Particle Size Of ZnO Research Articles

Effect of Particles Size on Dielectric Properties of Nano-ZnO/LDPE Composites.

The melt blending was used to prepare 3 wt% ZnO/low density polyethylene (ZnO/LDPE) nanocomposites in this article. The effect of different inorganic ZnO particles doping on the dielectrical property and crystal habit of LDPE matrix was explored. The nanoparticles size was 9 nm, 30 nm, 100 nm, and 200 nm respectively. Scanning electron microscope (SEM) was used to characterize ZnO nanoparticles whereas differential scanning calorimetry (DSC) was used to make thermal characterization of the samples. Besides, the AC (alternating current), DC (direct current breakdown characteristics and electrical conductivity of the nanocomposites was studied in this article. The experimental results showed that nano-ZnO/LDPE composites had the advantages such as small crystal size, high crystallization rate and crystallinity owing to nano-ZnO particles doping, when doping nano-ZnO particles size was 30 nm, the ZnO/LDPE nanocomposite crystallinity crest value 39.77% appeared. At the mean time, the DC and AC breakdown field strength values of composites were 138.0 kV/mm and 340.4 kV/mm respectively. They were the maximal values which improved 8.24% and 13.85% than LDPE. The AC breakdown field strength of samples decreased with specimen thickness increase. The DC breakdown field strength of LDPE and ZnO/LDPE composites were greater than AC breakdown field strength. From the conductivity experimental result it could be seen that when the experimental temperature and electric field intensity rose, the current density and conductivity of ZnO/LDPE composites increased with the enlargement of ZnO particles size. But the values were less than which of LDPE.

Solvent-free synthesis of ZnO-graphene nanocomposite with superior photocatalytic activity

ZnO-graphene nanocomposites have potential applications in sensors, photocatalysis, solar cells, and energy storage. Currently, graphene-ZnO nanocomposites are prepared via multistep solution-based methods that suffer from low productivity and generation of large quantities of liquid waste. In this article, we report a new solventless process for the synthesis of ZnO-graphene nanocomposites contain 9 nm ZnO nanoparticles uniformly dispersed on the surface of thermally reduced graphene (TRG) via short-time ball milling of hydrozincite and graphite oxide (GO) followed by thermal annealing. Characterization of the structure and morphology of the graphene-ZnO nanocomposite as examined by XRD, FTIR, XPS, SEM, TEM, BET, and TGA revealed the ball milled nanocomposite has higher surface area and smaller ZnO particle size compared to the nanocomposite prepared by the solution-based hydrothermal method. Moreover, the photocatalytic activity of the ball-milling composite for degradation of methylene blue (MB) dye under visible light illumination are superior not only to TRG, ZnO, and hydrothermal ZnO-graphene nanocomposite but also to other reported ZnO and ZnO-graphene nanocomposite. Our results clearly demonstrate this mechanothermal process provides a facile, green, and scalable route for development of high-performance metal oxide-graphene nanocomposites.

Structural and electrical properties of ferroelectric poly(vinylidene fluoride) and mechanically activated ZnO nanoparticle composite films

The influence of the mechanical activation of ZnO nanoparticle fillers on the structural and electrical properties of the matrix of poly(vinylidenefluoride)–ZnO (PVDF–ZnO) films was investigated. Transmission electron microscopy and scanning electron microscopy analyses showed that mechanical activation in a high energy planetary ball mill reduces the size of ZnO particles. X-ray diffraction and Raman spectroscopy revealed that PVDF crystallized predominantly as the γ-phase. Non-activated ZnO filler reduces the degree of the crystallinity of the matrix and promotes crystallization of α-phase of PVDF in the film, while the fillers activated for 5 and 10 min induce crystallization of β-phase, indicating that mechanical activation of the filler can be used as a general method for fabrication of PVDF composites with increased content of piezoelectric β-phase crystals. Dielectric spectroscopy measurements show that polymer composite with the high content of β-phase (with ZnO filler activated for 5 min) exhibits the highest value of dielectric permittivity in 150–400 K range of temperatures. Kinetic analysis shows combined effects of increased surface area and increased concentration of surface defects on the interactions between polymer chains and activated nanoparticles.

