SnO2纳米粒子作为SERS基底的研究

采用溶胶-水热法制备了不同尺寸的SnO2纳米粒子, 并将其作为表面增强拉曼散射(Surface-enhanced Raman scattering, SERS)活性基底, 重点探讨了表面缺陷能级与SERS性能的关系. 观察到4-巯基苯甲酸(4-MBA)吸附在150 ℃水热合成的SnO2纳米粒子上的SERS 信号最强, 随着在空气中煅烧温度的升高, SERS信号逐渐减弱. 分别用透射电子显微镜、 紫外-可见光谱、 荧光光谱、 X射线衍射和X射线光电子能谱对SnO2纳米粒子进行了表征. 结果表明, SnO2纳米粒子的表面氧空位和缺陷等表面性质在增强拉曼散射性能中发挥着重要的作用, 表面氧空位和缺陷等含量越高其SERS信号就越强.     

纳米Ag/TiO_(2)纳米管阵列基底构建及表面增强拉曼散射光谱检测与降解盐酸四环素北大核心CSCD

将阳极氧化与光还原法结合,在TiO_(2)纳米管阵列(TiO_(2)NTAs)表面修饰Ag纳米粒子,获得一种均匀有序、稳定性高且可循环的TiO_(2)NTAs/Ag活性基底。采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)、表面增强拉曼散射光谱(SERS)和扫描电子显微镜(SEM)等手段对TiO_(2)NTAs/Ag的组成和结构进行了表征。进一步研究了该TiO_(2)-NTAs/Ag阵列对盐酸四环素(TC-HCl)的SERS响应,结果表明,该复合基底对TC-HCl具有较高的检测灵敏度,在水中检测限可达1×10^(−14) mol/L,而TiO_(2)-NTAs与Ag之间的协同效应对其检测性能的提高起着关键作用。此外,TiO_(2)NTAs/Ag基底在光照下对TC-HCl展示了优异的降解活性,且至少可循环使用8次。表明该TiO_(2)NTAs/Ag基底在环境中有机污染物的SERS检测和降解领域具有潜在的应用前景。     

室温电子还原制备金纳米颗粒与琼脂糖复合膜的表征与应用

利用室温电子还原技术合成了一种金纳米颗粒与琼脂糖复合膜。合成过程采用氩气辉光放电为廉价电子源,方便快捷,绿色环保。通过紫外-可见(UV-Vis)分光光度计、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射(XRD)仪、光电子能谱(XPS)等表征,发现可以通过改变氯金酸浓度调控复合膜中金纳米颗粒的分布,加入聚乙烯吡咯烷酮(PVP)可有效控制金纳米颗粒的形貌。由于复合膜具有金纳米颗粒密集排布的结构,可作为表面增强拉曼散射(SERS)活性基底。实验表明,以对氨基苯硫酚为探针,该复合膜作为SERS基底,SERS平均增强因子超过了106,检测限达到了10-12mol?L-1。除此之外,作为SERS基底,复合膜具有良好的均一性和稳定性。     

Strong metal-support interactions between gold nanoparticles and ZnO nanorods in CO oxidation

The catalytic performances of supported gold nanoparticles depend critically on the nature of support. Here, we report the first evidence of strong metal-support interactions (SMSI) between gold nanoparticles and ZnO nanorods based on results of structural and spectroscopic characterization. The catalyst shows encapsulation of gold nanoparticles by ZnO and the electron transfer between gold and the support. Detailed characterizations of the interaction between Au nanoparticles and ZnO were done with transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR), and FTIR study of adsorbed CO. The significance of the SMSI effect is further investigated by probing the efficiency of CO oxidation over the Au/ZnO-nanorod. In contrast to the classical reductive SMSI in the TiO(2) supported group VIII metals which appears after high temperature reduction in H(2) with electron transfer from the support to metals, the oxidative SMSI in Au/ZnO-nanorod system gives oxygen-induced burial and electron transfer from gold to support. In CO oxidation, we found that the oxidative SMSI state is associated with positively charged gold nanoparticles with strong effect on its catalytic activity before and after encapsulation. The oxidative SMSI can be reversed by hydrogen treatment to induce AuZn alloy formation, de-encapsulation, and electron transfer from support to Au. Our discovery of the SMSI effects in Au/ZnO nanorods gives new understandings of the interaction between gold and support and provides new way to control the interaction between gold and the support as well as catalytic activity.     

