Christopher Chidsey
Associate Professor of Chemistry, Emeritus
Bio
Professor Chidsey’s research interests lie in electrochemistry and electrocatalysis, and in building the chemical base for molecular electronics. He has investigated the role of chemical bonding in promoting long-distance electron tunneling across interfaces and contributed to the development of silicon and germanium surface chemistry, including the self-assembly of complex molecular monolayers on silicon. Today his lab develops molecular systems, analytical tools and theoretical approaches to understand electron transfer between electrodes and among redox species, with applications in sustainable battery technology, fuel chemistry, and biochemical analysis.
Born in 1957, Christopher Chidsey studied chemistry at Dartmouth College (A.B. 1978) and physical chemistry at Stanford University (Ph.D. 1983). After postdoctoral work in electrochemistry with Royce Murray at the University of North Carolina, he joined the technical staff at AT&T Bell Laboratories, where he probed long-distance electron transfer across interfaces and contributed to developments in scanning tunneling microscopy, nonlinear optical materials and optical materials processing. He joined the Stanford Department of Chemistry as Associate Professor in 1992, and in 2009 was also appointed Senior Fellow at the Precourt Institute for Energy. He has received the Dreyfus Teacher-Scholar Award and Bing and Hertz Foundation fellowships, and was elected a fellow of the American Association for the Advancement of Science.
The Chidsey Lab at Stanford uses surface chemistry and electrochemistry to control and investigate a number of important interfacial phenomena.
Water Oxidation
The group has shown that a 2 nm film of TiO2, created by atomic layer deposition, protects otherwise unstable semiconductor surfaces to achieve efficient and stable photoelectrolysis of water to produce hydrogen and oxygen fuels. Current work involves tailoring alloyed RuO2/TiO2 catalyst layers to optimize the turnover frequency for oxygen evolution, with the aim of achieving comparable electrocatalytic activity at a fraction of prior noble metal usage.
Electrocatalysis for Fuel Cells and CO2 Reduction
A major effort involves covalent attachment of electrocatalysts to carbon electrodes and other oxidation-resistant conductive substrates for use in ambient-temperature fuel cells and related energy- and chemical-conversion systems. A new covalent chemistry on graphitic carbon surfaces, based on the ‘click’ reaction of azides and alkynes, has been developed. Another effort involves the formation of electroactive self-assembled thiol monolayers on gold surfaces – an area Professor Chidsey pioneered beginning 15 years ago.
Another project employs transfer hydrogenation catalyts as alcohol oxidation electocatalysts for fuel cells. Lab members study the thermodynamics and kinetics of metal hydride formation from a metal precatalyst and an alcohol fuel, and examine the electro-oxidation of the formed metal hydrides. Running this cycle in the microscopic reverse direction leads to a strategy for CO2 reduction. The aim is to extend this knowledge from working examples to catalyst design for such transformations.
Battery Technology
Many of the electrolyte components used in lithium-ion batteries are not electrochemically stable at the low potentials reached by the anode when the battery charges. However, with the right electrolyte mixture, the decomposition products on the first charge create a solid electrolyte interphase that acts as a lithium-ion conductive, but otherwise passivating layer, slowing electrolyte degradation. Chidsey group members study the formation and useful contributions of this layer.
Academic Appointments
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Emeritus Faculty, Acad Council, Chemistry
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Senior Fellow, Precourt Institute for Energy
Administrative Appointments
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Associate Professor by Courtesy, Department of Chemical Engineering Stanford University (2008 - 2011)
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Associate Professor, Department of Photon Science SLAC, Stanford University (1997 - 2010)
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Member of Technical Staff, AT&T Bell Laboratories (1984 - 1992)
Honors & Awards
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Fellow, National Science Foundation (1978-1981)
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Fellow, Fanny and John Hertz Foundation (1982-1983)
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Teacher-Scholar, Camille and Henry Dreyfus (1993)
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Bing Fellow, Stanford University (1995)
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Fellow, AAAS (2007)
Professional Education
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Postdoctoral Fellow, University of North Carolina, Electrochemistsry (1983)
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Ph.D., Stanford University, Physical Chemistry (1983)
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A.B., Dartmouth College, Chemistry (1978)
Current Research and Scholarly Interests
The Chidsey group research interest is to build the chemical base for molecular electronics. To accomplish this, we synthesize the molecular and nanoscopic systems, build the analytical tools and develop the theoretical understanding with which to study electron transfer between electrodes and among redox species through insulating molecular bridges. Members of the group have synthesized several series of saturated and conjugated oligomers with which we have studied the fundamental aspects of electron tunneling through well-defined molecular bridges. The oligophenylenevinylene bridge of these molecules promotes rapid tunneling over remarkably long distances compared with other unsaturated and saturated bridges we have studied. For instance, starting in the activated complex, the tunneling rate between a gold electrode and an appended ferrocene through 3.5nm of an oligophenylenevinylene (OPV) bridge is 8 x 109 s-1 whereas the tunneling rate through an alkane bridge of the same length is expected to be slower than 1s-1.
To date our electron-tunneling studies have largely focused on what we casually denote as a "one-electrode" measurement with the molecular bridge connecting one electrode to a redox species which acts as a molecular capacitor to an ionically conducting solution. The other electrodes necessary to measure the tunneling conduction are remotely located in an electrochemical cell. We are currently embarked on a broad based effort to make conduction measurements with two electrodes, one on each end of a single molecule. We are also developing strategies to include one or more additional electrodes so that molecular circuits with electrical power gain can be assembled. This effort is leading us to develop nanostructured wiring schemes and self-assembly methods for the construction of whole circuits of wired molecules. We will be examining nanowires formed from doped silicon and other substances. This emerging effort in nanowiring will be greatly aided by the previous work in the Chidsey lab on the surface chemistry of silicon, particularly the self-assembly of complex molecular monolayers on silicon surfaces.
2024-25 Courses
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Independent Studies (8)
- Advanced Undergraduate Research
CHEM 190 (Aut, Win, Spr, Sum) - Directed Instruction/Reading
CHEM 90 (Aut, Win, Spr, Sum) - Graduate Independent Study
MATSCI 399 (Aut, Win, Spr, Sum) - Master's Research
MATSCI 200 (Aut, Win, Spr, Sum) - Ph.D. Research
MATSCI 300 (Aut, Win, Spr, Sum) - Practical Training
MATSCI 299 (Aut, Win, Spr, Sum) - Research and Special Advanced Work
CHEM 200 (Aut, Win, Spr, Sum) - Research in Chemistry
CHEM 301 (Aut, Win, Spr, Sum)
- Advanced Undergraduate Research
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Prior Year Courses
2021-22 Courses
- Physical chemistry laboratory I
CHEM 174, CHEM 274 (Aut)
- Physical chemistry laboratory I
All Publications
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Bromomethylation of high-surface area carbons as a versatile synthon: adjusting the electrode-electrolyte interface in lithium-sulfur batteries
JOURNAL OF MATERIALS CHEMISTRY A
2019; 7 (34): 20013–25
View details for DOI 10.1039/c9ta04360h
View details for Web of Science ID 000483565400041
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Mapping free energy regimes in electrocatalytic reductions to screen transition metal-based catalysts
CHEMICAL SCIENCE
2019; 10 (32): 7649–58
View details for DOI 10.1039/c9sc01766f
View details for Web of Science ID 000481422800017
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Mapping free energy regimes in electrocatalytic reductions to screen transition metal-based catalysts.
Chemical science
2019; 10 (32): 7649-7658
Abstract
The free energy landscape of catalytic intermediates in the two-electron reduction of proton donors and/or CO2 to H2, CO and HCO2- is mapped with density functional theory to screen catalyst candidates from a library of different transition metals and ligands. The goal is to minimize the free energy corrugations between reactants, catalytic intermediates and each desired product, simultaneously screening against intermediates with low free energy that would be traps, and against necessary intermediates with high free energy. Catalysts are initially screened for those with: (a) standard state free energy of the metal hydride intermediate ergoneutral with HCO2-, which is the lowest energy product with weak proton donors, and (b) standard free energy of the metal carbonyl intermediate sufficiently high to avoid trapping. The design method is tested on a diverse range of ligands including cyclopentadienyl, polypyridyl, amino, phosphino and carbonyl ligands, around three earth-abundant d6 transition metal ions, Mn(i), Fe(ii) and Co(iii), using the BP86 density functional, the double-zeta 6-31+G* basis, LANL2DZ effective core potential on the metals and SMD polarizable continuum model for acetonitrile as solvent, which have previously provided chemically accurate values of several redox potentials, pKa's and ligand exchange equilibria for transition metal complexes. Among the 36 complexes screened, an Fe(ii) center ligated to two bipyridines and a pyridine with a solvent-bound sixth coordination site for hydride formation from phenol as the proton donor is identified as a promising candidate for ergoneutral hydride formation without trapping by CO. The redox-active bipyridine ligands are predicted to provide near ergoneutral sites for accumulating the two electrons needed to form the hydride. To test the predictions, an Fe(ii) complex was prepared with the desired ligand environment using a pentadentate ligand to prevent ligand exchange. The synthesized complex was indeed found to be active towards electrocatalytic proton reduction as well as CO2 reduction at the predicted redox potentials with no trapping by CO. However, contrary to the in silico predictions, we found electrochemical evidence of CO2 binding after the first reduction leading to CO production. Mapping the free energies of key catalytic intermediates such as the metal hydride and metal carbonyl species by using density functional theory (DFT) serves as a first step in catalyst screening spanning large libraries of metals and ligands. In order to screen against all the intermediates in the catalytic pathway, such as reduced metal-bound CO2 intermediates, further refinement and validation of the DFT methods are needed.
View details for DOI 10.1039/c9sc01766f
View details for PubMedID 31588316
View details for PubMedCentralID PMC6761863
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Atomic Layer Deposited TiO2-IrOx Alloys Enable Corrosion Resistant Water Oxidation on Silicon at High Photovoltage
CHEMISTRY OF MATERIALS
2019; 31 (1): 90–100
View details for DOI 10.1021/acs.chemmater.8b03092
View details for Web of Science ID 000455558100011
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Atomic Layer Deposited TiO2-IrOx Alloy as a Hole Transport Material for Perovskite Solar Cells
ADVANCED MATERIALS INTERFACES
2018; 5 (16)
View details for DOI 10.1002/admi.201800191
View details for Web of Science ID 000442489600007
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Electrocatalytic alcohol oxidation with molecular catalysts
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435539902252
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Initiation of the Electrochemical Reduction of CO2 by a Singly Reduced Ruthenium(II) Bipyridine Complex.
