Honors & Awards
MRSEC Fellowship, Northwestern University (2012-2014)
International Institute for Nanotechnology (IIN) Outstanding Researcher Award, Northwestern University (2015)
MRS Fall Meeting Graduate Student Award (GSA) Silver Award, Materials Research Society (2015)
The John E. Hilliard Symposium Best Speaker Award, Northwestern University (2016)
Chinese Government Award for Outstanding Students Abroad, Chinese Government (2016)
Bachelor of Science, Tsinghua University (2008)
Master of Science, Tsinghua University (2011)
Doctor of Philosophy, Northwestern University (2016)
Yi Cui, Postdoctoral Faculty Sponsor
Fast lithium growth and short circuit induced by localized-temperature hotspots in lithium batteries.
2019; 10 (1): 2067
Fast-charging and high-energy-density batteries pose significant safety concerns due to high rates of heat generation. Understanding how localized high temperatures affect the battery is critical but remains challenging, mainly due to the difficulty of probing battery internal temperature with high spatial resolution. Here we introduce a method to induce and sense localized high temperature inside a lithium battery using micro-Raman spectroscopy. We discover that temperature hotspots can induce significant lithium metal growth as compared to the surrounding lower temperature area due to the locally enhanced surface exchange current density. More importantly, localized high temperature can be one of the factors to cause battery internal shorting, which further elevates the temperature and increases the risk of thermal runaway. This work provides important insights on the effects of heterogeneous temperatures within batteries and aids the development of safer batteries, thermal management schemes, and diagnostic tools.
View details for PubMedID 31061393
- In Situ X-ray Absorption Spectroscopic Investigation of the Capacity Degradation Mechanism in Mg/S Batteries NANO LETTERS 2019; 19 (5): 2928–34
Wrinkled Graphene Cages as Hosts for High-Capacity Li Metal Anodes Shown by Cryogenic Electron Microscopy.
Lithium (Li) metal has long been considered the "holy grail" of battery anode chemistry but is plagued by low efficiency and poor safety due to its high chemical reactivity and large volume fluctuation, respectively. Here we introduce a new host of wrinkled graphene cage (WGC) for Li metal. Different from recently reported amorphous carbon spheres, WGC show highly improved mechanical stability, better Li ion conductivity, and excellent solid electrolyte interphase (SEI) for continuous robust Li metal protection. At low areal capacities, Li metal is preferentially deposited inside the graphene cage. Cryogenic electron microscopy characterization shows that a uniform and stable SEI forms on the WGC surface that can shield the Li metal from direct exposure to electrolyte. With increased areal capacities, Li metal is plated densely and homogeneously into the outer pore spaces between graphene cages with no dendrite growth or volume change. As a result, a high Coulombic efficiency (CE) of 98.0% was achieved under 0.5 mA/cm2 and 1-10 mAh/cm2 in commercial carbonate electrolytes, and a CE of 99.1% was realized with high-concentration electrolytes under 0.5 mA/cm2 and 3 mAh/cm2. Full cells using WGC electrodes with prestored Li paired with Li iron phosphate showed greatly improved cycle lifetime. With 10 mAh/cm2 Li metal deposition, the WGC/Li compositeanodewas able to provide a high specific capacity of 2785 mAh/g. With its roll-to-roll compatible fabrication procedure, WGC serves as a highly promising material for the practical realization of Li metal anodes in next-generation high energy density secondary batteries.
View details for PubMedID 30676759
Direct electrochemical generation of supercooled sulfur microdroplets well below their melting temperature.
Proceedings of the National Academy of Sciences of the United States of America
Supercooled liquid sulfur microdroplets were directly generated from polysulfide electrochemical oxidation on various metal-containing electrodes. The sulfur droplets remain liquid at 155 °C below sulfur's melting point (T m = 115 °C), with fractional supercooling change (T m - T sc)/T m larger than 0.40. In operando light microscopy captured the rapid merging and shape relaxation of sulfur droplets, indicating their liquid nature. Micropatterned electrode and electrochemical current allow precise control of the location and size of supercooled microdroplets, respectively. Using this platform, we initiated and observed the rapid solidification of supercooled sulfur microdroplets upon crystalline sulfur touching, which confirms supercooled sulfur's metastability at room temperature. In addition, the formation of liquid sulfur in electrochemical cell enriches lithium-sulfur-electrolyte phase diagram and potentially may create new opportunities for high-energy Li-S batteries.
