Luminescent mesoporous silica nanoparticles for biomedical applications: Synthesis and characterization

We report the synthesis and detailed characterization of intrinsically/lable-free luminescent mesoporous silica nanoparticles (L-MSN), which may have useful biomedical applications. These particles were prepared by modified Stober's method followed by calcination. By optimizing the ratio of (3-aminopropyl triethoxysilane) APTS to tetraetthoxysaline (TEOS), particles with size similar to 43 nm and size dispersion similar to 12% were obtained. The luminescence of L-MSN is suggested to be due to the formation of carbonaceous compounds, giving particles yellowish brown color, during the process of calcination at optimum temperatures similar to 400 degrees C. Interestingly, our studies suggest that these carbonaceous impurities are carbon dots (C-Dots) and fluorescence anisotropy decay measurements indicate C-Dots as integral part of L-MSN. Luminescent properties of L-MSN were found to be stable as a function of pH as well as long time light exposure. Our results suggest that L-MSN may be explored for biomedical imaging as well as drug delivery applications.