Monitoring the Synthesis of Au Nanoparticles Using SEC

In this paper, it is demonstrated that size-exclusion chromatography (SEC) with SDS (10 mM) as the mobile phase can be used to rapidly determine the sizes of Au nanoparticles (NPs). It was found that standard particles at sizes ranging from 12.1 to 79.1 nm eluted in a linear manner with respect to the elution time. The reproducibility of the separation over the entire range of the calibration curve was high; the relative standard deviations of the elution times were less than 0.3%. Next, the separation conditions to characterize the sizes of Au NPs prepared through seed-assisted synthesis were employed. Using this approach, it was found that the rate of addition of the reducing agent influenced the sizes of the final products; for example, rapid addition of the reducing agent resulted in polydisperse Au NP products. SEC analysis revealed that the presence of NaOH in the synthesis medium decreased the sizes of the Au NPs dramatically. When using SEC to analyze Au NPs produced through seed-assisted synthesis, a good correlation existed between the sizes obtained using SEC and those provided by transmission electron microscopy (TEM). Based on these findings, SEC appears to be an efficient and accurate tool for characterizing the sizes of NPs fabricated through seed-assisted synthesis.     

Structural Characterization of Zirconia Nanoparticles Prepared by Microwave-Hydrothermal Synthesis

Nanocrystalline zirconia powders have been prepared by microwave-hydrothermal synthesis starting from aqueous solution of ZrOCl₂·8H₂O. Results of investigations on the aqueous suspension stability of the washed zirconia nanopowders by dynamic light scattering showed that the suspension, constituted by superaggregates of nanoparticles (131 ± 10 nm), was stable up to 15 days. Nanopowders were investigated by means of transmission electron microscopy and small angle x-ray scattering measurements which proved that the zirconia nanopowder is constituted by small primary nanoparticles of ca. 8 nm that agglomerate forming bigger aggregates of 50 ± 1 nm.     

微波法制备3.5 G PAMAM树状大分子保护的金纳米粒子

以3.5 G PAMAM(3.5代聚酰胺-胺型)树状大分子为保护剂,利用微波法还原HAuCl₄溶液制备金纳米粒子.考察了当3.5 G PAMAM与HAuCl₄物质的量的比一定时,微波照射不同时间对金纳米粒子大小及形状的影响;以及同一照射条件下,3.5 G PAMAM与HAuCl₄不同的物质的量比值对金纳米粒子大小及形状的影响.利用紫外可见分光光度计、透射电子显微镜对其进行了表征.结果表明,当3.5 G PAMAM与HAuCl₄物质的量的比值一定时,金纳米粒子的形状和大小受微波照射时间长短的影响不大;适当延长照射时间,制得的金纳米粒子的分散性较好.在相同照射条件下,随着3.5 G PAMAM与HAu-Cl₄物质的量比值的减小,得到的金纳米粒子粒径逐渐变大,且分散性变差.     

Monitoring Stability and Sizes of Au/Pd Core/Shell Nanoparticles by SEC

This paper describes how size exclusion chromatography (SEC) can be used to rapidly characterize Au/Pd core/shell nanoparticles (NPs). We monitored the sizes of Au/Pd core/shell NPs by effecting SEC separation using a mobile phase of 10 mM sodium dodecyl sulfate (SDS); the plot of retention time with respect to the standard size of the Au NPs was linear (R ² = 0.991) for diameters falling in the range from 12.1 to 59.9 nm; for five consecutive runs, the relative standard deviations of these retention times were less than 0.4%. Under the optimized separation conditions, we found that the addition of the surfactant SDS stabilized the Au/Pd core/shell NP samples. In addition, SEC analysis revealed that the sizes of the Au/Pd core/shell NPs could be controlled via modification of the rate of addition of the reducing agent and the use of adequate volumes of the seed and shell precursor metal ion solutions. When using these conditions to analyze the Au/Pd core/shell NPs produced through seed-assisted synthesis, a good correlation existed between the sizes determined through SEC and transmission electron microscopy. Our results suggest that SEC is a useful technique for monitoring the sizes of NPs and nanomaterials in general.     

