Showing papers by "Kuvempu University published in 2019"

Green synthesis of Zinc oxide nanoparticles (ZnO NPs) and their biological activity

Abstract: Zinc oxide (ZnO) has broad applications in various areas. Green synthesis is an alternative to conventional physical and chemical methods. Green synthesis of nanoparticles is gaining importance due to its cost-effectiveness, reduction of toxic chemicals and extensive antimicrobial activity. Herein, we have discovered synthesis of zinc oxide nanoparticles (ZnONPs) using agro waste materials like sheep and goat faecal matter as a reducing agent. Synthesized ZnONPs were evaluated for their purity, particle size, morphological structure, using UV–visible spectroscopy, Fourier transforms infrared spectroscopy, X-ray diffraction and scanning electron microscope analysis. However, nanoparticles gain low crystallite size, they seemed to be uneven structures like spongy like and flower shaped particles. Obtained nanoparticles exhibit good antimicrobial activity and minimum inhibitory concentration against Salmonella typhimurium and Bacillus subtilis. Agro-waste based green synthesized ZnONPs possess small sized particles, enhances the good antimicrobial effect. This research leads to develop a new way of cost-effective synthesis and reducing usage of chemicals in further studies.

Probiotic Properties of Lactic Acid Bacteria Isolated From Neera: A Naturally Fermenting Coconut Palm Nectar.

Abstract: Probiotic bacteria were isolated from different traditional fermented foods as there are several such foods that are not well explored for their probiotic activities. Hence, the present study was conducted to find the potential of lactic acid bacteria (LAB) as probiotics that were isolated from the sap extract of the coconut palm inflorescence - Neera, which is a naturally fermented drink consumed in various regions of India. A total of 75 isolates were selected from the Neera samples collected aseptically in the early morning (before sunrise). These isolates were initially screened for cultural, microscopic, and biochemical characteristics. The initial screening yielded 40 Gram-positive, catalase-negative isolates that were further subjected to acid - bile tolerance with resistance to phenol. Among 40 isolates, 16 survived screening using analysis of cell surface hydrophobicity, auto aggregation with adhesion to epithelial cells, and gastric-pancreatic digestion for gastrointestinal colonization. The isolates were also assessed for antimicrobial, antibiotic sensitivity, and anti-oxidative potential. The safety of these isolates was evaluated by their hemolytic and deoxyribonuclease (DNase) activities. Based on these results, seven isolates with the best probiotic attributes were selected and presented in this study. These LAB isolates, with 51.91-70.34% survival at low pH, proved their resistance to gastric conditions. The cell surface hydrophobicity of 50.32-77.8% and auto aggregation of 51.02-78.95% represented the adhesion properties of these isolates. All the seven isolates exhibited good antibacterial and antifungal activity, showing hydroxyl-scavenging activity of 32.86-77.87%. The results proved that LAB isolated from Neera exhibited promising probiotic properties and seem favorable for use in functional fermented foods as preservatives.

Green synthesis of zinc doped cobalt ferrite nanoparticles: Structural, optical, photocatalytic and antibacterial studies

Abstract: The nanostructured zinc-doped cobalt ferrites (Zn x Co 1−x Fe2O4 where x ranges from 0.0 to 0.6 with the step of 0.2) were prepared by combustion method using curd as a green fuel. The prepared nanoparticles were further characterized using XRD, SEM with EDAX, TEM, FTIR, UV-DRS, and luminescence spectroscopy. From the XRD, it shows that these nanomaterials exhibit average crystallite size in the range ∼ 12-21 nm with inverse cubic spinel structure. The agglomerated and spherical structure of the nanoparticles is confirmed by SEM and TEM. The vibrational stretching modes of tetrahedral (582 cm−1) and octahedral (385 cm−1) sites were confirmed by FTIR. Further, density functional theory (DFT) analysis was carried out in order to study the electronic properties of cobalt ferrite and zinc-doped cobalt ferrite nanostructures. The band gap results for pure CoFe2O4 and Zn-doped CoFe2O4 nanoparticles were closer to the experimental values. The luminescence spectrum shows peaks correspond to violet, blue, green, yellow and orange emission. The photodegradation studies of obtained nanoparticles were evaluated for the degradation of Congo red and Evans blue dyes under visible light irradiation. Pure CoFe2O4 and Zn-doped CoFe2O4 nanoparticles were inspected against both gram-positive (Staphylococcus aureus) and the gram-negative (Salmonella typhi) bacteria for antibacterial studies. The gram-negative bacterium Salmonella typhi shows high antibacterial activity with the inhibition zone of Zn-doped CoFe2O4 (22 mm) compared to pure CoFe2O4 (16 mm)

An environmental friendly attempt to recycle the spent Li-ion battery cathode through organic acid leaching

