Application of Nanomaterials for Latent Fingerprint Visualization

Nanomaterials, with dimensions below 100 nm, usually exhibit distinct physical and chemical properties compared with their bulk counterparts due to their small size, high surface area, and quantum confinement effects. A wide range of industries, including electronics, energy storage, healthcare, and forensics, has recently shown significant interest in nanomaterials. In forensic research, nanotechnology has emerged as a revolutionary technique, particularly for enhancing the visibility of latent fingerprints. One of the most significant and prevalent forms of evidence in forensic investigations is latent fingerprints. These prints are composed of natural skin secretions, including perspiration, oils, and other organic materials inadvertently left on a surface. Fingerprints provide unmistakable proof of an individual and can be used to identify them due to their distinctiveness and permanence. Nevertheless, these prints must be improved for vision because they are sometimes invisible to the unaided eye. Conventional detection techniques, including chemical fuming, iodine vapor exposure, and powder dusting, have drawbacks such as low contrast, limited sensitivity, and reliance on the surface. The quality of latent prints can also be lowered by environmental elements, including temperature, humidity, and time. Better and more reliable fingerprint visualization methods are therefore desperately needed to solve these problems.

In this regard, several nanomaterials have shown potential for effective detection of latent fingerprints. Distinct physical, chemical, and optical properties of nanomaterials at the nanoscale level are the origin of this observed advancement. Nanoparticles can be tailored in size, shape, and surface chemistry to meet technological requirements, and they have a very high surface area-to-volume ratio. These characteristics of nanomaterials enable improved interaction with minute residues, such as proteins, lipids, or amino acids, present in latent fingerprints. These nanomaterials can be designed to meet the needs of forensic applications, which require contrast, sensitivity, and selectivity for detecting latent fingerprints. In fingerprint visualization, nanomaterials are superior to conventional powders and chemicals in several ways. Due to their small size, they could pierce fingerprints and disclose minute ridge features. Additionally, the surface chemistry of these nanomaterials can be modified to interact with biological elements found in fingerprint residues. Many nanomaterials exhibit unusual optical properties, such as fluorescence, which can be exploited to produce highly contrasted images when illuminated under unusual lighting conditions. The most attractive category of nanomaterials is undoubtedly that of fluorescent nanoparticles. Strong and stable UV or visible radiation can excite fluorescence from these nanoparticles. Producing images of fingerprint ridge patterns with high clarity, even when on complex or multi-coloured surfaces, is possible with this emission. Magnetic nanoparticles can also be used to develop a fingerprint detection technique that is non-invasive, in that magnetic attraction is first used to gently place the particles onto the ridge deposits without damaging the surface. Functionalized nanomaterials have even been tailored to bind with fingerprint residues in a specified manner. This ensures that the targeted binding enhances contrast with respect to background noise and the longevity of the developed prints. In this context, along with the other mentioned nanomaterials, graphitic carbon nitride (g-C₃N₄), a promising metal-free nanomaterial, has received significant attention due to its multifunctionality and eco-friendly nature for latent fingerprint detection. This material is made up solely of carbon and nitrogen atoms. It forms layered sheets that resemble graphite, but it has a more complex electronic structure based on tri-s-triazine units (heptazine). Hence, nanotechnology is expected to find application in forensic science in this decade.