Hexagonal Zinc Oxide Nanoparticles Research Articles

Low‐temperature synthesis of maize straw biochar‐ZnO nanocomposites for efficient adsorption and photocatalytic degradation of methylene blue

AbstractAs a new type of environmental functional material, biochar composites have become the focus of considerable interest in wastewater treatment research owing to their excellent adsorption and photocatalytic properties. However, the fabrication of cost‐effective biochar composites with high photocatalytic efficiencies at low synthesis temperatures remains challenging. In this study, biochar was prepared using an environmentally friendly hydrothermal method at a low temperature with maize straw as the waste material, instead high costs pyrolysis process. Hexagonal zinc oxide nanoparticles were grown in and on the biochar framework using the chemical deposition method. The adsorption and photocatalytic degradation performance of aqueous methylene blue (MB) solutions were investigated. We demonstrated that the photocatalytic degradation performance of the biochar‐ZnO composites was considerably higher than that of the most other reports. The degradation of the MB solutions (60 mg/L) reached 98.0 % in 240 min under low‐power ultraviolet light (50 W) irradiation. We propose that the synergetic effect of the high adsorption of the porous biochar and the photocatalytic activity of ZnO led to a high degradation efficiency. This study provides theoretical and practical guidance for the preparation of photocatalytic composites obtained from waste biomass materials by a cost‐efficient, fast, and environmentally friendly method, and the efficient degradation of dye pollutants in water.

Zinc oxide Nanoparticles, Biosynthesis, characterization and their potent photocatalytic degradation, and antioxidant activities

ObjectivesThis study aimed to biosynthesize zinc oxide nanoparticles (ZnO-NPs) using the seed extract of Moringa oleifera. The catalytic activity of the biosynthesized ZnO-NPs was examined as photocatalyst for the degradation methylene blue (MB) and their antioxidant activity by H2O2 assay were studied. MethodsThe biosynthesized ZnO-NPs and their physicochemical properties investigated via UV–visible spectroscopy (UV–vis), Fourier transform infrared (FTIR) spectroscopy, Transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray diffraction analysis (XRD) analysis, and zeta potential was calculated using the Zetasizer nano. ResultsUV–Visible analysis of the biosynthesized nanoparticles revealed the characteristic a specific peak at 375 nm indicating the formation of ZnO-NPs. XRD study showed a distinctive diffraction peak indicating the formation of crystalline nanoparticles which matches to the spherical and hexagonal structure of ZnO-NPs. TEM results confirmed the formation of spherical and hexagonal ZnO-NPs and the size ranging between 25 and 30 nm. EDX analysis was used for the determination of elemental composition of biosynthesized ZnO-NPs which included zinc, oxygen and carbon. FTIR spectroscopy is useful to determine the available functional group from the phytochemical components implicated in the stabilization and reduction of ZnO-NPs. ZnO-NPs exhibited effective photocatalytic activity in degrading methylene blue (MB) and maximum photocatalytic activity (71 %) after 24 hrs. In addition, ZnO NPs exhibited high antioxidant activity against H2O2 free radicals scavenger. ConclusionThe biosynthesized ZnO-NPs have excellent MB dye degradation power and complete dye degradation was achieved within 24 hrs and synthesized ZnO-NPs showed improved antioxidant power. ZnO-NPs are good tools for industrial applications.

ZnO/Zn(OH)2 nanoparticles and self-cleaning coatings for the photocatalytic degradation of organic pollutants

Zinc oxide (ZnO) nanostructures have emerged as efficient heterogeneous photocatalysts for the degradation of organic pollutants in aqueous solutions and industrial wastewaters. In this work, a simple and effective method is reported for the synthesis of zinc oxide/zinc hydroxide (ZnO/Zn(OH)2) hybrid nanoparticles using a mineral acid to enhance the photocatalytic activity of ZnO. Infrared spectroscopy reveals the presence of hydroxyl groups in ZnO/Zn(OH)2 nanoparticles. X-ray diffraction shows the formation of hexagonal wurtzite ZnO nanoparticles, which retain their wurtzite structure after acid treatment but additional diffractions for Zn(OH)2 are also recorded. The optical bandgap of resulting ZnO and ZnO/Zn(OH)2 nanoparticles is reduced to 3.05 and 3.08 eV, respectively. In the initial photocatalysis experiments, ZnO/Zn(OH)2 nanoparticles exhibit 3.5-times improved degradation and removal of sunset yellow dye, a model organic pollutant, from deionized water compared to pristine ZnO nanoparticles. Hence, for further studies, ZnO/Zn(OH)2 coatings are fabricated on glass slides with a uniform surface morphology as shown by the atomic force microscopy. The time-dependent UV-visible spectroscopy reveals the photocatalytic degradation of sunset yellow over the surface of ZnO/Zn(OH)2 coatings. The degradation reaction follows the pseudofirst-order mechanism with a rate constant of 2.9 × 10–2 min−1. The recyclability and stability experiments reveal the retention of appreciable photocatalytic activity of ZnO/Zn(OH)2 coatings (with >92% degradation efficiency after six successive cycles). The results are compared with recent examples from the pertinent literature. The surface hydroxyl groups on ZnO/Zn(OH)2 nanoparticles and bandgap lowering enhance the anchoring of dye molecules and electron transfer reactions.

