Precipitation Of Gold Nanoparticles Research Articles

Local control of optical absorption properties of glass using precipitation of gold nanoparticles via gold sphere movement driven by laser

Glass embedded with metal nanoparticles is a promising material necessary for optical devices because of its absorption properties associated with the surface plasmon resonance (SPR) of metal nanoparticles. We demonstrated that continuous-wave laser illumination of the metal sphere in glass migrates the metal sphere and dopes the migration trajectory. In this study, we have attempted to locally control the absorption properties of borosilicate glass via gold nanoparticle precipitation using gold sphere migration. The gold sphere was moved in the glass via laser illumination, and the gold nanoparticles were precipitated in the movement trajectory. The trajectory was colored in red and purple gradations because of the SPR of gold nanoparticles. The particle size of the precipitated gold nanoparticles and the absorption peak wavelength increased with increasing velocity of the gold sphere. The absorption properties of the trajectory depend on the velocity of the gold sphere migration, which enabled local control of the absorption properties of the glass.

Visible on-site detection of Ara h 1 by the switchable-linker-mediated precipitation of gold nanoparticles

Biosensors have been widely applied in tests for allergens, but on-site detection remains a challenge. Herein, we proposed a detection procedure for peanut Ara h 1 as a representative allergen, which was extracted from a cookie, thereby minimising the need for any complex pretreatment that was difficult to perform, and enabling the visual detection of the target without the use of analytical equipment. The extraction procedure was performed in less than 30 min using a syringe and filter (0.45 μm). The detection method for Ara h 1 was based on the aggregation of switchable linkers (SL) and gold nanoparticles (AuNP), and the presence of 0.19 mg peanut protein per 30 g of cookie could be confirmed within 30 min based on the AuNP/SL concentration ratio by the precipitation. This proposed procedure could be successfully applied to the detection of a wide range of food allergens.

Heterogeneous Precipitation of Gold Nanoparticles on PEI Coated Silica Gel

Heterogeneous Precipitation of Gold Nanoparticles on PEI Coated Silica Gel

Kinetic studies of gold(III) chloride complex reduction and solid phase precipitation in acidic aqueous system using dimethylamine borane as reducing agent

Kinetics of gold(III) chloride complex ions reduction with dimethylamine borane and precipitation of gold nanoparticles was investigated. The influence of concentrations of reductant, gold(III) chloride complex ions, neutral salt and chloride ions as well as temperature on the process was reported. Experimental results were used to determine parameters in the Arrhenius equation. A set of reactions occurring in the system was proposed. Rate equations were presented and verified. It was proposed that state of the catalytic surface of gold particles play a crucial role in the mechanism of the reaction and competition between AuCl4− adsorption and AuCl4− reduction on the metal particles exists in the system. Microscopic observations as well as analysis of the particles were also performed.

Precipitation of gold nanoparticles on insulating surfaces for metallic ultra-thin film electroless deposition assistance

In this work, the kinetics of 15 and 25nm gold nanoparticle (AuNP) precipitation on silanized SiO2/Si surfaces were studied. The NP coverage as well as distribution on the substrates was explored. It was found that at the beginning of the process, the 25nm AuNPs precipitate faster than their 15nm counterparts. However, early saturation and low final surface coverage by these NPs were observed. The 15nm AuNPs, exhibited higher (∼40%) surface coverage and precipitation saturation only after longer treatment times. This makes small NPs a promising candidate for catalyzing the deposition of ultra-thin metallic films on insulating substrates. In addition, it has been demonstrated for the first time that NPs, independently of their size, precipitate with a certain regularity and order. Using high-resolution scanning electron microscopy (HRSEM) it was observed that NPs are organized in pairs, and in each pair they are located at 50–60nm from each other and under certain angle.

Peptide-induced patterning of gold nanoparticle thin films

In this work, the use of patterned proteins and peptides for the deposition of gold nanoparticles on several substrates with different surface chemistries is presented. The patterned biomolecule on the surface acts as a catalyst to precipitate gold nanoparticles from a precursor solution of HAuCl 4 onto the substrate. The peptide patterning on the surfaces was accomplished by physical adsorption or covalent attachment. It was shown that by using covalent attachment with a linker molecule, the influence of the surface properties from the different substrates on the biomolecule adsorption and subsequent nanoparticle deposition could be avoided. By adjusting the reaction conditions such as pH or HAuCl 4 concentration, the sizes and morphologies of deposited gold nanoparticle agglomerates could be controlled. Two biomolecules were used for this experiment, 3XFLAG peptide and bovine serum albumin (BSA). A micro-transfer molding technique was used to pattern the peptides on the substrates, in which a pre-patterned poly(dimethylsiloxane) (PDMS) mold was used to deposit a lift-off pattern of polypropylmethacrylate (PPMA) on the various substrates. The proteins were either physically adsorbed or covalently attached to the substrates, and an aqueous HAuCl 4 solution was applied on the substrates with the protein micropatterns, causing the precipitation of gold nanoparticles onto the patterns. SEM, AFM, and Electron Beam Induced Current (EBIC) were used for characterization.

Light-responsive reversible solvation and precipitation of gold nanoparticles

Photo-irradiation with visible and UV light can be used to reversibly trigger the precipitation and solvation, in organic media, of Au nanoparticles coated with a rigid-rod type azobenzene.

Precipitation of gold nanoparticles on the quartz surface modified by titanium (IV) butoxide

Gold nanoparticles have been precipitated on the surface of quartz slides covered with titanium (IV) butoxide. UV irradiation of modified quartz slides immersed into water solutions of hydrogen tetrachloroaurate of different concentrations (2.5 × 10−4–1.0 × 10−2 M) has been used for this purpose. Properties of produced samples have been investigated by UV–Vis spectroscopy, IR spectroscopy, SEM-EDX, TGA, and AFM. According to the obtained data, produced gold particles are distributed on modified quartz surface very uniformly and the average size of gold particles is about 30–50 nm.

Mechanisms of the refractive index change in femtosecond laser-irradiated Au3+-doped silicate glasses

We report on the refractive index change in Au3+-doped silicate glasses irradiated by a femtosecond laser and successive heat treatment. The refractive index of the irradiated area increased after the femtosecond laser irradiation and decreased with increasing annealing temperature up to 450°C and then increased again with increasing annealing temperature. Absorption spectra of the glass samples before and after femtosecond laser irradiation and after further annealing manifested the formation of color centers after laser irradiation, disappearance of color centers after annealing at 300°C, and precipitation of gold nanoparticles after annealing at high temperature. The mechanisms of the observed phenomena are discussed.

Fabrication of a Photoelectrochemical Cell Using a Self-Assembled Monolayer of Tris(2,2'-bipyrisine)ruthenium(II)-Viologen Linked Thiol on Multistructured Gold Nanoparticles

A novel photoelectrochemical cell consisting of a modified electrode with a self-assembled monolayer of a tris(2,2'-bipyridine)ruthenium(II)-viologen linked thiol on the surfaces of a gold-particle multistructure, an indium-tin-oxide (ITO) electrode, and an aqueous electrolyte solution containing hydroxymethylferrocene, has been fabricated. The modified electrode was constructed by the precipitation of gold nanoparticles on a planar gold electrode, and by subsequent self-assembling of the thiol compound on the surfaces of the multistructure. The spatial separation between the modified electrode and the ITO electrode was as small as ∼12 µm, which was determined from the thickness of a polyimide film used for electrical insulation. The performance of the photoelectrochemical cell was investigated. Photocurrents and photovoltages increased with increasing number of immobilized molecules.