Electrooxidation of ethylene glycol using gold nanoparticles electrodeposited on pencil graphite in alkaline medium

The electrooxidation of ethylene glycol(EG) on the surface of gold nanoparticles(AuNPs) in alkaline medium was investigated.AuNPs were electrodeposited on pencil graphite(PG) by fast scan cyclic voltammetry.Different sizes of AuNPs deposited on the surface of PG(AuNPs/PG) were used for the electrooxidation process.AuNPs were electrodeposited on PG at various deposition times in the same potential range but with different scan rates and scan cycles.Scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray diffraction(XRD) were used to visualize and characterize the prepared AuNPs/PG electrodes.Cyclic voltammograms were also used to investigate the electrooxidation of EG.The effects of EG and supporting electrolyte concentrations,scan rate,particle size of AuNPs and final potential limit on the electrooxidation process have been investigated.Further studies showed that the electrooxidation of EG is affected by temperature of the medium.The prepared AuNPs showed stability after long-term use.     

Amphiphilic Janus Gold Nanoparticles Prepared by Interface‐Directed Self‐Assembly: Synthesis and Self‐Assembly

Materials with Janus structures are attractive for wide applications in materials science. Although extensive efforts in the synthesis of Janus particles have been reported, the synthesis of sub‐10 nm Janus nanoparticles is still challenging. Herein, the synthesis of Janus gold nanoparticles (AuNPs) based on interface‐directed self‐assembly is reported. Polystyrene (PS) colloidal particles with AuNPs on the surface were prepared by interface‐directed self‐assembly, and the colloidal particles were used as templates for the synthesis of Janus AuNPs. To prepare colloidal particles, thiol‐terminated polystyrene (PS‐SH) was dissolved in toluene and citrate‐stabilized AuNPs were dispersed in aqueous solution. Upon mixing the two solutions, PS‐SH chains were grafted to the surface of AuNPs and amphiphilic AuNPs were formed at the liquid–liquid interface. PS colloidal particles decorated with AuNPs on the surfaces were prepared by adding the emulsion to excess methanol. On the surface, AuNPs were partially embedded in the colloidal particles. The outer regions of the AuNPs were exposed to the solution and were functionalized through the grafting of atom‐transfer radical polymerization (ATRP) initiator. Poly[2‐(dimethamino)ethyl methacrylate] (PDMAEMA) on AuNPs were prepared by surface‐initiated ATRP. After centrifugation and dissolving the colloidal particles in tetrahydrofuran (THF), Janus AuNPs with PS and PDMAEMA on two hemispheres were obtained. In acidic pH, Janus AuNPs are amphiphilic and are able to emulsify oil droplets in water; in basic pH, the Janus AuNPs are hydrophobic. In mixtures of THF/methanol at a volume ratio of 1:5, the Janus AuNPs self‐assemble into bilayer structures with collapsed PS in the interiors and solvated PDMAEMA at the exteriors of the structures.     

Self-assembly of ionic liquid (BMI-PF6)-stabilized gold nanoparticles on a silicon surface: chemical and structural aspects

Ultrafine monodisperse gold nanoparticles (AuNPs) were synthesized by an elegant sputtering of gold onto 1- n-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF(6)) ionic liquid. It was found that the BMI-PF(6) supramolecular aggregates were loosely coordinated to the gold nanoparticles and were replaceable with thiol molecules. The self-assembly of BMI-PF(6)-stabilized AuNPs onto a (3-mercaptopropyl)trimethoxysilane (MPS)-functionalized silicon surface in 2D arrays, followed by dodecanethiol (DDT) treatment, have been demonstrated using X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and contact angle measurements. DDT treatment of tethered AuNPs revealed two types of interactions between AuNPs and the MPS-functionalized surface: (a) AuNPs anchor through Au-S chemisorption linkage resulting in strong immobilization and (b) some of the AuNPs are supported by physisorption, driven by BMI-PF(6). The attachment of these particles remains unchanged with sonication. The replacement of BMI-PF(6) aggregates from physisorbed AuNPs with DDT molecules advances the dilution of their interaction with the MPS-functionalized surface, and they subsequently detach from the silicon surface. The present finding is promising for the immobilization of ionic liquid-stabilized nanoparticles, which is very desirable for electronic and catalytic device fabrication. Additionally, these environmentally friendly AuNPs are expected to replace conventional citrate-stabilized AuNPs.     