View details for PubMedID 30602455
Reversible and selective ion intercalation through the top surface of few-layer MoS2.
2018; 9 (1): 5289
Electrochemical intercalation of ions into the van der Waals gap of two-dimensional (2D) layered materials is a promising low-temperature synthesis strategy to tune their physical and chemical properties. It is widely believed that ions prefer intercalation into the van der Waals gap through the edges of the 2D flake, which generally causes wrinkling and distortion. Here we demonstrate that the ions can also intercalate through the top surface of few-layer MoS2 and this type of intercalation is more reversible and stable compared to the intercalation through the edges. Density functional theory calculations show that this intercalation is enabled by the existence of natural defects in exfoliated MoS2 flakes. Furthermore, we reveal that sealed-edge MoS2 allows intercalation of small alkali metal ions (e.g., Li+ and Na+) and rejects large ions (e.g., K+). These findings imply potential applications in developing functional 2D-material-based devices with high tunability and ion selectivity.
View details for PubMedID 30538249
- Fundamental study on the wetting property of liquid lithium ENERGY STORAGE MATERIALS 2018; 14: 345–50
Spectrally Selective Nanocomposite Textile for Outdoor Personal Cooling.
Advanced materials (Deerfield Beach, Fla.)
Outdoor heat stress poses a serious public health threat and curtails industrial labor supply and productivity, thus adversely impacting the wellness and economy of the entire society. With climate change, there will be more intense and frequent heat waves that further present a grand challenge for sustainability. However, an efficient and economical method that can provide localized outdoor cooling of the human body without intensive energy input is lacking. Here, a novel spectrally selective nanocomposite textile for radiative outdoor cooling using zinc oxide nanoparticle-embedded polyethylene is demonstrated. By reflecting more than 90% solar irradiance and selectively transmitting out human body thermal radiation, this textile can enable simulated skin to avoid overheating by 5-13 °C compared to normal textile like cotton under peak daylight condition. Owing to its superior passive cooling capability and compatibility with large-scale production, this radiative outdoor cooling textile is promising to widely benefit the sustainability of society in many aspects spanning from health to economy.
View details for PubMedID 30015999
Spatially controlled doping of two-dimensional SnS2 through intercalation for electronics
2018; 13 (4): 294-+
Doped semiconductors are the most important building elements for modern electronic devices 1 . In silicon-based integrated circuits, facile and controllable fabrication and integration of these materials can be realized without introducing a high-resistance interface2,3. Besides, the emergence of two-dimensional (2D) materials enables the realization of atomically thin integrated circuits4-9. However, the 2D nature of these materials precludes the use of traditional ion implantation techniques for carrier doping and further hinders device development 10 . Here, we demonstrate a solvent-based intercalation method to achieve p-type, n-type and degenerately doped semiconductors in the same parent material at the atomically thin limit. In contrast to naturally grown n-type S-vacancy SnS2, Cu intercalated bilayer SnS2 obtained by this technique displays a hole field-effect mobility of ~40 cm2 V-1 s-1, and the obtained Co-SnS2 exhibits a metal-like behaviour with sheet resistance comparable to that of few-layer graphene 5 . Combining this intercalation technique with lithography, an atomically seamless p-n-metal junction could be further realized with precise size and spatial control, which makes in-plane heterostructures practically applicable for integrated devices and other 2D materials. Therefore, the presented intercalation method can open a new avenue connecting the previously disparate worlds of integrated circuits and atomically thin materials.
View details for PubMedID 29483599
Correlating Nanoscopic Energy Transfer and Far-Field Emission to Unravel Lasing Dynamics in Plasmonic Nanocavity Arrays
2018; 18 (2): 1454–59
Excited-state interactions between nanoscale cavities and photoactive molecules are critical in plasmonic nanolasing, although the underlying details are less-resolved. This paper reports direct visualization of the energy-transfer dynamics between two-dimensional arrays of plasmonic gold bowtie nanocavities and dye molecules. Transient absorption microscopy measurements of single bowties within the array surrounded by gain molecules showed fast excited-state quenching (2.6 ± 1 ps) characteristic of individual nanocavities. Upon optical pumping at powers above threshold, lasing action emerged depending on the spacing of the array. By correlating ultrafast microscopy and far-field light emission characteristics, we found that bowtie nanoparticles acted as isolated cavities when the diffractive modes of the array did not couple to the plasmonic gap mode. These results demonstrate how ultrafast microscopy can provide insight into energy relaxation pathways and, specifically, how nanocavities in arrays can show single-unit nanolaser properties.
