Pina, S., Candia-Onfray, C., Hassan, N., Jara-Ulloa, P., Contreras, D., & Salazar, R. (2021). Glassy Carbon Electrode Modified with C/Au Nanostructured Materials for Simultaneous Determination of Hydroquinone and Catechol in Water Matrices. Chemosensors, 9(5), 88.
Abstract: The simultaneous determination of hydroquinone and catechol was conducted in aqueous and real samples by means of differential pulse voltammetry (DPV) using a glassy carbon electrode modified with Gold Nanoparticles (AuNP) and functionalized multiwalled carbon nanotubes by drop coating. A good response was obtained in the simultaneous determination of both isomers through standard addition to samples prepared with analytical grade water and multivariate calibration by partial least squares (PLS) in winery wastewater fortified with HQ and CT from 4.0 to 150.00 mu M. A sensitivity of 0.154 mu A mu M-1 and 0.107 mu A mu M-1, and detection limits of 4.3 and 3.9 mu M were found for hydroquinone and catechol, respectively. We verified the reliability of the developed method by simultaneously screening analytes in spiked tap water and industrial wastewater, achieving recoveries over 80%. In addition, this paper demonstrates the applicability of chemometric tools for the simultaneous quantification of both isomers in real matrices, obtaining prediction errors of lower than 10% in fortified wastewater.
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Pina, S., Sandoval, A. M., Jara-Ulloa, P., Contreras, D., Hassan, N., Coreno, O., et al. (2022). Nanostructured electrochemical sensor applied to the electrocoagulation of arsenite in WWTP effluent. Chemosphere, 306, 135530.
Abstract: A sensitive electroanalytical method for the determination of arsenite, based on a heterostructure of aminated multiwalled carbon nanotubes and gold nanoparticles, was applied in an electrocoagulation (EC) treatment for the elimination of arsenite. A sensitive quantitative response was obtained in the determination of As3+ in a secondary effluent from a wastewater treatment plant from Santiago (Chile). The preconcentration stage was optimized through a Central Composite Face design, and the most sensitive peak current was obtained at 200 s and -600 mV of time and accumulation potential, respectively, after a differential pulse voltammetry sweep. Electroanalytical determination was possible in an interval between 42.89 and 170.00 mu g L-1 with a detection limit of 0.39 mu g L-1, obtaining recoveries over 99.1%. The developed method was successfully applied in an electrocoagulation treatment to remove 250 mu g L-1 of arsenite from a polluted effluent in a batch system. Complete arsenite removal was achieved using a steel EC system with a current density of 6.0 mA cm(-2) in less than 3 min of 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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Sahlevani, S. F., Pandiyarajan, T., Arulraj, A., Valdes, H., Sanhueza, F., Contreras, D., et al. (2024). Tailored engineering of rod-shaped core@shell ZnO@CeO2 nanostructures as an optical stimuli-responsive in sunscreen cream. Mater. Today Commun., 38, 107959.
Abstract: The catalytic efficiency of the materials can be boosted with the selective designing (nanostructures) including the core@shell which aids in attaining the separation of photoinduced charge carriers. However, to effectively separate the carriers and reduce the rate of recombination, tuning the thickness of the shell wall is a vital one. The one-dimensional (1D) rod-like shell wall-controlled ZnO@CeO2 core@shell structures were successfully prepared via co-precipitation and hydrothermal methods using the hexamethylenetetramine (HMTA) as a reagent. The CeO2 shell wall thickness was fine-tuned between 15 and 70 nm with a variation in the concentration of HMTA reagent. The results revealed that the concentration of HMTA played a significant role in the formation of ZnO@CeO2 core@shell structures and in tuning their thickness. The FE-SEM images evidenced the core-shell structures formation with the specific thickness and uniformity. The HR-TEM images confirmed the homogeneity and regular form of the shell thickness. The unit cell and crystallite size were identified from the XRD analysis. The constructed core-shell structures were further employed in the formula of the prototypes of sunscreen and their photoprotective performance was analyzed in the view to cut the solar light irradiation in a new sunscreen formulation. The developed core-shell ZnO@CeO2 structures showed the excellent optical absorption in both the UV as well as visible regions.
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