Effect of composition on the conductivity and morphology of poly(3-hexylthiophene)/gold nanoparticle composite Langmuir-Schaeffer films

Ultrathin Langmuir-Schaeffer (LS) films were fabricated from blends of regioregular poly(3-hexylthiophene) (P3HT) and highly monodispersed dodecanethiolate-capped gold nanoparticles (Au NPs) mixed in varying weight ratios. The morphology of the ultrathin films was investigated by UV-visible absorption spectroscopy, atomic force microscopy (AFM) and field-emission scanning electron microscopy (FE-SEM). The results of the structural investigations were correlated with the lateral conductivity of the films, with P3HT in its unintentionally doped state, probed by scanning electrochemical microscopy (SECM), which proved to be a very sensitive technique. Control over the P3HT/Au NP ratio led to remarkable changes in the morphology and lateral conductivity of the films. Inclusion of Au NPs into P3HT was found to influence the ordering of P3HT, which ultimately determined the macroscopic charge transport characteristics of the films. Composite films with ca. 33% by weight of Au NPs were found to be the most ordered and exhibited the highest conductivity, substantially higher than P3HT alone. To provide insight into the film formation process, LS composite films comprising equal quantities of P3HT and Au NPs (by weight) were transferred at several surface pressures and investigated by SECM, AFM and FE-SEM.     

Preparation of Ag Nanowire @ Au Nanoparticle Hybrid Nanowires and their Influence on the Fluorescence Properties of P3HT

In this study, the galvanic displacement reaction between silver and AuCl₄⁻ was carried out to synthesize a series of silver nanowire (Ag NW) @ gold nanoparticle (Au NP) hybrid nanowires. The influence of Ag NW @ Au NP hybrid nanowires on the fluorescence properties of the poly (3‐hexylthiophene) (P3HT) was investigated. The particle sizes of Au NPs on the hybrid nanowires could be adjusted by varying the reaction time and the concentration of the HAuCl₄ solution. Furthermore, steady‐state fluorescence measurements showed that the fluorescence intensity of the P3HT films was higher on various Ag NW @ Au NP hybrid nanowires compared to that on a bare silicon substrate. This was due to the increase in the intensity of electromagnetic field by the localized surface plasmon resonances of Au NPs and surface plasmon polaritons of Ag NWs from the hybrid nanowires. The results were further confirmed by the Raman spectra of the P3HT films on different substrates.     

Organosulfur-functionalized Au, Pd, and Au-Pd nanoparticles on 1D silicon nanowire substrates: preparation and XAFS studies

A hybrid preparative method was developed to prepare organosulfur-functionalized Au nanoparticles (NPs) on silicon nanowires (SiNWs) by reacting HAuCl(4) with SiNW in the presence of thiol. A number of organosulfur molecules-dodecanethiol, hexanethiol, 1,6-hexanedithiol, and tiopronin-were used to functionalize the Au surface. Size-selected NPs ranging from 1.6 to 7.5 nm were obtained by varying the S/Au ratio and the concentration of HAuCl(4). This method was further extended to the preparation Pd and Pd-Au bimetallic NPs on SiNWs. The morphology of the metal nanostructures was examined by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The local structure and bonding of the SiNW-supported metal nanostructures were studied using X-ray absorption fine structures (XAFS) [including both X-ray near-edge structures (XANES) and extended X-ray absorption fine structures (EXAFS)] at the Au L(3)-, Pd K-, S K-, and Si K-edges. It was also found that the annealing of the thiol-capped Au NPs up to 500 degrees C transforms the surface of the thiol-capped NPs to gold sulfide, as identified using Au L(3)- and S K-edge XANES. We also illustrate that this preparative approach can be used to form size-controllable Au NPs on carbon nanotubes.     

Synthesis of Au nanoparticles with Bi adlayers using glucose as dispersant

Well-dispersed Au/Bi nanoparticles with average size below 10 nm were prepared by using NaBH₄ to reduce HAuCl₄ with glucose as dispersant. The obtained Au/Bi NPs were well characterized by UV-Vis spectra, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements. The electrochemical study found that Bi adlayers on the surface of Au nanoparticles owns two kinds of surface structures, including a low coverage (2 × 2)-Bi adlayer and a close-packed (p × √3)-2 Bi adlayer due to the strong interaction between the two Bi layers and the below Au atoms, which is same with that bulk on Au surface.     

