Papers by Keyword: Gold Nanoparticle

Abstract: A reusable electrochemical biosensing strategy based on gold nanoparticle involved layer-by-layer self-assembly for sensitive detection of single nucleotide polymorphisms is proposed in this study. Making use of the strong sulfur-Au affinity, ethanthiol and capture probe modified gold nanoparticles are self-assembled onto the surface of gold electrode successively. The target DNA hybridizes with the capture probe and ferrocene labeled signaling probe successively via sandwich hybridization reaction. By measuring ac current voltammetry, the target DNA can be sensitively detected in a linear dynamic range from 4.1-410 nM with a low detection limit of 2 nM. Making use of self-assembled gold nanoparticles layer, a large amount of capture probes can be modified onto the gold electrode, supporting the high sensitivity of the proposed strategy. In addition, good reproducibility, high selectivity and stability are achieved. In particular, the biosensor can be easily regenerated by melting in hot water, making it reusable.

Abstract: A nanostructured hybrid consisting of a high-density and uniform assembly of gold nanoparticles (AuNPs) on multiwalled carbon nanotubes (MWCNTs) is always desired and demanded in various applications. However, a simple, cost effective and highly efficiency method is required in the fabrication of MWCNTs-AuNPs nanohybrids. This study introduces a method where MWCNTs were functionalizing with nitric acid (HNO₃) and sulphuric acid (H₂SO₄) in ratio of 1:3 v/v by using ultrasonication. These functionalized MWCNTs served as substrates for gold nanoparticle deposition. Later, it was pre-mixed with tri-sodium citrate (Na₃C₆H₅O₇.2H₂O), next it was reacted with nobel metal (AuNPs) via the addition of chloroauric acid (HAuCl₄) at various pH. When HAuCl₄ was added to the reaction system, Au³⁺ was directly reduced at the surface of the MWCNTs and gold nanoparticles were assembled along the MWCNTs. Fourier Transform Infrared (FTIR), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray (EDX) analysis and dispersion test were used to characterize the MWCNTs/AuNPs nanocomposites. The fully functionalized MWCNTs using acid oxidation at 4 hour using ultrasonication were used in synthesis of nanohybrids, and the optimum gold yield on MWCNTs obtained at pH 4. Compared to other methods, these procedures require low temperature without involving the need of any catalyst or surfactant which results in a simple and efficient method for fabrication of gold nanoparticles on carbon nanotubes.

Abstract: A single step method for the synthesis of gold nanoparticles decorated graphene oxide nanocomposite using aniline as reducing agent has been developed. The composite was characterized using FE-SEM, UV-Vis and FT-IR and XRD analysis. The electron transfer behavior of the modified electrodes was investigated in a redox probe using cyclic voltammetry. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to evaluate the electrochemical properties of AuNPs/GO/GCE towards the electrochemical oxidation of tryptophan. A calibration graph was constructed by plotting the concentration of tryptophan against the peak current. Under the optimum experimental conditions, the oxidation peak currents were measured by varying the tryptophan concentrations. The resulting sensor displays an excellent repeatability and long-term stability.

Abstract: Gold nanoparticles coated on indium tin oxide substrate have been attracting great attention due to their excellent optical, electronic, electrocatalytic and biosensing application in recent years. In this paper, recent research progress in the preparation methods of gold nanoparticles on indium tin oxide substrate surface such as assembling with polymer, seed-mediated growth method and electrodeposition are presented. The applications of gold nanoparticles modified indium tin oxide substrate are also reviewed in electrode, catalyst, sensors and biochemical analysis.

Abstract: A periodic structure of gold nanoparticles (AuNPs) is formed by reducing a solution of gold chloride using novel plasma techniques, where a spatio-periodically generated plasma is transcribed to the AuNP structure formed on the ionic liquid (IL) surface under the strong magnetic field. In addition, it is found that a ring-shaped AuNP structure is formed corresponding to the shape of a ring electrode inserted into the plasma, where the AuNPs are synthesized at the position without plasma irradiation due to the shielding by the ring electrode. On the other hand, the periodic structure of the AuNPs are synthesized on the carbon nanotubes (CNTs) working as a template, where the controlled ion irradiation to the IL including functional groups can realize the distance-controlled synthesis of the AuNPs by dissociation of the IL and the functionalization of the CNTs by the dissociated carboxyl and amino groups. Furthermore, DNA is used as the functional group which connects the AuNPs to the CNTs. The mono-dispersed and high-density AuNPs are synthesized on the CNTs in the same way as the carboxyl and amino groups.