Biogenic Synthesis of CuO, ZnO, and CuO-ZnO Nanoparticles Using Leaf Extracts of Dovyalis caffra and Their Biological Properties.

Biogenic metal oxide nanoparticles (NPs) have emerged as a useful tool in biology due to their biocompatibility properties with most biological systems. In this study, we report the synthesis of copper oxide (CuO), zinc oxide (ZnO) nanoparticles (NPs), and their nanocomposite (CuO–ZnO) prepared using the phytochemical extracts from the leaves of Dovyalis caffra (kei apple). The physicochemical properties of these nanomaterials were established using some characterization techniques including X-ray diffraction analysis (XRD), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The XRD result confirmed the presence of a monoclinic CuO (Tenorite), and a hexagonal ZnO (Zincite) nanoparticles phase, which were both confirmed in the CuO–ZnO composite. The electron microscopy of the CuO–ZnO, CuO, and ZnO NPs showed a mixture of nano-scale sizes and spherical/short-rod morphologies, with some agglomeration. In the constituent’s analysis (EDX), no unwanted peak was found, which showed the absence of impurities. Antioxidant properties of the nanoparticles was studied, which confirmed that CuO–ZnO nanocomposite exhibited better scavenging potential than the individual metal oxide nanoparticles (CuO, and ZnO), and ascorbic acid with respect to their minimum inhibitory concentration (IC50) values. Similarly, the in vitro anticancer studies using MCF7 breast cancer cell lines indicated a concentration-dependent profile with the CuO–ZnO nanocomposite having the best activity over the respective metal oxides, but slightly lower than the standard 5-Fluorouracil drug.

Heterostructures of mixed metal oxides (ZnMnO3/ZnO) synthesized by a wet-chemical approach and their application for the electrochemical detection of the drug chlorpromazine

Materials development using heterostructures is generally considered an efficient method for developing electrocatalysts . However, it still faces many challenges, such as instability and accurate phase mixing ratio of metals. On the other hand, the excessive consumption of drugs such as chlorpromazine (CPMZ) leads to several serious human diseases. Therefore, the accurate detection and determination of CPMZ is essential. In this view, a highly efficient electrochemical sensor based on a heterostructure of ZnMnO 3 /ZnO NPs/GCE was fabricated to detect the psychotic drug CPMZ. The heterostructure of cubic ZnMnO 3 (ZMO) and hexagonal zinc oxide nanoparticles (ZMO/ZnO NPs) was synthesized by a simple co-precipitation method followed by thermal calcination . The as-prepared material crystallinity and average crystal size (26 nm) were analyzed by p-XRD. The morphology of the ZMO/ZnO NPs was analyzed by SEM and HR-TEM, which revealed the formation of non-uniform spherical and hexagonal nanoparticles with a size of ∼10-30 nm. FT-IR and XPS were used to investigate the functional groups and oxidation states of the ZMO/ZnO NPs. The electrochemical properties of the ZMO/ZnO NPs/GCE were analyzed by EIS , CV , and DPV methods. ZMO/ZnO/GCE has improved electrochemical activity for detecting CPMZ. In addition, the ZMO/ZnO/GCE electrochemical probe has two linear ranges (0.05–125.55 μM and 185.55–1625 μM) and good sensitivity (0.760 μA μM −1 cm −2 ) with a low detection limit of 0.019 μM. Analysis of real samples was performed in human blood serum and urine, and the recoveries of CPMZ were 96–100% and 98–100%, respectively.

