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Amine salts assisted controllable synthesis of the YVO4:Eu3+ nanocrystallines and their Luminescence properties
摘要： The Eu3+ doped YVO4 nanocrystallines with various morphologies were successfully synthesized by an amines (TETA, ETA and EDA) assisted hydrothermal process. By rationally adjusting the adding amount of TETA, ETA and EDA, the trepang-like, globular-like and pineapple-like Eu3+ doped YVO4 nanostructures can be conventionally obtained. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns indicate that these samples are all of the tetragonal structure. The SEM and TEM results show that the amines additives play an important role in morphology formation. Furthermore, the fluorescence properties of those samples are also systematically studied. Under the excitation of 280 nm, Eu3+ doped YVO4: nanostructures emit strong red fluorescence due to the transitions of 5D1-7F1 and 5D0-7FJ (J =1, 2, 3 and 4) of Eu3+ ions. The intensity of red fluorescence is related to not only the concentrations of Eu3+, but also the types of adding amines. The effective luminescence lifetimes of the trepang-like Y0.9Eu0.1VO4 nanocrystallines, the globular-lik and pineapple-like Y0.95Eu0.05VO4 nanocrystallines are 0.91 ms, 1.02 ms and 1.14 ms, respectively. It is believed that this study is beneficial to promote the development of color display industry.
关键词： hydrothermal,Amine salts,luminescence lifetimes,Eu3+ doped YVO4,fluorescence properties
更新于2025-09-23 15:23:52
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Hybrid fluorescent liquid crystalline composites: directed assembly of quantum dots in liquid crystalline block copolymer matrices
摘要： Hybrid ?uorescent liquid crystalline (LC) composites containing inorganic quantum dots (QDs) are promising materials for many applications in optics, nanophotonics and display technology, combining the superior emission capability of QDs with the externally controllable optical properties of LCs. In this work, we propose the hybrid LC composites that were obtained by embedding CdSe/ZnS QDs into a series of host LC block copolymers of di?erent architectures by means of a two-stage ligand exchange procedure. The ABA/BAB triblock copolymers and AB diblock copolymers with di?erent polymerization degrees are composed of nematogenic phenyl benzoate acrylic monomer units and poly(4-vinylpyridine) blocks, which are capable of binding to the QD surface. Our results clearly show that the spatial distribution of QDs within composite ?lms as well as the formation of QD aggregates can be programed by varying the structure of the host block copolymer. The obtained composites form a nematic LC phase, with isotropization temperatures being close to those of the initial host block copolymers. In addition, the in?uence of the molecular architecture of the host block copolymers on ?uorescence properties of the obtained composites is considered. The described strategy for the QD assembly should provide a robust and conventional route for the design of highly ordered hierarchical hybrid materials for many practical applications.
关键词： liquid crystalline block copolymer matrices,ligand exchange procedure,fluorescence properties,CdSe/ZnS QDs,nematic LC phase,Hybrid ?uorescent liquid crystalline composites,quantum dots
更新于2025-09-23 15:19:57
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Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds
摘要： Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds is an important factor for their use in medical and sensor applications. However, reports providing a deep understanding of the potential factors influencing these properties are rare and focus only on a few influencing factors. The current contribution targets this issue and we report a comprehensive study of the fluorescence properties of NVs in nanodiamonds as a function of electron irradiation fluence and surface termination. Here we show that process parameters such as defect center interactions, in particular, different nitrogen defects and radiation induced lattice defects, as well as surface functionalities have a strong influence on the fluorescence intensity, fluorescence lifetime and the charge state ratio of the NV centers. By employing a time-correlated single photon counting approach we also established a method for fast macroscopic monitoring of the fluorescence properties of ND samples. We found that the fluorescence properties of NV centers may be controlled or even tuned depending upon the radiation treatment, annealing, and surface termination.
