Ningxin Jiang

The stability of platinum-based alloy catalysts is crucial for the future development of proton exchange membrane fuel cells, considering the potential dissolution of transition metals under complex operating conditions. Here, we report on a Rh-doped Pt3Co alloy that exhibits strong interatomic interactions, thereby enhancing the durability of fuel cells. The Rh-Pt3Co/C catalyst demonstrates exceptional catalytic activity for oxygen reduction reactions (ORR) (1.31 A mgPt-1 at 0.9 V vs. the reversible hydrogen electrode (RHE) and maintaining 92% of its mass activity after 170,000 potential cycles). Long-term testing has shown direct inhibition of Co dissolution in Rh-Pt3Co/C. Furthermore, tests on proton exchange membrane fuel cells (PEMFC) have shown excellent performance and long-term durability with low Pt loading. After 50,000 cycles, there was no voltage loss at 0.8 A cm-2 for Rh-Pt3Co/C, while Pt3Co/C experienced a loss of 200 mV. Theoretical calculations suggest that introducing transition metal atoms through doping creates a stronger compressive strain, which in turn leads to increased catalytic activity. Additionally, Rh doping increases the energy barrier for Co diffusion in the bulk phase, while also raising the vacancy formation energy of the surface Pt. This ensures the long-term stability of the alloy over the course of the cycle.

Photochemistry: A direct and mild photochemical synthesis of lactones, cyclopropanes and ATRA products, utilizing sodium ascorbate or ascorbic acid as the halogen/hydrogen bonding mediator and irradiation at 370 nm, 390 nm or 427 nm LED as the irradiation source. A variety of iodo-reagents were activated via halogen or hydrogen bonding and reacted successfully with a number of alkenes without the use of an external photocatalyst, leading to products in good to excellent yields (up to 95 % yield).

Abstract

Light-mediated processes have received significant attention, since they have re-surfaced unconventional reactivity platforms, complementary to conventional polar chemistry. γ-Lactones and cyclopropanes are prevalent moieties, found in numerous natural products and pharmaceuticals. Among various methods for their synthesis, light-mediated protocols are coming to the spotlight, although these are contingent upon the use of photoorgano- or metal-based catalysts. Herein, we introduce a novel photochemical activation of iodo-reagents via the use of cheap sodium ascorbate or ascorbic acid to enable their homolytic scission and addition onto double bonds. The developed protocol was applied successfully to the formal [3+2] cycloaddition for the synthesis of γ-lactones, traditional atom transfer radical addition (ATRA) reactions and the one-pot two-step conversion of alkenes to cyclopropanes. In all cases, the desired products were obtained in good to high yields, while the reaction mechanism was thoroughly investigated. Depending on the nature of the iodo-reagent, a halogen or a hydrogen-bonded complex is formed, which initiates the process.

Short-wave infrared (SWIR) photoluminescence lifetime imaging microscopy using an all-optical streak camera (PLIMASC) reaches a 1D imaging speed of up to 138.9 kHz in the 900–1700 nm spectral range. SWIR-PLIMASC is implemented to map lifetimes of downshifting emission by rare-earth doped nanoparticles with applications in anti-counterfeiting and thermometry.

Abstract

The short-wave infrared (SWIR) photoluminescence lifetimes of rare-earth doped nanoparticles (RENPs) have found diverse applications in fundamental and applied research. Despite dazzling progress in the novel design and synthesis of RENPs with attractive optical properties, existing optical systems for SWIR photoluminescence lifetime imaging are still considerably restricted by inefficient photon detection, limited imaging speed, and low sensitivity. To overcome these challenges, SWIR photoluminescence lifetime imaging microscopy using an all-optical streak camera (PLIMASC) is developed. Synergizing scanning optics and a high-sensitivity InGaAs CMOS camera, SWIR-PLIMASC has a 1D imaging speed of up to 138.9 kHz in the spectral range of 900–1700 nm, which quantifies the photoluminescence lifetime of RENPs in a single shot. A 2D photoluminescence lifetime map can be acquired by 1D scanning of the sample. To showcase the power of SWIR-PLIMASC, a series of core-shell RENPs with distinct SWIR photoluminescence lifetimes is synthesized. In particular, using Er³⁺-doped RENPs, SWIR-PLIMASC enables multiplexed anti-counterfeiting. Leveraging Ho³⁺-doped RENPs as temperature indicators, this system is applied to SWIR photoluminescence lifetime-based thermometry. Opening up a new avenue for efficient SWIR photoluminescence lifetime mapping, this work is envisaged to contribute to advanced materials characterization, information science, and biomedicine.

A novel 2D thin-layer binary SbBi alloy is designed, which displays superior 2D structural stability, highly reversible alloying/dealloying, fast K/Li storage kinetics, and ultra-long-cycle stability in potassium/lithium-ion batteries (PIBs/LIBs).

