乳液聚合法制备纳米金/聚苯乙烯复合粒子

以氯金酸为前驱体,十二烷基硫醇和硼氢化钠分别作为稳定剂和还原剂,采用相转移法制备了单分散的金纳米粒子.将金纳米粒子通过乳液聚合的方法制备了纳米金/聚苯乙烯复合粒子.通过紫外-可见吸收光谱(UV-Vis)研究了纳米金和纳米金/聚苯乙烯复合粒子的光吸收特性,使用傅立叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电子显微镜(TEM)和动态光散射(DLS)对产物的组成、晶体结构、形貌、以及粒径进行了表征.结果表明,复合粒子为粒径分布较窄的球形,其中的金纳米粒子为面心立方结构.热失重分析(TGA)说明制备的纳米金/聚苯乙烯复合粒子具有很好的热稳定性.     

PVP 稳定的纳米 Au 溶胶对葡萄糖液相选择氧化的催化性能

 采用化学还原法制备了聚乙烯吡咯烷酮 (PVP) 稳定的纳米 Au 溶胶, 这种 Au 溶胶在葡萄糖空气氧化制葡萄糖酸反应中具有良好的催化性能. 考察了 PVP 加入量和氯金酸前驱液的浓度对反应活性的影响. 紫外-可见吸收光谱和透射电镜分析结果表明, 含有较小 Au 粒子的 Au 溶胶体系具有较高的催化活性. 当 PVP/Au 质量比为 40, 氯金酸浓度为100 μg/ml 时, 得到稳定的 Au 溶胶体系具有金粒子尺寸小、分布均匀的特点, 对葡萄糖氧化反应活性高, 葡萄糖的转化率达到 54.4%.     

二苯胺磺酸钠还原法制备粒径可控的金纳米粒子

采用二苯胺磺酸钠还原四氯合金酸的方法,在室温条件下,用SDS(十二烷基硫酸钠)、SDBS(十二烷基苯磺酸钠)作表面活性剂,成功地合成了金纳米粒子.分别讨论了还原剂二苯胺磺酸钠、表面活性剂(SDS、SDBS)及四氯台金酸的浓度等对金纳米粒子的粒径和形貌的影响.通过控制反应条件,可以合成出平均粒径大约为10、14、30、36nm的金纳米粒子.利用透射电镜(TEN)、紫外-可见(UV-Vis)吸收光谱对金纳米粒子进行了表征.研究结果表明不同的SDS或SDBS/HAuCl4的摩尔比,对金纳米粒子的尺寸大小有影响.     

反相微乳液中憎水性纳米金的原位还原法合成

利用十八胺(C18NH2)/正丁醇/正庚烷/HAuCl4(aq)W/O型微乳液体系,在常温的碱促进条件下由正丁醇原位还原氯金酸合成了具有高度单分散的憎水性金纳米粒子。由C18NH2稳定的金纳米颗粒运用紫外可见光谱(UV-vis)、透射电镜(TEM)和X射线衍射(XRD)等分别进行了表征和分析,并探讨了微乳液体系各组分对形成金纳米粒子形貌、尺寸和单分散性的影响。结果显示,随十八胺/氯金酸摩尔比的增加,金粒子的尺寸逐渐减小而单分散性逐渐提高。在正丁醇原位慢还原氯金酸的过程中,实验所选W/O型微乳液模板和表面活性剂十八胺分子对憎水性金纳米粒子的形貌和尺寸仍具有良好的控制作用。     

