Browsing by Author "Sahoo, B."

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5,10,15,20-Tetrakis(p-tolyl)porphyrin derived carbon dots as colorant in flexo and screen inks with multi-level covert features for security printing
(Elsevier B.V., 2024) Ullal, N.; Sahoo, B.; Dhanya, D.; Kulkarni, S.D.; Sinha, R.K.; Anand, P.J.; Udaya, B.K.
Fluorescent inks with covert security features, which make it difficult for forgers to replicate, are highly sought after among the array of anti-counterfeit technologies. The present study focuses on the synthesis of Carbon dots (CDs) from 5,10,15,20-tetrakis(p-tolyl)porphyrin (TTP) via a solvothermal approach. The prepared CDs exhibit attractive emissive characteristics with an absolute fluorescence quantum yield of 38.85 %. Time-resolved fluorescence studies reveal the multiple exponential decay nature of the emitters, which could be due to the diverse chemical environment on the surface of the CDs. XPS analysis proves oxygen as the major element, along with carbon, sulfur, and nitrogen as minor elements. DFT studies on four optimized structures of CDs along with their respective UV and FT-IR plots are conducted. The theoretically derived photoluminescence plots corresponding to the 25-30th excited states coincide with the experimental emission peak. CDs demonstrate characteristic variations in fluorescence in the presence of water, attributed to ?-? stacking induced aggregation. Aggregate formation is also influenced by pH changes, affecting the surface functional groups in proximity to the solvent medium. CDs are used as colorants in the fabrication of both flexo and screen inks. Flexo ink retains the fluorescence features of the CDs, while screen ink offers multilevel security features. Exposing UV-dull paper to 365 nm UV light allows the ink inscribed letters to appear fluorescent blue, whereas the use of UV/green optical filters facilitates the visualization of green/yellow emissions. The introduction of multilevel features makes the duplication of the print difficult, protecting the integrity of the product and could be used for real-life applications. © 2024 The Author(s)
Cryogenic machining induced corrosion resistance of magnesium alloy AZ91
(Elsevier B.V., 2025) Marakini, V.; P, C.; P, S.P.; Achar, B.P.; Sahoo, B.; Bhat K, U.
Magnesium (Mg) alloys are popular in the aerospace and automotive sector owing to their light-weight aspects. Amongst various Mg alloys, AZ91 alloy has been trending and needs to be completely explored. The corrosion resistance of AZ91 alloy has always been a question, hence needs further investigation. The impact of face milling operations under cryogenic conditions on the corrosion properties of AZ91 alloy is studied in the current work. Using electrochemical polarization testing technique with a 3.5 % NaCl solution, the optimal surface finish of the alloy produced by cryogenic assisted face milling has been contrasted with dry milling. The polarization method compares both specimens after testing them for 0.5 h. Cryogenic machining considerably minimized the roughness by upto 28 % with values ranging between 0.0525 µm and 0.1169 µm when compared to the 0.1259 µm and 0.0691 µm from dry condition. The comparatively low roughness surface from cryogenic condition demonstrated a relatively low corrosion rate (1.1992 mm/year in cryogenic; 1.2891 mm/year in dry), indicating that the corrosion rates are directly related to the surface roughness. The superior corrosion resistance of the cryogenic milled surface over the dry milled surface was supported by the polarization curves. Additionally, the elemental analysis test on the surfaces after the polarization test revealed that the cryogenic milled surface had less oxygen (44.28 wt% and 7.29 wt%) than the dry milled surface (47.13 wt% and 10.01 wt%), proving the superior corrosion resistance of cryogenic milled surface. © 2025 The Authors
Cumulative effect of FexN phases, roughness parameters, and asperity geometry on the anti-wear properties of low-temperature plasma nitrided Ti-Nb stabilized IF steel
(Elsevier Ltd, 2025) Sahoo, B.; Bhat, K.U.