金纳米粒子的细胞毒性

金纳米粒子(AuNPs)是构建用于诊断和治疗的纳米药物/探针的理想纳米材料之一,因此研究AuNPs与细胞的相互作用具有重要意义。 本文详细分析了金纳米簇(AuNCs)、球形金纳米粒子A(AuNPss)、金纳米球壳(AuNSs)和金纳米棒(AuNRs)等不同形貌的Au NPs对不同细胞模型的细胞毒性;讨论了AuNPs的理化性质(大小、形状、化学功能和表面电荷)对其细胞毒性的影响。 总结了AuNP细胞毒性研究遇到的挑战并提出相应解决方法。     

溶胶-凝胶法原位复合PVA/HA水凝胶的结构表征与性能研究

采用溶胶-凝胶原位复合的方法制备了聚乙烯醇/羟基磷灰石生物活性复合水凝胶,探讨了HA含量对复合水凝胶结构性能的影响,用X射线衍射分析、红外光谱分析、DSC、扫描电镜等方法对HA在PVA水凝胶体系中的晶态结构及分散状态进行了表征,并与物理共混复合法进行了比较.研究发现,采用溶胶-凝胶法原位复合可在PVA水凝胶中形成具有生物活性的HA结晶结构,且分散良好,分布均匀.HA粉体作为异相成核剂,促进了PVA水凝胶基体的结晶,提高了复合水凝胶的力学性能.     

Small Size Effect and Concentration Response of Gold Nanoparticles in Electrochemiluminescence Reaction

Recent reports have used gold nanoparticles (AuNPs) as a co‐reactant for the electrochemiluminescence (ECL) reaction of ruthenium complex. However, understanding the size effect of AuNPs on ECL reaction is very meaningful to explore its unknowns and develop its applications at the molecular level. In this paper, we examined the behavior of various small‐size AuNPs in ECL reaction, focusing on changes in ECL caused by AuNPs size and reasons for this change. Although the luminescence spectra and excitation potential have hardly changed in ECL reaction, the difference of ECL intensities induced by different sizes AuNPs is very obviously. Our experimental results revealed disparate behaviors depending on AuNPs size: the small‐sized AuNPs can lead to stronger ECL, and ECL intensities increase as the addition of AuNPs concentration in the wider range. This small size effect is related to an intermediate process of charge‐discharge in electric double layer formed by adsorbing ruthenium complex with AuNPs, and the surface and quantum size effect of AuNPs may affect this intermediate process. More importantly, AuNPs can act as a marker, has the same small size effect and concentration response, and bring about a promising platform for biochemical analysis.     

金纳米粒子膜的电化学合成及SERS活性分析

Surface-enhanced Raman scattering(SERS)-active gold nanoparticles(AuNPs) films were prepared with a one-step electrochemical method. The orthogonal design was used to investigate the experimental conditions influencing the morphologies and the SERS activity of the AuNPs. A condition was found to obtain the optimal SERS activity. The SEM study reveals that the AuNPs films were composed of closely packed AuNPs. The Finite Difference Time Domain(FDTD) simulation result indicates that the coupling between particles plays an important role in the enhancement SERS of AuNPs.     