Fabrication of a novel glucose biosensor based on a highly electroactive polystyrene/polyaniline/Au nanocomposite

A novel nanocomposite with a core-shell structure containing polystyrene (PS), polyaniline (PANI), and Au nanoparticles (NPs) was synthesized. The nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetric experiments indicated that the nanocomposite had excellent redox ability in a wide range of pH values. The existence of Au NPs resulted in a higher electrical conductivity of the nanocomposite. As a model, glucose oxidase (GOD) was entrapped onto the nanocomposite-modified glassy carbon electrode (GCE) and applied to construct a sensor. The immobilized GOD showed a pair of well-defined redox peaks and high catalytic activity for the oxidation of glucose.     

应用于局域表面等离激元共振扫描显微探针的球形Au@Ag纳米粒子的合成及介电敏感性检测

局域表面等离激元共振(LSPR)显微探针的检测灵敏性主要取决于针尖上修饰的纳米粒子的LSPR性质.本文采用阴离子辅助法,在水溶液中通过调节Au核与Ag⁺的物质的量之比,实现Au核上不同厚度的Ag壳层包覆,可控地一步合成均一性好、银壳层较厚(≥10 nm)的核壳比不同的球形Au@Ag纳米粒子.通过扫描电镜(SEM)、透射电镜(TEM)及扫描透射电子显微镜X射线能谱(STM-EDS)线扫描分析对不同核壳比的Au@Ag纳米粒子进行形貌组成表征,证实了所合成核壳结构的可控性.将不同核壳比的Au@Ag纳米粒子置于不同折射率溶液中进行纳米粒子介电敏感性的研究,表明7.5 nm Au@28 nm Ag的纳米结构具有最高的品质因子.同时将不同核壳比的Au@Ag纳米粒子置于不同折射率的非导电性基底上进行单颗纳米粒子散射性质的研究,结果表明7.5 nm Au@28 nm Ag纳米粒子适合作为LSPR显微探针的高检测灵敏性纳米结构之一.     

低温静电自组装法制备贵金属修饰TiO_2纳米结构薄膜及其增强的光催化性能(英文)

以碱-水热法在金属Ti片上原位生长了TiO2纳米结构(纳米花和纳米线)薄膜,并采用低温静电自组装方法将超细贵金属(金、铂、钯)纳米颗粒均匀沉积于多孔TiO2薄膜上.负载于Ti片上的贵金属/TiO2纳米结构薄膜具有一体化结构、多孔架构和高光催化活性.超高分辨率场发射扫描电子显微镜(FESEM)直接观察表明贵金属纳米颗粒在TiO2表面分布均匀,且颗粒之间相互分离,金、铂、钯纳米颗粒的平均粒径分别约为4.0、2.0和10.0nm.俄歇电子能谱(AES)纵深成分分析表明贵金属不仅沉积于薄膜表面,且大量分布于TiO2纳米结构薄膜内部,其深度超过580 nm.X射线光电子能谱(XPS)分析表明,经300°C下在空气中热处理后,纳米金仍保持金属态,纳米铂部分被氧化成PtOabs,而钯粒子则完全被氧化成氧化钯(PdO).以低温静电自组装法沉积贵金属,贵金属负载量可通过调节组装时间与溶胶pH值来控制.光催化降解甲基橙的结果表明,沉积的纳米金和铂能显著增加TiO2纳米结构薄膜的光催化活性,说明金和铂粒子可促进光生载流子的分离;但负载的PdO对TiO2薄膜的光催化性能增强几乎无作用.     

Ion-exchange synthesis and improved photovoltaic performance of CdS/Ag2S heterostructures for inorganic-organic hybrid solar cells

A facile ultrasound-assisted ion exchange route was developed for the synthesis of CdS/Ag₂S heterojunctions by ion exchange between the nanostructured CdS film and [Ag(NH₃)₂]⁺ under ultrasonication. The CdS/Ag₂S heterojunction film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis DRS spectroscopy, photoelectrochemical measurements, and the transient photovoltage (TPV) technique. CdSAg₂S heterojunctions exhibit a dense morphology, enhanced visible light absorption and stronger photocurrent response than the pure CdS films. Poly(3-hexylthiophene) (P3HT) was then spin coated into the CdS/Ag₂S framework. Hybrid solar cells constructed with FTO/CdS/Ag₂S/P3HT/Au display relatively higher power conversion efficiency than FTO/CdS/P3HT/Au.     