Plasma-driven surface modification techniques like plasma nitriding (PN) are trending, especially for steel products. It is advantageous due to the higher order of process control and superior quality of property enhancement of the surface. This technique often employs a high processing temperature, which is one of its metallurgical and economical limitations. One of the renowned solutions is the implementation of lower processing temperatures. The current work is based on the low-temperature plasma nitriding of Ti-Nb stabilized interstitial-free steel at different processing temperatures ranging from 400 ºC to 500 ºC. The role of FexN phases, surface roughness parameters, and asperities geometry are thoroughly studied with respect to the anti-wear properties of the surface. The formation of ??-Fe4N and ?-Fe2–3N are detected in the XRD plot, whereas ??-Fe16N2 is confirmed in microscopy. The sample treated at 450 ºC presents the best anti-wear properties compared to other samples, primarily due to the presence of prominent ?-Fe2–3N phase and blunt surface asperities. A maximum reduction in wear volume of about 3 times the base value is recorded in the wear test. The microscopic and elemental analyses are conducted on the wear scars, wear debris, and counter-body worn-out surfaces to study the wear mechanism comprehensively. The work tries to illustrate the wear mechanisms schematically to understand the conceptual grounds associated with such theories. The spectrometric analysis in the depth direction is also performed, and it detects the trace of nitrogen up to about 7 µm depth for 500 ºC nitriding conditions. © 2025
Effect of fiber aspect ratio and orientation on the thermal insulation property of short palm leaf fiber reinforced epoxy composite
(Elsevier B.V., 2025) Sahoo, B.; Nanda, B.P.
The evolution of research ensues new ideologies and methodologies, of which computational methods have been the most sought-after. Most of these computational techniques are based on finite element analysis (FEA). FEA is a cost-effective and time-reliable method for investigating complex problems. The present article uses the ANSYS APDL package to simulate the thermal insulation behavior of palm fiber reinforced composites w.r.t fiber aspect ratio and fiber orientation. For this, a cubical model is developed with cylindrical fibers of different aspect ratios and orientations inside it. It is found that the aspect ratio is inversely proportional to the insulation performance, and the horizontal orientation of fiber performs superiorly than the vertical orientation. The experimental data is also collected for different fiber loading (3.5, 5.5, 7.9, 9.3, and 19.2 vol%) conditions to validate the FEA model. It is observed that the bubble formation and their size and distribution during the composite fabrication are crucial for comparing the experimental and FEA results. © 2025 The Authors
Elevated-Temperature Tribological Study of Interstitial-Free Steel Subjected to Shot Peening
(Springer, 2025) Sahoo, B.; Bhat, K.U.
The tribological behavior of steels at an elevated temperature plays a vital role in manufacturing processes like rolling, stamping, drawing, deep drawing, etc., where a prominent metal-to-metal contact demands a good wear resistance of the surface. The current investigation is based on improving the tribological behavior of interstitial-free steel by subjecting it to shot peening. The wear test was conducted at four different temperatures: 25, 100, 200, and 400 °C. The shot peening was done in two sets: conventionally shot peening and severe shot peening (SSP). The profile of the wear scar was analyzed in a profilometer, confirming the superiority of the SSPed sample in terms of smaller wear scar and lesser wear rate. Considering the temperature effects, the increase in wear resistance was more prominent at 400 °C due to the trace of thick oxide layers countering the ultrafine, fine oxide layers in the 200 and 100 °C wear conditions. The presence of protective ?-Fe2O3 layers and lubricative Fe3O4 layers was advantageous in the tribological aspect, contributing to the formation of a thinner wear scar and lower wear rate. A prominent trace of counter body material was also found in the debris generated at 400 °C wear condition. © ASM International 2024.
Enhancement of Microstructural, Mechanical, and Tribological Properties of AA5083 Alloy via Multi-axial Forging
(Springer, 2025) Aravindh, G.; Sahoo, B.; Kumar, G.V.P.; Udaya Bhat, K.
The present study investigates the influence of multi-axial forging (MAF) on the microstructure, mechanical, and wear properties of the AA5083 alloy. After solution treatment, the alloy was subjected to three MAF cycles at room temperature with a strain of 0.63 per cycle. The evolution of the microstructure was analyzed using optical microscopy, field emission gun scanning electron microscopy, and x-ray diffraction. Mechanical properties were evaluated through tensile testing, and Vicker’s micro-hardness and wear behavior of the alloys were investigated using reciprocating wear tests. The results demonstrated significant improvement in properties after the third MAF cycle, forming 8.3 ?m wide shear bands and a refined grain structure. The alloy achieved maximum hardness (130 HV), tensile strength (334 MPa), and elongation to failure (8.01%), along with a reduced strain-hardening exponent (0.27). Wear resistance showed marked enhancement, with wear volume reductions of 36%, 49%, and 21% under 1, 2, and 4 N loads, respectively. Similarly, wear rates decreased by 64%, 49%, and 15% under the same loads. These findings emphasize the MAF process's effectiveness in enhancing the mechanical and wear properties of AA5083 alloy, indicating its potential for advanced material processing techniques. © ASM International 2025.
