Influences of boron and nitrogen co-doped carbon dot based coating fabricated via layer-by-layer self-assembly on the UV protection and flame retardancy of cotton fabric

Boron and nitrogen co-doped carbon dots (BN-CDs) were synthesized using one-pot hydrothermal carbonization. The synthesized CDs were then combined with alginate and polyethyleneimine to create a multilayered coating on cotton fabric through layer-by-layer (LbL) self-assembly. The CD-containing coating emitted visible blue light under a 365 nm UV lamp. The UV protection, thermal stability, flame retardancy, and wash durability of the CD-treated cotton fabric were subsequently investigated. The ultraviolet protection factors of pure cotton fabric and cotton fabric treated with 12 bilayer CD-containing coating were 6.48 and 64.10, respectively. This indicated that the synthesized CD is an efficient UV absorber. In the TGA test, more char residue was observed at 700 °C for CD coated cotton fabrics under a nitrogen atmosphere. After B, N co-doped CDs were enriched in the PEI/alginate multilayered coating, the peak heat release rate (PHRR) of cotton-CDs-12BL was reduced by 15%, and the T_PHRR of cotton-CDs-12BL was improved by 26.4 °C in the microscale combustion calorimeter test. These results indicate that B, N co-doped CDs which possess UV absorption and environmental friendliness, have potential application as a flame retardant on the surface of cotton fiber.