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Cesium lead halide perovskite nanocrystals (PNCs) have attracted great attention in optoelectronic devices due to their excellent optical properties, such as tunable emission wavelengths, long carrier lifetime, and narrow full width at half-maximum (fwhm). However, the poor stability of PNCs in water or humid environments greatly limits their wide-spreading applications. It is challenging to prepare PNCs with long-term stability in water. Herein, we successfully prepared CsPbBr3@PDMS microspheres by using the emulsification method. Due to the protection of the PDMS layer, the CsPbBr3@PDMS microspheres exhibit good optical properties and stability in water, acid, and alkali solutions. In addition, to expand the application of CsPbBr3 NCs in flexible optical devices and wearable devices, we first prepared stretchable, stable, and photoluminescent hydrogel with a CsPbBr3@PDMS microsphere (hydrogel/CsPbBr3@PDMS) by using the emulsification method. The hydrogel/CsPbBr3@PDMS elastomer exhibits good stability and stretchability. Furthermore, the hydrogel/CsPbBr3@PDMS elastomer retains bright green emission and stability under different mechanical deformations. This work provides a method to improve the CsPbBr3 PNCs with high stability by emulsification, which could also expand the applications of PNCs in underwater display, wearable, and flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

Li dendrite and the shuttle effect are the two primary hindrances to the commercial application of lithium-sulfur batteries (LSBs). Here, a multifunctional separator has been fabricated via successively coating carbon nanotubes (CNTs) and lithium phytate (LP) onto a commercial polypropylene (PP) separator to improve the performance of LSBs. The LP coating layer with abundant electronegative phosphate group as permselective ion sieve not only reduces the polysulfide shuttle but also facilitates uniform Li + flux through the PP separator. And the highly conductive CNTs on the second layer act as a second collector to accelerate the reversible conversion of sulfide species. The synergistic effect of LP and CNTs further increases the electrolyte wettability and reaction kinetics of cells with a modified separator and suppresses the shuttle effect and growth of Li dendrite. Consequently, the LSBs present much enhanced rate performance and cyclic performance. It is expected that this study may generate an executable tactic for interface engineering of separator to accelerate the industrial application process of LSBs.

A new two-dimensional material B 2 S 2 has been successfully synthesized for the first time and validated using first-principles calculations, with fundamental properties analyzed in detail. B 2 S 2 has a similar structure as transition-metal dichalcogenides (TMDs) such as MoS 2 , and the experimentally prepared free-standing B 2 S 2 nanosheets show a uniform height profile lower than 1 nm. A thickness-modulated and unique oxidation-level dependent band gap of B 2 S 2 is revealed by theoretical calculations, and vibration signatures are determined to offer a practical scheme for the characterization of B 2 S 2 . It is shown that the functionalized B 2 S 2 is able to provide favorable sites for lithium adsorption with low diffusion barriers, and the prepared B 2 S 2 shows a wide band photoluminescence response. These findings offer a feasible new and lighter member for the TMD-like 2D material family with potential for various aspects of applications, such as an anode material for Li-ion batteries and electronic and optoelectronic devices.

It was interesting to experimentally find that the thermal insulation of silica aerogels was improved by doping graphene sheets with high heat conductivity. The underlying mechanism is investigated in the present work from the perspective of gas-solid interaction using a comprehensive analysis of molecular dynamics (MD) simulations, theoretical modeling, and experimental data. The MD-modeled small pores are demonstrated to effectively represent big pores in silica aerogels because of similar heat conduction physics, because it is found that adsorption does not contribute to gas heat conduction. Meanwhile, based on the experimentally measured density, the porous structures are schematically re-engineered using molecular modeling for the first time. The evaluated pore size distributions numerically present a consistency with available experimental data. Inspired by the visualization of the 3D pore structure, we proposed a graphene/silica/nitrogen model to evaluate the role of graphene in heat conduction: it can not only reduce effective gas collision (impede heat transport) but also enhance the gas-solid coupling effect. The former is dominant because of the high porosity, leading to an improvement in thermal insulation. The competition between them can be the reason for the "trade-off" phenomenon in the graphene doping effect in the available experiment.

