Crescimento de nanopartículas de prata em substrato de sílica para futura aplicação em sensores ópticos

Abstract

One of the major challenges that currently exists is the development of materials and equipaments which detect and quantify substances in concentrations smaller and smaller. Nanomaterials Chemistry is an area of great potential in this development. A nanomaterial is a solid material having at least one dimension below a critical size where its properties as is conferred to conventional sizes, begin to undergo changes, which are directly dependent on the size and shape of this nanomaterial.An important class of nanomaterials are metallic nanoparticles, which stand out for their intensely different and fantastic optical properties. When electromagnetic waves propagate along an interface metal/dielectric medium creates a coupled electromagnetic field of the coherent oscillation of electrons in the conduction band way. Metal nanoparticles in the electric field induces polarization charges, the free electrons in the particle are displaced and the difference in the charge distribution gives rise to a restoring force generating resonance conditions in which the oscillation of free electrons is in phase with the electromagnetic radiation(Plasmon absorption). These properties (mainly gold, silver and copper nanoparticles in which have absorptions in the visible region of the electromagnetic spectrum) can be very useful for development, for example, optical sensors, which may cause the device a higher sensitivity and selectivity. In this study we sought growth of silver nanoparticles on a silica substrate and then construct a model system for this growth in a fiber optic sensor. The proposed route, with cleaning and surface treatment of the glass slide and silanization of the surface with 3-aminopropyltriethoxysilane and subsequent trapping of the metal and reduction of this, showed promise. Three concentrations of the coupling agent and three concentrations of the root silver (AgNO3) were used to control the size of these nanoparticles. The samples were characterized by the following techniques that qualitatively showed the existence of the material on its surface: UV-Vis spectroscopy in which we observed a Plasmon band, Raman spectroscopy in which it probed the existence of functionalizing, X-Ray Diffraction in which it characterized the presence of silver on the surface and transmission electron microscopy which allowed examine size and shape of nanoparticles synthesized. Other characterizations can also be used as Infrared Spectroscopy and Atomic Force Microscopy and quantitative analyzes should also be made for the future construction of a model system.