Assessment of photocatalytic potentiality and determination of ecotoxicity (using plant model for better environmental applicability) of synthesized copper, copper oxide and copper-doped zinc oxide nanoparticles.
ABSTRACT: A facile cost effective wet chemical method of synthesis is proposed for Cu-NPs, CuO-NPs and Cu-doped ZnO-NPs. The nanomaterials are opto-physically characterized for nano standard quality. Cu-doped ZnO-NPs based catalytic system is found to possess most efficient photocatalytic activity in degradation of two organic azo-dyes namely methyl red (MR) and malachite green (MG) that are released as industrial effluents in eco-environment intercollegium. Two possible photocatalytic degradation pathways are proposed to understand the mechanism of interaction prevailing during the mineralization of MR and MG dyes. Such study provides insight for waste water management. The uniqueness of the present work is 1) possible routes of MG dye degradation by Cu-doped ZnO-NPs and subsequent intermediate by-products are novel and pioneered of its kind. 2) two new intermediate byproducts are identified suggesting prevalence of multiple MR degradation pathways by Cu-doped ZnO-NPs.For assessment of residual NPs impact on environment, eco-toxicological assay is performed using plant system (Sesamum indicum L.) as model. The study encompasses seed germination, seedling morphology, quantification of endogenous H2O2 and MDA generation, estimation of DNA double strand break and analysis of cell cycle inhibition. Results highlight reduced ecotoxicity of Cu-doped ZnO-NPs compared to the other synthesized nanomaterials thereby suggesting better environmental applicability in waste water purification.
Project description:Removal of nitrogen oxide pollution has attracted much attention, and photocatalysis is considered as an effective method to treat polluted gas. Currently, modified semiconductors with approximate band gap are used as visible-light-driven photocatalysts. Herein, this is the first investigation of photocatalytic removal of NO under visible light over Cr-doped ZnO nanoparticles (Cr-ZnO NPs). Furthermore, the trapping species experiment and electron spin resonance measurement were conducted to identify the primary reactive factor of the photocatalytic reaction. In this study, Cr-ZnO NPs were synthesized by the sol-gel method with a narrow band gap, enhanced NO photocatalytic degradation performance, low NO2 conversion yield, and high stability under visible light.
Project description:Photocatalytic removal of ammonium-nitrogen ( NH4+ -N) from water using solar energy is an approach of high interest and applicability due to the convenience in application. ZnO has a great potential in photocatalytic decomposition of NH4+ -N and conversion of this nutrient to under visible light irradiations. However the applicability of pristine ZnO though is limited due to its reduced capacity to utilize light from natural light. Herein, we report a two-step ZnO-modified strategy (Cu-doped ZnO nanoparticles, immobilized on reduced graphene oxide (rGO) sheets) for the promotion of photocatalytic degradation of NH4+ -N under visible light. UV-Vis spectra showed that the Cu/ZnO/rGO can be highly efficient in the utilization of photons from the visible region. Hence, Cu/ZnO/rGO managed to demonstrate adequate photocatalytic activity and effective NH4+ -N removal from water under visible light compared to single ZnO. Specifically, up to 83.1% of NH4+ -N (initial concentration 50 mg·L-1, catalyst dosage 2 g·L-1, pH 10) was removed within 2 h retention time under Xe lamp irradiation. From the catalysis, the major by-product was N2. The high ammonia degradation efficiency from the ZnO/Cu/rGO is attributed to the improvement of the reactive oxygen species (ROSs) production efficiency and the further activation of the interfacial catalytic sites. This study also demonstrated that such nanocomposite is a recyclable agent. Its NH4+ -N removal capacity remained effective even after five batch cycles. In addition, Cu/ZnO/rGO was applied to treat real domestic wastewater, and it was found that chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal efficiencies can reach 84.3, 80.7, and 90.3%, respectively. Thus, Cu/ZnO/rGO in the presence of solar light can be a promising photocatalyst in the field of wastewater treatment.
Project description:Undoped and Fe-doped ZnO nanoparticles (NPs) were synthesized using Amaranthus spinosus leaf extract as a reducing agent. The physicochemical traits, dissolution, cytotoxicity, as well as the antioxidant, photocatalytic and antibacterial activities of synthesized NPs were investigated. The results revealed that ZnO NPs were rod shaped with hexagonal phase structure, and their crystal size, dissolubility and aggregation decreased with Fe doping of NPs. Cytotoxicity of the NPs was studied against MCF-7 cells by MTT assay. IC50 values for undoped and 1 wt% Fe-doped ZnO NPs were found to be 400 and 600 ?g mL-1, respectively. Cell viability with Fe-doped ZnO NPs was higher than with undoped ZnO. Among the synthesized NPs, A. spinosus-mediated 1 wt% Fe-doped ZnO shows a better decolourization efficiency of 97% for indigo carmine dye under solar irradiance. The antibacterial activity of NPs was tested against Gram-negative Escherichia coli and Gram-positive Bacillus safensis using disc diffusion, minimum inhibitory concentration and growth curve method. The bactericidal activity of Fe-doped ZnO NPs was more prominent with E. coli than B. safensis bacteria and when compared to undoped ZnO.
