Faculty Publications
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Item Synthesis and characterisation of an ultra-light, hydrophobic and flame-retardant robust lignin-carbon foam for oil-water separation(Elsevier Ltd, 2021) Vannarath, A.; Thalla, A.K.The lignin extracted from Arecanut husk (Areca catechu) was used as an additive in lignin-carbon foam synthesis to enhance oil uptake in oil-water separation. The lignin yield from the arecanut husk increased as the husk fibre size reduced. The extracted lignin and lignin-carbon foam were characterised for morphology, structural, compositional and thermal degradation properties. The synthesised lignin-carbon foam appears to be ultralight (density = 0.0294 g/cm3), excellent hydrophobic (water contact angle was 124°), mesoporous (3D cell-like structure), fire-retardant and thermally stable. The foam showed an excellent sorption capacity for different oils, and the highest sorption was observed for diesel oil (7842.71 mg/g). The optimisation of contact time (30 min), lignin-carbon foam dosage (0.5 g), and initial oil concentration (30 g/L) were done for the diesel oil sorption. The isotherm study and kinetic model evaluation were done for the diesel adsorption on the lignin-carbon foam. The Temkin model was found the best fit for the adsorption isotherm. The adsorption kinetics of the lignin-carbon foam for diesel oil was best described by pseudo-second-order kinetics. The thermodynamic parameters showed that the adsorption was endothermic and spontaneous (standard enthalpy change, ?H° = +4926.46 J/mol and standard entropy change, ?S° = 25.249 J/mol/K). The proposed mechanism depicts that the adsorption primarily influenced hydrogen bonding (H-bonding) and n-? interactions. The enduring adsorption of oil into the lignin-carbon foam within few seconds shows the material oleophilicity and confirms their application prospect in oil spill cleanup. © 2021Item Fabrication of minimal capital-intensive scratch-resistant and hydrophobic tungsten oxide film on stainless steel through spray pyrolysis(John Wiley and Sons Ltd, 2022) Vardhan, R.; Kumar, S.; Mandal, S.In this contribution, a pure and robust tungsten oxide (WO3) film was accomplished on stainless steel (SS) substrate at 400°C through a minimal capital intensive, simplistic spray pyrolysis method by utilizing a precursor comprising tungsten hexachloride and 2-methoxyethanol. Thermal analysis revealed the precursor's thermal decomposition and crystallization at ~230°C and 255°C, respectively. The fabricated polycrystalline (monoclinic crystal structured) film was uniform and dense in nature, exhibiting surface porosity and average surface roughness of 4.7 % and 15.9 nm, respectively. The average grain size and thickness of film were 360 ± 70 nm and ~3.6 μm, respectively. W, O elemental presence with a close atomic ratio of 1:3 on the film's surface was acquired along with 91 % lattice oxygen. Regardless of applied normal load in the range of 5 to 15 N, an increment of ~22 % in scratch hardness was gained in WO3-coated SS compared to uncoated one. Hydrophilic natured WO3 film (water contact angle, WCA, of ~31°) was efficaciously transformed into hydrophobic (WCA, 136°) by chemical modification with octadecyltrichlorosilane to create a self-assembled monolayer on the surface of the film. The hydrophobicity of octadecyltrichlorosilane (OTS)-treated film was found to be preserved even after 100 days. © 2022 John Wiley & Sons, Ltd.Item Biocorrosion Behavior of Epoxy-Based Multilayer Nanocomposite Coatings(Springer Science and Business Media Deutschland GmbH, 2023) Shetty, P.; Arya, S.B.; Shetty K, V.S.Marine structures are prone to biocorrosion, so developing a suitable coating system to combat corrosion is essential. The present work is focused on the development of a multilayered epoxy-based nanocomposite (NC) coating system reinforced with ZnO filler in the first layer coat (NC1), ZnO and Cu2O in the second layer (NC2), and the third layer consisting of a varying percentage of TiO2 with 5 wt%, 10 wt%, and 15 wt% of TiO2 designated as NC3, NC4, and NC5, respectively, as top coat on the bare steel. Brush coating was employed to fabricate the coatings. Surface morphology and mechanical properties, wettability, corrosion, and biocorrosion behavior of the bare steel and coated substrates were examined. Mechanical properties such as linear scratch hardness and posi adhesion test values of the coatings were found to be in the order NC1 < NC2 < NC3 < NC4 < NC5. The NC3-coating system comprising three layers of coating reinforced with 5 wt% TiO2 imparting hydrophobicity offered maximum resistance to microbial adhesion with 93% and 91% reduction in corrosion rate than the bare metal in natural and artificial seawater, respectively, after the 7th day of immersion. The bacterial and fungal cell counts in the biofilm after the 7th day of immersion were reduced by four and three orders of magnitude, respectively, in the nanocomposite against the bare substrate providing good biofouling resistance. NC3 coating also prevented the release of metal ions into the seawater and acted as a barrier for the leaching of metals from the coating underneath, thus, proving to be safe for the marine environment. