掺锗SiO2 玻璃的发光现象

掺锗SiO2 玻璃的发光现象;Ge/SiO2玻璃;Ge纳米晶粒;溶胶-凝胶;光致发光     

有机改性先驱体对含铕配合物的凝胶玻璃结构及性能的影响

分别采用γ-缩水甘油氧基三甲氧基硅烷(CH₂OCHCH₂O(CH₂)₃Si(OCH₃)₃) (GPTMS), 甲基三甲氧基硅烷(MTMS)和乙烯基三乙氧基硅烷(VTES)作为有机改性先驱体, 采用原位合成技术, 用溶胶-凝胶法制备了Eu^3＋, β-二酮噻吩甲酰三氟丙酮(TTA)及协同体1,10-菲啰啉(phen)共掺的三种有机改性二氧化硅(ormosil)玻璃. 测量了它们的发射光谱和红外光谱, 并进行了XRD, SEM和TG-DSC测试. 探讨了不同有机改性先驱体及热处理温度对原位合成的稀土有机配合物掺杂二氧化硅凝胶玻璃的发光性能、热稳定性及机械性能的影响. 结果表明, 有机改性先驱体能使凝胶玻璃结构致密, 但同时热稳定性降低; 对于荧光性能, MTMS和VTES可使其有一定的提高, 但它们的最大含量不能超过50%, 否则凝胶易失透, 而GPTMS能大幅提高凝胶的荧光性能. 通过综合比较, 选取出各种性能都较好的配方, 为今后制备较实用的具有较强荧光的含铕的凝胶玻璃提供了一定的依据.     

Luminescence 3D-ordered porous materials composed of CdSe and CdTe nanocrystals

The luminescence porous materials of CdTe or CdSe nanocrystals (NCs) were prepared by filling the corresponding NCs into the voids of colloidal crystal by co-deposition of polymer beads and NCs. After removing the beads with tetrahydrofuran (THF), the 3D-ordered porous materials of CdTe (or CdSe) NCs were obtained. The wavelength of maximum photoluminescence of the NCs porous material shows obvious red shift compared with their aqueous dispersion. Under the excitation of high-energy electron the porous materials of CdTe and CdSe NCs will emit photons that can be collected to form a cathode luminescence (CL) image.     

NaTaO3及NaTaO3∶Bi3+光催化剂的光致发光光谱研究

采用光致发光光谱技术对一系列不同条件下制备的NaTaO3及不同掺杂量的NaTaO3∶Bi3+进行了研究. 结果表明, NaTaO3的发光性质与其制备条件密切相关: 在钠离子不足的条件下合成的样品, 其发光带主要位于515和745 nm左右; 而在钠离子充足条件下合成的样品, 其发光带位于460 nm左右, 随着n(Na)/n(Ta)的降低, 发光带向长波长方向移动; 掺入Bi3+之后, 其发光峰由515 nm移至455 nm, 随着Bi3+掺入量的增加, 455 nm的发光带强度减弱. 515 nm的发光带与替位缺陷TaNa....相关; 745 nm的发光带与VNa`缺陷相关; 而460 nm的发光带与本征TaO6基团相关. 将Bi3+掺入到钽酸钠样品, TaNa....由BiNa..替代, 相应的发光带向高的n(Na)/n(Ta)方向移动, 从而呈现出本征TaO6基团的发光带.     

Properties of Luminescent Si Nanoparticles in Sol-Gel Matrices

In this wor e preparation and properties of silica sol-gels incorporating luminescent Si nanocrystallites extracted from porous Si are described for the first time. These sol-gel/Si nanocrystallite composite materials are characterized by BET isotherm measurements, photoluminescence spectroscopy, and infrared spectroscopy. To stabilize the photoluminescence (PL) of Si crystallites within the silica matrix, a fatty acid (capric (C₁₀), myristic (C₁₄) or arachidic acid (C₂₀)) is added as a passivation agent during the hydrolysis of tetraethoxysilane. The presence of the fatty acid is crucial to the long-term stability of the Si nanocrystallite luminescence, as the Si visible light emission remains essentially unchanged for more than a month when the fatty acid is present in the mixture but degrades quickly (within days) when absent. The thermal stability of the Si luminescence within the sol-gel is also reported. Fluorescence microscopy reveals that the light-emitting Si crystallites aggregate into micron-sized domains somewhat unevenly throughout the silica matrix. This distribution of Si crystallites can be improved by employing a surfactant, dioctyl sodium sulfosuccinate (DSS).     

