Browsing by Author "P.j, A."

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    Dual emissive water-based flexo ink from tapioca-derived carbon dots for anti-counterfeiting applications
    (Elsevier B.V., 2022) Ullal, N.; Lewis, P.M.; Dhanya, D.; Kulkarni, S.D.; P.j, A.; K, U.B.
    Counterfeiting of high-value items is a challenging menace worldwide, and luminescent nanoparticles-based security inks have promising applications while addressing this global issue. As Carbon dots (CDs) show attractive functional properties, hydrophilic CDs were prepared through hydrothermal approach from tapioca starch as an eco-friendly precursor. CDs with bluish-green fluorescence emission under 365 nm UV light illumination was obtained using column chromatography technique. TCSPC studies indicated the presence of blue and green emitters with average lifetimes of 1.12 and 1.61 ns, respectively. The graphitic and polycrystalline nature of CDs (~9 nm) with negatively charged surface groups was confirmed through ATR-IR, XPS, RS, XRD, SAED, DLS and TEM. An eco-friendly water-based security ink for flexography printing was formulated, and the influence of the ink components on the fluorescence of CDs were studied. The prints on UV dull paper displayed good abrasion resistance, densitometry and colorimetric values. The letters written using the invisible ink exhibited good security features including excellent covertness under daylight, and a bluish-green emission under 365 nm UV light. Moreover, a yellow emission was perceived using a yellow-orange pass filter under the same light source. The surface morphology and electrical property investigations suggested the use of flexo-ink in flexible printed electronics for anti-counterfeiting. These results propose that Tapioca-derived CDs can enable unique optical features in its eco-friendly ink formulation to demonstrate promising security applications. © 2022 Elsevier B.V.
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    Fluorene-vanillin hybrid: A multifunctional fluorophore for latent fingerprint detection and sustainable offset security ink development
    (Elsevier B.V., 2025) K Jain, R.; P.j, A.; Dhanya, D.; Bhagavath, P.; Vatti, A.K.; Mahadeva Prasad, M.P.; K, U.B.; Alex, A.
    Fluorophores play a pivotal role in forensic science and anticounterfeit applications due to their unique and distinct emission features, which enable visualization and authentication. In the pursuit for advanced fluorescent pigments, ortho vanillin-fluorene Schiff base (OAF) with bright orange fluorescence was synthesized using a cost-effective, simple, and one-step method. This fluorophore was highly effective in developing latent fingerprints (LFPs), enabling visualization of level 1–3 features on nonporous glass and semi-porous leather under 365 nm UV light. The interaction between glycine in the fingerprint residue on glass substrate and OAF was analyzed through computational studies and further validated using ATR-FTIR analysis. The FESEM images of the latent prints revealed detailed surface morphology and particle distribution on the ridges of the fingermarks. Further, fluorescent images of LFPs were successfully developed on sticky paint, moist glass, multicolored compact disc, and uneven leaf surface, demonstrating the material's versatility on challenging substrates. Moreover, the powder dusting of composite powder of OAF and JUP-AS120, a commercially available pigment enabled enhanced LFP visualization on glass under both 365 and 980 nm light sources for better contrast and minimal background fluorescence, while minimising degradation of fingerprint residues over time. In addition, an OAF spray was formulated using nitrocellulose resin, ethyl acetate and carbitol for broader forensic application, which facilitated LFP visualization down to fine minutiae details on porous, semi-porous and non-porous substrates. Furthermore, to address the growing rates of counterfeited products/banknotes/security documents, an ecofriendly composite security ink was formulated using OAF and JUP-AS120 to obtain offset prints with excellent resistance to photobleaching and scuffing on paper substrate. The ink film exhibited multilevel authentication features: orange fluorescence under a 365 nm light source, and green and red emissions without and with a 610 nm band pass filter, respectively under 980 nm laser source, enhancing security and making forgery more challenging. Additionally, biocompatible OAF can be incorporated in ink pads to offer a dual layer of validation for fingerprints on security documents: optical authentication by leveraging the ink's fluorescence properties and biometric recognition through fingerprint patterns. © 2025 The Author(s)
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    Ink formulations using Eu3+ doped strontium aluminates for security printing
    (Elsevier B.V., 2025) Ullal, N.; Sahoo, B.; Dhanya, D.; Kulkarni, S.D.; Bhat K, U.; P.j, A.; Rao, A.
    Counterfeiting is a widespread menace that affects multiple sectors of society, which is increasing due to technological advancements and growing globalization of trade. It undermines economic growth, endangers public safety, damages brand integrity, and facilitates criminal activities. The present study focuses on the synthesis of thermally stable europium (Eu3+) doped orthorhombic Sr4All4O25 (SAO) system by solid state method for use as a colorant in the formulation of viz based and polyvinyl alcohol (PVA) based screen inks. The steady state spectrum of Eu3+ doped SAO depicts the charge transfer taking place between host (O2-) and half-filled f-orbital of Eu3+ ion. Mono-exponential decay with lifetime value recorded in milliseconds indicates substitution of single Sr host lattice. The screen prints obtained on UV dull paper using PVA based ink with Eu3+ doped SAO as pigment displayed better photostability and abrasion resistance. Both Viz and PVA based formulations could serve as invisible inks for security printing and information storage applications. The prints produced using the viz-based and PVA-based formulations appeared fluorescent blue under UV illumination, while they exhibited red and green fluorescence, respectively, when viewed through long-pass filters. A user familiar with these features can easily authenticate the prints, whereas replicating them is challenging for counterfeiters. © 2025 The Authors