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Huang, Yun

Publications and source records attributed to Huang, Yun.

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Near-Field Nanoimaging of Colloidal Transition Metal Dichalcogenide Waveguides

Bulk transition metal dichalcogenide (TMDC) nanostructures are regarded as promising material candidates for integrated photonics due to their high refractive index at the near-infrared wavelengths. Here in this work, colloidal TMDC waveguides with tailorable dimensions are prepared by a scalable synthetic approach. The optical waveguiding properties of colloidal nanowires are studied by the near-field nanoimaging technique. In addition to dependence on thickness and wavelength, the excitonic responses and resultant waveguide modes in TMDC nanowires can be modulated by the environmental temperature. With the high-throughput production and tunable optical properties, colloidal TMDC nanowires highlight the potential for active optical components and integrated photonic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Construction of extracellular matrix-based 3D hydrogel and its effects on cardiomyocytes

Highlights: • SOD and Triton X-100 could efficiently decellularize cells to get cardiac ECM. • Main proteins of cECM were fibronectin, collagen, elastin, fibrillin, laminin, etc. • 75% cECM-containing 3D hydrogel promoted cell proliferation and anti-apoptosis. • cECM3DH facilitated the differentiation of ESCs into CMs. • APcECM3DH was more conducive to NCM and ESC-derived CM maturation. Some discoveries resulted from 2-dimensional (2D) cultured cardiac cells have been disqualified in animal testing and later clinical trials. Extracellular matrix (ECM) plays a vital role in cardiac homeostasis, cardiac ECM (cECM)-based 3D cell cultures can mimics the physiological and pathological conditions in vivo closely, it is hopeful of addressing this challenge. Construction of cECM-based 3-dimensional (3D) hydrogel (cECM3DH) and its effects on cell behaviors were studied here. The results indicated that cellular compartments could be efficiently removed from heart tissue via sodium dodecyl sulfonate (SDS)- and Triton X-100-mediated decellularization, remaining the natural fibrous network structure and major proteins. 3D hydrogel consisted of 1 × 10{sup 7} cells/mL cells and 75% cECM could promote the proliferation and anti-apoptosis ability of human embryonic kidney (HEK)-293T cells. 0.25% trypsin or 0.20% collagenase was suitable to retrieve these cells from 3D hydrogel for further researches. Compared with 2D culture system, cECM3DH could significantly increase the proportion of GATA 4{sup +} cardiomyocytes (CMs) derived from heart tissue of neonatal mouse or induced differentiation of embryonic stem cells (ESCs) (P < 0.05) The expression levels of mature genes including cTnT, JCN, CaV1.2, MYL2, CASQ2, NCX1, and Cx43 of these CMs in adult pig cECM-based 3D hydrogel (APcECM3DH) were significantly higher than that in 2D culture system and in newborn piglet cECM-based 3D hydrogel (NPcECM3DH), respectively (P < 0.05). Therefore, cECM3DH supports the generation of primary CMs and ESC-derived CMs, APcECM3DH was more conducive to promoting CM maturation, which contributes to building 3D model for pathogenesis exploration, drug screening, and regenerative medicine of heart diseases.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Self-supported MoO 2 /MoS 2 nano-sheets embedded in a carbon cloth as a binder-free substrate for high-energy lithium–sulfur batteries

As one of the most prospective candidates for next-generation rechargeable batteries, lithium-sulfur (Li-S) batteries currently still encounter great challenges associated with the low conductivity, severe shuttle effects, and sluggish redox kinetics. Herein, a self-supported sulfur host is fabricated by an in-situ growth of MoO 2 /MoS 2 nano-sheets on a carbon cloth (CC). First, carbon cloth serves as a good template for the morphology-controlled synthesis of nanostructured materials, which not only alleviates the agglomeration of MoO2/MoS2, but also enhances the flexibility and mechanical strengthen of the hybrid architecture as a free-standing host. Second, the polysulfide-trapping ability can be greatly enhanced by both physical and chemical adsorption from the MoO 2 /MoS 2 -anchored carbon cloth. Moreover, the partially sulfurized MoO 2 /MoS 2 nano-sheets integrate the benefits of conductive MoO 2 and sulfiphilic MoS 2 , thus facilitating fast charge transfer and redox kinetics of polysulfide conversion. As a result, these attributes enable the host to hold a high sulfur loading (up to 7.6 mg cm -2 ), which exceeds most of the reported carbon cloth-related cathode work in the literature. Furthermore, the Li-S cells can achieve a high peak capacity of 1350 mA h g -1 , excellent rate capability (C/20 - 2C rate), impressive areal capacity (up to 6.3 mA h cm -2 ), and a high capacity retention of 85% after 100 cycles.

