Abstract3D organic–inorganic and all‐inorganic lead halide perovskites have been intensively pursued for resistive switching memories in recent years. Unfortunately, instability and lead toxicity are two foremost challenges for their large‐scale commercial applications. Dimensional reduction and composition engineering are effective means to overcome these challenges. Herein, low‐dimensional inorganic lead‐free Cs3Bi2I9 and CsBi3I10 perovskite‐like films are exploited for resistive switching memory applications. Both devices demonstrate stable switching with ultrahigh on/off ratios (≈106), ultralow operation voltages (as low as 0.12 V), and self‐compliance characteristics. 0D Cs3Bi2I9‐based device shows better retention time and larger reset voltage than the 2D CsBi3I10‐based device. Multilevel resistive switching behavior is also observed by modulating the current compliance, contributing to the device tunability. The resistive switching mechanism is hinged on the formation and rupture of conductive filaments of halide vacancies in the perovskite films, which is correlated with the formation of AgIx layers at the electrode/perovskite interface. This study enriches the library of switching materials with all‐inorganic lead‐free halide perovskites and offers new insights on tuning the operation of solution‐processed memory devices.

Lead halide perovskites‐based memory devices have attracted considerable interest due to their unique current–voltage (I–V) hysteresis. Herein, all‐inorganic CsPbI3 perovskite film surviving 30 d of air storage is prepared by using a poly‐vinylpyrrolidone‐assisted passivation method under fully open‐air condition. Afterwards, a memory device with a sandwich structure of Ag/CsPbI3/indium tin oxide is manufactured. From I–V characteristics of pristine device, a spontaneous reaction between the active Ag electrode and I− ions under air exposure is suggested. Furthermore, complete degradation of Ag electrode and formation of AgIx are verified, which also accompanies with generation of more iodine vacancies (VI) in perovskite film. The memory device with AgIx layer shows a bipolar resistive switching behavior, ultrahigh ON/OFF ratio (above 106), nonvolatile, reliable, and reproducible switching performance. Cell area and temperature dependent characteristics propose that the resistive switching is dominated by VI filament in low‐resistance state and thermally assisted hopping in high‐resistance state. This study provides a new insight to understand switching behavior from the way of electrode degradation and metal iodide formation in lead iodide perovskites‐based memory devices and also suggests a potential application for AgIx‐induced resistive switching in CsPbI3‐based memory device.

Purpose: D-psicose-3-epimerase (DPEase) catalyses the isomerisation of D-fructose to D-psicose, a rare sugar in nature with unique nutritional and biological functions. An effective industrial-scale method is needed for D-psicose production. Herein, the expression of a neutral and a slightly acidic pH DPEase in Bacillus subtilis was evaluated. Methods: Two DPEase genes from Clostridium bolteae and Dorea sp. were separately expressed in B. subtilis via plasmid pSTOP1622, and an extra P43 promoter was employed to the expression cassette. The fermentation conditions of the engineered B. subtilis strains were also optimised, to facilitate both cell growth and enzyme production. Result: The introduction of P43 promoter to the two DPEase genes increased enzyme production by about 20%. Optimisation of fermentation conditions increased DPEase production to 21.90 U/g at 55°C and 24.01 U/g at 70°C in B. subtilis expressing C. bolteae or Dorea sp. DPEase, equating to a 94.67% and 369.94% increase, respectively, relative to controls. Conclusion: Enhanced DPEase production was achieved in B. subtilis expressing C. bolteae or Dorea sp. DPEase genes.

The design of electrode materials with rational core/shell structures is promising for improving the electrochemical properties of supercapacitors. Hence, hierarchical FeCo 2 S 4 @FeNi 2 S 4 core/shell nanostructures on Ni foam were fabricated by as imple hydrothermalm ethod. Owing to their structure and synergistic effect, they delivera ne xcellent specificc apacitance of 2393Fg À1 at 1Ag À1 and long cycle lifespana sp ositive electrode materials. An asymmetric supercapacitor device with FeCo 2 S 4 @FeNi 2 S 4 as positivee lec-trode and graphene as negative electrode exhibited aspecific capacitanceo f1 33.2 Fg À1 at 1Ag À1 and ah igh energy density of 47.37 Whkg À1 at ap owerd ensityo f8 00 Wkg À1 . Moreover,t he devices howedr emarkable cycling stability with 87.0 %s pecific-capacitance retention after 5000 cycles at 2Ag À1 .T hese results demonstrate that the hierarchical FeCo 2 S 4 @FeNi 2 S 4 core/shell structuresh ave great potentiali n the field of electrochemical energy storage.

The cross‐compatibility of electronic devices and biomedicine has greatly promoted the new medical diagnosis and treatment technology. Developing biodegradable resistive random access memory device (ReRAM) with low power is key to biomedical application. In this paper, the all‐inorganic air‐stable and high‐quality AgBi2I7 perovskite‐like film is successfully prepared by introducing Ag+ into the Bi‐I system. The device has a higher ON/OFF ratio after annealing in NH3 compared with annealing in vacuum, and the switching behavior changes from gradual type to abrupt filamentary type. Meanwhile, ultralow power characteristic with the set power of 6.9 × 10–7 W (0.42V@1.6 × 10–6A) and the reset power of 1.5 × 10–8 W (1V@1.5 × 10–8A) is achieved in the Ag/AgBi2I7/ITO memory devices after annealing in NH3. Good biodegradability is affirmed via put Ag/AgBi2I7/ITO device in PBS solution. Results show that the Ag/AgBi2I7/ITO memory devices are the promising candidate in the field of biomedical application.