Surface-specific performance of metal and metal oxide nanoparticles in latent fingerprint visualisation

Latent fingerprint (LFP) visualisation remains a cornerstone method in forensic science, with ongoing developments aimed at enhancing clarity, sensitivity, and substrate compatibility. Due to their ability to tailor surface chemistry and optical properties, nanoparticles present a promising avenue for fingerprint development, especially on various types of surfaces. However, there has been a lack of understanding regarding the comparative behaviour of nanoparticles across different substrates. This review aims to address this gap by critically comparing the surface-specific performance of metal and metal oxide nanoparticles. In which we consider common nanoparticles for LFP development, such as Gold, Silver, silica, zinc oxide, Titanium dioxide, iron oxide, Copper oxide, and Aluminium oxide. Our review examines how various nanoparticles influence fingerprint residue on porous and non-porous surfaces and assesses their effectiveness in terms of clarity, durability using these nanoparticles. Our key finding of comparative analysis highlights that gold nanoparticles yield promising outcomes even on historically challenging porous substrates due to their affinity for sweat and amino acids. Conversely, zinc oxide and titanium dioxide exhibit superior fluorescence-based contrast on non-porous surfaces such as glass and plastics, as well as some porous surfaces. The rest of the nanoparticles were able to achieve their success on porous and non-porous surfaces with some limitations. We also outline diverse methods employed by various researchers, including dusting, brushing, spraying, and fluorescence imaging, while emphasising the role of substrate texture and the functionalization of nanoparticles. The review provides insights using comparative tables on selecting effective nanoparticle-based methods for specific forensic contexts to achieve more stable and universal fingerprint recovery in criminal investigations.