Preparation of Tetraethylenepentamine Modified Magnetic Graphene Oxide for Adsorption of Dyes from Aqueous Solution

<div><p>In this study, tetraethylenepentamine modified magnetic graphene oxide nanomaterial (TMGO) was prepared and characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and vibration sample magnetometer (VSM). All the characterizations proved that the modification and preparation of TMGO were successful. The TMGO nanomaterial was used in the adsorption of Acid Red 18 (AR) in aqueous solution. The parameters like pH of solution, adsorption kinetics and isotherms were all investigated. The results indicated that the TMGO nanomaterial had satisfied adsorption ability and the maximum adsorption capacity was 524.2 mg g -1 at 45 °C and pH 6. The adsorption capacity remained at 91.8% of the initial value after five cycles. The adsorption process with AR was found through fitting the pseudo-second-order kinetics equations and the Freundlich adsorption model. The experimental results demonstrated that the TMGO nanomaterial could be rapidly extracted from the medium and had a good adsorption ability to remove dyes in wastewater.</p></div

Halide Perovskites for Resistive Switching Memory

Resistive switching random access memory (RRAM), also known as memristor, is regarded as an emerging nonvolatile memory and computing-in-memory technology to address the intrinsic physical limitations of conventional memory and the bottleneck of von Neumann architecture. In particular, halide perovskite RRAMs have attracted widespread attention in recent years because of their ionic migration nature and excellent photoelectric properties. This Perspective first provides a condensed overview of halide perovskite RRAMs based on materials, device performance, switching mechanism, and potential applications. Moreover, this Perspective attempts to detail the challenges, such as the quality of halide perovskite films, the compatible processing of device fabrication, the reliability of memory performance, and clarification of the switching mechanism, and further discusses how the outstanding challenges of halide perovskite RRAMs could be met in future research

Synthesis of Zn-Doped AgInS₂ Nanocrystals and Their Fluorescence Properties

AgInS₂ nanocrystals have attracted intense attention due to their promising applications in printable solar cells, light-emitting diode (LED), and biological labeling. Although much effort has been made to develop various synthesis methods to prepare AgInS₂ nanocrystals, it remains a goal to obtain high quality AgInS₂ nanocrystals. In this work, Zn-doped AgInS₂ nanocrystals were synthesized by diffusing Zn into the preformed AgInS₂ seeds at high temperature in solution. The resulting Zn-doped AgInS₂ nanocrystals had well-defined spherical morphology with narrow size distribution. By varying the reaction temperature, the emission wavelengths of the obtained Zn-doped AgInS₂ nanocrystals could be adjusted from 520 to 680 nm. The quantum yield of the obtained alloyed nanocrystals could reach 41%, which was reasonably good as compared to those of the previously reported. The obtained Zn-doped AgInS₂ nanocrystals showed promising applications in cell labeling

Enhanced Resistive Switching Performance through Air-Stable Cu₂AgSbI₆ Thin Films for Flexible and Multilevel Storage Application

Herein, the lead-free halide perovskite films with different Cu-to-Ag ratios (Cu3–xAgxSbI6, x = 0, 1, 2, or 3) have been prepared by a spin-coating method at low temperature. The enhanced resistive switching (RS) performance of more uniform SET/RESET voltages and the endurance up to at least 1600 cycles are found in the RS memory with a device structure of Ag/PMMA/Cu2AgSbI6/ITO. The device performance is not degraded under different bending angles and after 103 bending cycles, which is beneficial for flexible memory applications. The appropriately increased activation energy of the perovskites with the partial substitution of Ag atoms, which would lead to a more robust filament formed, is proposed to explain the enhanced RS mechanism. Importantly, the effective size and number of filaments measured by conductive AFM are introduced to confirm the multilevel storage effect of Cu2AgSbI6. The multilevel storage characteristics with four resistance levels are demonstrated by various compliance currents. Moreover, the Cu2AgSbI6 memory devices still exhibit enhanced RS properties and multilevel storage after 75 days of exposure to ambient conditions. Our study provides a strategy for improving the stability and high-density storage applications of halide perovskite RS memory devices

Synthesis of ZnO Nanoparticles with Tunable Emission Colors and Their Cell Labeling Applications