Abstract: Gold nanoparticles (AuNPs) having particle size less than 10 nm can exhibit enhancement of surface area to give high activity such as in catalytic reaction. However, it is hard to synthesize AuNPs with small particle size due to the strong agglomeration. Herein we report that channels of mesoporous silica synthesized via the template sol-gel synthesis can be used to prepare AuNPs by calcination method. Mesoporous silica with an interpore distance of 4.1 nm was successfully fabricated as transparent thin film by using an amphiphilic trinuclear gold (I) pyrazolate complex as a template for the sol-gel synthesis. Upon calcination at 450 °C for 3 h, silica film nanocomposites showed red-shifting of surface plasmon resonance (SPR) bands from 518 (AuNPs from the bulk) to 544 nm owing to decreasing of the average particle size. The formation of AuNPs was also supported by the appearance of diffraction peaks of d₁₁₁ at 2θ = 38.20° having a cubic phase. Moreover, transmission electron microscope (TEM) images and X-ray diffraction (XRD) peaks also showed smaller and more homogenous distribution of AuNPs.

Abstract: In this paper, we fabricated the 4-aminobenzenethiol modified gold nanoparticles onto polymer spheres as SERS substrate to selectively detect 2,4,6-trinitrotoluene (TNT) explosives. The gold nanoseeds were fixed on polymer surface by reduction of HAuCl₄·3H₂O with sodium citrate. About 60~100nm nanoparticles were formed from the previous seeds and self-assembled by 4-aminobenzenethiol. The functionalized gold nanopartilces aggregation coated on large polymer sphere surface not only absorbed more TNT molecules via conjugation system, but also generated numerous "hot spots". It was demonstrated that this substrate displayed high SERS activity for TNT detection. It could also be anticipated that the aforementioned material would be used for fast and sensitive SERS detection of TNT in real-world situation. Keywords: gold nanopartilces, SERS, TNT, functionalization

Abstract: This paper reports a novel and facile activation process for electroless copper plating on Acrylonitrile Butadiene Styrene (ABS) plastic substrate using gold nanoparticles as catalyst. Gold nanoparticles were prepared by chemical reduction method and characterized by UVvisible adsorption spectrum and transmission electron microscope (TEM). The gold nanoparticles were sphere-like with a size of less than 50 nm. Gold nanoparticles were adsorbed on ABS surface and acted as nucleation centers in activating process of the electroless copper plating. The uniform and dense film was obtained at the optimal technological parameters which were achieved by the orthogonal experiment. The scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) were used to detect the morphology, structure and elemental composition of the coating, respectively. The results indicated that copper coating contained only Cu (0) without any other elements.

Abstract: An immunosensor is an analytical system consisting of specific immune system molecules coupled to a signal transducer. Immunosensor sensitivity depends on the type of immunorecognition ligands used, immobilization influence on their activity and orientation on the surface. Quartz crystal microbalance with dissipation (QCM-D) was employed to investigate the immobilization of antibodies against bovine leukemia virus antigen gp51 (gp51). Disulphide bridges of antibody hinge region were reduced chemically to yield two half antibody fragments (Frag-Ab), each having a single antigen binding site and free sulfhydryl groups that were used for immobilization. Frag-Ab were immobilized on planar gold and gold nanoparticle (AuNP) modified QCM-D sensor surfaces from initial solutions of different concentrations. Higher Frag-Ab surface density values were obtained on AuNP modified surfaces at all tested antibody concentrations. Frag-Ab/gp51 specific interaction was registered and it was determined that the highest sensitivity was exhibited by Frag-Ab immobilized at the lowest surface desities on both types of investigated surfaces. Specific gp51 interaction with Frag-Ab and non-specific binding to bovine serum albumin modified surfaces were compared by employing Δf/ΔD plots, which could serve as fingerprints of different processes.

Abstract: Au/MeO_x (MeO_x - SiO₂, Al₂O₃ and TiO₂) nanocomposites have been produced by the extractive-pyrolytic method. An organic extract – a solution of n-trioctylammonium tetrachlorolaurate ([Oct₃NH]AuCl₄) in toluene – was used as a gold-containing precursor. The produced samples were analyzed by IR spectroscopy, X-ray diffraction and scanning electron microscopy. The performed studies have shown that the mean size of the metal crystallites vary within wide limits: on Al₂O₃ from 60 nm to 35 nm; on SiO₂ from 33 nm to 23 nm; on TiO₂ from 50 nm to 13 nm.