Project description:A novel eco-friendly procedure was developed to produce safer, stable and highly pure zinc oxide nanoparticles (ZnO NPs) using microalgae Chlorella extract. The ZnO NPs were synthesized simply using zinc nitrate and microalgae Chlorella extract which conducted at ambient conditions. In this recipe, microalgae Chlorella extract acted as the reducing agent and a stabilizing layer on fresh ZnO NPs. UV-visible spectrum was confirmed the formation of ZnO NPs showing an absorption peak at 362?nm. XRD results demonstrated that prepared ZnO NPs has a high-crystalline hexagonal (Wurtzite) structure, with average size about 19.44?nm in diameter. FT-IR spectral analysis indicated an active contribution of algae-derived biomolecules in zinc ions bioreduction. According to SEM and TEM observations, ZnO NPs are well dispersed and has a hexagonal shape with the average size of 20?±?2.2?nm, respectively. Based on gas chromatography analyses, the optimum 0.01?g/L dosage of ZnO catalyst revealed an effective photocatalytic activity toward the degradation (97%) of Dibenzothiophene (DBT) contaminant as an organosulfur model in the neutral pH at the mild condition. Rapid separation and facile recyclability at five consecutive runs were demonstrated high efficiency and durability of green ZnO nanophotocatalyst. The possible mechanisms of green ZnO NPs formation and the photo-desulfurization of DBT were also proposed.
Project description:Our study was focused on the synthesis of photocatalytic materials for the degradation of organic dyes based on the valorization of biomass resources. The biochar resulted from pyrolysis process of cherry pits wastes was activated by CO<sub>2</sub> flow. Activated and inactivated carbon was used to obtain carbon-based photocatalysts impregnated with different zinc salt precursors. The activation of carbon had no significant influence on the photodegradation process. The doping procedure used Li<sub>2</sub>CO<sub>3</sub> and Zn(CH<sub>3</sub>COO)<sub>2</sub> of different concentrations to impregnate the biochar. The carbon-ZnO-Li<sub>2</sub>O based nanomaterials were analysed by TEM and SEM, while the presence of hexagonal wurtzite ZnO was investigated by XRD. The solid samples were analysed by PL at 360?nm excitation fixed wavelength to correlate their morphology with the optical and photocatalytic properties. The presence of Li atoms led to photocatalytic activities of the doped ZnO similar to the undoped ZnO obtained at higher concentrations of zinc acetate precursor.
Project description:In this paper, the Ag-doped zinc oxide nanorods embedded reduced graphene oxide (ZnO:Ag/rGO) nanocomposite was synthesized for photocatalytic degradation of methyl orange (MO) in the water. The microstructural results confirmed the successful decoration of Ag-doped ZnO nanorods on rGO matrix. The photocatalytic properties, including photocatalytic degradation, charge transfer kinetics and photocurrent generation, are systematically investigated using electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD). The results of photocatalytic dye degradation measurements indicated that ZnO:Ag/rGO nanocomposite is more effective than pristine ZnO to degrade the MO dye, and the degradation rate reached 40.6% in 30 min. The decomposition of MO with ZnO:Ag/rGO nanostructure followed first-order reaction kinetics with a reaction rate constant (K a) of 0.01746 min-1. The EIS, PCTR and OCVD measurements revealed that the Ag doping and incorporation of rGO could suppress the recombination probability in ZnO by the separation of photo-generated electron-hole pairs, which leads to the enhanced photocurrent generation and photocatalytic activity. The photocurrent density of ZnO:Ag/rGO, ZnO/rGO and pristine ZnO are 206, 121.4 and 88.8 nA cm-2, respectively.