View details for DOI 10.1021/acs.nanolett.7b05223
View details for Web of Science ID 000425559700116
View details for PubMedID 29369639
In Situ Investigation on the Nanoscale Capture and Evolution of Aerosols on Nanofibers
2018; 18 (2): 1130–38
Aerosol-induced haze problem has become a serious environmental concern. Filtration is widely applied to remove aerosols from gas streams. Despite classical filtration theories, the nanoscale capture and evolution of aerosols is not yet clearly understood. Here we report an in situ investigation on the nanoscale capture and evolution of aerosols on polyimide nanofibers. We discovered different capture and evolution behaviors among three types of aerosols: wetting liquid droplets, nonwetting liquid droplets, and solid particles. The wetting droplets had small contact angles and could move, coalesce, and form axisymmetric conformations on polyimide nanofibers. In contrast, the nonwetting droplets had a large contact angle on polyimide nanofibers and formed nonaxisymmetric conformations. Different from the liquid droplets, the solid particles could not move along the nanofibers and formed dendritic structures. This study provides an important insight for obtaining a deep understanding of the nanoscale capture and evolution of aerosols and benefits future design and development of advanced filters.
View details for PubMedID 29297691
Millimeter-Scale Spatial Coherence from a Plasmon Laser
2017; 17 (11): 6690–95
Coherent light sources have been demonstrated based on a wide range of nanostructures, however, little effort has been devoted to probing their underlying coherence properties. Here, we report long-range spatial coherence of lattice plasmon lasers constructed from a periodic array of gold nanoparticles and a liquid gain medium at room temperature. By combining spatial and temporal interferometry, we demonstrate millimeter-scale (∼1 mm) spatial coherence and picosecond (∼2 ps) temporal coherence. The long-range spatial coherence occurs even without the presence of strong coupling with the lattice plasmon mode extending over macroscopic distances in the lasing regime. This plasmonic lasing system thus provides a platform for understanding the emergence of long-range coherence from collections of nanoscale resonators and points toward novel types of distributed lasing sources.
View details for DOI 10.1021/acs.nanolett.7b02677
View details for Web of Science ID 000415029000028
View details for PubMedID 28956442
Warming up human body by nanoporous metallized polyethylene textile
2017; 8: 496
Space heating accounts for the largest energy end-use of buildings that imposes significant burden on the society. The energy wasted for heating the empty space of the entire building can be saved by passively heating the immediate environment around the human body. Here, we demonstrate a nanophotonic structure textile with tailored infrared (IR) property for passive personal heating using nanoporous metallized polyethylene. By constructing an IR-reflective layer on an IR-transparent layer with embedded nanopores, the nanoporous metallized polyethylene textile achieves a minimal IR emissivity (10.1%) on the outer surface that effectively suppresses heat radiation loss without sacrificing wearing comfort. This enables 7.1 °C decrease of the set-point compared to normal textile, greatly outperforming other radiative heating textiles by more than 3 °C. This large set-point expansion can save more than 35% of building heating energy in a cost-effective way, and ultimately contribute to the relief of global energy and climate issues.Energy wasted for heating the empty space of the entire building can be saved by passively heating the immediate environment around the human body. Here, the authors show a nanophotonic structure textile with tailored infrared property for passive personal heating using nanoporous metallized polyethylene.
View details for PubMedID 28928427
Band-edge engineering for controlled multi-modal nanolasing in plasmonic superlattices
2017; 12 (9): 889-+
Single band-edge states can trap light and function as high-quality optical feedback for microscale lasers and nanolasers. However, access to more than a single band-edge mode for nanolasing has not been possible because of limited cavity designs. Here, we describe how plasmonic superlattices-finite-arrays of nanoparticles (patches) grouped into microscale arrays-can support multiple band-edge modes capable of multi-modal nanolasing at programmed emission wavelengths and with large mode spacings. Different lasing modes show distinct input-output light behaviour and decay dynamics that can be tailored by nanoparticle size. By modelling the superlattice nanolasers with a four-level gain system and a time-domain approach, we reveal that the accumulation of population inversion at plasmonic hot spots can be spatially modulated by the diffractive coupling order of the patches. Moreover, we show that symmetry-broken superlattices can sustain switchable nanolasing between a single mode and multiple modes.
