Fluorinated carbon dots/carboxyl methyl cellulose sodium composite with a temperature-sensitive fluorescence/phosphorescence applicable for anti-counterfeiting marking

Carbon dots (CDs) have attracted extensive attention due to their excellent optical properties , especially in the tunable photoluminescence (PL) (including fluorescence, delayed fluorescence and phosphorescence) and high photostability. However, the thermal stimuli-responsive PL from CDs based materials is still rare reported so far. In this work, we report a facile, large-scale synthesis of a polymer nanocomposite containing fluorinated carbon dots (FCDs) by using a commercial, water-soluble polymer carboxyl methyl cellulose sodium (CMCNa) as a stabilizing matrix. The as-synthesized FCDs-CMCNa shows both solid-state fluorescence and room temperature phosphorescence (RTP). More interestingly, with temperature decreasing from 300 to 90 K, the FCDs-CMCNa presents a peculiar temperature-sensitive optical property that its fluorescence/phosphorescence intensity both increase with temperature decreasing to a turning point of 150 K and then decline gradually as temperature decreasing to 90 K. This peculiar temperature-sensitive optical property of FCDs-CMCNa can be applied in advanced anti-counterfeiting, information encryption and thermo-sensitive sensors.