Optical and gas sensing properties of mesoporous hollow ZnO microspheres fabricated via a solvothermal method

Mesoporous,hollow Zn O microspheres were synthesized via a hydrothermal method,using glycerol and zinc acetate as the starting materials.XRD and FESEM analysis showed that the surface morphology of the spheres with a Wurtzite structure could be reasonably adjusted by varying the weight ratio(Rw) of Zn(CH3COO)2 2H2O:H2O:C3H8O3.The responses of the gas sensor based on the spheres to 100 ppm ethanol and 100 ppm acetone are 18.9 and 10.4,respectively.The response and recovery times of the sensor to ethanol and acetone are 2 s and 3 s,3 s and 5 s,respectively.The hollow spheres show an intense UV emission at 392 nm and a broad blue-green emission at 488 nm.Interestingly,a light trapping phenomenon is revealed by UV emission and scattering measurements on the microspheres,which can be attributed to the mesoporous shell and hollow structure of the microsphere.     

Preparation of Porous Polylactide Microspheres and Their Application in Tissue Engineering

In this study,porous polylactide (PLA) microspheres with different structures were prepared through the multiple emulsion solvent evaporation method.By changing organic solvents (ethyl acetate and chloroform) and adding effervescent salt NH4HCO3 in the inner water phase,microspheres with porous capsular,matrix,microcapsular and multivesicular structures were prepared.The protein encapsulation and release,and the cell growth behavior of porous microspheres were further explored.Under the same inner water phase,microspheres prepared with chloroform had higher protein encapsulation efficiency and less protein release rate as compared with those prepared with ethyl acetate.Cell experiments showed that the relatively rough surface of microspheres prepared with chloroform was more favorable for the cell growth in comparison with the smooth surface of microspheres prepared with ethyl acetate.This study shows a simple and effective method to control the protein release and cell growth behaviors of polymer microspheres by tuning their porous structure.     

Regional variation of sediment load of Asian rivers flowing into the ocean

CdS, CdS:Mn, ZnS, ZnS:Mn and ZnS:Tb nanoparticles were prepared by using carboxylic-containing copolymer, polystyrene-maleic anhydride (PSM), as template. Average particle size, 2.5 nm for CdS nanoparticles, is deduced from UV-vis absorption spectra and consistent with the observation of TEM. Characteristic emissions of the doping ions can be observed and the energy transfer from the host to the doping ions is verified. Fourier transform infrared (FTIR) spectra were studied to confirm the bonding effect of the copolymer and the metal ions. PSM hydrolyzed and chelated metal ions by its carboxylic group, and then performed as a protection layer after the formation of nanoparticles.     

Synthesis of bovine serum albumin imprinted Mn:ZnS quantum dots

A novel bovine serum albumin（BSA） imprinted Mn-doped ZnS quantum dots（Mn:ZnS QDs） is firstly reported.The molecular imprinted polymer（MIP） functionalized Mn:ZnS QDs（Mn:ZnS@SiO₂@MIP） include the preparation of Mn:ZnS QDs,the coating of silica on the surface of Mn:ZnS QDs,and the functional polymerization by sol-gel reaction using 3-aminophenylboronic acid as the functional and cross-linking monomer in the presence of BSA（Mn:ZnS@SiO₂@MIP-BSA）,and then the elution of the imprinted BSA on the surface of Mn:ZnS@SiO₂ QDs.The results showed that the phosphorescence of Mn:ZnS@SiO₂@MIP is stronger quenched by BSA than that of non-imprinted one（Mn:ZnS@SiO₂@NIP）,indicating that the selectivity of the imprinted Mn:ZnS quantum dots toward BSA is superior to that of non-imprinted one.     

