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The resistance random access memory (RRAM) based on biomaterials has great potential application in the sustainable electronic devices with the advantages of being sustainable, green, and environment-friendly, and it can offer a potential route for developing bio-RRAM devices, which would be a competitive bench in development of multipurpose memory devices. In our work, the banana peel, an ubiquitous useless waste, is introduced as an intermediate insulating material to preparing resistive switching memory device with Ag/Banana peel/Ti structure, in which the superior switching memory performance with a lager high resistance state/low resistance state resistance ratio and long retention characteristics are revealed. Moreover, the coexistence of memristor effect, capacitance effect, and negative differential resistance phenomenon are observed in our device. The repeatable nonvolatile resistive switching memory behaviors are attributed to the redox properties of metal cations contained in biomaterials.

Since memristors as an emerging nonlinear electronic component have been considered the most promising candidate for integrating nonvolatile memory and advanced computing technology, the in-depth reveal of the memristive mechanism and the realization of hardware fabrication have facilitated their wide applications in next-generation artificial intelligence. Flexible memristors have shown great promising prospects in wearable electronics and artificial electronic skin (e-skin), but in-depth research on the physical mechanism is still lacking. Here, a flexible memristive device with a Ag/HfO x /Ti/PET crossbar structure was fabricated, and a remarkable analog switching characteristic similar to synaptic behavior was observed. Through detailed data fitting and in-depth physical mechanism analysis, it is confirmed that the analog switching characteristics of the device are mainly caused by carrier tunneling. Furthermore, the memristive properties of the Ag/HfO x /Ag/PET device can be attributed to the conductive filaments formed by the redox reaction of the active metal Ag. Finally, the interfacial barrier is extracted by the Arrhenius diagram and the energy band diagram, which is drawn to clearly demonstrate the conduction mechanism of charge trapping in the device. Therefore, the HfO x -based flexible memristor with analog switching behavior and stable memory performance lays the foundation for cutting-edge applications in wearable electronics and smart e-skin.

Harvesting electrical energy from different forms of water by using the hydrovoltaic effect is a promising approach to green energy acquisition. However, at present, different devices are required to obtain electrical energy from different water forms, and the output performance of the devices is not high, which greatly reduces the convenience and effectiveness of harvesting electrical energy from different water forms. Here, a carbon nanofiber electrode with a hierarchical porous structure capable of promoting water molecule adsorption, rapid penetration, and diffusion is reported. Besides, the electrode acts as a nanofluidic diode with anodic aluminum oxide in which the built‐in electric field drives selective separation and directional transport of ions and efficient ion/electron current conversion at the electrodes. Unlike typical hygroelectric devices, the device can work with moisture (93% relative humidity, 25 °C, open‐circuit voltage (VOC) ≈ 1.1 V, short‐circuit current density (JSC) ≈ 27 µA cm−2), water droplets (2 µL, VOC ≈ 1.03 V, JSC ≈ 640 µA cm−2), and bulk water (VOC ≈ 1.15 V, JSC ≈ 256 µA cm−2). It provides an efficient way to generate electricity in multiform water environment, greatly broadening the working scene and improving the adaptability of the device in complex weather environments.

The Bi-Y-O system has been investigated by X-ray powder diffraction, electron diffraction, UV-vis and IR experiments. A metastable cubic high temperature phase of BiYO3 with fluorite-type structure has been structurally characterized for the first time and shows a large band gap of ∼ 5.9 eV. A unified description for the numerous structural variants discovered in the Bi-Y-O system is established within the symmetry breaking approach. This rich structural phenomenon makes the Bi-Y-O system a promising candidate in the search for new topological insulators for applications. On this basis, a long standing controversy on the phase diagram of the Bi-Y-O system has been solved. Our DFT calculations predict a high pressure phase for BiYO3 with perovskite (ABO3) structure and ordering of Bi and Y on the A and B sites, respectively. However, our analysis of the nature of the low energy electronic structure shows that this phase is not a suitable candidate for a topological insulator.

PbS nanoparticles (PbS NPs), an efficient sensitizer for TiO2 nanotube arrays (TiO2 NAs), were fabricated by the method of sonication-assisted successive ionic layer adsorption and reaction (SILAR). The filling degree and size of PbS NPs can be tuned by changing the repeated cycles (N) of the SILAR process. TiO2 NAs can be fully covered with PbS NPs with a size ranging from less than 4 nm to 25 nm and large aggregates inside and outside the nanotubes when N reaches 15. The growth mechanism of PbS NPs in TiO2 NAs was expounded in great detail in this work. Ultraviolet-visible diffuse-reflectance spectra and surface photovoltage spectroscopy were used to investigate the light absorption properties and the transfer behavior of photogenerated charges in PbS-modified TiO2 NA heterostructures. Results show that the absorption range of TiO2 NAs is extended from the ultraviolet to the visible region by PbS NPs modification. A heterojunction is formed between PbS NPs and TiO2 NAs, facilitating the separation of photogenerated charge carriers. This PbS NPs fully-covered TiO2 NA electrode exhibits the best photoelectrochemical performance in all PbS-sensitized TiO2 NA electrodes, due to a larger number of small PbS NPs (<4 nm). With AM 1.5G illumination at 100 mW cm(-2), its short-circuit current density, open-circuit voltage and photoelectric conversion efficiency are 9.55 mA cm(-2), 0.95 V and 2.83%, respectively.

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