Gold Nanoparticles (gold + nanoparticle)

Distribution by Scientific Domains

Kinds of Gold Nanoparticles

  • colloidal gold nanoparticle
  • nm gold nanoparticle

  • Terms modified by Gold Nanoparticles

  • gold nanoparticle array

  • Selected Abstracts


    Gold Nanoparticle-Based Mediatorless Biosensor Prepared on Microporous Electrode

    ELECTROANALYSIS, Issue 3 2006
    Fenghua Zhang
    Abstract A mediatorless biosensor was fabricated with a double-sided microporous gold electrode by successively immobilizing a mixed self-assembled monolayer (SAM) comprising carboxylic-acid- and thiol-terminated thiolate (dl -thiorphan and 1,8-octanedithiol), glucose oxidase (GOx) and finally gold nanoparticle (Au NP) on one working side. The double-sided microporous gold electrodes were formed by plasma sputtering of gold on a porous nylon substrate, yielding a face-to-face type two-electrode electrochemical cell. While the straight chain molecule 1,8-octanedithiol forms a dense insulating monolayer, the side armed dl -thiorphan forms a low density layer for the diffusion of redox couples to the electrode surface. The mixed SAM not only provided the linking functional groups for both enzyme and Au NP but also resulted in the appropriately spaced monolayer for direct electron tansfer (ET) process from the center of the redox enzyme to the electrode surface. After covalently immobilizing GOx onto the carboxylic-acid-terminated monolayer, Au NP was easily immobilized to both enzyme and nearby thiols by simple dispensing of the colloidal gold solution. It was observed that the resulting amperometric biosensor exhibited quantitatively the same response to glucose in the presence and in the absence of dissolved oxygen, which evidence that the Au NPs immobilized on and around the GOx promote direct ET from the enzymes to the electrode, assuming the role of a common redox mediator. [source]


    Biotemplated Synthesis of Gold Nanoparticle,Bacteria Cellulose Nanofiber Nanocomposites and Their Application in Biosensing

    ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
    Taiji Zhang
    Abstract Bacteria cellulose (BC) nanofibers are used as robust biotemplates for the facile fabrication of novel gold nanoparticle (NP),bacteria cellulose nanofiber (Au,BC) nanocomposites via a one-step method. The BC nanofibers are uniformly coated with Au NPs in aqueous suspension using poly(ethyleneimine) (PEI) as the reducing and linking agent. With the addition of different halides, Au,BC nanocomposites with different Au shell thicknesses are formed, and a possible formation mechanism is proposed by taking into account the special role played by PEI. A novel H2O2 biosensor is constructed using the obtained Au,BC nanocomposites as excellent support for horseradish peroxidase (HRP) immobilization, which allows the detection of H2O2 with a detection limit lower than 1,µM. The Au,BC nanocomposites could be further used for the immobilization of many other enzymes, and thus, may find potential applications in bioelectroanalysis and bioelectrocatalysis. [source]


    Small-Molecule-Directed Assembly: A Gold Nanoparticle-Based Strategy for Screening of Homo-Adenine DNA Duplex Binders,

    ADVANCED MATERIALS, Issue 4 2008
    G. Song
    By using AuNP-modified homo-adenine DNA conjugate as a model system, simple colorimetric and resonance Rayleigh scattering assays have been developed for screening small molecules that trigger the formation of the non-Watson,Crick homo-adenine duplexes. The assay presented here is more simplified in format as it involves only one type of ssDNA modified Au-NP, and can be easily adapted to high-throughput screening. [source]