STUDY OF DEPENDENCE OF LIQUID CHROMATOGRAPHIC PERFORMANCE UPON PORE STRUCTURE OF POROUS POLYDIVINYLBENZENE MICROSPHERES

Pore structure of the porous polydivinylbenzene microspheres is controlled by the degreeof crosslinkage and the diluent used. It is proved by chromatographic results that the higher thedegree of crosslinkage is, the more the micellar pores will be formed, and the nature as wellas the quantity of the diluent determine the real pore structure. Among the structural para-meters of the microspheres, the size and the pore diameter affect the performance in HPLCmostly. The linear sample capacity of the microspheres in 1--2 order of magnitude larger thanthat of the Silica-ODS. According to this result, it could be confirmed that the solute mole-cules penetrate deeply into the skeleton of the polymer network. Based on the polymeric struc-ture with the same chemical composition but different in pore structure, the contribution tothe retention of several organic compounds by Henry's and/or adsorption coefficient has beenstudied. The results obtained show that Henry's coefficient is approximately 80% of thetotal contribution, i. e. dissolution mechanism plays the main role in the chromatographicprocess, especially in case of polar compounds. The experimental result that the chroma-tographic separation relatively slightly depends upon the sueface area of the polymer isanother ovidence. It is better to define this kind of polymeric stationary phase as a sorbentrather than an adsorbent. From the point of view of dissolution mechanism, it is suggestedthat a homogeneous porous polymeric stationary phase constructed with chemically rigid ske-letal structure and sufficiently thin bulk polymeric phase inside the microspheres should bean ideal packing for chromatography.     

Fluorescence Quantum Efficiency Enhancement in CaWO4:Eu3+,Na+ Nanocrystals by Tridoping with F- Ions

We demonstrated that tridoping with F- ions is an effective way to improve the fluorescence quantum efficiency of CaWO4:Eu3+,Na+ nanocrystals. F--tridoped samples with different F- concentrations were synthesized by a hydrothermal process. The fluorescence spectra and decay curves were measured at room temperature. The fluorescence intensity of F--tridoped samples is about 3 times that for the non F--doped sample. The fluorescence quantum efficiency can be enhanced by 21% when the atomic ratio of F to W was 0.7.     

Silver Hollow Microspheres: Large-scale Synthesis, Characterization and Electromagnetic Shielding Property

A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core-shell particles by a controllable liquid reduced reaction of Ag[(NH3)2]+ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy (SEM), transmitted electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.     

Preparation of PLGA microspheres with different porous morphologies

Poly(D,L-lactide-co-glycolide)(PLGA) microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell(denoted by hollow in brief) and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin(BSA) was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior.     

Preparation and Characterization of Biodegradable Polylactide（PLA） Microspheres Encapsulating Ginsenoside Rg3

In this study, the process of a biodegradable polylactide（PLA） microsphere encapsulating ginsenoside Rg3 was first studied by the emulsion solvent evaporation method, for enhancing solubility and stability of ginsenoside Rg3. Alabum was also first used as a modifier in this method. The mean diameter of the prepared PLA microspheres containing Rg3 was 40 μm. Ginsenoside Rg3 released from the microspheres was studied by HPLC and detected by UV. It was found that the drug release curve fitted the Model Heller-Baker best.     

Synthesis and Characterization of Copolymercore-Silvershell Composite Microspheres

Composite microspheres composed of monodispersed poly（St-co-MAA） latices with diameter about 260 nm as core and Ag nanocrystals as shell were prepared by an in situ reduction method. The shell thickness could be controlled in the range of 15--45 nm by this coating process. The structure and the composition of the core-shell microspheres were characterized by transmission electron microscopy （TEM）, X-ray diffractometry （XRD）, X-ray photoelectron spectroscopy （XPS）, and thermogravimetric analysis （TG）. The formation of the composite microspheres is explained by the nucleation of silver on the surface of the latices followed by growth of the silver shell.     

Synthesis and characterization of the water-soluble silica-coated ZnS:Mn nanoparticles as fluorescent sensor for Cu ions

Silica-coated ZnS:Mn nanoparticles were synthesized by coating hydrophobic ZnS:Mn nanoparticles with silica shell through microemulsion. The core–shell structural nanoparticles were confirmed by X-ray diffraction (XRD) patterns, high-resolution transmission electron microscope (HRTEM) images and energy dispersive spectroscopy (EDS) measurements. Results show that each core–shell nanoparticle contains single ZnS:Mn nanoparticle within monodisperse silica nanospheres (40 nm). Photoluminescence (PL) spectroscopy and UV–vis spectrum were used to investigate the optical properties of the nanoparticles. Compared to uncoated ZnS:Mn nanoparticles, the silica-coated ZnS:Mn nanoparticles have the improved PL intensity as well as good photostability. The obtained silica-coated ZnS:Mn nanoparticles are water-soluble and have fluorescence sensitivity to Cu²⁺ ions. Quenching of fluorescence intensity of the silica-coated nanoparticles allows the detection of Cu²⁺ concentrations as low as 7.3 × 10⁻⁹ mol L⁻¹, thus affording a very sensitive detection system for this chemical species. The possible quenching mechanism is discussed.     

