Photocatalytic Efficiency Of ZnO Research Articles

Analysis of the photocatalytic efficiency of ZnO–ZnO nanorods films deposited by two-step chemical methods in hydrogen generation

Analysis of the photocatalytic efficiency of ZnO–ZnO nanorods films deposited by two-step chemical methods in hydrogen generation

Preparation of Yb-doped ZnO nanoparticles by combustion method combined with high temperature calcination for photodegradation of methylene blue under visible light irradiation

ABSTRACT Yb-doped ZnO nanoparticles with different contents of Yb were prepared by a tartaric acid-assisted combustion method combined with high temperature calcination. TGA/DTA, XRD, TEM, XPS, Raman spectrophotometry, UV-visible spectroscopy and photoluminescence spectroscopy were used to determine calcination temperature, phase, morphology, vibrational mode, optical properties and atomic composition. In this research, Yb3+ ions substituted for Zn2+ ions containing in hexagonal ZnO structure. The samples were composed of nanoparticles with good particle-size distribution. Their photocatalytic activities were investigated through the degradation of methylene blue under visible radiation. The results demonstrated that Yb dopant can play the role in improving the photocatalytic efficiency of ZnO and that Zn0.97Yb0.03O nanoparticles exhibited the highest photocatalytic activity of 96.78% within 100 min with ●O2– and ●OH as the main active radicals.

Spinach Extract Derived Carbon Dots Decorated on ZnO Nanorods for Photocatalytic Dye Degradation

The carcinogenic and mutagenic nature of organic dyes makes their removal from dye-containing wastewaters essential prior to the discharge of such wastewaters. We synthesized carbon dots having emission wavelengths in the near-infrared region from spinach extract. Thereafter, CDs were embedded on ZnO nanorods through hydrothermal treatment. The prepared ZnO doped with CDs were characterized by various analytical instruments and used to photocatalytically degrade methylene blue dye under sunlight. The as-prepared ZnO exhibited nanorod morphology, with the CDs doped on its surface. The dye degradation followed pseudo-first-order kinetics; the ZnO doped with CDs synthesized at pH 10 achieved the highest dye degradation, with a kinetic coefficient of 0.02889 min−1. This study shows that the photocatalytic efficiency of ZnO can be effectively improved by doping with CDs.

Exhibition of Novel Photocatalytic Activity and Photoluminescence Properties with High Inhibition Towards Bacterial Growth by Hydrothermally Grown ZnO Nanorods

Background: Metal oxide nanomaterial such as ZnO shows novel structural, optical, electrical and antibacterial properties due to its wide bandgap (3.37 eV) and high excitonic binding energy (60 meV). Probing these inherent properties of nanosized ZnO with different morphologies has generated new interest among researchers. Objective: To investigate the size-dependent functional attributes, ZnO nanorods were prepared by hydrothermal method and the photocatalytic (PC) efficiency was studied. The photoluminescence (PL) property of ZnO nanorods was also studied by recording the emission spectrum under photoexcitation. These nanorods (NRs) were coated on cotton fabric to study the effectiveness of these NRs in defending and inhibiting the growth of different bacteria. Methods: The crystallographic structure and morphology of the ZnO samples were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopic (FESEM) measurements. PL measurement at room temperature was undertaken by exciting the sample with light of wavelength 350 nm. The PC property of ZnO NRs was studied in degrading organic dyes like methylene blue. Bacteria like Staphylococcus aureus, Escherichia coli and Bacillus subtilis were cultured and the inhibition of growth of these bacteria was studied by the application of ZnO. To enhance the microbe defence mechanism of fabric, we coated these NRs on fabric test samples and investigated the bacterial growth on it. Results: XRD and FESEM studies reveal the dimension of the synthesized products in the nano range. These nanorods are of high density and have surface roughness as per the FESEM study. PL measurement shows the presence of strong UV emission at 382 nm with defect emissions in the bluegreen region opening up the path for ZnO to be used in the fabrication of optoelectronic devices. PC study reveals that 89% degradation of methylene blue (MB) dye is achievable in 180 min using these ZnO catalysts. The anti-bacterial study shows that the minimum inhibitory concentration (MIC) of ZnO nanorods coated on the fabric against S. aureus is found to be 3.5 mg/ml which is the minimum as compared to E. coli (7.5 mg/ml) and B. subtilis (5.5 mg/ml). The study further enunciates that fabric coated with ZnO samples exhibited considerably high inhibition activity towards S. aureus. Conclusion: The study shows that ZnO NRs can be effectively used for the fabrication of UVLASER/ LED. The photocatalytic efficiency of ZnO will be useful for the degradation of organic dyes controlling environmental pollution. It further enunciates that fabric coated with ZnO samples exhibited considerably high inhibition activity toward S. aureus (skin bacteria) which will be helpful in defending microbes if used in surgical cotton bandages.