Vibrational spectroscopic characterization of 4-acylamidobenzenethiol-stabilized gold nanoparticles

A simple preparation method of gold nanoparticles (AuNPs) with 4-acylamidobenzenethiol derivative (BD) was improved to obtain the larger size of AuNPs which exhibited localized surface plasmon resonance. The spectroscopic characterizations of two kinds of BD-stabilized AuNPs were carried out by means of ATR-FTIR and Raman spectroscopy in order to clarify the conformation and orientation of BDs adsorbed on AuNPs. The relation between the stability of AuNPs and the adsorbed states of BDs were also discussed. The average sizes of the resulting AuNPs were 18 nm for BD1 and 30 nm for BD2, respectively. It was found that the BD1-capped AuNPs formed large aggregates. The results of vibrational spectroscopy revealed that loosely packed self-assembled monolayer (SAM) of BD1 molecules was formed on the surface of the AuNPs; on the other hand, densely packed SAM was formed in the case of BD2. We concluded the difference behavior between the two types of molecules was caused by the functional groups. The sulfuryl groups of BD2 induced highly ordered SAM and suppressed aggregate formation of AuNPs.     

Green synthesis of Au nanoparticles immobilized on halloysite nanotubes for surface-enhanced Raman scattering substrates

A facile and green route was introduced to synthesize Au nanoparticles immobilized on halloysite nanotubes (AuNPs/HNTs) used for surface-enhanced Raman scattering substrates. The naturally occurring HNTs were firstly functionalized with a large amount of -NH(2) groups by N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (AEAPTES), which possesses one lone electron pair and will "anchor" Au ions to form a chelate complex. Then, with the addition of tea polyphenols (TP), the Au ions were reduced on the surface of the previously formed Au-NH(2) chelate complex to form AuNPs. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) observations indicate that a large amount of AuNPs were synthesized on HNTs. The AuNPs are irregularly spherical and densely dispersed on HNTs and the diameter of the nanoparticles varies from 20 to 40 nm. The interactions between AuNPs and -NH(2) groups were verified by X-ray photoelectron spectroscopy (XPS) and the results showed that the functional groups can "anchor" AuNPs through the chelating effect. The as-prepared AuNPs/HNTs nanomaterials with several nanometers gaps among nanoparticles were used as a unique surface-enhanced Raman scattering substrate, which possessed strong and distinctive Raman signals for R6G, indicating the remarkable enhancement effect of the AuNPs/HNTs.     

Structural organization of gold nanoparticles onto the ITO surface and its optical properties as a function of ensemble size

Self-assembly of citrate-stabilized gold nanoparticles (AuNPs) onto an optically transparent indium tin oxide (ITO) surface followed by neutralization of these particles using dodecanethiol as a surfactant have been demonstrated. X-ray photoelectron spectroscopic (XPS) studies revealed the partial removal of citrate ions from the immobilized AuNPs, which advances the dilution of electrostatic attraction between AuNPs and the APS (amino-terminated monolayer)-functionalized ITO surface. The resultant AuNPs restore their mobility to some extent and form small ensembles. Some of the immobilized AuNPs were completely removed from the surface due to neutralization, as confirmed by XPS studies. Interparticle distance and size of ensembles were manipulated by consecutive cycles of immobilization and neutralization of AuNPs. Controlled nanostructural fabrication progression, which leads to two-dimensional lateral growth of AuNPs, provides a method for systematically shifting the surface plasmon resonance band based on the increase in plasmon coupling among the closely placed AuNPs of an ensemble. The magnitude of shift increases with the size of ensemble. This manipulated chemical strategy offers a convenient and simple method to tune the optical properties of materials on a nanoscale.     

