Deposit of UV- or γ-synthesized gold nanoparticles on TiO2 powder using lipid-based multilamellar vesicles

This article describes a general method for the deposition of gold nanoparticles onto solid support based on the use of multilamellar vesicles (MLVs). Gold nanoparticles (nps) synthesized within lipid-based MLVs by UV- or γ-irradiation were deposited onto TiO₂ powder support. The organic phase from MLVs was removed by calcination leading to high dispersion of naked Au nanoparticles. The resulting particles were investigated using spectrometry, electron microscopy and XPS. The gold nanoparticles were stable and well-separated on the titania surface. It was found that the metal nanoparticles produced by radiolysis have smaller average size and narrower size distribution than those synthesized by photochemical route. After calcinations, the particles tended to enlarge to reach c.a. 18 nm. The gold loading on the titania support could be controlled by changing the gold salt concentration and the MLV-to-TiO₂ weight ratio; values of Au-to-Ti ratio up to 44 % could be obtained.     

Thioether moiety functionalization of mesoporous silica films for the encapsulation of highly dispersed gold nanoparticles

Highly dispersed gold nanoparticles within mesoporous thin films (MTFs) have been synthesized through a newly developed controllable strategy, in which (1,4)-bis(triethoxysilyl)propane tetrasufide (BPTS) organosiloxane coupling agent was co-assembled with tetraethyl orthosilicate (TEOS) to form organic groups functionalized mesoporous composite films followed with oxidization, ion-exchange with Au(en)₂Cl₃ (en: 1,2-ethanediamine) compound and calcination under hydrogen/nitrogen mixing atmosphere. Small-angle X-ray diffraction (XRD) characterization indicated that up to 10 mol% of BPTS could be incorporated into mesoporous hybrid films, and that would not breakup the structural integrity and long-range periodicity. The loaded gold nanoparticles were uniformly distributed due to the molecular level homogenous mixing of the BPTS precursor with TEOS, and its concentration could be controlled via the original ratio of BPTS to TEOS. The nanoparticles had a narrow size distribution with diameters in the size range of 3-7 nm through transmission electron microscopy (TEM) observation and underwent a slight size increase with the higher gold load level. An overall increase in the absorption intensity, a red shift of absorption peak, together with a comparatively narrower bandwidth could be observed at higher gold concentration within composite films from UV-vis spectra. Wide-angle XRD, TEM, X-ray photoelectron spectroscopy (XPS) and UV-vis spectra characterizations all agreed on the fact that the gold loading level could be controlled by the amount of BPTS in the starting sol for preparing MTFs.     

Phase transfer of large gold nanoparticles to organic solvents with increased stability

In this paper, we describe a new procedure to phase transfer large gold nanoparticles (diameters > 45 nm) from aqueous solution to organic solvents. This is accomplished using a covalent amide coupling reaction that incorporates dicyclohexylamine (DCHA) headgroups on the surface of mercaptoacetic acid (MAA) functionalized gold nanoparticles. Gold nanoparticles are first synthesized in aqueous solution by the citrate-reduction method, and nanoparticle size is controlled by the molar ratio of the reducing agent (sodium citrate) and the gold precursor (KAuCl4). MAA is then adsorbed to the surface of the gold nanoparticles followed by an amide-coupling reaction to covalently attach DCHA to the surface-immobilized MAA. The bulky dicyclohexyl groups entropically stabilize gold nanoparticles in organic solvents. This procedure was used to reliably transfer gold nanoparticles with diameters between 45 and 100 nm from aqueous solution to organic solvents such as dimethyl sulfoxide and chloroform.     

Catalytic activity of supported Au nanoparticles deposited from block copolymer micelles

Quasi-ordered, highly dispersed, gold nanoclusters of tightly controlled particle size were synthesized by dip-coating substrates with gold precursors encapsulated by block-copolymer micelles. By this method, gold particles (4.8 +/- 1.3 nm) were deposited on ITO-coated glass and shown to be catalytically active for electro-oxidation of carbon monoxide. XPS confirmed the catalytically active particles were predominantly Au0; however, a large fraction existed as Au3+. Whereas bulk gold is inert, these results demonstrate that catalytically active Au nanoparticles can be derived from micelle encapsulation.     

Preparation and Characterization of Heparin‐Stabilized Gold Nanoparticles

A simple method for preparing gold nanoparticles in aqueous solution has been developed by using glycosaminoglycan‐heparin as reducing and stabilizing agent and HAuCl₄ as precursor. The obtained gold nanoparticles were characterized by UV‐vis spectroscopy, resonance light scattering spectroscopy (RLS), transmission electron microscopy (TEM) and electrophoresis technology. The influence of reactant concentration for the preparation of gold nanoparticles was investigated. The results indicated that the gold nanoparticles carried negative charges in the aqueous solution and the size and shape of the gold nanoparticles could be controlled by changing the concentration of the heparin. Moreover, the gold nanoparticles obtained with relatively high concentration of heparin were very stable and had relative narrow size distribution.     

