Titanium dioxide (TiO2) nanoparticles have been extensively studied for catalyzing the photo-degradation of organic pollutants, the photocatalyst being nonselective to the substrate. We, however, ...found that TiO2 nanoparticles prepared via the sol-gel and hydrothermal synthetic routes each possess a definite specificity to the charge of the substrate for photodegradation. The nanoparticles were characterized by SEM, FTIR, XRD, TGA, and UV-visible spectra, and the photocatalytic degradation under UV-B (285 nm) irradiation of two model compounds, anionic methyl Orange (MO) and cationic methylene blue (MB) was monitored by a UV-visible spectrophotometer. Untreated sol-gel TiO2 nanoparticles (Tsg) preferentially degraded MO over MB (90% versus 40% in two hours), while after calcination at 400 °C for two hours (Tsgc) they showed reversed specificity (50% MO versus 90% MB in one hour). The as-prepared hydrothermal TiO2 nanoparticles (Tht) behaved in the opposite sense of Tsg (41% MO versus 91% MB degraded in one and a half hours); calcination at 400 °C (Thtc) did not reverse the trend but enhanced the efficiency of degradation. The study indicates that TiO2 nanoparticles can be made to degrade a specific class of organic pollutants from an effluent facilitating the recycling of a specific class of pollutants for cost-effective effluent management.
Abalone are frequently exposed to several environmental factors including heavy metal toxicity, thermal stress, H2O2-stress, starvation, viral and bacterial infection that can induce oxidative ...stress. Glutathione reductase is a vital enzyme in the antioxidant defense system that catalyzes the reduction of oxidized glutathione to reduced glutathione. The present study aimed to identify and localize glutathione reductase in Pacific abalone (Hdh-GR) and assess its potential role in stress physiology, heavy metal toxicity, immune response, gonadal development, and metamorphosis. The mRNA expression of Hdh-GR was upregulated in response to thermal stress, starvation, H2O2-stress, and cadmium-exposed toxicity. The induced mRNA expression was also quantified in immune-challenged abalone. Moreover, the Hdh-GR expression was significantly higher during metamorphosis. The Hdh-GR mRNA expression showed an inverse relationship with ROS production in heat stressed Pacific abalone. These results suggest that Hdh-GR has central role in the stress physiology, immune response, gonadal development, and metamorphosis of Pacific abalone.
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•Hdh-GR, a biomarker gene was characterized from Pacific abalone.•Fluorescence in-situ hybridization confirmed the localization of Hdh-GR in DG.•Heavy metal (Cd) toxicity, ROS-induction (H2O2), and thermal stress induces Hdh-GR expression.•Virus infection, bacterial infection, and starvation also induces Hdh-GR expression.•Hdh-GR may have defensive role against excessive ROS production.
Two different stable forms of copper oxide (Cu2O and CuO) nanoparticles (NPs) were selectively synthesized through a smart approach using the same precursor but different reagent amounts. The ...fabrication strategy is cost-effective and relatively easy. The bandgap energies of the as-synthesized Cu2O- and CuO-NPs, as determined from Tauc plots, are 2.08 and 1.82 eV, respectively. The photocatalytic performance of these NPs was assessed through their use in the photodegradation of an organic-dye water contaminant under UV and solar-light illumination. Methylene blue (MB) was chosen as a representative dye because of its ubiquitous presence in industrial wastewater and its hazardous effects on human health. The results of experiments involving the photodegradation of MB by the synthesized Cu2O- and CuO-NPs revealed 97% and 81% photodecomposition efficiencies, respectively, during 60 min of UV-light illumination. When sunlight was used as a light source, and the duration was extended to 120 min, the photodecomposition efficiencies were 70% and 63% for the Cu2O- and CuO-NP photocatalysts, respectively. The efficient degradation of MB solution by the as-prepared NPs implies that they are potentially potent photocatalysts for the treatment of wastewater originating from industrial and domestic sources.
