Synthesis of nitrogen-doped carbon dots with 3-aminoquinoline and citric acid as an absorbent in full ultraviolet bands and application of transparent sunscreen umbrella

In recent years, as the global climate continues to deteriorate, the harm of ultraviolet(UV) radiation to the human body is increasing, but the development of commercial UV-blocking products has not followed the corresponding update. Carbon dots (CDs) are excellent candidates for UV absorbers because of their multi-functional groups, high stability, and low toxicity. In this study, full UV bond absorbing CDs (3A-CDs) were synthesized by a one-step hydrothermal method using anhydrous Citric acid(CA) and 3-aminoquinoline as raw materials. The 3A-CDs have super high UV absorption efficiency, light-aging resistance, and acid and alkaline resistance. Subsequently, different concentrations of 3A-CDs were doped into PVA to prepare 3A-CDs@PVA films with excellent full UV bond absorption and good mechanical properties. Finally, 3A-CDs@PVA films were sandwiched between two pieces of transparent umbrella cloth. The 0.3 wt% 3A-CDs@PVA film with transparent umbrella cloth can achieve a blocking efficiency of more than 97.2% in the full UV bands. Also, SPF is greater than 50, PFA is PA++++, and the visible light transmittance is as high as 93.8%. This study provides a new application and prospect for the development of CDs and their composite products into new, efficient, and durable UV-blocking products.