Controlled dispersion of polystyrene‐capped Au nanoparticles in P3HT:PC61BM and consequences upon active layer nanostructure

Numerous recent publications detail higher absorption and photovoltaic performance within organic photovoltaic (OPV) devices which are loaded with Au or Ag nanoparticles to leverage the light management properties of the localized surface plasmon resonance (LSPR). This report details the impact upon film morphology and polymer/nanoparticle interactions caused by incorporation of polystyrene‐coated Au nanoparticles (Au/PS) into the P3HT:PC₆₁BM bulk heterojunction film. Nanostructural analysis by transmission electron microscopy and X‐ray scattering reveals tunable Au/PS particle assembly that depends upon the choice of casting solvent, polymer chain length, film drying time, and Au/PS particle loading density. This Au/PS particle assembly has implications on the spectral position of the Au nanoparticle LSPR, which shifts from 535 nm for individually dispersed particles in toluene to 650 nm for particles arranged in large clusters within the P3HT:PC₆₁BM matrix. These results suggest a critical impact from PS/P3HT phase separation, which causes controlled assembly of a separate Au/PS phase in the nanoparticle/OPV composite; controlled Au/PS phase formation provides a blueprint for designing AuNP/OPV hybrid films that impart tunable optical behavior and potentially improve photovoltaic performance. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 709–720     

Electrochemical solid-state phase transformations of silver nanoparticles

Adenosine triphosphate (ATP)-capped silver nanoparticles (ATP-Ag NPs) were synthesized by reduction of AgNO(3) with borohydride in water with ATP as a capping ligand. The NPs obtained were characterized using transmission electron microscopy (TEM), UV-vis absorption spectroscopy, X-ray diffraction, and energy-dispersive X-ray analysis. A typical preparation produced ATP-Ag NPs with diameters of 4.5 ± 1.1 nm containing ~2800 Ag atoms and capped with 250 ATP capping ligands. The negatively charged ATP caps allow NP incorporation into layer-by-layer (LbL) films with poly(diallyldimethylammonium) chloride at thiol-modified Au electrode surfaces. Cyclic voltammetry in a single-layer LbL film of NPs showed a chemically reversible oxidation of Ag NPs to silver halide NPs in aqueous halide solutions and to Ag(2)O NPs in aqueous hydroxide solutions. TEM confirmed that this takes place via a redox-driven solid-state phase transformation. The charge for these nontopotactic phase transformations corresponded to a one-electron redox process per Ag atom in the NP, indicating complete oxidation and reduction of all Ag atoms in each NP during the electrochemical phase transformation.     

Gold nanoparticle-catalyzed environmentally benign deoxygenation of epoxides to alkenes

We have developed a highly efficient and green catalytic deoxygenation of epoxides to alkenes using gold nanoparticles (NPs) supported on hydrotalcite [HT: Mg(6)Al(2)CO(3)(OH)(16)] (Au/HT) with alcohols, CO/H(2)O or H(2) as the reducing reagent. Various epoxides were selectively converted to the corresponding alkenes. Among the novel metal NPs on HT, Au/HT was found to exhibit outstanding catalytic activity for the deoxygenation reaction. Moreover, Au/HT can be separated from the reaction mixture and reused with retention of its catalytic activity and selectivity. The high catalytic performance of Au/HT was attributed to the selective formation of Au-hydride species by the cooperative effect between Au NPs and HT.     

