Crystallization-based upcycling of iron oxyhydroxide for efficient arsenic capture in contaminated soils.

Arsenic (As)-contaminated soil inevitably exists in nature and has become a global challenge for a sustainable future. Current processes for As capture using natural and structurally engineered nanomaterials are neither scientifically nor economically viable. Here, we established a feasible strategy to enhance As-capture efficiency and ecosystem health by structurally reorganizing iron oxyhydroxide, a natural As stabilizer. We propose crystallization to reorganize FeOOH-acetate nanoplatelets (r-FAN), which is universal for either scalable chemical synthesis or reproduction from natural iron oxyhydroxide phases. The r-FAN with wide interlayer spacing immobilizes As species through a synergistic mechanism of electrostatic intercalation and surface chemisorption. The r-FAN rehabilitates the ecological fitness of As-contaminated artificial and mine soils, as manifested by the integrated bioassay results of collembolan and plants. Our findings will serve as a cornerstone for crystallization-based material engineering for sustainable environmental applications and for understanding the interactions between soil, nanoparticles, and contaminants.

Mechanistic insights on the electronic properties and electronic/atomic structure aspects in orthorhombic SrVO3 thin films: XANES-EXAFS study.

Correlations among the B-O6 octahedra distortions, existing polymorphous phases, band structures and electronic conductivities of ABO3 perovskites are matters for debate and require a deep understanding of their local atomic/electronic structures and diverse assets. In this study, to illustrate the distortion in V-O6 octahedra and its implication on the band structure and electronic properties, spectroscopic investigations on the RF-sputtering grown insulating SrVO3 thin films were employed using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). V K-edge and V L3,2-edge XANES, along with atomic multiplet calculations, have confirmed the 4+ oxidation state of V ions in the pristine and annealed SrVO3 thin films. Lower t2g/eg peak intensity ratio and smaller energy separation between t2g and eg peaks in the O K-edge XANES spectra, compared to the VO2 reference sample, have confirmed a larger V-O6 distortion in the orthorhombic SrVO3 thin films. Moreover, from the EXAFS data analysis, the local orthorhombic structure has been identified in the pristine and annealed SrVO3 thin films, compelling significant distortion in the V-O6 octahedra. Dimerization in the vanadium chains and V-V twisting, caused by V-O6 octahedra distortion, manifests a miscellaneous ligand field interaction between O 2p and V 3d orbitals and facilitates (i) a larger separation between the bonding and antibonding d‖ orbitals and (ii) an upward shift of the π* band in the band structure, leading to larger band gaps in the insulating SrVO3 thin films. Our spectroscopy results may open up new avenues for the mechanism of insulating/conducting character in other complicated perovskite materials using XANES-EXAFS.

Emissive CdTe/ZnO/GO quasi-core-shell-shell hybrid quantum dots for white light emitting diodes.

Colloidal quantum dots (QDs) have been extensively studied for optoelectronic and biological applications due to their unique physical and optical properties. In particular, among the optoelectronics applications, the white light emitting diode (WLED) has great potential in flat panel displays and solid-state lighting. Herein, we demonstrate a novel, facile, and efficient technique for the synthesis of CdTe/ZnO/GO quasi-core-shell-shell hybrid quantum dots containing the CdTe core with multi shells of ZnO and graphene oxide (GO) and fabrication of WQDLEDs. The CdTe/ZnO/GO quasi-core-shell-shell QDs have a unique strong photoluminescence (PL) peak at 624 nm related to the CdTe core and new weak peaks at 382, 404, 422, and 440 nm due to conjugation with ZnO and GO. Also, in the electroluminescence (EL), multiple emission peaks are observed, which can be correlated to the recombination process inside the CdTe core and also recombination of electrons in the lowest unoccupied molecular orbital (LUMO) and LUMO+2 of GO and holes in the valence band (VB) of ZnO. The QDLEDs show clear white color emission with a maximum luminance value of about 480 cd m-2 with Commission Internationale de l'Eclairage (CIE) color coordinates of (0.35, 0.28).