Inorganic chemistry
2017; 56 (14): 8326-8333
Abstract
The one-electron reduction of [CpRu(bpy)NCCH3]PF6 (Cp = cyclopentadienyl; bpy = 2,2'-bipyridine), abbreviated as [Ru-S]+, where S = CH3CN, in CO2-saturated acetonitrile initiates a cascade of rapid electrochemical and chemical steps (ECEC) at an electrode potential of ca. 100 mV positive of the first reduction of the ruthenium complex. The overall two-electron process leads to the generation of a CO-bound ruthenium complex, [Ru-CO]+, and carbonate, as independently confirmed by NMR spectroscopy. Simulations of the cyclic voltammograms using DigiElch together with density functional theory based calculations reveal that the singly reduced ruthenium complex [Ru-S]0 binds CO2 at a rate of ca. 105 M-1 s-1 at almost zero driving force. Subsequent to CO2 binding, all of the steps leading up to deoxygenation are highly exergonic and rapid. A model of the potential energy profile of the CO2 approach to the Ru center in the singly reduced manifold reveals a direct correlation between the reactivity toward CO2 and the nucleophilicity at the metal center influenced by different ligand environments. Through the binding of CO2 after the first reduction, overpotentials associated with consecutive electrochemical reductions are avoided. This work therefore provides an important design principle for engineering transition-metal complexes to activate CO2 under low driving forces.
View details for DOI 10.1021/acs.inorgchem.7b01004
View details for PubMedID 28640601
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Multielectron Transfer at Cobalt: Influence of the Phenylazopyridine Ligand
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2017; 139 (12): 4540-4550
Abstract
The dicationic complex [CpCo(azpy)(CH3CN)](ClO4)2 1 (azpy = phenylazopyridine) exhibits a reversible two-electron reduction at a very mild potential (-0.16 V versus Fc(0/+)) in acetonitrile. This behavior is not observed with the analogous bipyridine and pyrazolylpyridine complexes (3 and 4), which display an electrochemical signature typical of Co(III) systems: two sequential one-electron reductions to Co(II) at -0.4 V and Co(I) at -1.0 to -1.3 V versus Fc(0/+). The doubly reduced, neutral complex [CpCo(azpy)] 2 is isolated as an air-stable, diamagnetic solid via chemical reduction with cobaltocene. Crystallographic and spectroscopic characterization together with experimentally calibrated density functional theory calculations illuminate the key structural and electronic changes that occur upon reduction of 1 to 2. The electrochemical potential inversion observed with 1 is attributed to effective overlap between the metal d and the low-energy azo π* orbitals in the intermediary redox state and additional stabilization of 2 from structural reorganization, leading to a two-electron reduction. This result serves as a key milestone in the quest for two-electron transformations with mononuclear first-row transition metal complexes at mild potentials.
View details for DOI 10.1021/jacs.7b01047
View details for Web of Science ID 000398247100051
View details for PubMedID 28263588
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Electrocatalytic Alcohol Oxidation with Ruthenium Transfer Hydrogenation Catalysts
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2017; 139 (2): 738-748
Abstract
Octahedral ruthenium complexes [RuX(CNN)(dppb)] (1, X = Cl; 2, X = H; CNN = 2-aminomethyl-6-tolylpyridine, dppb = 1,4-bis(diphenylphosphino)butane) are highly active for the transfer hydrogenation of ketones with isopropanol under ambient conditions. Turnover frequencies of 0.88 and 0.89 s(-1) are achieved at 25 °C using 0.1 mol % of 1 or 2, respectively, in the presence of 20 equiv of potassium t-butoxide relative to catalyst. Electrochemical studies reveal that the Ru-hydride 2 is oxidized at low potential (-0.80 V versus ferrocene/ferrocenium, Fc(0/+)) via a chemically irreversible process with concomitant formation of dihydrogen. Complexes 1 and 2 are active for the electrooxidation of isopropanol in the presence of strong base (potassium t-butoxide) with an onset potential near -1 V versus Fc(0/+). By cyclic voltammetry, fast turnover frequencies of 3.2 and 4.8 s(-1) for isopropanol oxidation are achieved with 1 and 2, respectively. Controlled potential electrolysis studies confirm that the product of isopropanol electrooxidation is acetone, generated with a Faradaic efficiency of 94 ± 5%.
View details for DOI 10.1021/jacs.6b09705
View details for Web of Science ID 000392459300032
View details for PubMedID 27997178
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Initiation of the Electrochemical Reduction of CO2 by a Singly Reduced Ruthenium(II) Bipyridine Complex
Inorganic Chemistry
2017: 8326–33
Abstract
The one-electron reduction of [CpRu(bpy)NCCH3]PF6 (Cp = cyclopentadienyl; bpy = 2,2'-bipyridine), abbreviated as [Ru-S]+, where S = CH3CN, in CO2-saturated acetonitrile initiates a cascade of rapid electrochemical and chemical steps (ECEC) at an electrode potential of ca. 100 mV positive of the first reduction of the ruthenium complex. The overall two-electron process leads to the generation of a CO-bound ruthenium complex, [Ru-CO]+, and carbonate, as independently confirmed by NMR spectroscopy. Simulations of the cyclic voltammograms using DigiElch together with density functional theory based calculations reveal that the singly reduced ruthenium complex [Ru-S]0 binds CO2 at a rate of ca. 105 M-1 s-1 at almost zero driving force. Subsequent to CO2 binding, all of the steps leading up to deoxygenation are highly exergonic and rapid. A model of the potential energy profile of the CO2 approach to the Ru center in the singly reduced manifold reveals a direct correlation between the reactivity toward CO2 and the nucleophilicity at the metal center influenced by different ligand environments. Through the binding of CO2 after the first reduction, overpotentials associated with consecutive electrochemical reductions are avoided. This work therefore provides an important design principle for engineering transition-metal complexes to activate CO2 under low driving forces.
View details for DOI 10.1021/acs.inorgchem.7b01004
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Isolating the Photovoltaic Junction: Atomic Layer Deposited TiO2-RuO2 Alloy Schottky Contacts for Silicon Photoanodes
ACS APPLIED MATERIALS & INTERFACES
2016; 8 (36): 23763-23773
Abstract
We synthesized nanoscale TiO2-RuO2 alloys by atomic layer deposition (ALD) that possess a high work function and are highly conductive. As such, they function as good Schottky contacts to extract photogenerated holes from n-type silicon while simultaneously interfacing with water oxidation catalysts. The ratio of TiO2 to RuO2 can be precisely controlled by the number of ALD cycles for each precursor. Increasing the composition above 16% Ru sets the electronic conductivity and the metal work function. No significant Ohmic loss for hole transport is measured as film thickness increases from 3 to 45 nm for alloy compositions ≥ 16% Ru. Silicon photoanodes with a 2 nm SiO2 layer that are coated by these alloy Schottky contacts having compositions in the range of 13-46% Ru exhibit average photovoltages of 525 mV, with a maximum photovoltage of 570 mV achieved. Depositing TiO2-RuO2 alloys on nSi sets a high effective work function for the Schottky junction with the semiconductor substrate, thus generating a large photovoltage that is isolated from the properties of an overlying oxygen evolution catalyst or protection layer.
View details for DOI 10.1021/acsami.6b08558
View details for Web of Science ID 000383412000036
View details for PubMedID 27548719
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Titanium Oxide Crystallization and Interface Defect Passivation for High Performance Insulator-Protected Schottky Junction MIS Photoanodes
ACS APPLIED MATERIALS & INTERFACES
2016; 8 (23): 14596-14603
Abstract
Atomic layer deposited (ALD) TiO2 protection layers may allow for the development of both highly efficient and stable photoanodes for solar fuel synthesis; however, the very different conductivities and photovoltages reported for TiO2-protected silicon anodes prepared using similar ALD conditions indicate that mechanisms that set these key properties are, as yet, poorly understood. In this report, we study hydrogen-containing annealing treatments and find that postcatalyst-deposition anneals at intermediate temperatures reproducibly yield decreased oxide/silicon interface trap densities and high photovoltage. A previously reported insulator thickness-dependent photovoltage loss in metal-insulator-semiconductor Schottky junction photoanodes is suppressed. This occurs simultaneously with TiO2 crystallization and an increase in its dielectric constant. At small insulator thickness, a record for a Schottky junction photoanode of 623 mV photovoltage is achieved, yielding a photocurrent turn-on at 0.92 V vs NHE or -0.303 V with respect to the thermodynamic potential for water oxidation.
View details for DOI 10.1021/acsami.6b03688
View details for Web of Science ID 000378195000038
View details for PubMedID 27196628
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Engineering Interfacial Silicon Dioxide for Improved Metal-Insulator-Semiconductor Silicon Photoanode Water Splitting Performance
ACS APPLIED MATERIALS & INTERFACES
2016; 8 (20): 13140-13149
Abstract
Silicon photoanodes protected by atomic layer deposited (ALD) TiO2 show promise as components of water splitting devices that may enable the large-scale production of solar fuels and chemicals. Minimizing the resistance of the oxide corrosion protection layer is essential for fabricating efficient devices with good fill factor. Recent literature reports have shown that the interfacial SiO2 layer, interposed between the protective ALD-TiO2 and the Si anode, acts as a tunnel oxide that limits hole conduction from the photoabsorbing substrate to the surface oxygen evolution catalyst. Herein, we report a significant reduction of bilayer resistance, achieved by forming stable, ultrathin (<1.3 nm) SiO2 layers, allowing fabrication of water splitting photoanodes with hole conductances near the maximum achievable with the given catalyst and Si substrate. Three methods for controlling the SiO2 interlayer thickness on the Si(100) surface for ALD-TiO2 protected anodes were employed: (1) TiO2 deposition directly on an HF-etched Si(100) surface, (2) TiO2 deposition after SiO2 atomic layer deposition on an HF-etched Si(100) surface, and (3) oxygen scavenging, post-TiO2 deposition to decompose the SiO2 layer using a Ti overlayer. Each of these methods provides a progressively superior means of reliably thinning the interfacial SiO2 layer, enabling the fabrication of efficient and stable water oxidation silicon anodes.
View details for DOI 10.1021/acsami.6b03029
View details for Web of Science ID 000376825800069
View details for PubMedID 27096845
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Experimental and Theoretical Study of CO2 Insertion into Ruthenium Hydride Complexes.
Inorganic chemistry
2016; 55 (4): 1623-1632
Abstract
The ruthenium hydride [RuH(CNN)(dppb)] (1; CNN = 2-aminomethyl-6-tolylpyridine, dppb = 1,4-bis(diphenylphosphino)butane) reacts rapidly and irreversibly with CO2 under ambient conditions to yield the corresponding Ru formate complex 2. In contrast, the Ru hydride 1 reacts with acetone reversibly to generate the Ru isopropoxide, with the reaction free energy ΔG°298 K = -3.1 kcal/mol measured by (1)H NMR in tetrahydrofuran-d8. Density functional theory (DFT), calibrated to the experimentally measured free energies of ketone insertion, was used to evaluate and compare the mechanism and energetics of insertion of acetone and CO2 into the Ru-hydride bond of 1. The calculated reaction coordinate for acetone insertion involves a stepwise outer-sphere dihydrogen transfer to acetone via hydride transfer from the metal and proton transfer from the N-H group on the CNN ligand. In contrast, the lowest energy pathway calculated for CO2 insertion proceeds by an initial Ru-H hydride transfer to CO2 followed by rotation of the resulting N-H-stabilized formate to a Ru-O-bound formate. DFT calculations were used to evaluate the influence of the ancillary ligands on the thermodynamics of CO2 insertion, revealing that increasing the π acidity of the ligand cis to the hydride ligand and increasing the σ basicity of the ligand trans to it decreases the free energy of CO2 insertion, providing a strategy for the design of metal hydride systems capable of reversible, ergoneutral interconversion of CO2 and formate.
