Great enhancement of red emitting carbon dots with B/Al/Ga doping for dual mode anti-counterfeiting

Red emitting carbon dots (RCDs) still suffer from low photoluminescence quantum yield (QY) and unclear luminescence mechanism. Group IIIA (B, Al, Ga) elements are firstly introduced to improve the QY of RCDs and the QY has been significantly increased from 0.29% to 12.02% (forty one times), 1.99% (seven times) and 1.53% (five times) for B-CDs, Al-CDs and Ga-CDs, respectively. The improvement of QY for RCDs is mainly originated from the formation of CNIIIAO bonds, which suppress the non-radiative transition with electron-withdrawing effects. In addition, B-CDs with acid-induced discoloration can be applied to a new anti-counterfeiting technology with dual mode, and this reversible process of acid-induced discoloration is originated from the reversibly switchable structure between BOH and BCl bonds.