Self-assembly and encoding of polymer-stabilized gold nanoparticles with surface-enhanced Raman reporter molecules

Polymer-stabilized gold nanoparticles (AuNPs) were prepared and encoded with a range of surface-enhanced Raman reporter molecules. A range of as-synthesized polymers produced by reversible addition fragmentation chain transfer (RAFT) polymerization were demonstrated to self-assemble at the surface of AuNPs dispersed in water. The method involved the coprecipitation of polymer-gold conjugates by the addition of polymer dissolved in a water-miscible solvent to gold AuNPs dispersed in water. This method represents a simplification of the preparation of polymer-stabilized AuNPs compared with other published methods, in that the AuNPs do not need to be first transferred to an organic solvent. The process enabled the polymer stabilized AuNPs to be easily recovered by filtration or by phase transfer of the AuNPs to an organic solvent in which the RAFT polymer was soluble. The polymer-stabilized AuNPs were characterized by a range of methods including UV-visible spectrophotometry, transmission electron microscopy, thermogravimetric analysis, dynamic light scattering, and attenuated total reflection Fourier transform infrared spectroscopy. Furthermore, 1H pulsed field gradient spin echo NMR was utilized to characterize the self-diffusion of the polymer-stabilized AuNPs. Finally, we then demonstrated that these polymer-stabilized AuNPs maintained their ability to be encoded with surface-enhanced Raman spectroscopy reporter molecules.     

用金纳米粒子修饰硅纳米线及复合结构的光谱性质研究

在溶液中以正己硫醇作稳定剂, 利用HAuCl4与HF处理后的硅纳米线(SiNWs)的氧化还原反应, 在SiNWs表面负载金纳米粒子(AuNPs). 通过调整HAuCl4的浓度, 得到了AuNPs粒径从3.2到7.0 nm的AuNPs/SiNWs复合结构, 并对这种复合结构进行了紫外-可见吸收光谱和荧光光谱研究. 紫外-可见吸收光谱研究表明, 负载不同粒径的AuNPs的SiNWs在530～580 nm间有明显的由AuNPs表面等离子体共振引起的吸收, 且随着AuNPs粒径的增加, 该吸收峰发生红移. 负载前后的荧光光谱表明, 在红光和绿光区负载AuNPs的SiNWs的荧光峰与HF处理后SiNWs的荧光峰峰形相当, 峰位变化不大; 但在蓝光区, 不同于HF处理前后SiNWs的发射峰(464 nm左右), 负载了AuNPs的SiNWs在423 nm的位置处出现了强荧光峰, 这个峰是AuNPs费米能级的电子与sp或d带的空穴辐射复合产生的.     

Electrocatalytic activity of supported gold nanoparticles toward CO oxidation: The perimeter effect of gold–support interface

The gold nanoparticles (AuNPs) sputtered on indium tin oxide (ITO) were used to investigate the origin of the high catalytic activity of AuNPs toward electrooxidation of CO in alkali media. We demonstrated that the catalytic activity is closely related to the gold–ITO perimeter, which represents only a very small percentage of the total surface area of AuNPs. Increasing the perimeter-to-surface ratio of the ITO-supported AuNPs leads to an increase of catalytic activity. This work provides a potential strategy to further promote the catalytic activity of AuNPs in the electrochemical system.     

Gold-nanosphere formation using food sample endogenous polyphenols for in-vitro assessment of antioxidant capacity

In this work it was demonstrated that sample endogenous polyphenols are selectively driving the gold-nanoparticle (AuNPs)-formation process when representative food samples were used as natural sources of reducing compounds. The process of AuNPs formation was characterized by UV-visible spectroscopy and was described by a sigmoidal curve (R (2)?≥?0.990) which gave information about the polyphenol concentration at which the localized surface plasmon resonance (LSPR) absorption reached its half-value, X (c) (50) , and about AuNPs production per polyphenol concentration unit, K (AuNPs). The behavior of phenolic acids was different, with lower X (c) (50) and higher K (AuNPs) values than flavonoids. For the food samples tea, apple, pear, wine, and honey X (c) (50) values were 0.22, 7.3, 11.5, 20.4, 30.3, and 53.5 (mg mL(-1)) and K (AuNPs) values were 28.7, 0.70, 0.60, 0.20, 0.14, and 0.10 (mg(-1) mL), respectively. Excellent correlation between K (AuNPs) and total phenolics (TP) was obtained (r?=?0.98, p-value? apple > pear > wine > honey. The reproducibility of the AuNPs formation approach was excellent, not only for polyphenol standards (RSD?相似文献   