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Development of stable and functional encapsulated chrysin using casein–polysaccharide complexes for food applications(John Wiley and Sons Inc, 2023) Parappa, K.; Krishnapura, P.R.; Iyyaswami, R.; Belur, P.D.Chrysin is a hydrophobic flavonoid with multiple health benefits. The various applications of chrysin are challenged by its poor solubility, instability and loss of bioactivity. Casein–chrysin complex and casein–polysaccharide–chrysin complexes have developed to overcome these limitations. Very high encapsulation efficiency of 98.23 ± 0.22% was achieved with casein–inulin–chrysin complex. The chrysin was able to form a stable casein–polysaccharide–chrysin complex suspension with a hydrodynamic diameter of 382.3 nm, zeta potential value of −12.3 mV and a Polydispersity Index (PDI) of 27.7. The antioxidant activity of chrysin increased about threefold after encapsulation. The release of chrysin from its encapsulated complexes to different buffers in the pH range of 3 to 10 was studied at 1:10 ratio. At the end of 48 h, only 6%–8% of chrysin was released in the pH range 3–4, 33%–58% at pH 5–9 and 62% at pH 10. The chrysin encapsulated in casein–inulin–chrysin complex was able to overcome the rapid release of chrysin from the casein–chrysin complex. The results indicate the successful development of a stable encapsulated chrysin complex which can overcome the various limitations of chrysin in its potential applications. © 2023 Institute of Food, Science and Technology (IFSTTF).Item Anti-biofouling evaluation of vacuum-assisted hydrophobic ytterbium oxide (Yb2O3) coating on stainless steel by facile spray combustion(Springer, 2024) Karle, S.S.; Kailasam, K.; Vardhan, R.V.; Praveen, L.L.; Gautam, V.; Mandal, S.Despite the development of numerous coating techniques and materials, today’s anti-biofouling applications require coatings that are facile and mechanically robust in nature. Studies on the hydrophobicity of rare-earth oxides have risen due to their unusual chemical properties; ytterbium oxide is one such oxide substance. In this study, spray combustion was used to create a hydrophobic coating of ytterbium oxide (Yb2O3) on a stainless steel (SS) substrate, which was then vacuum-treated. GI-XRD analysis confirmed the sesquioxide cubic crystalline structure of Yb2O3. FESEM images displayed an underneath wavy morphological coating with discrete particles on the surface. The thickness and roughness were ~12 and ~0.17 µm, respectively. When 5 and 10 N loads were applied, the coating showed better scratch hardness than uncoated SS. Water contact angle (WCA) <10° indicated superhydrophilicity in the fabricated coating. After vacuum treatment, it became hydrophobic, and the WCA was 128°; because of the increment in the relative area fraction of the C–H bond. The proportion of area covered by blue–green algae (Phormidium sp.) on vacuum-treated Yb2O3 coating was only 3% compared to uncoated SS samples, 80%. © Indian Academy of Sciences 2024.Item Fabrication and Characterization of Silicon Dioxide-Reinforced Polydimethylsiloxane Composite Coating for Corrosion Protection of Galvanized Iron(SAE International, 2024) Kumar, P.; Ramesh, M.R.; Doddamani, M.The present work highlights the significance of nanocomposite coatings for their ease of processing and applicability in combating corrosion. Ongoing research is dedicated to the development of an effective nanocomposite hydrophobic coating. A hydrophobic nanocomposite coating was deposited on galvanized iron (GI) using a sol-gel route with polymethylsiloxane (PDMS) reinforced with nano-SiO2. Surface morphology and chemical composition analysis, conducted with scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR), revealed the coating's structural and compositional attributes. The resulting hydrophobic coating exhibits a water contact angle (WCA) of 104.1°, indicating a 30.45% increase compared to bare GI. Subsequent to these characterizations, the adhesion of the coated GI, rated as 4B per ASTM D3359, is followed by commendable resistance to corrosion, as evidenced by electrochemical tests. The corrosion rate for the coated GI sheet is notably low, at 62.78 × 10-3 mpy, underscoring its anti-corrosive efficacy. © 2024 SAE International.Item Exploring the protection of spray-pyrolysed tungsten oxide hydrophobic coating on stainless steel in a marine environment(Springer, 2024) Gautam, V.; Praveen, L.L.; Vardhan, R.V.; Mandal, S.Tremendous potential in the field of anti-biofouling coatings to prevent stainless steel (SS)-based underwater pipelines, sea vessels and other marine structures have been recognized to protect from biofouling, which is often initiated by algae attachment over the surface. In this work, hydrophobicity in spray-pyrolysed tungsten oxide (TO) coating on SS-316 substrate has been reported for the first time, via post-processing treatment using