25 ENERGY STORAGE↗
DOE OSTI2019

A functional SrF 2 coated separator enabling a robust and dendrite-free solid electrolyte interphase on a lithium metal anode

An unstable solid electrolyte interphase (SEI) and accompanying Li metal dendrites are the key impediments to commercialization of high-energy lithium metal batteries (LMBs). We employ a strontium fluoride (SrF 2 ) microsphere coated polypropylene (PP) separator to stabilize the SEI and to prevent dendrites from growing. This approach is tested with Li∥Cu half-cells, Li∥Li symmetrical cells, and Li∥NMC full LMBs, there being a major improvement in each case. The Li∥Cu cell with SrF 2 maintains a stable coulombic efficiency (CE) of 80% after 100 cycles, when tested at 0.25 mA cm -2 to a capacity of 0.5 mA h cm -2 . By comparison, the uncoated PP reference has a CE of 10% in cycle 60. The Li∥Li cell with SrF 2 exhibits a markedly smaller voltage polarization and is able to stably cycle for approximately 340 h vs. the reference which begins to display severe voltage instability at 200 h. The Li∥NMC full LMB with SrF 2 shows an initial discharge capacity of 173 mA h g -1 , with 167 mA h g -1 (96.5%) being retained after 200 cycles at 200 mA g -1 (1C rate). The SrF 2 containing LMB also has a substantially improved rate capability over the reference, the difference being drastic even at the highest testing rate of 20C. First-principles calculations based on DFT indicate that lithium ions prefer to adsorb onto the SrF 2 surface, which should create a more uniform ion flux and reduce the propensity for dendrite nucleation. Finally in parallel, the SrF 2 spheres bind with the SEI layer, creating a tough in situ formed composite membrane that mechanically stabilizes a planar metal interface.

25 ENERGY STORAGE↗
DOE OSTI2019

Xyloglucan Endotransglucosylase-Hydrolase30 negatively affects salt tolerance in Arabidopsis

Plants have evolved various strategies to sense and respond to saline environments that severely reduce plant growth and limit agricultural productivity. Alteration to the cell wall is one strategy that helps plants adapt to salt stress. However, we do not fully understand the physiological significance of how cell wall components respond to salt stress. Here, we show that expression of XTH30, encoding a xyloglucan endotransglucosylase/hydrolase, is strongly up-regulated in response to salt stress in Arabidopsis thaliana. Loss-of-function in XTH30 leads to increased salt tolerance and overexpression of XTH30 results in salt hypersensitivity. XTH30 is located in the plasma membrane and highly expressed in the root, flower, stem, and etiolated hypocotyl. The NaCl-induced increase in XLFG (xyloglucan-derived (XyG) oligosaccharide) of the wild type is partly blocked in xth30 mutants. Loss-of-function in XTH30 slows down the decrease of crystalline cellulose content and the depolymerization of microtubules caused by salt stress. Moreover, less Na+ accumulation in shoot and H 2 O 2 content are found in xth30 mutants in response to salt stress. Taken together, these results indicate that XTH30 modulates XyG side chains with altered abundance of XLFG, the cellulose synthesis and cortical microtubule stability, and then negatively affects salt tolerance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Structural basis for preferential binding of human TCF4 to DNA containing 5-carboxylcytosine

