Faculty Publications
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Item Reduction of reflectance at c-silicon solar cell using nanotexturization(Institute of Electrical and Electronics Engineers Inc., 2014) Maity, S.; Kundu, A.; Das, S.; Chakraborty, P.Reduction in reflection losses of bare silicon surfaces has always attracted many researchers as it by far remains the most important criterion needed for achieving high efficiency solar cells. Anti-reflection coatings (ARC) of dielectrics help in balancing the refractive index mismatch between silicon and air. Although such ARCs help in reducing the reflection losses, they do not cause bending of light rays which is essential for efficient light trapping of the injected light into the cell. The technological leaps in the last few decades have lead to the possibility of nanotextured surfaces comprising of sub-wavelength structures in the optical domain. We report a simple and fast process for nanotexturing of the silicon surface may be achieved by creating silver nano-islands on the silicon surface and etching the exposed silicon surface. © 2014 IEEE.Item Experimental Investigations on RBI Grade 81 Stabilized Lateritic Soil(Springer Science and Business Media Deutschland GmbH, 2021) Chethan, B.A.; Das, S.; Amulya, S.; Ravi Shankar, A.U.R.The effectiveness of the addition of RBI Grade 81 (stabilizer) (dosages of 2, 4, 6, and 8%) to stabilize the largely encountered lateritic soil during construction was investigated. Stabilized lateritic soil mixes were evaluated by conducting a series of experiments, viz., standard and modified compaction, unconfined compressive strength, and California bearing ratio at various curing periods. Mixes under both standard and modified compaction energies have shown the highest density at a 6% stabilizer dosage. A remarkable increase in unconfined compressive strength was observed for the specimens prepared at a 6% stabilizer dosage corresponding to the modified compaction density. An increase in the percentage of stabilizer has increased the California bearing ratio of treated mixes. Exorbitant increase in the soaked California bearing ratio values of the stabilized mixes was observed for higher dosages (6 and 8%). Hence, RBI Grade 81 amended lateritic soil mixes enhance the strength of the subgrade. © 2021, Springer Nature Singapore Pte Ltd.Item Bacterial quorum sensing: Functional features and potential applications in biotechnology(2012) Mangwani, N.; Dash, H.R.; Chauhan, A.; Das, S.Quorum sensing (QS) represents an exceptional pattern of cell-to-cell communication in bacteria using self-synthesized signalling molecules known as autoinducers. Various features regulated by QS in bacteria include virulence, biofilm formation, sporulation, genetic competence and bioluminescence, among others. Other than the diverse signalling properties of autoinducers, there are non-signalling properties also associated with these signalling molecules which make them potential antimicrobial agents and metal chelators. Additionally, QS signal antagonism has also been shown to be a promising alternative for blocking pathogenic diseases. Besides, QS has impressive design features useful in tissue engineering and biosensor technology. Although many aspects of QS are well understood, several other features remain largely unknown, especially in biotechnology applications. This review focuses on the functional features and potential applications of QS signalling molecules in biotechnology. © 2012 S. Karger AG, Basel.Item Titanium foam with coarser cell size and wide range of porosity using different types of evaporative space holders through powder metallurgy route(Elsevier Ltd, 2014) Mondal, D.P.; Patel, M.; Das, S.; Jha, A.K.; Jain, H.; Gupta, G.; Arya, S.B.Ti-foams were made using different evaporative types of space holders such as acrowax and ammonium bicarbonate with a wide range of porosities (55-89%) through powder metallurgy technique. Cold compaction pressure was varied from 100 to 200. MPa in order to examine the effect of cold compaction pressures on the absolute porosities of the foams. The cell size, cell wall thickness and porosities of the foams were characterised as a function of cold compaction pressures and type of space holders. Empirical correlation has been established to predict foam porosities from compaction pressures and volume fraction of space holder. The sintered foams were found to be free from residue of the space holder. However, approximate 8-10% of titanium oxidized during sintering. The foam made with acrowax, as space holder attains slightly higher strength, modulus and energy absorption. © 2014 Elsevier Ltd.Item The effect of the particle shape and strain rate on microstructure and compressive deformation response of pure Ti-foam made using acrowax as space holder(Elsevier Ltd, 2015) Mondal, D.P.; Patel, M.; Jain, H.; Jha, A.K.; Das, S.; Dasgupta, R.Titanium foams of varying amount of