纳米金粒子与R-藻红蛋白的相互作用

以NaBH4为还原剂, 采用化学还原法制备了纳米金溶胶, 发现以pH=7的金前驱液还原得到的纳米金粒子具有最强的紫外吸收(525 nm), 当以聚乙烯吡咯烷酮(PVP)为稳定剂时, 此吸收紫移到510 nm. TEM观察金粒子大小为5~8 nm. PVP、聚乙烯醇(PVA)和吐温-80等能较好地稳定纳米金粒子, 而十二烷基苯磺酸钠、PEG-1000和OP乳化剂等则没有稳定作用. 以紫外-可见光谱(UV-Vis)、X光荧光光谱(XRF)、透射电子显微镜(TEM)等研究了纳米金粒子与R-藻红蛋白的相互作用, 发现R-藻红蛋白本身对纳米金粒子具有良好的稳定作用. 当R-藻红蛋白与纳米金粒子共存时, R-藻红蛋白所具有的538 nm吸收带强度有所增强, 并发生紫移, 同时578 nm的荧光强度也明显减弱, 这表明R-藻红蛋白与纳米金粒子的相互作用对R-藻红蛋白的空间结构产生了影响, 导致位于R-藻红蛋白外缘藻红素发色团(PEB)的微环境发生了改变. 凝胶柱层析及分光光度分析结果进一步证实了金纳米粒子与藻红蛋白存在明显的相互作用, 这种相互作用可能与藻红蛋白分子中所包含的氨基基团有关.     

不同质子酸掺杂对银/聚苯胺纳米复合材料结构和导电性的影响

利用紫外光作为辅助条件,在反胶束体系中采用一步双原位法合成了硝酸(HNO3)、对甲基苯磺酸(TSA)和5-磺基水杨酸(SSA)掺杂的银/聚苯胺(Ag/PANI)纳米复合材料.通过对复合材料进行红外光谱(FTIR)、紫外光谱(UV-Vis)、扫描电镜(SEM)、X射线衍射(XRD)和导电性能的测试,研究了不同质子酸对Ag/PANI纳米复合材料结构、形貌和导电性能的影响.测试结果表明,3种酸掺杂制备的Ag/PANI纳米复合材料均为聚苯胺包覆银粒子的核-壳结构.不同的质子酸掺杂会对Ag/PANI纳米复合材料的电性能有重要影响.在3种酸掺杂的复合材料中,TSA掺杂的复合材料的电导率最佳,为215.14 S·cm-1.     

Au-Ag三角纳米环单层膜的原位转化制备及 SERS效应

利用模板牺牲氧化还原反应将自组装在基片上的三角板银纳米粒子(边长约为79.2 nm)与氯金酸溶液作用进而原位转化形成三角纳米环. 通过紫外-可见(UV-Vis)光谱实时监测基片上银三角板纳米粒子在反应不同阶段的消光特性; 扫描电子显微镜(SEM)显示了银三角板纳米粒子转化过程的形貌变化; 利用X射线光电子能谱(XPS)对其成分进行分析. 表征结果表明, 三角纳米环的成分为Au-Ag合金或复合物; 随着基片与氯金酸溶液作用时间的增加, 自组装膜的表面等离子体共振峰逐渐红移; Au-Ag三角环状纳米粒子的平均壁厚度从29.3 nm缩小至16.2 nm. 以4-巯基苯胺(4-ATP)为探针分子研究了该Au-Ag三角环状纳米粒子单层膜的表面增强拉曼(SERS)活性. 自组装单层膜基底的SERS信号随着Au-Ag三角纳米环平均壁厚度的增加逐渐增强.     

pH响应性树枝状聚合物-金纳米粒子复合药物载体的制备

以表面接枝聚乙二醇链的聚酰胺胺树枝状聚合物(PEG-PAMAM)为纳米载体, 在其内部空腔包覆金纳米粒子, 在金纳米粒子表面连接硫辛酸改性的阿霉素(LA-DOX), 从而间接实现了抗癌药物在PEG-PAMAM内的高效负载. 同时, LA-DOX中的酰腙键提供pH响应性, 实现了药物的pH响应性释放. 紫外-可见(UV-Vis)光谱表明, 包覆金纳米粒子的PEG-PAMAM纳米载体对LA-DOX的负载能力显著增强. 体外细胞实验表明, 负载LA-DOX的树枝状聚合物-金纳米粒子复合药物载体具有较强的抗肿瘤能力.     

