Mathur Gopalakrishnan Sethuraman

Corrosion inhibition of mild steel by Datura metel in acidic medium

Purpose – To evaluate the corrosion inhibition potential of Datura metel in acid medium on mild steel (MS) with a view to develop green corrosion inhibitors.Design/methodology/approach – Acid extract of the D. metel was studied for its corrosion inhibitive effect by electrochemical and weight loss methods. Using weight loss measurement data, an attempt has been made to probe the mechanism of inhibitive action by fitting adsorption isotherms.Findings – D. metel has been found to show significant corrosion inhibitive effect in acid medium on MS. Inhibition is through adsorption of the phytoconstituents on MS following Tempkin and Langmuir adsorption isotherms. The results of A.C. impedance and polarisation studies correlate well with the weight loss studies.Originality/value – The plant has been investigated for the first time for its corrosion inhibitive effect. The effect has been studied by proven methods. This green inhibitor can find use in the inhibition of corrosion in industries where MS is used as ...

Biogenic robust synthesis of silver nanoparticles using Punica granatum peel and its application as a green catalyst for the reduction of an anthropogenic pollutant 4-nitrophenol

A robust synthesis of silver nanoparticles (AgNPs) using the peel extract of Punica granatum is reported in this article. The formation of AgNPs was confirmed by the appearance of brownish yellow color and the Surface Plasmon Resonance (SPR) peak at 432 nm. The biogenic AgNPs were found to have the size approximately 30 nm with distorted spherical shape. The high negative zeta potential values of AgNPs revealed their high stability which could be attributed to the capping of AgNPs by the phytoconstituents of the Punica granatum peel. The biogenic AgNPs were also found to function as an effective green catalyst in the reduction of anthropogenic pollutant viz., 4-nitrophenol (4-NP) by solid sodium borohydride, which was evident from the instantaneous color change of bright yellow (400 nm) to colorless (294 nm) solution, after the addition of AgNPs. The catalytic action of biogenic AgNPs in the reduction of 4-NP could be explained on the basis of Langmuir-Hinshelwood model.

Green synthesis of silver nanoparticles using Terminalia cuneata and its catalytic action in reduction of direct yellow-12 dye

Facile green synthesis of silver nanoparticles (AgNPs) using aqueous bark extract of Terminalia cuneata has been reported in this article. The effects of concentration of the extract, reaction time and pH were studied by UV-Vis spectroscopy. Appearance of yellow color with λmax around ~420 nm suggested the formation of AgNPs. The stable AgNPs were further characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) with zeta potential and high resolution transmission electron microscopy (HR-TEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The synthesized AgNPs were in the size range of 25-50 nm with a distorted spherical shape identified from HR-TEM analysis. The catalytic activity of AgNPs on the reduction of direct yellow-12 using NaBH4 was analyzed using a UV-Vis spectrophotometer. This study showed the efficacy of biogenic AgNPs in catalyzing the reduction of direct yellow-12.

Microwave assisted green synthesis of fluorescent N-doped carbon dots: Cytotoxicity and bio-imaging applications

A fast and facile microwave approach for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) is reported. The N-CDs were hydrothermally synthesized using l-ascorbic acid (AA) and β-alanine (BA) as the carbon precursor and the nitrogen dopant, respectively. The morphology of synthesized N-CDs was characterized by high resolution transmission electron microscopy (HR-TEM) and the elemental composition was analyzed using elemental mapping method. The crystallinity and graphitation of N-CDs were examined by X-ray diffraction (XRD) and Raman spectroscopy. The doping of nitrogen over the carbon dots (CDs) was revealed by attenuated total reflection conjunction with Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photo electron spectroscopy (XPS). The optical properties of synthesized N-CDs were examined by UV-Visible (UV-Vis) and fluorescence spectroscopy. The synthesized N-CDs emit strong blue fluorescence at 401nm under excitation of 325nm. The excitation dependent emission property of synthesized N-CDs was exposed from fluorescence results. The quantum yield of synthesized N-CDs is about 14% against the reference quinine sulfate. The cytotoxicity of synthesized N-CDs on Madin-Darby Canine Kidney (MDCK) and HeLa cells were evaluated through Cell Counting Kit-8 (CCK-8) cytotoxicity assay. The results implied that the fluorescent N-CDs showed less cytotoxicity, further which was successfully applied as a staining probe for the confocal imaging of MDCK and HeLa cells.

Inhibition of corrosion of mild steel in sulphuric acid medium by Calotropis procera

Purpose – The purpose of this paper is to evaluate the corrosion inhibition potential of Calotropis procera in sulphuric acid medium on mild steel with a view to developing green corrosion inhibitors.Design/methodology/approach – Extract of the C. procera was studied for its corrosion inhibitive effect by weight loss, electrochemical, SEM and UV methods. Using weight loss measurement data, mechanism of inhibitive action is probed by fitting in adsorption isotherm.Findings – C. procera has been found to show significant corrosion inhibitive effect in sulphuric acid medium on mild steel. Inhibition is through adsorption of the phytoconstituents on mild steel following Tempkin adsorption isotherm. The results of ac impedance and polarization studies correlate well with the weight loss studies.Originality/value – The plant has been investigated for the first time for its corrosion inhibitive effect. The effect has been studied by proven methods. This green inhibitor can find use in the inhibition of corrosion...

