Ashina, C., Pugazhenthiran, N., Sathishkumar, P., Selvaraj, M., Assiri, M. A., Rajasekaran, C., et al. (2023). Ultra-small Ni@NiFe2O4/TiO2 magnetic nanocomposites activated peroxymonosulphate for solar light-driven photocatalytic mineralization of Simazine. J. Environ. Chem. Eng., 11(6), 111342.
Abstract: In the heterogeneous photocatalytic degradation of environmental contaminants the recovery, reuse of employed nanocatalyst was crucial and it is essentially required for the scale up applications. Besides, designing a magnetic material with heterojunction that can effectively oxidize the toxic organic contaminants to non-toxic substance under different reaction conditions including direct solar light irradiation remains a challenge. Considering the above facts, herein, we tailored heterojunction between the magnetic materials and non-magnetic materials with ultra-small Ni nanoparticles modified NiFe2O4/TiO2 nanostructures (Ni@NiFe2O4/TiO2 magnetic nanocomposites) through a simple sonochemical route. The Raman phonons at similar to 540 cm(-1) consistent to nickel metal nanoparticles and the spinel ferrites crystal structure confirmed the formation of Ni@NiFe2O4/TiO2 magnetic nanocomposites. The reduced optical bandgap of the resulting nanocomposites indicated the effective absorption of direct solar light irradiation when compared to the bare TiO2. Thus in-turn, enhanced the photocatalytic efficiency of simazine degradation in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k= 11.0 x 10(-4) s(-1)) and augmented the activation of peroxymonosulphate (PMS) in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k= 32.5 x 10(-4) s(-1)). Ni@NiFe2O4/TiO2 +PMS exhibited 3 folds enhanced efficiency in the presence of sunlight. The as-prepared NiFe2O4/TiO2 magnetic nanocatalysts were more stable and the efficiency of simazine oxidation was approximately same for the continuous five cycles at the optimized experimental conditions. The Ni@NiFe2O4/TiO2 magnetic nanocomposites preparation and the activation of PMS may promise the applications in an efficient wastewater treatment.
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Pugazhenthiran, N., Sathishkumar, P., Albormani, O., Murugesan, S., Kandasamy, M., Selvaraj, M., et al. (2023). Silver nanoparticles modified ZnO nanocatalysts for effective degradation of ceftiofur sodium under UV-vis light illumination. Chemosphere, 313, 137515.
Abstract: Light-induced photocatalytic degradation of ceftiofur sodium (CFS) has been assessed in the presence of plas-monic zinc oxide nanostructures (ZnONSTs), like, ZnO nanoparticles, ZnO nanorods (ZnONRs) and ZnO nano -flowers (ZnONFs). Silver nanoparticles (Ag NPs) loaded ZnO nanostructures (Ag-ZnONSTs) are obtained through seed-assisted chemical reaction followed by chemical reduction of silver. The surface modification of ZnO nanostructures by Ag NPs effectually altered their optical properties. Further, the surface plasmonic effect of Ag NPs facilitates visible light absorption by ZnONSTs and improved the photogenerated electron and hole separation, which makes the ZnONSTs a more active photocatalyst than TiO2 (P25) nanoparticles. Especially, Ag-ZnONRs showed higher CFS oxidation rate constant (k' = 4.6 x 10-4 s-1) when compared to Ag-ZnONFs (k' = 2.8 x 10-4 s-1) and Ag-ZnONPs (k' = 2.5 x 10-4 s-1), owing to their high aspect ratio (60:1). The unidirectional transport of photogenerated charge carriers on the Ag-ZnONRs may be accountable for the observed high photocatalytic oxidation of CFS. The photocatalytic oxidation of CFS mainly proceeds through center dot OH radicals generated on the Ag-ZnONRs surface under light illumination. In addition, heterogeneous activation of perox-ymonosulfate by Ag-ZnONRs accelerates the rate of photocatalytic mineralization of CFS. The quantification of oxidative radicals supports the proposed CFS oxidation mechanism. Stability studies of plasmonic Ag-ZnONSTs strongly suggests that it could be useful to clean large volume of pharmaceutical wastewater under direct solar light irradiation.