Effect of vegetable waste extract on microstructure, morphology, and photocatalytic efficiency of ZnO–CuO nanocomposites

Environment friendly and cost-effective structure-directing agents (SDAs) are highly desirable for the development of purposely designed functional nanomaterials. To comply, we aimed to explore vegetable waste extracts as potential SDAs for the synthesis of ZnO–CuO nanocomposites. Extracts of wastes of three different vegetables (cauliflowers, potatoes, and peas) were used, and their impact upon crystal structure, morphology, optical-band-gap (Eg ), and photocatalytic efficiency of ZnO–CuO was explored. XRD and SEM revealed that the crystallite size and morphology varied with the vegetable waste extract. Similarly, the wide Eg of n-type ZnO narrowed upon coupling with p-type CuO, and also varied significantly with the vegetable waste extract. The resulting ZnO–CuO nanocomposites were used as photocatalysts for the degradation of model environmental pollutant (an organic dye) under visible light, and it was found that 95.6%, 93%, and 91.3% of the dye decomposes in 120 min under ZnO–CuO photocatalysts synthesized using cauliflower, peas, and potatoes waste extracts, respectively.

Visible-Light Driven Photocatalytic and Antibacterial Assessment of Ag/ZnO/Cellulose Nanocomposite

Ag/ZnO/cellulose nanocomposites were synthesised through in-situ solution casting method, which offers a good adhesion and dispersity of nanostructured materials. SEM analysis revealed formation of nanodiscs-like structures for ZnO while nanospheres and hierarchical nanosheets were observed for Ag and cellulose, respectively. XRD analysis pointed to the monoclinic type-1 phase of cellulose. Peaks corresponding to typical hexagonal wurtzite structure of ZnO and face-centredcubic Ag structure were also identified. Photodecomposition of aqueous methylene blue (MB) under direct sunlight irradiation was monitored to study the photocatalytic activity of the nanocomposite. About 92% of MB dye was photodegraded in the presence of Ag/ZnO/cellulose nanocomposite. The influence of Ag+ ions on the photocatalytic efficiency of ZnO is discussed. The antibacterial efficiency of the synthesised samples was investigated against two Gram positive pathogenic bacteria species: Staphylococcus aureus and a spore forming Bacillus subtilis as well as a Gram-negative Escherichia coli. The prepared nanocomposite exhibited strong activity against the growth of all the bacterial species though in different quantified measures.

Inhibition of Photocatalytic Activity of Basic Blue-41 by ZnO Modified Surface with Amino Silane

The reduction of the photo catalytic efficiency of ZnO can be achieved by modifying its surface with amino silane, which synthesized through condensation reaction under basic condition. The pH of solution was varied from 8 to 14 during the synthesis and was found that pH 12 was the most suitable pH for the preparation. All of ZMAS were characterized by Elemental Analysis which showed the highest percentage of nitrogen at 3.1064% and IR technique which indicated the Si-O-Zn bond at about 1000 cm-1. The photodegradation property of ZMAS prepared at pH 8-12 toward basic blue 41 was retarded when compared with the unmodified ZnO. Effect of mole ratio of ZnO:APTES (1:0.1, 1:0.5, 1:1, and 1:2) in the preparation of ZMAS was investigated. The photodegration activity of ZMAS prepared at mole ratio of ZnO:APTES as 1:0.5 to 1:2 toward basic blue 41 was retarded when compared with the unmodified ZnO. The coating of amino silane on ZnO surface did not have much effect on the band gap energy of modified ZnO. The absorption edge of ZMAS was only slightly shifted from 392 to 397 nm.

ZIF-8 derived Ag-doped ZnO photocatalyst with enhanced photocatalytic activity.

