Colloidal nanocrystals of fully inorganic cesium lead halide (CsPbX3, X = Cl, Br, I, or combinations thereof) perovskites have attracted much attention for photonic and optoelectronic applications. Herein, we demonstrate a facile room-temperature (e.g., 25 °C), ligand-mediated reprecipitation strategy for systematically manipulating the shape of CsPbX3 colloidal nanocrystals, such as spherical quantum dots, nanocubes, nanorods, and nanoplatelets. The colloidal spherical quantum dots of CsPbX3 were synthesized with photoluminescence (PL) quantum yield values up to >80%, and the corresponding PL emission peaks covering the visible range from 380 to 693 nm. Besides spherical quantum dots, the shape of CsPbX3 nanocrystals could be engineered into nanocubes, one-dimensional nanorods, and two-dimensional few-unit-cell-thick nanoplatelets with well-defined morphology by choosing different organic acid and amine ligands via the reprecipitation process. The shape-dependent PL decay lifetimes have been determined to be several to tens to hundreds of nanoseconds. Our method provides a facile and versatile route to rationally control the shape of the CsPbX3 perovskites nanocrystals, which will create opportunities for applications such as displays, lasing, light-emitting diodes, solar concentrators, and photon detection.

Colloidal nanocrystals of lead halide perovskites have recently received great attention due to their remarkable performance in optoelectronic applications (e.g., light-emitting devices, flexible electronics, and photodetectors). However, the use of lead remains of great concern due to its toxicity and bioaccumulation in the ecosystem; herein we report a strategy to address this issue by using tetravalent tin (Sn 4+ ) instead of divalent lead (Pb 2+ ) to synthesize stable Cs 2 SnI 6 perovskite nanocrystals. The shapes of assynthesized Cs 2 SnI 6 nanocrystals are tuned from spherical quantum dots, nanorods, nanowires, and nanobelts to nanoplatelets via a facile hot-injection process using inexpensive and nontoxic commercial precursors. Spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) and simulation studies revealed a well-defined face-centered-cubic (fcc) perovskite derivative structure of Cs 2 SnI 6 nanocrystals. The solution-processed Cs 2 SnI 6 nanocrystal-based field effect transistors (FETs) displayed a p-type semiconductor behavior with high hole mobility (>20 cm 2 /(V s)) and high I-ON/I-OFF ratio (>10 4 ) under ambient conditions. We envision that this work will pave the way to produce new families of high-performance, stable, low-cost and nontoxic nanocrystals for optoelectronic applications.

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Nanocrystal shape can have a strong influence on the 2D and 3D structure of nanocrystal (NC) arrays, and it is important to understand its role if functional magnetic nanodevices are to be realized. Here is presented a detailed TEM analysis of 11 nm Co NCs and their effect on the superlattice assembly. Twins and stacking faults (see Figure) are reported to be due to mismatched faces on adjacent nanocrystals (see also Cover).

Ultra-thin W(18)O(49) nanowires were initially obtained by a simple solvothermal method using tungsten chloride and cyclohexanol as precursors. Thermal processing of the resulting bundled nanowires has been carried out in air in a tube furnace. The morphology and phase transformation behavior of the as-synthesized nanowires as a function of annealing temperature have been characterized by x-ray diffraction and electron microscopy. The nanostructured bundles underwent a series of morphological evolution with increased annealing temperature, becoming straighter, larger in diameter, and smaller in aspect ratio, eventually becoming irregular particles with size up to 5 µm. At 500 °C, the monoclinic W(18)O(49) was completely transformed to monoclinic WO(3) phase, which remains stable at high processing temperature. After thermal processing at 400 °C and 450 °C, the specific surface areas of the resulting nanowires dropped to 110 m(2) g(-1) and 66 m(2) g(-1) respectively, compared with that of 151 m(2) g(-1) for the as-prepared sample. This study may shed light on the understanding of the geometrical and structural evolution occurring in nanowires whose working environment may involve severe temperature variations.

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Noble Metal-free catalysts attracted much attention as promising candidates for Pt-based catalyst replacement to advance applications related to oxygen reduction reaction (ORR), which is critical for large-scale renewable energy storage and conversion. Herein, this work focused on a synthesis of noble metal-free ORR electrocatalysts consisting of porous N-rich carbon/MXene, which was obtained using very conductive and reactive Ti3C2 MXene and polypyrrole (PPy) as a C and N source. The electrocatalyst exhibited excellent electrocatalytic activity and stability with an onset and a half-wave potentials equal to 0.85 and 0.71 V, respectively. Results obtained in this work demonstrate how to design efficient noble metal-free ORR electrocatalysts applicable to other chemical systems.

Steel corrosion is a global problem in marine engineering. Numerous inhibitory treatments have been applied to mitigate the degradation of metallic materials; however, they typically have a high cost and are not environmental friendly. Here, we present a novel and “green” approach for the protection of steel by a marine bacterium Pseudoalteromonas lipolytica. This approach protects steel from corrosion in seawater via the formation of a biofilm followed by the formation of an organic–inorganic hybrid film. The hybrid film is composed of multiple layers of calcite and bacterial extracellular polymeric substances, exhibiting high and stable barrier protection efficiency and further providing an in situ self-healing activity. The process involving the key transition from biofilm to biomineralized film is essential for its lasting anticorrosion activity, which overcomes the instability of biofilm protection on corrosion. Therefore, this study introduces a new perspective and an option for anticorrosion control in marine environments.