Browsing by Author "Varma, Rajender S."

Now showing 1 - 7 of 7
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    Bioplastic Fibers from Gum Arabic for Greener Food Wrapping Applications
    (AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, 2019-03-18) Padil, Vinod V. T.; Senan, Chandra; Waclawek, Stanislaw; Černík, Miroslav; Agarwal, Seema; Varma, Rajender S.
    The fabrication of bioplastic fibers from gum arabic (GA), a natural tree gum exudate, is described via the electrospinning method. The enrichment in surface properties of this bioplastic fiber was evaluated by methane plasma and gamma-ray irradiation treatments. The fibers with their modified forms, both treated and untreated, were investigated by various characterization techniques such as scanning electron microscopy, atomic force microscopy, X-ay diffraction and attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, BET surface area, water contact angle, and tensile strength measurements. A switchable hydrophobic/hydrophilic functionality on GA bioplastic fibers was established through CH4 plasma and gamma-ray irradiation treatments; higher water contact angle (130 degrees) was observed in GA bioplastic fibers that had undergone methane plasma treatment. However, the untreated and gamma-ray-irradiated GA bioplastics exhibited hydrophilic behavior. The comparative properties such as water resistance, antioxidant potency, gas barrier attributes, antibacterial effectiveness, biodegradability and food contact migration through the GA bioplastic fibers (untreated, plasma treated, and gamma-ray-irradiated) were assessed. The present work, in contrast to other existing bioplastic fibers, has the potential of becoming a viable option in greener food packaging as well as in environmental and medically related products based on tree gums.
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    Greener assembling of MoO3 nanoparticles supported on gum arabic: cytotoxic effects and catalytic efficacy towards reduction of p-nitrophenol
    (2019-01-01) Kothaplamoottil Sivan, Saranya; Padinjareveetil, Akshay K.K.; Padil, Vinod V. T.; Pilankatta, Rajendra; George, Bini; Senan, Chandra; Černík, Miroslav; Varma, Rajender S.
    An economical and easy one-step method for the biosynthesis of highly stable molybdenum trioxide (MoO3) nanoparticles was developed using gum arabic as a bio-template; ensuing nanoparticles (NP) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV–visible spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The crystallinity and purity of MoO3 nanoparticles in the orthorhombic phase were confirmed by XRD analysis, and their rod-shaped identity (average sizes ranging from 7.5 to 42 nm) were observed by TEM. Cytotoxic effects of the NP were monitored using Hep G2 (human liver cancer) and HEK 293 (human embryonic kidney) cell lines via 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assays. The results of this study revealed that MoO3 nanoparticles are nontoxic towards Hep G2 cell lines and displayed negligible toxicity, even at very high concentrations (1000 ppm), although had moderate toxicity towards HEK 293 cells. Furthermore, their catalytic activity was evaluated for the reduction of p-nitrophenol to p-aminophenol. Graphical abstract: Synopsis: Green synthesis of MoO3 nanorods using gum arabic demonstrated as an eco-friendly catalyst for the conversion of p-nitrophenol with negligible toxicity towards Hep G2 cell lines.[Figure not available: see fulltext.].
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    Gum Kondagogu/Reduced Graphene Oxide Framed Platinum Nanoparticles and Their Catalytic Role
    (MDPI, 2019-10-01) Venkateshaiah, Abhilash; Silvestri, Daniele; Ramakrishnan, Rohith K; Wacławek, Stanislaw; Padil, Vinod V. T; Černík, Miroslav; Varma, Rajender S.
    This study investigates an environmentally benign approach to generate platinum nanoparticles (Pt NP) supported on the reduced graphene oxide (RGO) by non-edible gum waste of gum kondagogu (GK). The reaction adheres to the green chemistry approach by using an aqueous medium and a nontoxic natural reductant-GK-whose abundant hydroxyl groups facilitate in the reduction process of platinum salt and helps as well in the homogenous distribution of ensued Pt NP on RGO sheets. Scanning Electron Microscopy (SEM) confirmed the formation of kondagogu gum/reduced graphene oxide framed spherical platinum nanoparticles (RGO-Pt) with an average particle size of 3.3 ± 0.6 nm, as affirmed by Transmission Electron Microscopy (TEM). X-ray Diffraction (XRD) results indicated that the Pt NPs formed are crystalline with a face-centered cubic structure, while morphological analysis by XRD and Raman spectroscopy revealed a simultaneous reduction of GO and Pt. The hydrogenation of 4-nitrophenol could be accomplished in the superior catalytic performance of RGO-Pt. The current strategy emphasizes a simple, fast and environmentally benign technique to generate low-cost gum waste supported nanoparticles with a commendable catalytic activity that can be exploited in environmental applications.
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    Microscopic Techniques for the Analysis of Micro and Nanostructures of Biopolymers and Their Derivatives
    (MDPI, 2020-03-01) Venkateshaiah, Abhilash; Padil, Vinod V. T.; Nagalakshmaiah, Malladi; Waclawek, Stanislaw; Černík, Miroslav; Varma, Rajender S.