Synthesis of Silver and Gold Nanoparticles by a Novel Electrochemical Method

Spherical silver and gold nanoparticles with narrow size distributions were conveniently synthesized in aqueous solution by a novel electrochemical method. The technological keys to the electrochemical synthesis of monodispersed metallic nanoparticles lie in the choice of an ideal stabilizer for the metallic nanoclusters and the use of a rotating platinum cathode. Poly(N‐vinylpyrrolidone) (PVP) was chosen as the stabilizer for the silver and gold clusters. PVP not only protects metallic particles from agglomeration, but also promotes metal nucleation, which tends to produce small metal particles. Using a rotating platinum cathode effectively solves the technological difficulty of rapidly transferring the (electrochemically synthesized) metallic nanoparticles from the cathode vicinity to the bulk solution, avoiding the occurrence of flocculates in the vicinity of the cathode, and ensuring the monodispersity of the particles. The particle size and particle size distribution of the silver and gold nanoparticles were improved by adding sodium dodecyl benzene sulfonate (SDBS) to the electrolyte. The electrochemically synthesized nanoparticles were characterized by TEM and UV/Vis spectroscopy.     

金纳米粒子的微波法合成及在蛋白质检测中的应用

通过对微波反应器中氯金酸和柠檬酸钠混合物进行直接加热,快速、一步合成了金纳米粒子.通过调节反应初始混合物中氯金酸与柠檬酸钠的比例,可获得不同粒径窄分散的金纳米粒子.进一步将所合成的金纳米粒子功能化,考察了其在蛋白质检测中的应用.     

Biodistribution of colloidal gold nanoparticles after intravenous administration: effect of particle size

Purpose of the present research work was to evaluate the biological distribution of differently size gold nanoparticles (NP) up on intravenous administration in mice. Another objective was to study effect of particle size on biological distribution of gold NP to enable their diverse applications in nanotechnology. Gold NP of different particle sizes, mainly 15, 50, 100 and 200nm, were synthesized by modifying citrate ion concentration. Synthesized gold nanoparticles were characterized by SEM and their size distribution was studied by particle size analyzer. Gold NP was suspended in sodium alginate solution (0.5%, w/v) and administered to mice (1g/kg, intravenously) [n=3]. After 24h of administration of gold NP, blood was collected under light ether anesthesia, mice were sacrificed by cervical dislocation and various tissues/organs were removed. The tissues were then washed with saline, homogenized and lysed with aqua regia. The determination of gold in samples was carried out quantitatively by inductively coupled plasma mass spectrometry (ICP-MS). SEM study revealed spherical morphology of gold NP with narrow particle size distribution. Biodistribution study revealed gold NPs of all sizes were mainly accumulated in organs like liver, lung and spleen. The accumulation of gold NP in various tissues was found to be depending on particle size. 15nm gold NP revealed higher amount of gold and number of particles in all the tissues including blood, liver, lung, spleen, kidney, brain, heart, stomach. Interestingly, 15 and 50nm gold NP were able to pass blood-brain barrier as evident from gold concentration in brain. Two-hundred nanometers gold NP showed very minute presence in organs including blood, brain, stomach and pancreas. The results revealed that tissue distribution of gold nanoparticles is size-dependent with the smallest 15nm nanoparticles showing the most widespread organ distribution.     

Effect of size and shape controlled biogenic synthesis of gold nanoparticles and their mode of interactions against food borne bacterial pathogens

In this study, size and shape controlled biogenic synthesis of gold nanoparticles and their antibacterial activity against food borne bacterial pathogens were investigated. Synthesis of gold nanoparticles was carried out using two medicinally important plants Cucurbita pepo and Malva crispa and the size and shape of the nanoparticles were controlled by altering various parameters in the reaction medium. Results obtained from UV–Vis, FE-SEM, EDS and HR-TEM analyses supported the nanoparticles formation. FT-IR analysis confirmed the presence of biomolecules in the plant leaves extracts responsible for reducing and capping agents. Interestingly, the plant extract synthesized gold nanoparticles showed effective inhibition zone against Gram-positive and Gram-negative pathogens. The minimum inhibitory concentration (MIC) of synthesized gold nanoparticles at 400 μg/ml concentration showed effective inhibitory activity against Escherichia coli and Listeria monocytogenes. Conductivity of the medium continuously increased during the nanoparticles treatment with food borne bacterial pathogens resulting in indirect indication of the disruption of bacterial cell membranes. In addition, mode of interactions of gold nanoparticles against food borne bacterial pathogens was demonstrated using Bio-TEM analysis which is clear evident for the disruption of bacterial cell membranes.     

