Faculty Publications
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Publications by NITK Faculty
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Item Effect of cadmium incorporation on the properties of zinc oxide thin films(Springer Nature, 2018) Bharath, S.P.; Bangera, K.V.; Shivakumar, G.K.CdxZn1-xO (0 ? x ? 0.20) thin films are deposited on soda lime glass substrates using spray pyrolysis technique. To check the thermal stability, CdxZn1-xO thin films are subjected to annealing. Both the as-deposited and annealed CdxZn1-xO thin films are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDAX) to check the structural, surface morphological and compositional properties, respectively. XRD analysis reveals that the both as-deposited and annealed CdxZn1-xO thin films are (002) oriented with wurtzite structure. SEM studies confirm that as-deposited, as well as annealed CdxZn1-xO thin films are free from pinholes and cracks. Compositional analysis shows the deficiency in Cd content after annealing. Optical properties evaluated from UV-Vis spectroscopy shows red shift in the band gap for CdxZn1-xO thin films. Electrical property measured using two probe method shows a decrease in the resistance after Cd incorporation. The results indicate that cadmium can be successfully incorporated in zinc oxide thin films to achieve structural changes in the properties of films. © Springer-Verlag GmbH Germany, part of Springer Nature 2018.Item Improvement of third-order NLO properties of vacuum deposited Cd1-xPbxS nanostructured thin films for optoelectronic device applications(Elsevier Ltd, 2023) Bairy, R.; Vijeth, H.; Kulkarni, S.D.; Murari, M.S.; Bhat K, U.K.A polycrystalline nanostructured cadmium lead sulfide thin film was deposited using the thermal evaporation (PVD) technique (Cd1-xPbxS with x = 0.00, 0.01, 0.05 and 0.1 wt.% of Pb). Structural parameters of as-prepared Cd1-xPbxS thin films have been studied through X-ray diffraction. The optical investigation demonstrates that Cd1-xPbxS film's optical band gap (Eg) may be adjusted from the visible to the near-infrared region. (2.64 - 2.42 eV). The film is substantially more appropriate for absorbing layers in solar cells and optoelectronic applications due to the large decrease in ‘Eg.’ The enhanced Pb doping was found to have altered the surface morphology, verified by Field Emission Scanning Electron Microscopy (FESEM) images. The doped films also showed a significant red shift in the band edge and increased transmittance in the visible and NIR regions. The third-order nonlinear optical (TONLO) parameters of the samples were determined from the Q-switched Nd: YAG laser with 65-ps pulse duration at 1064 nm. The investigated TONLO components such as nonlinear absorption coefficient (β), nonlinear refractive index (n2) and the susceptibility χ(3)were found to be in the range from 1.16 × 10−3 to 4.12 × 10−3 (cmW−1), 1.06 × 10−8 to 3.32 × 10−8 (cm2 W−1) and 1.23 × 10−4 to 5.62 × 10−4 (esu) respectively. The results indicate that Pb-doping on CdS nanostructures on surface morphology can be used to modify NLO characteristics.Cd1-xPbxS thin film is a potential and able material for optoelectronic device applications, as seen by these encouraging NLO results. © 2023 Elsevier LtdItem Meso-tris(2-furyl/2-thienyl) substituted porphyrin-ferrocene ‘click’ conjugates: synthesis, experimental, and computational studies(Royal Society of Chemistry, 2024) Shet, S.N.; Patil, M.; Shetti, V.S.The chemical synthesis of 5-(4-azidophenyl)-10,15,20-tris(2-furyl/2-thienyl)porphyrins and their utilization in a Cu(i) catalyzed alkyne-azide ‘click’ reaction (CuAAC) with ethynylferrocene to obtain the hitherto unknown meso-tris(2-furyl/2-thienyl) substituted porphyrin-ferrocene ‘click’ conjugates are reported. These new ‘click’ conjugates were studied along with the reference ‘click’ conjugates containing all-meso-aryl substituted porphyrins by experimental and computational methods. Compared to the reference, the new conjugates displayed red-shifted absorption/emission bands, easier porphyrin ring reduction, and an efficient photoinduced electron transfer (PET) process from ferrocene to a porphyrin unit. Density functional theory (DFT) calculations performed on these conjugates revealed a good correlation with the experimental results. © 2024 The Royal Society of Chemistry.Item A comprehensive study uncovering physical, structural, and optical properties of Cu2O and TiO2-reinforced borosilicate glasses as optical filters(Elsevier B.V., 2024) Raghuvanshi, V.; Rashmi, I.; Ingle, A.; Shashikala, H.D.; Nagaraja, H.S.In this study, the integration of transition metal oxides (TMOs), specifically Cu2O and TiO2, into a borosilicate glass matrix (30SiO2–35B2O3–35Na2O–5CaF2-X (TMO)) was investigated for enhanced glass functionality. Glass samples with varying TMO concentrations (X = 0, 1, 2, 3, 4 mol%) were prepared using the melt-quenching technique. X-ray diffraction confirmed the amorphous nature of the synthesized samples, while FTIR analysis showed structural changes, transitioning from trigonal BO3 to BO4 tetrahedra, alongside the formation of non-bridging oxygen species due to TMO integration. UV–Vis spectroscopy demonstrated a red shift in optical absorption profiles, correlating with a reduction in the indirect band gap as TMO content