Nanoforensics is an emerging interdisciplinary field that leverages nanotechnology to enhance forensic science practices. It involves the application of nanoscale materials, tools, and techniques to analyse, identify, and interpret trace evidence and other forensic samples. By utilising the unique properties of nanomaterials, nanoforensics aims to improve the accuracy, sensitivity, and efficiency of forensic investigations, enabling the detection of minuscule quantities of evidence and providing valuable insights for solving criminal cases.
Nanotechnology can be implemented in different areas of forensic science:
- Latent fingerprints visualisation
- Drug detection
- DNA quantification
- Explosives detection
- Gunshot residue analysis
- Questioned Documents
- In the estimation of time since death
NANOTECHNOLOGY IN QUESTIONED DOCUMENTS:
The formulation of writing and printing ink includes the addition of nanoparticles. The elemental profile and morphological characterization of the pigments present in writing and printing ink are provided by SEM (Scanning Electron Microscopy) images of the ink at various levels. Self-erasing medium and self-erasing ink have been developed to help maintain the confidentiality and secrecy of security documents.
- SELF-ERASING MEDIUM
Researchers at Northwestern University, led by chemical and biological engineering professor Bartosz Grzybowski, have used gold and silver nanoparticles embedded in a thin, flexible organic gel film to make the new type of self-erasing medium. These are composed of 5 nm-sized gold and silver nanoparticles. When these nanoparticles are exposed to UV light, they group together and change colour. However, these clumps disintegrate and cause the ink to evaporate in visible light. Grzybowski says, “It self erases and there’s no way of tracing it back”.
In 2006, A paper that self destructs in 16 to 24 hours was announced by Xerox. These substances employ photochromic molecules, which change color when exposed to light and alter their internal chemical structure. Usually, these molecules can only flip between two colors, and after a few cycles, they lose the ability to do so.
According to Masahiro Irie, a chemical professor at Tokyo’s Rikkyo University who specialises in photochromic molecules, the idea of using photostimulated reversible aggregation of gold or silver particles for self-erasing images is quite novel and exciting. As he thinks that photochromic molecules might be preferable for real world self-erasing devices, though.
Self-erasing medium can be employed for sharing confidential files, ensuring that the files get self-destructed after a certain period or after being accessed a certain number of times.
People use self-erasing digital diaries or journals for writing persona thoughts that automatically disappear after a specified period.
• SELF-ERASING INK
Water is used to make the self-erasing ink. Instead of a traditional pigment or dye, the ink uses a pH indicator such as o-cresolphthalein (C 22 H 18 O 4 ) as a colorant. It is used therapeutically to assess calcium levels in the human body or to create polyamides. The pH indicator is coloured when the pH is high and colourless when the pH is low. For best readability, the ink is printed at a high pH. Following that, the printed image collects carbon dioxide and water vapours from the air, resulting in the formation of carbonic acid. This decreases the pH of the ink, resulting in colourless printed image. The ink is still on the paper, but it is no longer visible.
Disappearing inks are visible for a short amount of time before becoming invisible again. These are usually based on a chemical reaction between Thymolphthalein and a basic material like sodium hydroxide. In a solution with the base, thymolphthalein, which is ordinarily colourless, turns blue. The pH dips below 10.5 when a base combines with carbon dioxide, and colour fades.
Self-erasing ink can be used as barcodes in military security are printed with highly classified ink. Ink containing gold nanoparticles contained in an alkanethiol is used to create radio frequency identification tags. This further can be employed as a part of anti-counterfeiting measures on documents, tickets, or products. If anyone tries to tamper the ink, it will become evident. It has eco-friendly applications as well, such as temporary plant markings in garden or other environmentally sensitive areas.
• SECURITY TAGS
Fluorescence is now widely recognized as one of the most effective anti-counterfeiting measures. When exposed to UV light, zinc oxide quantum dots (ZnOQds) exhibit excellent fluorescence, making them a contender for anti-counterfeiting printing. The resulting anti-counterfeiting papers are environmentally friendly and resistant to organic dyes. ZnOQds were synthesized in a green way and studied using UV-visible spectroscopy, as well as microscopic studies using transmission electron microscopy (TEM) and crystallography using X-ray diffraction (XRD). It was authorised to form ZnOQds nanocrystals with an average partial size of 7.3 nm. Furthermore, double layer sheets were produced at two ZnOQds loading concentrations, 0.5 and 1 (wt/v), and characterized utilising a topographical surface examination using field emission scanning electron microscopy (FE-SEM) . When compared to single layer paper and polymer film, hybrid sheets were mechanically more stable. Furthermore, aging modeling confirmed hybrid sheets’ great stability. For more than 25 years, the photoluminescence has confirmed the anti-aging properties of hybrid paper. The hybrid sheets also demonstrated a broad spectrum of anti bacterial action.