porosities have been made using acrowax bits as a space holder through powder metallurgy route. Two types of Ti-particles were used: (i) angular and (ii) spherical in order to see the effect of particle shape on microstructure and deformation behavior. The compressive deformation behavior of Ti-foams with varying porosities and type of particles are studied under different strain rates. It is observed that the microstructural characteristics of Ti-foam varied marginally with the shape of Ti-particles. But the shape of particles influenced reasonably the deformation responses of Ti-foam. The plateau stress, modulus and energy absorption follow power law with relative density irrespective of shape of Ti-particles. All these parameters in Ti-foams are almost invariant to the strain rate. The empirical constants associated with different empirically developed power law relations are different for different shape of Ti-particles. © 2014 Elsevier B.V.Item Reusable floating polymer nanocomposite photocatalyst for the efficient treatment of dye wastewaters under scaled-up conditions in batch and recirculation modes(John Wiley and Sons Ltd vgorayska@wiley.com Southern Gate Chichester, West Sussex PO19 8SQ, 2019) Das, S.; Mahalingam, H.BACKGROUND: In the last decade, research on floating photocatalysts has increased rapidly with polymer substrates being a popular choice. However, most of the published work is on very small volumes and there is very little work on scale-up of such systems. RESULTS: Polystyrene–titanium dioxide nanocomposite floating films were prepared using a facile solvent casting method and tested for the photocatalytic degradation of four different dyes under UV irradiation. The prepared film was characterised by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES) and profilometry. Scale-up studies were done in batch mode under optimised conditions, and for the larger reactor volume, the effect of recirculation was studied. Complete decolourisation of the model dye (Remazol Turquoise Blue) was observed within 80 min in the scaled-up batch process. In the recirculation mode, for a much larger volume of the dye solution, around 75% decolourisation in 6 h was observed. The reusability of the photocatalytic film was tested, and the results promise a minimum decolourisation efficiency of around 70%. Finally, total organic carbon (TOC) and liquid chromatography mass spectrometry (LC-MS) analysis were used to assess the degradation of the dye. The maximum TOC reduction observed was around 25% possibly due to the complex nature of the dye used in this study. The intermediate products of degradation were identified, and a tentative mechanism is suggested. CONCLUSION: This work demonstrates the recirculation aspects of the photocatalytic reactor under the scaled-up conditions for a complex dye. The prepared film showed excellent stability with satisfactory wastewater decontamination under UV irradiation even after repeated use. © 2019 Society of Chemical Industry. © 2019 Society of Chemical IndustryItem Exploring the synergistic interactions of TiO2, rGO, and g-C3N4 catalyst admixtures in a polystyrene nanocomposite photocatalytic film for wastewater treatment: Unary, binary and ternary systems(Elsevier Ltd, 2019) Das, S.; Mahalingam, H.Reduced graphene oxide (rGO) as well as graphitic carbon nitride (g-C3N4) were synthesised and blended along with TiO2 at specific ratios in polystyrene photocatalytic films to find out the optimum efficiency. The prepared photocatalysts were characterised by scanning electron microscopy (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and contact angle analyser. The SEM, XRD, and FTIR analysis indicated that the nanoparticles were evenly distributed on the surface of the polystyrene film. The stability of the polymer film with respect to possible leaching of the embedded catalyst particles was evaluated by ICP-OES analysis. The photocatalytic activity of the admixture was evaluated using remazol turquoise blue dye as a model organic pollutant, and it was found that the photocatalytic ternary admixtures displayed much higher photocatalytic activity (99%) than the unary (89%) or binary (94%) mixtures indicating the synergistic effect of these catalysts. The effect of catalyst ratio, immobilisation, pH, initial dye concentration, irradiated light source, the presence of H2O2 and reusability of the film were also evaluated. The degradation of the dye is confirmed by TOC analysis (40% reduction), and HPLC/MS was used to identify the final degraded compounds. © 2019 Elsevier Ltd.Item Dye degradation studies using immobilized pristine and waste polystyrene-TiO2/rGO/g-C3N4 nanocomposite photocatalytic film in a novel airlift reactor under solar light(Elsevier Ltd, 2019) Das, S.; Mahalingam, H.Complex dyes are not completely removed in most wastewater treatment plants and thus released into nearby waterbodies posing problems to aquatic life and humans. In