View details for DOI 10.1021/acs.inorgchem.5b02556
View details for PubMedID 26835983
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Conductance and capacitance of bilayer protective oxides for silicon water splitting anodes
ENERGY & ENVIRONMENTAL SCIENCE
2016; 9 (2): 504-516
View details for DOI 10.1039/c5ee02484f
View details for Web of Science ID 000369744500017
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Rapid oxidative hydrogen evolution from a family of square-planar nickel hydride complexes.
Chemical science
2016; 7 (1): 117-127
Abstract
A series of square-planar nickel hydride complexes supported by bis(phosphinite) pincer ligands with varying substituents (-OMe, -Me, and -Bu t ) on the pincer backbone have been synthesized and completely characterized by NMR spectroscopy, IR spectroscopy, elemental analysis, and X-ray crystallography. Their cyclic voltammograms show irreversible oxidation peaks (peak potentials from 101 to 316 mV vs. Fc+/Fc) with peak currents consistent with overall one-electron oxidations. Chemical oxidation by the one-electron oxidant Ce(NBu4)2(NO3)6 was studied by NMR spectroscopy, which provided quantitative evidence for post-oxidative H2 evolution leading to a solvent-coordinated nickel(ii) species with the pincer backbone intact. Bulk electrolysis of the unsubstituted nickel hydride (3a) showed an overall one-electron stoichiometry and gas chromatographic analysis of the headspace gas after electrolysis further confirmed stoichiometric production of dihydrogen. Due to the extremely high rate of the post-oxidative chemical process, electrochemical simulations have been used to establish a lower limit of the bimolecular rate constant (kf > 107 M-1 s-1) for the H2 evolution step. To the best of our knowledge, this is the fastest known oxidative H2 evolution process observed in transition metal hydrides. Quantum chemical calculations based on DFT indicate that the one-electron oxidation of the nickel hydride complex provides a strong chemical driving force (-90.3 kcal mol-1) for the production of H2 at highly oxidizing potentials.
View details for DOI 10.1039/c5sc03189c
View details for PubMedID 29861972
View details for PubMedCentralID PMC5950828
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Rapid oxidative hydrogen evolution from a family of square-planar nickel hydride complexes
CHEMICAL SCIENCE
2016; 7 (1): 117-127
Abstract
A series of square-planar nickel hydride complexes supported by bis(phosphinite) pincer ligands with varying substituents (-OMe, -Me, and -Bu t ) on the pincer backbone have been synthesized and completely characterized by NMR spectroscopy, IR spectroscopy, elemental analysis, and X-ray crystallography. Their cyclic voltammograms show irreversible oxidation peaks (peak potentials from 101 to 316 mV vs. Fc+/Fc) with peak currents consistent with overall one-electron oxidations. Chemical oxidation by the one-electron oxidant Ce(NBu4)2(NO3)6 was studied by NMR spectroscopy, which provided quantitative evidence for post-oxidative H2 evolution leading to a solvent-coordinated nickel(ii) species with the pincer backbone intact. Bulk electrolysis of the unsubstituted nickel hydride (3a) showed an overall one-electron stoichiometry and gas chromatographic analysis of the headspace gas after electrolysis further confirmed stoichiometric production of dihydrogen. Due to the extremely high rate of the post-oxidative chemical process, electrochemical simulations have been used to establish a lower limit of the bimolecular rate constant (kf > 107 M-1 s-1) for the H2 evolution step. To the best of our knowledge, this is the fastest known oxidative H2 evolution process observed in transition metal hydrides. Quantum chemical calculations based on DFT indicate that the one-electron oxidation of the nickel hydride complex provides a strong chemical driving force (-90.3 kcal mol-1) for the production of H2 at highly oxidizing potentials.
View details for DOI 10.1039/c5sc03189c
View details for Web of Science ID 000366826900011
View details for PubMedCentralID PMC5950828
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Design principles for maximizing photovoltage in metal-oxide-protected water-splitting photoanodes
NATURE MATERIALS
2016; 15 (1): 99-?
Abstract
Metal oxide protection layers for photoanodes may enable the development of large-scale solar fuel and solar chemical synthesis, but the poor photovoltages often reported so far will severely limit their performance. Here we report a novel observation of photovoltage loss associated with a charge extraction barrier imposed by the protection layer, and, by eliminating it, achieve photovoltages as high as 630 mV, the maximum reported so far for water-splitting silicon photoanodes. The loss mechanism is systematically probed in metal-insulator-semiconductor Schottky junction cells compared to buried junction p(+)n cells, revealing the need to maintain a characteristic hole density at the semiconductor/insulator interface. A leaky-capacitor model related to the dielectric properties of the protective oxide explains this loss, achieving excellent agreement with the data. From these findings, we formulate design principles for simultaneous optimization of built-in field, interface quality, and hole extraction to maximize the photovoltage of oxide-protected water-splitting anodes.
View details for DOI 10.1038/NMAT4451
View details for Web of Science ID 000366690600028
View details for PubMedID 26480231
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Understanding Photovoltage in Insulator-Protected Water Oxidation Half-Cells
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2016; 163 (3): H192-H200
View details for DOI 10.1149/2.0601603jes
View details for Web of Science ID 000370861500120
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The Effect of SPA-SiO2 Tunnel Oxide Thickness for Metal-Insulator-Silicon Photoelectrochemical Cells
ELECTROCHEMICAL SOC INC. 2014: 265–76
View details for DOI 10.1149/06409.0265ecst
View details for Web of Science ID 000356676800024
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Electrooxidation of alcohols catalyzed by amino alcohol ligated ruthenium complexes.
Journal of the American Chemical Society
2013; 135 (38): 14299-14305
Abstract
Ruthenium transfer hydrogenation catalysts physisorbed onto edge-plane graphite electrodes are active electrocatalysts for the oxidation of alcohols. Electrooxidation of CH3OH (1.23 M) in a buffered aqueous solution at pH 11.5 with [(η(6)-p-cymene)(η(2)-N,O-(1R,2S)-cis-1-amino-2-indanol)]Ru(II)Cl (2) on edge-plane graphite exhibits an onset current at 560 mV vs NHE. Koutecky-Levich analysis at 750 mV reveals a four-electron oxidation of methanol with a rate of 1.35 M(-1) s(-1). Mechanistic investigations by (1)H NMR, cyclic voltammetry, and desorption electrospray ionization mass spectrometry indicate that the electroxidation of methanol to generate formate is mediated by surface-supported Ru-oxo complexes.
View details for DOI 10.1021/ja4055564
View details for PubMedID 24044700
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Effects of catalyst material and atomic layer deposited TiO2 oxide thickness on the water oxidation performance of metal-insulator-silicon anodes
ENERGY & ENVIRONMENTAL SCIENCE
2013; 6 (8): 2487-2496
View details for DOI 10.1039/c3ee41178h
View details for Web of Science ID 000321983800022
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Squish and CuAAC: Additive-Free Covalent Mono layers of Discrete Molecules in Seconds
LANGMUIR
2013; 29 (18): 5383-5387
Abstract
A terminal alkyne is immobilized rapidly into a full monolayer by squishing a small volume of a solution of the alkyne between an azide-modified surface and a copper plate. The monolayer is covalently attached to the surface through a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction, and the coverages of the immobilized electroactive alkyne species are quantified by cyclic voltammetry. A reaction time of less than 20 s is possible with no other reagents required. The procedure is effective under aerobic conditions using either an aqueous or aprotic organic solution of the alkyne (1-100 mM).
View details for DOI 10.1021/la400172w
View details for Web of Science ID 000318756200001
View details for PubMedID 23551032
View details for PubMedCentralID PMC3683963
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Gas-Phase Azide Functionalization of Carbon
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2013; 135 (3): 1110-1116
Abstract
Tailoring the surface and interfacial properties of inexpensive and abundant carbon materials plays an increasingly important role for innovative applications including those in electrocatalysis, energy storage, gas separations, and composite materials. Described here is the novel preparation and subsequent use of gaseous iodine azide for the azide modification of carbon surfaces. In-line generation of gaseous iodine azide from iodine monochloride vapor and solid sodium azide is safe and convenient. Immediate treatment of carbon surfaces with this gaseous stream of iodine azide provides a highly reproducible, selective, and scalable azide functionalization that minimizes waste and reduces deleterious side reactions. Among the possible uses of azide-modified surfaces, they serve as versatile substrates for the attachment of additional functionality by coupling with terminal alkynes under the mild copper-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reaction. For instance, coupling ethynylferrocene to azide-modified glassy carbon surfaces achieves ferrocene coverage up to 8 × 10(13) molecules/cm(2) by voltammetric and XPS analyses. The 1,2,3-triazole linker formed during the CuAAC reaction is robust and hydrolytically stable in both aqueous 1 M HClO(4) and 1 M NaOH for at least 12 h at 100 °C.
View details for DOI 10.1021/ja310410d
View details for Web of Science ID 000314141200027
View details for PubMedID 23301920
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ALD-TiO2 Preparation and Characterization for Metal-Insulator-Silicon Photoelectrochemical Applications
9th International Symposium on Atomic Layer Deposition Applications held during the 224th Meeting of the Electrochemical-Society (ECS)
ELECTROCHEMICAL SOC INC. 2013: 75–86
View details for DOI 10.1149/05810.0075ecst
View details for Web of Science ID 000329647500008
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Molecular Junctions of Self-Assembled Monolayers with Conducting Polymer Contacts
ACS NANO
2012; 6 (11): 9920-9931
Abstract
We present a method to fabricate individually addressable junctions of self-assembled monolayers (SAMs) that builds on previous studies which have shown that soft conductive polymer top contacts virtually eliminate shorts through the SAMs. We demonstrate devices with nanoscale lateral dimensions, representing an order of magnitude reduction in device area, with high yield and relatively low device-to-device variation, improving several features of previous soft contact devices. The devices are formed in pores in an inorganic dielectric layer with features defined by e-beam lithography and dry etching. We replace the aqueous PEDOT:PSS conductive polymer used in prior devices with Aedotron P, a low-viscosity, amphiphilic polymer, allowing incorporation of self-assembled monolayers with either hydrophobic or hydrophilic termination with the same junction geometry and materials. We demonstrate the adaptability of this new design by presenting transport measurements on SAMs composed of alkanethiols with methyl, thiol, carboxyl, and azide terminations. We establish that the observed room-temperature tunnel barrier is primarily a function of monolayer thickness, independent of the terminal group's hydrophilicity. Finally, we investigate the temperature dependence of transport and show that the low-temperature behavior is based on the energy distribution of sites from which carriers can tunnel between the polymer and gold contacts, as described by a model of variable-range hopping transport in a disordered conductor.
