Photocatalytic Activity Of ZnO Nanorods Research Articles

Evaluation of the photocatalytic activity of ZnO nanorods and nanoflowers grown from seed layers deposited by spin coating

The increase in pollution, using photocatalytic materials to degrade organic pollutants remains in force. ZnO is the most used semiconductors for photocatalytic applications. The oriented growth of nanostructures on substrates or seed layers (SL) improves the physical and chemical properties compared to the bulk-grown material. In this work, the photocatalytic efficiency of ZnO nanorods and nanoflowers was evaluated, obtained by hydrothermal growth (HG) over SL deposited by the spin-coating technique (SCT). The characterizations results showed two types of growth: 1D nanostructures with a dimension in the range of 400–1000nm and diameters of 70–100nm, and 1D microstructures with approximate 5–11μm length and diameters of 1–2μm. However, in the 7 SL system, micro prisms were generated, which led to the formation of 3D nanostructures (micro flowers) of ZnO with a maximum of 6μm in diameter. The system with 1D and 3D ZnO nanostructures, grown in 7 SL, was the most efficient methylene blue degradation. Achieving 100% transformation in 120min, with a rate constant of 2.98×10−2min−1. The results show that the SCT deposit combined with the sol–gel method and HG produces 1D and 3D structures with high potential in photocatalytic degradation.

The effects of nanofibrous seed layer and stoichiometry of CBD process on microstructural, electro-optical and photocatalytic activity of ZnO nanorods for oxytetracycline degradation

In the present study, we applied a nanofibrous ZnO seed layer and modified the stoichiometry of the ZnO nanorods (NRs) by Al and Cu doping. The microstructure, crystallography, electro-optical, and photocatalytic properties of ZnO NRs were studied. The microstructure studies indicated that changing the stoichiometry resulted in the formation of imperfect ZnO NRs. Also, the columnar growth factor decreased. In contrast, extra emissions were observed in the photoluminescence spectra issued by further defects in non-stoichiometric ZnO NRs. The results exhibited a higher photon absorption and optical bandgap for stoichiometric ZnO NRs. The hydrophobicity of stoichiometric ZnO NRs decreased by incorporating Al and Cu. By evaluating the photocatalytic activity, it was found that ZnO NRs perfectly aligned hexagonal morphology was more effective in the photocatalytic process than having further point defects. The kinetics study showed a better activity for stoichiometric ZnO NRs to degrade oxytetracycline (OTC). The highest photocatalytic efficiency was obtained 46.27 % for stoichiometric ZnO NRs.

Uncovering the Role of Surface-Attached Ag Nanoparticles in Photodegradation Improvement of Rhodamine B by ZnO-Ag Nanorods.

ZnO nanorods decorated with metal nanoparticles have sparked considerable interest in recent years thanks to their suitability for a wide range of applications, such as photocatalysis, photovoltaics, antibacterial activity, and sensing devices. In this study, we prepared and investigated the improved solar-light-assisted photocatalytic activity of ZnO nanorods (NRs) decorated with Ag nanoparticles (NPs) using a conventional rhodamine B (RB) dye as a model water pollutant. We showed that the presence of Ag NPs on the surface of ZnO NRs significantly increases the degradation rate of RB dye (~0.2432 min−1) when compared to bare ZnO NRs (~0.0431 min−1). The improved photocatalytic activity of ZnO-Ag was further experimentally tested using radical scavengers. The obtained results reveal that ˙OH and ˙O2− radicals are main active species involved in the RB dye photodegradation by ZnO-Ag NRs. It was concluded that efficient charge separation plays a major role in photocatalytic activity improvement.