Thin films of Ag nanoparticles prepared from the reduction of AgI nanoparticles in self-assembled films

A novel method for the preparation of thin films of Ag nanoparticles is reported. Using mercaptoacetic acid as the stabilizing agent, AgI nanoparticles were prepared in aqueous solution. And based on electrostatic interactions, the thiol-passivated AgI nanoparticles were assembled in a self-assembled film by alternative deposition with a cationic polyelectrolyte. Then the AgI nanoparticles in the composite film were reduced by NaBH(4), which resulted in the formation of a thin film of Ag nanoparticles. UV-visible spectra and X-ray photoelectron spectroscopy data confirmed the transformation from AgI to Ag. Atomic force microscopy (AFM) showed that the formed Ag nanoparticles distributed on the film homogeneously. Surface-enhanced Raman spectroscopy (SERS) measurement indicated that the prepared thin films could be used as effective SERS substrates. The reduction process was also carried out by UV light at selective surface regions, which resulted in the formation of patterned nanoparticle arrays.     

Aggregation of photolytic gold nanoparticles at the surface of chitosan films

Formation and aggregation of photolytic gold nanoparticles at the surface of chitosan (CTO) films have been investigated. When thin films of chloroauric acid salt of CTO were irradiated with UV light in wet air at room temperature for 10 min, gold nanoparticles of approximately 10 nm size are formed at the film surface. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize gold nanoparticles at the film surface. The shift of Au(4f) peak to the higher energy side and broadening of full width at half-maximum in the XPS spectrum are the direct evidence of the existence of gold atoms and small clusters in the early stage of photolysis. According to FE-SEM observation, growth in the particle diameter and aggregation of nanoparticles were observed after prolonged irradiation, and, finally, the film surface was densely covered with gold particles of 20-100-nm size. Gold atoms and clusters could move in the film and precipitate to the irradiated surface. Chemical composition analysis further suggests that gold particles at the surface are covered with an ultrathin CTO layer, which is partly oxidized by oxygen and chlorinated by chlorine during photochemical reactions.     

X-ray photoelectron spectroscopic studies of charge transfer interactions in electroactive polyaniline

Four modes of charge transfer interactions in polyaniline (PAN), viz. acid protonation, self-doping, charge transfer interactions with organic acceptors, and charge transfer interactions with surface grafted functional polymers have been studied by X-ray photoelectron spectroscopy (XPS). In the case of acid protonation, the protonation behavior of volatile and non-volatile acid differs. The structures of sulfonated leucomeraldine (LM) and nigraniline (NA) are similar to those of sulfonated and self-protonated emeraldine (EM). A substantially higher degree of charge transfer interaction with the organic acceptors is observed for EM film that has been subjected to one cycle of acid/base treatment. The charge transfer interactions with the organic acceptors have proceeded further than the pure formation of molecular complexes. Both pristine and Ar plasma or O₃ pretreated EM films are susceptible to surface modifications by graft copolymerization. The protonic acid functional groups of the graft readily give rise to a self-protonated EM surface.     

Preparation of Luminescent Polyelectrolyte/Cu-Doped ZnSe Nanoparticle Multilayer Composite Films

ZnSe and Cu-doped ZnSe nanoparticle aqueous suspensions were prepared in the presence of mercaptopropionic acid (MPA). Cu-doped ZnSe nanoparticles exhibited a strong blue emission that was strongly dependent upon the Cu dopant level and the chemical surface passivation produced by zinc-mercaptopropionic acid complexes. These Cu-doped ZnSe nanoparticles were further assembled into ultrathin polymer-supported films using electrostatic interactions and the layer-by-layer assembly method. UV-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) provided evidence for the presence and optical activity of Cu-doped ZnSe nanoparticles within the polymer ultrathin films. Moreover, XPS data supported the presence of zinc mercaptopropionic acid complexes on nanoparticle surfaces and the presence of Cu(+) ions with high luminescent activity in the doped nanoparticles. Copyright 2001 Academic Press.     

聚苯胺包裹的金纳米粒子的合成和表征及初步应用

用苯胺作还原剂还原氯金酸合成了金纳米结构. TEM实验表明, 苯胺还原氯金酸能生成苯胺齐聚物或其聚合物包裹的金球形纳米粒子. XPS分析表明, 金纳米粒子包覆的聚合物层带正电荷. 该纳米粒子能用于电极表面纳米结构组装及氧化还原性的生物大分子的电化学研究, 实现了超氧化物歧化酶(SOD)在这种带正电荷的金纳米粒子表面的直接电子转移.     

