Stanford Advisors

All Publications

  • In Situ Investigation of Ultrafast Dynamics of Hot Electron-Driven Photocatalysis in Plasmon-Resonant Grating Structures JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Wang, Y., Wang, Y., Aravind, I., Cai, Z., Shen, L., Zhang, B., Wang, B., Chen, J., Zhao, B., Shi, H., Dawlaty, J. M., Cronin, S. B. 2022; 144 (8): 3517-3526


    Understanding the relaxation and injection dynamics of hot electrons is crucial to utilizing them in photocatalytic applications. While most studies have focused on hot carrier dynamics at metal/semiconductor interfaces, we study the in situ dynamics of direct hot electron injection from metal to adsorbates. Here, we report a hot electron-driven hydrogen evolution reaction (HER) by exciting the localized surface plasmon resonance (LSPR) in Au grating photoelectrodes. In situ ultrafast transient absorption (TA) measurements show a depletion peak resulting from hot electrons. When the sample is immersed in solution under -1 V applied potential, the extracted electron-phonon interaction time decreases from 0.94 to 0.67 ps because of additional energy dissipation channels. The LSPR TA signal is redshifted with delay time because of charge transfer and subsequent change in the dielectric constant of nearby solution. Plateau-like photocurrent peaks appear when exciting a 266 nm linewidth grating with p-polarized (on resonance) light, accompanied by a similar profile in the measured absorptance. Double peaks in the photocurrent measurement are observed when irradiating a 300 nm linewidth grating. The enhancement factor (i.e., reaction rate) is 15.6× between p-polarized and s-polarized light for the 300 nm linewidth grating and 4.4× for the 266 nm linewidth grating. Finite-difference time domain (FDTD) simulations show two resonant modes for both grating structures, corresponding to dipolar LSPR modes at the metal/fused silica and metal/water interfaces. To our knowledge, this is the first work in which LSPR-induced hot electron-driven photochemistry and in situ photoexcited carrier dynamics are studied on the same plasmon resonance structure with and without adsorbates.

    View details for DOI 10.1021/jacs.1c12069

    View details for Web of Science ID 000773646200023

    View details for PubMedID 35188777

  • CO2 Reduction to Higher Hydrocarbons by Plasma Discharge in Carbonated Water ACS ENERGY LETTERS Yang, S., Zhao, B., Aravind, I. A., Wang, Y., Zhang, B., Weng, S., Cai, Z., Li, R., Baygi, A., Smith, A., Gundersen, M. A., Cronin, S. B. 2021; 6 (11): 3924-3930
  • Voltage-induced modulation in the charge state of Si-vacancy defects in diamond using high voltage nanosecond pulses APPLIED PHYSICS LETTERS Weng, S., Coleman, C., Aravind, I., Wang, Y., Zhao, B., Cronin, S. B. 2021; 119 (17)

    View details for DOI 10.1063/5.0066537

    View details for Web of Science ID 000730999400015

  • Monitoring Reaction Intermediates in Plasma-Driven SO2, NO, and NO2 Remediation Chemistry Using In Situ SERS Spectroscopy ANALYTICAL CHEMISTRY Li, S., Zhao, B., Aguirre, A., Wang, Y., Li, R., Yang, S., Aravind, I., Cai, Z., Chen, R., Jensen, L., Cronin, S. B. 2021; 93 (16): 6421-6427


    In situ surface-enhanced Raman scattering (SERS) spectroscopy is used to identify the key reaction intermediates during the plasma-based removal of NO and SO2 under dry and wet conditions on Ag nanoparticles. Density functional theory (DFT) calculations are used to confirm the experimental observations by calculating the vibrational modes of the surface-bound intermediate species. Here, we provide spectroscopic evidence that the wet plasma increases the SO2 and the NOx removal through the formation of highly reactive OH radicals, driving the reactions to H2SO4 and HNO3, respectively. We observed the formation of SO3 and SO4 species in the SO2 wet-plasma-driven remediation, while in the dry plasma, we only identified SO3 adsorbed on the Ag surface. During the removal of NO in the dry and wet plasma, both NO2 and NO3 species were observed on the Ag surface; however, the concentration of NO3 species was enhanced under wet-plasma conditions. By closing the loop between the experimental and DFT-calculated spectra, we identified not only the adsorbed species associated with each peak in the SERS spectra but also their orientation and adsorption site, providing a detailed atomistic picture of the chemical reaction pathway and surface interaction chemistry.