Enhanced Photocatalytic Activity of ZnO Nanorods/(Graphene Oxide, Reduced Graphene Oxide) for Degradation of Methyl Orange Dye

ZnO has been well-known as a significant photocatalyst material due to its high surface area, efficient charge transport, and superior photosensitivity. Even though photocatalysis using bare ZnO NRs is useful in pollutant remediation, two main drawbacks scale down their performance as photocatalysts. First, ZnO NRs absorb mainly the UV light, which compromises a small portion of the solar spectrum, and second, the high recombination rate in the ZnO NRs prevents the path of electron-hole outward and then reduces the photocatalysis efficiency. In this work, ZnO-NRs, ZnO-NRs/Graphene Oxide (GO), and ZnO-NRs/Reduced Graphene Oxide (rGO) array composites were vertically grown on conductive glass substrates of SnO2:F (FTO). The films were synthesized by hydrothermal method using ZnO seed layers deposited by spray pyrolysis technique. The nanosheets of GO and rGO were anchored onto the surface of the as-prepared ZnO-NRs by using the spray deposition technique (SDT). The photocatalytic activity of these materials was studied by analyzing the degradation of methylene orange (MO) in an aqueous solution under ultraviolet light, and we found that the decoration of ZnO-NRs with nanosheets of GO and rGO resulted in a significant enhancement of the photocatalytic degradation efficiency, where ZnO-NRs/rGO are more efficient than ZnO-NRs/GO and the latter better than pure ZnO-NRs.

Structure, morphology and photocatalytic activity of ZnO nanorods fabricated by electrochemical deposition

We report the investigation of structure, morphology, photocatalytic degradation of methyl blue using ZnO nanorods (NRs). The ZnO NRs samples were fabricated using electrochemical deposition from aqueous solution of zinc nitrate and hexamethylenetetramine on ITO substrates. The effect of the growth time on the structure, morphology and photocatalytic properties of ZnO NRs was investigated in details.XRD analysis showed that the fabricated NRs have hexagonal wurtzite structure and growth direction along the (002) plane. The morphology of the prepared samples investigated by SEM showed that growth rate of the NRs depends on the time of the growth. The surface area and cross-sectional area of the fabricated ZnO NRs increased with increasing the growth time and led to improvements in the NRs aspect ratios. It was also found that the photocatalytic activity of the grown nanorods enhances by increasing the deposition time. The present results are discussed in terms of the observed structural morphology of the investigated ZnO NRs and correlated with the photocatalytic performance of the grown NRs.

Enhanced photocatalytic activity of ZnO nanorods by surface treatment with HAuCl4: Synergic effects through an electron scavenging, plasmon resonance and surface hydroxylation

In this research, we demonstrate an enhanced photocatalytic activity (PA) of ZnOR/Au composites compared to PA of plain ZnOR structures. The ZnOR were produced by a hydrothermal growth method and the surface treatment of the ZnOR crystals was carried out with HAuCl4 using a spin coating technique. In this study, methyl orange was chosen to evaluate the photocatalytic activity of the ZnOR and ZnOR/Au. The highest degradation efficiency of MO was achieved with ZnOR/Au layers. The XPS and wettability measurements have confirmed the increase in the amount of hydroxyl groups on the surface of the ZnOR/Au. Taking into account the physical and chemical characterizations of the samples, the enhanced photocatalytic activity of the ZnOR/Au composites has been attributed to the three main issues 1) an effective charge carries separation due to proper ZnO and Au bands alignment where the gold acts as an electron scavenger, 2) surface plasmon resonance from Au nanoparticles 3) increase of the hydroxylation of the ZnOR crystals surface after HAuCl4 interaction with ZnOR surface.

Mxene enhanced the photocatalytic activity of ZnO nanorods under visible light

MXene is a novel metal compound with narrow band gap and has been widely applied in energy storage, solar energy cells, and hydrogen production. A simple technique was used to attain MXene, and then the ZnO nanorods/MXene (ZnO-MX) hybrids were fabricated by ultrasonic oscillation. Experimental results illustrated that MXene sheets were decorated by ZnO nanorods, and the resultant ZnO-MX hybrids possessed higher removal ability of Rhodamine B (RhB) than pure ZnO nanorods, in which the removal efficient was 3.2 times as fast as pure ZnO nanorods (0.0077 min−1) under visible light irradiation. Additionally, the photocatalytic hydrogen production of ZnO nanorods was improved by MXene sheet significantly. The enhancement was because MXene sheet increased the surface area of ZnO nanorods and reduced the resistance of transferring photo-engendered carriers, indicating that MXene sheet can serve as suitable carrier for photocatalytic materials.