Synthesis of Multifunctional Mn‐Doped CdTe/ZnS Core/Shell Quantum Dots

The synthesis of a novel water‐soluble Mn‐doped CdTe/ZnS core‐shell quantum dots using a proposed ultrasonic assistant method and 3‐mercaptopropionic acid (MPA) as stabilizer is descried. To obtain a high luminescent intensity, post‐preparative treatments, including the pH value, reaction temperature, reflux time and atmosphere, have been investigated. For an excellent fluorescence of Mn‐doped CdTe/ZnS, the optimal conditions were pH 11, reflux temperature 100°C and reflux time 3 h under N₂ atmosphere. While for phosphorescent Mn‐doped CdTe/ZnS QDs, the synthesis at pH 11, reflux temperature 100°C and reflux time 3 h under air atmosphere gave the best strong phosphorescence. The characterizations of Mn‐doped CdTe/ZnS QDs were also identified using AFM, IR, powder XRD and thermogravimetric analysis. The data indicated that the photochemical stability and the photoluminescence of CdTe QDs are greatly enhanced by the outer inorganic ZnS shell, and the doping Mn²⁺ ions in the as‐prepared quantum dots contribute to strong luminescence. The strong luminescence of Mn‐doped CdTe/ZnS QDs reflected that Mn ions act as recombination centers for the excited electron‐hole pairs, attributing to the transition from the triplet state (⁴T₁) to the ground state (⁶A₁) of the Mn²⁺ ions. All the experiments demonstrated that the surface states played important roles in the optical properties of Mn‐doped CdTe/ZnS core‐shell quantum dots.     

Poly(MAA-Mn) for Triple-Layer Structure Synthesis of ZnS/ZnS:Mn/SiO2 Phosphors

Methacrylic acid (MAA) was used as a manganese carrier to prepare ZnS/MAA-Mn particles, and ZnS/ZnS:Mn phosphors were formed from ZnS/MAA-Mn by ion substitution through heat treatment. After silica coating on surface by chemical precipitation method with tetraethyl orthosilicate (TEOS), ZnS/ZnS:Mn/SiO₂ phosphors were prepared successfully as a new core/shell structure compound. The thickness of layers was controlled by adjusting concentrations of manganese (II) acetate (Mn(CH₃COO)₂) and TEOS. Structure, morphology, and composition of prepared phosphors were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Photoluminescence (PL) properties of ZnS with different Mn²⁺ content were analyzed by PL spectrometer. PL emission intensity and PL stability were analyzed for evaluating effects of silica coating and Mn²⁺ activator doping. As a result, the structure of two layers could be observed, and optimum composition of ZnS/ZnS:Mn/SiO₂ structure was also obtained.     

基于L-半胱氨酸修饰的锰掺杂ZnS量子点应用于叶酸测定

以L-半胱氨酸为表面修饰剂制备了稳定性和水溶性均优的ZnS∶Mn2+纳米晶,并应用于叶酸的检测。在pH 7.4的KH2PO4-Na2HPO4 缓冲溶液中,叶酸的加入使ZnS∶Mn2+体系的荧光发生猝灭,荧光强度的变化与叶酸浓度呈良好的线性关系,其线性范围为1.0×10-6~7.0×10-5 mol?L-1 （4.4×10-4~3.1×10-2 g?L-1）,方法检出限为9.6×10-7 mol?L-1 （4.2×10-4 g?L-1）。该方法用于叶酸片剂和健康人尿液中叶酸的测定,结果满意。采用荧光光谱、紫外可见吸收光谱及X-ray光谱等研究了ZnS∶Mn2+纳米晶及其水溶液的特性,通过热力学参数对叶酸测定的可能机理进行了探讨。     

Synthesis and characterization of high-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) luminescent nanocrystals

High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.     

