Fabrication and Efficient Interfacial Assembly of Bright Red‐Emitting Carbon Quantum Dots for Security‐Warning Textiles

Abstract Carbon quantum dots (CQDs) have attracted more attentions due to their multiple performances. However, the fabrication of long‐wavelength emitting CQDs with aliphatic precursors still remains a challenge, mainly because it is difficult to generate large sp 2 domains to reduce energy gap, which is not conducive to a redshift of the luminescence peak. Hereon, by regulating the pH of citric acid and thiourea mixture, a N, S co‐doped CQD emitting bright red fluorescence at 635 nm is successfully fabricated through the solvothermal reaction under acidic condition, achieving a high quantum yield of 32.66%. Solvatochromic effects of the CQDs are discussed through theoretical equations and models, which confirm that the hydrogen‐bonding interaction dominates the fluorescence emission behavior of CQDs in polar solvents. Besides, a feasible strategy is proposed to prepare an anti‐counterfeiting textile via the deposition of red‐emitting CQDs onto cotton fibers, through rapidly evaporating the preferred organic solvent. As expected, the CQD‐decorated textiles exhibit encouraging anti‐counterfeiting and security‐warning functions, along with underwater and long‐distance detectability, washability, and sun resistance. It is worth noting that the present work is innovative in realizing the application of red‐light‐emitting CQDs in the fields of security‐warning textiles.