Faculty Publications
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Item Biosynthesis of lead selenide quantum rods in marine Aspergillus terreus(2014) Mary Jacob, J.; Mohan Balakrishnan, R.M.; Kumar, U.B.Biosynthesis of fluorescent, semiconductor lead selenide (PbSe) quantum rods was initiated in lead and selenium tolerant marine Aspergillus terreus. TEM and SEM images revealed the formation of rod like structures having an average diameter of 59 nm. Compositional analysis using EDAX followed by optical and structural characterization by XRD, UV-vis and FTIR spectrophotometry confirmed the biogenesis of crystalline PbSe nanoparticles with quantum confinement effects. © 2014 Elsevier B.V.Item Biosynthesis and optimization of silver nanoparticles by endophytic fungus Fusarium solani(Elsevier, 2014) Sogra Fathima, B.; Mohan Balakrishnan, R.M.A mathematical model for optimization of factors influencing the biosynthesis of silver nanoparticles by an endophytic fungus Fusarium solani was designed. A high determination coefficient R2 of 99.3% was obtained. Structural characterization by UV-vis, TEM, XRD and FTIR revealed the formation of spherical nanoparticles. © 2014 Elsevier B.V.Item Optimised microwave-assisted biosynthesis of silver nanoparticles from Nothapodytes foetida leaf extracts and its anti-microbial activities(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2016) Roopesh, R.; Geedhika, G.; D'Souza, J.; Anandhan, S.; Bhat, K.U.; Jaya M, J.; Fathima B, S.; Mohan Balakrishnan, R.M.The present investigation reports the biogenesis of silver nanoparticles (Ag NPs) using extracts of a medicinal plant Nothapodytes foetida. Total phenolic content (TPC) and ferric reducing antioxidant power (FRAP) assay were carried out for the microwave-assisted extract (MAE) of N. foetida using methanol as solvent and the conditions for extraction were optimised by response surface methodology (RSM). The effects of operating variables such as extraction time, temperature and ratio of sample to solvent were studied using central composite design (CCD). A mathematical model with a high determination coefficient (R2) for TPC (0.991) and FRAP (0.995) was obtained. The optimal conditions of extraction for TPC were 48.6 ºC, 23.15 min and 2.04:30 (g/mL) and for FRAP 52.31ºC, 12.32 min and 1.67: 30 (g/mL). Under these conditions, the experimental yields of TPC and FRAP were 2.426 mg gallic acid equivalents (GAE)/g dry powder and 14.985mg of FeSO4·7H2O/g of dry powder, respectively. Ag NPs were characterised using UV–Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The synthesised Ag NPs have also shown potent activity against the human pathogenic Staphylococcus aureus. © 2016 Informa UK Limited, trading as Taylor & Francis Group.Item Selenium Biosorption and Recovery by Marine Aspergillus terreus in an Upflow Bioreactor(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2016) Raja, C.P.; Jacob, J.M.; Mohan Balakrishnan, R.M.Experiments were conducted to study the Selenium (Se) biosorption and recovery by marine Aspergillus terreus in an upflow bioreactor for a period of 8 days. The Se tolerance of the marine fungus was initially confirmed by visual and microscopic observations that evinced intact fungal cells in an Se-amended medium with sparse changes in the spore texture and cellular number by the seventh day of biosorption studies in the upflow bioreactor. Further, the effect of pH and contact time on the percentage of Se biosorption, in an upflow bioreactor containing fungal pellets, was investigated. It was analyzed that pH ranges of 6-7 and a contact time of 5 days resulted in 85-87% biosorption of Se by the fungal biomass. The interaction of the fungus with the induced Se stress in the medium was monitored regularly for studying the uptake of the metalloid and the possible biosynthesis of Se nanoparticles. Analyses using ultraviolet visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) studies revealed the formation of crystalline Se nanocrystals with an average diameter of 500 nm on the fungal cell wall. Fourier transform infrared (FTIR) spectroscopic analysis indicated the possible involvement of fungal protein groups that aid the binding of the biosorbed Se nanoparticles on to the fungal cell wall. © 2015 American Society of Civil Engineers.Item Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection(Elsevier B.V., 2017) Uddandarao, U.; Mohan Balakrishnan, R.M.Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II–IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu2 + and Mn2 + in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV–Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem. © 2016 Elsevier B.V.Item Biosynthesis of cobalt oxide nanoparticles using endophytic fungus Aspergillus nidulans(Academic Press, 2018) Vijayanandan, A.S.; Mohan Balakrishnan, R.M.Metallic oxide nanoparticles have profound applications in electrochemical devices, supercapacitors, biosensors and batteries. Though four fungi were isolated from Nothapodytes foetida, Aspergillus nidulans was found to be suitable for synthesis of cobalt oxide nanoparticles, as it has proficient tolerance towards metal under study. The broth containing precursor solution and organism Aspergillus nidulans had changed from pink to orange indicating the formation of nanoparticles. Characterization by x-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive x-ray analysis (EDX) confirmed the formation of spinel cobalt oxide