Combining optical lithography with rapid microwave heating for the selective growth of Au/Ag bimetallic core/shell structures on patterned silicon wafers

We demonstrate a novel approach for the production of patterned films of nanometer-sized Au/Ag bimetallic core/shell nanoparticles (NPs) on silicon wafers. In this approach, we first self-assembled monodisperse Au NPs, through specific Au...NH(2) interactions, onto a silicon substrate whose surface had been modified with a pattern of 3-aminopropyltrimethoxysilane (APTMS) groups to form a sandwich structure having the form Au NPs/APTMS/SiO(2). These Au NPs then served as seeds for growing the Au/Ag bimetallic core/shell NPs: we reduced silver ions to Ag metal on the surface of Au seeds under rapid microwave heating in the presence of sodium citrate. Energy-dispersive X-ray analysis confirmed that the Au/Ag bimetallic core/shell NPs grew selectively on the regions of the surface of the silicon wafer that had been patterned with the Au seeds. Scanning electron microscopy images revealed that we could synthesize well-scattered, high-density (>82%) thin films of Au/Ag bimetallic core/shell NPs through the use of this novel strategy. The patterned structures that can be formed are simple to produce, easily controllable, and highly reproducible; we believe that this approach will be useful for further studies of nanodevices and their properties.     

Electrodeposited Cu‐Au Alloy Nanoparticles for Uric Acid Electrochemical Biosensor with Quick Response

A uric acid (UA) electrochemical biosensor based on the Cu‐Au alloy nanoparticles (NPs) and uricase was developed. The electrodeposition technique of Cu‐Au alloy NPs was selected to be a convenient potentiostatic method at –0.8 V in a single solution containing both Au(III) and Cu²⁺. Cyclic voltammetry and scanning electron microscopy proved the successful deposition of Cu‐Au alloy NPs. EIS demonstrated the good conductivity of Cu‐Au alloy NPs. The enzyme was immobilized on the surface of Cu‐Au alloy NPs modified electrode by casting with chitosan solution. The ultimate biosensor showed linear amperometric response towards UA in the concentration range of 3.0 to 26.0 μM with a detection limit of 0.8 μM. The main feature of the biosensor was its short response time, which was attributed to the good conductivity of Cu‐Au alloy NPs. Furthermore, the biosensor could avoid the interference of ascorbic acid and oxygen.     

Preparation, structure, and optical properties of nanoporous gold thin films

Thin nanoporous gold (np-Au) films, ranging in thickness from approximately 40 to 1600 nm, have been prepared by selective chemical etching of Ag from Ag/Au alloy films supported on planar substrates. A combination of scanning electron microscopy (SEM) imaging, synchrotron grazing incidence small angle X-ray scattering, and N2 adsorption surface area measurements shows the films to exhibit a porous structure with intertwined gold fibrils exhibiting a spectrum of feature sizes and spacings ranging from several to hundreds of nanometers. Spectroscopic ellipsometry measurements (300-800 nm) reveal the onset of surface plasmon types of features with increase of film thicknesses into the approximately 200 nm film thickness range. Raman scattering measurements for films functionalized with a self-assembled monolayer formed from 4-fluorobenzenethiol show significant enhancements which vary sharply with film thickness and etching times. The maximum enhancement factors reach approximately 10(4) for 632.8 nm excitation, peak sharply in the approximately 200 nm thickness range for films prepared at optimum etching times, and show high spot to spot reproducibility with approximately 1 microm laser spot sizes, an indication that these films could be useful as durable, highly reproducible surface-enhanced Raman substrates.     

Electrochemical fabrication of large-area Au/TiO2 junctions

Electrically continuous Au thin films were prepared on polycrystalline TiO₂ by pulsed galvanostatic electrodeposition. Large-area electrically continuous films 10–30 nm in thickness and approximately 0.25 cm² in area were created using a series of 5 ms bipolar current pulses. The film morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) which showed a network of interconnected Au islands. The electrical properties of the resulting Schottky junction were also investigated and the conduction was found to deviate considerably from ideal thermionic emission. The effective barriers were higher than in Au/TiO₂ junctions prepared by electron beam evaporation.     