Photodegradation of aramids. I. Irradiation in the absence of oxygen

The photolysis reactions of a series of isomeric fully aromatic polyamides (aramids) have been investigated in the absence of oxygen by ultraviolet and luminescence spectroscopy. Several of the aramids were found to undergo photo-Fries rearrangements to give 2-aminobenzophenone backbone units when irradiated either as films, fibers, or dissolved in liquids. Quantum yields for this rearrangement were low, < 1 × 10^?6 mole/einstein, and increased with decreasing aramid glass transition temperature and increasing backbone mobility. The formation of gel, carbon monoxide, and a strong ESR signal were consistent with a free-radical mechanism for the rearrangement.     

Soluble rigid–flexible polyethers containing bis(biphenyl)anthracene or bis(styryl)anthracene units in the main chain for light-emitting applications

New rigid–flexible polyethers containing bis(biphenyl)anthracene or bis(styryl)anthracene units in the main chain were synthesized and characterized by viscosimetry, thermal and mechanical analysis, NMR, UV-vis, and luminescence spectroscopy. The polyethers containing bis(styryl)anthracene units in the main chain form free-standing films either from solution casting or after melt pressing at temperatures where they are thermally stable. The length of the flexible spacer influences the thermal and mechanical behavior of these polymers. The isotropization temperature as well as the glass transition temperature show an odd–even effect depending on the spacer segment length. Films with high modulus at room temperature and glass transition temperatures in the range 74–103°C were obtained using dynamic mechanical analysis. These polymers show bright-yellow photoluminescence with maximum at 580 nm in solution. In the solid state, the luminescence maximum is either red or blue shifted depending on the number of the methylene units in the aliphatic segment. The polyethers containing bis(biphenyl)anthracene units in the main chain are blue-light-emitting polymers with photoluminescence maxima at 435 and 455 nm in solution. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3826–3837, 1999     

Luminescence database I--minerals and materials.

A luminescence database for minerals and materials has been complied from the literature, the aim being to create a resource that will aid in the analysis of luminescence spectral of ionic species in minerals and materials. The database is based on a range of excitation techniques and records both major and minor lines, and their activators. The luminescence techniques included in the database are cathodoluminescence, ion luminescence, and photoluminescence. When combined with other traditional X-ray measurements collected on the same region, use of the luminescence database will give additional insight into the chemistry of minerals and materials.     

NaTaO_3及NaTaO_3∶Bi~(3+)光催化剂的光致发光光谱研究

采用光致发光光谱技术对一系列不同条件下制备的NaTaO3及不同掺杂量的NaTaO3∶Bi3 进行了研究.结果表明,NaTaO3的发光性质与其制备条件密切相关在钠离子不足的条件下合成的样品,其发光带主要位于515和745nm左右;而在钠离子充足条件下合成的样品,其发光带位于460nm左右,随着n(Na)/n(Ta)的降低,发光带向长波长方向移动;掺入Bi3 之后,其发光峰由515nm移至455nm,随着Bi3 掺入量的增加,455nm的发光带强度减弱.515nm的发光带与替位缺陷Ta.N.a..相关;745nm的发光带与VN`a缺陷相关;而460nm的发光带与本征TaO6基团相关.将Bi3 掺入到钽酸钠样品,TaN..a..由BiN..a替代,相应的发光带向高的n(Na)/n(Ta)方向移动,从而呈现出本征TaO6基团的发光带.     

Enhanced NIR Luminescence of Nanozeolite L Loading Lanthanide β‐Diketonate Complexes

Herein, we report the preparation of zeolite NIR luminescence materials with a remarkable increase of luminescence intensity by attaching stopper molecule (an imidazolium salt) to the channel entrances of zeolite L loading with NIR lanthanide (Er³⁺ or Nd³⁺) β‐diketonate complexes. This results from the formation of Ln³⁺‐β‐diketonate complexes (Ln=Er or Nd) with high coordination numbers through the decreasing of the proton strength in the zeolite channels. The obtained materials were characterized with SEM and photoluminescence spectroscopy. We believe that this hybrid material will be an appealing candidate for the applications of optical fiber, telecommunications and bio‐imaging.     

