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 Exploring the fungal protein cadre in the biosynthesis of PbSe quantum dots(Elsevier B.V., 2017) Jacob, J.M.; Sharma, S.; Mohan Balakrishnan, R.M.While a large number of microbial sources have recently emerged as potent sources for biosynthesis of chalcogenide quantum dots (QDs), studies regarding their biomimetic strategies that initiate QD biosynthesis are scarce. The present study describes several mechanistic aspects of PbSe QD biosynthesis using marine Aspergillus terreus. Scanning electron microscopic (SEM) studies indicated distinctive morphological features such as abrasion and agglomeration on the fungal biomass after the biosynthesis reaction. Further, the biomass subsequent to the heavy metal/metalloid precursor was characterized with spectral signatures typical to primary and secondary stress factors such as thiol compounds and oxalic acid using Fourier Transform Infra-Red Spectroscopic (FTIR) analysis. An increase in the total protein content in the reaction mixture after biosynthesis was another noteworthy observation. Further, metal-phytochelatins were identified as the prominent metal-ion trafficking components in the reaction mixture using Liquid Chromatography Mass Spectroscopic analysis (LCMS). Subsequent assays confirmed the involvement of metal binding peptides namely metallothioneins and other anti-oxidant enzymes that might have played a prominent role in the microbial metal detoxification system for the biosynthesis of PbSe QDs. Based on these findings a possible mechanism for the biosynthesis of PbSe QDs by marine A. terreus has been elucidated. © 2016 Elsevier B.V.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 Melanin nano-pigments for heavy metal remediation from water(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2019) Thaira, H.; Raval, K.; Manirethan, V.; Mohan Balakrishnan, R.M.Melanins are water insoluble polyphenol compounds. The metal ion chelating property of natural melanin is exploited for removal of heavy metals from contaminated water. We optimized biosynthesis of melanin from marine bacterium using different growth media, media components, and operating conditions. Optimized medium yielded 513 mg/L melanin at 36 h of incubation, which was 3.15 times higher than the yield before optimization. Particle size analysis of the biosynthesized melanin indicated a size of 32 ± 0.98 nm. Preliminary investigation indicated that melanin nanoparticles could adsorb different heavy metals such as chromium, selenium, and lead from very low initial concentrations. © 2018, © 2018 Taylor & Francis.Item Bioinspired ZnS: Gd nanoparticles synthesized from an endophytic fungi Aspergillus flavus for fluorescence-based metal detection(MDPI AG, 2019) Uddandarao, P.; Mohan Balakrishnan, R.M.; Ashok, A.; Swarup, S.; Sinha, P.Recently, several nonconventional sources have emerged as strong hotspots for the biosynthesis of chalcogenide quantum dots. However, studies that have ascertained the biomimetic methodologies that initiate biosynthesis are rather limited. The present investigation portrays a few perspectives of rare-earth(Gd)-doped ZnS biosynthesis using the endophytic fungi Aspergillus flavus for sensing metals based on their fluorescence. Analysis of ZnS:Gd nanoparticles was performed by elemental analysis, energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), and transmission electron microscopy (TEM). The results of TEM demonstrated that the particles were polycrystalline in nature, with a mean size of 10-18 nm. The fluorescence amenability of the biogenic ZnS nanoparticles was further used for the development of a simple and efficient sensing array. The results showed sensitive and detectable quenching/enhancement in the fluorescence of biogenic colloidal ZnS nanoparticles, in the presence of Pb (II), Cd (II), Hg (II), Cu (II) and Ni (II), respectively. The fluorescence intensity of the biogenic ZnS:Gd nanoparticles was found to increase compared to that of the ZnS nanoparticles that capacitate these systems as a reliable fluorescence sensing platform with selective environmental applications. © 2019 by the authors.