CHCA-modified Au nanoparticles for laser desorption ionization mass spectrometric analysis of peptides

Gold nanoparticles (AuNPs) have been studied as a potential solid-state matrix for laser desorption/ionization mass spectrometry (LDI-MS) but the efficiency in ionization remains low. In this report, AuNPs are capped by a self-assembled monolayer of cysteamine and modified with α-cyano-4-hydroxycinnanic acid (CHCA) for effective MALDI measurements. CHCA-terminated AuNPs offer marked improvement on peptide ionization compared with citrate-capped or cysteamine-capped AuNPs. The coating also effectively suppresses formation of Au cluster ions and analyte fragment ions, leading to cleaner mass spectra. Addition of glycerol and citric acid to the peptide/AuNPs sample further improves the performance of these AuNPs for LDI-MS analysis. Glycerol appears to enhance the dispersion of AuNPs in sample spots, increasing the sample ionization and shot-to-shot reproducibility, while citric acid serves as an external proton donor, providing high production of protonated analyte ions and reducing fragmentation of peptides on the nanoparticle-based surface. Optimal ratios of citric acid, glycerol, and AuNPs in sample solution have been systematically studied. A more than 10-fold increase for desorption ionization of peptides can be achieved by combining 5% glycerol and 20 mM citric acid with the CHCA-terminated AuNPs. The applicability of the CHCA-AuNPs for LDI-MS analysis of protein digests has also been demonstrated. This work shows the potential of AuNPs for SALDI-MS analysis, and the improvement with chemical functionalization, controlled dispersion, and use of an effective proton donor.     

AuNPs/PNIPAM复合颗粒的制备及其温敏性质

将金纳米颗粒(AuNPs)组装到聚N-异丙基丙烯酰胺(PNIPAM)水凝胶微球表面制备出AuNPs/PNIPAM复合颗粒. 将PNIPAM 凝胶的温敏特性与AuNPs的光学性质结合, 通过改变温度调节AuNPs的局部表面等离子共振(LSPR)吸收峰位置. 研究结果表明, 温度升高使AuNPs的LSPR吸收峰发生红移, 并且这种效应是可逆的. 同时发现, AuNPs的光学性质还可以作为表征PNIPAM水凝胶微球温敏行为的一种手段. 利用透射电镜、紫外-可见光谱仪及动态光散射仪对AuNPs/PNIPAM复合颗粒的形貌、光学性质、粒径变化等进行了分析.     

基于DNA电化学发光传感器研究金纳米颗粒对量子点的电化学发光影响

纳米金颗粒具有高的消光系数和良好的表面等离子体共振特性, 其等离子体共振特性受纳米金颗粒的尺寸和周围环境等因素的影响. 本文基于半导体纳米晶电化学发光信号对金纳米颗粒的距离依赖性制备了DNA电化学发光传感器. 首先利用循环伏安法(CV)在玻碳电极(GCE)表面原位沉积金纳米颗粒(AuNPs), 巯基丙酸包裹的CdS量子点(QDs)与氨基修饰的双链DNA (dsDNA)通过酰胺键缩合, 形成量子点修饰的双链DNA(QDs-dsDNA). 最后将QDs-dsDNA 通过dsDNA 另一端的巯基组装到纳米金表面, 得到CdS QDs-DNA/AuNPs/GCE电化学发光传感器. 在优化电极表面QDs-dsDNA密度、金纳米颗粒沉积方法等实验条件的基础上, 对不同传感器的表面性质进行了表征, 如形貌和电化学阻抗等. 进一步通过控制纳米金和CdS QDs之间的DNA研究了纳米金对CdS QDs发光信号的影响作用. 结果显示DNA链的长度和类型对发光信号有着重要的影响. 最后将此传感器用于环境污染物的DNA损伤检测, 显示出很好的灵敏响应.     

