Incense soot derived carbon nanoparticles for latent fingerprint development: detection and characterization via field emission-scanning electron microscopy, FTIR transmittance and Raman scattering

For decades, latent fingerprints have been visualized using diverse physical and chemical techniques. In the past two decades, nanoparticle-based developers have gained prominence. This study highlights carbon nanoparticles from incense (dhoop) soot as an accessible developer for latent prints. Natural latent marks were deposited on porous (e.g., paper, cardboard, ceramic) and non-porous substrates (e.g., glass, steel, aluminum foil, plastic cover, compact disc). Soot generated by igniting incense was applied to the prints, producing clear, high-contrast ridge detail across most tested surfaces. Detection and characterization employed Field Emission–Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) spectroscopy, and Raman spectroscopy. FE-SEM at 10.00 kV revealed spherical nanoparticles of ~ 50–100 nm. FTIR showed a C–H stretch near 2927 cm⁻¹, O–H around 3436 cm⁻¹, and a weak C=C band at ~ 1630 cm⁻¹. Raman spectra of developed fingermarks exhibited peaks at ~ 1063.28, 1339.45, and 1586.64 cm⁻¹; the incense sample showed peaks at ~ 1077.74, 13 33.62, 1344.41, 1582.63, and 1588.04 cm⁻¹. These signatures confirm shared carbonaceous functionality, including C–C bonding, and provide molecular-level chemical information. The methodology used is novel and has proved to be effective over other existing methods. The sensitivity and quality of widely available reasonably priced powder may be lacking, which has fueled research into substitutes like nanomaterial powders. Overall, incense-soot nanoparticles offer a low-cost, practical, and effective approach to latent fingerprint development, reinforcing the growing role of nanotechnology in forensic science.