This paper proposes a composite nonlinear controller combining backstepping and double-integral sliding mode controllers for DC–DC boost converter (DDBC) feeding by constant power loads (CPLs) to ...improve the DC-bus voltage stability under large disturbances in DC distribution systems. In this regard, an exact feedback linearization approach is first used to transform the nonlinear dynamical model into a simplified linear system with canonical form so that it becomes suitable for designing the proposed controller. Another important feature of applying the exact feedback linearization approach in this work is to utilize its capability to cancel nonlinearities appearing due to the incremental negative-impedance of CPLs and the non-minimum phase problem related to the DDBC. Second, the proposed backstepping double integral-sliding mode controller (BDI-SMC) is employed on the feedback linearized system to determine the control law. Afterwards, the Lyapunov stability theory is used to analyze the closed-loop stability of the overall system. Finally, a simulation study is conducted under various operating conditions of the system to validate the theoretical analysis of the proposed controller. The simulation results are also compared with existing sliding mode controller (ESMC) and proportional-integral (PI) control schemes to demonstrate the superiority of the proposed BDI-SMC.
Abstract
A convenient route was developed for the selective preparation of two stable nanocomposites, Ti
3+
/TiO
2
/CNT (labeled as TTOC-1 and TTOC-3) and Ti
3+
/TiO
2
/carbon layer (labeled as ...TTOC-2), from the same precursor by varying the amount of single-walled carbon nanotubes used in the synthesis. TiO
2
is an effective photocatalyst; however, its wide bandgap limits its usefulness to the UV region. As a solution to this problem, our prepared nanocomposites exhibit a small bandgap and wide visible-light (VL) absorption because of the introduction of carbonaceous species and Ti
3+
vacancies. The photocatalytic efficiency of the nanocomposites was examined via the degradation of methylene blue dye under VL. Excellent photocatalytic activity of 83%, 98%, and 93% was observed for TTOC-1, TTOC-2, and TTOC-3 nanocomposites within 25 min. In addition, the photocatalytic degradation efficiency of TTOC-2 toward methyl orange, phenol, rhodamine B, and congo red was 28%, 69%, 71%, and 91%, respectively, under similar experimental conditions after 25 min. Higher reusability and structural integrity of the as-synthesized photocatalyst were confirmed within five consecutive runs by photocatalytic test and X-ray diffraction analysis, respectively. The resulting nanocomposites provide new insights into the development of VL-active and stable photocatalysts with high efficiencies.
We report enhanced catalytic action of a series of copper(II)-oxide-single-walled carbon nanotube (CuO-SWCNT) composite photocatalysts (abbreviated as CuO-SWCNT-0.5, CuO-SWCNT-2, and CuO-SWCNT-5, ...where 0.5, 2, and 5 represent the calcination time in hours) synthesized via recrystallization followed by calcination. The photocatalytic performance of the fabricated nanocomposites was examined by evaluating the degradation of methylene blue (MB) under irradiation with visible light. All of the as-fabricated nanocomposites were effective photocatalysts for the photodegradation of a MB solution; however, the CuO-SWCNT-5 displayed the best photocatalytic ability among the investigated catalysts, achieving 97.33% degradation of MB in 2 h under visible-light irradiation. The photocatalytic action of the nanocomposites was remarkably higher than that of pristine CuO nanocrystals fabricated using the same route. The recyclability of the photocatalyst was also investigated; the CuO-SWCNT-5 catalyst could be reused for three cycles without substantial degradation of its catalytic performance or morphology.
ZnO nanoparticles (ZnO-NPs) were synthesized by a straightforward modified thermal method using only one chemical: zinc acetate dihydrate. The process is environmentally safer than other methods ...because it does not involve other chemicals or a catalyst, acid, or base source. X-ray diffraction analysis indicated that the ZnO-NPs crystallize in the hexagonal wurtzite structure. The UV–vis absorption spectra revealed a marked redshift, which is critical for enhanced photocatalytic activity. We used methylene blue for photocatalytic activity tests and found an excellent degradation percentage (99.7%) within a short time (80 min). The antibacterial activity of the synthesized ZnO-NPs was tested against Escherichia coli at different concentrations of ZnO-NPs. The analysis revealed that the minimum inhibitory concentration (MIC) of the ZnO-NPs against E. coli was 30–50 μg/mL. Our ZnO-NPs were found to be more effective than previously reported ZnO-NPs synthesized via other methods.