Psidium guajava leaf extract-mediated synthesis of ZnO nanoparticles under different processing parameters for hydrophobic and antibacterial finishing over cotton fabrics

In recent times, treatment of natural fibres, like cotton, with antimicrobial finishing using nanoparticles has become increasingly high due to the possibility of anticipated property and their tuneable nature. In this study, using the phytoconstituents of leaf extract of Psidium guajava, Zinc acetate was reduced to obtain ZnO nanoparticles using three different synthesis routes namely sonication, wet-chemical and hydrothermal methods. To evaluate and get a broader understanding about the influence of processing parameter over the ZnO nanoparticles, physico-chemical, biological and photocatalytic property, a comparative assessment was performed. The ZnO nanoparticles were subjected to X-ray diffraction, particle size analysis and scanning electron microscope to ascertain its structure/morphology. The comparative studies reveal that hydrothermal method of ZnO synthesis yields smaller particle size (12 nm), with higher photocatalytic activity (94%), higher antibacterial activity against Escherichia coli (27.4 mm) and Staphylococcus aureus (29.3 mm) and lower structural defects comparing to ZnO synthesised via other methods of synthesis. Furthermore, the most effective ZnO nanoparticles (hydothermal method) was incorporated in chitosan and coated over the cotton fabric to functionalise cotton fabrics for better antimicrobial and water repellent property. Along with the same line, the ZnO nanocomposite coated fabrics exhibit better hydrophobic (157 ± 0.1°) (superhydrophobicity) and higher antibacterial activity (30.58 ± 0.3 mm (99%) (S. aureus) and 24 ± 0.5 mm (96%) (E. coli)), which could be attributed to ZnO particle size and favourable structural morphology. Thus, the study not only reveals the tuneable nature of the ZnO nanoparticles with respect to processing parameters and also shows the potential role in coating these nanoparticles over the cotton fabrics to impart an effective antimicrobial and hydrophobic finishing for biomedical applications.

Homogeneous distribution of nanosized ZnO in montmorillonite clay sheets for the photocatalytic enhancement in degradation of Rhodamine B

Nanosized ZnO intercalated in montmorillonite (ZnO-MMT) was successfully prepared by two-step preparation: ion exchange and thermal treatment. It was found that the structure of the obtained composite was arranged in the house-of-cards structure with the homogeneous distribution of nanosized ZnO in the clay sheets, according to the XRD, SEM–EDX, TEM, XAS analyses. Importantly, as-obtained ZnO-MMT showed the small domains of crystalline ZnO with less particle aggregation. The particle size of ZnO defined by TEM was in the range of 1.8–3.0 nm. In addition, XAS results suggested the presence of short-range structural order in wurtzite ZnO crystalline. The photocatalytic activity of ZnO-MMT over Rhodamine B solution was remarkably enhanced with the normalized quantity of 8.4 mmol g−1 compared with a physical mixture of ZnO and montmorillonite (ZnO@MMT) (1.8 mmol g−1) and commercial ZnO (1.1 mmol g−1). This photocatalytic enhancement was attributed to the strong synergistic interaction of nanosized ZnO that was homogeneously embedded in the montmorillonite structure.

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

AbstractCompounds of undoped and samarium (Sm) doped ZnO have been prepared by standard solid‐state reaction method. X‐ray diffraction (XRD), Williamson‐Hall (W‐H) analysis, Transmission Electron Microscopy (TEM), temperature‐dependent electrical and dielectric studies have been done to characterize these materials. Inclusion of Sm as dopant in hexagonal wurtzite ZnO changes the lattice parameters to a small extent with some Sm aggregation at higher concentration. Also, the mean particle sizes of ZnO:Sm compounds showed an inter‐correlation with the Scherrer method, W‐H analysis as well as with TEM results. The electrical resistivity depicts an exponential decay and metal‐semiconductor transition (MST) at ~300 K for the pristine sample whereas there is large decrement in the resistivity with Sm doping. The analysis of σac of ZnO suggests that the power law is obeyed and indicated an increase in the ac conductivity with Sm content. The mechanism behind this type of conductivity is elucidated by small polaron tunneling (SPT) model of conductivity. The dependence of ln dc on the temperature inverse shows that the traps of electrons are thermally activated such that low and high temperature activation energies confirm the presence of vacancies and interstitials of both O and Zn ions. Thus, a high value of dielectric constant makes these materials suitable for high frequency and charge storage device applications.