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Pugazhenthiran, N., Valdes, H., Mangalaraja, R. V., Sathishkumar, P., & Murugesan, S. (2022). Graphene modified “black {001}TiO2” nanosheets for photocatalytic oxidation of ethylene: The implications of chemical surface characteristics in the reaction mechanism. Sep. Purif. Technol., 292, 121008.
Abstract: In this work, crystal facets, bandgap, size and shape of reduced graphene oxide (rGO) modified anatase {001} black TiO2 nanosheets (rGO-B-TiO2 NSTs) were tailored for the photocatalytic oxidation of ethylene under high humidity content. XRD, Raman and HR-TEM analyses confirm that rGO-B-TiO2 NSTs have a 94 % of exposed {001} facets with high number of oxygen vacancies. In addition, rGO-B-TiO2 NSTs exhibit increased values of surface area and porosity compared to its pristine form. A 48 and 34 mu mol g(-1) of ethylene are adsorbed at the surface of rGO-B-TiO2 NSTs in the absence and in the presence of humidity, respectively. In addition, operando DRIFTS analyses provide the insight of surface interactions between ethylene molecules and adsorption sites of rGO-B-TiO2 NSTs. The photocatalytic removal efficiencies of the synthesized materials under both UV and visible light irradiation proceed as follows: rGO-B-TiO2 NSTs > B-TiO2 NSTs > TiO2 NSTs > commercial TiO2 NPs. Further, ethylene is very quickly photocatalytic oxidized when rGO-B-TiO2 NSTs is applied under UV light irradiation, having a 72 and 92 % ethylene removal in the absence and in the presence of humidity, respectively. Moreover, a 48 and 58 % of ethylene removal takes place in the absence and presence of humidity under visible light irradiation, respectively. Results indicate that rGO-B-TiO2 NSTs boost the photocatalytic activity through their virtue of visible-light absorption properties (Bandgap = 2.61 eV) and the rapid electron-hole separation at the rGO {0 0 1} black TiO2 NSTs interfaces. Such findings are confirmed through UV-visible diffused reflectance, photoelectrochemical and photoluminescence analyses. Nanosheets made of rGO modified {0 0 1} black TiO2 could be used as an effective photocatalyst for the removal of ethylene from large volume fruit storage areas by exploiting a simple light source in the presence of high content of humidity.
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Raj, B. G. S., Mangalaraja, R. V., Vinoth, V., Pugazhenthiran, N., Herrera, F. V., Jauhar, R. M., et al. (2023). Facile sonochemical synthesis of nanostructured FeWO4-rGO and CuCo2O4 nanocomposite for high-rate capability and stable asymmetric (CuCo2O4//FeWO4-rGO) supercapacitors. J. Alloys Compd., 968, 172156.
Abstract: The present work reports iron tungstate (FeWO4) nanostructures with reduced graphene oxide (rGO) as a novel anode material for enhancing the electrochemical properties of asymmetric supercapacitors. The FeWO4-rGO composite nanostructures were successfully synthesized by the one-pot sonochemical method. The synthesized nanocomposites crystal structure and phase purity were investigated using the powder X-ray diffraction (XRD) technique. The Fourier transform infrared (FT-IR) spectrograms demonstrate the presence of functional groups in the composite. The composite's morphology was examined using the high-resolution transmission electron microscopy (HR-TEM) and the field emission scanning electron microscopy (FE-SEM), and it was observed that the FeWO4 nanostructures were uniformly distributed on the reduced graphene oxide surface. The cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) analyses were used to evaluate the electrochemical performance. After 5000 cycles at 10 mA cm(-2), the FeWO4-rGO composite achieved a better rate of efficiency and outstanding cycling performance, with capacitance retained at 68% and 77.8%, respectively. In 1 M Na2SO4, an asymmetric device (CuCo2O4//FeWO4-rGO composite) achieved a high energy density of 21.5 W.h Kg(-1) and a power density of 147 W Kg(-1). In the FeWO4-rGO nanocomposite, the reduced graphene oxide could enhance the conductivity and the free diffusion processes for the quick ion transport and easy ion access to the storage sites. The obtained results indicated that the FeWO4-rGO nanocomposite could be a good anode electrode material for the next-generation energy storage applications.
