Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
16 results
Search Results
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 Synthesis of silver nanoparticles using medicinal Zizyphus xylopyrus bark extract(Springer Nature, 2015) Babu, B.; Devadiga, A.; Shetty K, V.K.; Saidutta, M.B.In the present paper, biosynthesis of silver nanoparticles using Zizyphus xylopyrus bark extract is reported. Z. xylopyrus bark extract is efficiently used for the biosynthesis of silver nanoparticles. UV–Visible spectroscopy showed surface plasmon resonance peaks in the range 413–420 nm confirming the formation of silver nanoparticles. Different factors affecting the synthesis of silver nanoparticles like methodology for the preparation of extract, concentration of silver nitrate solution used for biosynthesis and initial pH of the reaction mixture were studied. The extract prepared with 10 mM AgNO3 solution by reflux extraction method at optimum initial pH of 11, resulted in higher conversion of silver ions to silver nanoparticles as compared with those prepared by open heating or ultrasonication. SEM analysis showed that the biosynthesized nanoparticles are spherical in nature and ranged from 60 to 70 nm in size. EDX suggested that the silver nanoparticles must be capped by the organic components present in the plant extract. This simple process for the biosynthesis of silver nanoparticles using aqueous extract of Z. xylopyrus is a green technology without the usage of hazardous and toxic solvents and chemicals and hence is environment friendly. The process has several advantages with reference to cost, compatibility for its application in medical and drug delivery, as well as for large-scale commercial production. © 2014, The Author(s).Item Insights into the optical and anti-bacterial properties of biogenic PbSe quantum rods Optical and anti-bacterial properties of biogenic PbSe quantum rods(Elsevier, 2016) Jacob, J.M.; Raj Mohan, B.; Akshay Gowda, K.M.The detailed optical properties of lead selenide (PbSe) quantum rods biosynthesized in marine Aspergillus terreus were apprehended theoretically using ab initio calculations based on the experimental absorption spectrum. These studies indicate that the absorption coefficient of the biosynthesized PbSe quantum rods increases linearly with incident photon energies. The variation of other optical constants like extinction coefficient, refractive index and reflectance was comparable to that of the chemically synthesized counterparts. Further, the high dielectric constant and remarkable fluorescence of the biogenic PbSe quantum rods pronounce their application in opto-electronic devices in the Near Infra-Red and Ultraviolet spectral regime. The biosynthesized PbSe quantum rods were also found to possess appreciable anti-bacterial activity against various gram positive and gram negative bacterial species thus enhancing the relevance of the same for practical utility. Based on these results it can be concluded that biogenic PbSe quantum rods can be envisaged as potential candidates for bio-imaging, bio-sensing and other photo-voltaic applications. © 2014 The AuthorsItem 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 Biosynthesis of copper nanoparticles using copper-resistant Bacillus cereus, a soil isolate(Elsevier Ltd, 2016) Tiwari, M.; Jain, P.; Raghu Chandrashekar, R.; Narayanan, K.; Bhat, K.U.; Udupa, N.; Rao, J.V.Microorganisms are useful systems for the production of biocompatible metal nanoparticles. Copper, an essential element of life, has good therapeutic potential. However, copper lacks suitable form for effective in vivo delivery, which has diminished its applicability. In this study, we produced biosynthesized copper nanoparticles (BCuNps) using a copper-resistant bacterial isolate from copper mine. The organism was able to tolerate >10 mM of copper and when analysed by 16S rRNA technique, showed 100% similarity with Bacillus cereus. BCuNps, produced by this microorganism, in cell-free filtrate, were characterized for surface plasmon resonance (SPR), particle's characteristics, spectroscopic properties and morphology. SPR peaks for BCuNps were recorded between 570–620 and 350–370 nm. BCuNps characteristics, namely particle size distribution, polydispersity index and zeta potential were found to be 11–33 nm, 0.433 and (?) 19.6 mV, respectively. Scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) analyses confirmed the uniform morphology; X-ray diffraction (XRD) spectrum revealed the crystalline nature; and Fourier transform infrared (FTIR) spectrum disclosed the presence of protein with BCuNps. A comparative evaluation of BCuNps with copper sulphate to determine their antimicrobial and cell toxicity levels was undertaken. BCuNps showed better antimicrobial effect and found to be safer against normal cell lines, such as HaCat, Vero and hFOB, than the copper sulphate control. © 2016 Elsevier LtdItem 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 Biologically synthesized PbS nanoparticles for the detection of arsenic in water(Elsevier Ltd, 2017) Uddandarao, U.; Gowda K M, A.; M G, E.; Teja B, S.; Nitish, N.; Mohan B, R.Semiconductor nanoparticles have gained importance because of their interesting optical properties. Among these, lead sulfide (PbS) has been extensively studied due to its potential technological applications in field effect transistors, solar cells, photo-voltaics, light emitting diodes, photocatalysis, photo-luminescence, infrared photodetectors, environmental and biological sensors. Hence there is a need to explore cost effective and eco-friendly biological routes for their synthesis. In this paper, biosynthesis of PbS nanoparticles were carried out using endophytic fungi, subsequently detailed characterization was also performed using UV–visible, fluorescence spectrometer, FTIR, SEM, TEM, EDX and XRD. TEM revealed the formation of PbS nanoparticles in typical size range of 35–100 nm. The application of these nanoparticles for detection of arsenic in aqueous solution through their absorbance properties was also dealt. Importantly, the results were demonstrated for detection of 50 ppb As (III) in water without any interference of other selected ions maintained upto 20 ppb under same conditions. Further, the correlation for the bio-sensitivity of PbS nanoparticles based on the quenching effect with arsenic concentrations ranging between 10 and 100 ppb in water samples was deduced. © 2016 Elsevier LtdItem 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.