    Design of Gold Nanoparticle-Based Colorimetric Biosensing Assays

    CHEMBIOCHEM, Issue 15 2008
    Weian Zhao
    Abstract Gold nanoparticle (AuNP)-based colorimetric biosensing assays have recently attracted considerable attention in diagnostic applications due to their simplicity and versatility. This Minireview summarizes recent advances in this field and attempts to provide general guidance on how to design such assays. The key to the AuNP-based colorimetric sensing platform is the control of colloidal AuNP dispersion and aggregation stages by using biological processes (or analytes) of interest. The ability to balance interparticle attractive and repulsive forces, which determine whether AuNPs are stabilized or aggregated and, consequently, the color of the solution, is central in the design of such systems. AuNP aggregation in these assays can be induced by an "interparticle-crosslinking" mechanism in which the enthalpic benefits of interparticle bonding formation overcome interparticle repulsive forces. Alternatively, AuNP aggregation can be guided by the controlled loss of colloidal stability in a "noncrosslinking-aggregation" mechanism. In this case, as a consequence of changes in surface properties, the van der Waals attractive forces overcome interparticle repulsive forces. Using representative examples we illustrate the general strategies that are commonly used to control AuNP aggregation and dispersion in AuNP-based colorimetric assays. Understanding the factors that play important roles in such systems will not only provide guidance in designing AuNP-based colorimetric assays, but also facilitate research that exploits these principles in such areas as nanoassembly, biosciences and colloid and polymer sciences. [source]


    Electrocatalytic Oxidation of Nitrite at Gold Nanoparticle- polypyrrole Nanowire Modified Glassy Carbon Electrode

    CHINESE JOURNAL OF CHEMISTRY, Issue 12 2009
    Jing Li
    Abstract A novel chemically modified electrode based on the dispersion of gold nanoparticles on polypyrrole nanowires has been developed to investigate the oxidation behavior of nitrite using cyclic voltammetry, differential pulse voltammetry and chronoamperometry techniques. The diffusion coefficient (D), electron transfer coefficient (,) and charge transfer rate constant (k) for the oxidation of nitrite were determined. The modified electrode exhibited high electrocatalytic activity toward the oxidation of nitrite. The catalytic peak current was found to be linear with nitrite concentrations in the range of 8.0×10,7,2.5×10,3 mol·L,1 with a detection limit of 1.0×10,7 mol·L,1 (s/n=3). The proposed method was successfully applied to the detection of nitrite in water samples with obtained satisfactory results. Additionally, the sensor also showed excellent sensitivity, anti-interference ability, reproducibility and stability properties. [source]


    Design of Gold Nanoparticle-Based Colorimetric Biosensing Assays

    CHEMBIOCHEM, Issue 15 2008
    Weian Zhao
    Abstract Gold nanoparticle (AuNP)-based colorimetric biosensing assays have recently attracted considerable attention in diagnostic applications due to their simplicity and versatility. This Minireview summarizes recent advances in this field and attempts to provide general guidance on how to design such assays. The key to the AuNP-based colorimetric sensing platform is the control of colloidal AuNP dispersion and aggregation stages by using biological processes (or analytes) of interest. The ability to balance interparticle attractive and repulsive forces, which determine whether AuNPs are stabilized or aggregated and, consequently, the color of the solution, is central in the design of such systems. AuNP aggregation in these assays can be induced by an "interparticle-crosslinking" mechanism in which the enthalpic benefits of interparticle bonding formation overcome interparticle repulsive forces. Alternatively, AuNP aggregation can be guided by the controlled loss of colloidal stability in a "noncrosslinking-aggregation" mechanism. In this case, as a consequence of changes in surface properties, the van der Waals attractive forces overcome interparticle repulsive forces. Using representative examples we illustrate the general strategies that are commonly used to control AuNP aggregation and dispersion in AuNP-based colorimetric assays. Understanding the factors that play important roles in such systems will not only provide guidance in designing AuNP-based colorimetric assays, but also facilitate research that exploits these principles in such areas as nanoassembly, biosciences and colloid and polymer sciences. [source]


    Gold nanoparticles induce protein crystallization

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2008
    F. Hodzhaoglu
    Abstract Nucleation of protein crystals by gold nanoparticles was observed. Lysozyme and ferritin were used as model proteins. The effect was established with uncoated gold nanoparticles and with gold nanoparticles coated by 16-mercaptodecanoic acid. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Electroanalysis of Norepinephrine at Bare Gold Electrode Pure and Modified with Gold Nanoparticles and S-Functionalized Self-Assembled Layers in Aqueous Solution