Graphene Oxide Supported Cubic ZnO for Enhanced Photodecomposition of Dyes

AbstractA new nanocomposites photocatalyst was fabricated including cubic zinc oxide (ZnO) and the graphene oxide (GO) by simple solvothermal method. The hexagonal ZnO nanoparticles with cubic shapes were acquired via calcination of zeolitic imidazolate framework‐8 (ZIF‐8) pyrolysis at 450 °C. The result of optical absorption property and photoelectrochemical performance showed that GO enhanced the photocatalytic performance of ZnO due to the enhanced visible light absorption, the fewer electron‐hole pairs recombine, the efficient transfer of electron‐hole pairs and effectively reduced the accumulation of ZnO. The ZnO‐GO nanocomposites photocatalyst was demonstrated remarkable degradation performance that almost completely degraded Rhodamine B (RhB) in 40 min and Methyl orange (MO) in 100 min under sunlight. It also exhibits good recyclability after 5 cycles that keep high photocatalytic efficiencies of 94 %. This kind of catalyst with photocatalytic activity and stable performance is expected to be widely used in the photocatalytic degradation of dyes, heavy metal ions, antibiotics and other fields.

Structural and spectroscopic analysis of pure phase hexagonal wurtzite ZnO nanoparticles synthesized by sol-gel

In the present study, Sol-gel route was employed to synthesize the pure phase hexagonal wurtzite zinc oxide (ZnO) nanoparticles with crystallite size and lattice strain ~ 21 nm and ~ 7.6 × 10-4 respectively. The synthesized ZnO nanoparticles were characterized by X-ray Powder Diffraction (XRPD), Fourier Transform Infrared (FTIR) Spectroscopy and Raman spectroscopy at room temperature. FTIR spectrograph demonstrates the presence of stretching vibration of Zinc-Oxygen (Zn-O) bonding. The Raman active optical phonon mode E2High at 438.59 cm−1 confirms the formation of pure phase wurtzite hexagonal ZnO nanoparticles.

Hylotelephium telephium Flower Extract-Mediated Biosynthesis of CuO and ZnO Nanoparticles with Promising Antioxidant and Antibacterial Properties for Healthcare Applications

The present work mainly concentrates on the biosynthesis of copper oxide (CuO) nanoparticles (NPs) and zinc oxide (ZnO) nanoparticles using Hylotelephium telephium subsp. telephium flower extract. XRD study confirms the formation of monoclinic CuO NPs and hexagonal ZnO NPs. SEM and TEM analyses show that the CuO NPs were spherical in shape of 83 nm in size, whereas the ZnO NPs were irregular in shape of 36 nm in size. The synthesized nanoparticles have excellent antioxidant and antibacterial activities. The antioxidant activity results reveal that the synthesized nanoparticles exhibit excellent free radicals scavenging activity. A comparative study on the antibacterial activity of the chemically synthesized nanoparticles and biosynthesized nanoparticles was conducted and it was found that the biosynthesized nanoparticles possess better activities than the chemically synthesized nanoparticles. Hence, biosynthesis is a more advantageous and reliable method when compared to chemical synthesis for the production of nanoparticles for antibacterial applications.

X-RAY ANALYSIS FOR DETERMINATION THE CRYSTALLITE SIZE AND LATTICE STRAIN IN ZnO NANOPARTICLES

Zinc oxide (ZnO) nanoparticles were synthesized by modified hydrothermal method at 160oC under different reaction times. The analysis of the XRD pattern lines is considered a simple and effective method in estimating the crystallite size and the corresponding lattice strain. X-ray patterns were analyzed using Scherrer method and Williamson–Hall treatment to determine the crystallite size and the lattice strain. The XRD pattern confirmed the presence of crystalline hexagonal wurtzite ZnO nanoparticles with average crystallite size in the range 30 –36 nm with different reaction times. ZnO nanoparticles were also characterized by high resolution transmission electron microscopy (HR-TEM), UV-visible spectroscopy and thermal analysis.

Exploiting in vitro potential and characterization of surface modified Zinc oxide nanoparticles of Isodon rugosus extract: Their clinical potential towards HepG2 cell line and human pathogenic bacteria.

Little is known about biogenically synthesized Zinc oxide nanoparticles (ZnONPs) from Isodon rugosus. Synthesis of metal oxide NPs from essential oil producing medicinal plants results in less harmful side effects to the human population as compared to chemically synthesized NPs. In this article, we report biogenic synthesis of ZnONPs from in vitro derived plantlets and thidiazuron (TDZ) induced callus culture of Isodon rugosus. Synthesized NPs were characterized using UV-spectra, XRD, FTIR, SEM and EDX. Furthermore, the NPs were evaluated for their potential cytotoxic (against HepG2 cell line) and antimicrobial (against drug resistant Staphylococcus epidermidis, Bacillus subtilis, Klebsiella pneumoniae and Pseudomonas aeruginosa) activities. Pure crystalline ZnONPs with hexagonal and triangular shapes were obtained as a result of callus extract (CE) and whole plant extract (WPE), respectively. ZnONPs showed potent cytotoxic and antimicrobial potential. The antimicrobial and cytotoxic activities of ZnONPs were found to be shape and surface bound phytochemicals dependent. CE mediated hexagonal ZnONPs showed superior anti-cancer and antimicrobial activities as compared to WPE mediated triangular shaped ZnONPs. It is concluded that biogenic ZnONPs have incredible potential as theranostic agents and can be adopted as useful drug delivery system in next generation treatment strategies.

