Metal nanoparticles exhibit characteristics that are different from the bulk state, such as large surface to volume ratio and size-dependent properties, e.g, plasmon resonances in noble metal. The excitation of plasmon resonance (the collective oscillations of the conductive electrons) in silver nanoparticles (AgNPs), represent the most efficient mechanism, by which light interacts with matter. Based on the method developed in our laboratory, AgNPs are synthesized by the reduction of a saturated solution of silver oxide with hydrogen gas in the presence of silicate in water. The freshly synthesized particles have a narrow size distribution and are stable without additional stabilizing agents. There is a correlation between the concentration of silicate in solution with the size and concentration of synthesized AgNPs. Higher concentrations of silicate yield larger concentrations of small nanoparticles, while lower concentrations of silicate yield smaller concentrations of large nanoparticles for the same reaction time. It is assumed that silicate act as a stabilizing and catalytic agent. However, the initial interactions of silver ions (Ag+) and silicate ions (SiO32-) in solution will provide a foundation for understanding how silicate could affect the reaction with other metal ions. It is hypothesized that SiO32- make a low solubility intermediate complex with Ag+, because of the low solubility of this complex as well as the condensation polymerization nature of silicate. This complexe aggregates to form nanoparticles that function as nanoreactors in further reactions. The nanoreactor concentrates Ag+ making them available for reduction with hydrogen gas to form AgNps. The ability to synthesis of the clean, stable AgNPs with hydrogen gas in the presence of silicate highlights the versatility of other metal silicate intermediates. Sodium metasilicate can be a general approach for the synthesis of other metal nanoparticles and metal chalcogenide nanostructures such as Cu, Fe, Sn, Zn, and Bi sulfides. These nanoparticles were characterized by UV absorption, light scattering spectroscopy, atomic force microscopy, and powder X-ray diffraction.

Silicate metal complexes as a versatile intermediate for synthesis of metal nanoparticles and nanostructures

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