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Zhang, Zhuolei

Publications and source records attributed to Zhang, Zhuolei.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

One Pot Synthesis of Cyan Emitting CdZnSSe Quantum Dots for Human Centric Lighting

A one pot synthesis of blue and green emissive CdZnSSe quantum dots (QDs) from thio- and selenoureas and Cd and Zn carboxylates is optimized using high throughput robotic optimization. A large set of spectral data (N = 192) is used to train machine learning models that accurately predict the photoluminescence emission wavelength (λmax) and full-width half-maximum, and the relative photoluminescence quantum yield (PLQY) from the S:Se and Zn:Cd stoichiometries and reaction time. ZnS shells are deposited on the crude QD heterostructures using 4-tert-butylbenzyl mercaptan, a more reactive source of sulfide that enables shell growth below the temperature where ion diffusion in the QD can broaden its optical spectrum (≤275 °C). These optimized procedures provide gram quantities of blue-green emitting QDs (PLQY = 85–99%) in a single reaction vessel. A solid state lighting device (4260 K) that incorporates cyan emissive QDs achieved a higher luminous efficacy of 179 lm/W and melanopic daylight efficiency ratio (0.71) than existing commercial human centric lighting devices.

Jordan, Abraham J↗
DOE OSTI2022

Tuning Phonon Energies in Lanthanide‐doped Potassium Lead Halide Nanocrystals for Enhanced Nonlinearity and Upconversion

Abstract Optical applications of lanthanide‐doped nanoparticles require materials with low phonon energies to minimize nonradiative relaxation and promote nonlinear processes like upconversion. Heavy halide hosts offer low phonon energies but are challenging to synthesize as nanocrystals. Here, we demonstrate the size‐controlled synthesis of low‐phonon‐energy KPb 2 X 5 (X=Cl, Br) nanoparticles and the ability to tune nanocrystal phonon energies as low as 128 cm −1 . KPb 2 Cl 5 nanoparticles are moisture resistant and can be efficiently doped with lighter lanthanides. The low phonon energies of KPb 2 X 5 nanoparticles promote upconversion luminescence from higher lanthanide excited states and enable highly nonlinear, avalanche‐like emission from KPb 2 Cl 5 : Nd 3+ nanoparticles. The realization of nanoparticles with tunable, ultra‐low phonon energies facilitates the discovery of nanomaterials with phonon‐dependent properties, precisely engineered for applications in nanoscale imaging, sensing, luminescence thermometry and energy conversion.

Zhang, Zhuolei↗
DOE OSTI2022

Tuning Phonon Energies in Lanthanide-doped Potassium Lead Halide Nanocrystals for Enhanced Nonlinearity and Upconversion

Optical applications of lanthanide-doped nanoparticles require materials with low phonon energies to minimize nonradiative relaxation and promote nonlinear processes like upconversion. Heavy halide hosts offer low phonon energies but are challenging to synthesize as nanocrystals. Here, we demonstrate the size-controlled synthesis of low-phonon-energy KPb 2 X 5 (X=Cl, Br) nanoparticles and the ability to tune nanocrystal phonon energies as low as 128 cm -1 . KPb 2 Cl 5 nanoparticles are moisture resistant and can be efficiently doped with lighter lanthanides. Further, the low phonon energies of KPb 2 X 5 nanoparticles promote upconversion luminescence from higher lanthanide excited states and enable highly nonlinear, avalanche-like emission from KPb 2 Cl 5 : Nd 3+ nanoparticles. The realization of nanoparticles with tunable, ultra-low phonon energies facilitates the discovery of nanomaterials with phonon-dependent properties, precisely engineered for applications in nanoscale imaging, sensing, luminescence thermometry and energy conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Hydrogen Storage Performance of Preferentially Oriented Mg/rGO Hybrids

Chemical interactions on the surface of a functional nanoparticle are closely related to its crystal facets, which can regulate the corresponding energy storage properties like hydrogen absorption. In this study, we reported a one-step growth of magnesium (Mg) particles with both close- and nonclose-packed facets, that is, {0001} and {$2\overline{116}$} planes, on atomically thin reduced graphene oxide (rGO). The detailed microstructures of Mg/rGO hybrids were revealed by X-ray diffraction, selected-area electron diffraction, high-resolution transmission electron microscopy, and fast Fourier transform analysis. Hydrogen storage performance of Mg/rGO hybrids with different orientations varies: Mg with preferential high-index {$2\overline{116}$} crystal surface shows remarkably increased hydrogen absorption up to 6.2 wt % compared with the system exposing no preferentially oriented crystal surfaces showing inferior performance of 5.1 wt % within the first 2 h. First-principles calculations revealed improved hydrogen sorption properties on the {$2\overline{116}$} surface with a lower hydrogen dissociation energy barrier and higher stability of hydrogen atoms than those on the {0001} basal plane, supporting the hydrogen uptake experiment. In addition, the hydrogen penetration energy barrier is found to be much lower than that of {0001} because of low surface atom packing density, which might be the most critical process to the hydrogenation kinetics. Here, the experimental and calculation results present a new handle for regulating the hydrogen storage of metal hydrides by controlled Mg facets.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Development and Prospects of Halide Perovskite Single Crystal Films

Halide perovskite single crystal (HPSC) films have demonstrated extraordinary performance in solar cells, photodetectors, and lighting applications, owing to the high carrier mobility, long carrier diffusion length, tunable bandgap, and large light absorption coefficients of these materials. Here, the recent development of the major HPSC thin films is reviewed systematically, including MAPbI 3 , α-FAPbI 3 , MAPbBr 3 , CsPbBr 3 , with special emphasis on different classes of fabrication methods and thin-film characteristics. So finally, the conclusion and prospects in this field are discussed in detail. It is anticipated that the HPSC thin films will lead to a compelling future for the rising electronic applications.

MAPbI3↗
DOE OSTI2020

Enhanced and stabilized hydrogen production from methanol by ultrasmall Ni nanoclusters immobilized on defect-rich h-BN nanosheets

Employing liquid organic hydrogen carriers (LOHCs) to transport hydrogen to where it can be utilized relies on methods of efficient chemical dehydrogenation to access this fuel. Therefore, developing effective strategies to optimize the catalytic performance of cheap transition metal-based catalysts in terms of activity and stability for dehydrogenation of LOHCs is a critical challenge. Here, we report the design and synthesis of ultrasmall nickel nanoclusters (∼1.5 nm) deposited on defect-rich boron nitride (BN) nanosheet (Ni/BN) catalysts with higher methanol dehydrogenation activity and selectivity, and greater stability than that of some other transition-metal based catalysts. The interface of the two-dimensional (2D) BN with the metal nanoparticles plays a strong role both in guiding the nucleation and growth of the catalytically active ultrasmall Ni nanoclusters, and further in stabilizing these nanoscale Ni catalysts against poisoning by interactions with the BN substrate. We provide detailed spectroscopy characterizations and density functional theory (DFT) calculations to reveal the origin of the high productivity, high selectivity, and high durability exhibited with the Ni/BN nanocatalyst and elucidate its correlation with nanocluster size and support–nanocluster interactions. This study provides insight into the role that the support material can have both regarding the size control of nanoclusters through immobilization during the nanocluster formation and also during the active catalytic process; this twofold set of insights is significant in advancing the understanding the bottom-up design of high-performance, durable catalytic systems for various catalysis needs.

08 HYDROGEN↗