Study of Undoped and Indium Doped ZnO Thin Films Deposited by Sol Gel Method

In this paper, we report the effects of Indium doping concentrations (from 0 to 10wt%) on the structural, morphological, and optical properties of deposited In doped ZnO (IZO) thin films prepared by the sol–gel method through the dip coating technique. X-ray diffraction (XRD) analysis indicates that all ZnO thin films have a polycrystalline nature with a hexagonal wurtzite phase with (002) as a preferential orientation. XRD results demonstrate that the particle size of ZnO decreased with the increase in Indium concentrations. Raman scattering spectra confirmed the wurtzite phase and the presence of intrinsic defects in our samples. Energy dispersive spectroscopy (EDS) and the X-ray photoelectron spectroscopy (XPS) measurements, confirmed the presence of zinc, oxygen and indium elements which is in agreement with XPS results. The photoluminescence (PL) spectra of the films exhibit defects-related visible emission peaks, with intensities differing owing to different concentrations of zinc vacancies. UV–Vis spectrometer measurements show that all the films are highly transparent in the visible wavelength region (≥ 70%) and presented two different absorption edges at about 3.21 eV and 3.7 eV, these may be correspond to the band gap of zinc oxide and indium oxide respectively.

Biosynthesised ZnO : Dy3+ nanoparticles: Biodiesel properties and reusable catalyst for N-formylation of aromatic amines with formic acid

ZnO nanoparticles doped with trivalent dysprosium ions (Dy3+) were prepared through the green combustion technique using E. tirucalli plant latex as a fuel. The fundamental and optical properties of the samples are examined via the X-ray diffraction, FTIR, UV-visible analytical methods and morphology by scanning electron microscope and transmission electron microscope. Rietveld refinement results show that the ZnO : Dy3+ were crystallized in the wurtzite hexagonal structure with space group P63mc (No. 186). The average particle size of ZnO : Dy3+ prepared with the different concentration of latex was found to be in the range 30-38nm, which is also confirmed by TEM analysis. A rapid and convenient method for the one-pot preparation of N-formamide derivatives aromatic amines and amino acid esters has been developed using Dy3+ doped ZnO as a catalytic agent. This method provides an efficient and much improved modification over reported protocols regarding yield, clean and work-up procedure milder reaction conditions. In this work, Pongamiapinnata oil was recycled for the preparation of biodiesel via Dy3+ doped ZnO as a catalytic agent.

Improvement of Mechanical and Dielectric Properties of Epoxy Resin Using CNTs/ZnO Nanocomposite.

In this study, carbon nanotubes (CNTs)/ZnO composites had been prepared using the sol-gel method and then incorporated into an epoxy resin for reinforcement of mechanical and electrical properties. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD) Field Emission Scanning Electron Microscope (FE-SEM) analyses show that the ZnO nanoparticles deposited on CNTs were crystallized in a hexagonal wurtzite structure. Average particle size of ZnO deposited on the CNT was about 8 nm. The mechanical and dielectric properties of epoxy containing CNTs/ZnO were investigated in comparison to epoxy resin and epoxy resin containing only CNT or ZnO nanoparticles. The results indicated that tensile strength and elongation at break of the nanocomposite were substantially improved with the presence of CNTs/ZnO at the equal volume. The DSC analysis associate with the dielectric results shows that the behavior of epoxy/CNTs/ZnO is identical to epoxy/ZnO composite, and the CNTs is essential to the distributed arrangement of ZnO in the epoxy resin.