octadecyltrimethoxysilane (ODTMS) to induce self-assembled monolayer (SAM). Initially, structural and vibrational characteristics of ODTMS and ODTMS-treated TO (OTO) coating on SS were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. OTO-coating depicted a water contact angle (WCA) of 121°, revealing its hydrophobic nature, with further affirmation from X-ray photoelectron spectroscopy (XPS). Durability of the TO-coating was explored using the scratch hardness (Hs) test at different loading conditions (5, 10 and 15 N). Biofouling study was conducted by culturing blue-green algae (BGA, Phormidium sp.) in an in-house laboratory setup for 40 days, using seawater (collected from the Arabian Sea, Karnataka). The SS, TO- and OTO-coatings were immersed for 14 days in a controlled sea-water environment in the laboratory with the presence of BGA. A comparative study on the areal-algae attachment was keenly analysed over SS-, TO- and OTO-coatings. This work can be projected as a promising application providing multi-dimensional solutions in creating scratch-resistant and anti-biofouling coatings on SS in the shipbuilding industry. © Indian Academy of Sciences 2024.Item Dopant-free hydrophobic fluorene-based hole transport materials: impact of methoxy-substituted triphenylamine and carbazole peripheral groups on the performance of perovskite solar cells(Royal Society of Chemistry, 2025) Bhat, V.G.; Keremane, K.S.; Subramanya, K.S.; Archana, S.; Hegde, A.; Asuo, I.M.; Poudel, B.; Udayakumar, U.Hole-transporting materials (HTMs) are crucial for charge separation in perovskite solar cells (PVSCs). Besides possessing suitable HOMO/LUMO energies, HTMs should ideally be hydrophobic to protect the perovskites from atmospheric moisture to enhance device stability. We designed two fluorene-core D-?-D-type organic HTMs (V1 and V2), consisting of either 4,4?-methoxy triphenylamine (V1) or N-phenyl-3,6-methoxy carbazole (V2) as the peripheral donor moiety. Optoelectronic characterization and density functional theory calculations confirmed the intramolecular charge transfer within these new HTMs. UPS and REELS analyses revealed favorable HOMO-LUMO energy level alignment of V1 and V2 with the work functions of MAPbI3 and gold electrode for effective charge extraction. TRPL and transient absorption studies commendably explained better quenching of perovskite's luminescence by V1 over V2, suggesting a better interfacial contact of V1 with the perovskite layer. Accordingly, the PVSCs with V1 and V2 as HTMs in an architecture ITO/SnO2/MAPbI3/HTM(V1 or V2)/Au demonstrated power conversion efficiency (PCE) of 14.05% and 12.73% respectively. Also, the device with V1 retains 75% of its initial efficiency for more than 480 hours. The contact angle measurements revealed the strong hydrophobicity of both alkylated fluorene molecules (V1 and V2), and impedance spectroscopy measurements further revealed higher Rrec values for these HTMs, indicating improved charge transport and reduced recombination losses. These findings demonstrate the potential of the newly developed hydrophobic fluorene-based HTMs for achieving long-lasting performance in PVSCs. © 2025 The Royal Society of Chemistry.Item Enhanced Anti-corrosion and Anti-fouling Properties of Galvanized Iron Using Nanocomposite Hydrophobic Coatings(Springer, 2025) Kumar, P.; Ramesh, M.R.; Doddamani, M.; Narendranath, S.Nanocomposite hydrophobic coatings have garnered substantial interest in recent times due to their remarkable anticorrosion and antifouling attributes. These coatings are designed to repel water and thwart the adherence of contaminants, rendering them valuable for an array of applications, including self-cleaning surfaces, anti-icing coatings, marine protection, and biomedical uses. This study delves into the fabrication of nanocomposite coatings, incorporating mixed oxide nanoparticles of CuO-MgO, MgO-ZnO, and CuO-ZnO at varying weight percentages within a poly (lactic acid) (PLA) matrix. Surface morphology and elemental composition were examined through Field Emission Scanning Electron Microscope (FESEM) and Energy-Dispersive x-ray Analysis (EDAX). The chemical composition of the coatings was assessed using Fourier Transform Infrared Spectroscopy (FTIR), revealing structural changes specific to PLA with Mg-Zn nanocomposite coating. The wettability studies indicate that the PLA/Cu-Mg coated sample exhibits superior hydrophobic properties, with a water contact angle (CA) of 98.2°. This value represents a remarkable 48.7 % increase compared to the bare Galvanised iron (GI) substrate. The coating's mechanical properties were assessed using scratch and adhesion tests. The efficacy of these coatings for anticorrosion and antifouling applications was gauged through comprehensive evaluations, in-vitro corrosion studies, egg white tests, and antibacterial tests. PLA/Mg-Zn nanocomposite coating exhibited exceptional performance in terms of scratch hardness and adhesion strength, whereas PLA/Cu-Zn nanocomposite coating exhibited better anticorrosion and antifouling properties. © ASM International 2024.