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Shanmugaraj, K., Vinoth, V., Pugazhenthiran, N., Valdes, H., Salvo, C., Sepulveda, E., et al. (2023). Ferrihydrite- Graphene oxide foams as an efficient adsorbent for Arsenic (III) removal from an aqueous solution. Inorg. Chem. Commun., 153, 110892.
Abstract: We report the synthesis of a new range of ferrihydrite-graphene oxide (FH-GO) foams using chitosan as cross linker, with varying iron content (5 wt%, 10 wt%, and 20 wt% of FH) as highly efficient adsorbents for the removal of arsenic (III) (As(III)) in an aqueous solution. The sonochemical methods were adopted to synthesize various FH-GO foams and were further characterized by XRD, SEM, TEM, FTIR, Raman, and XPS techniques. The synthesized materials were used for the removal of As(III) in both batch and fixed bed absorbent column methods. The adsorption isotherm results showed that the 10 wt% of FH-GO foams demonstrated a superior adsorbent for the As(III) with high adsorption capacities than that of the other two FH-GO foams (5 wt% and 20 wt% of FH). Moreover, 10 wt% of FH-GO foams was also demonstrated to be nearly a complete (>98.4%) removal of As(III) ions at neutral pH 7. The adsorption isotherm fitted very well with the Langmuir model with the highest accuracy data for all the synthesized adsorbent materials. In addition, the fixed bed absorbent column method was also adopted for the removal of As(III) ions in the water sample, which showed > 99.2% of removal efficiency. The outstanding adsorption capabilities, along with their easy and low-cost synthesis, make these kinds of adsorbents extremely capable for commercial applications in wastewater treatment and drinking water purification.
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Vinoth, V., Kaimal, R., Selvamani, M., Michael, R., Pugazhenthiran, N., Mangalaraja, R. V., et al. (2023). Synergistic impact of nanoarchitectured GQDs-AgNCs(APTS) modified glassy carbon electrode in the electrochemical detection of guanine and adenine. J. Electroanal. Chem., 934, 117302.
Abstract: In this work, a facile green approach for the synthesis of graphene quantum dots (GQDs) embedded on silicate network silver nanocrystals (GQDs-AgNCs(APTS)) is reported. Moreover, glassy carbon-GC electrodes were mod-ified with the prepared nanocomposite containing graphene quantum dots supported on silver nanocrystals (GQDs-AgNCs(APTS)) and applied for simultaneous detection of guanine (GA) and adenine (AD). The chemically modified electrode was assessed during the determination of purine bases by cyclic voltammetry-CV and dif-ferential pulse voltammetry-DPV. The incorporation of GQDs-AgNCs(APTS) nanocomposites over the surface of the GC electrode considerably enhances the anodic peak currents and decreases the adenine and guanine peak potentials. Compared to other electrodes, GQDs-AgNCs(APTS)/GC improved the electrochemical behavior towards the detection of adenine and guanine. At optimal conditions, calibration curves were obtained by DPV being linear in the range of 0.1-6.0 mu M and 0.1-5.0 mu M for guanine and adenine, respectively. The detec-tion limits of both guanine and adenine were estimated as 0.1 mu M. Additionally, interferences analyses were performed on the existence of other interferent compounds. Furthermore, the method developed for the iden-tification of GA and AD was proved using fish sperm DNA samples.
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