Plasmon assisted intense blue-green emission from ZnO/ZnS nanocrystallites

Excellent luminescence properties of ZnO/ZnS nanocrystallites prepared using simple wet chemical approach at room temperature have been reported. ZnS coating on the surface of ZnO nanocrystallites enhanced the green emission (around 500 nm) by a factor of 2. The intensity of the blue emission around 450 nm of ZnO/ZnS nanocrystallites is observed to be as high as three times the emission intensity of pure ZnO nanocrystallites. A further overall increase by a factor of ∼2.5 has also been observed in the intensity of wide blue-green emission when the sample was prepared onto grating compared to that of the samples prepared onto uncoated as well as gold coated quartz. The enhanced emission is thought to be due to plasmon assisted electromagnetic field enhancement near nanocrystallites-metal interface. This is supported by power dependent photoluminescence measurements. The strong enhanced blue-green emission covering a wide spectral range of ∼375-650 nm signifies potential optoelectronic applications in near UV and VIS wavelength regimes.     

A highly luminescent ZnS/CdSe/ZnS nanocrystals-tetrapeptide biolabeling agent

Stable colloidal ZnS/CdSe/ZnS nanocrystals capped with hexadecylamine were transferred into water by encapsulation in a protective shell of an amphiphilic polymer. The properties of the products have been investigated by dynamic lighting scattering, absorption, and photoluminescence spectroscopy. These nanocrystals, when conjugated with tuftsin in aqueous suspension, formed an effective labeling reagent for macrophages or lymphocytes. The labeling of cells was demonstrated by confocal microscopy. Hybrid bio-inorganic nanoconjugates are potentially powerful fluorescent tracking tools in biological systems.     

Deposition and STM characterization of luminescent organic molecules on metal substrates

The porphyrin-based molecules including H₂TBPP, ZnTBPP and P_tTBPP as well as the perinone derivatives (PD) molecules were deposited on Au(100), Au(111) and Cu(100) substrates in the form of single molecule, molecular line, submonolayer, monolayer and multilayer. The features of the performed molecular nanostructures were characterized by an ultrahigh vacuum scanning tunneling microscopy (STM) at room temperature. The observed molecular topographies matched very well with the molecule structures in spite of the fact that the molecular adsorption states were influenced by different metal surface. STM-induced photon emission was generated from the surface of H₂TBPP multilayer structures on Au(100) in tunneling junction when the applied bias exceeds the “turn-on” voltages ∼− 1.6 V or + 1.3 V at 0.5 nA.     

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot.     

Highly water-resistant and organic miscible inorganic/polymer composite luminescent material

A novel highly water-resistant and organic miscible luminescent phosphor has been synthesized by grafting a polymer onto the surface of SrAl₂O₄:Eu²⁺, Dy³⁺ (SAO–ED). A bifunctional ligand, 3-allyl-2, 4-pentanedione (APD) was used as a bridge to introduce the polymer onto the surface of SAO–ED. The coordination of APD with SAO–ED was confirmed by FT–IR spectra. The luminescence property of SAO–ED/polymer composite material was analyzed by spectrometer LS-100. The water resistance and miscibility with organics of the product were also investigated. Compared with traditional inorganic SAO–ED, this novel polymer-grafted SAO–ED has higher brightness, much better water resistance and good miscibility with organic solvents and polymers.     

MCM-41与8-羟基喹啉铝复合发光材料的制备与性能研究

以十六烷基三甲基溴化铵（CTAB）为模板剂，正硅酸乙酯（TEOS）为硅源，在有机弱碱和室温条件下制备出高度有序的介孔材料MCM-41。以氯仿、乙醇为混合溶剂，将有机发光小分子8-羟基喹啉铝（Alq3）组装进介孔MCM-41中，得到有机-无机复合发光材料。采用XRD、IR、紫外-可见漫反射、N2吸附-脱附、激发发射等测试方法对产物的结构和性能进行了分析，结果表明，组装体保持了有序的介孔结构，并且主客体之间存在较强的相互作用。     

