Browsing by Author "Sarkar, P."

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Carbohelicenes and thiahelicene from phthalaldehydes through Perkin approach
(2019) Sarkar, P.; Das, B.K.; Chakraborty, D.; Muthamma, K.
Synthesis and structural features of helical nanographene molecules comprising of seven benzene rings are examined. Thus dibutyl-dicarboxylate functional [7]helicene and its two regioisomers, dinaphtho[1,2 a:1?,2? h]anthracene and naphtho[2,1 c]pentahelicene, have been synthesized in two steps through Perkin approach using napthalene-2-acetic acid and ortho- or meta-phthalaldehydes. The feasibility of this approach to construct sulfur doped twisted dithiaarenes is also investigated by using thiophene-3-acetic acid. While dithiaarenes from meta-phthalaldehyde remains challenging, synthesis and characterization of planar anthra[1,2 b:5,6 b']dithiophene and twisted 1,12-dithiapentahelicene is successful from ortho-phthalaldehyde. Conformational analysis with DFT calculation shows unique helicity preference in such doubly helical carbon nanostructures. Absorption and emission behavior of these ?-extended molecules shows enhanced conjugation. 2019 Elsevier B.V.
Carbohelicenes and thiahelicene from phthalaldehydes through Perkin approach
(Elsevier B.V., 2019) Sarkar, P.; Das, B.K.; Chakraborty, D.; Muthamma, K.
Synthesis and structural features of helical nanographene molecules comprising of seven benzene rings are examined. Thus dibutyl-dicarboxylate functional [7]helicene and its two regioisomers, dinaphtho[1,2–a:1?,2?–h]anthracene and naphtho[2,1–c]pentahelicene, have been synthesized in two steps through Perkin approach using napthalene-2-acetic acid and ortho- or meta-phthalaldehydes. The feasibility of this approach to construct sulfur doped twisted dithiaarenes is also investigated by using thiophene-3-acetic acid. While dithiaarenes from meta-phthalaldehyde remains challenging, synthesis and characterization of planar anthra[1,2–b:5,6–b']dithiophene and twisted 1,12-dithiapentahelicene is successful from ortho-phthalaldehyde. Conformational analysis with DFT calculation shows unique helicity preference in such doubly helical carbon nanostructures. Absorption and emission behavior of these ?-extended molecules shows enhanced conjugation. © 2019 Elsevier B.V.
High figure-of-merit in Zn, Sb co-doped Mg2Si0.3Sn0.7 alloy through simultaneous optimization of electrical and thermal transports
(Elsevier Ltd, 2025) Sarkar, P.; Gupta, P.; Shenoy, U.S.; Singh, S.; Kundu, S.; Kumawat, N.; Kedia, D.K.; Bhat, D.K.; Bhattacharya, S.; Singh, A.
The derivatives of Mg2Si have recently attracted wide attention as promising thermoelectric materials due to earth abundant and environment friendly low-cost constituents. The main challenge in optimizing the thermoelectric figure of merit ZT, is the low electrical and high thermal conductivities of Mg2Si. The present study demonstrates high ZT of ?1.55 at 673 K in Mg2Si0.3Sn0.7 through simultaneous optimization of electrical and thermal transport through Sb and Zn co-doping. The ultra-low deformation and alloy scattering potentials in Sb and Zn co-doped samples helps in maintaining record high Hall mobility ?70–90 cm2/V.s. The doping induced pudding mold band structure with hyperconvergence in conduction band balances high Seebeck coefficient and high electrical conductivity. The point defects and dislocations created by doping helps in lowering of lattice thermal conductivity as well. The uni-leg power generator fabricated using optimized Mg1.96Zn0.04(Si0.3Sn0.7)0.98Sb0.02 exhibits a record efficiency of ?9.5 % at ?T ? 329 K. © 2025
Optical properties of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO tandem absorber coatings by phase-modulated spectroscopic ellipsometry
(2017) Jyothi, J.; Biswas, A.; Sarkar, P.; Soum-Glaude, A.; Nagaraja, H.S.; Barshilia, H.C.
TiAlC, TiAlCN, TiAlSiCN, TiAlSiCO, and TiAlSiO layers of thicknesses ~2.2 ?m, 755, 491, 393, and 431 nm, respectively, were deposited on stainless steel, silicon, and glass substrates to study their refractive indices and extinction coefficients using the phase-modulated spectroscopic ellipsometry in the wavelength range of 300 1200 nm. Absorption coefficient of each layer was calculated from the extinction coefficient of the layer. The results indicate that the first three layers (i.e., TiAlC, TiAlCN, and TiAlSiCN) are absorbing in nature, while TiAlSiCO and TiAlSiO act as intermediate and antireflection layers. Subsequently, a tandem absorber of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO with layer thicknesses of 62, 20, 18, 16, and 27 nm, respectively, was deposited on stainless steel substrates to fabricate a spectrally selective coating with absorptance of 0.961 and emittance of 0.15 at 82 C. The obtained refractive indices and extinction coefficients of the tandem absorber were used to simulate the reflectance of the deposited tandem absorber using SCOUT software. Simulated reflectance data of the tandem absorber showed a good agreement with the experimental data measured by UV Vis NIR and FTIR spectrophotometry. The angular dependence of the selective properties of the tandem absorber was studied by measuring the reflectance spectra of the tandem absorber at different incident angles. 2017, Springer-Verlag GmbH Germany.