Dietary transfer of zinc oxide particles from algae (Scenedesmus obliquus) to daphnia (Ceriodaphnia dubia)

The rapid increase in production and usage of ZnO particles in recent years has instigated the concerns regarding their plausible effects on the environment. Current study explores the trophic transfer potential of ZnO particles of different sizes (50, 100 nm and bulk particles) from algae (Scenedesmus obliquus) to daphnia (Ceriodaphnia dubia) and the contribution of ZnO(ions) (effect of dissolved Zn ions that remain in test medium after separation NPs) to the overall toxicity of ZnO(total) (impact of both particle and dissolved Zn ions). Toxicity and uptake of ZnO(total) and ZnO(ions) in algae were found to be dependent on the concentration and particle size. Feeding of Zn accumulated algae (517 ± 28, 354.7 ± 61 and 291 ± 20 µg/g dry wt.) post-exposure to 61 µM of ZnO(total) of 50, 100 nm and bulk ZnO particles caused a significant decrease in the survival (15–20%) of daphnia. A significant amount of Zn accumulation was observed in daphnia even after the 48 h depuration period. Biomagnification factor was found to be nearly 1 for all the sizes of ZnO particles tested. For 50 nm ZnO, the BMF was higher when compared to other two sizes, reaching the mean value of 1.06 ± 0.01 at 61 µM. Further analysis revealed that the dietary uptake of different sizes of ZnO particles caused ultra-structural damages and degradation of internal organs in daphnia.

Quantum dot light emitting diodes using size-controlled ZnO NPs

The particle size and trap energy level of ZnO were adjusted by varying the concentration of precursors using a sol–gel process, and the energy transport properties of the electron transport layer in quantum dot light-emitting diodes (QD-LEDs) were analyzed. Thus far, no study has considered the efficient electron transport properties of quantum dot light-emitting devices with respect to trap energy levels owing to the oxygen vacancies of ZnO. The particle size and trap energy levels of ZnO were analyzed based on optical properties such as photoluminescence and absorbance. The optimized device showed excellent performance, with a maximum luminance of 50,120 cd/m2, a high efficiency of 5.85 cd/A, and a threshold voltage of 2.5 V. The Y-ZnO (yellow photoluminescence ZnO)-based QD-LEDs not only enhanced the injection efficiency of electrons into the emitting layer but also confined the holes in the emitting layer due to the shallow trap level of Y-ZnO, in contrast to the deep trap levels of G-ZnO (green photoluminescence ZnO) and B-ZnO (blue photoluminescence ZnO). Here, we present the first attempt to analyze the electron transport behavior of the electron transport layer of the resulting device.

Synthesis and Characterization of Catalysts Cu–ZnO Supported on Mesoporous Carbon FDU‐15

A new catalyst with uniformly distributed metal oxide is synthesized and characterized. The active centers Cu–ZnO of the designed catalyst are well distributed in the ordered mesoporous carbon FDU‐15 which has very high BET surface area and large pore volume. The effects of the amount of metal oxide loading, calcination temperature, and ramping rate on the resulting catalysts are investigated using N2‐physisorption, X‐ray diffraction, and scanning and electron microscopy. The results show that the Cu–ZnO particle size increases with the metal loading and calcination temperature, whereas it decreases with the ramping rate. When the metal loading is 20%, the calcination temperature is 700 °C, and the ramping rate is 20 °C/min, uniform metal oxide particles well distributed on the carbon support are obtained.

Magnetic properties and photovoltaic applications of ZnO:Mn nanocrystals

A simple and large-scale synthetic method of Mn doped ZnO (ZnO:Mn) was developed in this work. ZnO:Mn nanocrystals with hexagonal structure were prepared by thermal decomposition of zinc acetate and manganese acetate in the presence of oleylamine and oleic acid with different temperatures, ligand ratios, and Mn doping concentrations. The particle size (47–375 nm) and morphology (hexagonal nanopyramid, hexagonal nanodisk and irregular nanospheres) of ZnO:Mn nanocrystals can be controlled by the ratio of capping ligand, reaction temperature, reaction time and Mn doping concentration. The corresponding optical and magnetic properties were systemically studied and compared. All samples were found to be paramagnetic with antiferromagnetic (AFM) exchange interactions between the Mn moments in the ZnO lattice, which can be affected by the reaction conditions. The quantum dot sensitized solar cells (QDSSCs) were fabricated based on ZnO:Mn nanocrystals and CdS quantum dots, and the device performance affected by Mn doping concentration was also studied and compared.