    ELECTROANALYSIS, Issue 13 2009
    Teresa, uczak
    Abstract Gold nanoparticles (Au-NPs), cystamine (CA) and 3,3,-dithiodipropionic acid (DTDPA) modified gold bare electrodes were applied in voltammetric sensors for simultaneous detection of norepinephrine (NEP), ascorbic (AA) and uric (UA) acids. A linear relationship between norepinephrine concentration and current response was obtained in the range of 0.1,,M to 600,,M M with the detection limit ,0.091,,M for the electrodes modified at 2D template and in the range of 0.1,,M to 700,,M M with the detection limit ,0.087,,M for the electrodes modified at 3D template The results have shown that using modified electrodes it is possible to perform electrochemical analysis of norepinephrine without interference of ascorbic and uric acids, whose presence is the major limitation in norepinephrine determination at a bare gold electrode. The modified SAMs electrodes show good selectivity, sensitivity, reproducibility and high stability. [source]


    Electrochemical Aptasensor for the Determination of Cocaine Incorporating Gold Nanoparticles Modification

    ELECTROANALYSIS, Issue 13 2008
    Xiaoxia Li
    Abstract A novel electrochemical aptasensor incorporating a signal enhancement for the determination of cocaine was designed. Gold nanoparticles were self-assembled onto the surface of a gold electrode through 1,6-hexanedithiol. A bifunctional derivative of the 32-base cocaine-binding aptamer with a redox-active ferrocene moiety and a thiol linker group at the termini of the strand was self-assembled onto the surface of gold nanoparticles. The oxidation peak current is linearly related to the concentration of cocaine from 1.0 to 15.0,,M with a detection limit of 0.5,,M. It was found that the sensitivity of the aptasensor with gold nanoparticles modification was ca. 10-fold higher than that of the aptasensor without gold nanoparticles modification. This work demonstrates that gold nanoparticles-assembled gold electrode provides a promising platform for immobilizing aptamer and enhancing the sensitivity. [source]


    Study on the enhancement of Ru(bpy)32+ electrochemiluminescence by nanogold and its application for pentoxyverine detection

    ELECTROPHORESIS, Issue 23 2005
    Yingju Liu
    Abstract In this work, CE separation with end-column Ru(bpy)32+ ECL detection for the quantitative determination of pentoxyverine was firstly performed. The experimental conditions, such as the applied potential, injection voltage, injection time, and the pH of separation buffer, were discussed in detail. Gold nanoparticles were found to enhance the ECL intensity at an appropriate volume ratio of nanogold with Ru(bpy)32+ but without changing their nanoproperties proved by transmission electron microscopy (TEM) and UV-vis spectra. The detection limits with or without nanogold were 6,nM and 0.6,,M, respectively. Successful separation of pentoxyverine, chlorpheniramine, and lidocaine was achieved. This method was also applied to monitor drug binding with HSA, and the binding constant for pentoxyverine was estimated as 1.8×103/M. [source]


    3D Ordered Gold Strings by Coating Nanoparticles with Mesogens

    ADVANCED MATERIALS, Issue 17 2009
    Xiangbing Zeng
    Gold nanoparticles covered with a nematic liquid-crystal ligand laterally attached via a thioalkyl spacer and a thioalkane "diluent" exhibit 3D ordering in strings jacketed by the mesogens with controllable interparticle spacing. The particles form rhombohedral, hexagonal, and rectangular columnar superlattices, not the usual packing modes of spheres. [source]


    Cover Picture: Functionalized Gold Nanoparticles Mimic Catalytic Activity of a Polysiloxane-Synthesizing Enzyme (Adv. Mater.

    ADVANCED MATERIALS, Issue 10 2005
    10/2005)
    Abstract A system that acts as a biomimetic of the silica-synthesizing enzyme found in a marine sponge is reported by Morse and co-workers on p.,1234. Gold nanoparticles (GNPs) are functionalized with the same organic moieties that are found in the enzyme's catalytic site. Interaction between the nucleophilic (OH-terminated) and hydrogen-bonding (imidazole-terminated) GNPs, as shown on the cover, is required for the hydrolysis of a silicon alkoxide precursor and subsequent polycondensation to form silica at a low temperature and near-neutral pH. Replacement of either of the required functional groups by a non-reactive methyl group abolishes catalysis in this synthetic system, as it does in the biological enzyme. Cover art provided by Peter Allen. [source]


    Synthesis and photoluminescence properties of silicon nanowires treated by high-pressure water vapor annealing