Electrophoretic deposition of functional organic molecules and composite films

2,2′-Bicinchoninic acid (BiqCOOH) exhibits a set of functional properties, which motivated the work of fabricating BiqCOOH films. Thin films of BiqCOOH were prepared potentiodynamically or under constant-voltage conditions from the solutions of dipotassium salt of 2,2′-bicinchoninic acid (BiqCOOK) in water or ethanol-water solvent. Electron microscopy investigations showed that the electrochemical assembly of BiqCOOH in aqueous solutions resulted in fibrous morphology while a flower-like morphology, containing rectangular prism-shaped particles, was the result in ethanol-water solutions. The anodic deposition mechanism for BiqCOOH has been proposed based on the analysis of cyclic voltammetry (CV), electron microscopy and FTIR data. The polyaromatic BiqCOOK molecules, containing chelating ligands, showed adsorption on a range of different materials, such as Pd, NiO and multi-walled carbon nanotubes (MWCNT). An electrophoretic deposition (EPD) method allowed for the manufacturing of Pd, NiO and MWCNT films using BiqCOOK as anionic dispersing and binding species. The results of this investigation have generated new possibilities in creating individual material and composite films for applications based on their functional properties.     

A novel paramagnetic polymeric sensor material sensitive to organic molecules

Utilizing the Diels-Alder reaction between cyclopentadiene groups attached on the linear polystyrene in the presence of nitroxide free radicals, a novel cross-linked network containing nitroxide free radicals is prepared. The signals of the electron spin resonance (ESR) from the resultant paramagnetic polymeric material contacting with organic molecules are different from uncontacting with organic molecules obviously. And the response from the organic molecules to organic molecules free or vice versa was reversible. Therefore, the resultant material is a novel paramagnetic polymeric sensor material sensitive to organic molecules and can be used for detecting the presence of organic molecules or the absence of organic molecules.     

原位反应制备ZnS/还原氧化石墨烯复合材料及其光催化性能

以氧化石墨烯和ZnAc2为反应前驱物,采用二甲基亚砜(DMSO)作为硫源和反应溶剂,通过一步溶剂热法原位制备出负载ZnS的还原氧化石墨烯(RGO)复合材料(ZnS/RGO)。采用SEM、XRD、激光拉曼(Raman)和荧光光谱对样品的微观形貌和化学结构进行表征。结果显示:原位反应制备的ZnS/RGO复合材料是由呈圆球状并均匀负载的纳米ZnS和6~7层RGO层状结构组成;在模拟紫外光照射下,对甲基橙污染物的光催化结果表明,ZnS/RGO复合材料的降解效率明显高于纯ZnS;同时,在多次循环催化过程中,ZnS/RGO复合材料的光催化效率仍基本保持不变,表明原位反应使ZnS与RGO结合增强。荧光光谱结果表明,ZnS/RGO复合材料光催化效率增强的主要原因在于ZnS中光生电子通过RGO得到有效的分离,进而延长了电子-空穴的复合效率。     

Visible light-active iron-doped anatase nanocrystallites and their self-cleaning property

To extend and improve photocatalytic activity of TiO₂ in UV-visible region and reduce electron-hole recombination, Fe³⁺ doped anatase nanocrystallites were synthesized by a sol-gel process in an aqueous solution at a temperature of 60 °C with the addition of Fe³⁺ dopant. The Fe³⁺ dopant with various doping level was investigated. Superior self-cleaning performance was achieved for the optimal doped anatase nanocrystals when compared to that of the pure TiO₂ through the evaluation of colorant decomposition, the degradation of a coffee stain, and a red wine stain under UV and visible light irradiation. The study demonstrated that it is feasible to apply Fe³⁺ doped anatase nanocrystallites to materials with low thermal resistance, such as textiles and other biomaterials as the doped anatase nanocrystals were formed during the sol-gel process without the need of any post-thermal treatment and the use of aqueous based sol-gel process instead of previously reported solvent-based ones is more environmentally friendly and suitable for large-scale fabrication.     

Structure property relationship among novel dental composite matrix resins

Several novel dimethacrylate monomers of propoxylated diphenols have been synthesized to establish a correlation between their structure and the important properties of viscosity, curing shrinkage and wetting behaviour. These dimethacrylates were designed to possess linear and flexed structures. These new monomers exhibited very much lower viscosities compared to the conventionally used Bis-GMA. Good correlations were obtained for variations of the monomer structures with bulk viscosities and curing shrinkages. However, the wetting behaviour of these resins did not show any trend.     