Au纳米粒子负载的ZnO空心球复合材料的光生电荷转移行为及光催化活性

通过简单的两步法合成了不同负载量的Au/ZnO空心球。采用扫描电子显微镜(SEM),X射线衍射(XRD),X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)对样品的形貌、结构、组成和晶相等进行一系列的表征。以罗丹明B (RhB)为目标降解物,探究了Au/ZnO空心球的光催化活性。结果表明,适量Au修饰的ZnO光催化剂在混合光下20 min内对RhB的降解率达到73%。利用表面光电压谱(SPS)和瞬态光电压(TPV)技术,探讨了Au修饰后对ZnO光诱导电荷转移行为与光催化性能之间的关系。结果表明,混合光照下Au/ZnO空心球光降解性能的提高主要归因于作为电子受体的Au纳米粒子与ZnO之间形成的强的电子相互作用。适量Au纳米粒子的负载能够提高ZnO空心球中光生载流子的分离效率,相应地延长载流子的传输时间,增加光生电荷的寿命,从而促进其光催化活性的提高。     

Study of the affinity of thermographic additives for silver by time-of-flight static secondary ion mass spectrometry and surface-enhanced Raman spectroscopy on silver nanoparticles

Detection of the interactions between low molecular weight organic compounds and metals in the form of sols on a nanoscale is analytically challenging. This study aims to provide experimental evidence using a combination of UV-Vis absorption spectrometry, surface-enhanced Raman spectrometry (SERS), and static secondary ion mass spectrometry (S-SIMS). The field of application is thermography where silver images are formed via heat-catalyzed reactions. Several organic compounds called tone modifiers and stabilizers are used in thermographic materials for the optimization of the image quality. With exploitation of the strengths of each of the above-mentioned methods, an affinity ranking of several tone modifiers and a stabilizer was established on the basis of competitive adsorption experiments using different model systems. Specifically, silver sols, SERS probes, and sputter-coated silver substrates were exposed to systems with one or two additives. The UV-Vis results provided insight on the aggregation of silver nanoparticles in a hydrosol, which was necessary for the interpretation of the SERS data. Both SERS and S-SIMS measurements led to a similar ranking of the relative affinity of the additives in two components, which was largely consistent with empirical knowledge derived from macroscopic behavior.     

ZnO/graphene-oxide nanocomposite with remarkably enhanced visible-light-driven photocatalytic performance

In this work, a high-performance photocatalyst of ZnO/graphene-oxide (ZnO/GO) nanocomposite was synthesized via a facile chemical deposition route and used for the photodegradation of organic dye from water under visible light. The nanocomposite was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller N(2) adsorption-desorption analysis, and UV-Vis diffusion reflectance spectroscopy. The ZnO/GO nanocomposite consisting of flower-like ZnO nanoparticles anchored on graphene-oxide sheets has a high surface area and hierarchical porosity, which is benefit to the adsorption and mass transfer of dye and oxygen species. For the photodegradation of organic dyes under visible light, ZnO/GO nanocomposite exhibited remarkably enhanced photocatalytic efficiency than graphene-oxide sheets and flower-like ZnO particles. Moreover, the photocatalytic efficiency of ZnO/GO nanocomposite could be further improved by annealing the product in N(2) atmosphere. The outstanding photocatalytic performance was ascribed to the efficient photosensitized electron injection and repressed charge carriers recombination in the composite with GO as electron collector and transporter, thus leading to continuous generation of reactive oxygen species for the degradation of methylene blue.     

金纳米粒子组装体系SERS化学增强的研究

Gold nanoparticles were assembled on gold substrates with the self-assembled monolayer(SAM) of p-minothiophenol(PATP). AFM measurements disclose that gold nanoparticles are scattered over the surface of the substrate with a submonolayer coverage. The Raman signal of the coupling layer, the SAM of PATP, can be well observed. Potential-dependent measurements were performed to study the chemical enhancement in SERS of such a system. Based on the supposition that the direction of charge transfer is from gold nanoparticles to PATP, it is deduced that Herzberg-Teller contribution has ruled in the SERS of such a system.     

Synthesis of gold nanoparticles from an organometallic compound in supercritical carbon dioxide

This article presents the synthesis of gold nanoparticles in a single-phase supercritical fluid carbon dioxide solvent. The gold nanoparticles were formed by the reduction of triphenylphosphine gold(I) perfluorooctanoate with dimethylamineborane. Transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy reveal the formation of gold nanoparticles of 1 nm in diameter. A high dispersion stability of the gold nanoparticles in supercritical carbon dioxide can be obtained by binding both triphenylphosphine and fluorocarbon ligands on the surface of the gold nanoparticles.     