PREPARATION AND CHARACTERIZATION OF ZnO NANOPARTICLES BY SOLVENT FREE METHOD

ZnO nanoparticles have numerous applications as photo catalysts, gas sensors, UV lasers, as optoelectronic and microelectronic devices or in cosmetic field. ZnO nanoparticles were synthesized by solvent free method using zinc nitrate hexahydrate as precursor and glycerol as dispersant, without solvent present. This method proved to be very simple, economic and ecofriendly. Zinc nitrate and glycerol were mixed in different ratio in order to avoid and overcome a possibility of agglomeration. Characterization of samples was performed by UV/VIS and FTIR spectrophotometry. The strongest absorption appeared at wavelength 206 nm. Using combination of UV/VIS spectrophotometry and hyperbolic band model (HBM) particles size of ZnO particles were evaluated to 2.06 nm. Additionally, using Tauc plot, a band gap energy was determined. Band gap energy of ZnO nanoparticles amounted to 5.00 eV. IR spectrum showed existence of ZnO in interval 600- 400 cm-1.

Effect of ZnO particle sizes on thermal aging behavior of natural rubber vulcanizates

The effects of ZnO particle size on crosslinking and thermal aging behavior of natural rubber (NR) were investigated. NR vulcanizates filled with nano ZnO allowed higher crosslink density, lower polysulfide crosslink, and stronger mechanical properties than those filled with micro ZnO. After thermal aging, NR filled with nano ZnO exhibited much more stable chemical and mechanical properties. The high crosslink density as well as the formation of more stable mono- and di-sulfidic crosslinks was attributed to the good dispersion and high surface area of the nano ZnO.

Molecular aspects of core-shell intrinsic defect induced enhanced antibacterial activity of ZnO nanocrystals.

To investigate molecular aspects of the antibacterial effect of size-dependent core-shell intrinsic defects of nanocrystalline ZnO synthesized through high energy ball milling technique. Mechanically synthesized and characterized 7, 10 and 15h milled ZnO nanoparticles were evaluated for antibacterial activity with molecular investigation by computational molecular docking. Synthesized ZnO nanoparticles displayed shrinkage of core and increase of shell with reduction in size of bulk ZnO particles from 250 to 80, 40 and 20nm and increase in zeta potential up to -19mV in 7, 10 and 15h nano ZnO. Antibacterial activity was found increased with decrease in size due to increased reactive oxygen species and membrane damage in bacteria. Synthesized nano ZnO exhibit size-dependent antibacterial action as consequences of interactions with cell membrane proteins via hydrogen bond interaction with amino acid residues followed by internalization, membrane depolarization and induction of reactive oxygen species generation.

Effect of bovine serum albumin immobilized Au–ZnO–graphene nanocomposite on human ovarian cancer cell

Present work reports for the first time on successful in-situ synthesis of Au incorporated ZnO–graphene nanocomposites (AZG) by one pot surfactant free low temperature (∼95 °C) solution process. Zinc acetate dihydrate and graphene oxide with varying content of chloroauric acid (5 mM, 10 mM and 50 mM) were used as the precursor materials. The immobilization of bovine serum albumin (BSA) with a particular AZG2 nanocomposite (derived from the precursor medium with 10 mM chloroauric acid) was also made separately. X-ray diffraction, field emission scanning and transmission electron microscopic analyses confirmed the presence ZnO and Au nanoparticles (NPs), distributed uniformly in CCG matrix of the sample. The average particle size of ZnO and Au nanoparticle were ∼11.3 nm and 30–60 nm, respectively as obtained from TEM images of AZG2 nanocomposite. FTIR, Raman, UV–visible and X-ray photoelectron spectroscopic characterizations also were carried out to confirm the existence of chemical interaction/complexation that happened between the available oxygen functional groups of CCG with the inorganic moieties (ZnO/Zn2+ and Au NPs) of AZG nanocomposites. An existence of interaction between BSA and AZG2 nanocomposite was confirmed by UV–Visible and photoluminescence spectral analyses. Initially, the in vitro cytotoxicity and quantitative cell viability (CV) of human ovarian teratocarcinoma cell line, PA1 was investigated to a maximum concentration of 200 μg/ml for ZO, ZG, AZG1, AZG2 and AZG3 sample. The CV was again repeated on BSA-AZG2 nanocomposite (as AZG2 shows maximum cell viability) and a maximum CV of the cancer cells was found (∼92% of the viable cells at 50 μg/ml dose). This work could have fundamental importance in biomedical applications.