Influence of Samarium (Sm) Addition on Mechanical and Tribological Performance of the Al–Mg Alloy AA5083
(Springer Science and Business Media Deutschland GmbH, 2025) Aravindh, G.; Sahoo, B.; Kumar, G.V.P.; Udaya Bhat, K.
Using rare earth elements as minor additives in aluminum alloys has become a promising strategy for enhancing their properties. This study specifically investigates the effects of introducing samarium (Sm) as a minor addition to the Al–Mg alloy AA5083 and analyzes the resulting changes after casting and subsequent solution treatment. The solution treatment process involved heating the alloy to 475 °C for 12 h, followed by rapid cooling in water. Various assessments, including compression testing, differential scanning calorimetry (DSC) analysis, and wear testing, were performed to evaluate the alterations of mechanical, thermal, and tribological characteristics. The results indicate that adding Sm significantly improves the mechanical strength, thermal stability, and wear resistance of the AA5083 alloy. Wear properties demonstrate that the AA5083 alloy with 1 wt.% Sm exhibited superior performance for both as-cast and solution-treated alloys compared to other alloys. These enhancements highlight the potential of incorporating rare earth microadditions to enhance the performance characteristics of aluminum alloys for a wide range of industrial applications. © American Foundry Society 2024.
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
Investigation of column purified dye derived carbon nanomaterials for security printing and supercapacitor applications
(Elsevier B.V., 2024) Mehta, R.; Ullal, N.; Sahoo, B.; Dhanya, D.; Kulkarni, S.D.; Sudhakar, Y.N.; Abdul Salam, A.A.; K, U.B.; Anand, P.J.
Literature evidence reveals versatile applications of carbon dots (CDs), but generally mixtures of various types of carbon nanomaterials, molecular intermediates as well as side products are obtained upon hydrothermal treatment of the precursor material. This demands isolation of pure components and their complete characterization before these nano carbonaceous materials are chosen for suitable applications. In the present study, perylenetetracarboxylic dianhydride (PTCDA) is subjected to hydrothermal treatment and the mother liquor obtained is separated using column chromatography technique using dichloromethane-methanol solvent system to isolate fractions of various fluorescent carbonaceous nanostructures. The TEM imaging of nano carbonaceous particles of all five fractions indicated that the first and third fractions were composed of nanoribbons, while the latter two fractions largely contained quasi-spherical nanoparticles of both lesser (carbon quantum dots) and greater (carbon nanodots) than 10 nm dimensions. The XPS results of all the fractions suggested separation based on polarity difference. The ID/IG ratios obtained from Raman spectra implied the presence of several defects on the CDs. The time resolved fluorescence spectra of third, fourth and fifth fractions revealed mono-exponential decay of fluorophores with excitation independent average lifetime values. The fifth fraction exhibited good biocompatibility and the highest absolute fluorescence quantum yield of 58.47 % among all the isolated samples. As these CDs displayed a remarkable rise in the quantum yield to 88.60 % when dispersed in water, a water-based flexo-ink was formulated. The photostable pale yellow flexo print proofs obtained on UV dull paper exhibited a green fluorescence under 365 nm illumination, whereas a yellow glow when shined with blue light, which can serve as an authentication feature for security documents and currency notes. Moreover, as the third fraction constitutes mainly of carbon nanoribbons (CNRs), an optimized polymer electrolyte was prepared along with sodium alginate (SA), and MgCl2 to understand their potential use in energy storage application. A supercapacitor was fabricated and tested for its electrochemical performance such as cyclic voltammtery (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD). An enhanced current window was observed in the CV of SA/CNRs compared to pure SA and SA/CNRs/Mg films, which indicated a structural interaction of CNRs with SA. The conductivity of SA/CNRs/Mg was lesser than SA/CNRs in EIS studies due to the presence of Mg ions, while pure SA showed lesser conductivity. The dual ionic interaction of Na and Mg along with enhanced structural stability due to doped CNRs favors its convenient supercapacitor application. The fabricated eco-friendly supercapacitor showed a specific capacitance of 84 F/g. The GCD of the device displayed pseudocapacitance behaviour and was quite stable for 2000 cycles with coulombic efficiency of 96 %. © 2024 The Author(s)
Microstructural Features Intimated in Automotive Grade IF Steel Subjected to Conventional and Severe Shot Peening
(Springer, 2024) Sahoo, B.; Udaya Bhat, K.
