Highly bright carbon quantum dots for flexible anti-counterfeiting

Abstract

Carbon quantum dots (C-dots) have attracted increasing attention because of their nontoxic composition and excellent optical properties, which have seen them widely used as building blocks for various types of optoelectronic devices. However, the large-scale synthesis of C-dots with a high quantum yield is a big challenge. Herein, C-dots were synthesized via a vacuum heating approach, which could provide over 100 g per batch. The purified C-dots had an ultrahigh quantum yield of ∼79%, absorption peaks at 330 and 405 nm, and a narrow fluorescence spectrum with a main peak centered at 520 nm. As a proof of concept, an as-prepared C-dots/polymer aqueous solution was used as a security ink for textile anti-counterfeiting. After printing the ink into the cotton fabrics, the C-dots still had a quantum yield of 42%. By mixing with other colored C-dots, a multiple colored anti-counterfeiting security code was obtained, which could greatly enhance the anti-counterfeiting level. This study provides a reliable approach to provide high-quality C-dots in a large scale and may open possibilities to use C-dots for potential flexible anti-counterfeiting and optoelectronic applications.