A waterborne polyurethane‐based fluorescent tunable carbon quantum dot

Fluorescent tunable materials have potential applications in lighting, display, anti‐counterfeiting, biological probes, and so on. Herein, carbon quantum dots (CQDs) with blue fluorescence (BCDs), and yellow fluorescence (YCDs) were synthesized by solvothermal method using bio‐based citric acid and lignin as carbon sources, respectively. BCDs and YCDs were anchored on polyurethane chains to prepare waterborne polyurethane‐based blue fluorescent carbon quantum dots (BCDs1.0‐WPU) and waterborne polyurethane‐based yellow fluorescent carbon quantum dots (YCDs1.0‐WPU), respectively. Compared with the corresponding BCDs and YCDs, the fluorescence intensity of both BCDs1.0‐WPU and YCDs1.0‐WPU is markedly enhanced, and the emission peaks obviously show a hypochromatic shift. A waterborne polyurethane‐based fluorescent tunable carbon quantum dots (BCDsxYPDs1‐x‐WPU) is prepared by mixing the ratio of BCDs1.0‐WPU and YCDs1.0‐WPU with the RGB method. It is noteworthy that BCDsxYCDs1‐x‐WPU not only achieves a fluent change of fluorescence from blue to yellow but also emits strong white fluorescence (CIE coordinates: X = 0.28, Y = 0.32). The absolute value of the Zeta potential of BCDsxYCDs1‐x‐WPU is greater than 40, indicating good storage stability. Furthermore, the thermal decomposition temperature is above 225 °C, implying good thermal stability. Furthermore, BCDsxYCDs1‐x‐WPU uses water as a continuous phase and has potential applications in environmentally friendly luminescence, anti‐counterfeiting and biological probes.