壳聚糖-纳米金-葡萄糖氧化酶生物传感器的制备及其应用于葡萄糖的测定

采用了一种简便快捷的电沉积方法制备了壳聚糖-纳米金复合膜并应用于葡萄糖生物传感器的构建.氯金酸和壳聚糖的混合液在玻碳电极表面电化学还原为金纳米粒子,再将葡萄糖氧化酶通过戊二醛交联的方式固定在纳米金复合膜修饰的玻碳电极表面,制成一种新型的葡萄糖氧化酶生物传感器.该传感器对葡萄糖的响应十分快速,在5 S内即达到平衡.测定葡萄糖的线性范围为20μmol·L-1～5 mmol·L-1,检出限(3S/N)为12μmol·L-1.     

分子印迹聚合物负载纳米金催化剂的制备及其底物识别性能

以4-硝基苯甲醇与氯金酸的络合物为模板,利用聚合物空腔内胺基捕获NaBH4还原的纳米粒子,设计和制备了一种具有底物识别性能的分子印迹聚合物负载纳米Au催化剂(Au/MIP).运用红外光谱、紫外-可见光谱和扫描电镜等方法对催化剂进行了表征.同时以水为溶剂,过氧化氢为氧化剂,考察了催化剂在取代苯甲醇氧化反应中的催化性能.结...     

Morphology study of gold-chitosan nanocomposites

Gold nanoparticles were prepared in the presence of chitosan via reduction of HAuCl4 with sodium borohydride. The gold-chitosan nanocomposite was formed by adsorbing chitosan molecules onto the gold nanoparticle surfaces. The resulting gold nanoparticles were characterized by transmission electron microscopy and UV-vis spectroscopy. Morphology of gold-chitosan nanocomposite films was investigated by polarized optical microscopy. The morphology of chitosan crystal cast from the prepared nanocomposite was much different from that cast from chitosan solution due to the possible nucleation of gold nanoparticles. A branched-like structure or a cross-linked needle-like structure could be formed in nanocomposite films with different casting volumes.     

Adsorption characteristics of thionine on gold nanoparticles

Adsorption characteristics of thionine on gold nanoparticles have been studied by using UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), cyclic voltammetry and Fourier transform infrared spectroscopy. With the increasing concentration of gold nanoparticles, the absorption peak intensity of H-type dimers of thionine increases continuously, whereas that of monomers of thionine first increases and then decreases. The addition of gold nanoparticles makes the equilibrium between the monomer and H-type dimer forms of thionine move toward the dimer forms. Furthermore, the adsorption behavior of thionine on gold nanoparticles is also influenced by temperature. TEM images show that the addition of thionine results in an obvious aggregation, and further support the absorption spectral results. The fluorescence intensity of adsorbed thionine is quenched by gold nanoparticles due to the electronic interaction between thionine molecules and gold nanoparticles. Cyclic voltammetric and infrared spectroscopic studies show that the nitrogen atoms of both of the NH2 moieties of thionine strongly bind to the gold nanoparticle surfaces through the electrostatic interaction of thionine with gold nanoparticles. For 15-20 nm particles, the number of adsorbed thionine molecules per gold nanoparticle is about 7.66 x 10(4). Thionine molecules can not only bind to a particle to form a compact monolayer via both of the NH2 moieties, but they can also bind to two particles via their two NH(2) moieties, respectively.     