nanoparticles at an average size of 20.29 nm in spherical shape with sulfur-bearing proteins acting as a capping agent for the synthesized nanoparticles. The nanoparticles could be applied in energy storage, as a specific capacitance of 389 F/g showed competence. The study was a greener attempt to synthesize cobalt oxide nanoparticles using endophytic fungus. © 2018 Elsevier LtdItem Photocatalytic degradation of Irgalite violet dye using nickel ferrite nanoparticles(IWA Publishing 12 Caxton Street London SW1H 0QS, 2019) Vijay, S.; Mohan Balakrishnan, R.M.; Rene, E.R.; Uddandarao, P.Nanotechnologies have prominent applications in the field of science and technology owing to their size-tunable properties providing a promising approach for degradation of various pollutants. In this scenario, the present work aims to study the effect of nickel ferrite nanoparticles on the degradation of Irgalite violet dye by Fenton’s reaction using oxalic acid as an oxidizing agent in the presence of sunlight. The effect of pH and adsorbent dosage on the rate of dye degradation was monitored. Based on these studies it was observed that 99% dye degradation was achieved for catalyst dosage of 0.2 g, 400 ppm dye concentration and 2.0 mM oxalic acid at pH 3.0 within 60 min. The studies reveal that the degradation follows pseudo-first-order kinetics and the catalyst reusability remained constant almost for five cycles. Further, nickel ferrite nanoparticles are proven to be an efficient alternative for the removal of dyes from coloured solutions. © IWA Publishing 2019Item Decolorization of Reactive Blue 220 aqueous solution using fungal synthesized Co3O4 nanoparticles(IWA Publishing 12 Caxton Street London SW1H 0QS, 2019) Valappil, R.S.K.; Vijayanandan, A.S.; Mohan Balakrishnan, R.M.In this work, the photocatalytic activity of the biosynthesized cobalt oxide (Co3O4) nanoparticle (NP) is investigated using a textile dye Reactive Blue 220 (RB220) and decolorization % was monitored using UV–Vis spectrophotometer. The photocatalytic activity has been observed maximum at alkaline pH of 9, NP dosage of 250 mg/L, and reaction time of 270 min. In the presence of UV light irradiation, a maximum dye concentration of 10 mg/L was treated effectively using 150 mg/L NP, and 67% decolorization was achieved. Reaction kinetics has been analyzed, and the reaction followed the pseudo kinetics model with an activation energy of -484 kJ mol-1. © IWA Publishing 2019Item Solar assisted photocatalytic degradation of organic pollutants in the presence of biogenic fluorescent ZnS nanocolloids(Elsevier Ltd, 2019) Uddandarao, P.; Hingnekar, T.A.; Mohan Balakrishnan, R.M.; Rene, E.R.The main aim of this study was to ascertain the photocatalytic degradation of organic pollutants present in aqueous phase using fluorescent biogenic ZnS nanocolloids produced from an endophytic fungus Aspergillus flavus. The degradation studies were carried out using different organic pollutants such as methyl violet (MV), 2,4-dichlorophenoxyacetic acid (2,4-D) and paracetamol (PARA) for 120 min, 270 min and 240 min, respectively, at pH varying from 3.0 to 11.0. The results from this study indicate that the degradation efficiency of ZnS nanocolloids for MV, 2,4-D and PARA were 87%, 33% and 51%, respectively, at the optimum concentration of 100 mg/L of the tested organic pollutants. At different time intervals, the samples were analyzed for their chemical oxygen demand (COD) and total organic carbon (TOC) contents. The reduction of COD and TOC were 78% and 74% for MV at 120 min; 55.5% and 57.2% for 2,4-D at 270 min and 47.6% and 44.5% for PARA at 240 min, respectively. The degradation pathway was determined based on the mass spectrum and the intermediates formed; in addition, the interaction between organic pollutants and nanocolloids was also elucidated based on atomic force microscopy (AFM) and fluorescence spectrum. © 2019 Elsevier LtdItem Evaluation of photothermal properties for absorption of solar energy by Co3O4 nanofluids synthesized using endophytic fungus Aspergillus nidulans(Elsevier Ltd, 2020) Vijayanandan, A.S.; Kandath Valappil, R.S.; Mohan Balakrishnan, R.M.An attempt has been made to compare the optical properties of cobalt oxide (Co3O4) nanoparticles using experimental values and theoretical predictions. Optical transmittance of the nanoparticles obtained was higher than 65% in 550–850 nm containing visible spectrum and the experimental results were in accordance with the predictive datum. The absorption coefficient peak observed is close to the predictive value and is present in the visible region of the light. In addition, there was an excellent agreement between theoretical and experimental results in extinction coefficient and refractive index. Besides, this work proposes and validates a novel idea of using Co3O4 nanofluids to enhance solar thermal conversion efficiency. Co3O4 nanofluids synthesized using endophytic fungus Aspergillus nidulans isolated from a medicinal plant, Nothapodytes foetida has been used to illustrate the energy storage capacity of nanofluids. Experimental results reveal that Co3O4 nanofluids have good specific absorption rate (SAR) and better photo-thermal conversion efficiency than water. Nanofluid exhibited a greater temperature gradient than pure water, which is desired. Thus the good absorption ability of Co3O4 nanofluids for solar energy indicated that it is suitable for direct absorption solar thermal energy systems. © 2019