Reductive-degradation of carcinogenic azo dyes using Anacardium occidentale testa derived silver nanoparticles

In the present work, reductive-degradation of azo dyes such as congo red (CR) and methyl orange (MO) was manifested using Anacardium occidentale testa derived silver nanoparticles (AgNPs) as a catalyst. The formation of highly stable AgNPs were visually confirmed by the appearance of yellow color and further substantiated by the existence of surface plasmon resonance (SPR) peak around 425nm. The effect of A. occidentale concentration, reaction time and pH in the formations of AgNPs was corroborated by UV-visible (UV-Vis) spectroscopy. The Fourier transform infrared (FT-IR) spectroscopic results proved that phytoconstituents of A. occidentale testa acts as a capping agent and thereby protects the AgNPs from aggregation. The crystalline nature of the AgNPs was validated from the XRD patterns. The average size of synthesized AgNPs was 25nm, with distorted spherical shape was ascribed from the high resolution transmission electron microscopic (HR-TEM) images. Due to the high stability of the as-synthesized AgNPs, they were utilized for the degradation of carcinogenic azo dyes such as CR and MO using NaBH4 and its catalytic activity was studied via UV-Vis spectroscopy. The results proved that extraordinary catalytic activity of synthesized AgNPs towards the reductive-degradation of both CR and MO.

STUDIES ON THE INHIBITIVE EFFECT OF DATURA STRAMONIUM EXTRACT ON THE ACID CORROSION OF MILD STEEL

The extract of Datura stramonium has been studied as a possible source of green inhibitor for corrosion of mild steel (MS) in HCl and H2SO4 media at different temperatures. The anticorrosion effect was evaluated by conventional weight loss studies, electrochemical studies viz., Tafel polarization, ac impedance, and SEM studies. The studies reveal that the plant extract acts as a good inhibitor in both the acid media and better in H2SO4 medium. Tafel polarization method indicate that the plant extract behaves as a mixed mode inhibitor. Double layer capacitance and charge transfer resistance values derived from Nyquist plots obtained from ac impedance studies give supporting evidence for the anticorrosive effect. The inhibitive effect may be attributed to the adsorption of the inhibitor on the surface of MS, following Temkin adsorption isotherm. Increase of inhibition efficiency with increase of temperature along with Ea values serve as a proof for chemisorption. SEM studies provide the confirmatory evidence for the protection of MS by the green inhibitor. The study reveals the potential of D. stramonium for combating corrosion which may be due to the adsorption of alkaloids and other phytoconstituents.

Fabrication of copper-based superhydrophobic self-cleaning antibacterial coating over cotton fabric

A superhydrophobic cotton fabric exhibiting excellent self-cleaning and antibacterial activity prepared by a facile, cost-effective method involving deposition of copper and stearic acid has been reported in this article. The surface morphology and microstructure of the modified fabric have been characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis and X-ray photoelectron spectroscopy. The antibacterial activity of the as-prepared superhydrophobic textiles has been evaluated by the disc diffusion method using Gram-positive and Gram-negative microorganisms. Evaluation of the modified fabric by a simple washing method and immersion in media of various pH values revealed the durability of the superhydrophobic textiles. In view of the robustness of this technique, it is certain that textiles with the dual functionalities of superhydrophobicity and antibacterial activity could be developed by this method and exploited in application domains in the years to come.

Biological and catalytic applications of green synthesized fluorescent N-doped carbon dots using Hylocereus undatus

In this work, a simple hydrothermal route for the synthesis of fluorescent nitrogen doped carbon dots (N-CDs) is reported. The Hylocereus undatus (H. undatus) extract and aqueous ammonia are used as carbon and nitrogen source, respectively. The optical properties of synthesized N-CDs are analyzed using UV-Visible (UV-Vis) and fluorescence spectroscopy. The surface morphology, elemental composition, crystallinity and functional groups present in the N-CDs are examined using high resolution transmission electron microscopy (HR-TEM) with energy dispersive spectroscopy (EDS), selected area electron diffraction (SAED), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, respectively. The synthesized N-CDs emit strong blue fluorescence at 400nm under the excitation of 320nm. Further, the excitation dependent emission properties are also observed from the fluorescence of synthesized N-CDs. The HR-TEM results reveal that synthesized N-CDs are in spherical shape with average diameter of 2.5nm. The XRD pattern exhibits, the graphitic nature of synthesized N-CDs. The doping of nitrogen is confirmed from the EDS and FT-IR studies. The cytotoxicity and biocompatibility of N-CDs are evaluated through MTT assay on L-929 (Lymphoblastoid-929) and MCF-7 (Michigan Cancer Foundation-7) cells. The results indicate that the fluorescent N-CDs show less cytotoxicity and good biocompatibility on both L-929 and MCF-7 cells. Moreover, the N-CDs show excellent catalytic activity towards the reduction of methylene blue by sodium borohydride.

Corrosion Inhibitory Effect Of Few Piperidin-4-One Oximes On Mild Steel In Hydrochloric Acid Medium

Three piperidin-4-one oxime derivatives viz. 3,5-dimethyl-2,6-diphenyl-piperidin-4-one oxime (DDPO), 3-ethyl-2,6-diphenyl-piperidin-4-one oxime (EDPO), and 1-methyl-3-isopropyl-2, 6-diphenyl-piperidin-4-one oxime (MIDPO) were synthesized. Corrosion inhibiting ability of these compounds in 1 M HCl was studied using weight loss study, potentiodynamic polarization measurements, electrochemical impedance spectroscopy, XRD and SEM with EDS measurements. Weight loss studies revealed that all the three oximes are good corrosion inhibitors. The order of inhibiting ability of these compounds is as follows: DDPO > EDPO > MINDO. Results of the polarization measurement showed that these inhibitors do not alter the mechanism of either hydrogen evolution or mild steel dissolution reaction, proving the mixed mode of inhibition. At constant acid concentration, increase of inhibitor concentration increased the charge transfer resistance (Rct), complimented with decrease of double layer capacitance (Cdl), thereby indicating the increase of percentage inhibition efficiency. XRD and SEM with EDS analysis provided strong proof for the existence of inhibitor film over the mild steel surface.