Latent fingerprint development by using silver nanoparticles and silver nitrate-A comparative study

The beginning of latent fingerprint development on porous surface was first achieved by silver nitrate (AgNO₃ ) method. But the significantly increasing cost has caused forensic experts to look for an alternative means. Silver nitrate (AgNO₃ ) is the main component in the synthesis of metal nanoparticles, namely silver nanoparticles (AgNPs). Owing to its unique property to adhere with fingerprint residue, AgNPs have attracted a great attention in the domain of nano-forensic fingerprinting. This study mainly focuses on the use of lower concentration of silver nitrate through new AgNP development method. The AgNPs were synthesized by wet chemical method with different molar concentrations (0.1, 0.01, and 0.001 M) of silver nitrate, characterized by ultraviolet visible spectrophotometer and high-resolution transmission electron microscope (HR-TEM). The average diameter of AgNPs calculated by HR-TEM was 10.66 ± 1.22 nm at 0.1 M, 12.50 ± 2.64 nm at 0.01 M, and 14.44 ± 2.68 nm at 0.001 M, respectively. A comparative analysis was also carried out to see the quality and stability of fingerprints produced on paper or porous substrate by using AgNO₃ and AgNPs, respectively. During the study, AgNPs were able to develop distinct ridge details and were found to be stable for more than a month. Comparatively, when AgNO₃ was used as the developing agent for the latent fingerprints, only faint ridge patterns were observed which further showed degradation of fingerprint stability within about 20 days. Overall, the current AgNP method showed good visibility and stability by using lower concentration of silver nitrate which can be used in place of conventional AgNO₃ method.