Synergistic effect of a cobalt dopant and Au nanoparticles on the photocatalytic activity of ZnO nanorods

The photocatalytic performance of zinc oxide nanorods (ZnO NRs) still needs improvement. In this regard, the addition of noble-metal nanoparticles (NPs) and doping with transition metals can be employed. In this study, nanocomposites of ZnO NR/Au and Co-doped ZnO NR/Au NPs were synthesized by ultrasonic spray pyrolysis and hydrothermal method and subsequently used as photocatalysts for the degradation of methylene blue. Results revealed that pure ZnO NRs exhibit a degradation rate of only 28.8%, while ZnO NR/Au NPs exhibit a degradation rate of 37.3%, and Co-doped ZnO NR/Au NPs exhibit the highest degradation rate of up to 46.5%. Based on these results, the presence of Au on the ZnO NR surface can enhance the photocatalytic activity due to its key role as an electron sink, which reduces the recombination rate of electrons and holes, while the incorporation of Co into ZnO NRs can also enhance the number of crystal defects, which can widen the visible-light absorption spectrum.

Bayberry-like Pt nanoparticle decorated ZnO nanorods for the photocatalytic application

The preparation of the nanocomposites zinc oxide/platinum (ZnO/Pt) has attracted much attention with regard to improving the photocatalytic efficiency of ZnO, but most studies have focused on the use of ZnO/Pt in conventional powdered spherical nanocrystals only. In this experiment, bayberry-like Pt nanoparticles (NPs) were successfully synthesized and deposited on the surfaces of ZnO nanorods (NRs) that were hydrothermally grown on glass substrates. The bayberry-like Pt NPs, which had a diameter range of 40–70 nm and consisted of many nanodots with a diameter < 5 nm, were spread uniformly on the surface of the ZnO NRs via the drop-casting method. The presence of the Pt NPs increased the photocatalytic activity of ZnO NRs for methylene blue (MB) degradation by 54% and 32% under UV and visible light irradiation, respectively. This improvement can be attributed to the presence of Pt, which acted as an electron trap and can inhibit the rate of electron–hole recombination. It may also be credited to the morphology of the bayberry-like Pt NPs, which consisted of many nanodots that can trap light in the surroundings of the nanodots, thereby enhancing the light scattering and absorption and enlarging the surface area for oxygen and hydroxyl ion adsorption.

Synthesis and characterization of aligned ZnO nanorods for visible light photocatalysis

Aligned ZnO nanorods (NRs) were synthesized by a simple and inexpensive hydrothermal method. Morphological, structural, photoabsorbance and photoluminescence studies have been carried out using field emission scanning electron microscopy (FE-SEM), grazing incidence X-ray diffraction (GIXRD), Raman, UV–visible and Photoluminescence spectroscopy. Results show that crystallinity and alignment of ZnO NRs lead to good photocatalytic activity in the presence of visible light. The Photoluminescence spectra revealed a decrease in the UV emission, suggesting a reduced recombination of the photo generated carriers. The visible region emission is due to the surface oxygen vacancies. Increase of charge separation rate observed from emission spectra and the vacancy related sub-bands in the absorbance spectra are together responsible for the enhanced visible light photocatalytic activity of ZnO NRs. Vertically aligned 1-D morphology of ZnO NRs and the presence of oxygen vacancy states assist in the visible light photocatalytic degradation of Methylene Blue dye.

Enhancement of sunlight-induced photocatalytic activity of ZnO nanorods by few-layer MoS2 nanosheets

Few-layer exfoliated MoS2 nanosheets were easily composited with ZnO nanorods. It was found that MoS2 nanosheets could enhance the sunlight-induced photocatalytic activity rate of ZnO by 74%. In addition, we showed that under UV-blocked sunlight irradiation, MoS2 weakens the photocatalytic activity rate of ZnO by 33%. Finally, we discussed the mechanisms behind the enhanced (weakened) photocatalytic activity under sunlight (UV-blocked sunlight) irradiation based on the UV-Vis absorption and photoluminescence spectra as well as the potential band diagrams of the ZnO/MoS2 composite.

