Carbon dot-silica composite nanoparticle: an excitation-independent fluorescence material with tunable fluorescence

Based on the copolycondensation of tetraethoxysilane and glucose, a facile one-pot approach is explored in this paper to prepare composite nanoparticles of silica/carbon dots (SCDs) on a large scale. Glucose, the carbon source for the carbon dots (CDs), is pre-packaged by copolycondensation with tetraethoxysilane in silica nanoparticles. It is likely that this creative route can reversibly modulate the excitation-dependent behavior of CD fluorescence. Compared with the character of the blue emission belonging to the carbon dots (CDs), which are illuminated under a UV lamp, SCDs suspended in water show bright tunable fluorescence from green to yellow. Moreover, the excitation dependence of the photoluminescence (PL) of the CDs is unprecedentedly restricted with a limitation of the CDs' growth in the silica nanoparticles, and afterwards the excitation dependence of PL can be fully recovered by the removal of the silica. In the solid state, the SCDs remain strongly luminescent and show temperature-sensitive PL. These findings pave the way for mechanistic studies on the excitation dependent fluorescence and applications of CDs in bioimaging and phosphor powders.