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007
    B. Salhi
    Abstract This paper reports on silicon nanowires (SiNWs) growth on porous silicon (PS) template using vapor-liquid-solid (VLS) technique and the effect of high-pressure water vapor annealing (HWA) on their optical properties. Gold nanoparticles (Au NPs) with average mean diameter of 50 and 20 nm were used as catalysts. The SiNWs were obtained by thermal decomposition of silane gas (SiH4) at high temperature (540 °C) catalyzed by the Au NPs. The resulting nanostructures display comparable diameter to the initial gold catalysts and are few microns long without a preferential growth direction. We have next examined the optical properties of the 20 nm diameter SiNWs. As-prepared SiNWs display a weak photoluminescence (PL), which is related to the recombination emissions from defect centers. High-pressure water vapor annealing (HWA) at 260 °C and 2.6 MPa of the SiNWs led to an increase of the PL by a factor 10 without significant changes in the emission band. TEM analysis of the HWA-treated SiNWs showed a crystalline silicon core surrounded by an amorphous oxide layer. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Preparation and characterization of polyurethane,gold nanocomposites prepared using encapsulated gold nanoparticles

    POLYMER INTERNATIONAL, Issue 7 2010
    Chao-Ching Chang
    Abstract Gold nanoparticles (GNPs) have been widely studied due to their unique properties. Although many research groups have developed the synthesis of GNPs using various polymers as stabilizing or reducing agents, the effects of GNPs on the structures and properties of polymer matrices have been less reported. We propose a new design for the preparation of polyurethane,gold (PU,Au) nanocomposites. 11-Mercapto-1-undecanol-coated GNPs acted as the chain extenders and reacted with isocyanates to form covalent bonds between PU and GNPs. PU,Au nanocomposites were successfully synthesized, and the effects of multifunctional GNPs on the structures, morphology and properties of poly(ester urethane) were investigated. Scanning electron microscopy images suggested the GNPs can be dispersed uniformly in the PU matrix. Maltese-cross of spherical crystals was observed in the PU,Au nanocomposites, and the size of the crystals decreased with an increase in gold content. As the gold content increased, the thermal decomposition temperature and the temperature of the maximum decomposition rate increased. The glass transition temperature, crystal melting temperature and melting enthalpy of the soft segment also increased progressively. The results showed that multifunctional GNPs concentrated hard segments and resulted in an increase of heterogeneous nucleation, phase separation and elasticity. Copyright © 2010 Society of Chemical Industry [source]


    On-plate-selective enrichment of glycopeptides using boronic acid-modified gold nanoparticles for direct MALDI-QIT-TOF MS analysis

    PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 22 2009
    Jia Tang
    Abstract In this study, an on-plate-selective enrichment method is developed for fast and efficient glycopeptide investigation. Gold nanoparticles were first spotted and sintered on a stainless-steel plate, then modified with 4-mercaptophenylboronic acid to provide porous substrate with large specific surface and dual functions. These spots were used to selectively capture glycopeptides from peptide mixtures and the captured target peptides could be analyzed by MALDI-MS simply by deposition of 2,5-dihydroxybenzoic acid matrix. Horseradish peroxidase was employed as a standard glycoprotein to investigate the enrichment efficiency. In this way, the enrichment, washing and detection steps can all be fulfilled on a single MALDI target plate. The relatively small sample amount needed, low detection limit and rapid selective enrichment have made this on-plate strategy promising for online enrichment of glycopeptides, which could be applied in high-throughput proteome research. [source]


    Radiofrequency field-induced thermal cytotoxicity in cancer cells treated with fluorescent nanoparticles,

