Counterfeit items continue to be a significant concern in modern society, posing complex challenges with many financial and security implications.
Study: Invisible Thermoplasmonic Indium Tin Oxide Nanoparticle Ink for Anti-counterfeiting Applications. Image Credit: Standret/Shutterstock.com
A new paper has set out to help address this issue by creating a thermoplasmonic transparent nanoparticle ink based on a colloidal suspension of indium tin oxide (ITO) nanoparticles. This nanoparticle ink acts as a novel anti-counterfeiting technique, with more details published in the journal ACS Applied Materials & Interfaces.
Importance of Novel Anti-Counterfeiting Technologies
Due to the rapid advancement of digital technologies, such as digitized cameras, printers, and scanners, counterfeiters can manufacture high-quality reproductions using just their desktop computers. Such unlawful operations not only affect the enterprises who manufacture the items by breaching their rights and causing a loss of profit, but they also represent significant security threats to society at large.
The implementation of novel anti-counterfeiting solutions is critical in preventing these situations. To date, the most prevalent anti-counterfeiting systems rely on tags that, owing to their minimal complexity and repeatability, can be simply replicated. However, recent technological breakthroughs have enabled the development of innovative anti-counterfeiting solutions that are easy to manufacture but difficult to copy.
Recent research suggests that physically unclonable functions (PUFs) be employed in creating security labels, making use of certain natural random fluctuations produced by the production process. Because the PUF system is hard to duplicate, this method can ensure a very high degree of security, making it ideal for anti-counterfeiting applications.
Use of Nanoparticles in Anti-Counterfeiting Technologies
Many anti-counterfeiting methods, including certain PUF-based technologies, use nanoparticles (NPs) due to their distinctive and highly customizable mechanical characteristics, reactivity to various stimuli, and ability to incorporate them into electronics through solution processing.
Nanoparticle-based techniques are more difficult to counterfeit than molecular solutions because their attributes are highly reliant on the synthesis process, structure, and surface chemistry and cannot be readily reverse-engineered.
Thermoplasmonic Nanoparticle Ink: The Future of Anti-Counterfeiting
The utilization of a thermoplasmonic nanoparticle ink capable of interacting with light to show a particular manufactured pattern as a visual readout signal is of significant relevance in anti-counterfeiting applications. Furthermore, plasmonic NPs demonstrate enhanced light absorption when treated at their unique resonance frequency, which is adjustable with size, structure, and chemical compositions.
This new field known as thermoplasmonics has recently been widely used in anti-counterfeiting technology. To this end, plasmonic nanoparticles that create heat upon infrared radiation while remaining transparent to visible light are extremely attractive.
However, a nanoparticle ink made from transparent elements such as silver is not completely transparent under visible light since it may absorb red light as well. A transparent nanoparticle ink is significantly more difficult to recognize and copy in this regard, making it highly suitable for anti-counterfeiting applications.
A Novel Transparent Nanoparticle Ink based on Indium Tin Oxide (ITO)
Heavily modified semiconductors with large free transport concentrations are evolving as promising plasmonic nanomaterials with variable resonance frequencies ranging from visual to far infrared. The most notable is indium tin oxide (ITO), which is naturally transparent to visible light owing to its large band gap.
Moreover, colloidal ITO NP suspensions can be made in very large quantities using simple chemical processes such as organometallic chemical breakdown or the solvothermal approach. ITO NPs have various benefits over standard noble metal plasmonic NPs, including inexpensive cost, little oxidation damage, and good thermal stability.
All of these properties make colloidal dispersions of ITO NPs particularly appealing for creating a unique anti-counterfeiting nanoparticle ink that uses the thermoplasmonic effect caused by infrared light irradiation.
Highlights and Key Developments of the Current Research
In this study, the researchers created a thermoplasmonic translucent nanoparticle ink for anti-counterfeiting applications that exhibits plasmonic resonance in the near-infrared region while remaining transparent in the visible range using a novel tin-doped indium oxide nanoparticle (ITO NP) colloidal suspension.
Inkjet printers can be used to manufacture nanosized transparent sheets with various patterns directly on the targeted substrate, paving the path for systematic low-cost manufacturing of transparent, photothermally active tags.
The researchers created a QR code invisible to the naked eye but plainly apparent in thermal photos when exposed to near-infrared (NIR) light. Because the nanoparticle ink is actually translucent and the thermal scanning is extremely quick (numbers appear/disappear in less than 1 second), this novel process can be highly useful in the manufacturing and decoding of security tags.
Interestingly, instead of NIR beams, the reading may be conducted using regular infrared cameras and low-cost light sources (such as broadband infrared lamps), rendering this anti-counterfeiting system easy to implement for a wide range of applications and situations.
Mazzotta, A. et al. (2022). Invisible Thermoplasmonic Indium Tin Oxide Nanoparticle Ink for Anti-counterfeiting Applications. ACS Applied Materials & Interfaces. Available at: https://pubs.acs.org/doi/10.1021/acsami.2c10864
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