Recently, zeolitic imidazolate framework-8 (ZIF-8) has been widely studied and used as a catalyst in various fields, due to its high specific surface area, tunable channels and thermal and chemical stability. In this paper, ZIF-8 was used as a precursor to fabricate a Ag/ZnO photocatalyst, and the influence of Ag on the photocatalytic activity of ZnO has been explored. All samples were characterised using XRD, SEM, TEM, and UV-vis diffuse reflectance spectra. The photocatalytic activity of all samples was evaluated by the degradation of a rhodamine B solution under UV light. The results show that ZIF-8 was completely transformed into ZnO when it was calcined at 550 °C for 6 h, and Ag was well loaded onto ZnO. The photocatalytic efficiency of ZnO is 92.32%. When ZnO was doped with Ag, its photocatalytic efficiency was highly improved (99.64%). Furthermore, Ag/ZnO exhibited high photocatalytic stability. After five repeated cycles, the photocatalytic activity of Ag/ZnO was highly retained at 97.48%.

Synthesis of ZnO[sbnd]Al2O3 core-shell nanocomposite materials by fast and facile microwave irradiation method and investigation of their optical properties

Alumina (Al2O3) coated ZnO core-shell structures were synthesized by a novel, fast, and facile route utilizing microwave (MW) irradiation to control photocatalytic property of ZnO. The phase analysis and the core–shell structure development were corroborated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) analysis and Fourier transform infrared spectroscopy (FT-IR). The XPS results affirmed that elements on the coated surface were Al and O. Zeta potential analysis predicted the presence of Al2O3 layer on ZnO due to almost similar zeta potential curve for pure Al2O3 and Al2O3 coated ZnO nanoparticles. There was no significant change in band gap energy of ZnO after amorphous Al2O3 coating as obtained from derived data of the reflectance spectra but gradual decreasing of reflectance in the visible range, measured by UV–vis spectroscopy, of the prepared core-shell nanoparticle may be due to the coating of amorphous Al2O3 on ZnO. The photocatalytic efficiency of ZnO was reduced after amorphous Al2O3 layer as confirmed by the photodegradation of methylene blue under UV irradiation.

Enhancement of visible light photocatalytic activity of CdO modified ZnO nanohybrid particles

Highly effective ZnO–CdO nanohybrid particles were synthesized via a hydrothermal co-precipitation method and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FESEM), particle size analyzer, zeta sizer and Brunauer–Emmett–Teller (BET) surface area analysis. ZnO–CdO-3:1 nanohybrid photocatalyst exhibited significantly enhanced photostability and photocatalytic activity for the degradation of Methylene Blue. The formation of hydroxyl radicals was measured by photoluminescence (PL) spectroscopy. Photocatalytic efficiency of ZnO was high at ZnO–CdO ratio of 3:1. Furthermore, this work provides an insight into the development of a new photocatalyst for the degradation of organic contaminants.

Synthesis of ZnO–Pt nanoflowers and their photocatalytic applications

The photocatalytic behaviors of ZnO nanoparticles have been intensively studied recently.However, the photocatalytic efficiency of pure ZnO nanoparticles always suffers from thequick recombination of photoexcited electrons and holes. In order to suppressthe electron–hole recombination and then raise the photocatalytic efficiency ofZnO, metal nanoparticles have been combined with ZnO to form ZnO–metalheterostructures. In this work, the feasibility of synthesizing ZnO–Pt composite nanoflowersfor optimized catalytic properties was studied. Three different Pt nanocrystals,i.e. cubic Pt nanocrystals enclosed by {100} facets, octahedral Pt nanocrystals enclosedby {111} facets, and truncated octahedral Pt nanocrystals enclosed by both {111}and {100} facets, were selected as seeds for epitaxial growth of ZnO. A ZnO–Ptflowerlike nanostructure was formed by selective growth of ZnO nanolobes at {111}facets of the truncated octahedral Pt nanocrystals. The resultant nanoflowershad well defined ZnO–Pt interfaces and exposed Pt {100} facets, as confirmed bytransmission electron microscopy (TEM) and high-resolution TEM (HRTEM)measurements. The photocatalytic behaviors of the resultant ZnO–Pt nanoflowers weredemonstrated in the photodegradation of ethyl violet. In comparison with the commercialTiO2 photocatalyst P25, the ZnO–Pt flowerlike nanostructures showed improved catalyticefficiency. Notable ferromagnetism of the obtained ZnO–Pt flowerlike nanostructures wasalso observed. It is believed that the ZnO–Pt interface played an important role in theenlarged magnetic coercivity of the ZnO–Pt nanoflowers.