Engineering inorganic hybrid nanoparticles: tuning combination fashions of gold, platinum, and iron oxide

Multistep colloidal chemical routes were employed to synthesize Pt/Au, Pt/iron oxide (IO), and Au/Pt/IO hybrid nanoparticles (NPs). The starting templates, Pt NPs, were synthesized by controlling the decomposition kinetics of platinum acetylacetonate in oleylamine. The morphologies of binary metal Pt/Au hybrid NPs were modulated by controllable attachment of Au nanoscale domains to Pt templates. Similarly, Pt/IO and Au/Pt/IO hybrid NPs were fabricated by the controllable attachment of Fe to the Pt or Pt/Au template NPs. The noble metal domains of as-prepared hybrid NPs had face center cubic crystal structures and did not alloy, as verified by high resolution transmission electron microscopy and X-ray diffraction spectrometry. X-ray diffraction spectrometry study indicates that the IO domains in the as-prepared NPs have a spinel structure. UV-vis study of binary metal Pt/Au hybrid NPs revealed that they have a characteristic plasmon resonance around 525 nm, while dumbbell-like Au/Pt/IO NPs had a plasmon resonance around 600 nm. Furthermore, magnetism study of the binary Pt-IO NPs clearly indicated that the interfacial interactions between Pt and IO domains could result in a shift of the blocking temperature.     

Biosynthesis of gold nanoparticles using Pseudomonas aeruginosa

Pseudomonas aeruginosa were used for extra-cellular biosynthesis of gold nanoparticles (Au NPs). Consequently, Au NPs were formed due to reduction of gold ion by bacterial cell supernatant of P. aeruginosa ATCC 90271, P. aeruginosa (2) and P. aeruginosa (1). The UV-vis and fluorescence spectra of the bacterial as well as chemical prepared Au NPs were recorded. Transmission electron microscopy (TEM) micrograph showed the formation of well-dispersed gold nanoparticles in the range of 15-30 nm. The process of reduction being extra-cellular and may lead to the development of an easy bioprocess for synthesis of Au NPs.     

Facile synthesis of gold nanoparticles in aqueous acrylamide solution

A method is advanced for preparing gold nanoparticles (NPs) at 50°C in aqueous acrylamide (AAm), which has the dual function of a reducing agent for HAuCl₄ and a protective ligand for NPs. Nanoparticles have gold cores with the average size d_Au = 20.9 ± 3.6 nm. The growth kinetics of NPs has been studied. Films of NPs have been produced on glass, silica, silicon, and polyethylene terephthalate (PET) substrates. The NPs and films have been characterized by UV-Vis and IR spectroscopy, X-ray powder diffraction, transmission and scanning electron microscopy, and atomic-force microscopy.     

金/氧化亚铜异质球的制备及其可见光催化性能

使用L-半胱氨酸作为连接剂, 利用硼氢化钠原位还原预先吸附在介孔氧化亚铜表面的氯金酸根离子,得到了Au/Cu₂O异质结构. 应用X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱和N₂物理吸附等手段对催化剂进行表征, 并以λ>400 nm的可见光作为光源, 评价了该催化剂光催化降解亚甲基蓝(MB)的活性. 实验结果表明, 直径为4 nm的金颗粒完好地负载在介孔氧化亚铜的表面, 并且介孔氧化亚铜的细微结构与孔径均未发生变化. 研究表明, 以乙醇作为反应溶剂有效抑制了AuCl₄^-与Cu₂O之间的氧化还原反应, 从而有利于氧化亚铜介孔结构的保持及金颗粒的原位还原. 光催化降解亚甲基蓝的结果表明, Au/Cu₂O异质结构的光催化活性比纯氧化亚铜光催化活性有明显提高. 推测其光催化性能提高的主要原因如下: 一方面, 金颗粒良好的导电性有利于氧化亚铜表面电子的快速转移, 实现电子-空穴分离; 另一方面, 金颗粒可能存在的表面等离子共振现象加速了光生电子的产生.     

内部具有可移动金核的中空银纳米颗粒的制备、表征及其表面增强拉曼效应

采用振荡法和种子生长技术制备出核壳结构的Au@SiO2纳米颗粒及夹层结构的Au@SiO2@Ag纳米颗粒, 用HF将Au@SiO2@Ag NPs夹层的SiO2溶解, 得到内部带有粒径为30 nm的可移动金核、壳层厚度约为30 nm的中空银纳米颗粒(Au@air@Ag NPs). 用扫描电子显微镜和透射电子显微镜对所得到的纳米微球的形貌进行了表征, 并以罗丹明B为探针分子研究了Au@air@Ag 纳米颗粒的表面增强拉曼(SERS)效应, 发现Au@air@Ag 纳米颗粒是一种可应用于SERS的理想材料.