    CANCER, Issue 13 2010
    Evan S. Glazer MD
    Abstract BACKGROUND: Nonionizing radiation, such as radiofrequency field and near infrared laser, induces thermal cytotoxicity in cancer cells treated with gold nanoparticles. Quantum dots are fluorescent semiconducting nanoparticles that were hypothesized to induce similar injury after radiofrequency field irradiation. METHODS: Gold nanoparticles and 2 types of quantum dot (cadmium-selenide and indium-gallium-phosphide) conjugated to cetuximab (C225), a monoclonal antibody against human epidermal growth factor receptor (EGFR)-1, demonstrated concentration-dependent heating in a radiofrequency field. The authors investigated the effect of radiofrequency field exposure after targeted nanoparticle treatment in a coculture of 2 human cancer cell lines that have differential EGFR-1 expression (a high-expressing pancreatic carcinoma, Panc-1, and a low-expressing breast carcinoma, Cama-1). RESULTS: Radiofrequency revealed that Panc-1 or Cama-1 cells not containing gold nanoparticles or quantum dots had a viability of >92%. The viability of Panc-1 cells exposed to the radiofrequency field after treatment with 50 nM Au-C225 was 39.4% ± 8.3% without injury to bystander Cama-1 cells (viability was 93.7% ± 1.0%; P , .0006). Panc-1 cells treated with targeted cadmium-selenide quantum dots were only 47.5% viable after radiofrequency field exposure (P<.0001 compared with radiofrequency only Panc-1 control cells). Targeted indium-gallium-phosphide quantum dots decreased Panc-1 viability to 58.2% ± 3.4% after radiofrequency field exposure (P = ,.0004 compared with Cama-1 and Panc-1 controls). CONCLUSIONS: The authors selectively induced radiofrequency field cytotoxicity in Panc-1 cells without injury to bystander Cama-1 cells using EGFR-1,targeted nanoparticles, and demonstrated an interesting bifunctionality of fluorescent nanoparticles as agents for both cancer cell imaging and treatment. Cancer 2010. © 2010 American Cancer Society. [source]


    N -Formylation of Amines via the Aerobic Oxidation of Methanol over Supported Gold Nanoparticles

    CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 6 2009
    Tamao Ishida Dr.
    Abstract Dress code: formyl. Gold nanoparticles supported on NiO catalyze the one-pot N -formylation of amines with methanol and molecular oxygen to produce formamide at a selectivity of 90,%. This process generates methyl formate in situ, followed by reaction with amines. [source]


    Colorimetric Sensing of Adenosine Based on Aptamer Binding Inducing Gold Nanoparticle Aggregation

    CHINESE JOURNAL OF CHEMISTRY, Issue 10 2009
    Xueping Liu
    Abstract A simple and rapid colorimetric approach for the determination of adenosine has been developed via target inducing aptamer structure switching, thus leading to Au colloidal solution aggregation. In the absence of the analytes, the aptamer/gold nanoparticle (Au NP) solution remained well dispersed under a given high ionic strength condition in that the random-coil aptamer was readily wrapped on the surface of the Au NPs, which resulted in the enhancement of the repulsive force between the nanoparticles due to the high negative charge density of DNA molecules. While in the presence of adenosine, target-aptamer complexes were formed and the conformation of the aptamer was changed to a folded structure which disfavored its adsorption on the Au NP surface, thus leading to the reduction of the negative charge density on each Au NP and then the reduced degree of electrostatic repulsion between Au nanoparticles. As a result, the aggregation of the Au colloidal solution occurred. The changes of the absorption spectrum could be easily monitored by a UV-Vis spectrophotometer. A linear correlation exists between the ratio of the absorbance of the system at 522 to 700 nm (A522 nm/A700 nm) and the concentration of adenosine between 100 nmol·L,1 and 10 µmol·L,1, with a detection limit of 51.5 nmol·L,1. [source]


    Effect of gold nanoparticle on the microscopic morphology of white blood cell

    CYTOPATHOLOGY, Issue 2 2009
    V. Wiwanitkit
    Background:, In medicine, there is limited knowledge on the toxicity of nanoparticles. In medicine, there has been limited knowledge on the effect of nanoparticles on the white blood cell. Objective:, To evaluate the effect of gold nanoparticle on the microscopic morphology of white blood cell. Setting:, Chulalongkorn Univesity, Bangkok, Thailand. Method:, This study was performed as an experimental study. Mixture of gold nanoparticle solution and blood sample was prepared and analysed. Result:, This work revealed that after mixing the blood sample with gold nanoparticle solution, accumulation of gold nanoparticle in the white blood cell was observed. Conclusion:, The effect of gold nanoparticle on the white blood cell can be detected and this knowledge can be used in cytotoxic drug treatment. [source]


