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.