Abstract

The inferior cycling stabilities or low capacities of 2D Sb or Bi limit their applications in high-capacity and long-stability potassium/lithium-ion batteries (PIBs/LIBs). Therefore, integrating the synergy of high-capacity Sb and high-stability Bi to fabricate 2D binary alloys is an intriguing and challenging endeavor. Herein, a series of novel 2D binary SbBi alloys with different atomic ratios are fabricated using a simple one-step co-replacement method. Among these fabricated alloys, the 2D-Sb_0.6Bi_0.4 anode exhibits high-capacity and ultra-stable potassium and lithium storage performance. Particularly, the 2D-Sb_0.6Bi_0.4 anode has a high-stability capacity of 381.1 mAh g⁻¹ after 500 cycles at 0.2 A g⁻¹ (≈87.8% retention) and an ultra-long-cycling stability of 1000 cycles (0.037% decay per cycle) at 1.0 A g⁻¹ in PIBs. Besides, the superior lithium and potassium storage mechanism is revealed by kinetic analysis, in-situ/ex-situ characterization techniques, and theoretical calculations. This mainly originates from the ultra-stable structure and synergistic interaction within the 2D-binary alloy, which significantly alleviates the volume expansion, enhances K⁺ adsorption energy, and decreases the K⁺ diffusion energy barrier compared to individual 2D-Bi or 2D-Sb. This study verifies a new scalable design strategy for creating 2D binary (even ternary) alloys, offering valuable insights into their fundamental mechanisms in rechargeable batteries.

Sensitive and accurate analysis for extracellular vesicles (EVs) has received substantial attention for noninvasive diagnosis and prognosis of diseases. Owing to the excellent programmability and modifiability, DNA-based nanomaterials have emerged as powerful tools for detecting EVs. The recent advancements in EV analysis using a variety of DNA-based nanomaterials are overviewed and unresolved challenges and perspective directions in the field are discussed.

Abstract

Extracellular vesicles (EVs) are cell-derived nanovesicles comprising a myriad of molecular cargo such as proteins and nucleic acids, playing essential roles in intercellular communication and physiological and pathological processes. EVs have received substantial attention as noninvasive biomarkers for disease diagnosis and prognosis. Owing to their ability to recognize protein and nucleic acid targets, DNA-based nanomaterials with excellent programmability and modifiability provide a promising tool for the sensitive and accurate detection of molecular cargo carried by EVs. In this perspective, recent advancements in EV analysis using a variety of DNA-based nanomaterials are summarized, which can be broadly classified into three categories: linear DNA probes, DNA nanostructures, and hybrid DNA nanomaterials. The design, construction, advantages, and disadvantages of different types of DNA nanomaterials, as well as their performance for detecting EVs are reviewed. The challenges and opportunities in the field of EV analysis by DNA nanomaterials are also discussed.

A spinel-CoFe₂O₄-decorated α-Fe₂O₃ nanotube arrays (NTAs) photoanode is developed for the oxidation of methanol to formaldehyde. The superiority of the co-edged FeO₆ octahedral structure in the Formox process is demonstrated. Impressively, the heterostructure and the interfacial effect of α-Fe₂O₃ and CoFe₂O₄ facilitates the separation and transport of photogenerated carriers, resulting in superior PEC methanol conversion efficiency and formaldehyde selectivity.

Abstract

The interaction mechanism between the reacting species and the active site of α-Fe₂O₃-based photoanodes in photoelectrochemical methanol conversion reaction is still ambiguous. Herein, a simple two-step strategy is demonstrated to fabricate a porous α-Fe₂O₃/CoFe₂O₄ heterojunction for the methanol conversion reaction. The influence of the electronic structure of active site and interfacial effect on the reaction are investigated by constructing two different FeO₆ octahedral configurations and heterogeneous structures. The optimal sample ZnFeCo-2 affords high photocurrent density of 1.17 mA cm⁻² at 0.5 V vs Ag/AgCl, which is 3.2 times than that of ZnFe (0.37 mA cm⁻²). Meanwhile, the ZnFeCo-2 also exhibits 97.8% Faraday efficiency of CH₃OH to HCHO, and long-term stability over 40 h. Furthermore, density functional theory calculations reveal that the heterostructured α-Fe₂O₃/CoFe₂O₄ with favorable electron transfer effectively lowers methanol adsorption, C–H bond activation, and HCHO desorption energy relative to the pristine α-Fe₂O₃, resulting in excellent methanol conversion efficiency.

Science Advances, <a href="https://www.science.org/toc/sciadv/8/7">Volume 8, Issue 7</a>, February 2022.

This review paper addresses the key challenges in vat polymerization and bioresin development for use in tissue engineering and regenerative applications. The paper provides a perspective on the unique bioresin design criteria and processing strategies required to aid the development of novel bioresins for vat polymerization and unlock the next evolution of biofabrication.