Immobilization of ZnO nanoparticles on fluorinated perlite granules for the photocatalytic degradation of methylene blue

The fluorination of perlite granules and the immobilization of ZnO nanoparticles on the perlite surface were carried out at the same time by a simple impregnation method to create new highly photocatalytic materials which are easily separated from reaction solutions after treatment. The influence of perlite fluorination on the crystal structure, morphology, UV-visible absorption, and surface functional groups of ZnO, as well as on the ZnO content on perlite, was respectively characterized by XRD, FE-SEM, UV-Visible diffuse reflectance, FTIR and atomic absorption spectrometry. The photocatalytic activity was evaluated via the extent of degradation of methylene blue under UVA irradiation. According to the results, the fluorination of perlite leads to numerous effects on ZnO, such as the decline of ZnO cell parameters, the increase of ZnO content on perlite granules (resulting in the enhancement of light absorption in UVA range), and the decrease of ZnO particle size, which can effectively improve its photocatalytic performance. The photocatalysts were also found to be able to stay afloat on water, allowing for easy separation from the reaction solution.

Zinc Oxide/TiO2 Bilayer Heterojunction as a Working Electrode in Quasi Solid Dye Sensitized Solar Cells

Bilayer heterojunction of aluminium doped zinc oxide (AZO) and titanium dioxide (TiO2) mesoporous has been successfully deposited on fluorine tin oxide (FTO) substrate as working electrode in dye sensitized solar cell. This layer was used as working electrode in quasi solid dye sensitized solar cell. The solar cell structure is FTO/ZnO/TiO2/PGE/Pt/FTO using polymer gel electrolyte (PGE). In polymer gel electrolyte system, hybrid copolymer based on poly-TMSPMA (3-methoxysilyl propyl methacrylate) was used as a matrix to trap ionic liquid. An addition of aluminum as atom dopant also studied to observe the physical properties changes of photoanode related to solar cell performance. AlCl3 was used as dopant material with the concentrations at 0.5 weight % and 1.0 weight% of zinc acetate dehydrate as raw material. Based on our previous result, the existence of Al dopant would decrease the surface roughness of ZnO layer, reduce the grain size of ZnO particles, transmittance at visible light increase and also change the charge carrier density. Nevertheless, the highest efficiency was achieved for undoped ZnO/TiO2 photoanode (η=0.67%). Based on current-voltage measurement data analysis (using diode model equation) the ideality factor (n) of device using undoped ZnO was smaller (n=2.96) than AZO 0.5 wt% and 1.0 wt% (n=∼4), indicate better quality of undoped ZnO/TiO2 interfaces rather than AZO/TiO2.

Photocatalytic degradation of pefloxacin in water by modified nano-zinc oxide

Nanocrystalline La-doped ZnO powders were synthesized by homogeneous precipitation method and characterized by various sophisticated techniques such as XRD, UV–vis DRS and SEM. Experimental results show that the La-doped ZnO could make ZnO particle size decrease and make specific surface area large, so the photocatalytic activity of La-doped ZnO was increased compared with pure ZnO. The optimal conditions for maximum efficiency of pefloxacin degradation under 6h UV irradiation were found as 1g/L dosage of La-doped ZnO nanocomposite, pefloxacin concentration of 15mg/L, and pH = 7.0. Under optimal operating conditions, degradation efficiency was reached to 93%.