Pyrolysis of single carbon sources in SBA-15: A recyclable solid phase synthesis to obtain uniform carbon dots with tunable luminescence

Most of carbon dots (CDs) are synthesized in solutions, but the extensive use of solvents produces too much waste, needs complex purification and results in low yield. Particularly for the popular hydrothermal/solvothermal syntheses, safety issues hinder the large-scale production of CDs. Solid phase synthesis in air seems perfect to solve the above problems once for all, but nanoparticle growth in solid phase is always difficult to control. Here we suggest a new method to synthesize CDs in SBA-15 template, just by heating single carbon sources in air. Employing single carbon sources is important, which ensures both homogeneity of the nucleation and uniformity of the nanoparticle growth. The pores confinement of SBA-15 guarantees the uniform sizes of CDs, while the catalytic effect of SBA-15 accelerates the carbonization process of precursors. The products are easily extracted from the template by ethanol, and then the template can be recycled for the next synthesis after calcination. Various CDs are synthesized in this way by using different carbon sources and SBA-15 templates with different pore diameters, respectively. The results show that, the fluorescence properties of these CDs are determined by their composition and surface states, but not the particle sizes. This work opens a new avenue to synthesize uniform CDs in solid phase with high yield, low cost and tunable luminescence.