Synthesis of carbon quantum dots based on hemp leaves and cysteamine for latent fingerprint detection and their potential therapeutic anticancer application

In this study, an eco-friendly one-pot hydrothermal method was used to synthesize carbon quantum dots (CQDs) using hemp leaves and cysteamine hydrochloride as the carbon and nitrogen-sulfur sources, respectively. Synthesized carbon quantum dots (HC-CQDs) were developed to achieve the clear detection of latent fingerprints (LFPs) on non-porous materials under UV-light, and their nontoxicity to humans was verified by testing on cancer cells. HC-CQDs characterized by various techniques exhibited a high quantum yield of 36.1%, and their excitation and emission peaks appeared at 354 and 434 nm, respectively. For the detection of LFPs, we prepared a fluorescence fingerprint powder utilizing HC-CQDs, cellulose nanofiber (CNF), chitosan, and cassava starch. Results showed a complete fingerprint, and it was possible to clearly identify the location and type of defects on the fingerprint (minutiae). Additionally, we performed MTT assays to understand the effect of HC-CQDs on cell viability in cancer cell lines. HC-CQDs exhibited pronounced anti-cancer activity against A549 lung carcinoma cells while demonstrating negligible cytotoxic effects on normal Vero cells. Therefore, this study successfully developed plant-based fluorescent carbon quantum dots, which can be used to prepare a fluorescent powder for detecting LFPs that is safe for forensic scientists. These HC-CQDs also possess potential in inhibiting A549 lung cancer cells, which could be further developed in the medical field.