Project description:Amorphous materials with non-periodic structures are commonly evaluated based on their chemical composition, which is not always the best parameter to evaluate physical properties, and an alternative parameter more suitable for performance evaluation must be considered. Herein, we quantified various structural and physical properties of Ce-doped strontium borate glasses and studied their correlations by principal component analysis. We found that the density-driven molar volume is suitable for the evaluation of structural data, while chemical composition is better for the evaluation of optical and luminescent data. Furthermore, the borate-rich glasses exhibited a stronger luminescence due to Ce3+, indicating a higher fraction of BO3/2 ring and larger cavity. Moreover, the internal quantum efficiency was found to originate from the local coordination states of the Ce3+ centres, independent of composition or molar volume. The comparison of numerical data of the matrix is useful not only for ensuring the homogenous doping of amorphous materials by activators, but also for determining the origin of physical properties.
Project description:New glass compositions containing high concentrations of Tb3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100 - x)(41GeO2-25B2O3-4Al2O3-10Na2O-20BaO) - xTb4O7. Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb3+ ions confirmed the homogeneous distribution of Tb3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 °C). An optical fiber was manufactured by a fiber drawing process. The UV-Vis spectra of the glasses showed Tb3+ electronic transitions and optical windows varying from 0.4 to 1.6 μm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (VB) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum VB values obtained at 650 and 1550 nm for the glass with x = 18 mol% were -128 and - 17.6 rad T-1 m-1, respectively. The VB values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb4O7 were - 110.2 and - 9.5 rad T-1 m-1, respectively, while the optical loss at around 880 nm was 6.4 dB m-1.
Project description:Ce(3+)-doped yttrium aluminum garnet (YAG:Ce) nanocrystals were successfully synthesized via a facile sol-gel method. Multiple characterization techniques were employed to study the structure, morphology, composition and photoluminescence properties of YAG:Ce nanophosphors. The YAG:Ce0.0055 sintered at 1030?°C exhibited a typical 5d(1)-4f(1) emission band with the maximum peak located at 525?nm, and owned a short fluorescence lifetime ?1 (~28?ns) and a long fluorescence lifetime ?2 (~94?ns). Calcination temperature and Ce(3+) doping concentration have significant effects on the photoluminescence properties of the YAG:Ce nanophosphors. The emission intensity was enhanced as the calcination temperature increased from 830 to 1030?°C, but decreased dramatically with the increase of Ce(3+) doping concentration from 0.55 to 5.50 at.% due to the concentration quenching. By optimizing the synthesized condition, the strongest photoluminescence emission intensity was achieved at 1030?°C with Ce(3+) concentration of 0.55 at.%.
Project description:The paper presents sorption behavior of Arachis hypogaea shells towards silver ions and possibility of their use as antimicrobial product. During the modification process of the natural sorbent, equilibrium tests were carried out. Moreover, the possibility of obtaining biocomposite Arachis hypogaea shells/nAg has been determined, and its antimicrobial properties have been evaluated. Additionally, sorption kinetics has been calculated. In the last step, silver ions were desorbed. The conducted equilibrium tests allowed to adjust the sorption isotherm model and determine the sorption capacity of tested material. This process is best described by Freudlich's isotherm, and the sorption capacity is equal to 12.33 mg/g. On the basis of kinetic studies, the chemical nature of this process has been proved (by choosing a pseudo-second order model for the sorption process). It has been confirmed that the obtained peanut shells modified with silver ions have antimicrobial properties. The tests allowed to obtain 100% inhibition of Aspergillus niger and ~?98% Escherichia coli.
Project description:A new series of Ce3+, Tb3+ singly doped and Ce3+/Tb3+ co-doped NaZnPO4 (NZPO) phosphors have been synthesized via a high-temperature solid-state reaction method at 800 °C. The crystal cell structure, luminescence proprieties, energy transfer, and chromaticity coordinates of the as-prepared phosphors were investigated in detail. The photoluminescence spectra of NZPO:Ce3+ phosphors exhibited broad emission in the 300-380 nm range, while under UV excitation, the singly doped NZPO:Tb3+ phosphor showed emission peaks at ∼485-690 nm among which the green emission peak appears at ∼543 nm. The Tb3+ green emission was significantly enhanced almost 20 times via energy transfer from Ce3+ to Tb3+. The energy transfer (ET) mechanism from Ce3+ to Tb3+ in NZPO is identified to be a resonant type via the dipole-dipole interaction mechanism with an ET efficiency of 91%. Intense green emission is obtained at very low Tb3+ concentrations under 285 nm excitation, making NZPO:Ce3+/Tb3+ an efficient UV-excited green phosphor. The NaZnPO4:Ce3+/Tb3+ phosphors are promising UV convertible materials of green light for UV -LEDs applications.