View details for DOI 10.1021/nn3035183
View details for Web of Science ID 000311521700061
View details for PubMedID 23035989
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Deposition of Dense Siloxane Monolayers from Water and Trimethoxyorganosilane Vapor
LANGMUIR
2011; 27 (16): 9928-9935
Abstract
A convenient, laboratory-scale method for the vapor deposition of dense siloxane monolayers onto oxide substrates was demonstrated. This method was studied and optimized at 110 °C under reduced pressure with the vapor of tetradecyltris(deuteromethoxy)silane, (CD(3)O)(3)Si(CH(2))(13)CH(3), and water from the dehydration of MgSO(4)·7H(2)O. Ellipsometric thicknesses, water contact angles, Fourier transform infrared (FTIR) spectroscopy, and electrochemical capacitance measurements were used to probe monolayer densification. The CD(3) stretching mode in the FTIR spectrum was monitored as a function of the deposition time and amounts of silane and water reactants. This method probed the unhydrolyzed methoxy groups on adsorbed silanes. Excess silane and water were necessary to achieve dense, completely hydrolyzed monolayers. In the presence of sufficient silane, an excess of water above the calculated stoichiometric amount was necessary to hydrolyze all methoxy groups and achieve dense monolayers. The excess water was partially attributed to the reversibility of the hydrolysis of the methoxy groups.
View details for DOI 10.1021/la201333y
View details for Web of Science ID 000293662800036
View details for PubMedID 21721567
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Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation
NATURE MATERIALS
2011; 10 (7): 539-544
Abstract
A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient photovoltaic material, is protected by atomic layer deposition (ALD) of a highly uniform, 2 nm thick layer of titanium dioxide (TiO(2)) and then coated with an optically transmitting layer of a known catalyst (3 nm iridium). Photoelectrochemical water oxidation was observed to occur below the reversible potential whereas dark electrochemical water oxidation was found to have low-to-moderate overpotentials at all pH values, resulting in an inferred photovoltage of ~550 mV. Water oxidation is sustained at these anodes for many hours in harsh pH and oxidative environments whereas comparable silicon anodes without the TiO(2) coating quickly fail. The desirable electrochemical efficiency and corrosion resistance of these anodes is made possible by the low electron-tunnelling resistance (<0.006 Ω cm(2) for p(+)-Si) and uniform thickness of atomic-layer deposited TiO(2).
View details for DOI 10.1038/NMAT3047
View details for Web of Science ID 000291969500020
View details for PubMedID 21685904
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Electrocatalytic O-2 Reduction by Covalently Immobilized Mononuclear Copper(I) Complexes: Evidence for a Binuclear Cu2O2 Intermediate
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2011; 133 (11): 3696-3699
Abstract
A Cu(I) complex of 3-ethynyl-phenanthroline covalently immobilized onto an azide-modified glassy carbon surface is an active electrocatalyst for the four-electron (4-e) reduction of O(2) to H(2)O. The rate of O(2) reduction is second-order in Cu coverage at moderate overpotential, suggesting that two Cu(I) species are necessary for efficient 4-e reduction of O(2). Mechanisms for O(2) reduction are proposed that are consistent with the observations for this covalently immobilized system and previously reported results for a similar physisorbed Cu(I) system.
View details for DOI 10.1021/ja106338h
View details for Web of Science ID 000288889900004
View details for PubMedID 21366244
View details for PubMedCentralID PMC3077299
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Redox Catalysis for Dehydrogenation of Liquid Hydrogen Carrier Fuels for Energy Storage and Conversion
ELECTROCHEMICAL SOC INC. 2011: 3–17
View details for DOI 10.1149/1.3641814
View details for Web of Science ID 000300873900001
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Group IV semiconductor nanowire arrays: epitaxy in different contexts
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
2010; 25 (2)
View details for DOI 10.1088/0268-1242/25/2/024016
View details for Web of Science ID 000273852300017
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Gold Removal from Germanium Nanowires
LANGMUIR
2009; 25 (16): 9473-9479
Abstract
We report the selective removal of gold from the tips of germanium nanowires (GeNWs) grown by chemical vapor deposition on gold nanoparticles (AuNPs). Selective removal was accomplished by aqueous hydrochloric acid solutions containing either potassium triiodide or iodine. Measurement of the residual number of gold atoms on the GeNW samples using inductively coupled plasma-mass spectrometry shows that 99% of the gold was removed. Photoemission spectroscopy shows that the germanium surfaces of these samples were not further oxidized after treatment with these liquid etchants. Auger electron spectroscopy shows that AuNPs that did not yield GeNWs contain germanium and also that the addition of gaseous HCl to GeH(4) during GeNW growth increased the selectivity of germanium deposition to the AuNPs.
View details for DOI 10.1021/la900725b
View details for Web of Science ID 000268719900088
View details for PubMedID 19419180
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Selective Anodic Desorption for Assembly of Different Thiol Monolayers on the Individual Electrodes of an Array
LANGMUIR
2009; 25 (11): 6517-6521
Abstract
The close proximity of two individually addressable electrodes in an interdigitated array provides a unique platform for electrochemical study of multicatalytic processes. Here, we report a "plug-and-play" approach to control the underlying self-assembled monolayer and the electroactive species on each individually addressable electrode of an interdigitated array. The method presented here uses selective anodic desorption of a monolayer from one of the individually addressable electrodes and rapid formation of a different self-assembled monolayer on the freshly cleaned electrode. We illustrate this strategy by introducing variations in the length of the linker to the electroactive species in the self-assembled monolayer, which determines the rate of electron transfer. In order to separate the assembly of the monolayer from the choice of the electroactive species, we use CuI-catalyzed triazole formation ("click" chemistry) to covalently attach an acetylene-terminated electroactive species to an azide-terminated thiol monolayer selectively on each electrode. The resulting variations in the electron-transfer rate to surface-attached ferrocene and in the rate of catalytic oxidation of ascorbate by the ferrocenium/ferrocene couple demonstrate an application of this approach.
View details for DOI 10.1021/la8043363
View details for Web of Science ID 000266604000071
View details for PubMedID 19379005
View details for PubMedCentralID PMC2704236
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Growth of germanium crystals from electrodeposited gold in local crucibles
APPLIED PHYSICS LETTERS
2009; 94 (4)
View details for DOI 10.1063/1.3074363
View details for Web of Science ID 000262971800124
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Oxide-encapsulated vertical germanium nanowire structures and their DC transport properties
NANOTECHNOLOGY
2008; 19 (48)
Abstract
We demonstrate the p-type doping of Ge nanowires (NWs) and p-n junction arrays in a scalable vertically aligned structure with all processing performed below 400 °C. These structures are advantageous for the large scale production of parallel arrays of devices for nanoelectronics and sensing applications. Efficient methods for the oxide encapsulation, chemical mechanical polishing and cleaning of vertical Ge NWs embedded in silicon dioxide are reported. Approaches for avoiding the selective oxidation and dissolution of Ge NWs in aqueous solutions during chemical mechanical polishing and cleaning of oxide-encapsulated Ge NWs are emphasized. NWs were doped through the epitaxial deposition of a B-doped shell and transport measurements indicate doping concentrations on the order of 10(19) cm(-3).
View details for DOI 10.1088/0957-4484/19/48/485705
View details for Web of Science ID 000260859400022
View details for PubMedID 21836312
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Kinetic and mechanistic studies of the electrocatalytic reduction of O-2 to H2O with mononuclear Cu complexes of substituted 1,10-phenanthrolines
JOURNAL OF PHYSICAL CHEMISTRY A
2007; 111 (49): 12641-12650
Abstract
Mononuclear Cu complexes with a 1,10-phenanthroline-based ligand adsorbed onto an edge-plane graphite electrode act as electrocatalysts for the 4-electron reduction of O2 to H2O. A mechanism is proposed for the electrocatalytic O2 reduction that accounts for the observed redox and kinetic dependences on coordinating anions and proton donors in the buffer. Systematic increases of ligand electron-withdrawing properties and/or the steric demands near the Cu center increase the E0 of the Cu catalysts but decrease the rate of O2 reduction. The kinetic rate of O2 reduction at E0, reported as kinetic current divided by catalyst redox charge, decreases as E0 increases: from 16 s(-1) measured at E0 in air-saturated solutions for adsorbed Cu(phen) to 0.4 s(-1) for Cu(2,9-Et2-phen). The maximum value of E for which catalytic activity can be attained is estimated to be +350 mV vs NHE. Near E0, the kinetic current deviates from that expected if O2 binding were the sole rate-limiting step. This indicates that one or more of the electrochemical reduction steps are rate limiting at potentials near E0.
View details for DOI 10.1021/jp076106z
View details for Web of Science ID 000251518000062
View details for PubMedID 18076134
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Metastability of Au-Ge liquid nanocatalysts: Ge vapor-liquid-solid nanowire growth far below the bulk eutectic temperature
ACS NANO
2007; 1 (5): 415-422
Abstract
The vapor-liquid-solid mechanism of nanowire (NW) growth requires the presence of a liquid at one end of the wire; however, Au-catalyzed Ge nanowire growth by chemical vapor deposition can occur at approximately 100 degrees C below the bulk Au-Ge eutectic. In this paper, we investigate deep sub-eutectic stability of liquid Au-Ge catalysts on Ge NWs quantitatively, both theoretically and experimentally. We construct a binary Au-Ge phase diagram that is valid at the nanoscale and show that equilibrium arguments, based on capillarity, are inconsistent with stabilization of Au-Ge liquid at deep sub-eutectic temperatures, similar to those used in Ge NW growth. Hot-stage electron microscopy and X-ray diffraction are used to test the predictions of nanoscale phase equilibria. In addition to Ge supersaturation of the Au-Ge liquid droplet, which has recently been invoked as an explanation for deep sub-eutectic Ge NW growth, we find evidence of a substantial kinetic barrier to Au solidification during cooling below the nanoscale Au-Ge eutectic temperature.
View details for DOI 10.1021/nn7001486
View details for Web of Science ID 000252022900011
View details for PubMedID 19206662
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Conditions for subeutectic growth of Ge nanowires by the vapor-liquid-solid mechanism
JOURNAL OF APPLIED PHYSICS
2007; 102 (9)
View details for DOI 10.1063/1.2803893
View details for Web of Science ID 000250983700084
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Vertically oriented germanium nanowires grown from gold colloids on silicon substrates and subsequent gold removal
NANO LETTERS
2007; 7 (6): 1637-1642
Abstract
A linker-free method to deposit citrate-stabilized Au colloids onto hydrogen-terminated Si by acidifying the Au colloid solution with HF or HCl is presented. This method prevents oxide formation and provides a model system for studying orientation control of nanowires by epitaxy. Conditions are reported that result in vertically oriented Ge nanowires of uniform diameter and length on Si(111). We then present a method to remove Au catalysts from the nanowires with aqueous triiodide and HCl.
