Recently, the role of nanotechnology in forensics has been experiencing a rapid growth.
In fact, forensic is a highly skilled, technical and professional discipline with academic research behind with progresses basically driven by achievements in analytical techniques.
Vahid Javan Kouzegaran
Analytical Chemist (Ph.D.) / Nanografi Nano Technology
The analysis of DNA is considered the most common area and nanotechnology has provided promising contributions to developments in the scientific latent fingerprints.
An overview on Latent Fingerprint
Technically, latent fingerprints is referred as deposits left by a combination of exertions from a series of glands in the skin known to be sebaceous glands and sweating which are basically invisible and require the application of some optical techniques and development including some powders to reveal the print. The capability of fingerprints in identifying individuals was demonstrated a long time ago. and carbon black have been employed as latent fingerprint developers for a long time since they are responsive under particular circumstances. However, engineered materials that are particularly designed for fingerprints development haven't been developed so considerably 1.
Advantages of Nanoparticles in Forensic Applications
Specifically a qualified and ideal powder to be applied for fingerprinting is expected to stick the residues left by the finger with characteristic patterns to identify a given crime case. There are some common techniques to achieve a clear identification. Today, nanotechnology is employed to design a series of nanostructured particles to get over this problem. First of all, nanostructured colors are expected to improve insights more coherent and clearer images. According to a study, zinc oxide nanoparticles can not only give better prints and are basically fluorescent but they can also function under wet conditions with that characteristics micron scale powders are not able to do so. In addition to this, calcium selenide nanoparticle with sizes as small as 10 nm and inherent fluorescence under UV light have been able to improve the quality of fingerprints images. A series of nano powders have been designed to analyze and identify a fingerprint using the chemicals to be in contact other materials. For instance, if an individual has been handling explosives or narcotic drugs, the contact residues will appear in the fingerprint for identification. This way of scientific analysis is possible only using this series of nanopowders. The analytical experiments can take an extra stage and the excreted metabolites can be identified because secretions and sweat are the means of removing waste chemicals from the body.
Role of Instrumentation in Forensic Applications
Similar to other branches of nanotechnology, forensics strongly depends on instrumentation among which atomic force microscopy (AFM) has contributed a lot to the growth and progress of this area of science. AFM is a kind of microscope capable of analyzing ink crossing through scanning the surface of documents created by the pattern of pen Strokes and three dimensional morphology of them. Additionally, AFM can provide significant data concerning the alignment of lines and curves formed by the pen ink and the dye. Based on the AFM, it is possible to clarify the ink crossing in order to translate accurate information for forensic investigation. Atomic Force microscopy has contributed a range of other forensically significant applications including blood stain age determination 2.
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Nanomaterials in Forensics
So far, several nanostructured materials have exhibited satisfactory results in forensics including silver nanoparticles, gold nanoparticles (AuNPs) zinc oxide nanoparticles (ZnO-NPs) silica nanoparticles (SiO2-NPs) and CdSe quantum dots.
Inclusion of CdSe quantum dots in porous phosphate petrol structures as a fluorescent nanocomposite and functionalized with amino groups has been reported to be employed for fingerprint detection. This detecting platform has been designed to develop a powder to detect latent fingerprints specifically non-porous surfaces. Further integration of this powder in porous phosphate heterostructures makes it possible to limit the spread of fluorescent nanoparticles through which high qualified fluorescent images can be achieved. Based on this detection platform, fingerprints from distinct non-porous surfaces including mobile phone screen, magnetic band of a credit card and iron tweezers are treated with this powder with the consecutive emission of an orange luminescence observed under the UV light. Extensive image processing such as contrast enhancement with positive matches from a police database has demonstrated the effectiveness of the obtained result compared to non-processed images 3.
In forensics, gold nanoparticles have appeared to play a crucial role in developing latent fingerprints platforms mostly because of their inert nature of high selectivity and sensitivity along with attributes which make the storage of develop fingerprints possible for a long period of time. Regarding the unique properties of gold nanoparticles, they have been applied to improve the visibility of latent fingerprints taking the advantage of multi metal deposition based on sol-gel method that is carried out in two steps. In working with gold nanoparticles, the fingerprint bearing surface is immersed in a solution of gold nanoparticles that are basically stabilized in citrate ion medium with consecutive addition of silver physical developer solution. According to characterization analysis, gold nanoparticles can bind to fingerprint residues and catalyze the precipitation of silver ions to metallic silver. Accordingly, the latent fingerprint silver image is achieved due to the electrostatic interaction between the positively charged fingerprint residue and the negatively charged gold nanoparticles.
Zinc oxide possesses interesting properties namely a wide band gap, capability to facilitate interactions with lipids and proteins in the fingerprint residue at ambient temperatures and high excitation binding energy the process transitions at room temperature. Zinc oxide nanoparticles have been employed in the form of a powder to develop the age latent fingerprints specifically on non-porous surfaces. This way of developing fingerprint has shown a clear ridge detail with fluorescence emission under the UV light. Recently, it has been reported that zinc oxide nanoparticles as big as 2 nm can not only provide coherent and clearer images, based on their structure, their natural fluorescence can function even under wet conditions. Furthermore, other studies have demonstrated that nanostructured zinc oxide can generate high quality fluorescent images of the latent fingerprints when they are illuminated by UV light. Moreover, the combination of zinc oxide nano powder and silicon oxide has turned out to have a remarkable impact on developing the latent fingerprints in distinct nanopowders.
Nanomaterials have a wide range of applications in forensics with gold nanoparticles used for increasing the efficiency of PCR, quality of AFM micrographs and XPS in drug analysis. Gold and silver nanoparticles can also be employed to develop latent fingerprints with practically long shelf life. Furthermore, they can be functionalized in order to identify the secondary properties of an individual. Similar to this, functionalized silica nanoparticles can be used to study the mechanisms of fingerprints development in aqueous solutions. Zinc oxide nano powder has found applications as a capable agent for latent fingerprints development with minimum background staining compared to other available powders.
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1.Pitkethly, M. Nanotechnology and forensics. Mater. Today12, 6 (2009).
2.Prasad, V., Lukose, S., Agarwal, P. & Prasad, L. Role of Nanomaterials for Forensic Investigation and Latent Fingerprinting—A Review. J. Forensic Sci.65, 26–36 (2020).
3.Algarra, M. et al. Fingerprint detection and using intercalated CdSe nanoparticles on non-porous surfaces. Anal. Chim. Acta812, 228–235 (2014).