A carbon dots green nanotechnology approach for recovering latent fingerprints on fired and unfired firearm cartridge cases

A persistent misconception in forensic science is that firearm discharge destroys fingerprint residues, causing fired cartridge cases to be overlooked during examination. Conventional techniques, including powder dusting and cyanoacrylate fuming, may perform poorly on thermally stressed metallic surfaces. This study developed an eco-friendly fluorescent powder using carbon dots (CDs) synthesized from potato peel waste through hydrothermal treatment at 300°C for 9 hours. The CDs were characterized using X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, UV–Vis spectroscopy, fluorescence spectroscopy, and scanning electron microscopy. The nanoparticles had an average size of approximately 5.4 nm, exhibited excitation-dependent blue fluorescence, and achieved a quantum yield of 16.02%. Latent fingerprints were naturally deposited by four consenting donors on brass cartridge cases from AK-47 and 9 mm Browning ammunition, producing 160 fired samples under contamination-controlled conditions. Under 365 nm ultraviolet illumination, the CDs produced fluorescence and clear ridge visualization on both unfired and fired cartridge cases. Compared with commercial black powder, fluorescent powder, and cyanoacrylate fuming, the CDs demonstrated better contrast, ridge clarity, and detection performance, particularly on fired cartridges. Furthermore, utilizing potato peel waste provides a low-cost, potentially sustainable alternative to conventionally sourced fluorescent fingerprint development materials.