View details for DOI 10.1021/nl070595x
View details for Web of Science ID 000247186800037
View details for PubMedID 17530912
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Azide-modified graphitic surfaces for covalent attachment of alkyne-terminated molecules by "click" chemistry
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2007; 129 (17): 5370-?
View details for DOI 10.1021/ja071291f
View details for Web of Science ID 000245946400036
View details for PubMedID 17425323
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A cytochrome c oxidase model catalyzes oxygen to water reduction under rate-limiting electron flux
SCIENCE
2007; 315 (5818): 1565-1568
Abstract
We studied the selectivity of a functional model of cytochrome c oxidase's active site that mimics the coordination environment and relative locations of Fe(a3), Cu(B), and Tyr(244). To control electron flux, we covalently attached this model and analogs lacking copper and phenol onto self-assembled monolayer-coated gold electrodes. When the electron transfer rate was made rate limiting, both copper and phenol were required to enhance selective reduction of oxygen to water. This finding supports the hypothesis that, during steady-state turnover, the primary role of these redox centers is to rapidly provide all the electrons needed to reduce oxygen by four electrons, thus preventing the release of toxic partially reduced oxygen species.
View details for DOI 10.1126/science.1135844
View details for Web of Science ID 000244934800049
View details for PubMedID 17363671
View details for PubMedCentralID PMC3064436
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An integrated phase change memory cell with Ge nanowire diode for cross-point memory
Symposium on VLSI Technology 2007
JAPAN SOCIETY APPLIED PHYSICS. 2007: 98–99
View details for Web of Science ID 000250539900038
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Rate of interfacial electron transfer through the 1,2,3-triazole linkage
JOURNAL OF PHYSICAL CHEMISTRY B
2006; 110 (32): 15955-15962
Abstract
The rate of electron transfer is measured to two ferrocene and one iron tetraphenylporphyrin redox species coupled through terminal acetylenes to azide-terminated thiol monolayers by the Cu(I)-catalyzed azide-alkyne cycloaddition (a Sharpless "click" reaction) to form the 1,2,3-triazole linkage. The high yield, chemoselectivity, convenience, and broad applicability of this triazole formation reaction make such a modular assembly strategy very attractive. Electron-transfer rate constants from greater than 60,000 to 1 s(-1) are obtained by varying the length and conjugation of the electron-transfer bridge and by varying the surrounding diluent thiols in the monolayer. Triazole and the triazole carbonyl linkages provide similar electronic coupling for electron transfer as esters. The ability to vary the rate of electron transfer to many different redox species over many orders of magnitude by using modular coupling chemistry provides a convenient way to study and control the delivery of electrons to multielectron redox catalysts and similar interfacial systems that require controlled delivery of electrons.
View details for DOI 10.1021/jp057416p
View details for Web of Science ID 000239656100049
View details for PubMedID 16898751
View details for PubMedCentralID PMC3434967
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Nature of germanium nanowire heteroepitaxy on silicon substrates
JOURNAL OF APPLIED PHYSICS
2006; 100 (2)
View details for DOI 10.1063/1.2219007
View details for Web of Science ID 000239423400124
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Mixed azide-terminated monolayers: A platform for modifying electrode surfaces
LANGMUIR
2006; 22 (6): 2457-2464
Abstract
We have prepared and characterized mixed self-assembled monolayers (SAM) on gold electrodes from azido alkane thiols and various omega-functionalized alkane thiols. In the presence of copper(I) catalysts, these azide-modified surfaces are shown to react rapidly and quantitatively with terminal acetylenes forming 1,2,3-triazoles, via "click" chemistry. The initial azide substituents can be identified and monitored using both grazing-angle infrared (IR) and X-ray photoelectron spectrosopies. Acetylenes possessing redox-active ferrocene substituents react with the azide-terminated mixed SAMs and electrochemical measurements of the ferrocene-modified SAM electrodes have been used to quantify the redox centers attached to these platforms. Time-resolved electrochemical measurements have enabled us to follow the formation of these ferrocene centers and thus to measure the rate of the surface "click" reaction. Under optimal conditions this well-behaved second-order reaction takes place with a rate constant of 1 x 10(3) M(-)(1) s(-)(1). Typical reaction times of several minutes were realized using micromolar concentrations of acetylene. These techniques have been used to construct well-characterized, covalently modified monolayers that can be employed as functional electrode surfaces.
View details for DOI 10.1021/la052947q
View details for Web of Science ID 000236009900015
View details for PubMedID 16519441
View details for PubMedCentralID PMC1513191
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Selective functionalization of independently addressed microelectrodes by electrochemical activation and deactivation of a coupling catalyst
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2006; 128 (6): 1794-1795
Abstract
We demonstrate selective functionalization of independently addressed microelectrodes by electrochemical activation and deactivation of a coupling catalyst. 1,2,3-Triazole formation between terminal acetylenes and organic azides is efficiently catalyzed by copper(I) complexes (a Sharpless "click" reaction), while the oxidized copper(II) complexes are inactive. By electrochemically activating or deactivating the catalyst by switching its redox state, we demonstrate control over triazole formation between surface-immobilized azides and ethynylferrocene. The reaction proceeds on the time scale of minutes using submicromolar concentration of reactants and catalyst, requires mild potentials for catalyst activation and deactivation, and works in aqueous and mixed aqueous-organic solvents. By appropriate biasing of each electrode, we selectively modify one of two chemically identical 10-mum-wide electrodes separated by 10 mum in an interdigitated array. The ability to switch on or off the reaction by electrical addressing together with the chemoselectivity of this reaction makes Cu(I)-catalyzed triazole formation an ideal method for the chemical modification of multielectrode arrays.
View details for DOI 10.1021/ja058380h
View details for Web of Science ID 000235452200010
View details for PubMedID 16464070
View details for PubMedCentralID PMC1473176
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Germanium nanowire epitaxy: Shape and orientation control
NANO LETTERS
2006; 6 (2): 318-323
Abstract
Epitaxial growth of nanowires along the 111 directions was obtained on Ge(111), Ge(110), Ge(001), and heteroepitaxial Ge on Si(001) substrates at temperatures of 350 degrees C or less by gold-nanoparticle-catalyzed chemical vapor deposition. On Ge(111), the growth was mostly vertical. In addition to 111 growth, 110 growth was observed on Ge(001) and Ge(110) substrates. Tapering was avoided by the use of the two-temperature growth procedure, reported earlier by Greytak et al.
View details for DOI 10.1021/nl052231f
View details for Web of Science ID 000235532700034
View details for PubMedID 16464057
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Photoemission studies of passivation of germanium nanowires
APPLIED PHYSICS LETTERS
2005; 87 (26)
View details for DOI 10.1063/1.2158027
View details for Web of Science ID 000234338700081
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Chemoselective covalent coupling of oligonucleotide probes to self-assembled monolayers
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2005; 127 (24): 8600-8601
Abstract
A chemoselective route to routinely and rapidly attach oligonucleotide probes to well-defined surfaces is presented. Cu(I) tris(benzyltriazolylmethyl)amine-catalyzed coupling of terminal acetylenes to azides on a self-assembled monolayer is used instead of traditional nucleophilic-electrophilic coupling reactions. The reaction proceeds well even in the presence of purposely introduced nucleophilic and electrophilic impurities. The density of oligonucleotide probes can be controlled by controlling the amount of azide functionality. Although most of our work was done on gold surfaces, this technique should be readily applicable to any surface on which an azide-containing monolayer can be assembled as we have preliminarily demonstrated by derivatizing azidotrimethoxysilane-modified glass slides with fluorescein-containing oligonucleotides.
View details for DOI 10.1021/ja0514621
View details for Web of Science ID 000229981200010
View details for PubMedID 15954758
View details for PubMedCentralID PMC3431914
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Role of O-3 and OH. radicals in ozonated aqueous solution for the photoresist removal of semiconductor fabrication
OZONE-SCIENCE & ENGINEERING
2005; 27 (2): 139-146
View details for DOI 10.1080/01919510590925257
View details for Web of Science ID 000228976100005
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Interfacial electron-transfer kinetics of ferrocene through oligophenyleneethynylene bridges attached to gold electrodes as constituents of self-assembled monolayers: Observation of a nonmonotonic distance dependence
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2004; 126 (44): 14620-14630
Abstract
The standard heterogeneous electron-transfer rate constants (k(n)0) between substrate gold electrodes and the ferrocene redox couple attached to the electrode surface by variable lengths of substituted or unsubstituted oligophenyleneethynylene (OPE) bridges as constituents of mixed self-assembled monolayers were measured as a function of temperature. The distance dependences of the unsubstituted OPE standard rate constants and of the preexponential factors (An) obtained from an Arrhenius analysis of the unsubstituted OPE k(n)0 versus temperature data are not monotonic. This surprising result, together with the distance dependence of the substituted OPE preexponential factors, may be assessed in terms of the likely conformational variability of the OPE bridges (as a result of the low intrinsic barrier to rotation of the phenylene rings in these bridges) and the associated sensitivity of the rate of electron transfer (and, hence, the single-molecule conductance which may be estimated using An) through these bridges to the conformation of the bridge. Additionally, the measured standard rate constants were independent of the identity of the diluent component of the mixed monolayer, and using an unsaturated OPE diluent has no effect on the rate of electron transfer through a long-chain alkanethiol bridge. These observations indicate that the diluent does not participate in the electron-transfer event.
View details for DOI 10.1021/ja047458b
View details for Web of Science ID 000224964500063
View details for PubMedID 15521782
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"Clicking" functionality onto electrode surfaces
LANGMUIR
2004; 20 (4): 1051-1053
View details for DOI 10.1021/la0362977
View details for Web of Science ID 000189013400010
View details for PubMedID 15803676
View details for PubMedCentralID PMC3428800
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Charge transfer on the nanoscale: Current status
JOURNAL OF PHYSICAL CHEMISTRY B
2003; 107 (28): 6668-6697
View details for DOI 10.1021/jp0268462
View details for Web of Science ID 000184084300003
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Modular assembly and air-stable electrochemistry of ruthenium porphyrin monolayers
LANGMUIR
2003; 19 (9): 3814-3821
View details for DOI 10.1021/la026948j
View details for Web of Science ID 000182467100037
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Heterogeneous electron-transfer kinetics for ruthenium and ferrocene redox moieties through alkanethiol monolayers on gold
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2003; 125 (7): 2004-2013
Abstract
The standard heterogeneous electron-transfer rate constants between substrate gold electrodes and either ferrocene or pentaaminepyridine ruthenium redox couples attached to the electrode surface by various lengths of an alkanethiol bridge as a constituent of a mixed self-assembled monolayer were measured as a function of temperature. The ferrocene was either directly attached to the alkanethiol bridge or attached through an ester (CO(2)) linkage. For long bridge lengths (containing more than 11 methylene groups) the rate constants were measured using either chronoamperometry or cyclic voltammetry; for the shorter bridges, the indirect laser induced temperature jump technique was employed to measure the rate constants. Analysis of the distance (bridge length) dependence of the preexponential factors obtained from an Arrhenius analysis of the rate constant versus temperature data demonstrates a clear limiting behavior at a surprisingly small value of this preexponential factor (much lower than would be expected on the basis of aqueous solvent dynamics). This limit is independent of both the identity of the redox couple and the nature of the linkage of the couple to the bridge, and it is definitely different (smaller) from the limit derived from an equivalent analysis of the rate constant (versus temperature) data for the interfacial electron-transfer reaction through oligophenylenevinylene bridges between gold electrodes and ferrocene. There are a number of possible explanations for this behavior including, for example, the possible effects of bridge conformational flexibility upon the electron-transfer kinetics. Nevertheless, conventional ideas regarding electronic coupling through alkane bridges and solvent dynamics are insufficient to explain the results reported here.
