CsPbX 3 (X = halide, Cl, Br, or I) all-inorganic halide perovskites (IHPs) are regarded as promising functional materials because of their tunable optoelectronic characteristics and superior stability to organic-inorganic hybrid halide perovskites. Herein, nonvolatile resistive switching (RS) memory devices based on all-inorganic CsPbI 3 perovskite are reported. An air-stable CsPbI 3 perovskite film with a thickness of only 200 nm is successfully synthesized on a platinum-coated silicon substrate using low temperature all-solution process. The RS memory devices of Ag/polymethylmethacrylate (PMMA)/ CsPbI 3 /Pt/Ti/SiO 2 /Si structure exhibit reproducible and reliable bipolar switching characteristics with an ultralow operating voltage (<+0.2 V), high on/off ratio (>10 6 ), reversible RS by pulse voltage operation (pulse duration < 1 ms), and multilevel data storage. The mechanical flexibility of the CsPbI 3 perovskite RS memory device on a flexible substrate is also successfully confirmed. With analyzing the influence of phase transition in CsPbI 3 on RS characteristics, a mechanism involving conducting filaments formed by metal cation migration is proposed to explain the RS behavior of the memory device. This study will contribute to the understanding of the intrinsic characteristics of IHPs for low-voltage resistive switching and demonstrate the huge potential of them for use in low-power consumption nonvolatile memory devices on next-generation computing systems.

Since it was first discovered, thousands of years ago, silkworm silk has been known to be an abundant biopolymer with a vast range of attractive properties. The utilization of silk fibroin (SF), the main protein of silkworm silk, has not been limited to the textile industry but has been further extended to various high-tech application areas, including biomaterials for drug delivery systems and tissue engineering. The outstanding mechanical properties of SF, including its facile processability, superior biocompatibility, controllable biodegradation, and versatile functionalization have allowed its use for innovative applications. In this review, we describe the structure, composition, general properties, and structure-properties relationship of SF. In addition, the methods used for the fabrication and modification of various materials are briefly addressed. Lastly, recent applications of SF-based materials for small molecule drug delivery, biological drug delivery, gene therapy, wound healing, and bone regeneration are reviewed and our perspectives on future development of these favorable materials are also shared.

Carbon and graphene quantum dots for biological and sensing applications of neurotransmitters.

Recently, organometallic and all-inorganic halide perovskites (HPs) have become promising materials for resistive switching (RS) nonvolatile memory devices with low power consumption because they show current–voltage hysteresis caused by fast ion migration. However, the toxicity and environmental pollution potential of lead, a common constituent of HPs, has limited the commercial applications of HP-based devices. Here, RS memory devices based on lead-free all-inorganic cesium tin iodide (CsSnI3) perovskites with temperature tolerance are successfully fabricated. The devices exhibit reproducible and reliable bipolar RS characteristics in both Ag and Au top electrodes (TEs) with different switching mechanisms. The Ag TE devices show filamentary RS behavior with ultralow operating voltages (<0.15 V). In contrast, the Au TE devices have interface-type RS behavior with gradual resistance changes. This suggests that the RS characteristics are attributed to either the formation of metal filaments or the ion migration of defects in HPs under applied electric fields. These distinct mechanisms may permit the opportunity to design devices for specific purposes. This work will pave the way for lead-free all-inorganic HP-based nonvolatile memory for commercial application in HP-based devices.