View details for DOI 10.1038/NNANO.2017.126
View details for Web of Science ID 000409361800015
View details for PubMedID 28692060
Thermal Management in Nanofiber-Based Face Mask
2017; 17 (6): 3506–10
Face masks are widely used to filter airborne pollutants, especially when particulate matter (PM) pollution has become a serious concern to public health. Here, the concept of thermal management is introduced into face masks for the first time to enhance the thermal comfort of the user. A system of nanofiber on nanoporous polyethylene (fiber/nanoPE) is developed where the nanofibers with strong PM adhesion ensure high PM capture efficiency (99.6% for PM2.5) with low pressure drop and the nanoPE substrate with high-infrared (IR) transparency (92.1%, weighted based on human body radiation) results in effective radiative cooling. We further demonstrate that by coating nanoPE with a layer of Ag, the fiber/Ag/nanoPE mask shows a high IR reflectance (87.0%) and can be used for warming purposes. These multifunctional face mask designs can be explored for both outdoor and indoor applications to protect people from PM pollutants and simultaneously achieve personal thermal comfort.
View details for DOI 10.1021/acs.nanolett.7b00579
View details for Web of Science ID 000403631600028
View details for PubMedID 28505460
Deterministic Coupling of Quantum Emitters in 2D Materials to Plasmonic Nanocavity Arrays
2017; 17 (4): 2634–39
Quantum emitters in two-dimensional materials are promising candidates for studies of light-matter interaction and next generation, integrated on-chip quantum nanophotonics. However, the realization of integrated nanophotonic systems requires the coupling of emitters to optical cavities and resonators. In this work, we demonstrate hybrid systems in which quantum emitters in 2D hexagonal boron nitride (hBN) are deterministically coupled to high-quality plasmonic nanocavity arrays. The plasmonic nanoparticle arrays offer a high-quality, low-loss cavity in the same spectral range as the quantum emitters in hBN. The coupled emitters exhibit enhanced emission rates and reduced fluorescence lifetimes, consistent with Purcell enhancement in the weak coupling regime. Our results provide the foundation for a versatile approach for achieving scalable, integrated hybrid systems based on low-loss plasmonic nanoparticle arrays and 2D materials.
View details for DOI 10.1021/acs.nanolett.7b00444
View details for Web of Science ID 000399354500076
View details for PubMedID 28318263
Coherent Light Sources at the Nanoscale
ANNUAL REVIEW OF PHYSICAL CHEMISTRY, VOL 68
2017; 68: 83–99
This review focuses on coherent light sources at the nanoscale, and specifically on lasers exploiting plasmonic cavities that can beat the diffraction limit of light. Conventional lasers exhibit coherent, intense, and directional emission with cavity sizes much larger than their operating wavelength. Plasmon lasers show ultrasmall mode confinement, support strong light-matter interactions, and represent a class of devices with extremely small sizes. We discuss the differences between plasmon lasers and traditional ones, and we highlight advances in directionality and tunability through innovative cavity designs and new materials. Challenges and future prospects are also discussed.
View details for DOI 10.1146/annurev-physchem-052516-050730
View details for Web of Science ID 000401335600005
View details for PubMedID 28142312
Programmable and reversible plasmon mode engineering
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2016; 113 (50): 14201–6
Plasmonic nanostructures with enhanced localized optical fields as well as narrow linewidths have driven advances in numerous applications. However, the active engineering of ultranarrow resonances across the visible regime-and within a single system-has not yet been demonstrated. This paper describes how aluminum nanoparticle arrays embedded in an elastomeric slab may exhibit high-quality resonances with linewidths as narrow as 3 nm at wavelengths not accessible by conventional plasmonic materials. We exploited stretching to improve and tune simultaneously the optical response of as-fabricated nanoparticle arrays by shifting the diffraction mode relative to single-particle dipolar or quadrupolar resonances. This dynamic modulation of particle-particle spacing enabled either dipolar or quadrupolar lattice modes to be selectively accessed and individually optimized. Programmable plasmon modes offer a robust way to achieve real-time tunable materials for plasmon-enhanced molecular sensing and plasmonic nanolasers and opens new possibilities for integrating with flexible electronics.