this study, a chemically synthesized nanocomposite photocatalyst containing TiO2, rGO and g-C3N4 immobilized in a polystyrene film is evaluated for the degradation of the Cu-phthalocyanine complex dye (Remazol Turquoise Blue, RTB) in a multiphase airlift reactor under sunlight. Both pristine and waste polystyrene were used in the synthesis of the film. The characterisation of the powder photocatalyst composite as well as the immobilized photocatalyst film is performed using particle size analyzer, SEM-EDX, BET, XRD, XPS, FTIR, and ICP-OES. The optimization of various parameters affecting the photocatalytic decolourization such as the g-C3N4 quantity in the composite catalyst, catalyst loading, the initial concentration of dye, use of waste polystyrene and catalyst reuse has been studied thoroughly. The photocatalytic treatment of RTB dye under optimum conditions for 90min shows that the decolourization (60%) and degradation (51.43%) as measured by TOC analysis are quite similar. The possible breakdown compounds from the parent molecule after the photocatalytic operation are identified by HPLC-MS. In conclusion, the immobilized nano-composite photocatalyst incorporated into a multiphase airlift reactor, is a very promising system to improve the water quality by TOC reduction, before discharge to nearby natural water sources. © 2019 Elsevier Ltd.Item Novel immobilized ternary photocatalytic polymer film based airlift reactor for efficient degradation of complex phthalocyanine dye wastewater(Elsevier B.V., 2020) Das, S.; Mahalingam, H.Reduced graphene oxide (rGO) as well as graphitic carbon nitride (g-C3N4) catalysts were synthesized and a physical admixture of rGO and g-C3N4 along with TiO2 in the ratio of 1:1:1 by weight was immobilized in a polystyrene film using the facile solvent casting method. An internal loop airlift reactor with a working volume of 1.2 litres incorporating the prepared polymer-based photocatalytic film was designed and tested for the photocatalytic degradation of remazol turquoise blue dye synthetic wastewater. The reactor parameters affecting the photocatalytic activity such as airflow rate and Di/Do (ratio of draft tube diameter to outer tube diameter) were evaluated. The successful operation of the reactor obtained using the ternary immobilized catalyst mixture film gave 92.25% total organic carbon reduction and 94% decolourization within 140 min, compared to 91% decolourization by the slurry form within 40 min. Complete and quicker decolourization of the dye was also demonstrated under the influence of O3 or H2O2. The immobilized catalyst was successfully reused four times. The ternary catalyst admixture employed in this work and the unique design of the photocatalytic reactor helps to increase the degradation rate of toxic textile effluents thus making it suitable for larger scales of treatment. © 2019 Elsevier B.V.Item Evaluation of implant properties, safety profile and clinical efficacy of patient-specific acrylic prosthesis in cranioplasty using 3D binderjet printed cranium model: A pilot study(Churchill Livingstone, 2021) Basu, B.; Bhaskar, N.; Barui, S.; Sharma, V.; Das, S.; Govindarajan, N.; Hegde, P.; Perikal, P.J.; Antharasanahalli Shivakumar, M.; Khanapure, K.; Jagannatha, A.There exists a significant demand to develop patient-specific prosthesis in reconstruction of cranial vaults after decompressive craniectomy. we report here, the outcomes of an unicentric pilot study on acrylic cranial prosthesis fabricated using a 3D printed cranium model with its clinically relevant mechanical properties. Methods: The semi-crystalline polymethyl methacrylate (PMMA) implants, shaped to the cranial defects of 3D printed cranium model, were implanted in 10 patients (mean age, 40.8 ± 14.8 years). A binderjet 3D printer was used to create patient-specific mould and PMMA was casted to fabricate prosthesis which was analyzed for microstructure and properties. Patients were followed up for allergy, infection and cosmesis for a period of 6 months. Results: As-cast PMMA flap exhibited hardness of 15.8 ± 0.24Hv, tensile strength of 30.7 ± 3.9 MPa and elastic modulus of 1.5 ± 0.1 GPa. 3D microstructure of the semi-crystalline acrylic implant revealed 2.5–15 µm spherical isolated pores. The mean area of the calvarial defect in craniectomy patients was 94.7 ± 17.4 cm2. We achieved a cranial index of symmetry (CIS -%) of 94.5 ± 3.9, while the average post-operative Glasgow outcome scale (GOS) score recorded was 4.2 ± 0.9. Conclusions: 3D printing based patient-specific design and fabrication of acrylic cranioplasty implant is safe and achieves acceptable cosmetic and clinical outcomes in patients with decompressive craniectomy. Our study ensured clinically acceptable structural and mechanical properties of implanted PMMA, suggesting that a low cost 3D printer based PMMA flap is an affordable option for cranioplasty in resource constrained settings. © 2021 Elsevier Ltd