A significant amount of interstitial-free or IF steel is used to manufacture automotive body parts due to its high ductility, high formability, and low yield strength. But, the major drawback of this steel is the lower surface hardness. The current investigation intended to enhance the surface hardness by employing shot peening at different coverages. The work also studied the microstructural features intimated after the treatment and its effect on the surface hardness. The optical and transmission electron microscopy (TEM) results showed a prominent grain refinement and dislocation hardening, which improved the micro-hardness to 2.5 times. Tri-junctions, sub-grains, twins, nanocrystalline regions, and several dislocation-induced microstructural features, like dislocation bands, dislocation forests, dislocation walls, dislocation cell structure, etc., were detected in the samples after peening. These features bear a beneficial impact on the surface hardness of the substrate. A spatial filter (Sobel filter) was used to refine the image and detect the presence of NbC precipitates near the grain boundary. Using Gatan DigitalMicrograph software, the thermal imaging technique effectively identified thinner grain boundaries near the segregation zone. © ASM International 2024.
Microstructural, electrochemical and immersion based corrosion analysis in milling induced magnesium alloy AZ91
(Russian Association of Corrosion Engineers, 2024) Marakini, V.; Pai, S.; Achar, B.; Sahoo, B.; Bhat K, U.; Devadiga, R.; Rao, S.; Swamy, M.; Mesta, R.
Present work discusses the effect of face milling operations on the corrosion characteristics of AZ91 alloy. A full factorial L27 design of experiment is prepared and face milling is performed to identify the optimal conditions with lowest roughness. The optimal surface of the alloy obtained from face milling has been compared with the slightly polished surface of as-cast alloy using weight loss and electrochemical polarization testing methods using 3.5% NaCl solution. In weight loss method, the alloy surfaces are solution treated for various time intervals ranging from 0.5 to 72 hours, to study the effect of surface finish obtained from face milling in comparison to polishing (as-cast). Whereas, in polarization method, the tests are conducted for only 0.5 hour on both specimens and compared. The corrosion rates are found to be in direct relation to the surface roughness, as the low roughness surface from face milling showed comparatively low corrosion rate. The polarization curves justified the better corrosion resistance of milled surface when compared to polished surface. Further, FESEM micrograph comparison between the before and after polarization test surfaces showed the severity of corrosion attack in both tested surfaces. Furthermore, the elemental analysis using EDAX test on the before and after polarization test surfaces showed the presence of less oxygen in the milled surface compared to polished surface, which established the better corrosion resistance of milled surfaces which has low surface roughness. © 2024, Russian Association of Corrosion Engineers. All rights reserved.
Pyrene carbaldehyde derived carbon dots for detecting water in alcohol and security printing
(Elsevier B.V., 2024) Ullal, N.; Sahoo, B.; Dhanya, D.; Kulkarni, S.D.; Bhat K, U.; Anand
This study focuses on preparing Carbon dots (CDs) from Pyrene-1-carbaldehyde (PCA) using a solvothermal method and further purification using column chromatography. The aggregation-induced emission (AIE) of CDs was systematically investigated in a THF/water medium. The CDs showed red shifts in their photoluminescence (PL) spectra upon increase in water content. Scanning electron microscopic (SEM) images revealed the formation of aggregates, while X-ray diffraction (XRD) confirmed that the d-spacing values remains unchanged. The NMR spectrum of the CDs displayed peaks corresponding to aromatic carbon, which disappeared upon addition of water due to ?-? stacking, indicating aggregate formation. Based on the aggregation-induced fluorescence emission mechanism, detection of water content in alcohol is demonstrated. Moreover, the synthesized CDs were used as fluorescent colorant in screen inks along with polyvinyl alcohol (PVA) and hydroxyethyl cellulose (HEC) as binders. The print proofs obtained on UV-dull paper using PVA-based screen ink exhibited fluorescence emission at longer wavelengths and showcased desirable photostability under prolonged UV exposure compared to the prints obtained using HEC-based ink. Moreover, though the PVA based print appeared blue or cyan fluorescent, the actual yellow emissions from the CDs can be visualised using UV block filter. Such features, masked to the forger, but known to the user can be utilised in checking the authenticity of the print. © 2024 The Authors
Scratch and wear resistance of interstitial-free steel subjected to severe shot peening
(SAGE Publications Inc., 2024) Sahoo, B.; Bhat K, U.; Rao, M.