View details for DOI 10.1073/pnas.1615281113
View details for Web of Science ID 000389696700035
View details for PubMedID 27911819
View details for PubMedCentralID PMC5167184
Unidirectional Lasing from Template-Stripped Two-Dimensional Plasmonic Crystals
2015; 9 (12): 11582–88
Plasmon lasers support cavity structures with sizes below that of the diffraction limit. However, most plasmon-based lasers show bidirectional lasing emission or emission with limited far-field directionality and large radiative losses. Here, we report unidirectional lasing from ultrasmooth, template-stripped two-dimensional (2D) plasmonic crystals. Optically pumped 2D plasmonic crystals (Au or Ag) surrounded by dye molecules exhibited lasing in a single emission direction and their lasing wavelength could be tuned by modulating the dielectric environment. We found that 2D plasmonic crystals were an ideal architecture to screen how nanocavity unit-cell structure, metal material, and gain media affected the lasing response. We discovered that template-stripped strong plasmonic materials with cylindrical posts were an optimal cavity design for a unidirectional laser operating at room temperature.
View details for DOI 10.1021/acsnano.5b05419
View details for Web of Science ID 000367280100008
View details for PubMedID 26456299
- Superlattice Plasmons in Hierarchical Au Nanoparticle Arrays ACS PHOTONICS 2015; 2 (12): 1789–94
- Breakthroughs in Photonics 2014: Advances in Plasmonic Nanolasers IEEE PHOTONICS JOURNAL 2015; 7 (3)
Real-time tunable lasing from plasmonic nanocavity arrays
2015; 6: 6939
Plasmon lasers can support ultrasmall mode confinement and ultrafast dynamics with device feature sizes below the diffraction limit. However, most plasmon-based nanolasers rely on solid gain materials (inorganic semiconducting nanowire or organic dye in a solid matrix) that preclude the possibility of dynamic tuning. Here we report an approach to achieve real-time, tunable lattice plasmon lasing based on arrays of gold nanoparticles and liquid gain materials. Optically pumped arrays of gold nanoparticles surrounded by liquid dye molecules exhibit lasing emission that can be tuned as a function of the dielectric environment. Wavelength-dependent time-resolved experiments show distinct lifetime characteristics below and above the lasing threshold. By integrating gold nanoparticle arrays within microfluidic channels and flowing in liquid gain materials with different refractive indices, we achieve dynamic tuning of the plasmon lasing wavelength. Tunable lattice plasmon lasers offer prospects to enhance and detect weak physical and chemical processes on the nanoscale in real time.
View details for DOI 10.1038/ncomms7939
View details for Web of Science ID 000353704500002
View details for PubMedID 25891212
View details for PubMedCentralID PMC4411284
Hetero-oligomer Nanoparticle Arrays for Plasmon-Enhanced Hydrogen Sensing
2014; 8 (8): 7639–47
This paper describes how the ability to tune each nanoparticle in a plasmonic hetero-oligomer can optimize architectures for plasmon-enhanced applications. We demonstrate how a large-area nanofabrication approach, reconstructable mask lithography (RML), can achieve independent control over the size, position, and material of up to four nanoparticles within a subwavelength unit. We show how arrays of plasmonic hetero-oligomers consisting of strong plasmonic materials (Au) and reactant-specific elements (Pd) provide a unique platform for enhanced hydrogen gas sensing. Using finite-difference time-domain simulations, we modeled different configurations of Au–Pd hetero-oligomers and compared their hydrogen gas sensing capabilities. In agreement with calculations, we found that Au–Pd nanoparticle dimers showed a red-shift and that Au–Pd trimers with touching Au and Pd nanoparticles showed a blue-shift upon exposure to both high and low concentrations of hydrogen gas. Both Au–Pd hetero-oligomer sensors displayed high sensitivity, fast response times, and excellent recovery.
View details for DOI 10.1021/nn502502r
View details for Web of Science ID 000340992300008
View details for PubMedID 24956125