Oxygen surface-functionalized carbon dots derived from waste cassava peel for UV shielding applications

UV radiation, falling in the wavelength range between 290 nm and 400 nm, which reaches the Earth's surface, is capable of causing potential damage to human cells, especially the skin. Sun protection products, which were earlier treated as skincare utilities, have now become indispensable and fall under the category of healthcare commodities. The requirement for skin- and environment-friendly UV absorbers that are reliable enough to substitute synthetic ones is spiking day by day. In this work, we report the conversion of waste cassava peels into UV-absorbing carbon dots through a facile one-step microwave-assisted solvothermal route. The as-synthesized carbon dots, when dispersed in NMP, show intense absorption in the UVA and UVB region, which can be effectively used for UV shielding applications. In-vitro studies based on transmittance data show that dispersion is capable of blocking 90% of the UV rays at a concentration of 0.2 mg/mL, and at 0.5 mg/mL, an SPF of 35+ was obtained, corresponding to a shielding capability of more than 97%. The conversion of cassava peel waste into UV-absorbing carbon dots adds to the value of this agricultural waste and, on crossing the compatibility standards, would provide a suitable alternative for existing synthetic UV shielding materials.