A novel immunoassay strategy based on combination of chitosan and a gold nanoparticle label

A novel immunoassay strategy based on combination of chitosan (CHIT) and a gold nanoparticle (GNP) label has been developed. The susceptibility of CHIT to further chemical modifications due to the abundant amino groups is explored in order to covalently immobilize antibody (Ab) onto the (3-aminopropyl) triethoxysilane derivatized glass slide by cross-linking with glutaraldehyde (GA). After incubating in antigen (Ag) solution, the obtained substrate is immersed in GNP labeled antibody solution for signal generation. The two steps were repeated alternatively for three times, forming multilayer of gold nanoparticles via antigen-antibody specific reaction. Ultraviolet-visible (UV-vis) absorption spectrum is recorded to obtain quantitative information about the specific antigen. The presented immunoassay strategy is applied for determination of human serum albumin (HSA) as a model analyte. The immunoassay of HSA is specific. Compared to previous correlative work, the proposed immunosensing strategy shows some advantages, such as improved sensitivity as much more gold nanoparticles can be coupled to the functionalized surface making use of the abundant amino groups of CHIT. Moreover, a significantly extended linear detection range of 8.0-512.0 μg/mL is gained under the optimized experimental conditions. In particular, the presented biosensing method shows low cost and simplicity, and only a conventional UV-vis detector is involved.     

A Xyloside-Based Ligand to Stabilize Gold Nanoparticles: Preparation and Application

Water-soluble and air-stable gold nanoparticles stabilized by a xyloside-based ligand containing a pyridine ring-functionalized 1,2,3-triazole backbone were prepared in the presence of a reducing agent. During their preparation, UV-vis and NMR spectroscopic techniques were used to study the interaction between the xyloside ligand and Au(III) ions. These AuNPs were characterized by UV-vis spectroscopy, TEM and DLS and showed a small size (average diameter<10 nm determined by TEM). Their catalytic activity was tested in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in water.     

Architecture of linear arrays of fluorinated co-oligomeric nanocomposite-encapsulated gold nanoparticles: a new approach to the development of gold nanoparticles possessing an extremely red-shifted absorption characteristic

Fluoroalkyl end-capped co-oligomeric nanoparticles, which were prepared by the reaction of fluoroalkanoyl peroxide with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 1-hydroxy-5-adamantylacrylate (Ad-HAc), were applied to the preparation of novel fluorinated co-oligomeric nanocomposite-encapsulated gold nanoparticles. These fluorinated gold nanocomposites were easily prepared by the reductions of gold ions with poly(methylhydrosiloxane) (PMHS) in the presence of the corresponding fluorinated nanoparticles and tri -n-octylamine (TOA) in 1,2-dichloroethane (DE) at room temperature. These fluorinated gold nanoparticles were isolated as wine-red powders and were found to exhibit good dispersibility in a variety of traditional organic solvents such as DE, methanol, and t-butyl alcohol to afford transparent wine-red solutions. The morphology and stability of these fluorinated co-oligomeic nanocomposite-encapsulated gold nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering measurements (DLS), and UV-vis spectroscopy. DLS measurements and UV-vis spectroscopy showed that these particles are nanometer-size-controlled very fine nanoparticles (185-218 nm) that exhibit a plasmon absorption band at around 530 nm. TEM images also showed that gold nanoparticles are tightly encapsulated into fluorinated co-oligomeric nanoparticle cores. Interestingly, these fluorinated co-oligomeric nanocomposites-encapsulated gold nanoparticles were found to afford linear arrays of these fluorinated nanoparticles with increases in the feed amounts of TOA. More interestingly, these fluorinated gold nanoparticles were able to afford the extremely red-shifted plasmon absorption band at around 960 nm.     

Polymer-mediated chain-like self-assembly of functionalized gold nanoparticles

We report an easy solution phase template-based method to assemble mercaptoundecanoic acid-functionalized gold nanoparticles (MUA-GNPs) along poly(ethylene oxide) (PEO) chains. Transmission electron microscopy (TEM) images show one-dimensional and two-dimensional chain-like sequences of GNPs resembling PEO chains. The progress of the assembly was monitored by the evaluation of surface plasmon resonance band of MUA-GNPs with time by UV-vis spectroscopy. The assembly process is a result of hydrogen bonding interaction between the ethereal oxygen of PEO and carboxylic acid group of MUA attached to GNPs surface, which was confirmed through FTIR spectroscopy. The interaction between PEO and MUA-GNPs was further confirmed by thermal analysis using differential scanning calorimetry.     