具有温度响应壳层的金纳米粒子的制备

利用可逆-加成断裂链转移聚合得到全亲水性的嵌段共聚物(PEO-b-PNIPAM), 通过"grafting to"使其接枝到金纳米粒子表面. 通过透射电子显微镜、 紫外-可见吸收光谱、 能谱分析及动态光散射研究了杂化的金纳米粒子的壳层结构及温度响应行为. 实验结果表明, 得到核壳结构的金纳米粒子, 同时其壳层具有温度响应行为. 随着温度的升高, 其流体力学半径略有减小. 在整个升温过程中, 由于外层PEO链段的抑制作用, 没有发生粒子间的聚集.     

Study of molecular trapping inside gold nanofinger arrays on surface-enhanced Raman substrates

The binding of trans-1,2-bis(4-pyridyl)-ethylene (BPE) molecules on substrates arrayed with flexible gold nanofingers has been studied by surface-enhanced Raman spectroscopy (SERS) and angle-resolved X-ray photoelectron spectroscopy (AR-XPS). On the basis of the SERS and XPS results, BPE molecules are found to interact with the gold nanofingers through the lone pair electrons of pyridyl nitrogens, not through delocalized π electrons. Furthermore, after comparing the AR-XPS spectra of finger arrays preclosed before exposure to BPE with the spectra of arrays that closed after exposure to BPE, we observed in the latter case, at grazing takeoff angles, an increase in the component of the nitrogen photoelectron peak associated with pyridyl nitrogen atoms residing on bridging sites. These results demonstrate that a small percentage of BPE molecules was trapped between the neighboring gold finger tips during the finger closing process. However, because these trapped BPE molecules coincidently resided in the hot spots formed among the touching finger tips, the substantial increase in the observed SERS signal was dominated by the contribution from this small minority of BPE molecules.     

Cu掺杂TiO_2作为SERS基底的研究

本文采用溶胶-水热法制备了TiO2及Cu掺杂的TiO2纳米粒子作为表面增强拉曼光谱(SERS)活性基底,观察到当4-巯基苯甲酸吸附在3%Cu掺杂的TiO2表面上时,其SERS信号得到了最大程度的增强.Cu离子掺杂进TiO2晶格时会使TiO2表面的缺陷浓度(表面态)得到增加,一定量的缺陷浓度对TiO2-to-Molecule的电荷转移机理起到促进作用,进一步证明了化学增强机理在SERS现象的贡献.     

Synthesis of dense poly(acrylic acid) brushes and their interaction with amine-functional silsesquioxane nanoparticles

Poly(acrylic acid) polyelectrolyte brushes were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of tert-butyl acrylate on planar gold surfaces and subsequent hydrolysis. Three types of monolayers with different numbers of thiol binding sites per initiating unit were used. The binding strength to the gold surface turned out to be of crucial importance for the formation of uniform brush layers after acidic hydrolysis. The monolayers and polymer brushes were characterized by ellipsometry, infrared spectroscopy, water contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. Their interaction with [(diglycidylamino)propyl]silsesquioxane nanoparticles at various pH values was studied by surface plasmon resonance.     

Self-assembly of gold nanoparticles to carbon nanotubes using a thiol-terminated pyrene as interlinker

Gold nanoparticles were self-assembled onto the surface of solubilized carbon nanotubes through an interlinker of bi-functionalized molecule (PHT) terminated with pyrenyl unit at one end and thiol group at the other end. While the fluorescence of PHT is quenched moderately by the carbon nanotubes, the fluorescence is almost totally quenched by the further binding of gold nanoparticles. The enhancement of the Raman responses of nanotubes by the gold nanoparticles is also observed. These results imply there are charge transfer interactions between nanotubes and gold nanoparticles.     

Oxadiazole‐2‐thiol Adsorption on Gold Nanorods: A Joint Theoretical and Experimental Study by Using SERS,XPS, and DFT

The chemisorption of 1,3,4‐oxadiazole‐2‐thiol (ODT) on gold nanorods has been investigated by using surface‐enhanced Raman spectroscopy (SERS) and density functional theory (DFT). Although most of the SERS spectra have remarkable similarity to the normal Raman spectra of the pure analyte, the adsorption of ODT on a gold surface leads to a drastic change in its Raman spectrum and distinct vibrational features are obtained with gold nanorods and spherical nanoparticles. Simulated Raman spectra for hybrid systems that consist of an oxadiazole moiety coordinated to a Au₂₀ gold cluster provided valuable information about the coordination mode and enabled us to assign vibration modes.