ZnO nanoparticles have been studied for potential cell labeling applications over the past several years. However, little progress has been made because of the limited emission color and poor water stability of ZnO nanoparticles. In this work, ZnO nanoparticles with various emission colors, including blue, green, yellow, and orange, were synthesized through an ethanol-based precipitation method. The emission color of the ZnO nanoparticles could be tuned by adjusting the pH value of the precipitation solution. The as-prepared ZnO nanoparticles were then encapsulated with silica to form ZnO@silica core shell nanoparticles, to improve the water stability of the ZnO nanoparticles. The visible emissions of the ZnO nanoparticles were well retained after they had been coated with silica shells. The resultant ZnO@silica core shell nanoparticles exhibited low cytotoxity and were promising in cell labeling applications

One-Pot Synthesis of Water-Stable ZnO Nanoparticles via a Polyol Hydrolysis Route and Their Cell Labeling Applications

ZnO nanoparticles have been identified as a new generation of biofriendly cell labeling agents since they are nontoxic, less expensive, and chemically stable in air. However, ZnO nanoparticles show poor water stability due to high equilibrium concentration of Zn species in water in a wide pH range. In this work, a one-pot polyol hydrolysis method was developed for synthesizing water-stable ZnO nanoparticles with blue emission. The as-synthesized ZnO nanoparticles were hydrophilic and stable in water, even at basic or acidic aqueous conditions. The PL properties of the ZnO nanoparticles stored at various pH values (i.e., 4.5−11) could be preserved for at least 3 days. The good water stability of the ZnO nanoparticles was offered by the surface attachment of an ester compound, which was formed as a result of the reaction between the stearic acid and triethylene glycol (TREG). This method provides a new approach to synthesize water-stable ZnO nanoparticles. The resultant ZnO nanoparticles demonstrated promising applications in cell labeling

Light-Mediated Multilevel Flexible High-Efficiency Perovskite Resistive Switching Memory Based on Mn:CsPbCl₃ Nanocrystals

Herein, the electrical characteristics, photoelectric properties, resistive switching (RS) mechanism, and flexible storage application of Ag/PMMA&Mn:CsPbCl3/ITO (PMMA = poly(methyl methacrylate)) devices are studied by using the photoelectric material Mn:CsPbCl3 nanocrystals (NCs) embedded in PMMA as the RS layer. The devices exhibit bipolar RS behavior with low operating voltage, excellent cycling endurance (>1000 times), long retention time (≥104 s), high ON/OFF ratio (≈104), and good environmental stability. The flexible memory devices have demonstrated reliable mechanical stability of consecutive 1000 bending cycles. In addition, multilevel data storage is realized by introducing the UV light, and the adjustive resistive switching characteristics is achieved through photoelectric synergistic work. The resistive switching mechanism under the excitation of light has been studied comprehensively. This work may pave a new way for developing the next generation of high-density data storage and photoelectric memristor

Data_Sheet_1_CsPbBr3/CdS Core/Shell Structure Quantum Dots for Inverted Light-Emitting Diodes Application.docx

Novel CsPbBr3/CdS core/shell structure quantum dots (QDs) were successfully synthesized using a facile hot-injection method. The corresponding CsPbBr3/CdS QDs based light-emitting diodes (QLEDs) were further prepared, which demonstrated the maximum luminance of 354 cd/m2 and an external quantum efficiency (EQE) of 0.4% with the current efficiency (CE) of 0.3 cd/A. Moreover, the optoelectronic performance of the CsPbBr3/CdS QDs based QLEDs exhibited a comparable enhancement in contrast to the pure CsPbBr3 QDs based QLEDs. Hypothetically, the novel CsPbBr3/CdS structure QDs introduced one new route for advanced light emission applications of perovskite materials.</p

Highly Thermally Sensitive Cascaded Wannier–Mott Exciton Ionization/Carrier Localization in Manganese-Doped Perovskite Nanocrystals

Transition-metal doping in perovskite nanocrystals strongly alters the photophysical properties of these nanocrystals. However, the details of the underlying thermal and optical processes within such an intriguing symmetry-breaking nanosystem are far from clear. Herein, we study the sensitively temperature-dependent and highly competent delocalized exciton and transition-metal ion-captured carrier recombination processes in manganese-doped CsPbBr0.6Cl2.4 nanocrystals. The combined experimental and theoretical studies reveal that both the exciton ionization and capture of the band-edge carriers by the manganese ions play the dominant roles in determining the proportion of the manganese ions-dominated recombination process. A density functional theory calculation of the temporal fluctuation of the manganese ions-accommodated localized orbitals further confirms that the thermally enhanced nonadiabatic electron–phonon coupling promotes the probability of the carrier localization. These findings reveal the respective crucial roles of the exciton ionization and carrier capture in the localized recombination process in the transition-metal-doped semiconductor nanocrystals