increased. Photoluminescence studies showed distinct behaviors, with Cu2O suppressing emission peaks and TiO2 exhibiting intriguing blue and green emissions, diminishing at higher concentrations. It was attributed that Cu2O had a larger impact on altering the glass network than TiO2. These findings contribute to understanding the properties of Cu2O and TiO2-containing borosilicate glasses, suggesting tailored optical properties for potential applications as bandpass filter and UV blocker. © 2024 Elsevier B.V.Item 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.; AnandThis 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 AuthorsItem Rational design of an isatin-based colorimetric and solvatochromic receptor for carbonate ions and its application in molecular-scale logic gates & memory units(Elsevier B.V., 2025) Akhil Kumar, M.M.; Dhawale, A.; Trivedi, D.R.A simple and highly sensitive isatin-based colorimetric sensor ISAT 3(a-d) was synthesized through a single-step reaction. The as-prepared receptor ISAT 3b with carbonate ions (CO32? ions) shows a significant red shift in the UV–visible absorption spectra and a visible color change from pale yellow to pink. Also, the receptor ISAT 3b shows unique solvatochromic behavior with CO32? ions in different aprotic solvents and solvent compositions. Moreover, the receptor's pink coloration (absorption maxima at 544 nm) with CO32? ions could be reversible by adding HSO4? ions (attain initial pale-yellow color, absorption maxima at 425 nm), which can be repeatable. The observed color changes with spectral shift and reversibility of the receptor with CO32? ions and HSO4? ions provide “ON-OFF” switching for applying molecular logic gates. Receptors exhibited properties, such as reversibility and repeatability, benefit the design of a molecular-scale sequential memory unit with a display of “Writing-Reading-Erasing-Reading”. The real sample analysis was also carried out to prove the practical applicability of receptor (ISAT 3b) for detecting CO32? ions. © 2024 Elsevier B.V.Item Porphyrin-azoheteroarenes: synthesis, photophysical, and computational studies(Royal Society of Chemistry, 2025) Shet, S.N.; Bhat, V.G.; Swathi, S.G.; Udayakumar, U.; Shetti, V.S.Azobenzenes (Ph-N = N-Ph) are well-known photochromic compounds with widespread applications. Replacing one or both phenyl rings of azobenzenes with heteroarenes leads to a new class of compounds known as azoheteroarenes (Het-N N-Ph/Het). Azoheteroarenes have gained attention as promising alternatives to traditional azobenzenes in the field of photopharmacology due to their ability to undergo photoswitching under visible light. Interestingly, the chemistry of porphyrin-containing azoheteroarenes has been underexplored. In this study, we present the synthesis of hitherto unknown hybrid molecules: porphyrin-azopyrroles (porphyrin-N N-pyrrole) and porphyrin-azoindoles (porphyrin-N N-indole), which also feature porphyrins with five-membered meso-substituents, such as 2-furyl and 2-thienyl groups. The porphyrin-azoheteroarenes with meso-tris(2-furyl/2-thienyl) substitutions demonstrate red-shifted absorption and emission bands, more significant Stokes shifts, and smaller optical bandgaps compared to hybrids containing only meso-aryl groups. Additionally, these porphyrin-azoheteroarenes exhibit higher fluorescence emission intensities than their corresponding precursor porphyrins. © 2025 The Royal Society of Chemistry.Item Deep-eutectic solvent-assisted green synthesis of MAX-phase Cr2AlC and its 2D-MXene derivative Cr2CTxtowards room-temperature detection of ammonia gas(Elsevier Ltd, 2025) Lokeshwar, H.; Lakshmi Praveen, L.; Mandal, S.; Shakti, N.This study explores the novel and eco-friendly chemical etching of bulk Cr2AlC MAX phases using a deep eutectic solvent (DES) mixture of choline chloride (ChCl) and anhydrous ferric chloride (FeCl3) to synthesize chromium carbide (Cr2CTx) MXene nanolayers. ChCl-FeCl3enables a fluoride-free transformation approach to synthesize Cr2CTxMXene via selective etching of aluminium interlayers, resulting in mixed surface terminations (-O, -OH, -Cl) confirmed from bond vibrations observed in FTIR transmittance spectra. Also, the FESEM micrographs confirm the formation of Cr2CTxnanolayers with successful cleavage of Cr2AlC MAX phase nanolaminates identified from a distinct red shift of D-band with the highest ID/IGratio peak intensity ratio, confirming the presence of high defect concentration in Cr2CTxMXene. The hydrothermally synthesized SnO2powders exhibiting a rutile tetragonal phase average particle size of 35.8 ± 0.8 nm were mixed with Cr2CTxto formulate screen-printable inks for the fabrication of Cr2CTx, SnO2, and their composite Cr2CTx-SnO2gas sensors. The addition of Cr2CTxdemonstrated a detrimental effect on the gas-sensing performance of the SnO2sensor, which was further supported from XPS analysis. However, the SnO2sensor recorded the highest gas-response of ?452 towards 100 ppm of ammonia gas among all sensors, highlighting the role of oxygen defects confirmed from photoluminescence spectra. This work paves the way for a novel and eco-friendly etching approach of MAX-phases and helps in their research towards the development of ultra-sensitive gas sensors. © 2025 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.