Direct Conversion of Bulk Metals to Size‐Tailored,Monodisperse Spherical Non‐Coinage‐Metal Nanocrystals

Monodisperse non‐noble metal nanocrystals (NCs) that are highly uniform in shapes and particle size are much desired in various advanced applications, and are commonly prepared by either thermal decomposition or reduction, where reactive organometallic precursors or/and strong reducing agents are mandatory; however, these are usually toxic, costly, or suffer a lack of availability. Bulk Group 12 metals can now be converted into ligand‐protected, highly crystalline, monodisperse spherical metal NCs with precisely controlled sizes without using any precursors and reducers. The method is based on low‐power NIR‐laser‐induced size‐selective layer‐by‐layer surface vaporization. The monodisperse Cd NCs show pronounced deep‐UV (DUV) localized surface plasmon resonance making them highly competitive DUV‐plasmonic materials. This approach will promote appreciably the emergence of a wide range of monodisperse technically important non‐coinage metal NCs with compelling functionalities.     

Heat-Induced Formation of Monodisperse Gold Nanoparticles in Different Conditions

We investigate the preparation of nearly monodisperse gold nanoparticles by heat treatment in different conditions. The effects of various solvents, heating temperature, and heating time length on the monodispersity of gold nanoparticles were studied systematically and a general route to generate gold nanoparticles with uniform size was determined. The first step was to prepare gold nanoparticles with less than 3 nm and the following operation was to heat the gold nanoparticles in the present of thiolated solvents where monodispersed gold nanoparticles could be obtained easily. Our approach has enriched synthesis of monodisperse gold nanoparticles, and may provide some valuable experimental data about how the heating process affects the size evolution of gold nanoparticles.     

A New Method for Separation of Hydrophobic Au Nanoparticles in the Reversal Micelle

In this article, a new method which not only can separate hydrophobic Au nanoparticles (NPs), but also obtain highly monodisperse NPs is discussed. A self‐made device of two same burettes, one of which was inserted into the other, was used for separating the nanoparticles by washing the reversal micelle. The effects of separation were characterized and analyzed by micrograph of transmission electron microscope (TEM), UV‐vis spectra, quartz crystal microbalance (QCM), and energy dispersive x‐ray analysis (EDX). It has been shown that, the smaller nanoparticles are, the easier they are to stay at the reversal micelle and the narrower the sizes are. This method can be applied to synthesize highly monodisperse Au NPs.     

Synthesis of highly monodisperse quantum dot‐loaded polymer beads by impregnation and precipitation techniques

A novel approach to the synthesis of highly monodisperse quantum dot‐loaded polymer beads by combining impregnation and precipitation techniques was reported. The monodisperse poly(glycidyl methacrylate) (PGMA) beads were first synthesized by dispersion polymerization. Then, the PGMA beads were chemically modified to generate carboxyl groups, and impregnation of cadmium ions (Cd²⁺) inside the beads. Subsequently, the cadmium ions were reacted with thioacetamide to form cadmium sulfide (CdS) quantum dots within the polymer beads. The morphology, structure, and properties of CdS quantum dot‐loaded polymer beads were studied by field emission scanning electron microscope (SEM), transmission electron microscope, fluorescence spectrophotometer, fluorescence microscope, Fourier transform infrared spectroscopy, powder X‐ray diffraction, and thermogravimetric analysis. The results indicated that the CdS quantum dot‐loaded polymer beads had an average size of 1.4 μm, and were highly monodisperse. More interestingly, the CdS quantum dots distributed evenly within the polymer beads, which provide very strong fluorescence intensity. The existence of carboxyl groups on the quantum dot‐loaded polymer beads was measured quantitatively, and was found to be 0.2 mmol/g. These CdS quantum dot‐loaded polymer beads involving functional carboxyl groups would have potential applications in biological immunoassay and photoelectronic fields. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and characterization of polymethacrylates containing conjugated oligo(phenylene ethynylene)s as side chains

In order to form suitable systems designed for resonance energy transfer, a series of monodisperse methacrylate‐based monomers containing rigid π‐conjugated oligo(phenylene ethynylenes) with different sizes of the conjugated systems ( M1 – M3 ), and therefore different optoelectronic properties, were synthesized and subsequently polymerized using the reversible addition–fragmentation chain transfer polymerization technique ( P1 – P3 ). In addition, these oligomers were also copolymerized with methyl methacrylate. The obtained polymers were characterized by ¹H NMR spectroscopy, size exclusion chromatography, and analytical ultracentrifugation. The photophysical properties of the polymers were studied by UV–vis absorption and emission spectroscopy in diluted solutions as well as in thin films and compared to the photophysics of the corresponding monomers. Thereby, changes going from monomeric to polymeric systems could be detected in fluorescence quantum yields and lifetimes pointing to energy trapping, e.g., energy transfer. Donor–acceptor copolymers containing different numbers of monomeric units within the side chain exhibit differences in the emission spectra, indicating that energy trapping in polymers is very sensitive to structural properties such as the chain length. UV–vis absorption spectroscopy as well as time‐resolved lifetime studies indicate intrapolymer and interpolymer energy transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