关键词： fluorescence lifetime,charge state ratio,nanodiamonds,surface termination,nitrogen vacancy centers,fluorescence properties,electron irradiation
更新于2025-09-19 17:15:36
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Preparation of multicolored carbon quantum dots using HNO <sub/>3</sub> /HClO <sub/>4</sub> oxidation of graphitized carbon
摘要： The microstructure of carbon quantum dots (CQDs) has a great influence on their fluorescence properties. Here, different microstructures of CQDs were synthesized by the selective oxidation of graphitized activated carbon using HNO3/HClO4 as the oxidant. We characterized the microstructure and surface chemistry of the CQDs, and the results show that the degree of graphitization of activated carbon has a significant effect on the structure and fluorescence properties of the obtained CQDs. The fluorescence of the CQD solution can be tuned from yellow to green by regulating the degree of graphitization of the activated carbon by heat treatment at high temperature (up to 2500 °C). Moreover, the increased degree of graphitization of the raw carbon precursor is beneficial for significantly reducing the fluorescence self-absorption quenching of the concentrated CQD solution. Importantly, the as-prepared CQDs have no cytotoxicity and can be used as bioimaging agents.
关键词： fluorescence properties,graphitization,bioimaging,carbon quantum dots
更新于2025-09-12 10:27:22
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Non-linear changes of performances caused by introduction of chloride ions into Er3+-doped fluorozirconate glass
摘要： The effect of chloride ions on the properties of Er3+-doped fluorozirconate glass is systematically studied. We first observed a nonlinear mutation of the glass-forming abilities and fluorescence properties of glass when 1 mol% fluoride ions were replaced by chloride ions. The results differed from previous reports. In order to explain this special phenomenon, we investigated the changes of the structure and the Judd-Ofelt theory of glass before and after halogen anion substitution. The results indicate that part of the fluorozirconium octahedral network was destroyed and transformed into a chain structure due to the bridging chlorine atoms, of which the electronegativity is lower than F-. With the increase of Cl-, the glass-forming abilities gradually recovered due to the decrease of the liquid’s temperature. Therefore, a non-linear mutation of the glass-forming abilities was exhibited. Furthermore, the predictor χ, the ratio between the Judd–Ofelt parameters ??4 and ??6, and the reduction in phonon density caused a mutation on the fluorescence properties of glass, such as the intensity and lifetime. This research could provide a new reference for the anion modification of fluoride glass.
关键词： Non-linear changes,Halide glasses,Fluorescence properties,Thermal stability
更新于2025-09-11 14:15:04
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A three-dimensional Zn <sup>II</sup> coordination network based on 5,5′-methylenebis(2,4,6-trimethylisophthalic acid) and 2,7-bis(1 <i>H</i> -imidazol-1-yl)fluorene: synthesis, structure and luminescence properties
摘要： In recent years, coordination polymers constructed from multidentate carboxylate ligands and N-containing ligands have attracted much attention since these ligands can adopt a rich variety of coordination modes which can lead to crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[diaqua[μ-2,7-bis(1H-imidazol-1-yl)fluorene-κ2N3:N3′][μ-5,5′-methylenebis(2,4,6-trimethylisophthalato)-κ2O1:O1′]zinc(II)] hemihydrate], {[Zn(C23H22O8)(C19H14N4)(H2O)2]·0.5H2O}n, 1, was prepared by the self-assembly of Zn(NO3)2·6H2O with 5,5′-methylenebis(2,4,6-trimethylisophthalic acid) (H4BTMIPA) and 2,7-bis(1H-imidazol-1-yl)fluorene (BIF) under solvothermal conditions. The structure of 1 was determined by elemental analysis, single-crystal X-ray crystallography, powder X-ray diffraction, IR spectroscopy and thermogravimetric analysis. Each ZnII ion is six-coordinated by two O atoms from two H2BTMIPA2? ligands, by two N atoms from two BIF ligands and by two water molecules, forming a distorted octahedral ZnN2O4 coordination geometry. Adjacent ZnII ions are linked by H2BTMIPA2? ligands and BIF ligands, leading to the formation of a two-dimensional (2D) (4,4)-sql network, and intermolecular hydrogen-bonding interactions connect the 2D layer structure into the three-dimensional (3D) supramolecular structure. Each 2D layer contains two kinds of helices with the same direction, which are opposite in adjacent layers. The luminescence properties of complex 1 in the solid state have also been investigated.
关键词： crystal structure,fluorescence properties,two-dimensional coordination polymer,supramolecular,5,5′-methylenebis(2,4,6-trimethylisophthalic acid,zinc(II),2,7-bis(1H-imidazol-1-yl)fluorene,hydrogen bonding
更新于2025-09-04 15:30:14