Optical properties of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO tandem absorber coatings by phase-modulated spectroscopic ellipsometry
(Springer Verlag service@springer.de, 2017) Jyothi, J.; Biswas, A.; Sarkar, P.; Soum-Glaude, A.; Nagaraja, H.S.; Barshilia, H.C.
TiAlC, TiAlCN, TiAlSiCN, TiAlSiCO, and TiAlSiO layers of thicknesses ~2.2 ?m, 755, 491, 393, and 431 nm, respectively, were deposited on stainless steel, silicon, and glass substrates to study their refractive indices and extinction coefficients using the phase-modulated spectroscopic ellipsometry in the wavelength range of 300–1200 nm. Absorption coefficient of each layer was calculated from the extinction coefficient of the layer. The results indicate that the first three layers (i.e., TiAlC, TiAlCN, and TiAlSiCN) are absorbing in nature, while TiAlSiCO and TiAlSiO act as intermediate and antireflection layers. Subsequently, a tandem absorber of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO with layer thicknesses of 62, 20, 18, 16, and 27 nm, respectively, was deposited on stainless steel substrates to fabricate a spectrally selective coating with absorptance of 0.961 and emittance of 0.15 at 82 °C. The obtained refractive indices and extinction coefficients of the tandem absorber were used to simulate the reflectance of the deposited tandem absorber using SCOUT software. Simulated reflectance data of the tandem absorber showed a good agreement with the experimental data measured by UV–Vis–NIR and FTIR spectrophotometry. The angular dependence of the selective properties of the tandem absorber was studied by measuring the reflectance spectra of the tandem absorber at different incident angles. © 2017, Springer-Verlag GmbH Germany.
Synergistic bioremediation of marine oil spills using dual strain consortium immobilized rice husk biochar
(Elsevier B.V., 2025) Sarkar, P.; Pal, S.J.
Bacteria capable of degrading oil spillage hydrocarbons are widely identified, yet single bacterial strains often underperform in real environments due to competition with native microorganisms, leading to decreased degradation efficiency. In this study, an eco-friendly approach was developed for removing hydrocarbons from aqueous systems by immobilizing consortium of Novosphingobium sp. MCC 3051 and Alcanivorax sp. MCC 4337 onto rice husk-derived biochar (RHB). The Hydrocarbons remediation process was systematically optimized using response surface methodology (RSM). MCC 3051 and MCC 4337 exhibited a highly hydrophobic cell surface. Genetic analysis revealed multiple metabolic pathways for breaking down both alkanes and aromatic hydrocarbons. Experimentally, MCC 3051 and MCC 4337 completely degraded short-chain Hydrocarbons (C10–C22) and achieved over 97% degradation within 7 days. These findings suggest MCC 3051 and MCC 4337 hold strong promise for remediating oil-contaminated water due to its broad degradation range and high environmental adaptability. Gas Chromatography (GC) analyses identified the degradation products, signifying a synergistic effect of bacterial metabolism and adsorption in the Hydrocarbons removal mechanism. These findings highlight the potential of immobilized MCC 3051, MCC 4337 and Consortium loaded rice husk biochar (CRHB) for efficient remediation of marine oil-contaminated environments. © 2025 The Author(s)
Synthesis of Au/Si hybrid nanostructures with tuned optical properties via ultra-short laser pulses for in-Situ nanostructures generation (ULPING)
(Elsevier B.V., 2023) Jamwal, N.S.; Sarkar, P.; Kiani, A.
The research was based on nano-structuring of gold coated silicon and forming a layered Au/Si hybrid nanostructures with tuned opto-electrical properties. We employed Ultra-short Laser Pulses for In-Situ Nanostructure Generation (ULPING), a novel method for synthesizing the nano hybrid structured substrates. The variation in irradiation (power) and patterning or scanning (pitch and scan speed) parameters of the laser was done in order to create the samples. The morphological and material characterization analysis was performed using SEM, EDX and XPS which confirmed the formation of hybrid Au/Si nanostructures with SiO2 nanocoating. The optical properties of the structure were evaluated using the diffuse reflectance spectroscopy and the electrical properties of the composite structure was done using a 4-point probe method. We saw an enhanced band gap for all the samples in comparison with Au–Si control samples. Also, by changing the laser pulses parameters, wide range of variations in the optical and electrical properties were observed. The band gap of the hybrid nanostructured layer (HNL) was also evaluated using XPS and the band offset was determined for the nanostructured composites. © 2023 Elsevier B.V.