Project description:Hollow noble metal nanoparticles have excellent performance not only in surface catalysis but also in optics. In this work, the hollow Au-Ag alloy nanorices are fabricated by the galvanic replacement reaction. The dark-field spectrum points out that there is a big difference in the optical properties between the pure Ag nanorices and the hollow alloy nanorices that exhibit highly tunable localized surface plasmon resonances (LSPR) and that possess larger radiative damping, which is also indicated by the finite element method. Furthermore, the surface enhanced Raman scattering (SERS) and oxidation test indicate that hollow Au-Ag alloy nanorices show good anti-oxidation and have broad application prospects in surface-plasmon-related fields.
Project description:In this study, lanthanum aluminosilicate glasses with compositions of 45SiO2-20Al2O3-12.5LaF3-10BaF2-9K2O-1Cr2O3-2.5Yb2O3 (SALBK) were prepared using the conventional melting method and copper-potassium ion exchange process. Influences of the ion exchange process between copper and potassium on the visible, upconversion, and near-infrared luminescence spectra of Cr3+/Yb3+ co-doped under excitations of 343, 490, and 980 nm LD were investigated. The EDS analysis of SALBK glasses was measured to confirm the presence of atoms in the glasses. The values of direct and indirect bandgaps of Cr3+/Yb3+ co-doped SALBK glasses were calculated and analyzed. Besides, the energy exchange processes between Cu+, Cu2+ ions, and Cr3+, Yb3+ ions were also proposed and discussed.
Project description:The reactions of the cyclo-As5 complex [Cp*Fe(η5 -As5 )] (B) with the AgI and CuI salts of the weakly coordinating anion (WCA) [FAl{OC6 F10 (C6 F5 )}3 ]- ([FAl]- ) are studied. These reactions allow the synthesis of the mononuclear complexes [M(η5 : η2 -B)2 ][FAl] (M=Ag (1), Cu (2)) when a ratio of B/M(FAl) 2 : 1 is used. Compound 1 shows an unusual disorder of the central AgI cation between two π-coordinating cyclo-As5 ligands, which is absent in 2 pointing to a weak interaction of the Ag center towards the cyclo-As5 ligands in B. When the ratio of B/Ag(FAl) is changed to 3 : 1 or 1 : 1, the respective coordination compounds [Ag(η2 -B)3 ][FAl] (3) and [Ag2 (η2 : η2 -B)2 ][FAl]2 (4) are accessible. The coordination modes of the cyclo-As5 units in 1, 3 and 4 are all different, reflecting the adaptive coordination behavior of B towards AgI ions. The optimized geometries in the gas phase of 1-4 are determined by DFT calculations to support the bonding situation observed in their solid-state structures.
Project description:A novel and effective method to improve scintillation properties of glass-ceramics, such as intensity enhancement and decay-time shortening, is reported in this work. Compared with crystal scintillators, glass scintillators always have the problems of low efficiency and long decay; how to solve them has always been a scientific puzzle in the field of scintillation glass-ceramics. The plasma enhancement effect can be predicted to solve the above problems. Ag+ ions were diffused into glasses by ion exchange, and then Ag nanoparticles and CsPbBr3 quantum dots were formed by heat treatment. The structure of the CsPbBr3 perovskite consists of a series of shared corner PbBr6 octahedra with Cs ions occupying the cuboctahedral cavities. By using Ag and the plasma resonance effect, the photoluminescence intensity of CsPbBr3 quantum dot glasses was enhanced by 3 times, its radioluminescence intensity increased by 6.25 times, and its decay time was reduced by a factor of more than one. Moreover, the mechanism of photoluminescence and radioluminescence enhanced by Ag and plasma was discussed based on the experimental results and finite-difference time-domain method. We concluded that the increase in radioluminescence intensity was related to plasma enhancements and the energy exchange between Ag nanoclusters and CsPbBr3 quantum dots. Doping Ag is a valid means to improve the scintillation luminescence of CsPbBr3 quantum dot glasses, which can be applied in the field of scintillation.
Project description:Plasmonic metal nanoparticles are efficient light harvesters with a myriad of sensing- and energy-related applications. For such applications, the optical properties of nanoparticles of metals such as Cu, Ag, and Au can be tuned by controlling the composition, particle size, and shape, but less is known about the effects of oxidation on the plasmon resonances. In this work, we elucidate the effects of O adsorption on the optical properties of Ag particles by evaluating the thermodynamic properties of O-decorated Ag particles with calculations based on the density functional theory and subsequently computing the photoabsorption spectra with a computationally efficient time-dependent density functional theory approach. We identify stable Ag nanoparticle structures with oxidized edges and a quenching of the plasmonic character of the metal particles upon oxidation and trace back this effect to the sp orbitals (or bands) of Ag particles being involved both in the plasmonic excitation and in the hybridization to form bonds with the adsorbed O atoms. Our work has important implications for the understanding and application of plasmonic metal nanoparticles and plasmon-mediated processes under oxidizing environments.