New observations on the luminescence decay lifetime of Mn2+ in Zns: Mn2+ nanoparticles

A fast decay emission peaking at 645 nm with a decay lifetime within the experimental resolution of 0.14 micros is observed in ZnS:Mn2+ nanoparticles. This short-lived signal is also observed in pure ZnS and MgS: Eu3+ nanoparticles, which has nothing to do with Mn(2+)-doped ions but is from the deep trap states of the host materials. The short-lived component decreases in intensity relative to the Mn2+ emission at higher excitation powers, while it increases in intensity at low temperatures and shifts to longer wavelengths at longer time delays. Our observations demonstrated further that the emission of Mn2+ in ZnS: Mn2+ nanoparticles behaves basically the same as in bulk ZnS: Mn2+; the fast decay component is actually from the intrinsic and defect-related emission in sulfide compounds.     

Magic sized ZnS quantum dots as a highly sensitive and selective fluorescence sensor probe for Ag+ ions

A green and simple chemical synthesis of magic sized water soluble blue-emitting ZnS quantum dots (QDs) has been accomplished by reacting anhydrous Zn acetate, sodium sulfide and thiolactic acid (TLA) at room temperature in aqueous solution. Refluxing of this mixture in open air yielded ZnS clusters of about 3.5 nm in diameter showing very strong and narrow photoluminescence properties with long stability. Refluxing did not cause any noticeable size increment of the clusters. As a result, the QDs obtained after different refluxing conditions showed similar absorption and photoluminescence (PL) features. Use of TLA as a capping agent effectively yielded such stable and magic sized QDs. The as-synthesized and 0.5 h refluxed ZnS QDs were used as a fluorescence sensor for Ag(+) ions. It has been observed that after addition of Ag(+) ions of concentration 0.5-1 μM the strong fluorescence of ZnS QDs was almost quenched. The quenched fluorescence can be recovered by adding ethylenediamine to form a complex with Ag(+) ions. The other metal ions (K(+), Ca(2+), Au(3+), Cu(2+), Fe(3+), Mn(2+), Mg(2+), Co(2+)) showed little or no effect on the fluorescence of ZnS QDs when tested individually or as a mixture. In the presence of all these ions, Ag(+) responded well and therefore ZnS QDs reported in this work can be used as a Ag(+) ion fluorescence sensor.     

Generation and optical properties of monodisperse wurtzite-type ZnS microspheres

Monodisperse wurtzite-type ZnS microspheres have been prepared by using glutathione (GSH) as a sulfur source at low reaction temperatures ranging from 160 to 210 degrees C. The diameter of the ZnS microspheres can be tuned from approximately 254 to approximately 597 nm by changing the reaction parameters such as temperature, molar ratio of reactants (GSH/Zn2+), and reaction medium (ethylenediamine or ammonia). Our results demonstrate that monodentate amines (ammonia) play the same role as that of bidentate amines (ethylenediamine) in the formation of the wurtzite-type ZnS microspheres. The formation process of the monodisperse ZnS microspheres consists of a GSH-dominated nucleation process and an amine-dominated assembly process. The as-synthesized monodisperse ZnS microspheres readily self-assemble into ordered hexagonal patterns and thus have potential applications as colloidal crystalline materials. Blue fluorescence emission peaks at 415 and 466 nm in wavelength, attributed to deep-trap emission, are observed at room temperature.     

ZnS:Mn/ZnS量子点在DNA定量分析中的应用

以巯基乙酸为稳定剂,采用成核掺杂的方法在水溶液中一步制备得到具有核壳结构的ZnS:Mn/ZnS量子点.研究了荧光、室温磷光产生的机理.基于DNA对量子点发光的增强效应,以ZnS:Mn/ZnS量子点作为标记探针建立了测定DNA的荧光、室温磷光的分析方法.考察了量子点浓度、EDC/NHS用量和反应时间等条件对DNA测定的影...     

水热法合成单分散ZnS微球

以醋酸锌、硫代乙酰胺为原料, P123表面活性剂为模板, 采用水热法, 成功合成ZnS微球, 并提出其可能的形成机理. 通过XRD, TEM, FT-IR, N₂吸附-脱附表征, 发现该微球由ZnS纳米颗粒组成, ZnS纳米颗粒尺寸为6～7 nm; 微球直径500～600 nm, 具有单分散性, 表面光滑, 大小均匀; 在4000～400 cm^－1波段具有热红外透过性等特点, 有望在光、电、磁等领域发挥其潜在的应用价值.