Faculty Publications
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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 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 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. © 2019Item Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes(Springer, 2020) Manirethan, V.; Gupta, N.; Mohan Balakrishnan, R.M.; Raval, K.Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon–Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.