A novel approach of fluorescent porous graphite carbon nitride based silica gel powder for latent fingerprint detection

Porous graphitic carbon nitride (pg-C₃N₄) was synthesized from bulk g-C₃N₄ (Bg-C₃N₄). First, bulk g-C₃N₄ was prepared by a thermal method with poly-condensation of melamine as a precursor. The pg-C₃N₄ was synthesized from Bg-C₃N₄ under ultrasonic treatment in a sulphuric acid medium. Thereafter, pg-C₃N₄ was combined with commercial silica gel (Slg) to give a fluorescent Slg/pg-C₃N₄ powder. These prepared materials were characterized by means of distinctive instrumental techniques consisting of UV–visible spectroscopy (UV–visible), fluorescence spectroscopy (FL), Fourier transform infrared spectroscopy (FT-IR) X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM), transmission electron microscopy (TEM) and live cell microscopy. The fluorescent Slg/pg-C₃N₄ powder was used as a labeling agent for the development of latent fingerprints (LFP) on different surfaces such as glass slides, aluminum foil, aluminum sheets, aluminum rods, a compact disc (CD), iron discs, coins, a tea cup and spoon. The LFP images were additionally captured through the use of ultraviolet radiation at 365 nm due to the fluorescent nature of the Slg/pg-C₃N₄ powder. The LFP images have been also investigated using different commercial powders such as ZnSO₄, TiO₂ and Iodine vapor for comparison with fluorescent Slg/pg-C₃N₄ powder. The Slg/pg-C₃N₄ powder was used to investigate the LFP images submerged in fresh water. Ultimately, the different fluorescent backgrounds of LFP images had been demonstrated using live cell microscopy with pg-C₃N₄ and Bg-C₃N₄. The fluorescent Slg/pg-C₃N₄ powder exhibited potential as a good labeling agent with excessive sensitivity, rapid detection and an eco-friendly nature. This fluorescent Slg/pg-C₃N₄ powder was also used to develop the LFP images under conditions that are likely to simulate real crime scenes to establish whether this material can be used in real forensic investigations.