Quantum-size effects of PbS nanocrystallites in evaporated composite films

Semiconductor nanocrystallites exhibit electronic, optical and photochemical properties greatly differing from those observed in the related bulk material due to quantum size effects. In view of future applications, nanoclusters based on sulphur compounds will find great potential as photocatalysts or nonlinear optical materials. The method of interrupted island growth was applied to form PbS nanocrystallites in a dielectric SiO₂ host by a two source-evaporation technology. Depending on the deposition conditions, PbS nanocrystals can be formed with grain size down to about 1 nm, giving a significant increase in the optical band gap from 0.41 eV for the bulk material to about 5.2 eV. XPS, XRD and TEM investigations were performed to verify the formation of PbS nanocrystallites in the SiO₂ host. These nanocrystallites show an intensive photoluminescence emission band at about 435 nm, with the intensity decreasing with increasing PbS concentration.     

Low temperature synthesis and optical property of ZnS nanotubes

Zinc sulphide (ZnS) nanotubes were synthesised via simple surfactant emulsion template under hydrothermal conditions. X-ray diffraction, scanning electron microscopy and transmission electron microscope were used to characterise the nanotubes. The results indicate that the nanotubes are composed of nanoparticles. The diameters of the nanotubes vary from 300 to 700?nm and lengths range from 1 to 2?µm. In addition, it is found that the reaction time, reaction temperature and cetyltrimethylammonium bromide play key roles in the phase and morphology control of ZnS nanotubes. Furthermore, room temperature photoluminescence was recorded to investigate the optical property of the obtained product. The stable and strong green emission band centred at 513?nm was attributed to some self-activated centres, probably vacancy states or interstitial states related to the peculiar structure.     

Rapid and efficient detection of single chromophore molecules in aqueous solution

The first experiments on the detection of single fluorescent molecules in a flowing stream of an aqueous solution with high total efficiency are reported. A capillary injection system for sample delivery causes all the dye molecules to pass in a diffusion-broadened stream within a fast-moving sheath flow, through the center of the tightly focused laser excitation beam. Single-molecule detection with a transit time of ~1 ms is accomplished with a high-quantum-efficiency single-photon avalanche diode and a low dead-time time-gating circuit for discrimination of Raman-scattered light from the solvent.     

Synthesis and characterization of sol-gel derived ZnS : Mn2+ nanocrystallites embedded in a silica matrix

Synthesis and characterization of undoped and Mn²⁺ doped ZnS nanocrystallites (radius 2–3 nm) embedded in a partially densified silica gel matrix are presented. Optical transmittance, photoluminescence (PL), ellipsometric and electron spin resonance measurements revealed manifestation of quantum size effect. PL spectra recorded at room temperature revealed broad blue emission signal centred at ∼ 420 nm and Mn²⁺ related yellow-orange band centred at ∼ 590 nm while ESR indicated that Mn in ZnS was present as dispersed impurity rather than Mn cluster.     

一种新型的水性丙烯酸长余辉发光涂料

以Eu^2 和Dy^3 共掺杂的铝酸锶发光材料为发光体,以水性丙烯酸乳液为成膜介质制备了一种新型的发光涂料。该发光涂料环境友好,而且比相应的发光材料具有更长的余辉发光时间和更高的发光强度。     

碳纳米管/ZnS复合材料的制备及其性能表征

碳纳米管用氨水、乙二胺四乙酸(EDTA)进行表面改性, 然后通过硫代乙酰胺、醋酸锌、水和表面改性的碳纳米管在水浴超声条件下发生溶液化学反应, 在碳纳米管表面包裹了一层分布均匀、致密的ZnS纳米晶粒. 用XRD、TEM、SAED、SEM、FTIR、PL等表征手段对材料进行了结构及性能表征. 研究结果表明: 对碳纳米管进行乙二胺四乙酸处理是实现ZnS纳米晶粒在碳纳米管表面均匀、致密包裹的重要因素, 碳纳米管/ZnS复合材料的光致发光性较之相同方法合成的ZnS, 俘获态发射峰蓝移6nm, 而能带边缘发射峰蓝移16nm. 通过对FTIR及不同表面改性碳纳米管的对比试验研究, 给出了碳纳米管/ZnS复合材料的形成机理.