Development of a long-term fluorescent invisible marker using blue-emitting carbon dots

Abstract

The development of novel anti-counterfeiting materials and technologies is vital in order to combat counterfeit activities, as existing technologies such as optical watermarking, micro-printing, laser holography, barcodes, RFID, and QR codes are widely known to counterfeiters and easily replicated. In particular, several challenges and issues, including high costs, low yields during synthesis, and the photo-bleaching effect associated with the use of luminescent materials in anti-counterfeiting applications are still need to be addressed. Carbon Dots (CDs) is a new emergent in carbon family with excellent luminescence properties. In this report, we describe a fast, cost-effective, and simple one-step heating method for synthesizing CDs. An invisible marker was produced by incorporating blue emitting CDs into the reservoir of a commercial sketch pen. The writings using the marker were not visible under normal light but emitted blue fluorescence under UV light (365 nm). The marker retained its fluorescence for up to six months without any decrease visible to the naked eye.