Development of Carbon Dots Synthesized from Green Tea and Alpha‐hydroxyl Acids with Enhanced Antioxidant Activity, Photostability and UV Protection Properties

Abstract The exhaustion of the ozone layer in the atmosphere has caused an escalation of dangerous UV radiation penetrating the earth's surface. Reactive oxygen species generated under UV exposure through photocatalytic reactions can lead to severe skin health risks, such as skin cancer and premature aging. Although chemical sunscreens are widely used for protection against UV radiation, their long‐term use poses safety concerns and causes environmental damage. In this regard, we have developed carbon dots (CDs) with excellent UV absorption along with extraordinary antioxidant activity, photostability, and biocompatibility from green tea as the main precursor and alpha‐hydroxy acids (AHA) as the co‐precursors, including gluconic acid (GA), citric acid (CA), and tartaric acid (TA). All CDs have a strong UV absorption, especially in the UVB and UVC regions, with G‐CDs having the highest UV absorption. The G‐CDs also have the highest antioxidant activity, which is also higher than that of their parent green tea, AHAs, and ascorbic acid, a well‐known antioxidant. The photostability and cell viability of the G‐CDs were also excellent. The potential of G‐CDs as multifunctional materials makes them a promising candidate for cosmetic applications, particularly for their ability to absorb UV radiation with exceptionally high antioxidant activity, photostability, and biocompatibility.