Voltage-assisted photocatalytic activity of ZnO nanorods grown on carbon fabric for effluent treatment

The disposal of colored textile effluent into canals, rivers and sea has adverse effect on aquatic plants and animal life due to reduced penetration of sunlight into water. The aim of this study was to investigate the color removal of textile dyeing effluents with voltage-assisted photocatalytic activity of carbon fabrics containing ZnO nanorods. ZnO nanorods were grown on the oxidized carbon fabric samples by seeding technique using zinc acetate dihydrate and NaOH, followed by hydrothermal process using zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (C6H12N4). The surface morphology of functionalized carbon fabric was characterized using scanning electron microscope, transmission electron microscope and X-ray diffractometer. It was found that the degradation of dyes in aqueous solutions, with voltage-assisted photocatalytic activity of ZnO nanorods on carbon fabrics, follows Langmuir-Hinshelwood kinetics. The study concludes that increase in the applied voltage significantly increases the rate of degradation of dyes by enhancing the photocatalytic activity of carbon fabrics containing ZnO nanorods.

Preparation and photocatalytic activity of ZnO nanorods and ZnO/Cu2O nanocomposites

Preparation and photocatalytic activity of ZnO nanorods and ZnO/Cu2O nanocomposites

Controllable synthesis and photocatalytic activity of ZnO nanorods

ABSTRACTZnO nanorods were successfully synthesized by a microwave-assisted chemical method. The as-prepared ZnO particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM, X-ray photoelectron spectra (XPS), and X-ray diffraction (XRD). It is found that ZnO nanorods with diameters around 20–30 nm and lengths in the range of 60–80 nm were synthesized. The products showed good photocatalytic performance under UV light irradiation. The ZnO nanorods also showed excellent photostability and reusability under UV-visible light irradiation.

Enhanced Photocatalytic Activity of ZnO Nanorods with Tubular Facet Synthesized by Hydrothermal Method

Enhanced Photocatalytic Activity of ZnO Nanorods with Tubular Facet Synthesized by Hydrothermal Method

Photoluminescence and photocatalytic activities of Ag/ZnO metal-semiconductor heterostructure

Present article focuses on the photocatalytic activities of ZnO nanorods and Ag/ZnO heterostructure deposited on polyethylene terephthalate (PET) substrate. ZnO nanorods are synthesized by thermal decomposition technique and Ag nanoparticles deposition is done by photo-deposition technique using UV light. X-ray diffraction studies reveal that the ZnO nanorods are of hexagonal wurtzite structure. Further, as-prepared samples are characterized by Scanning Electron Microscopy (SEM), Photoluminescence (PL) spectroscopy and UV-Vis spectroscopy. The surface plasmon resonance response of Ag/ZnO is found at 420 nm. The photocatalytic activities of the samples are evaluated by photocatalytic decolorization of methyl orange (MO) dye with UV irradiation. The degradation rate of MO increases with increase in irradiation time. The degradation of MO follows the first order kinetics. The photocatalytic activity of Ag/ZnO heterostructure is found to be more than that of ZnO nanorods. The PL intensity of ZnO nanorods is stronger than that of the Ag/ZnO heterostructure. The strong PL intensity indicates high recombination rate of photoinduced charge carriers which lowers the photocatalytic activity of ZnO nanorods. The charge carrier recombination is effectively suppressed by introducing Ag nanoparticles on the surface of the ZnO nanorods. This study demonstrates a strong relationship between PL intensity and photocatalytic activity.