Linking the Gold Nanoparticles Formation Kinetics with Their Morphology

In this paper, we show that using different concentrations of reagents, it is possible to produce gold nanoparticles with different morphology (size, shape). The color of obtained colloidal gold change from pink, violet to blue, and it corresponds to the shape change. The pink color corresponds to spherical nanoparticles and the blue one to a star shape. The mixture of those two types of nanoparticles result in a violet tone. It was also shown that kinetics of nucleation and growth process is controlled by the reaction on the gold atoms surface, i.e., comproportionation of Au(III) and Au(0) to Au(I), which can be inhibited by varying precursor and reductant concentration.     

Size-controlled flow synthesis of gold nanoparticles using a segmented flow microfluidic platform

Segmented flow is often used in the synthesis of nanomaterials to achieve narrow particle size distribution. The narrowness of the distribution is commonly attributed to the reduced dispersion associated with segmented flows. On the basis of the analysis of flow fields and the resulting particle size distribution, we demonstrate that it is the slip velocity between the two fluids and internal mixing in the continuous-phase slugs that govern the nature of the particle size distribution. The reduction in the axial dispersion has less impact on particle growth and hence on the particle size distribution. Synthesis of gold nanoparticles from HAuCl(4) with rapid reduction by NaBH(4) serves as a model system. Rapid reduction yields gold nuclei, which grow by agglomeration, and it is controlled by the interaction of the nuclei with local flow. Thus, the difference in the physical properties of the two phases and the inlet flow rates ultimately control the particle growth. Hence, a careful choice of continuous and dispersed phases is necessary to control the nanoparticle size and size distribution.     

Stable polydiacetylene/ZnO nanocomposites with two-steps reversible and irreversible thermochromism: the influence of strong surface anchoring

The influence of pH value on gold nanoparticle production in the presence of Pluronic stabilizers is systematically investigated. The reactions are studied as a function of pH and at fixed concentrations of the two reactants, HAuCl(4) and P123 block copolymer. Results indicate that the reaction pathway during the nanoparticle formation can be controlled by varying pH. The nanoparticles synthesized at pH=11.12 have an average diameter of 9.6 nm with a narrow size distribution, and the Pluronics are adsorbed on individual gold particle surfaces to form core-shell structures via hydrophobic interactions. The present work provides an economic way to improve the dispersion and stabilization of gold nanoparticles and throws further light on the understanding of gold nanoparticle production using block copolymers.     

Solution-based direct readout surface enhanced Raman spectroscopic (SERS) detection of ultra-low levels of thiram with dogbone shaped gold nanoparticles

We report the use of two different sizes of dogbone shaped gold nanoparticles as colloidal substrates for surface enhanced Raman spectroscopy (SERS) based detection of ultra-low levels of thiram, a dithiocarbamate fungicide. We demonstrate the ability to use a solution based, direct readout SERS method as a quantitative tool for the detection of ultra-low levels of thiram. The two different sizes of dogbone shaped gold nanoparticles are synthesized by using the seed-mediated growth method and characterized by using UV-visible spectroscopy and transmission electron microscopy (TEM). The smaller dogbone shaped nanoparticles have an average size of 43 ± 13 nm. The larger dogbone shaped gold nanoparticles have an average size of 65 ± 15 nm. The nanoparticle concentration is 1.25 × 10(11) nanoparticles per mL for the smaller dogbone shaped gold nanoparticles and is 1.13 × 10(11) nanoparticles per mL for the larger dogbone shaped gold nanoparticles. Different concentrations of thiram are allowed to bind to the two different sizes of dogbone shaped gold nanoparticles and the SERS spectra are obtained. From the calibration curve, the limit of detection for thiram is 43.9 ± 6.2 nM when the smaller dogbone shaped gold nanoparticles are used as colloidal SERS substrates In the case of the larger dogbone shaped gold nanoparticles, the limit of detection for thiram is 11.8 ± 3.2 nM. The lower limit of detection obtained by using the larger dogbone shaped gold nanoparticles as colloidal substrates is due to the lightning rod effect, higher contributions from the electromagnetic enhancement effect, and larger number of surface sites for thiram to bind.     