View details for DOI 10.1021/ja028458j
View details for Web of Science ID 000181088000053
View details for PubMedID 12580629
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Photoelectron spectroscopy to probe the mechanism of electron transfer through oligo(phenylene vinylene) bridges
JOURNAL OF PHYSICAL CHEMISTRY B
2003; 107 (5): 1170-1173
View details for DOI 10.1021/jp026734a
View details for Web of Science ID 000180755800010
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Submicrosecond electron transfer to monolayer-bound redox species on gold electrodes at large overpotentials
JOURNAL OF PHYSICAL CHEMISTRY B
2002; 106 (41): 10706-10713
View details for DOI 10.1021/jp026195+
View details for Web of Science ID 000178548600026
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Surface functionalization of alkyl monolayers by free-radical activation: Gas-phase photochlorination with Cl-2
LANGMUIR
2002; 18 (16): 6217-6221
View details for DOI 10.1021/la020095d
View details for Web of Science ID 000177224400040
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Olefin additions on H-Si(111): Evidence for a surface chain reaction initiated at isolated dangling bonds
LANGMUIR
2002; 18 (2): 305-307
View details for DOI 10.1021/la010823h
View details for Web of Science ID 000173423700001
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Future directions in solid state chemistry: report of the NSF-sponsored workshop
PROGRESS IN SOLID STATE CHEMISTRY
2002; 30 (1-2): 1-101
View details for DOI 10.1016/S0079-6786(02)00010-9
View details for Web of Science ID 000180774900001
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Distance dependence of the electron-transfer rate across covalently bonded monolayers on silicon
JOURNAL OF PHYSICAL CHEMISTRY B
2001; 105 (44): 10900-10904
View details for Web of Science ID 000172049100023
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Synthesis of ferrocenethiols containing oligo(phenylenevinylene) bridges and their characterization on gold electrodes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2001; 123 (33): 8033-8038
Abstract
Ferrocene-terminated oligo(phenylenevinylene) (OPV) methyl thiols have been prepared by orthogonal coupling of phenylene monomers. Ethoxy substituents on the phenyl rings improve the solubility of OPV, enabling the synthesis of longer oligomers. Self-assembled monolayers containing a mixture of a ferrocene OPV methyl thiol and a diluent alkanethiol were deposited on gold. A cyclic voltammetric study of monolayers containing oligomers of the same length with and without ethoxy solubilizing groups reveals that both solubilized and unsolubilized oligomers form well-packed self-assembled monolayers. Changing the position of the solubilizing groups on an oligomer chain does not preclude packing of the oligomer in the monolayer. Conventional chronoamperometry, which can be used to measure rate constants up to approximately 10(4) s(-1), is too slow to measure the electron-transfer rate through these oligomers over distances up to 35 A. OPV bridges are expected to be highly conjugated unlike oligo(phenyleneethynylene) bridges, which may be only partially conjugated because of rotation of the phenyl rings about the ethynylene bonds. Because of its high conjugation, OPV may prove useful as a molecular wire.
View details for Web of Science ID 000170494200009
View details for PubMedID 11506559
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Surface characterization and electrochemical properties of alkyl, fluorinated alkyl, and alkoxy monolayers on silicon
LANGMUIR
2001; 17 (11): 3460-3465
View details for Web of Science ID 000168955300046
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Rapid electron tunneling through oligophenylenevinylene bridges
SCIENCE
2001; 291 (5508): 1519-1523
Abstract
We measured rate constants of thermal, interfacial electron transfer through oligophenylenevinylene bridges between a gold electrode and a tethered redox species in contact with an aqueous electrolyte using the indirect laser-induced temperature jump technique. Analysis of the distance dependence indicates that, unlike other bridges studied to date, the rate constants are not limited by electronic coupling for bridges up to 28 angstroms long. The energy levels of the bridges relative to those of the redox species rule out hopping through the bridge. We conclude that, out to 28 angstroms, the transfer is limited by structural reorganization and that electron tunneling occurs in less than 20 picoseconds, suggesting that oligophenylenevinylene bridges could be useful for wiring molecular electronic elements.
View details for Web of Science ID 000167153400037
View details for PubMedID 11222852
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Effect of silicon surface termination on copper deposition in deionized water
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2001; 148 (1): C16-C20
View details for Web of Science ID 000166129600028
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Control of ozonated water cleaning process for photoresist removal
5th International Symposium on Ultra Clean Processing of Silicon Surfaces (UCPSS 2000)
SCITEC PUBLICATIONS LTD. 2001: 215–218
View details for Web of Science ID 000168449500053
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Photoreactivity of unsaturated compounds with hydrogen-terminated silicon(111)
LANGMUIR
2000; 16 (13): 5688-5695
View details for Web of Science ID 000087800300031
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Atomic-scale mechanistic study of iodine/alcohol passivated Si(100)
6th International Symposium on Cleaning Technology in Semiconductor Device Manufacturing
ELECTROCHEMICAL SOCIETY INC. 2000: 545–52
View details for Web of Science ID 000088232900070
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Defect states at silicon surfaces
20th International Conference on Defects in Semiconductors (ICDS-20)
ELSEVIER SCIENCE BV. 1999: 468–472
View details for Web of Science ID 000084452200109
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Hole limited recombination in polymer light-emitting diodes
APPLIED PHYSICS LETTERS
1999; 74 (11): 1510-1512
View details for Web of Science ID 000079078200002
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Alkyl-terminated Si(111) surfaces: A high-resolution, core level photoelectron spectroscopy study
JOURNAL OF APPLIED PHYSICS
1999; 85 (1): 213-221
View details for Web of Science ID 000077489200030
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Electronic desorption of alkyl monolayers from silicon by very highly charged ions
42nd International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIPBN)
A V S AMER INST PHYSICS. 1998: 3298–3300
View details for Web of Science ID 000077542300071
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Nucleation of trace copper on the H-Si(111) surface in aqueous fluoride solutions
JOURNAL OF PHYSICAL CHEMISTRY B
1998; 102 (41): 7919-7923
View details for Web of Science ID 000076617100001
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Synthesis and properties of metalloporphyrin monolayers and stacked multilayers bound to an electrode via site specific axial ligation to a self-assembled monolayer
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1998; 120 (18): 4478-4487
View details for Web of Science ID 000073645600027
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D-Si(111)(1x1) surface for the study of silicon etching in aqueous solutions
APPLIED PHYSICS LETTERS
1998; 72 (4): 477-479
View details for Web of Science ID 000071619600029
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Etch-pit initiation by dissolved oxygen on terraces of H-Si(111) (vol 71, pg 1679, 1997)
APPLIED PHYSICS LETTERS
1998; 72 (1): 133-133
View details for Web of Science ID 000071324400046
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Selective nucleation mechanism of trace metal contaminants at surface defects of silicon wafers in aqueous fluoride solution
5th Symposium on High Purity Silicon at the 194th Meeting of the Electrochemical-Society
ELECTROCHEMICAL SOCIETY INC. 1998: 250–57
View details for Web of Science ID 000076516800022
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Reactivity of the H-Si (111) surface
1st International Conference on Synchrotron Radiation in Materials Science (ICSRMS 96)
ELSEVIER SCIENCE BV. 1997: 94–101
View details for Web of Science ID 000071422800018
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Rates of interfacial electron transfer through pi-conjugated spacers
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1997; 119 (43): 10563-10564
View details for Web of Science ID A1997YD81500045
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Etch-pit initiation by dissolved oxygen on terraces of H-Si(111)
APPLIED PHYSICS LETTERS
1997; 71 (12): 1679-1681
View details for Web of Science ID A1997XW90700029
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Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction
APPLIED PHYSICS LETTERS
1997; 71 (8): 1056-1058
View details for Web of Science ID A1997XR75400022
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The bulge blister test as a probe of adhesion at the polymer/solid interface.