Abstract: An environmentally friendly hydrometallurgical leaching process for the recovery of metal ions from the cathode active materials of spent lithium-ion batteries was investigated. The spent LIBs were first dismantled and separated by physical separation. The powder obtained after physical separation was subjected for leaching using easily degradable organic acids like nitrilotriacetic acid, adipic acid, and ascorbic acid. The leaching proceeds with a reductive-complexing mechanism and leaching occurs in about 6 h. The leaching rate constants (k) for Li and Co ions were determined by ‘cubic rate law’ plots. The formation of Co(III)– to Co(II)–Ligand during the leaching is confirmed from the UV–Vis spectra. The structural, morphology of the cathode materials before and after leaching was characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The amount of lithium and cobalt present in the leachate was determined by atomic absorption spectrophotometry (AAS). The presence of ascorbic acid in adipic acid solution is an active reducing agent compared to ascorbic acid in nitrilotriacetic acid solution because it enhances the leaching efficiency.

Microwave-Assisted ZrO2 Nanoparticles and Its Photocatalytic and Antibacterial Studies

Abstract: ZrO2 nanoparticles were prepared by the microwave-assisted method. XRD, FTIR, FESEM with EDS, TEM, UV–Vis, and photoluminescence were used for the characterization of ZrO2 nanoparticles. XRD exhibits cubic structure with an average crystallite size of 12 nm. FESEM and TEM images confirm the nanoparticles with an average particle size of 35 nm. From FTIR results, the characteristic vibrational band (Zr–O) is observed at 735 cm−1. The optical bandgap of the microwave-assisted ZrO2 nanoparticles is found to be 4.42 eV. The photoluminescence spectrum of ZrO2 nanoparticles showed blue, green and orange emissions. The photocatalytic degradation study of ZrO2 nanoparticles was investigated against the Methylene Blue (MB) and Rose Bengal (RB) dyes under UV light irradiation. Microwave-assisted ZrO2 nanoparticles showed an excellent photocatalytic activity (MB and RB dye) monitored by using UV–Vis spectrophotometer. Antibacterial activity (disc diffusion method) of microwave-assisted ZrO2 nanoparticles was studied against foodborne pathogens. Furthermore, microwave-assisted ZrO2 nanoparticles will be applicable to wastewater remediation and pharmaceutical applications.

CuO/ZnO/g-C3N4 heterostructures as efficient visible light-driven photocatalysts

Abstract: Photocatalytic degradation of organic pollutants is an environmentally friendly technique for water treatment. In this work, CuO/ZnO/g-C3N4 heterostructure is prepared via solution combustion route to take advantage of the porous structure which is resulted from releasing the gases during the combustion. XRD, EDX, TEM, XPS, and TEM analyses confirm the successful construction of CuO/ZnO/g-C3N4 heterostructure. SEM images reveal that the as-prepared heterostructure consists of flower-like nanosheets decorated with nanoparticles. The CuO/ZnO/g-C3N4 heterostructure exhibits improved photocatalytic activity for methylene blue (MB) degradation in comparison to the CuO/ZnO system under visible light irradiation. At optimal experimental conditions, about 98% of MB is degraded within 45 min. Moreover, about 91% of ammonia- nitrogen is degraded after 6 h visible light illumination. The enhanced photocatalytic activity is attributed to the improved redox potential of the photocatalyst and efficient electrons and holes separation induced by the Z-scheme charge carrier transfer.

Thermal analysis of nanofluid flow containing gyrotactic microorganisms in bioconvection and second-order slip with convective condition

Abstract: Bioconvection in magneto-nanoliquid embedded with gyrotactic microorganisms across an elongated sheet with velocity slip of second order is addressed. Nonlinear thermal radiation and chemical reaction aspects are retained in energy and concentration equations. Numerical simulations for the modeled problem are proposed via Runge–Kutta–Fehlberg-based shooting technique. Special attention is given to the impact of involved parameters on the profiles of motile microorganisms, nanoparticle volume fraction, temperature and velocity. Our simulations figured out that assisting flow generates more heat transfer than the opposing flow situation. The motile microorganism’s boundary layer decayed for higher bioconvection Peclet and bioconvection Lewis numbers.

Entropy generation and heat transport analysis of Casson fluid flow with viscous and Joule heating in an inclined porous microchannel

Abstract: The combined effects of the magnetic field, suction/injection, and convective boundary condition on heat transfer and entropy generation in an electrically conducting Casson fluid flow through an i...

Facile synthesis of CoFe 2 O 4 nanoparticles and application in removal of malachite green dye

Abstract: The adsorption capacity of the surface of cobalt ferrite (CoFe2O4) nanoparticles as an adsorbent was investigated. Malachite green dye in aqueous solution was used as the model compound. Various do...