    Natural biopolymers, a class of materials extracted from renewable sources, is garnering interest due to growing concerns over environmental safety; biopolymers have the advantage of biocompatibility and biodegradability, an imperative requirement. The synthesis of nanoparticles and nanofibers from biopolymers provides a green platform relative to the conventional methods that use hazardous chemicals. However, it is challenging to characterize these nanoparticles and fibers due to the variation in size, shape, and morphology. In order to evaluate these properties, microscopic techniques such as optical microscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM) are essential. With the advent of new biopolymer systems, it is necessary to obtain insights into the fundamental structures of these systems to determine their structural, physical, and morphological properties, which play a vital role in defining their performance and applications. Microscopic techniques perform a decisive role in revealing intricate details, which assists in the appraisal of microstructure, surface morphology, chemical composition, and interfacial properties. This review highlights the significance of various microscopic techniques incorporating the literature details that help characterize biopolymers and their derivatives.
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    Microwave-assisted sustainable co-digestion of sewage sludge and rapeseed cakes
    (Elsevier Ltd, 2019-11-01) Grübel, Klaudiusz; Kuglarz, Mariusz; Wacławek, Stanisław; Vellora Thekkae Padil, Vinod; Černík, Miroslav; Varma, Rajender S.
    The technological concept ensuring highly efficient co-digestion of by-products from the production of biodiesel and sewage sludge was examined. Rapeseed cakes (RC) 1–5% addition to waste activated sludge (WAS) 95–99% in digesters, positively influenced the degree of biodegradation of organic matter and the quantity and quality of the biogas produced. Under the optimal conditions (HRT = 20–22 days), the co-digestion mixtures (WAS + microwave disintegration + RC) generated double the amount of biogas, containing approximately 10–12% more CH4, than the samples which had the sewage sludge only. Under these conditions, the biogas yield increased by approximately 48–82% depending on the co-substrate used and was further improved via the introduction of microwave pre-treatment. After testing at the pilot scale, this method could be considered as a sustainable alternative to conventional methods for WAS and RC treatment.
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    Recycling non-food-grade tree gum wastes into nanoporous carbon for sustainable energy harvesting
    (ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND, 2020-02-21) Venkateshaiah, Abhilash; Cheong, Jun Young; Shin, Sung-Ho; Akshaykumar, K. P.; Yun, Tae Gwang; Bae, Jaehyeong; Waclawek, Stanislaw; Černík, Miroslav; Agarwal, Seema; Greiner, Andreas; Padil, Vinod V. T.; Kim, Il-Doo; Varma, Rajender S.
    The disposal of natural wastes has become a global problem and the use of lower-grade gums is very limited owing to their impurities as well as sticky nature. Rather than disposing these wastes, nanoporous carbon (nC) has instead been synthesized by carbonization and exfoliation. The synthesized nC exhibits a substantially high surface area along with abundant micro/mesopores. This desirable and useful nature of nC is well-suited for water-driven effective electrical energy conversion, which enables the fast evaporation of water via a capillary action through nanopores. Under asymmetric wetting in a water container and ambient conditions, the nC-based energy harvesters showed high capability of electricity production and reliable output generation, easily turning on a blue light-emitting diode (2.5 V and 20 mA) using a stored power source. In summary, many energy harvesters can be manufactured for the scale-up of electricity, and the suitability of regenerated carbon nanomaterials for green energy harvesting can contribute toward alleviating chronic environmental issues.
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    Synthesis of Ag nanoparticles by a chitosan-poly(3-hydroxybutyrate) polymer conjugate and their superb catalytic activity
    (Elsevier Ltd, 2020-01-01) Silvestri, Daniele; Wacławek, Stanisław; Venkateshaiah, Abhilash; Krawczyk, Kamil; Sobel, Bartłomiej; Padil, Vinod V.T.; Černík, Miroslav; Varma, Rajender S.
    This work describes an eco-friendly and sustainable technique for the synthesis of silver nanoparticles (nAg), where chitosan-poly(3-hydroxybutyrate) polymer conjugate (Chit-PHB) acts as a reducing and stabilizing material. The ensuing nanoparticles show an exceptional catalytic activity in the reduction of 4-nitrophenol to 4-aminophenol. nAg were characterized by several techniques, i.e. SEM and TEM-EDX, to confirm their production, size and morphology. Furthermore, infrared spectroscopy analysis proved the presence of a Chit-PHB coating on the nAg. The excellent catalytic properties of the nAg-Chit-PHB was discernible when the activity parameter (κc) normalized by the specific surface area (SSA) of the nanoparticles was taken into consideration; normalization of κc by the SSA is a vital parameter for the assessment of the accessibility to the surface area of particles. Herein synthesized Ag nanoparticles, as far as we know, exhibited the fastest reaction kinetics of 4-nitrophenol reduction compared to the silver nanoparticles reported in the literature