Using SEC for Analyzing the Sizes of Au/Pt Core/Shell Nanoparticles

This paper describes the use of size-exclusion chromatography (SEC) to characterize the sizes of fabricated Au/Pt core/shell nanoparticles (NPs), which were monitored using a polymer-based SEC column (pore size: ca. 400 nm) and a mobile phase of 10 mM sodium dodecyl sulfate (SDS). The plot of the retention time with respect to the logarithm of the size of the Au NPs was very linear (R ² = 0.999) for NP diameters falling in the range from 5.3 to 59.9 nm. The relative standard deviation (n = 5) of these retention times was less than 0.20%. When using SEC to analyze synthetic products, we found that the sizes of the fabricated Au/Pt core/shell NPs could be controlled via modification of the volumes of the seed, SDS, and sodium hydroxide solutions. A good correlation existed between the sizes determined through SEC and those determined using transmission electron microscopy. Thus, polymer-based SEC appears to be a useful technique for monitoring the sizes of NPs—and nanomaterials in general.     

Synthesis and Characterization of Silver Nanoparticles Prepared with Honey: The Role of Carbohydrates

Silver nanoparticles were synthesized using honey at pH 5.0 and 10.0 using a rapid, low cost, and simple technique. The influence of the honey carbohydrates (glucose and fructose) in the synthesis was characterized. Moreover, the kinetic variables in the synthesis at room temperature and at pH 5.0 and 10.0 were analyzed by measuring surface plasmon resonance at 411?nm by absorption spectroscopy. Transmission electron microscopy, thermal gravimetric analysis, and differential thermal analysis were used to characterize the metal nanoparticles and the capping agents. The synthesized nanoparticles were obtained for the first time at pH 5.0. This fact allows evaluating the kinetics and reaction mechanism. The obtained nanoparticles were spherical, monodispersed, and smaller than 20?nm. The results show that glucose serves as a reducing and capping agent while fructose has a limited reducing effect.     

Characterization of Au Nanoparticle Film Electrodes Prepared on Polystyrene

Au nanoparticle films prepared on a polystyrene substrate were studied as a new electrode material. The films were formed from Au particles with different sizes (2–50 nm) and binder molecules (methanethiol, butanethiol, pentanethiol, hexanethiol and heptanethiol) on the substrate with a straightforward procedure. The electrode allows one to monitor reactions occurring only on the nanoparticles, and the catalytic currents resulting from small molecules such as hydrogen peroxide and organic amines were successfully detected in such a manner.     

Synthesis and Characterization of Lead Sulfide Nanoparticles in Zirconia-Silica-Urethane Thin Films Prepared by the Sol-Gel Process

PbS nanocrystals (NCs) ranging between 4–8 nm were incorporated into Zirconium-Silica-Urethane (ZSUR) matrix obtained by the sol-gel method. The sizes of the particles were controlled by temperature treatment and by concentration of PbS in ZSUR matrix. The sizes of PbS NCs were determined by TEM measurements. The quantum size effect could also be extracted from optical absorption and photoluminescence spectra. The new matrix allows incorporation of up to 40% PbS forming a characteristic structure of dendrite by reacting lead acetate with ammonium thiocyanate in sol-gel matrix. The sol precursors of the matrix for Zirconium-Silica-Urethane contained zirconium oxide (ZrO₂) matrix solution, tetramethoxysilane (TMOS), 3-glycid oxypropyl trimethoxysilane (GLYMO) and polyethylene urethane silane (PEUS) synthesized separately. The ZrO₂ matrix solution was obtained from zirconium n-tetrapropoxide in propanol and acetic acid was used as a chelating agent to stabilize the zirconium oxide precursor.     

