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All inorganic metal halide perovskite nanocrystals (NCs) have attracted much attention for their outstanding optoelectronic properties, which can be tuned by the composition, surface, size and morphology in nanoscale. Herein, we report the microfluidic synthesis of hollow CsPbBr3 perovskite NCs through the nanoscale Kirkendall effect. The formation mechanism of the hollow structure (Kirkendall void) controlled by the temperature, flow rate, ratios of precursors and ligands was investigated. Compared with the solid CsPbBr3 NCs of the same size, the hollow CsPbBr3 NCs exhibit blue shifts in ultraviolet–visible (UV–vis) absorption and photoluminescence (PL) spectra, and remarkably longer PL average lifetime (~ 98.2 ns). Quantum confinement effect, inner surface induced additional trap states and lattice strain of the hollow CsPbBr3 NCs were discussed in understanding their unique optoelectronic properties. The hollow CsPbBr3 NC based photodetector exhibits an outstanding negative photoconductivity (NPC) detectivity of 8.9 × 1012 Jones. They also show potentials in perovskite NC based photovoltaic and light emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]

Organic field‐effect transistor (OFET) memory devices are benefiting from their independent gate modulation advantages for hardware implementation of synaptic functionalities. However, the imitation of selective release of excitatory–inhibitory neurotransmitters in a unipolar synaptic OFET is challenging due to the unbalanced mobile carrier concentration. Here, a p‐type synaptic OFET memory with CsPbBr3 quantum dots (QDs) as nano‐floating gates (NFGs) is developed, which can emulate both the excitatory–inhibitory responses of the biological synapse and their reconfigurable nature. By controlling the offset difference between stimulus voltage and reading voltage, the concomitant and independently expressed excitatory and inhibitory responses are successfully implemented in a negative gate modulation manner, but without introducing an ambipolar semiconductor or additional optical terminal. This reconfigurable modulation is ascribed to the dynamic competition between external electric field and built‐in electric field assisted by charge trapping in shallow traps. The proposed gate voltage‐offset method can be generally adapted to other unipolar synaptic OFETs. These results provide insight into OFET memory devices for building neuromorphic hardware elements with tailorable synaptic plasticity. [ABSTRACT FROM AUTHOR]

Pd-based nanostructures have potential use in optronics, sensing, organic catalysis, and gas-involved electrocatalysis. Despite the substantial advances made, controllable synthesis of amorphous-dominated Pd-based ternary alloy nanoparticles or related assemblies still faces challenges, and their uses for the hydrogen evolution reaction (HER) have not been fully studied. Here, the amorphous-dominated ultrasmall PdCuMo nanoparticle (2.58 nm) assemblies are fabricated under mild conditions via a polyether-assisted thermal reduction strategy, which possesses numerous amorphous/crystalline (a/c) heterophase interfaces, mesoporous structures, and a high specific surface area. Due to the presence of unique a/c heterophase interfaces, proper alloy constituents, and their strong interplay that can regulate the surface/interface electronic structure and optimize the Pd–H bonding intensity, the resultant amorphous-dominated PdCuMo assemblies manifest unprecedented HER performance with an ultralow overpotential of 15.6 mV at a current density of 10 mA cm–2 and a high mass activity of 390 A gPd–1 at a potential of −0.05 V vs reversible hydrogen electrode (RHE), outperforming their binary counterparts (PdCu and PdMo), PdCuMo control sample with a relatively high crystallinity (c-PdCuMo), benchmark Pt/C (commercial, 20%), and the state-of-the-art studied Pd-based electrocatalysts. Additionally, such amorphous-dominated PdCuMo assemblies exhibit outstanding durability and high faradic efficiency yet. This work may shed light on designing advanced amorphous-dominated or a/c heterophase Pd-based multicomponent alloy nanostructures or related assemblies for application in water splitting or other important technological fields. [ABSTRACT FROM AUTHOR]

All-inorganic lead halide perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals (NCs) have shown great application prospects in optoelectronic fields. Their properties can be feasibly tuned by the ratio of different halide ions. Post-synthesis halide anion exchange of Cl—Br or Br—I in CsPbX3 NCs allows getting any desired composition of CsPbClxBr3−x and CsPbBrxI3−x (0 ≤ x ≤ 3). However, due to the large difference of the Cl and I radii, they can only substitute each other in a limited ratio to form CsPbClyI3−y (0 < y < δ or 3 − δ < y < 3). To date, little has been known on the phase diagram of the ternary halide perovskite of CsPbClaBrbI3−a−b (0 < a + b < 3). In this work, the ternary halide perovskite phase diagram is constructed by the strategy of halide anion exchange between perovskite NCs. From the diagram, the composition and proportion of the perovskite NC final phases from any starting perovskite NC mixture can be calculated. Specifically, a two-phase perovskite NC system showing stable dual photoluminescence (PL) peaks is achieved. [ABSTRACT FROM AUTHOR]

CsPbX3 (X = Cl, Br, I) perovskite nanowires and nanorods are important 1D and quasi 1D semiconductor nanomaterials. They have shown significant prospect in optic and optoelectronic applications, especially for their adaptability to flexible devices, good carrier transport performance, polarized absorption, and emission properties. Due to the high dependence of the property to the morphology, it is crucial to develop synthesis methods with continuous diameter and length tunability of the 1D/quasi 1D perovskites. In this report, a feasibly room temperature synthesis method was developed for ultrathin CsPbX3(X = Cl, Br, I) perovskite nanowires. By aging the CsPbBr3 nanowires (≈2*500 nm) under ambient condition with proper concentration and time, the nanowires are transformed to nanorods with controllable diameter and length. Reversibly, the nanorods can be transformed back to nanowires. Equilibrium mechanism is adopted to understand the morphology evolution, and hopefully could be generally applied to many other nano materials. The polarized optoelectronic properties of the nanowires and nanorods are interpreted by a model based on the two‐channel anisotropies measurement. Polarized light detectors constructed by oriented assembled nanowires are fabricated to demonstrate their application potentials. [ABSTRACT FROM AUTHOR]