Microwave-induced synthesis of highly dispersed gold nanoparticles within the pore channels of mesoporous silica

Highly dispersed gold nanoparticles have been incorporated into the pore channels of SBA-15 mesoporous silica through a newly developed strategy assisted by microwave radiation (MR). The sizes of gold are effectively controlled attributed to the rapid and homogeneous nucleation, simultaneous propagation and termination of gold precursor by MR. Diol moieties with high dielectric and dielectric loss constants, and hence a high microwave activation, were firstly introduced to the pore channels of SBA-15 by a simple addition reaction between amino group and glycidiol and subsequently served as the reduction centers for gold nanoparticles. Extraction of the entrapped gold from the nanocomposite resulted in milligram quantities of gold nanoparticles with low dispersity. The successful assembly process of diol groups and formation of gold nanoparticles were monitored and tracked by solid-state NMR and UV-vis measurements. Characterization by small angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the incorporation of gold nanoparticles would not breakup the structural integrity and long-range periodicity of SBA-15. The gold nanoparticles had a narrow size distribution with diameters in the size range of 5-10 nm through TEM observation. The average particles size is 7.9 nm via calculation by the Scherrer formula and TEM measurements. Nitrogen adsorption and desorption isotherms gave further evidence that the employed method was efficient and gold nanoparticles were successfully incorporated into the pore channels of SBA-15.     

Facile synthesis of concave decahedra enclosed by high-index facets and truncated decahedra with a large size

Nanostructures with concave surfaces are not common, and their synthesis is still challenging. In this paper, we have successfully synthesized two kinds of five-fold-twinned Au decahedra and dodecagonal plates by changing the reaction conditions. 40 high-index {221} facets were observed in the concave decahedron. The truncated decahedral gold nanocrystals (NCs) with a large size of 250-350 nm were obtained for the first time, which breaks the assumption that the truncated five-fold-twinned Au nanoparticles (NPs) can only be obtained with a size below 5 nm. The growth mechanism and the evolution process of the gold nanostructures were discussed. This work provides a facile way to synthesize concave decahedra, truncated decahedra and dodecagonal plates with controlled nanostructures.     

Synthesis of gold nanoparticles by microemulsion assisted photoreduction method

A new, clean, cost-effective and rapid method for the synthesis of stable spherical gold nanoparticles (AuNPs) is developed. This novel technique combines microemulsion as one of soft-nanotechnology techniques of wet chemistry, with photo-physics of UV-radiation in a unique versatile method to design and obtain controlled nanostructures for multifunctional materials. Based on a phase diagram in ternary water/Brij 30/n-heptane system pristine, and thiol functionalized, gold nanoparticles were obtained by a microemulsion assisted photoreduction technique, allowing increased flexibility during the synthesis and selection of materials. The spherical nanoparticles obtained by this route show a homogeneous size distribution, with an average diameter of 11 nm, for pristine gold nanoparticles and of 12 nm, for functionalized species. The evolution of the system at the nanoscale has been studied using, in tandem, UV-VIS and DLS measurements. The structure, size and shape of the final nanoparticles obtained have been evaluated by adequate instrumental techniques: FTIR, XRD and TEM image analysis. Kinetic studies have also been performed in order to follow the evolution of nanospecies during irradiation procedure.     

Synthesis and Characterization of Self-Assembling Some Thiol Surfactants on Gold Nanoparticles

The purpose of this work is to study the self-assembling of some synthesized thiol surfactants namely (mercaptopropane-, mercaptohexane-, mercaptooctane-, and mercaptodecane sodium sulfonate) on the fabricated gold nanoparticles. The self-assembling of these surfactants on gold nanoparticles characterized using different techniques such as FTIR spectroscopy, UV spectroscopy, and transmission electron microscopy (TEM). Spectroscopic evidence suggests that the synthesized thiol surfactants have been attached to the gold nanoparticles. The effect of self-assembling of these surfactants on the size of the gold nanoparticles was studied using TEM images. The growth of the gold nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The results show that the stabilization of gold nanoparticles was affected by the increase in alkyl chain length of these surfactants. The effect of gold nanoparticles on the interfacial tension and the emulsion stability of these surfactants with crude oil was studied.     

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.     

Synthesis of cationic hyperbranched multiarm copolymer and its application in self-reducing and stabilizing gold nanoparticles

A novel hyperbranched multiarm copolymer of HBPO-star-PDEAEMA with a hydrophobic poly(3-ethyl-3-(hydroxymethyl) oxetane)(HBPO) core and many cationic poly(2-(N,N-diethylamino) ethyl methacrylate)(PDEAEMA) arms has been synthesized through an atom transfer radical polymerization(ATRP) method,and been applied to spontaneously reduce and stabilize gold nanoparticles(AuNPs) in water without other additional agents.The size of the nanoparticles could be effectively controlled at about 4 nm,and the nanoparticles ...