One-pot green synthesis of zinc oxide nano rice and its application as sonocatalyst for degradation of organic dye and synthesis of 2-benzimidazole derivatives

In this paper, we report novel and green approach for one-pot biosynthesis of zinc oxide (ZnO) nanoparticles (NPs). Highly stable and hexagonal phase ZnO nanoparticles were synthesized using seeds extract from the tender pods of Parkia roxburghii and characterized by XRD, FT-IR, EDX, TEM, and N2 adsorption-desorption (BET) studies. The present method of synthesis of ZnO NPs is very efficient and cost effective. The powder XRD pattern furnished evidence for the formation of hexagonal close packing structure of ZnO NPs having average crystallite size 25.6nm. The TEM image reveals rice shapes ZnO NPs are with an average diameter of 40–60nm. The as-synthesized ZnO NPs has proved to be an excellent sonocatalysts for degradation of organic dye and synthesis of 2-benzimidazole derivatives.

Preparation, characterization and photocatalytic activity of hexagonal ZnO nanoparticles

Hexagonal zinc oxide (ZnO) nanoparticles were synthesized via thermal decomposition of precursors prepared from carboxylic acids, such as oxalic, citric or tartaric acids, using a promising method. The as-prepared precursors were studied using thermal gravimetric analysis (TGA). The materials resulting from the heat treatment were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their specific surface areas were determined using the BET method to be approximately 20m2/g. The particle size was determined to be 40nm based on TEM and 25nm calculated from XRD. Therefore, the crystallite dimensions were confirmed to be on the nanoscale. All of these zinc oxide samples have exhibited very good efficiency for photodegradation of methylene blue (MB), which was used as a standard pollutant, under UV light irradiation.

Deposition and super liquid repellency of fluorinated ZnO nanoparticles on carbon fabrics

The liquid-repellent behavior of fluorinated zinc oxide (ZnO) nanoparticles deposited onto carbon fabric (CF) by a pulse microwave-assisted (MA) method followed by surface fluorination treatment was investigated. The MA process is performed at 80°C within 10min with different pH values of 5.5, 8 and 12. The hexagonal ZnO nanoparticles with an average size of 100nm exhibit a well-defined wurtzite crystal structure without any heat treatment. The ZnO nanoparticles produced by MA synthesis at pH=8 display the maximal density over CF substrate. The fluorination coating effectively imparts super water and oil repellencies on the ZnO–CF surface; i.e., the contact angles are 163° (water) and 153° (ethylene glycol, EG). The liquid repellencies toward water and EG droplets show an increasing function of surface density of ZnO nanoparticles. This result can be attributed to the fact that an air layer is confined in the nanoparticles, thereby inducing a rougher gas–vapor–solid contact line, referred to as the Cassie state. Based on the Young–Duprè equation incorporated with the Cassie parameter, the lowest work of adhesion (Wad) values of the ZnO–CF surface for water and EG repellencies are estimated to be 3.16 and 4.93mJ/m2, respectively. Accordingly, this work sheds some light on the creation of a two-tier texture by an efficient MA route and on how the surface density of ZnO nanoparticles strongly affects the repellent behavior of the resultant ZnO–CF composites.

Synthesis, characterization, and photocatalytic activities of titanate nanotubes surface-decorated by zinc oxide nanoparticles

Nanoscaled zinc oxide (ZnO) particles with different amounts are coated on titanate nanotubes (TNTs) by a facile chemical method at room temperature. The characterizations of XPS, TEM, XRD and UV–vis spectra confirm that pure hexagonal wurtzite ZnO nanoparticles with an average size of about 9 nm are distributed on the surfaces of TNTs evenly and attached strongly. The photocatalytic activities of the ZnO–TNTs nanocomposite are superior to those of P25, ZnO, TNTs and ZnO–anatase TiO 2 (TNP) nanocomposite in the oxidation of rhodamine B under UV light irradiation. A comparison of the photocatalytic activities between different catalysts is discussed. Furthermore, we also find that the ZnO–TNT nanocomposite shows very favorable recycle use potential, because they have a high sedimentation rate and their photocatalytic activity is only slightly decreased even after five times of repeated uses.