Effect of Ni coupling on the photoluminescence property and photocatalytic activity of ZnO nanorods

ZnO nanoparticles are promising UV light driven photocatalyst for the degradation of organic dyes. In this work, we demonstrated that the photocatalytic activity of ZnO nanoparticles could be improved by coupling with Ni particles. The Ni coupled ZnO nanorods were synthesized by two steps solution precipitation method. The surface plasmon resonance stimulated by the defect transition experienced by Ni coupled ZnO nanorods caused quenching of visible emission but enhancing of UV emission in RTPL analysis. The photodegradation of RhB solution in the presence of Ni coupled ZnO nanorods under UV irradiation followed first-order kinetic. The best photodegradation efficiency, i.e. 64% of RhB removal after 90 min UV irradiation with rate constant of 0.0119 min−1, was achieved when ZnO nanorods coupled with Ni nanoparticles prepared at 0.03 M nickel nitrate were used. The Ni nanoparticles acted as electron traps, pro-longing the charge separation duration. The scavenger test shows that holes and hydroxyl free radical were the dominant reactive species in the photocatalytic degradation of RhB dye by Ni coupled ZnO nanorods under UV irradiation. A refined photodegradation mechanism of RhB dye by Ni coupled ZnO nanorods is proposed based on these findings.

A synergetic effect of surface plasmon and ammoniation on enhancing photocatalytic activity of ZnO nanorods

A synergetic effect of surface plasmon (SP) and ammoniation on the enhancements of both ultraviolet and visible photocatalytic activities of ZnO nanorods is reported.

Template free large scale synthesis of multi-shaped ZnO nanostructures for optical, photocatalytical and antibacterial properties

In this article, ZnO nanostructures with diverse morphologies have been synthesized via a simple, rapid and cost effective solid state thermal decomposition method. The as-synthesized ZnO nanostructures were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), UV–Vis. diffuse reflectance spectra (UV–Vis-DRS) and photoluminescence (PL). The XRD patterns and HR-TEM image indicated a hexagonal wurtzite structure of ZnO. The SEM images of ZnO samples show the different morphologies such as nanowire, nanorods, spherical and irregular microsphere at different calcination temperatures. Room temperature PL spectra of the samples exhibited characteristics blue and green emission bands in accordance with calcination temperature. Moreover, photocatalytic as well as antimicrobial activities were evaluated using ZnO synthesized at different calcination temperatures. The effects of calcination temperature, catalyst loading and pH on the photodegradation efficiency were systematically studied. A highest (99 %) photocatalytic activity of ZnO nanorods towards the Acid Green 25 (AG-25) was achieved within 35 min at optimal conditions under UV light. As-synthesized ZnO nanorods are found to be more efficient than TiO2 (P25) towards the degradation of AG-25. It was found that the antimicrobial activity of ZnO nanorods (13 mm) obtained at 300 °C showed significantly higher inhibition efficiencies than the other samples. The mineralization of AG-25 was confirmed from a reduction of 85 % the chemical oxygen demand within 35 min. In addition, ZnO nanorods could be easily reusable up to four runs without changing its photocatalytic activity.

Enhanced photocatalytic activity of ZnO nanorods grown on Ga doped seed layer

ZnO nanorods have been successfully grown on Ga doped (0–5wt%) ZnO seed layer by using simple hydrothermal method. Changing Ga content in the seed layers lead to formation of ZnO nanorods with high aspect ratio and increased density. The effects of Ga doped seed layer on optical and structural morphology of ZnO nanorods are investigated in detail by using Field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and Photo luminescence spectroscopy (PL). It has been observed that the Ga doped seed layer strongly affected the structural morphology of ZnO nanorods. XRD results show that all the samples have hexagonal wurtzite shape and (002) is preferred direction of growth. The intensity of (002) peak increases with increasing Ga concentration in seed layer indicating that the Ga doped seed layer has promoted growth of nanorods along (002). SEM images show a decrease in diameter of ZnO nanorods with increasing Ga concentration in seed layer. The PL spectra of all the samples have two emission bands, UV and defect emission. UV emission shows a small blue shift with increasing Ga concentration in seed layer. The photocatalytic activity of as grown ZnO nanorods increases with aspect ratio (length) and density.