The second near-infrared window emission (1.0-1.7 μm, NIR-II) has received extensive attention with the advantages of negligible tissue scattering, reduced autofluorescence, and less background noise. Here a novel analysis platform based on quantum dots (QDs) for highly selective detection of Zn 2+ and Cd 2+ with an enhanced NIR-II fluorescence is reported for the first time. We have developed a facile two-step route to synthesize the water-soluble Ag 2 S QDs, constituting of a green hydrothermal process and followed surface ligands exchange. Surface passivation was proposed to be the mechanism for the enhanced fluorescence. The added Zn 2+ or Cd 2+ could react with the surface thioglycollic acid to form Zn-thiol or Cd-thiol complex passivation shell, which restored surface defects and suppressed nonradiative recombination pathway. The detection platform exhibited a linear relationship between the ion concentrations and enhanced fluorescence and had a detection limit as low as 760 nM for Zn 2+ and 546 nM for Cd 2+ at pH = 7.4. Furthermore, the as-synthesized Ag 2 S QDs showed good robustness in real sample matrix and were demonstrated to be able to detect exogenous Zn(II) in cells. These properties suggest potential applications of detection of Zn 2+ in biology and Cd 2+ in environment via the NIR-II fluorescent Ag 2 S QDs.

Si-based nanostructure composites have been intensively investigated as anode materials for next-generation lithium-ion batteries because of their ultra-high-energy storage capacity. However, it is still a great challenge to fabricate a perfect structure satisfying all the requirements of good electrical conductivity, robust matrix for buffering large volume expansion, and intact linkage of Si particles upon long-term cycling. Here, we report a novel design of Si-based multicomponent three-dimensional (3D) networks in which the Si core is capped with phytic acid shell layers through a facile high-energy ball-milling method. By mixing the functional Si with graphene oxide and functionalized carbon nanotube, we successfully obtained a homogeneous and conductive rigid silicon-based gel through complexation. Interestingly, this Si-based gel with a fancy 3D cross-linking structure could be writable and printable. In particular, this Si-based gel composite delivers a moderate specific capacity of 2711 mA h g -1 at a current density of 420 mA g -1 and retained a competitive discharge capacity of more than 800.00 mA h g -1 at the current density of 420 mA g -1 after 700 cycles. We provide a new method to fabricate durable Si-based anode material for next-generation high-performance lithium-ion batteries.

Ni 3 S 2 nanowire arrays doped with vanadium(V) are directly grown on nickel foam by a facile one-step hydrothermal method. It is found that the doping can promote the formation of Ni 3 S 2 nanowires at a low temperature. The doped nanowires show excellent electrocatalytic performance toward hydrogen evolution reaction (HER), and outperform pure Ni 3 S 2 and other Ni 3 S 2 -based compounds. The stability test shows that the performance of V-doped Ni 3 S 2 nanowires is improved and stabilized after thousands of linear sweep voltammetry test. The onset potential of V-doped Ni 3 S 2 nanowire can be as low as 39 mV, which is comparable to platinum. The nanowire has an overpotential of 68 mV at 10 mA cm -2 , a relatively low Tafel slope of 112 mV dec -1 , good stability and high Faradaic efficiency. First-principles calculations show that the V-doping in Ni 3 S 2 extremely enhances the free carrier density near the Fermi level, resulting in much improved catalytic activities. We expect that the doping can be an effective way to enhance the catalytic performance of metal disulfides in hydrogen evolution reaction and V-doped Ni 3 S 2 nanowire is one of the most promising electrocatalysts for hydrogen production.

The expression level of tumor-related mRNA can reveal significant information about tumor progression and prognosis, so specific mRNA in cells provides an important approach for biological and disease studies. Here, fluorescence lifetime imaging of nanoflares in living cells was first employed to detect specific intracellular mRNA. We characterized the lifetime changes of the prepared nanoflares before and after the treatment of target mRNA and also compared the results with those of fluorescence intensity-based measurements both intracellularly and extracellularly. The nanoflares released the cy5-modified oligonucleotides and bound to the targets, resulting in a fluorescence lifetime lengthening. This work puts forward another dimension of detecting specific mRNA in cells and can also open new ways for detection of many other biomolecules.