The psychiatric risk-associated transcription factor 4 (TCF4) is linked to schizophrenia. Rare TCF4 coding variants are found in individuals with Pitt-Hopkins syndrome—an intellectual disability and autism spectrum disorder. TCF4 contains a C-terminal basic-helix-loop-helix (bHLH) DNA binding domain which recognizes the enhancer-box (E-box) element 5'-CANNTG-3' (where N = any nucleotide). A subset of the TCF4-occupancy sites have the expanded consensus binding specificity 5'-C(A/G)-CANNTG-3', with an added outer Cp(A/G) dinucleotide; for example in the promoter for CNIH3, a gene involved in opioid dependence. In mammalian genomes, particularly brain, the CpG and CpA dinucleotides can be methylated at the 5-position of cytosine (5mC), and then may undergo successive oxidations to the 5-hydroxymethyl (5hmC), 5-formyl (5fC), and 5-carboxyl (5caC) forms. We find that, in the context of 5'- 0 CG- 1 CA- 2 CG- 3 TG-3'(where the numbers indicate successive dinucleotides), modification of the central E-box 2 CG has very little effect on TCF4 binding, E-box 1 CA modification has a negative influence on binding, while modification of the flanking 0 CG, particularly carboxylation, has a strong positive impact on TCF4 binding to DNA. Crystallization of TCF4 in complex with unmodified or 5caC-modified oligonucleotides revealed that the basic region of bHLH domain adopts multiple conformations, including an extended loop going through the DNA minor groove, or the N-terminal portion of a long helix binding in the DNA major groove. The different protein conformations enable arginine 576 (R576) to interact, respectively, with a thymine in the minor groove, a phosphate group of DNA backbone, or 5caC in the major groove. The Pitt-Hopkins syndrome mutations affect five arginine residues in the basic region, two of them (R569 and R576) involved in 5caC recognition. Our analyses indicate, and suggest a structural basis for, the preferential recognition of 5caC by a transcription factor centrally important in brain development.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Facile electrostatic self-assembly of silicon/reduced graphene oxide porous composite by silica assist as high performance anode for Li-ion battery

Silicon(Si)/graphene composite has been regarded as one of the most promising candidates for next generation anode materials with high power and energy density in lithium ion batteries. Introduction of graphene in Si anodes could improve the electronic conductivity, suppress the severe volume expansion of Si, and facilitate the formation of stable solid electrolyte interphase, etc. However, traditionally mechanical mixing of Si and graphene cannot realize uniform distribution of Si particles on the graphene sheets, which would largely weaken the effectiveness of the graphene in the composite. In this work, nano-Si/reduced graphene oxide porous composite (p Si/rGO) has been fabricated by a facile electrostatic self-assembly approach via using SiO2 as the sacrificial template. Compared with the simply mechanically mixed nano-Si and rGO (Si/rGO), the nano-Si particles could be more uniformly dispersed among the rGO sheets in the p Si/rGO, which significantly increases its electronic conductivity. Moreover, the drastic volume expansion of nano-Si during repeated lithiation/delithiation cycles also has been effectively accommodated by the large number of pores left after removing the SiO2 template in the composite. Thus, the p Si/rGO presented largely enhanced electrochemical performances, showing a high reversible capacity up to 1849?mA?h?g-1 at 0.2?A?g-1 with good capacity retention, and high rate capability (535?mA?h?g-1 at 2?A?g-1).

Silicon, Reduced graphene oxide, Electrostatic sel↗
DOE OSTI2018

Li-rich Li[Li1/6Fe1/6Ni1/6Mn1/2]O2 (LFNMO) Cathodes: Atomic Scale Insight on the Mechanisms of Cycling Decay and of the Improvement due to Cobalt Phosphate Surface Modification

Lithium-rich Li[Li1/6Fe1/6Ni1/6Mn1/2]O2(0.4Li2MnO3-0.6LiFe1/3Ni1/3Mn1/3O2, LFNMO) is a new member of the xLi2MnO3·(1-x)LiMO2 family of high capacity - high voltage LIB cathodes. Unfortunately, it suffers from the severe degradation during cycling both in terms of reversible capacity and operating voltage. We are the first to document the corresponding degradation occurring in LFNMO at an atomic scale using aberration- corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) , as well as tracing the elemental crossover to the Li metal anode using XPS. We also demonstrate that a phosphate coating significantly boosts LFNMO cycling stability and rate capability. Due to cycling, the unmodified LFNMO undergoes extensive elemental dissolution (especially Mn) and O loss, forming Kirkendall-type voids. The associated structural degradation is from the as-synthesized R-3m layered structure to a disordered rock-salt phase. Prior to cycling, the phosphate coating shares the crystallography of the parent material. During cycling, a 2-3 nm thick disordered Co-based rock-salt structure is formed on the Mod-LFNMO surface, while the bulk material retains R-3m crystallography. Electrochemical impedance spectroscopy (EIS) analysis highlights how the phosphide treatment stabilizes the charge transfer resistance (RCT), the CEI resistance (RCEI), and the lithium ion diffusion coefficient (DLi). XPS analysis demonstrates that the coating also reduces the amount of cross-over Mn, Fe and especially Ni deposited on the Li metal anode, which is expected to lead to a more stable SEI layer during cycling. These combined cathode - anode findings significantly advance the microstructural design principles for next generation Li-rich cathode materials and coatings.

: high voltage cathode, Li - and Mn - rich cathode↗