    Gold Nanoparticle-Based Mediatorless Biosensor Prepared on Microporous Electrode

    ELECTROANALYSIS, Issue 3 2006
    Fenghua Zhang
    Abstract A mediatorless biosensor was fabricated with a double-sided microporous gold electrode by successively immobilizing a mixed self-assembled monolayer (SAM) comprising carboxylic-acid- and thiol-terminated thiolate (dl -thiorphan and 1,8-octanedithiol), glucose oxidase (GOx) and finally gold nanoparticle (Au NP) on one working side. The double-sided microporous gold electrodes were formed by plasma sputtering of gold on a porous nylon substrate, yielding a face-to-face type two-electrode electrochemical cell. While the straight chain molecule 1,8-octanedithiol forms a dense insulating monolayer, the side armed dl -thiorphan forms a low density layer for the diffusion of redox couples to the electrode surface. The mixed SAM not only provided the linking functional groups for both enzyme and Au NP but also resulted in the appropriately spaced monolayer for direct electron tansfer (ET) process from the center of the redox enzyme to the electrode surface. After covalently immobilizing GOx onto the carboxylic-acid-terminated monolayer, Au NP was easily immobilized to both enzyme and nearby thiols by simple dispensing of the colloidal gold solution. It was observed that the resulting amperometric biosensor exhibited quantitatively the same response to glucose in the presence and in the absence of dissolved oxygen, which evidence that the Au NPs immobilized on and around the GOx promote direct ET from the enzymes to the electrode, assuming the role of a common redox mediator. [source]


    Biotemplated Synthesis of Gold Nanoparticle,Bacteria Cellulose Nanofiber Nanocomposites and Their Application in Biosensing

    ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
    Taiji Zhang
    Abstract Bacteria cellulose (BC) nanofibers are used as robust biotemplates for the facile fabrication of novel gold nanoparticle (NP),bacteria cellulose nanofiber (Au,BC) nanocomposites via a one-step method. The BC nanofibers are uniformly coated with Au NPs in aqueous suspension using poly(ethyleneimine) (PEI) as the reducing and linking agent. With the addition of different halides, Au,BC nanocomposites with different Au shell thicknesses are formed, and a possible formation mechanism is proposed by taking into account the special role played by PEI. A novel H2O2 biosensor is constructed using the obtained Au,BC nanocomposites as excellent support for horseradish peroxidase (HRP) immobilization, which allows the detection of H2O2 with a detection limit lower than 1,µM. The Au,BC nanocomposites could be further used for the immobilization of many other enzymes, and thus, may find potential applications in bioelectroanalysis and bioelectrocatalysis. [source]


    Nanoparticle-Dispersed Liquid Crystals Fabricated by Sputter Doping

    ADVANCED MATERIALS, Issue 5 2010
    Hiroyuki Yoshida
    A simple and robust method to prepare nanoparticle-dispersed liquid crystals is demonstrated. Highly dispersed gold nanoparticle,liquid crystal suspensions are fabricated by simply sputter doping the gold target on the host liquid crystal (see figure). The existence of the nanoparticles is supported by optical extinction measurements, polarization optical microscopy, and transmission electron microscopy. An improvement in the electro-optic response, namely, a decrease in the threshold voltage, is also demonstrated in twist nematic devices fabricated using the nanoparticle-dispersed liquid crystal. [source]


    Controlled Assembly of Protein,Nanoparticle Composites through Protein Surface Recognition,

    ADVANCED MATERIALS, Issue 5 2005
    S. Srivastava
    Controlled assembly of protein,nanoparticle composites through complementary protein surface recognition is demonstrated. Interaction of an unstable protein (chymotrypsin) with a gold nanoparticle results in close interparticle spacing, while a stable protein (cytochrome,C) that retains its structure upon binding produces a hybrid material with a larger interparticle distance (see Figure). [source]


    Label free optical sensor for Avidin based on single gold nanoparticles functionalized with aptamers

    JOURNAL OF BIOPHOTONICS, Issue 4 2009
    Frank Jeyson Hernandez
    Abstract Optical spectroscopy of a single gold nanoparticle, functionalized with an aptamer, is used to sense the specific binding of avidin. Herewith, the field of single noble metal nanoparticle biosensors is extended to the important field of aptamer based assays. The sensitivity of this initial, but not yet optimized apta-nano-sensor is in the range of 20 nM. Due to its nanoscopic size, this single nanoparticle based apta-sensor may be used in nanoscopic volumes such as in array type assays or even inside cells. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    First-principle calculations on CO oxidation catalyzed by a gold nanoparticle