An efficient photocatalyst, ZnO–single-walled carbon nanotube (ZnO–SWCNT) nanocomposite was successfully fabricated through a straightforward one-pot–two-chemical recrystallization technique followed ...by thermal decomposition. The photocatalytic efficiency of the prepared ZnO–SWCNT composite was investigated by assessing the degradation of a persistent water-pollutant dye (methylene blue, MB) under visible-light irradiation. We found that the synthesized photocatalyst is an effective and recyclable agent for the decomposition of an MB solution. Its photocatalytic performance was substantially better than that of pristine ZnO nanorods or pristine SWCNTs. The reusability of the photocatalyst was also examined, affirming that it could be used repeatedly for five cycles without conspicuous loss of morphology or catalytic performance.
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•The synergistic effect of SWCNTs on the photocatalytic activity of spherical ZnO nanoparticles (ZNPs) is presented.•A series of nanocomposites composed of ZNPs and SWCNTs are ...synthesized.•Optical bandgap of the pure ZNPs is narrowed and their maximum UV absorbance is red-shifted upon composite formation.•Maximum rate constant is 680 % and 2570 % greater than those of the pure ZNPs and the SWCNTs, respectively.•The synergistic effect is due to the creation of a heterojunction between the SWCNTs and the ZNPs.•The nanocomposite demonstrates remarkable reusability: the photocatalytic efficiency is reduced by only 3.62 % after the fifth cycle.
A series of nanocomposites composed of spherical ZnO nanoparticles (ZNPs, average diameter of 119 nm) and single-walled carbon nanotubes (average diameter of 1.1 nm) (ZNP–SWCNT) were synthesized. The synergistic effect of the SWCNTs on the photocatalytic efficiency of the ZNPs for the degradation of methylene blue dye under UV-light was demonstrated. The as-synthesized nanocomposites, pure ZNPs, and the pristine SWCNTs exhibited pseudo-first-order kinetic behavior in the decomposition of the dye. The decomposition rate constant in the presence of the nanocomposite varied with the amount of SWCNTs. The maximum rate constant was 680 % and 2570 % greater than those of the pure ZNPs and the pristine SWCNTs, respectively. It was found that the optical bandgap of the pure ZNPs was considerably narrowed, and their maximum UV absorbance was red-shifted upon composite formation between the SWCNTs and ZNPs. Those results suggested that the SWCNTs played a crucial role in the improvement of the catalytic activity of the ZNPs. Such a synergistic effect was due to the creation of a chemical heterojunction between the SWCNTs and the ZNPs. Moreover, the prepared nanocomposite demonstrated remarkable reusability: the photocatalytic efficiency was reduced by only 3.62 % after the fifth cycle.
In this recent era, several approaches have been developed to alleviate the adverse effects of salinity stress in different plants. However, some of them are not eco-friendly. In this context, ...evolving sustainable approaches which enhance the productivity of saline soil without harming the environment are necessary. Many recent studies showed that plant growth-promoting rhizobacteria (PGPR) are known to confer salinity tolerance to plants. Salt-stressed plants inoculated with PGPR enhance the growth and productivity of crops by reducing oxidative damage, maintaining ionic homeostasis, enhancing antioxidant machinery, and regulating gene expressions. The PGPR also regulates the photosynthetic attributes such as net photosynthetic rate, chlorophyll, and carotenoid contents and enhances the salinity tolerance to plants. Moreover, PGPR has a great role in the enhancement of phytohormones and secondary metabolites synthesis in plants under salt stress. This review summarizes the current reports of the application of PGPR in plants under salt stress and discusses the PGPR-mediated mechanisms in plants of salt tolerance. This review also discusses the potential role of PGPR in cross-talk with phytohormones and secondary metabolites to alleviate salt stress and highlights the research gaps where further research is needed.
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