Recent Progress for Single-Molecule Magnets Based on Rare Earth Elements.

Single-molecule magnets (SMMs) have attracted much attention due to their potential applications in molecular spintronic devices. Rare earth SMMs are considered to be the most promising for application owing to their large magnetic moment and strong magnetic anisotropy. In this review, the recent progress in rare earth SMMs represented by mononuclear and dinuclear complexes is highlighted, especially for the modulation of magnetic anisotropy, effective energy barrier (Ueff) and blocking temperature (TB). The terbium- and dysprosium-based SMMs have a Ueff of 1541 cm-1 and an increased TB of 80 K. They break the boiling point temperature of liquid nitrogen. The development of the preparation technology of rare earth element SMMs is also summarized in an overview. This review has important implications and insights for the design and research of Ln-SMMs.

Novel Refreshable Braille Display Based on the Layered Electromagnetic Driving Mechanism of Braille Dots.

In the digital era, Braille displays enable visually impaired people to easily access information. Different from traditional piezoelectric Braille displays, a novel electromagnetic Braille display is realized in this study. The novel display has the advantages of a stable performance, a long service life and a low cost and is based on an innovative layered electromagnetic driving mechanism of Braille dots, which can achieve a dense arrangement of Braille dots and provide a sufficient support force for them. The T-shaped screw compression spring, which causes the Braille dots to fall back instantaneously, is optimized to achieve a high refresh frequency and to enable visually impaired people to read Braille quickly. The experimental results show that under an input voltage of 6 V, the Braille display can work stably and reliably and provide a good fingertip touch; the Braille dot support force is greater than 150 mN, the maximum refresh frequency can reach 50 Hz, and the operating temperature is lower than 32 °C. Therefore, this cost-effective Braille display is expected to benefit a vast number of low-income visually impaired people in developing countries and improve their learning, working and living conditions.

Enhanced Photo-Fenton Activity of SnO2/α-Fe2O3 Composites Prepared by a Two-Step Solvothermal Method.

The x-SnO2/α-Fe2O3 (x = 0.04, 0.07, and 0.1) heterogeneous composites were successfully prepared via a two-step solvothermal method. These composites were systematically characterized by the X-ray diffraction technique, field emission scanning electron microscopy, an energy dispersive spectrometer, X-ray photoelectron spectroscopy and a UV-visible spectrometer. It was found that SnO2 nanoparticles were uniformly decorated on the surface of α-Fe2O3 particles in these heterogeneous composites. A comparative study of methylene blue (MB) photodegradation by α-Fe2O3 and x-SnO2/α-Fe2O3 composites was carried out. All x-SnO2/α-Fe2O3 composites showed higher MB photodegradation efficiency than α-Fe2O3. When x = 0.07, the MB photodegradation efficiency can reach 97% in 60 min. Meanwhile, the first-order kinetic studies demonstrated that the optimal rate constant of 0.07-SnO2/α-Fe2O3 composite was 0.0537 min-1, while that of pure α-Fe2O3 was only 0.0191 min-1. The catalytic mechanism of MB photodegradation by SnO2/α-Fe2O3 was examined. The SnO2 can act as a sink and help the effective transfer of photo-generated electrons for decomposing hydrogen peroxide (H2O2) into active radicals. This work can provide a new insight into the catalytic mechanism of the photo-Fenton process.

Enhanced Memristive Performance of Double Perovskite Cs2 AgBiBr6-x Clx Devices by Chloride Doping.

Mixed halide perovskites are promising memristive materials because of their excellent electronic-ionic properties. In this work, lead-free Cs2 AgBiBr6-x Clx (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite films were fabricated using a one-step solution spin-coating method in air. Moreover, the ITO/Cs2 AgBiBr6-x Clx /Al sandwich-like devices are fabricated to investigate the memristive behaviors. The present memristors exhibit nonvolatile and bipolar resistive switching behaviors without electroforming process. Interestingly, as the chloride content increases, the ON/OFF ratio of the device increases from 103 to 104 , the average SET voltage and the RESET voltage decrease from -0.40 V to -0.21 V and from 1.55 V to 1.34 V, respectively. In addition, resistance states of devices can be maintained after 100 switching cycles and 104  s of reading. This study provides new possibility for the development of low-power and environmentally friendly memristors.

Enhanced resistive switching performance in yttrium-doped CH3NH3PbI3 perovskite devices.

In this study, yttrium-doped CH3NH3PbI3 (Y-MAPbI3) and pure CH3NH3PbI3 (MAPbI3) perovskite films have been fabricated using a one-step solution spin coating method in a glove box. X-ray diffractometry and field-emission scanning electron microscopy were used to characterize the crystal structures and morphologies of perovskite films, respectively. It was found that the orientation of the crystal changed and the grains became more uniform in Y-MAPbI3 film, compared with the pure MAPbI3 perovskite film. The films were used to prepare the resistive switching memory devices with the device structure of Al/Y-MAPbI3 (MAPbI3)/ITO-glass. The memory performance of both devices was studied and showed a bipolar resistive switching behavior. The Al/MAPbI3/ITO device had an endurance of about 328 cycles. In contrast, the Al/Y-MAPbI3/ITO device exhibited an enhanced performance with a long endurance up to 3000 cycles. Moreover, the Al/Y-MAPbI3/ITO device also showed a higher ON/OFF ratio of over 103, long retention time (≥104 s), lower operation voltage (±0.5 V) and outstanding reproducibility. Additionally, the conduction mechanism of the high resistance state transformed from space-charge limited current for a Y free device to the Schottky emission after Y doping. The present results indicate that the Al/Y-MAPbI3/ITO device has a great potential to be used in high-performance memory devices.

Interface hybridization and spin filter effect in metal-free phthalocyanine spin valves.

Spin-orbit coupling (SOC) has long been regarded as the core interaction to determine the efficiency of spin conserved transport in semiconductor spintronics. In this report, a spin-valve device with a Co/metal-free phthalocyanine (H2Pc)/Co stacking structure is fabricated. The magnetoresistance effect was successfully obtained in the device. It is also found that the magnetoresistance response is relatively smaller than that of metallic phthalocyanines, clearly implying that SOC is not the key factor to affect the magnetoresistance in phthalocyanine spin-valves. The dominant mechanism that determines the spin transport efficiency in the present H2Pc devices was systemically explored by combining both experimental measurements and first-principles calculation analysis. It was noticed that both the crystalline structure and molecular orientation of the H2Pc layer could be modified by the contact under-layer materials, which changes the magnetization intensity of the ferromagnetic metallic electrode due to the strong interface hybridization of Co/H2Pc. Meanwhile, the theoretical calculations clearly demonstrated that the spin filter effect from the second H2Pc layer should be responsible for the decrease of the magnetoresistance response in the present spin-valves compared to those using metallic phthalocyanine layers. This investigation may trigger new insights into the role of SOC strength and interface hybridization in organic spintronics.

Properties and Applications of the ß Phase Poly(vinylidene fluoride).

Poly(vinylidene fluoride), PVDF, as one of important polymeric materials with extensively scientific interests and technological applications, shows five crystalline polymorphs with α, ß, γ, δ and ε phases obtained by different processing methods. Among them, ß phase PVDF presents outstanding electrical characteristics including piezo-, pyro-and ferroelectric properties. These electroactive properties are increasingly important in applications such as energy storage, spin valve devices, biomedicine, sensors and smart scaffolds. This article discusses the basic knowledge and character methods for PVDF fabrication and provides an overview of recent advances on the phase modification and recent applications of the ß phase PVDF are reported. This study may provide an insight for the development and utilization for ß phase PVDF nanofilms in future electronics.