溶剂萃取法制备的纳米CeF3紫外吸收性能研究

利用Cyanex 923萃取法制备了纳米级CeF3微粉,并研究了分散剂、 CeF3量、 CeF3预处理灼烧温度和微粉粒径分布等因素对CeF3紫外吸收行为的影响. 结果表明,CeF3在255 nm附近有特征吸收峰;分散剂的极性强弱、 分散物浓度的改变都会影响吸收峰的强弱;随着粒径的减小,紫外吸收峰发生明显的红移. 此外还研究了TiO2包覆CeF3的紫外吸收性质,复合材料在250～400 nm区间内同时出现了TiO2和CeF3的特征吸收峰,复合材料的吸光域范围扩展.     

Novel Green Synthesis and Characterization of the Antioxidant Activity of Silver Nanoparticles Prepared from Nepeta leucophylla Root Extract

Bioinspired silver nanoparticles were synthesized using nontoxic, eco-friendly, and novel root extract of Nepeta leucophylla. The reduction of silver nitrate salt into nanoparticles is performed using the root extract, which is rich in polyphenolic and flavonoid contents. The reduction of silver salt by this extract is occurred at several temperatures and the reaction mixture turns brown and displayed representative absorbance spectra of silver nanoparticles. The influence of numerous synthesis parameters such as the concentration of root extract, time, temperature, and reaction pH on the synthesis of silver nanoparticles was also examined. Furthermore, the synthesized silver nanoparticles were characterized by ultraviolet–visible spectroscopy, Fourier transformed infrared spectroscopy, X-ray diffraction, and transmission electron and field emission scanning electron microscopy. The formation of silver nanoparticles was enhanced with time, temperature, and at basic pH. The surface plasmon resonance band characteristics of silver nanoparticles were detected at 410?nm in the ultraviolet–visible absorbance spectra. The infrared spectroscopy results show that the extract contains phenol which is responsible for reduction and proteins may be capping the silver nanoparticles which prevent agglomeration. Transmission electron microscopy revealed that silver nanoparticles were spherical and the sizes matched well with X-ray diffraction and theoretical calculations by Mie theory. Furthermore, the antioxidant potential of the synthesized silver nanoparticles was assessed using 2,2-diphenyl-1-picrylhydrazyl assay and showed considerable antioxidant potential.     

银纳米粒子的一步合成与表征

在水和乙醇溶液中,以对巯基苯胺作为还原剂,利用一步法合成了银纳米微粒,并利用拉曼光谱仪考察了对巯基苯胺在银纳米微粒表面的自组装行为.结果表明,合成的银纳米微粒的形貌与介质的pH值密切相关;对巯基苯胺可在银纳米微粒表面自组装.     

Synthesis and Characterization of Bimetallic Copper-Gold Nanoparticles

We have synthesized copper-gold, core-shell nanoparticles by the microemulsion method. The particles were prepared in two steps, by first reducing copper ions and then gold ions in the aqueous domains of anionic microemulsions. Two surfactants have been used as emulsifiers, AOT and Cu(AOT)₂. The latter is the source of copper ions. Gold ions come from aqueous solutions of HAuCl₄. Ultraviolet-visible spectroscopy experiments show that copper nanoparticles are created in the first step of the synthesis, and that a gold layer covers them in the second step. Transmission electron microscopy and related techniques confirm the formation of copper (core)-gold (shell) nanocrystals.     

表面修饰LaF_3纳米微粒的制备及表征

在水醇混合介质中采用同阳离子共沉淀表面修饰法制备了有机化合物表面修饰的LaF3纳米微粒 ,研究了它的摩擦学特性。采用多种分析手段表征了表面修饰LaF3纳米微粒的结构 ,并在四球摩擦试验机上考察其润滑性能。结果表明 ,表面修饰LaF3纳米微粒不仅在有机溶剂中具有良好的分散性 ,同时也显示出良好的减摩、抗磨和承载性能。     

