Síntese e propriedades ópticas de nanopartículas de prata e resinas compostas/AgNPs

Abstract

The aim of this study was to synthesize silver nanoparticles (AgNPs) and use fluorescence microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis) to investigate the optical properties of composite resins and composite resins doped with AgNPs. To this end, solutions of AgNPs were synthesized at different concentrations (0.5; 1.0; 1.5; 2.0 and 2.5 mM). From the aforementioned characterizations, it could be seen that the synthesis of AgNPs with the NaBH4 reductant is an effective chemical method for synthesizing AgNPs with very small sizes, less than 10 nm in diameter, low/moderate polydispersity and low anisotropy. Based on MET measurements and the Mie-Gans theory, it was observed that increasing the concentration of precursor and reducer in a 1:1 ratio contributed both to increasing the average particle size and the concentration of the solutions (in the nanomolar range). Films were then made with Charisma Classic composite resin (Heraeus Kulzer®, Germany) A1 (lighter color) and A3 (darker color). UV-Vis spectroscopy showed a characteristic band at 340 nm for both resins, indicating the presence of titanium dioxide (TiO2). Fluorescent microscopy revealed the presence of substances such as Bis-GMA, TEGDMA, UDMA, TiO2 and camphorquinone, which are responsible for their fluorescent emission. In addition, both resins have the same fluorescent emission spectrum, indicating that what makes them different is basically the concentration of the substances used in each one. Because they have the same composition, the FTIR graphs showed the same vibration frequencies for both resins. After this, UV-Vis spectroscopy and fluorescence microscopy tests were carried out. A shift in the plasmon band of AgNPs of 30 nm was noted when they were incorporated into the resin. This is due to the change in medium (water to resin) and also the preparation method, which involves changing the temperature. The effect of the AgNPs on the luminescence of the resins was also analyzed and a large reduction in the fluorescence amplitude was observed, with no change in the wavelength of the emission peaks. This phenomenon was explained by Foster-type energy transfer. With these results, a contribution was made to the field of synthesis and characterization of nanomaterials, and the effectiveness of using fluorescent microscopy for the analysis of AgNPs in composite resins was proven, thus contributing to the development of future studies.