    View details for DOI 10.1021/acs.analchem.0c05413

    View details for Web of Science ID 000645428400017

    View details for PubMedID 33855854

  • Enhanced Plasma Generation from Metal Nanostructures via Photoexcited Hot Electrons JOURNAL OF PHYSICAL CHEMISTRY C Zhao, B., Aravind, I., Yang, S., Wang, Y., Li, R., Zhang, B., Wang, Y., Dawlaty, J. M., Cronin, S. B. 2021; 125 (12): 6800-6804
  • Hot Electron Plasmon-Resonant Grating Structures for Enhanced Photochemistry: A Theoretical Study CRYSTALS Aravind, I., Wang, Y., Cai, Z., Shen, L., Zhao, B., Yang, S., Wang, Y., Dawlaty, J. M., Gibson, G. N., Guignon, E., Cady, N. C., Page, W. D., Pilar, A., Cronin, S. B. 2021; 11 (2)
  • Au Nanoparticle Enhancement of Plasma-Driven Methane Conversion into Higher Order Hydrocarbons via Hot Electrons ACS APPLIED NANO MATERIALS Zhao, B., Aravind, I., Yang, S., Wang, Y., Li, R., Cronin, S. B. 2020; 3 (12): 12388-12393
  • Enhanced Low-Temperature Thermoelectric Performance in (PbSe)(1+delta)(VSe2)(1) Heterostructures due to Highly Correlated Electrons in Charge Density Waves NANO LETTERS Wang, Y., Hamann, D. M., Cordova, D. M., Chen, J., Wang, B., Shen, L., Cai, Z., Shi, H., Karapetrova, E., Aravind, I., Shi, L., Johnson, D. C., Cronin, S. B. 2020; 20 (11): 8008-8014


    We explore the effect of charge density wave (CDW) on the in-plane thermoelectric transport properties of (PbSe)1+δ(VSe2)1 and (PbSe)1+δ(VSe2)2 heterostructures. In (PbSe)1+δ(VSe2)1 we observe an abrupt 86% increase in the Seebeck coefficient, 245% increase in the power factor, and a slight decrease in resistivity over the CDW transition. This behavior is not observed in (PbSe)1+δ(VSe2)2 and is rather unusual compared to the general trend observed in other materials. The abrupt transition causes a deviation from the Mott relationship through correlated electron states. Raman spectra of the (PbSe)1+δ(VSe2)1 material show the emergence of additional peaks below the CDW transition temperature associated with VSe2 material. Temperature-dependent in-plane X-ray diffraction (XRD) spectra show a change in the in-plane thermal expansion of VSe2 in (PbSe)1+δ(VSe2)1 due to lattice distortion. The increase in the power factor and decrease in the resistivity due to CDW suggest a potential mechanism for enhancing the thermoelectric performance at the low temperature region.

    View details for DOI 10.1021/acs.nanolett.0c02882

    View details for Web of Science ID 000592495700028

    View details for PubMedID 33095023

  • Monitoring Local Electric Fields using Stark Shifts on Napthyl Nitrile-Functionalized Silicon Photoelectrodes JOURNAL OF PHYSICAL CHEMISTRY C Shi, H., Pekarek, R. T., Chen, R., Zhang, B., Wang, Y., Aravind, I., Cai, Z., Jensen, L., Neale, N. R., Cronin, S. B. 2020; 124 (31): 17000-17005
  • Hot Electron Driven Photocatalysis on Plasmon-Resonant Grating Nanostructures ACS APPLIED MATERIALS & INTERFACES Wang, Y., Aravind, I., Cai, Z., Shen, L., Gibson, G. N., Chen, J., Wang, B., Shi, H., Song, B., Guignon, E., Cady, N. C., Page, W. D., Pilar, A., Cronin, S. B. 2020; 12 (15): 17459-17465


    We demonstrate the hot electron injection of photoexcited carriers in an Ag-based plasmon resonant grating structure. By varying the incident angle of irradiation, sharp dips are observed in the reflectance with p-polarized light (electric field perpendicular to grating lines) when there is wavevector matching between the incident light and the plasmon resonant modes of the grating and no angle dependence is observed with s-polarized light. This configuration enables us to compare photoelectrochemical current produced by plasmon resonant excitation with that of bulk metal interband absorption simply by rotating the polarization of the incident light while keeping all other parameters of the measurement fixed. With 633 nm light, we observed a 12-fold enhancement in the photocurrent (i.e., reaction rate) between resonant and nonresonant polarizations at incident angles of ±7.6° from normal. At 785 nm irradiation, we observed similar resonant profiles to those obtained with 633 nm wavelength light but with a 44-fold enhancement factor. Using 532 nm light, we observed two resonant peaks (with approximately 10× enhancement) in the photocurrent at 19.4° and 28.0° incident angles, each corresponding to higher order modes in the grating with more nodes per period. The lower enhancement factors observed at shorter wavelengths are attributed to interband transitions, which provide a damping mechanism for the plasmon resonance. Finite difference time domain (FDTD) simulations of these grating structures confirm the resonant profiles observed in the angle-dependent spectra of these gratings and provide a detailed picture of the electric field profiles on and off resonance.

    View details for DOI 10.1021/acsami.0c00066

    View details for Web of Science ID 000526330900030

    View details for PubMedID 32212673