Abstract
Current reports in the field of nanotechnology indicate that the properties of metal nanoparticles are determined by their features such as size, shape, composition as well as a degree of crystallinity and stability. These, in turn, may depend heavily on their preparation way, treatment during and after synthesis and finally on properties of the supports and matrices. The goal of presented work was to determine the shape, size, and distribution of silver nanoparticles depending on preparation conditions. In particular, the issues of the formation of silver nanostructures (AgNP) with various shapes and sizes depending on functionalized silica surface as well as on the conditions of the impregnation step by noble metal ions (especially pH) were considered. In particular, the comprehensive approach to determine the impact of pH conditions on the properties of metallic nanoparticles is laid down in this work. Three types of fumed silica materials were selected as the supports of silver nanostructures (Aerosil 150, Aerosil 300 and Silochrom C-120). Silica materials were chemically functionalized by thiol and amine groups and treated with diamminesilver(I) ions [Ag(NH3)2]+. As a result of their reduction silicas adorned with silver nanostructures were obtained. In this work, the AgNP in the form of very small nanoparticles, longitudinal and spherical forms and greater structures with nondescript shape were successfully received and characterized through changing the form of functional groups on the solid surface by adjusting the pH conditions. It turns out that protonation and deprotonation of thiol, amino, and hydroxyl groups can be responsible for possible interactions between noble metal ions and functional groups in the form of both attractive and repulsive electrostatic interactions. The Ag nanoparticle/silica nanocomposites were investigated by X-ray diffraction, atomic force microscopy, potentiometric titration and X-ray photoelectron spectroscopy.
Highlights
Functionalization of the support surface is often a precondition for many potential applications when the interactions between components can affect the stability of nanoparticles and colloids (Haddada et al 2013; Milczarek et al 2014)
An important advantage of the creation of silver nanoclusters embedded in a solid matrix is improving the stability of silver nanoparticles and the reduction of a silver amount in comparison to pure silver coatings resulting in lower toxicity
Noble metal nanoparticles can be incorporated into solid support by integration with carrier surface decorated by specific functional groups as amine or thiol species (Dharanivasan et al 2015)
Summary
Functionalization of the support surface is often a precondition for many potential applications when the interactions between components can affect the stability of nanoparticles and colloids (Haddada et al 2013; Milczarek et al 2014). We tried to determine the relationship between shape, size, and distribution of silver nanoparticles deposited on silica surface and preparation conditions, types of functionalized silica surface as well as on conditions of the impregnation step by noble metal ions (especially pH). Potentiometric titration results of thiol-functionalized pyrogenic silica samples suggest that the significant changes and shifts of surface charge after modification were not clearly marked.
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