Abstract

The field of bioprinting has made significant advancements in recent years and allowed for the precise deposition of biomaterials and cells. However, within this field lies a major challenge, which is developing high resolution constructs, with complex architectures. In an effort to overcome these challenges a biofabrication technique known as vat polymerization is being increasingly investigated due to its high fabrication accuracy and control of resolution (µm scale). Despite the progress made in developing hydrogel precursors for bioprinting techniques, such as extrusion-based bioprinting, there is a major lack in developing hydrogel precursor bioresins for vat polymerization. This is due to the specific unique properties and characteristics required for vat polymerization, from lithography to the latest volumetric printing. This is of major concern as the shortage of bioresins available has a significant impact on progressing this technology and exploring its full potential, including speed, resolution, and scale. Therefore, this review discusses the key requirements that need to be addressed in successfully developing a bioresin. The influence of monomer architecture and bioresin composition on printability is described, along with key fundamental parameters that can be altered to increase printing accuracy. Finally, recent advancements in bioresins are discussed together with future directions.

Publication date: 5 May 2022

Source: Journal of Alloys and Compounds, Volume 902

Author(s): Jiale Man, Baolin Wu, Guosheng Duan, Lu Zhang, Gang Wan, Li Zhang, Naifu Zou, Yandong Liu

S = 1 /2 kagome lattice antiferromagnets (KLAFs) have attracted great interest since they are closely associated with the long-sought quantum spin liquid (QSL) state. The realization of S = 1/2 KLAF remains an outstanding challenge and efforts have focused principally on Cu2+, d9 compounds. Herein, the synthesis of the first structurally perfect d1 KLAF, (CH3NH3)2NaTi3F12, is presented. The trivalent oxidation state and the Jahn-Teller distortion of Ti3+ ions are probed by single crystal X-ray diffraction, X- ray photoelectron spectroscopy, and UV-vis-NIR diffuse reflectance. No structural phase transitions can be observed from 1.8 K to 523 K. However, a glass transition can be observed due to the disordered, interlayer CH3NH3+ cations. The Curie-Weiss temperature, θcw= -139.5(7) K, and the lack of long-range ordering in magnetic susceptibility and specific heat imply that this compound is a QSL candidate.

Author(s): Jeonghwan Ahn, Mujin You, Gwangyoung Lee, Tyler Volkoff, and Yongkyung Kwon

Path-integral Monte Carlo calculations have been carried out to investigate physical properties of a He4 monolayer adsorbed on a single 6,6,12-graphyne sheet, which is one of the graphyne families possessing a rectangular symmetry. To characterize elusive quantum phases of an adsorbed He4 monolayer ...

[Phys. Rev. B 99, 024113] Published Wed Jan 30, 2019

Flores Island, Indonesia, was inhabited by the small-bodied hominin species Homo floresiensis, which has an unknown evolutionary relationship to modern humans. This island is also home to an extant human pygmy population. Here we describe genome-scale single-nucleotide polymorphism data and whole-genome sequences from a contemporary human pygmy population living on Flores near the cave where H. floresiensis was found. The genomes of Flores pygmies reveal a complex history of admixture with Denisovans and Neanderthals but no evidence for gene flow with other archaic hominins. Modern individuals bear the signatures of recent positive selection encompassing the FADS (fatty acid desaturase) gene cluster, likely related to diet, and polygenic selection acting on standing variation that contributed to their short-stature phenotype. Thus, multiple independent instances of hominin insular dwarfism occurred on Flores.

Publication date: 5 October 2018
Source:Applied Catalysis B: Environmental, Volume 233
Author(s): Zizhong Zhang, Lin Huang, Jiangjie Zhang, Fengjiao Wang, Yanyu Xie, Xiaotong Shang, Yuyao Gu, Huibo Zhao, Xuxu Wang
Construction of heterostructure by intimately interfacing two or more semiconductor materials with different geometrical and electronically energetic alignments at nanoscale is very important to achieve the composite photocatalysts with a high photocatalytic efficiency. Here, we in-situ prepared an intimate contact MoS2/ZnIn2S4 heterostructure photocatalyst by a one-pot solvothermal reaction. The MoS2/ZnIn2S4 heterostructure significantly enhanced the photocatalytic H2 evolution of ZnIn2S4 under visible light illumination. The hydrogen evolution rate reaches 3891.6 μmol g⁻¹ h⁻¹ over 5%-MoS2/ZnIn2S4, which exceeded the photocatalytic activity of Pt-loaded ZnIn2S4 samples. The subtle atomic-level intimate contact and strong interactions between ZnIn2S4 and MoS2 was ascribed to a highly efficient charge carrier separation and thus photocatalytic activity for MoS2/ZnIn2S4. These results provide inspiration for the design of composited photocatalysts with efficient photocatalytic H2 evolution.

Graphical abstract

Abstract