Structural and spectral investigations of Rhodamine (Rh6G) dye-silica core-shell nanoparticles

Rhodamine (Rh6G) dye-silica core-shell nanoparticles (DSCSNPs) have been prepared by the controlled hydrolysis and condensation of single silica precursor tetraethylorthosilicate (TEOS) using the sol-gel method. Scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis reveal that dye molecules are entrapped in silica (SiO₂) shell resulting into core-shell particles of ∼30 nm diameter. These particles are also characterized by X-ray diffraction and Fourier transforms infrared spectroscopy. The results indicate that core-shell particles are all in spherical shape and have a narrow size distribution. The fluorescent and optical properties of core-shell particles have been investigated using fluorescence and UV-Visible absorption spectra. The photoluminescence in solid or liquid medium occurs at the same wavelength. The SiO₂ shell restricts the leakage and photobleaching of dye efficiently. These core-shell nanoparticles are found to be highly luminescent and stable.