Waste Biomass Originated Biocompatible Fluorescent Graphene Nano-Sheets for Latent Fingerprints Detection in Versatile Surfaces

In recent years, the application of biocompatible and non-toxic nanomaterials for the detection of fingerprints has become the major interest in the forensic sector and crime investigation. In this study, waste chickpea seeds, as a natural resource, were bioprocessed and utilized for the synthesis of non-toxic graphene nano-sheets (GNSs) with high fluorescence. The graphene GNS were synthesized via pyrolysis at high temperatures and were characterized by TEM, XPS, fluorescence and UV-Vis spectroscopy, and FTIR analysis. The GNS exhibited excitation-independent emission at about 620 nm with a quantum yield of over 10% and showed more distinct blue light under a UV lamp. Biocompatibility of the synthesized GNS in terms of cell viability (88.28% and 74.19%) was observed even at high concentrations (50 and 100 mg/mL), respectively. In addition, the antimicrobial properties of the synthesized GNS-based coatings were tested with the pathogenic strain of Bacillus cereus via live/dead cell counts and a plate counting method confirming their biocompatible and antimicrobial nature for their potential use in safe fingerprint detection. The developed chickpea-originated fluorescent GNS-based spray coatings were tested on different surfaces, including plastic, glass, silicon, steel, and soft plastic for the detection of crime scene fingerprints. Results confirmed that GNS can be used for the detection of latent fingerprints on multiple non-porous surfaces and were easy to detect under a UV lamp at 395 nm. These findings reinforce the suggestion that the developed fluorescent GNS spray coating has a high potential to increase sensitive and stable crime traces for forensic latent fingerprint detection on nonporous surface material. Capitalizing on their color-tunable behavior, the developed chickpea-originated fluorescent GNS-based spray coating is ideal for the visual enhancement of latent fingerprints.