New Preparation Method of Gold Nanoparticles on SiO 2

Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México (UNAM), Circuito Exterior S/N, A. P. 70-186, C. P. 04510, Ciudad Universitaria, México D. F., Mexico. zanella@
The Journal of Physical Chemistry B (Impact Factor: 3.3). 06/2006; 110(17):8559-65. DOI: 10.1021/jp060601y
Source: PubMed


It is shown that adsorption of the [Au(en)(2)](3+) cationic complex can be successfully employed for the deposition of gold nanoparticles (1.5 to 3 nm) onto SiO(2) with high metal loading, good dispersion, and small Au particle size. When the solution pH increases (from 3.8 to 10.5), the Au loading in the Au/SiO(2) samples increases proportionally (from 0.2 to 5.5 wt %), and the average gold particle size also increases (from 1.5 to 2.4 nm). These effects are explained by the increase in the amount of negatively charged sites present on the SiO(2) surface, namely, when the solution pH increases, a higher number of [Au(en)(2)](3+) species can be adsorbed. Extending the adsorption time from 2 to 16 h gives rise to an increase in the gold loading from 3.3 to 4.0 wt % and in the average particle size from 1.8 to 2.9 nm. Different morphologies of gold nanoparticles are present as a function of the particle size. Particles with a size of 3-5 nm show defective structure, some of them having a multiple twinning particle (MTP) structure. At the same time, nanoparticles with an average size of ca. 2 nm exhibit defect-free structure with well-distinguishable {111} family planes. TEM and HAADF observations revealed that Au particles do not agglomerate on the SiO(2) support: gold is present on the surface of SiO(2) only as small particles. Density functional theory calculations were employed to study the mechanisms of [Au(en)(2)](3+) adsorption, where neutral and negatively charged silica surfaces were simulated by neutral cluster Si(4)O(10)H(4) and negatively charged cluster Si(4)O(10)H(3), respectively. The calculation results are totally consistent with the suggestion that the deposition of gold takes place according to a cationic adsorption mechanism.

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    • "The quest for creating application-specific nanostructures and the necessary tools to probe their characteristics is generating a significant research effort [1] [2] [3] [4] [5]. Geometric control at the nanoscale is typically facilitated chemically [6] [7] [8] [9] [10] [11], or by nanofabrication techniques [12] [13] [14] [15], with the use of electron beam lithography or ion beam milling. Another fabrication process, based on stamp-printing, has also been reported to produce nanoparticle-patterned microstructures [16]. "
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    ABSTRACT: A facile and environmentally benign synthetic route to decorate preformed amine functionalized silica spheres (SiO2) by in situ formation of gold nanoparticles (Au NPs) at three different concentrations (1, 2, and 3 mM) of Au precursor (HAuCl4) is reported. UV–Visible absorption spectra of SiO2@Au (1, 2, and 3 mM) NPs showed a characteristic surface plasmon resonance band due to the presence of Au NPs and transmission electron microscopic images confirmed that the Au NPs were accommodated on the surface of the amine functionalized SiO2 spheres without aggregation. Herein, N-[3-(trimethoxysilyl) propyl] diethylenetriamine acted as both reducing and stabilizing agent for the Au NPs and no other protecting agents were used. Cyclic voltammogram recorded for the SiO2@Au NPs modified glassy carbon (GC) electrode showed a characteristic electrochemical response due to the presence of Au NPs on the electrode. Electrocatalytic reduction of hydrogen peroxide (H2O2) was carried out at the SiO2@Au (1, 2, and 3 mM) NPs modified GC electrodes, among which the SiO2@Au (3 mM) NPs modified GC electrode produced the highest catalytic current. Electrochemical sensing of H2O2 was performed using linear sweep voltammetry at the SiO2@Au (3 mM) NPs modified GC electrode with an experimental detection limit of 5 μM. Graphical Abstract
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