AMER CHEMICAL SOC. 1997: 485-POLY
View details for Web of Science ID A1997WP18703221
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Comparison of stresses in Al lines under various passivations
Symposium on Materials Reliability in Microelectronics, at the 1997 MRS Spring Meeting
MATERIALS RESEARCH SOCIETY. 1997: 415–420
View details for Web of Science ID A1997BJ82V00057
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Discussion of the Ward and Zaworotko lectures
Conference of the NATO Advanced Research Workshop on Modular Chemistry
SPRINGER. 1997: 423–432
View details for Web of Science ID 000080112300038
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Discussion of the Kahn and Brus lectures
Conference of the NATO Advanced Research Workshop on Modular Chemistry
SPRINGER. 1997: 309–321
View details for Web of Science ID 000080112300029
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Infrared spectroscopy of covalently bonded species on silicon surfaces: Deuterium, chlorine, and cobalt tetracarbonyl
Symposium on Science and Technology of Semiconductor Surface Preparation, at the 1997 MRS Spring Meeting
MATERIALS RESEARCH SOCIETY. 1997: 415–420
View details for Web of Science ID A1997BJ73X00056
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Preparation of pit-free hydrogen-terminated Si(111) in deoxygenated ammonium fluoride
Symposium on Science and Technology of Semiconductor Surface Preparation, at the 1997 MRS Spring Meeting
MATERIALS RESEARCH SOCIETY. 1997: 299–304
View details for Web of Science ID A1997BJ73X00038
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Discussion of the Mallouk and Fox lectures
Conference of the NATO Advanced Research Workshop on Modular Chemistry
SPRINGER. 1997: 69–73
View details for Web of Science ID 000080112300007
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An analysis of infrared spectroscopic geometries
Symposium on Science and Technology of Semiconductor Surface Preparation, at the 1997 MRS Spring Meeting
MATERIALS RESEARCH SOCIETY. 1997: 353–358
View details for Web of Science ID A1997BJ73X00047
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STM studies of electrode/electrolyte interfaces and silicon surface reactions in controlled atmospheres
Symposium on Electrochemical Synthesis and Modification of Materials, at the 1996 MRS Fall Meeting
MATERIALS RESEARCH SOCIETY. 1997: 173–183
View details for Web of Science ID A1997BJ46P00023
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Discussion of the Ebbesen and Scuseria lectures
Conference of the NATO Advanced Research Workshop on Modular Chemistry
SPRINGER. 1997: 275–286
View details for Web of Science ID 000080112300026
- Mechanism for the chemisorption of contaminants on hydrogen-terminated silicon surfaces Mater. Res. Soc. Proc. 1997; 436: 115-120
- Using self-assembled monolayers to modify electrode interfaces in organic light-emitting diodes Polymer Preprints, Division of Polymer Chemistry 1997; 38: 936-936
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Measuring interfacial fracture toughness with the blister test
Symposium on Thin Films - Stresses and Mechanical Properties VI, at the 1996 MRS Spring Meeting
MATERIALS RESEARCH SOCIETY. 1997: 115–120
View details for Web of Science ID A1997BH29Z00018
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Bioreactive self-assembled monolayers on hydrogen-passivated Si(111) as a new class of atomically flat substrates for biological scanning probe microscopy
JOURNAL OF STRUCTURAL BIOLOGY
1997; 119 (2): 189-201
Abstract
This is the first report of bioreactive self-assembled monolayers, covalently bound to atomically flat silicon surfaces and capable of binding biomolecules for investigation by scanning probe microscopy and other surface-related assays and sensing devices. These monolayers are stable under a wide range of conditions and allow tailor-made functionalization for many purposes. We describe the substrate preparation and present an STM and SFM characterization, partly performed with multiwalled carbon nanotubes as tapping-mode supertips. Furthermore, we present two strategies of introducing in situ reactive headgroup functionalities. One method entails a free radical chlorosulfonation process with subsequent sulfonamide formation. A second method employs singlet carbenemediated hydrogen-carbon insertion of a heterobifunctional, amino-reactive trifluoromethyl-diazirinyl crosslinker. We believe that this new substrate is advantageous to others, because it (i) is atomically flat over large areas and can be prepared in a few hours with standard equipment, (ii) is stable under most conditions, (iii) can be modified to adjust a certain degree of reactivity and hydrophobicity, which allows physical adsorption or covalent crosslinking of the biological specimen, (iv) builds the bridge between semiconductor microfabrication and organic/biological molecular systems, and (v) is accessible to nanopatterning and applications requiring conductive substrates.
View details for Web of Science ID A1997XN38200014
View details for PubMedID 9245759
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SYNTHESIS AND CHARACTERIZATION OF UNSYMMETRIC FERROCENE-TERMINATED PHENYLETHYNYL OLIGOMERS CP(2)FE-[C-C-C6H4](N),-X(X=SH, SME, SOME, AND SO(2)ME)
ORGANOMETALLICS
1995; 14 (10): 4808-4815
View details for Web of Science ID A1995RY97100049
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THE KINETICS OF ELECTRON-TRANSFER THROUGH FERROCENE-TERMINATED ALKANETHIOL MONOLAYERS ON GOLD
JOURNAL OF PHYSICAL CHEMISTRY
1995; 99 (35): 13141-13149
View details for Web of Science ID A1995RR84600016
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THIOPHENOL PROTECTING GROUPS FOR THE PALLADIUM-CATALYZED HECK REACTION - EFFICIENT SYNTHESES OF CONJUGATED ARYLTHIOLS
TETRAHEDRON LETTERS
1995; 36 (26): 4525-4528
View details for Web of Science ID A1995RG28900002
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ALKYL MONOLAYERS ON SILICON PREPARED FROM 1-ALKENES AND HYDROGEN-TERMINATED SILICON
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1995; 117 (11): 3145-3155
View details for Web of Science ID A1995QN45800019
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The Kinetics of Electron Transfer Through Ferrocene-Terminated Alkanethiol Monolayers on Gold
J. Phys. Chem.
1995; 99 (35): 13141-13149
View details for DOI 10.1021/j100035a016
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Alkyl Monolayers on Silicon Prepared from 1-Alkenes and Hydrogen-Terminated Silicon
J. Am. Chem. Soc.
1995; 117 (11): 3145-3155
View details for DOI 10.1021/ja00116a019
- Synthesis and Characterization of Unsymmetric Ferrocene-Terminated Phenylethynyl Oligomers Cp2Fe-[C.tplbond.C-C6H4]n-X, (X = SH, SMe, SOMe, and SO2Me) Organometallics 1995; 14: 4808-4815
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Blister test analysis methods
Symposium on Thin Films - Stresses and Mechanical Properties V, at the 1994 Fall Meeting of the Materials-Research-Society
MATERIALS RESEARCH SOCIETY. 1995: 585–590
View details for Web of Science ID A1995BD53A00090
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AN UNEXPECTED PACKING OF FLUORINATED N-ALKANE THIOLS ON AU(111) - A COMBINED ATOMIC-FORCE MICROSCOPY AND X-RAY-DIFFRACTION STUDY
JOURNAL OF CHEMICAL PHYSICS
1994; 101 (5): 4301-4306
View details for Web of Science ID A1994PE11000097
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PROTECTIVE TREATMENTS FOR NICKEL-BASED CONTACT MATERIALS
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
1994; 141 (7): 1977-1982
View details for Web of Science ID A1994NX19600053
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STRUCTURAL STUDIES OF ZIRCONIUM ALKYLPHOSPHONATE MONOLAYERS AND MULTILAYER ASSEMBLIES
LANGMUIR
1993; 9 (8): 2156-2160
View details for Web of Science ID A1993LU39600042
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THE ELECTRODE-ELECTROLYTE INTERFACE - A STATUS-REPORT
JOURNAL OF PHYSICAL CHEMISTRY
1993; 97 (28): 7147-7173
View details for Web of Science ID A1993LV57900007
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SUBSTRATE DEPENDENCE OF THE SURFACE-STRUCTURE AND CHAIN PACKING OF DOCOSYL MERCAPTAN SELF-ASSEMBLED ON THE (111), (110), AND (100) FACES OF SINGLE-CRYSTAL GOLD
JOURNAL OF CHEMICAL PHYSICS
1993; 98 (5): 4234-4245
View details for Web of Science ID A1993KR11100070
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SUPERLATTICE STRUCTURE AT THE SURFACE OF A MONOLAYER OF OCTADECANETHIOL SELF-ASSEMBLED ON AU(111)
JOURNAL OF CHEMICAL PHYSICS
1993; 98 (4): 3503-3511
View details for Web of Science ID A1993KP93800103
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ION SURFACE COLLISIONS AT FUNCTIONALIZED SELF-ASSEMBLED MONOLAYER SURFACES
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
1992; 122: 181-217
View details for Web of Science ID A1992KH29500016
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SYNTHESIS AND DEPOSITION OF ELECTRON-DONORS, ACCEPTORS, AND INSULATORS AS COMPONENTS OF ZIRCONIUM DIPHOSPHONATE MULTILAYER FILMS
ACS SYMPOSIUM SERIES
1992; 499: 24-32
View details for Web of Science ID A1992JG85000003
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SYNTHESIS AND DEPOSITION OF ELECTRON-DONORS, ACCEPTORS, AND INSULATORS AS COMPONENTS OF ZIRCONIUM DIPHOSPHONATE MULTILAYER FILMS
SYMP ON SUPRAMOLECULAR ARCHITECTURE, AT THE 201ST NATIONAL MEETING OF THE AMERICAN CHEMICAL SOC
AMER CHEMICAL SOC. 1992: 24–32
View details for Web of Science ID A1992BW18J00003
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POLAR ORIENTATION OF DYES IN ROBUST MULTILAYERS BY ZIRCONIUM PHOSPHATE-PHOSPHONATE INTERLAYERS
SCIENCE
1991; 254 (5037): 1485-1487
Abstract
Polar orientation of molecules in solids leads to materials with potentially useful properties such as nonlinear optical and electrooptical activity, electrochromism, and pyroelectricity. A simple self-assembly procedure for preparing such materials is introduced that yields multiple polar dye monolayers on solid surfaces joined by zirconium phosphate-phosphonate interlayers. Second harmonic generation (SHG) shows that the multilayers have polar order that does not decrease with increasing numbers (up to a large number) of monolayers in the film. The inorganic interlayers, as determined by SHG, impart excellent orientational stability to the dye molecules, with the onset of orientational randomization above 150 degrees C.
View details for Web of Science ID A1991GT90300032
View details for PubMedID 17773297
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SURFACE-REACTIONS AND SURFACE-INDUCED DISSOCIATION OF POLYATOMIC IONS AT SELF-ASSEMBLED ORGANIC MONOLAYER SURFACES
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1991; 113 (23): 8967-8969
View details for Web of Science ID A1991GP03700067
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INSITU SCANNING TUNNELING MICROSCOPY OF CORROSION OF SILVER-GOLD ALLOYS
SCIENCE
1991; 254 (5032): 687-689
Abstract
An in situ scanning tunneling microscope (STM) was used to observe the morphological changes accompanying the selective dissolution of Ag from low-Ag content Ag-Au alloys in dilute perchloric acid. This study was undertaken to explore the role of surface diffusion in alloy corrosion processes. These results are interpreted within the framework of the kink-ledge-terrace model of a crystal surface and a recent model of alloy corrosion based on a variant of percolation theory. The corrosion process leads to roughening of the surface by dissolution of Ag atoms from terrace sites. Annealing or smoothening of the surface occurs by vacancy migration through clusters and the subsequent annihilation of clusters at terrace ledges.
View details for Web of Science ID A1991GN47400033
View details for PubMedID 17774794
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QUATERTHIOPHENEDIPHOSPHONIC ACID (QDP) - A RIGID, ELECTRON-RICH BUILDING BLOCK FOR ZIRCONIUM-BASED MULTILAYERS
CHEMISTRY OF MATERIALS
1991; 3 (4): 699-703
View details for Web of Science ID A1991FZ19000025
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SURFACE-STRUCTURE AND THERMAL MOTION OF NORMAL-ALKANE THIOLS SELF-ASSEMBLED ON AU(111) STUDIED BY LOW-ENERGY HELIUM DIFFRACTION
JOURNAL OF CHEMICAL PHYSICS
1991; 94 (12): 8493-8502
View details for Web of Science ID A1991FQ58500036
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ROOM-TEMPERATURE SURFACE-DIFFUSION MECHANISMS OBSERVED BY SCANNING TUNNELING MICROSCOPY
5TH INTERNATIONAL CONF ON SCANNING TUNNELING MICROSCOPY/SPECTROSCOPY ( STM 90 ) / 1ST INTERNATIONAL CONF ON NANOMETER SCALE SCIENCE AND TECHNOLOGY ( NANO 1 )
A V S AMER INST PHYSICS. 1991: 964–68
View details for Web of Science ID A1991FL00400122
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FREE-ENERGY AND TEMPERATURE-DEPENDENCE OF ELECTRON-TRANSFER AT THE METAL-ELECTROLYTE INTERFACE
SCIENCE
1991; 251 (4996): 919-922
Abstract
The rate constant of the electron-transfer reaction between a gold electrode and an electroactive ferrocene group has been measured at a structurally well-defined metal-electrolyte interface at temperatures from 1 degrees to 47 degrees C and reaction free energies from -1.0 to +0.8 electron volts (eV). The ferrocene group was positioned a fixed distance from the gold surface by the self-assembly of a mixed thiol monolayer of (eta(5)C(5)H(5))Fe(eta(5)C(5)H(4))CO(2)(CH(2))(16)SH and CH(3)(CH(2))(15)SH. Rate constants from 1 per second (s(-1)) to 2 x 10(4) s(-1) in 1 molar HClO(4) are reasonably fit with a reorganization energy of 0.85 eV and a prefactor for electron tunneling of 7 x 10(4) s(-1) eV(-1). Such self-assembled monolayers can be used to systematically probe the dependence of electron-transfer rates on distance, medium, and spacer structure, and to provide an empirical basis for the construction of interfacial devices such as sensors and transducers that utilize macroscopically directional electron-transfer reactions.