Synthesis of atomic gold clusters with strong electrocatalytic activities

Small atomic gold clusters in solution, Au n , stabilized by tetrabutyl ammonium bromide (TBABr), have been synthesized by a simple electrochemical technique, based on the anodic dissolution of a gold electrode in the presence of TBABr salt, and using acetronitrile as solvent. The presence of clusters in the range Au3-Au11 were detected by MALDI-TOF spectroscopy, and further characterized by UV-vis absorption spectroscopy, TEM, AFM, X-ray diffraction, and cyclic voltammetry. Clusters display a semiconductor behavior with a band edge of approximately 2.5 eV. We report here their extraordinarily high electrocatalytic activity toward the O2 reduction reaction in acid solutions, which can explain Zhang's results, showing that a four-electron mechanism seems to occur because of the facile reduction of H2O2 on gold clusters compared to bulk gold or larger gold nanoparticles.     

Control of gold nanoparticle aggregates by manipulation of interparticle interaction

The size of gold nanoparticle aggregates was controlled by manipulating the interparticle interaction. To manipulate the interparticle interaction of gold nanoparticles prepared by citrate reduction, we applied the substitutive adsorption of benzyl mercaptan on the particle surface in the absence of the cross-linking effect. Various experimental techniques such as UV-vis absorption spectroscopy, surface-enhanced Raman scattering, quasi-elastic light scattering, and zeta-potential measurement were used to characterize the nanoparticle aggregates. Our results suggest that the replacement of the trivalent citrate ions adsorbed on the nanoparticle surface with monovalent benzyl mercaptan ions should destabilize the particles, causing aggregation and hence the increase in the size of nanoparticle aggregates. These experimental results were successfully rationalized by the classical DLVO (Derjaguin-Landau-Vervey-Overbeek) theory that describes the interparticle interaction and colloidal stability in solution. Our findings suggest that the control of surface potential is crucial in the design of stable gold nanoparticle aggregates.     

<Emphasis Type="Italic">In situ</Emphasis> analysis of the formation steps of gold nanoparticles by oleylamine reduction

A colloidal solution of gold nanoparticles is synthesized with the use of sodium tetrachloroaurate(III) as a precursor, oleylamine as a reducer and surfactant, and 1-octadecene as a solvent. Reaction stages are analyzed in situ by optical (UV-vis) absorption spectroscopy with a simultaneous analysis of particle sizes by dynamic light scattering and X-ray absorption near edge spectroscopy for the analysis of the gold oxidation state. After the synthesis the size of obtained nanoparticles is determined by transmission electron microscopy. The analysis of the obtained experimental data reveals the presence of three main steps in the reduction reaction mechanism, corresponding to Au³⁺, Au⁺, Au⁰, which enables the construction of the reaction model. The reaction mechanism involves the formation of gold(I) complexes with oleylamine, followed by polymerization and the formation of gold nanoclusters coated with oleylamine.     

Synthesis of Core-Shell (Pd-Au) Bimetallic Nanoparticles in Microemulsions

Palladium-gold core-shell nanoparticles were synthesized in the aqueous domains of water in oil microemulsions by the sequential reduction of H₂PdCl₄ and HAuCl₄. The nanoparticles were characterized by ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). The UV-vis spectra confirm the presence of palladium nanoparticles after reducing H₂PdCl₄. These particles have been used as seeds for the core-shell particles. UV-vis spectra show that, after reducing HAuCl₄, the surface plasmon absorption of the nanoparticles is dominated by gold, revealing the encapsulation of the palladium seeds. These results agree with crystallographic analysis performed with high-resolution TEM pictures, as well as with selected area electron diffraction. The TEM pictures show the core-shell nanoparticles with an average diameter of 9.1 nm, as compared with 5 nm for the palladium seeds, in good agreement with the used Pd:Au molar ratio.