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Random nanowire networks (NWNs) are regarded as promising memristive materials for applications in information storage, selectors, and neuromorphic computing. The further insight to understand their resistive switching properties and conduction mechanisms is crucial to realize the full potential of random NWNs. Here, a novel planar memristive device based on necklace-like structure Ag@TiO2 NWN is reported, in which a strategy only using water to tailor the TiO2 shell on Ag core for necklace-like core-shell structure is developed to achieve uniform topology connectivity. With analyzing the influence of compliance current on resistive switching characteristics and further tracing evolution trends of resistance state during the repetitive switching cycles, two distinctive evolution trends of low resistance state failure and high resistance state failure are revealed, which bear resemblance to memory loss and consolidation in biological systems. The underlying conduction mechanisms are related to the modulation of the Ag accumulation dynamics inside the filaments at cross-point junctions within conductive paths of NWNs. An optimizing principle is then proposed to design reproducible and reliable threshold switching devices by tuning the NWN density and electrical stimulation. The optimized threshold switching devices have a high ON/OFF ratio of ~107 with threshold voltage as low as 0.35 V. This work will provide insights into engineering random NWNs for diverse functions by modulating external excitation and optimizing NWN parameters to satisfy specific applications, transforming from neuromorphic systems to threshold switching devices as selectors.

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Despite the strong light absorption and high efficiency of multiple carrier generation and collection of carbon dots (CDs), little attention has been paid to the field of photodetection. Herein, CDs are synthesized through a green and facile strategy, which only uses graphite rods and distilled water. It is found that the oxygen content and the optical properties of CDs could be modulated by the voltage applied between the two graphite rods. A series of tests reveal that the excitationindependent blue photoluminescence (PL) emission of as-prepared CDs is related to the topological defects. And the oxygencontaining groups would bring new energy levels between the band gaps of CDs, which enhanced the excitation-dependent yellowgreen PL emission and the absorption from the near-ultraviolet (UV) to the visible range. The CDs with fewer oxygen-containing groups show strong UV absorption and short cutoff wavelength, and they are utilized to fabricate solar-blind UV photodetectors. Tested under 254 nm UV illumination, the detectors exhibit a high photoresponsivity (1.14 mA/W) and highly characteristic wavelength-dependent response (R 254 /R 365 = 115). This study provides a deeper understanding of the relationships between optical properties and the structure/composition of CDs. More importantly, the solution processability of CDs paves the way for future high-performance, low-cost solar-blind photodetectors.

To boost the performance of microbial fuel cells (MFCs), a novel material of polypyrrole nanowires (PPy-NWs) modified by carbon dots (CDs) is synthesized by polymerizing pyrrole monomers and CDs, in which CDs are attached and distributed on the surface of the PPy-NWs, thus leading to the rough surface with a special dot-line structure. Such CDs/PPy-NW composite with special unique structure exhibits superior properties, and excellent performance is found for MFC using CDs/PPy-NW composite as anode. The electron transfer rate increases to 0.0934 s -1 with a sharp rise by 26% over pure PPy-NWs, and the resistances of CDs/PPy-NW electrode are only one third of those of pure PPy-NWs electrode. Further, the mini-MFC equipped with the CDs/PPy-NW composite as anode exhibits a high open circuit voltage (630 mV) and its maximum power density with a value of 291.4 mW m -2 is twice that of the mini-MFC equipped with pure PPy-NWs anode. These results demonstrate CDs/PPy-NW with a unique dot-line structure as a more promising anode material for MFC application.