Desenvolvimento de um substrato plasmônico para aplicação em biossensores.

Abstract

The goal of this work was to synthesize and characterize gold and silver nanoparticles, and obtaining thin films from these nanoparticles aiming for application in sensors for biomolecules detection. Metallic nanoparticles were synthesized through a procedure that allowed for controlled spherical shape with narrow size distribution. The results presented in this work were focused on the optical (plasmonic) properties of both nanoparticles and films (multilayer) adsorbed on 1cm2 of glass substrate, in addition to demonstrate the plasmonic sensitivity of these films on detecting the molecules bound to the plasmonic material surface. Gold and silver nanoparticles were synthesized by the reduction from their corresponding metallic ions, using as reducing agent and stabilizer sodium citrate and sodium borohydride in excess, respectively. Optical, sensing, electrochemical and morphological properties of the nanoparticles and thin films were obtained by uv-vis spectroscopy, scanning electron microscopy, energy dispersive spectroscopy and cyclic voltammetry (in this case the nanoparticles films were adsorbed on fluorine doped tin oxide). Uv-vis spectroscopy allowed monitoring the plasmonic bands shifts; evaluating the temperature effect on the optical properties of both colloidal nanoparticles and films of nanoparticles; evaluating the sensitivity of the plasmonic substrates to detecting changes in refractive index close to the surface and finally to detect binding events close to the surface using the interaction between biotin and streptavidin. Therefore the use of these metal nanoparticles in thin films is a simple, fast and effective for use in biosensors.