钇对掺饵多孔硅体系1.54μm发光的增强作用

首次报道了用恒电位电解法将饵、钇共掺入多孔硅（porous silicons, PS） 中，经高温退火处理后，观察到了在近红外区（1.54 μm）室温下较强的光致发光 （photoluminescence, PL），并与掺饵多孔硅（erbium-doped porous silicon, PS:Er）做了比较，发现钇的共掺入对掺饵多孔硅体系1.54 μm发射起了增强作用 。研究了饵、钇共掺杂多孔硅（erbium and yttrium co-doped porous silicon, PS:Er, Y）光致发光强度随温度的变化，发现PS:Er与Si:Er材料相似，有较强的 温度猝灭效应，而PS:Er，Y体系的PL强度随温度升高趋于平稳，且有增强的趋势， 受温度影响不明显，并初步探讨了其发光机制。     

Photoinduced Luminescence Blinking and Bleaching in Individual Single‐Walled Carbon Nanotubes

The temporal evolution of photoluminescence in individual single‐walled carbon nanotubes (SWNT) under strong laser irradiation is studied and pronounced blinking and bleaching is observed, caused by photoinduced oxidation that subsequently quenches mobile excitons. The nanotubes are isolated with sodium cholate and spun onto either a glass or mica surface. Their bleaching behavior is investigated for variable laser intensities in air and argon atmosphere. The decay rate for luminescence bleaching generally increases with higher laser intensity, however saturating on mica substrates, which is attributed to limited availability of oxygen in the vicinity of the nanotubes. Step‐like events in the luminescence time traces corresponding to single oxidation events are analyzed regarding relative step height and suggest an exciton diffusion range of about 105 nm.     

Ce,Pr掺杂的YAG微晶玻璃的制备及光谱性能

以Y2O3-Al2O3-SiO2-Li2O-K2O-Na2O玻璃作为Ce,Pr掺杂基质玻璃,制备出白光LED用Ce:YAG和Ce,Pr:YAG微晶玻璃.使用X射线衍射仪、场发射扫描电子显微镜、荧光光度计对微晶玻璃的晶相、微观形貌、光谱性能及荧光寿命进行了研究.结果表明:掺杂铈或铈镨共掺杂的基质玻璃在1400℃热处理得到...     

Electronic,Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal–Organic Frameworks

Tetrathiafulvalene-lanthanide (TTF-Ln) metal–organic frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as electrical conductivity, redox activity, luminescence and magnetism. Herein a new family of isostructural TTF-Ln MOFs is reported, denoted as MUV-5(Ln) (Ln=Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermolecular S⋅⋅⋅S contacts established along the chain direction between partially oxidised TTF moieties. In addition, this family shows photoluminescence properties and single-molecule magnetic behaviour, finding near-infrared (NIR) photoluminescence in the Yb/Er derivative and slow relaxation of the magnetisation in the Dy and Er derivatives. As such properties are dependent on the electronic structure of the lanthanide ion, the immense structural, electronic and functional versatility of this class of materials is emphasised.     

增强掺Tb凝胶玻璃荧光性能的有机螯合体的选择

采用原位合成技术, 用溶胶凝胶法制备了稀土离子(Tb^3＋), β-二酮及协同体共掺的二氧化硅玻璃, 测量了它们发射光谱和红外光谱, 并进行了XRD, SEM和TG-DSC测试. 探讨各不同成分原位合成稀土有机配合物在二氧化硅玻璃中的发光性能及热处理温度对发光性能的影响. 结果表明, 在凝胶玻璃中掺入能级较匹配的β-二酮, 可以使稀土离子的荧光增强; 合适的协同体的引用也能使稀土离子的荧光增强. 这些结果为今后制备荧光较强的含Tb离子的SiO₂凝胶玻璃提供了一定的依据.     

Preparation and characterization of the biomineralized zinc oxide particles in spider silk peptides

In this work, hierarchical ZnO particles were prepared using a biomineralization strategy at room temperature in the presence of peptides acidified from spider silk proteins. A mechanism of the mineralization of the ZnO particles was that the affinity of original ZnO nanoparticles and zinc ions in the peptide chains played an important role in controlling the biocrystallizing formation of the pore ZnO particles. The intensity of their visible green luminescence was enhanced with increases of the mineralization time due to the porous surface defects. The hierarchical ZnO materials with biomolecules will facilitate their photoluminescence spectra applications as biosensors or optoelectronic nanodevices in the future, when covalently coupled with peptides or other biomolecules to achieve patterned growth over large areas of substrate.     