View details for Web of Science ID A1991EY62900038
View details for PubMedID 17847385
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ELECTRICAL AND NONLINEAR OPTICAL-PROPERTIES OF ZIRCONIUM PHOSPHONATE MULTILAYER ASSEMBLIES
CONF ON NONLINEAR OPTICAL PROPERTIES OF ORGANIC MATERIALS 4
SPIE - INT SOC OPTICAL ENGINEERING. 1991: 370–376
View details for Web of Science ID A1991BU87X00039
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HELIUM DIFFRACTION FROM OVERLAYERS PHYSISORBED ON A SELF-ASSEMBLED ORGANIC MONOLAYER
LANGMUIR
1990; 6 (12): 1804-1806
View details for Web of Science ID A1990EP43900017
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SELF-ASSEMBLY OF ORGANIC MULTILAYERS WITH POLAR ORDER USING ZIRCONIUM-PHOSPHATE BONDING BETWEEN LAYERS
LANGMUIR
1990; 6 (10): 1567-1571
View details for Web of Science ID A1990EF84100007
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COADSORPTION OF FERROCENE-TERMINATED AND UNSUBSTITUTED ALKANETHIOLS ON GOLD - ELECTROACTIVE SELF-ASSEMBLED MONOLAYERS
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1990; 112 (11): 4301-4306
View details for Web of Science ID A1990DE90200028
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CHEMICAL FUNCTIONALITY IN SELF-ASSEMBLED MONOLAYERS - STRUCTURAL AND ELECTROCHEMICAL PROPERTIES
LANGMUIR
1990; 6 (3): 682-691
View details for Web of Science ID A1990CW17300026
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MOLECULAR ORDER AT THE SURFACE OF AN ORGANIC MONOLAYER STUDIED BY LOW-ENERGY HELIUM DIFFRACTION
JOURNAL OF CHEMICAL PHYSICS
1989; 91 (7): 4421-4423
View details for Web of Science ID A1989AR31300074
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INSITU SCANNING-TUNNELING-MICROSCOPE OBSERVATION OF ROUGHENING, ANNEALING, AND DISSOLUTION OF GOLD(111) IN AN ELECTROCHEMICAL-CELL
PHYSICAL REVIEW LETTERS
1989; 62 (8): 929-932
View details for Web of Science ID A1989T264800023
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STM STUDY OF THE SURFACE-MORPHOLOGY OF GOLD ON MICA
SURFACE SCIENCE
1988; 200 (1): 45-66
View details for Web of Science ID A1988N824800014
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MONOLAYER VIBRATIONAL SPECTROSCOPY BY INFRARED-VISIBLE SUM GENERATION AT METAL AND SEMICONDUCTOR SURFACES
CHEMICAL PHYSICS LETTERS
1987; 141 (4): 350-356
View details for Web of Science ID A1987K961700016
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SPONTANEOUSLY ORGANIZED MOLECULAR ASSEMBLIES .4. STRUCTURAL CHARACTERIZATION OF NORMAL-ALKYL THIOL MONOLAYERS ON GOLD BY OPTICAL ELLIPSOMETRY, INFRARED-SPECTROSCOPY, AND ELECTROCHEMISTRY
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1987; 109 (12): 3559-3568
View details for Web of Science ID A1987H723400011
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REDOX CAPACITY AND DIRECT-CURRENT ELECTRON CONDUCTIVITY IN ELECTROACTIVE MATERIALS
JOURNAL OF PHYSICAL CHEMISTRY
1986; 90 (7): 1479-1484
View details for Web of Science ID A1986A654100051
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MICROMETER-SPACED PLATINUM INTERDIGITATED ARRAY ELECTRODE - FABRICATION, THEORY, AND INITIAL USE
ANALYTICAL CHEMISTRY
1986; 58 (3): 601-607
View details for Web of Science ID A1986A216900029
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ELECTROACTIVE POLYMERS AND MACROMOLECULAR ELECTRONICS
SCIENCE
1986; 231 (4733): 25-31
Abstract
Electrodes can be coated with electrochemically reactive polymers in several microstructural formats called sandwich, array, bilayer, micro-, and ion-gate electrodes. These microstructures can be used to study the transport of electrons and ions through the polymers as a function of the polymer oxidation state, which is essential for understanding the conductivity properties of these new chemical materials. The microstructures also exhibit potentially useful electrical and optical responses, including current rectification, charge storage and amplification, electron-hole pair separation, and gates for ion flow.
View details for Web of Science ID A1986AWR2700018
View details for PubMedID 17819225
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EFFECT OF MAGNETIC-FIELDS ON THE TRIPLET-STATE LIFETIME IN PHOTOSYNTHETIC REACTION CENTERS - EVIDENCE FOR THERMAL REPOPULATION OF THE INITIAL RADICAL PAIR
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1985; 82 (20): 6850-6854
Abstract
The lifetime of the molecular triplet state formed by recombination of the radical ion pair in quinonedepleted bacterial photosynthetic reaction centers is found to depend on applied magnetic field strength. It is suggested that this magnetic field effect results from thermally activated repopulation of the same radical ion pair that generates the triplet. Consistent with this hypothesis, the magnetic field effect on the triplet lifetime disappears at low temperature where the triplet state decays exclusively by ordinary intersystem crossing. This activated pathway for the decay of the triplet state can explain the strong temperature dependence of the triplet decay rate. A detailed theoretical treatment of the problem within a set of physically reasonable assumptions relates the observed temperature dependence of the triplet decay rate to the energy gap between the radical ion pair intermediate and the triplet state. This energy gap is estimated to be about 950 cm(-1) (0.12 eV). Combined with an estimate of the energy of the donor excited state, we obtain an energy gap between the excited singlet state of the donor and the radical ion pair of 2,250 cm(-1) (0.28 eV).
View details for Web of Science ID A1985ATC6000028
View details for PubMedID 16593615
View details for PubMedCentralID PMC390785
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ELECTROCHEMISTRY OF POLYMER-FILMS NOT IMMERSED IN SOLUTION - ELECTRON-TRANSFER ON AN ION BUDGET
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1985; 107 (9): 2824-2826
View details for Web of Science ID A1985AGH5200055
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MAGNETIC-FIELD DEPENDENCE OF RADICAL-PAIR DECAY KINETICS AND MOLECULAR TRIPLET QUANTUM YIELD IN QUINONE-DEPLETED REACTION CENTERS
BIOCHIMICA ET BIOPHYSICA ACTA
1984; 766 (2): 424-437
View details for Web of Science ID A1984TK78800018
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MAGNETIC-FIELD EFFECTS ON REACTION YIELDS IN THE SOLID-STATE - AN EXAMPLE FROM PHOTOSYNTHETIC REACTION CENTERS
ANNUAL REVIEW OF PHYSICAL CHEMISTRY
1983; 34: 389-417
View details for Web of Science ID A1983RN94700016
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CONTRIBUTIONS OF SPIN SPIN INTERACTIONS TO THE MAGNETIC-FIELD DEPENDENCE OF THE TRIPLET QUANTUM YIELD IN PHOTOSYNTHETIC REACTION CENTERS
CHEMICAL PHYSICS LETTERS
1982; 87 (6): 582-588
View details for Web of Science ID A1982NN15500016
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USE OF LARGE MAGNETIC-FIELDS TO PROBE PHOTOINDUCED ELECTRON-TRANSFER REACTIONS - AN EXAMPLE FROM PHOTOSYNTHETIC REACTION CENTERS
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1982; 104 (5): 1452-1454
View details for Web of Science ID A1982NF10300062
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ANISOTROPIC MAGNETIC-INTERACTIONS IN THE PRIMARY RADICAL ION-PAIR OF PHOTOSYNTHETIC REACTION CENTERS
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
1982; 79 (15): 4632-4636
Abstract
The quantum yield of triplets formed by ion-pair recombination in quinone-depleted photosynthetic reaction centers is found to depend on their orientation in a magnetic field. This new effect is expected to be a general property of radical pair reactions in the solid state. For 0 < H < 1,000 G, the quantum yield anisotropy is caused by anisotropic electron dipole-electron dipole or nuclear hyperfine interactions, or both. For high fields it is dominated by the anisotropy of the difference g-tensor in the radical ion-pair. The magnitude and sign of the contribution of each interaction depend not only on the values of the principal components of each anisotropic tensor but also on the geometric relationship of the principal axes of each tensor to the transition dipole moment used to detect the yield. A detailed formalism is presented relating these quantities to the observed yield anisotropy. The expected magnitude of each anisotropic parameter is discussed. It is demonstrated that the field dependence of the yield anisotropy is consistent with these values for certain reaction center geometries.
View details for Web of Science ID A1982PB77200023
View details for PubMedID 16578764
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DEPENDENCE OF THE YIELD OF A RADICAL-PAIR REACTION IN THE SOLID-STATE ON ORIENTATION IN A MAGNETIC-FIELD
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1982; 104 (9): 2674-2675
View details for Web of Science ID A1982NN22100072
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THE EFFECT OF LARGE MAGNETIC-FIELDS AND THE G-FACTOR DIFFERENCE ON THE TRIPLET POPULATION IN PHOTOSYNTHETIC REACTION CENTERS
CHEMICAL PHYSICS LETTERS
1980; 74 (1): 113-118
View details for Web of Science ID A1980KG96500026
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INTERACTIONS OF SMALL ORGANIC RINGS WITH TRANSITION-METALS - FORMATION OF ETA-3-CYCLOBUTENONYL COMPLEXES BY THE RING EXPANSION OF 2-CYCLOPROPENE-1-CARBONYL METAL SPECIES
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1979; 101 (1): 233-235
View details for Web of Science ID A1979GC40300046
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CATIONIC COBALT(I) CARBONYL-COMPOUNDS CONTAINING COMPLEXED CYCLOBUTADIENES
JOURNAL OF ORGANOMETALLIC CHEMISTRY
1979; 169 (1): C12-C14
View details for Web of Science ID A1979GQ98100018