Project description:Heterogeneous photo-Fenton systems offer efficient solutions for the treatment of wastewaters in the textile industry. This study investigated the fabrication and structural characterization of novel peculiar-shaped Cu<sup>II</sup>O, Fe<sup>III</sup><sub>2</sub>O<sub>3</sub>, and Fe<sup>II</sup>O nanoparticles (NPs) compared to the properties of the iron(II)-doped copper ferrite Cu<sup>II</sup><sub>0.4</sub>Fe<sup>II</sup><sub>0.6</sub>Fe<sup>III</sup><sub>2</sub>O<sub>4</sub>. The photocatalytic efficiencies of these NPs and the composite of the simple oxides (Cu<sup>II</sup>O/Fe<sup>II</sup>O/Fe<sup>III</sup><sub>2</sub>O<sub>3</sub>) regarding the degradation of methylene blue (MB) and rhodamine B (RhB) as model dyes were also determined. The catalysts were synthesized via simple co-precipitation and calcination technique. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) were utilized for structural characterization. The structure of Cu<sup>II</sup>O was bead-like connected into threads, Fe<sup>III</sup><sub>2</sub>O<sub>3</sub> was rod-like, while Fe<sup>II</sup>O pallet-like, with average crystallite sizes of 18.9, 36.9, and 37.1 nm, respectively. The highest degradation efficiency was achieved by Cu<sup>II</sup>O for RhB and by Cu<sup>II</sup><sub>0.4</sub>Fe<sup>II</sup><sub>0.6</sub>Fe<sup>III</sup><sub>2</sub>O<sub>4</sub> for MB. The Cu<sup>II</sup>O/Fe<sup>II</sup>O/Fe<sup>III</sup><sub>2</sub>O<sub>3</sub> composite proved to be the second-best catalyst in both cases, with excellent reusability. Hence, these NPs can be successfully applied as heterogeneous photo-Fenton catalysts for the removal of hazardous pollutants. Moreover, the simple metal oxides and the iron(II)-doped copper ferrite displayed a sufficient antibacterial activity against Gram-negative <i>Vibrio fischeri</i>.
Project description:Spread of antibiotic resistant bacteria through water, is a threat to global public health. Here, we report Fe-doped ZnO nanoparticles (Fe/ZnO NPs) based solar-photocatalytic disinfection (PCD) of multidrug resistant Escherichia coli (MDR E. coli). Fe/ZnO NPs were synthesized by chemical precipitation technique, and when used as photocatalyst for disinfection, proved to be more effective (time for complete disinfection?=?90?min) than ZnO (150?min) and TiO2 (180?min). Lipid peroxidation and potassium (K+) ion leakage studies indicated compromisation of bacterial cell membrane and electron microscopy and live-dead staining confirmed the detrimental effects on membrane integrity. Investigations indicated that H2O2 was the key species involved in solar-PCD of MDR E. coli by Fe/ZnO NPs. X-ray diffraction and atomic absorption spectroscopy studies showed that the Fe/ZnO NPs system remained stable during the photocatalytic process. The Fe/ZnO NPs based solar-PCD process proved successful in the disinfection of MDR E. coli in real water samples collected from river, pond and municipal tap. The Fe/ZnO NPs catalyst made from low cost materials and with high efficacy under solar light may have potential for real world applications, to help reduce the spread of resistant bacteria.
Project description:A new structure of honeycomb-like ZnO mesoporous nanowall arrays (MNWAs) with highly efficient photocatalytic activity was designed and successfully synthesized on Al foil by hydrothermal method. The nanowalls of ZnO-MNWAs have mesopores, which possess a large surface area. The visible light absorption of ZnO-MNWAs was efficiently stronger than ZnO nanowire, resulting in that the photocatalytic activity of ZnO-MNWAs, whose bandgap energy was 3.12?eV, was 5.97 times than that of ZnO nanowires in the degradation of methyl orange. Besides, Al foil acted as a good electron conductor which was beneficial to the separation of photo-induced electron-hole pairs. After modifying ZnO-MNWAs with a proper amount of Ag nanoparticles (NPs), photocatalytic activity could be further enhanced. The photocatalytic activity of ZnO-MNWAs with the optimal amount of Ag NPs was 9.08 times than that of ZnO nanowires and 1.52 times than that of pure ZnO-MNWAs.
Project description:Herein we explore the role of localized plasmonic heat generated by resonantly excited gold (Au) NPs on visible light driven photocatalysis process. Au NPs are deposited on the surface of vertically aligned zinc oxide nanorods (ZnO NRs). The localized heat generated by Au NPs under 532?nm continuous laser excitation (SPR excitation) was experimentally probed using Raman spectroscopy by following the phonon modes of ZnO. Under the resonant excitation the temperature at the surface of the Au-ZnO NRs reaches up to about 300?°C, resulting in almost 6 times higher apparent quantum yield (AQY) for photocatalytic degradation of methylene blue (MB) compared to the bare ZnO NRs. Under solar light irradiation the Au-ZnO NRs demonstrated visible light photocatalytic activity twice that of what was achieved with bare ZnO NRs, while significantly reduced the activation energy required for the photocatalytic reactions allowing the reactions to occur at a faster rate.