Multifunctional properties of microwave-assisted bioengineered nickel doped cobalt ferrite nanoparticles

Abstract: Nickel-doped cobalt ferrite nanoparticles based on Andrographis paniculata plant extract were prepared through the microwave-assisted method. The obtained nanoparticles were analyzed using XRD, FTIR, UV-DRS, SEM with EDAX, and HRTEM with SAED. XRD exhibits a cubic lattice structure of ferrites and the lattice parameter decreases with an increase in nickel dopant. The vibrational stretching mode of the metal–oxygen bond is observed for tetrahedral and octahedral sites. The optical energy bandgap of pure CoFe2O4 nanoparticles gradually increases with nickel doping. The luminescence spectrum showed the violet, yellow, green, and orange emissions of synthesized nanoparticles. Further, photodegradation of prepared nanoparticles was assessed for the degradation of Methylene blue, Rhodamine B, Eriochrome black T, Rose bengal, and Evan’s blue dyes. Antibacterial activity of synthesized nanoparticles was tested against Gram-positive and Gram-negative bacterial strains. The antibacterial activity improved with Ni doping when compared with pure CoFe2O4 nanoparticles.

Developments in taxol production through endophytic fungal biotechnology: a review

Abstract: Paclitaxel (taxol), a diterpene natural compound was first extracted from the bark of yew trees. However, the method cannot meet its increasing demand on the market due to unprecedented yew cutting, low amounts of taxol production, the laborious and slow process of taxol extraction. Recently, efforts have been made to develop alternative means of taxol production. Microbial fermentation would be a promising method in the production of taxol at industrial scale. Fungal endophytes have the capacity to produce bioactive compounds and can independently synthesize secondary metabolites similar to those made by the host plants. Optimization of the fermentation culture is one of the most important strategies in increasing taxol production by endophytic fungi supplemented with several substances including carbon sources, nitrogen sources, precursors, inducer and the metabolic bypass inhibitors. Improved fermentation techniques and different biotechnological strategies such as gene cloning, gene transformation, mutations are widely being used on endophytic fungi in order to increase the productivity of the taxol. In this review, the different strategies used to produce taxol from endophytic fungal biotechnology have been discussed.

Highly porous, honeycomb like Ag–ZnO nanomaterials for enhanced photocatalytic and photoluminescence studies: green synthesis using Azadirachta indica gum

Abstract: The preparation of zinc oxide and silver doped zinc oxide nanoparticles using zinc nitrates and silver nitrates as oxidizers and Azadirachta indica gum as a fuel via solution combustion method at 500 °C. The synthesized nanoparticles were characterized by XRD, FTIR, UV-DRS, SEM and TEM studies; these materials were tested for photoluminescence and photocatalytic activity studies. The PXRD data indicated that the synthesized nanoparticles confirmed as hexagonal phase with average crystallite size of 13.33 and 13.34 nm for ZnO and Ag–ZnO respectively. The SEM data revealed that, the material obtained is highly porous and honeycomb like structure. In the photocatalytic degradation of methylene blue, Ag–ZnO nanoparticles have shown the good photocatalytic activity than undoped ZnO nanoparticles. This is due to the presence of Ag on the surface of ZnO catalyst makes the catalyst more sensitive to light and reduce the electron hole recombination. Furthermore, we have also examined the photoluminescence studies for the synthesized materials and it has given the green emission by excitation at 380 nm. In this study, the green synthesis method will produces large quantity of nanomaterials with less time and low cost.

Study on the effect of Zn2+ doping on optical and electrical properties of CuO nanoparticles

Abstract: The present work outlines the synthesis of CuO and Zn-CuO nanoparticles via microwave combustion method using urea as a fuel. The structural, optical and electrical properties of the CuO and Zn-CuO nanoparticles were systematically characterized through UV–Visible spectroscopy (UV–Vis), Field-emission scanning electron microscopy (FE-SEM), Photoconductivity technique (I-V study), X-ray diffraction studies (XRD), Transmission electron microscopy (TEM) and Energy dispersive analysis X-rays spectrometer (EDAX). The average crystalline size and micro-strain of pure CuO and Zn-CuO nanoparticles were calculated using Debye-Scherrer and William-Hall (W-H) plot methods. The crystalline size was found to be decreased with increase in the concentration of Zn 2+ up to 6 mol% and a further increase in the Zn2+ concentration resulted in the formation impurity phase. Field emission scanning electron micrographs show the monoclinic rod-like structure of CuO and Zn-CuO nanoparticles. Energy dispersive X-ray spectra display the existence of Zn2+ in Zn-CuO nanoparticles. The optical band gap values of CuO and Zn-CuO nanoparticles were determined by optical absorption method and the results show a slight decrease in the optical band gap with Zn 2+ doping. Electrical properties of CuO and Zn-CuO films were performed using I-V characterization studies and the results shown that the enhancement of photocurrent is more in UV-light as compared to dark.

η-Ricci solitons and almost η-Ricci solitons on para-Sasakian manifolds

Abstract: In this paper, we study para-Sasakian manifold (M,g) whose metric g is an η-Ricci soliton (g,V ) and almost η-Ricci soliton. We prove that, if g is an η-Ricci soliton, then either M is Einstein and...