Surface integrity in terms of scratch and wear resistance is the major concern of any engineering component, which is attributed to most of the surface damages. A popular way of improving such behaviours is the mechanical treatment of the surface. The current investigation studied the improvement of scratch and wear properties by performing shot peening on the Ti–Nb stabilised interstitial free steel, a popular choice in automotive industries. The samples were shot-peened at different coverages. It was found that the shot-peened samples showed a superior scratch and wear behaviour as compared to as-received samples. The scratch hardness was improved by 2.4 times, the wear volume was decreased by 59.6%, and the wear rate was minimal for the 2000% peened sample. © Institute of Materials, Minerals and Mining 2024.
Secured IoT device management in cloud-fog environment using blockchain
(CRC Press, 2021) Biswal, A.K.; Addya, S.K.; Sahoo, B.; Turuk, A.K.
[No abstract available]
Synergistic investigation on Fe[sbnd]N phases and gradient microstructure supported anti-indentation and anti-scratch performance of low-temperature plasma ion nitrided Ti[sbnd]Nb stabilized IF steel
(Elsevier B.V., 2025) Sahoo, B.; Udaya Bhat, K.
Plasma ion nitriding (PIN) is a remarkable surface modification process that utilizes a thermochemical environment to treat the substrate by diffusion-induced phenomena, allowing it to modify complex-shaped objects, especially steel components. However, the foremost shortcoming of PIN is the higher processing cost, which can be minimized by reducing the nitriding temperature. This leads to a prominent variation in the sample's microstructure, often resulting in a gradient microstructure in the depth direction, which can be beneficial for specific industrial applications like scratch resistance, abrasion resistance, etc. The current investigation performs an extensive study to extrapolate the gradient microstructure-induced indentation and scratch resistance of low-temperature PINed (400 °C to 500 °C) interstitial-free steel through microscopy, diffractometry, spectroscopy, microhardness test, indentation test, and scratch test (constant and progressive loading). The transmission electron microscopy and scanning electron microscopy findings suggested a clear trace of gradient microstructure containing various Iron nitride phases (?-Fe2-3N, ?'-Fe4N, and ??-Fe16N2), size and distribution of which affect the scratch resistance. The sample treated at 450 °C shows the best result, with an overall improvement in scratch hardness of 3.2 times the base value. The coefficient of friction, track depth, traction force variation, etc., are also studied and correlated with spectroscopy and microscopy findings. © 2025 Elsevier B.V.
Synthesis and characterization of N-doped reduced graphene oxide for the supercapacitor application
(Springer, 2025) Moodakare, R.; Sahoo, B.; Bharadishettar, N.; Rahman, M.R.; Muhiuddin, M.; Udaya Bhat, K.
In this work, N-rGO is synthesized as a material for the electrode of supercapacitors using a single-stage hydrothermal process. Ammonia functions as a nitrogen source and a reducing agent, significantly enhancing its electrochemical properties. X-ray diffractometry (XRD), Raman spectroscopy, field emission gun scanning electron microscopy (FESEM), and FT-IR (Fourier-transform infrared spectroscopy) were employed for characterization of as-prepared N-rGO electrodes. The XRD plot evidences the successful reduction of as-received GO to as-prepared N-rGO. The FESEM micrograph displays the formation of highly porous and multi-layered N-rGO, showcasing significant structural characteristics. The nitrogen atoms are successfully incorporated into the resulting material (N-rGO) and have been verified through EDS and FT-IR spectroscopy studies. The specific capacitance of N-rGO reaches 107 Fg?1 at 0.5 Ag?1 in a 0.5 M H2SO4 aqueous electrolyte solution. The electrodes showed exceptional cyclic performance, maintaining approximately 130% capacitance after 10,000 cycles and delivering steady Coulombic efficiency. The material's porous structure and nitrogen doping create abundant active sites, facilitating electrolyte ion migration and producing exceptional capacitive performance. The electrochemical impedance spectroscopy study revealed that the N-rGO exhibited a distinctive capacitive behavior. The synthesized N-rGO offers excellent potential for an efficient energy storage application due to its simple, cost-effective, and eco-friendly approach. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.