Security features can be added to documents for various purposes to enhance security and prevent counterfeiting. These tags include holograms, watermarks, or other advanced features in currency, passports, or high-value certificates to deter counterfeiting. In sensitive or legal documents like contracts, diplomas, or government-issued IDs, security tags are used to confirm the authenticity of the document. Also in the publishing and entertainment industries, security tags can be used to protect copyrighted materials like books, scripts or music scores.
• UV and IR IMAGING
When combined with nanotechnology, UV (Ultraviolet) and IR (Infrared) imaging play an important part in nanoforensics document inspection. It allows forensic professionals to do multimodal analysis, offering a complete picture of a document’s qualities and history. UV and IR imaging can be used to validate documents by detecting security features, watermarks, or nanoscale patterns that are difficult to recreate.
In cases involving document fraud, forgery, or the altering of legal papers, these procedures give crucial forensic evidence.
*Ink Characterization:
UV Fluorescence Imaging: Under normal lighting, UV light can show fluorescent features of inks that are not visible. This aids in distinguishing between different ink kinds and detecting changes in documents that have utilized different inks.
Infrared imaging can detect differences in ink composition based on their absorption and reflection of infrared light. This might be handy for detecting changes or additions to text or graphics.
*Revealing Hidden Text and Alterations
UV Imaging: Variations in ink characteristics may become visible under UV lighting, revealing buried or erased text.
IR Imaging: Because different inks or materials have varied reflectance or absorption characteristics in the IR band, infrared imaging can reveal adjustments or additions made with different inks or materials.
*Forensic Photography Enhancement
These strategies can improve the contrast and visibility of specific elements or adjustments in documents, allowing forensic professionals to assess and document evidence more easily.
*Age Assessment
UV and IR imaging can help determine the age of documents by revealing changes in ink properties or degradation over time. This can be critical in establishing the authenticity of historical documents.
• DATING DOCUMENTS
Titanium dioxide (TiO2) nanoparticles, are sensitive to environmental conditions such as light and humidity. Forensic experts can estimate the age of a document or establish if it has been subjected to specific environmental conditions by evaluating the behavior of the nanoparticle within the paper.
TiO2 is an inorganic substance that is stable and non-toxic. TiO2 has been frequently utilized as a white pigment due to its extremely high refractive index. TiO2 particle sizes of roughly 250 nm are ideal for pigment applications. Titanium dioxide must be used as a pigment in the manufacture of high-quality papers. Titanium dioxide gives high-quality papers a desirable brightness and opacity. Papers with titanium dioxide pigment have a high strength and a white, shiny, thin, and smooth appearance.
REFERENCE :
- Prachi Patel, New Type of Disappearing Ink, MIT Technology Review, 2009
- Richa Rohatgi, Femin Dominica, Application of Nanotechnology in Forensic Science, Journal of Forensic Research, Volume 13: 8, 2022
- Alok Pandya, Ritesh K Shukla, New Perspective of Nanotechnology: Role in Preventive Forensic, Egyptian Journal of Forensic Sciences, Article No. 57 (2018)
- Markoff J., “Xerox Seeks Erasable Form of Paper for Copiers,” The New York Times, p. C8 (Nov. 27, 2006)
- With Self-Erasing Ink, Paper Does Not Have to be Disposable, Article by the National Science Foundation in partnership with CEP, Catalyzing Commercialization (Oct. 2020)
- Sonali Kesarwani, ed.al., Nano-Forensics: New Perspective and Extensive Application in Solving Crime, Volume 10, Issue 1, 2021
- Mohamed S. Hasanin, ed.al., Sustainable multifunctional zinc oxide quantum dots-aided double-layers security paper sheets, March 2021.
- Francis Tambo, Dorcas Naa Odarley, A review on the role of emerging revolutionary nanotechnology in forensic investigations, Institute of Forensic Science, Gujarat Forensic Sciences University (29 November 2020)
Kanak Varshney
SAGE University, Bhopal