Ce 3+ /Er 3+ /Bi 3+ triply-doped yttrium aluminum garnet (YAG) is synthesized using co-precipitation method.The Bi 3+ concentration-dependent near-infrared (NIR) emission behavior is systemically investigated.The NIR emission of Er 3+ ions at 1531 nm is enhanced threefold by the addition of 7 mol% Bi 3+ .Bi 3+ doping results in the formation of exciton in YAG and the variation in the local environment of the doped rare-earth ions.The enhancement in NIR luminescence is ascribed to the combined effects of the sensitization of exciton→Ce 3+ →Er 3+ and the Bi 3+ doping-induced adjustment of the local environment for Ce 3+ and Er 3+ ions.
Li+-doped HoPO4 powders with a pure tetragonal phase are successfully synthesized by the co-precipitation method. It exhibits an obvious color change under sunlight and tri-phosphor fluorescent light illumination. The introduction of Li+ ions into HoPO4 can further enhance its photochromic property effectively. The doped Li+ ions induce changes in the crystal structure. The spectral characteristics and thus photochromic properties of HoPO4 are explored. The improved HoPO4 powder, when used as a photochromic material, has wide-ranging prospects in security, decoration, and other applications.
As potential green alternatives to conventional organic solvents, ionic liquids (ILs) have gained extensive investigations in biocatalytic applications for over a decade. Recently, deep eutectic solvents (DESs), a new class of IL-related solvents, have emerged as a promising new reaction medium for biotransformation. DESs are simply formed by mixing an ammonium salt (such as choline chloride) and a hydrogen-bond donor (such as urea and glycerol) through thermal mixing or freeze-drying. They share some attractive IL-like solvent properties such as melting point below room temperature, low volatility, high thermal stability, high solubility for various substances, and, more importantly, the "designer solvent" property. The advantages of using DESs over the use of conventional ILs include low cost, easy preparation with high purity, high biodegradability, and low toxicity. Encouraging results have been obtained in the utilization of DESs as solvent/cosolvent for biotransformation. In this chapter, we discuss the physicochemical properties of DESs; we review the use of DESs as a new reaction medium for biocatalytic transformation, either as such or as a cosolvent in aqueous solution; and we introduce a new type of DESs, natural deep eutectic solvents (NADESs), that have an enormous potential for applications due to their nontoxicity, sustainability, and environmental friendliness.
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