Tailoring the surface characteristics and mechanical behavior of Ti-Nb stabilized IF steel through controlled shot peening coverage
(Elsevier Ltd, 2025) Sahoo, B.; Udaya Bhat, K.; Kumar, D.S.
The rising demand for a qualitative surface opens a new window of research in the domain of mechanical surface treatment, known as severe shot peening, especially in the automotive industry. The effectiveness of this method is usually affiliated with various process parameters, of which peening coverage is the most sought-after. It is anticipated to elevate the surface characteristics by proficiently optimizing the peening coverage. On this ground, the current investigation tries to gather the beneficial effect of peening coverage on the surface properties of Ti-Nb stabilized interstitial-free steel subjected to severe shot peening by considering four different coverages (100 %, 500 %, 1000 %, and 2000 %). The work attempts to interpret the impact of peening coverage on grain refinement and dislocation-induced microstructures at different depths of the as-treated sample. The crossectional microscopy unveiled a prominent grain refinement hardening and dislocation hardening in 2000 % peening coverage up to a depth of 90–120 µm, firmly agreeing with the microhardness depth profile. The optical microscopy identified four zones of deformation (severe deformation, deformation, transition, and undeformed zone) in the sample treated with the highest coverage. The transmission electron microscopy demonstrated the dominance of certain dislocation-derived features like dislocation forest, dislocation cells, tangled dislocations, dislocation bands, nanocrystalline region, stress concentration region, etc., at the deformed zone of the treated samples. Interestingly, the trace of these features was detected at a greater depth for the highest-peened sample than the lowest-peened sample, affirming the beneficial aspect of higher peening coverage. The stored energy and thermal stability assessment in the as-received and as-treated sample was done in the differential scanning calorimeter, revealing the favorable impact of severe peening on the substrate. The surface topographical study in a 3D profilometer also unveils the variation in the surface roughness and functional volume parameters. The present investigation also analyzed the maximum depth and mean density of furrows to verify the severe plastic deformation in the as-treated sample. © 2024
Yellow emissive and high fluorescence quantum yield carbon dots from perylene-3,4,9,10-tetracarboxylic dianhydride for anticounterfeiting applications
(Royal Society of Chemistry, 2024) Ullal, N.; Sahoo, B.; Dhanya, D.; Kulkarni, S.D.; Bhat K, U.; Anand, P.J.
Forged products are widespread in the market and there is an immediate need to counter this growing menace. Anti-counterfeit techniques using fluorescent materials with covert features that appear hidden under daylight and display characteristic fluorescence upon specific source irradiation have gained popularity. Carbon dots (CDs) that can be prepared through facile synthesis from various raw materials are a class of fluorescent materials that provide tremendous opportunities to combat counterfeiting. This work focuses on the fabrication of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) derived CDs via the solvothermal approach and their subsequent purification using column chromatography. The fifth fraction obtained exhibited remarkable yellow emission (λem = 540 nm) with a high fluorescence quantum yield of 53.22% and a lifetime of 4 ns. The CDs appeared quasi-spherical during TEM imaging with an average diameter of 1-3 nm and appeared polycrystalline from the SAED pattern. The XPS and TEM-EDS results suggested carbon as the major element along with oxygen and nitrogen as the other heteroatoms. The water-based ecofriendly ink formulated using the CDs was printed on UV dull paper using the flexography technique. The print-proof paper samples appeared pale pink under daylight and fluorescent yellow upon 365 nm UV illumination. Moreover, the stability of the print was confirmed upon exposure to strong UV radiation cycles and abrasion resistance. Besides, the fluorescence emission remained unaltered even after 5 months of storage under room temperature conditions. The ink was used to print on PVC sheets and FBB boards with good stability against scuffing, suggesting its applicability in the packaging industry. The CDs could also serve as fluorescent markers for identifying post-consumer plastic packaging for a circular economy. © 2024 The Royal Society of Chemistry.