Electrochemical Characterization and Electrocatalytic Application of Gold Nanoparticles Synthesized with Different Stabilizing Agents

Gold nanoparticles (AuNPs) have unique properties, making them attractive for electronic and energy‐conversion devices and as (electro)catalysts for electrochemical sensors. In addition to the size and shape of AuNPs, the electrocatalytic properties of AuNP‐sensors are also determined by the stabilizing agent used in their synthesis. Here, AuNPs were synthesized with citrate, alginate and quercetin, obtaining spherical and negatively charged nanoparticles. The AuNPs were used to modify glassy carbon electrodes (AuNPs/GCE), which were characterized by scanning electron microscopy and electrochemical techniques. The AuNPs/GCE showed aggregates of different sizes and degrees of dispersion on the electrode surface depending on the stabilizing agent. The AuNP's aggregates affect the homogeneity of the film, the reproducibility of the electrodes and their response in buffer solution. Finally, to evaluate the electrocatalytic ability of the AuNPs/GCE, we studied the oxidation of two analytes with opposite charges: (1) sunset yellow (negative) and (2) hydrazine (positive). Compared with GCE, the AuNPs/GCE showed good electrocatalytic properties for hydrazine, increasing the current up to 50 % and shifting the potential by almost 400 mV, depending on the AuNP used. For the negatively charged analyte, the current decreased up to 50 % and no shift in potential was observed. Thus, the electrocatalytic properties of the AuNPs showed to be highly dependent on the nature of the analyte.     

Analysis of Dynamic and Thermodynamic Adsorption of Nanoparticles on Solid Surfaces by Dark‐Field Light Scattering Measurements

We have constructed a dark‐field light scattering microscope using a very low‐cost digital camera to investigate the adsorption of gold nanoparticles (AuNPs) on four different substrates at various pH values. The substrates used are glass, polycarbonate (PC), poly(dimethylsiloxane) (PDMS), and poly(methyl methacrylate) (PMMA). The coverage of AuNPs on hydrophobic substrates such as PDMS is greater than that on hydrophilic substrates like glass. The adsorption and aggregation of AuNPs on a particular substrate increased upon decreasing the pH (from 9.0 to 4.0). A greater coverage percentage of AuNPs, but less aggregation, occurs on glass treated with poly(diallyldimethylammonium) (PDDA) than on bare glass. The scattering intensity increases upon increasing the number of layers of adsorbed AuNPs on glass that was treated sequentially with AuNPs and PDDA. When compared to UV‐Vis absorption, dark‐field microscope provides greater sensitivity and qualitative surface information.     

Iron(III)‐Quantity‐Dependent Aggregation–Dispersion Conversion of Functionalized Gold Nanoparticles

Developing gold nanoparticles (AuNPs) with well‐designed functionality is highly desirable for boosting the performance and versatility of inorganic–organic hybrid materials. In an attempt to achieve ion recognition with specific signal expressions, we present here 4‐piperazinyl‐1,8‐naphthalimide‐functionalized AuNPs for the realization of quantitative recognition of Fe^III ions with dual (colorimetric and fluorescent) output. The research takes advantage of 1) quantity‐controlled chelation‐mode transformation of the piperazinyl moiety on the AuNPs towards Fe^III, thereby resulting in an aggregation–dispersion conversion of the AuNPs in solution, and 2) photoinduced electron transfer of a naphthaimide fluorophore on the AuNPs, thus leading to reversible absorption and emission changes. The functional AuNPs are also responsive to pH variations. This strategy for realizing the aggregation–dispersion conversion of AuNPs with returnable signal output might exhibit application potential for advanced nanoscale chemosensors.