Photo- and thermally stimulated luminescence of polyminerals extracted from herbs and spices

Ionizing radiation processing is a widely employed method for preservative treatment of foodstuffs. Usually it is possible to detect irradiated herbs and spices by resorting to luminescence techniques, in particular photo- and thermostimulated luminescence. For these techniques to be useful, it is necessary to characterize the response to radiation of each particular herb or spice. In this work, the thermoluminescence (TL) and photostimulated luminescence (PSL) properties of inorganic polymineral fractions extracted from commercial herbs and spices previously irradiated for disinfestation purposes have been analyzed. Samples of mint, cinnamon, chamomile, paprika, black pepper, coriander and Jamaica flower were irradiated from 50 to 400 Gy by using a beta source. The X-ray diffraction (XRD) analysis has shown that the mineral fractions consist mainly of quartz and feldspars. The PSL and TL response as a function of the absorbed dose, and their fading at room temperature have been determined. The TL glow curves have been deconvolved in order to obtain characteristic kinetics parameters in each case. The results of this work show that PSL and TL are reliable techniques for detection and analysis of irradiated foodstuffs.     

Inhomogeneous broadening, luminescence origin and optical amplification in bismuth-doped glass

Absorption and luminescence spectra and optical amplification in bismuth-doped germanate silicate glass were investigated. Two kinds of bismuth ion valence states could exist in the glass. One is Bi2+, which has shown red luminescence, another might be Bi+, which is the active center for infrared luminescence. The infrared luminescence excited at 700, 800, and 980 nm should be ascribed to the electronic transition 3P1 --> 3P0 of Bi+ ions in three distinct sites. The shifting, broadening, and multiple configuration of the luminescence could be due to the randomly disorder of local environment and multiple sites of the active centers. In this glass, obvious optical amplification was realized at 1300 nm wavelength when excited at 808 and 980 nm, respectively.     

Mechanochromic luminescence of soft crystals: Recent systematic studies in controlling the molecular packing and mechanoresponsive properties

Soft crystals are a class of smart materials that can switch their photophysical or mechanical properties in response to gentle external stimuli. A representative stimuli-responsive behavior of soft crystals is mechanochromic luminescence (MCL), i.e., a reversible color change of solid-state photoluminescence induced by external mechanical stimuli. Together with the rapid growth in the area of solid-state photoluminescence including fluorescence, room-temperature phosphorescence (RTP), thermally activated delayed fluorescence (TADF), white-light emission (WLE), and circularly polarized luminescence (CPL), a number of soft crystals that exhibit MCL behaviors have been reported during the past decade. In the typical MCL of soft crystals, the emission color switches in the bathochromic direction upon amorphization by grinding and recovers to the original color upon recrystallization by heating or exposure to organic solvents. Relatively few are known to exhibit hypsochromically shifted MCL, two-step MCL, self-recovering MCL, or mechanical-stimuli-induced single-crystal-to-single-crystal (SCSC) transitions. Rational design guidelines to control the mechanoresponsive properties of soft crystals have not yet been established. This review summarizes the systematic studies on the substituent effect to control the MCL properties of soft crystals. Recent studies provide useful insights into the effects of electronic and steric differences of substituents on crystal structure, luminescence properties, and mechanoresponsive behaviors.     

The effect of the surface of SnO2 nanoribbons on their luminescence using x-ray absorption and luminescence spectroscopy

X-ray excited optical luminescence (XEOL) and x-ray absorption near-edge structure in total electron, x-ray fluorescence, and photoluminescence yields at Sn M5,4-, O K-, and Sn K-edges have been used to study the luminescence from SnO2 nanoribbons. The effect of the surface on the luminescence from SnO2 nanoribbons was studied by preferential excitation of the ions in the near-surface region and at the normal lattice positions, respectively. No noticeable change of luminescence from SnO2 nanoribbons was observed if the Sn ions in the near-surface region were excited selectively, while the luminescence intensity changes markedly when Sn or O ions at the normal lattice positions were excited across the corresponding edges. Based on the experimental results, we show that the luminescence from SnO2 nanoribbons is dominated by energy transfer from the excitation of the whole SnO2 lattice to the surface states. Surface site specificity is not observable due to its low concentration and weak absorption coefficient although the surface plays an important role in the emission as a luminescence center. The energy transfer and site specificity of the XEOL or the lack of the site specificity from a single-phase sample is discussed.