微波水热法制备CdS单分散纳米球及其形貌控制

采用微波水热法,以醋酸镉(Cd(CH3COO)2.2H2O)为镉源,硫脲(CS(NH2)2)为硫源,制备出了具有单分散球形形貌的CdS纳米晶。应用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、能量色散谱仪(EDS)、高分辨透射电子显微镜(HR-TEM)、紫外可见吸收光谱(UV-Vis)等测试手段对样品的物相、形貌、元素组分及吸光性能进行了表征,并以罗丹明B溶液的降解脱色反应来考察了其的光催化活性。结果表明:随着S/Cd物质的量比(nS/nCd)逐渐增大,产物会出现由刺球链状向分散球形过渡的规律性变化。在一定的nS/nCd比的条件下可以合成出大小均匀、分散性较好的六方相CdS纳米球。样品对可见光有较强吸收,存在着一定的红移现象。在可见光照射下,硫化镉单分散纳米球具有更高的光催化活性。     

双喷嘴乳粒发生器的研制及初步应用

 叙述了双喷嘴乳粒发生器的工作原理、设计关键点及设计思路,利用该发生器开展了双层乳粒的制备实验研究工作。研制的双喷嘴乳粒发生器在喷嘴处的3层管的位置能够通过简单调节达到同心,使得双层乳粒包覆的可靠性得到提高。研究了制备的乳粒的分散性和稳定性,并分析了形成双层乳粒的油相和水相的流速比,结果证明：利用所研制的双喷嘴乳粒发生器可以容易地制备出单分散性双层乳粒,油相与水相的流速比为0.3~15.0时,可形成双层乳粒。     

离子液体[Bmim]BF4中单分散Ru纳米粒子的制备及选择加氢性能

采用化学还原法在离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMim]BF₄)中制备了单分散纳米金属Ru粒子。采用X射线衍射(XRD)、透射电镜(TEM)、傅里叶红外光谱(FTTR)及热重(TG)对所制备样品的形貌和结构进行了表征。XRD表征结果显示：在[BMim]BF₄中制备的Ru具有六方紧密堆积结构,无氧化物峰出现;TEM结果显示：采用正滴法制备的Ru纳米粒子为球形颗粒,呈现良好的单分散状态,粒径分布窄,为2~5 nm,而采用反滴法制备的Ru纳米粒子则发生了严重的团聚,团聚体粒径大于10 nm;FTIR表征表明：Ru纳米粒子表面存在[BMim]BF₄液体层,分析二者之间存在较强的物理吸附作用,[BMim]BF₄在Ru纳米粒子的制备中起到了修饰剂和保护剂的双重作用,这一推论通过TG分析得到了进一步验证。将分散于[BMim]BF₄的Ru纳米粒子作为催化剂应用于苯选择加氢反应,结果分析表明：Ru-离子液体-苯反应体系中,苯转化率仅有0.3%;Ru-离子液体-苯-水反应体系中加氢活性较高,但环己烯选择性较低,在一定条件下,加氢30 min,苯转化率为27.3%,环己烯选择性仅为14.5%。     

Synthesis of Latex Particles with Surface Functional Groups and Their Applications for the Fabrication of Porous Materials

In this study, monodisperse latex particles with specific surface functional groups were synthesized by emulsifier-free emulsion polymerization. Amidine or carboxylated polystyrene nanospheres with narrow size distribution were prepared by emulsion polymerization using AIBA (α,α′-zodiisobutyramidine dihydrochloride) as amine-containing initiator or acrylic acid as carboxyl-containing comonomer, respectively. Factors affecting the particle size and distribution were systemically studied by changing the amount of initiator or monomer, the polymerization temperature, and the stirring speed of emulsion polymerization reactor. Monodisperse polymethylmethacrylate beads were also synthesized by soapless emulsion polymerization using methacrylic acid or aminoethylmethacrylate hydrogen hydrochloride as comonomer for the surface functionalization of the particles. As applications of the latex beads, the polymeric particles were adopted as templating materials for the fabrication of macroporous titania film and meso-macroporous silica particles by colloidal templating method.     

Highly monodisperse crosslinked polymethylmethacrylate microparticles by dispersion polymerization

Highly monodisperse polymethylmethacrylate (PMMA) microparticles crosslinked with carboxylic group-containing urethane acrylates (CUA) were produced by simple dispersion polymerization in methanol solution. In contrast to conventional crosslinkers, the CUA employed as a crosslinker was excellent for maintaining the monodispersity of PMMA microparticles even at moderate crosslinker concentrations (to about 5 wt%). It was believed that the CUA helped form the monomer-swellable surface of primary particles, because of the structurally long tetramethylene oxide groups in the molecule. Carboxylic groups in the molecular backbone resulted in larger primary particles by increasing the solubility of the monomer mixture in the medium. Owing to these larger primary particles, the crosslinked PMMA particles showed lower polymerization rates than the linear ones during particle growth. However, at high CUA concentrations (about 10 wt%), bimodal distributions were observed. This was attributed to the high crosslinking density of the primary particle surfaces. Therefore, monomer diffusion toward the polymer phase was restricted, resulting in more favorable secondary nucleation in the medium. Received: 12 May 1998 Accepted: 19 August 1998