Synthesis and Characterization of Carbon-Stabilized Magnesium Nanoparticles

Magnesium nanopowder has attracted many interests in the recent years, which has a very difficult and costly synthesis process because of its high activity. In this work, magnesium nanoparticles stabilized with amorphous carbon (Mg–C nanoparticles) were synthesized by submerged arc discharge technique in kerosene. The arc discharge was generated between two electrodes of magnesium at the arc current of 1 A and arc voltage of 50 V. Mg–C nanoparticles were characterized by various techniques. Dynamic light scattering result indicated that size of magnesium nanoparticles is about 35 nm. X-ray diffraction showed that the produced sample consisted of hexagonal magnesium and amorphous carbon and there was no presence of magnesium oxides in the pattern. Field emission scanning electron microscopy and transmission electron microscopy results illustrated that the sample has morphology of agglomerated nanospheres. Energy dispersive X-ray spectroscopy demonstrated formation of 57 percent magnesium and 43 percent carbon. Differential scanning calorimetry analysis showed that the amorphous carbon increased ignition temperature of nanoparticles by 180 °C compared to pure magnesium micron-sized powder. Therefore, Mg–C nanoparticles can have many applications in different fields similar to magnesium nanopowders. However, by producing Mg–C nanoparticles, there is no need for vacuum chamber or inert gases during production and after that, since amorphous carbon protects magnesium nanoparticles from oxidation.     

金纳米颗粒的水相法合成及荧光性能

在水溶液中,以PAMAM树形分子为模板,乙醇为还原剂,制备了树形分子包裹的金纳米颗粒,其水溶性好,可以稳定放置1年以上;通过控制Au3+与PAMAM树形分子的摩尔比,可以得到粒径可控的金纳米颗粒,其粒径范围为1～4nm,分别在385和402nm处出现强的共振瑞利光散射峰和荧光峰.室温下,荧光量子产率达到10%以上,比其它文献报道的金纳米颗粒的荧光量子产率高2个数量级以上,这一特性使其在潜指纹识别、光催化等方面具有很大的应用潜力.     

Synthesis and Properties of ZrO2 Films Dispersed With Au Nanoparticles

Au nanoparticles dispersed ZrO₂ thin films were prepared from two precursors HAuCl₄·4H₂O and ZrOCl₂·8H₂O in air. The structural properties and size of Au particle in ZrO₂ film were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface analysis with atomic force microscopy (AFM) showed the effect of monoethanolamine on preventing the migration of Au particles to the surface. The absorption peak of Au particles by the surface plasma resonance was observed and the red shift of absorption peak was discussed.     

TiO2纳米管负载Ag、Au、Pt纳米粒子的微波合成与表征(英)

TiO₂ nanotubes were prepared under normal pressure at a temperature of 120 ℃. Ag, Au, Pt nanoparticles supported on TiO₂ nanotubes were prepared by microwave assisted heating polyol process. TEM images showed that microwave prepared Ag, Au, Pt nanoparticles supported on TiO₂ nanotubes were small and well dispersed on the surface of the TiO₂ nanotubes. UV-Vis absorption spectra showed that the absorbance of Ag/TiO₂ nanotubes and Au/TiO₂ nanotubes in the visible light range increased greatly compared to the single titania nanotubes.     

Localized Deposition of Au Nanoparticles by Direct Electron Transfer through Cellobiose Dehydrogenase

Cellobiose dehydrogenase (CDH) is a fascinating extracellular fungal enzyme that consists of two domains, one carrying a flavin adenine dinucleotide (FAD) and the other a cytochrome‐type heme b group as cofactors. The two domains are interconnected by a linker and electrons can shuttle from the FAD to the heme group by intramolecular electron transfer. Electron transfer between CDH and an electrode can occur by direct electron transfer (DET) and by mediated electron transfer (MET). This characteristic makes CDH an interesting candidate for integration in systems such as biosensors and biofuel cells. Moreover, it makes CDH an alternative for the reduction of metal ions through DET and MET. In this work we have explored the localized deposition of gold on Pd substrates by CDH through DET and MET. For this purpose we exploited the advantage of scanning electrochemical microscopy (SECM) as a patterning tool. We first demonstrated that gold nanoparticles can be formed in homogenous solution. Then we showed that Au nanoparticles can also be locally formed and deposited on surfaces through DET at low pH and by MET at neutral pH using benzoquinone/hydroquinone as mediator.