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2010
    Hsin-Tsung Chen
    Abstract We have elucidated the mechanism of CO oxidation catalyzed by gold nanoparticles through first-principle density-functional theory (DFT) calculations. Calculations on selected model show that the low-coordinated Au atoms of the Au29 nanoparticle carry slightly negative charges, which enhance the O2 binding energy compared with the corresponding bulk surfaces. Two reaction pathways of the CO oxidation were considered: the Eley,Rideal (ER) and Langmuir,Hinshelwood (LH). The overall LH reaction O2(ads) + CO(gas) , O2(ads) + CO(ads) , OOCO(ads) , O(ads) + CO2(gas) is calculated to be exothermic by 3.72 eV; the potential energies of the two transition states (TSLH1 and TSLH2) are smaller than the reactants, indicating that no net activation energy is required for this process. The CO oxidation via ER reaction Au29 + O2(gas) + CO(gas) , Au29,O2(ads) + CO(gas) , Au29,CO3(ads) , Au29,O(ads) + CO2(gas) requires an overall activation barrier of 0.19 eV, and the formation of Au29,CO3(ads) intermediate possesses high exothermicity of 4.33 eV, indicating that this process may compete with the LH mechanism. Thereafter, a second CO molecule can react with the remaining O atom via the ER mechanism with a very small barrier (0.03 eV). Our calculations suggest that the CO oxidation catalyzed by the Au29 nanoparticle is likely to occur at or even below room temperature. To gain insights into high-catalytic activity of the gold nanoparticles, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source]


    Effect of pH and generation of dendron on single-step synthesis of gold nanoparticles using PEGylated polyamidoamine dendron in aqueous medium

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2010
    Atsushi Harada
    Abstract Three types of PEGylated polyamidoamine (PAMAM) dendrons were synthesized through PEGylation of primary amines at the periphery of second, third, and fourth generation dendrons. Au(III) precursors and the synthesized PEGylated PAMAM dendrons were mixed at various pHs to evaluate the effect of pH on gold nanoparticle (Au NP) synthesis by monitoring the change in surface plasmon resonance. The Au NP synthesis reaction was controlled by pH through the balance between protonated and deprotonated tertiary amines and the reactivity of Au(III) precursors. By using PEGylated PAMAM dendrons with higher generation, the obtained Au NPs had narrow size distribution with small average size because of the limitation of intermolecular space among PEGylated PAMAM dendrons for the growth to Au NP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1391,1398, 2010 [source]


    Encapsulation of a Single Metal Nanoparticle with Tunable Size in a Monodisperse Polymer Microcapsule

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 3 2009
    Haiqing Li
    Abstract A versatile approach to fabricate monodisperse poly[styrene- co -(divinyl benzene)] (PS- co -DVB) microcapsules that contain a single gold nanoparticle (AuNP) has been demonstrated. Using the PS- co -DVB microcapsule as a microreactor, aqueous HAuCl4 and NaBH4 solutions are subsequently infiltrated. The size of the resulting AuNP inside of the PS- co -DVB microcapsules is easily tunable by controlling the repeated infiltration cycles of aqueous HAuCl4 and NaBH4. PS- co -DVB microcapsules that contain a single silver and palladium nanoparticle are also obtained by following a similar protocol. [source]


    Photoluminescence effects on gold nano- particles modified by short single stranded DNA molecules

    MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2009
    O. Kysil
    Gold-Nanopartikel; Einzelstrang DNA; sichtbare Photolumineszenz; Photosensor Abstract The concept for a function of gold nanoparticle photosensor based on gold nanoparticle optical properties, depending on the size and architecture of their self , assemblies, is revised from the studies of modified by short ssDNA (5.4 nm length) selected gold nanoparticle (8.6 nm diameter) assembling in biosuspensions. Biosensing effect, collective photoluminescence in visible range of different size 2D, 3D assemblies from these nanoparticles, is revealed due to their controlled assembling in biosuspesions, dependent on ssDNA conformation, that changes gold core capping and therefore a force of interparticle interaction. Nanophotosensor is characterized by intensive photoluminescence maxima in two regions of visible range for tested biosuspensions due to detected difference in the self - assemblies' architecture of gold nanoparticles with different gold core capping by the ssDNA molecules. The emission maxima are 4.2x103 pps and 4.1x104 pps in (525,780) nm and (780,920) nm regions mainly for 2D assemblies as nanowires and 3D assemblies as circle holms, correspondently, in DNA buffer suspensions with different biomolecules. The results are explained addressing photoluminescence of gold nanoparticle assemblies to system of discrete electron states in valence and conductivity bands for gold nanoparticle model. Photolumineszenz-Effekt auf Gold Nanopartikel vermittelt durch kurze Einzelstrang DNA Moleküle Das Konzept für die Funktion der Goldpartikel Nanophotosensoren basiert auf den optischen Eigenschaften der Gold Nanopartikel abhängig von der Größe und Architektur ihrer ,Self-Assemblies", und wird auf Basis von Studien von kurzen ssDNA (5.4 nm Länge) mit ausgewählten sich in Biosuspensionen versammelnden Gold Nanopartikeln (8.6 nm Durchmesser) revidiert. Der Biosensoreffekt, sichtbar durch die gesammelte Photolumineszenz im sichtbaren Spektrum von verschieden großen 2D und 3D-Aggregaten von diesen Nanopartikeln, wird wegen ihrer kontrollierten Ansammlung in Biosuspensionen, welche in Abhängigkeit zu den kurzen ssDNA Konformation, dem Ändern der monomolekularen Bedeckungsschicht des Goldkerns und somit durch eine Kraft der Teilchen-Wechselwirkung offenbart. Der Nanophotosensor ist durch zwei intensive Photolumineszenz-Maxima im Bereich des sichtbaren Spektrums für derart geprüfte Biosuspensionen wegen des meßbaren Unterschieds in der Selbstanordnung von Gold Nanopartikeln mit dem verschiedenen Goldkernbedeckungen durch die ssDNA Stränge charakterisiert: Emissionsmaxima liegen bei 4.2x103 pps und 4.1x104 pps in den Wellenlängenbereichen von (525,780) nm und (780,920) nm, jeweils hauptsächlich für 2D-Aggregate als Nanodrähte und 3D-Aggregate in kreisförmiger Anordnung in DNA-Puffersuspendierungen mit verschiedenen Biomolekülen. Die Ergebnisse werden Mithilfe der Adressierung der Photolumineszenz von Gold Nanopartikel-Aggregaten zu System von getrennten Elektronzuständen in Valenz und Leitungsbändern entsprechend den Gold Nanopartikel-Modellen erklärt. [source]


    Carbohydrate-Encapsulated Gold Nanoparticles for Rapid Target-Protein Identification and Binding-Epitope Mapping

    CHEMBIOCHEM, Issue 7 2005
    Yu-Ju Chen Dr.
    Carbohydrate,lectin recognition plays important roles in cell,cell communication, proliferation, and differentiation. We report here a new approach of using a carbohydrate-encapsulated gold nanoparticle (shown in purple) as an affinity probe for the efficient separation and enrichment of target proteins, and then protein identification and epitope mapping by MALDI-TOF MS. [source]


    Fabrication, Characterisation and Voltammetric Studies of Gold Amalgam Nanoparticle Modified Electrodes

    CHEMPHYSCHEM, Issue 9 2004
    Christine M. Welch
    Abstract The fabrication, characterisation, and electroanalytical application of gold and gold amalgam nanoparticles on glassy carbon electrodes is examined. Once the deposition parameters for gold nanoparticle electrodes were optimised, the analytical utility of the electrodes was examined in CrIIIelectroanalysis. It was found that gold nanoparticle modified (Au-NM) electrodes possess higher sensitivity than gold macroelectrodes. In addition, gold amalgam nanoparticle modified (AuHg-NM) electrodes were fabricated and characterised. The response of those electrodes was recorded in the presence of important environmental analytes (heavy metal cations). It was found AuHg-NM electrodes demonstrate a unique voltammetric behaviour and can be applied for electroanalysis when enhanced sensitivity is crucial. [source]