Dispersion Of ZnO Nanoparticles Research Articles

Effect of pH and surfactants on the electrokinetic properties of nanoparticles dispersions and their application to the PET fibres modification

This paper presents the effect of surfactants, pH and electrolyte (0.1 × 10−3 M KCl) on the stability of the aqueous dispersions of commercial ZnO and AgCu nanoparticles. As the surfactants cationic hexadecyltrimethylammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS), and nonionic 4-(1,1,3,3-tetramethylbutyl)phenyl polyethylene glycol (Triton X-100) at concentrations of 0.5 × 10−3, 1.0 × 10−3, and 0.1 × 10−3 M, respectively, were used. The zeta potential values, z-average hydrodynamic diameter and long-term stability of ZnO and AgCu nanoparticles were examined by means of the dynamic light scattering (DLS) technique. It was found that the presence of ionic surfactants reduced the tendency of nanoparticles for agglomeration/aggregation and improved their colloidal stability. They were characterized by high (>|70| mV) and pH-independent zeta potential values. In addition, ZnO nanoparticles in the presence of ionic surfactants showed a better long-term stability than AgCu nanoparticles. Their z-average hydrodynamic diameters in CTAB and SDS were 195 ± 2 nm and 295 ± 5 nm, respectively, and remained almost unchanged for 5 days. The addition of KCl improved the stability of aqueous and containing nonionic surfactant dispersions of nanoparticles, what was reflected in the zeta potential values > 30 mV in almost the entire pH range. The stability of nanoparticles dispersion significantly affects the uniformity of nanoparticles distribution on the fibres surface. The uniformity of distribution of the ZnO and AgCu dispersion on the surface of polyester (PET) fibres was carried out by means of microscopic methods (SEM/EDS).

Monodispersed ZnO Nanoparticle-Poly(methyl methacrylate) Composites with Visible Transparency for Ultraviolet Shielding Applications

The inorganic–organic nanomaterials with high visible light transmittance have shown great potential in applications. However, it is difficult to disperse nanoparticles uniformly in organic matrices, resulting in an obvious decrease in transparency. This article reports a method to prepare ZnO-poly(methyl methacrylate) (ZnO-PMMA) nanocomposites with high transparency and excellent properties. First, a highly transparent nanodispersion of ZnO in methyl methacrylate (MMA) monomer is synthesized by the high-gravity reactive precipitation method. Then, ZnO-PMMA nanocomposites are prepared by the in situ bulk polymerization method. ZnO nanoparticles are about 6 nm with narrow size distribution, which monodisperse in MMA with the surface modifier containing C═C double bonds, contributing to the uniform dispersion of ZnO nanoparticles in PMMA matrices. Therefore, it ensures that the prepared ZnO-PMMA nanocomposites keep a high visible transmittance without any Rayleigh scatter. Moreover, ZnO-PMMA nanocomposites achieve multiple function applications of UV-shielding and anti-photo-aging, due to good thermal stability and high toughness and stiffness, which is attributed to the good dispersion of ZnO nanoparticles. After 200 h of UV radiation, pure PMMA obviously turns yellow and has a remarkable decrease in mechanical properties, whereas the nanocomposite is colorless and still keeps high visible transmittance and mechanical performances, which has great potential applications in the fields of optical materials and equipment.

Development of polylactic acid/ZnO composite membranes prepared by ultrasonication and electrospinning for food packaging

In this study, biopolymer-based antimicrobial fibrous membranes constituted by polylactic acid (PLA) and ultrasonically dispersed ZnO nanoparticles (NPs) were developed by electrospinning. The morphology, mechanical properties, thermodynamics and antimicrobial properties of membranes with different ZnO NPs content were comprehensively studied. The results showed that the best performance was achieved when the content of ZnO content was 0.5 wt% (PLA/ZnO-0.5%). Specifically, the tensile strength and elongation at break of the composite membrane were 6.85 ± 0.19 MPa and 74.90 ± 0.59%, respectively, and the inhibition zones of Escherichia coli and Staphylococcus aureus were 15.02 ± 0.18 mm and 14.74 ± 0.06 mm, respectively. In addition, an appropriate ultrasonication time of 45 min improved the thermal, ultraviolet (UV) barrier, and antibacterial properties of the composite membrane. At the 45 min ultrasonication time, the inhibition zone of PLA/ZnO-0.5% against Escherichia coli and Staphylococcus aureus was 18.11 ± 0.15 mm and 15.80 ± 0.11 mm, respectively. Therefore, PLA/ZnO-0.5% can be applied in food packaging to provide an antibacterial effect and UV light barrier.

Corrosion Inhibition Properties of Epoxy-Zinc Oxide Nanocomposite Coating on Stainless Steel 316L

Metal corrosion generally refers to metal deterioration process that is caused by electrochemical reactions between the metallic substrate with corrosive environment. Marine grade stainless steel type 316L (SS 316L) is a premium material for marine applications. Prolonged exposure to chloride-containing environments increases the susceptibility of unprotected SS 316L to localized corrosion namely pitting and crevice corrosion. In this study, the potential protective coating comprising of the epoxy matrix with ZnO nanoparticles combination was formulated and its anticorrosive properties on SS 316L substrate were analyzed. Variation in corrosion behaviour of SS 316L coated with a series of epoxy coating solution containing 1, 3, 5, 7 and 10 wt % ZnO nanoparticles were thoroughly observed. The coating formulations were characterised by using X-ray Diffraction (XRD) spectroscopy and Scanning Electron Microscope (SEM). Meanwhile, the corrosion performance testing was measured by using Potentiodynamic Polarization (PP) technique. The results revealed that epoxy coating incorporated with 3 wt % of ZnO nanoparticles provided the best corrosion protection on SS 316L as the corrosion rate for the metal substrate has been minimized from 0.05268 mm/year to as low as 0.00047 mm/year after coating. Dispersion of ZnO nanoparticles in epoxy matrix increases the barrier properties of the coating and impeded corrosion process on SS 316L through suppression of anodic reaction.

Optimal utilization of ZnO nanoparticles blended diesel-water emulsion by varying compression ratio of a VCR diesel engine

The experimental study is performed to understand the effect of the ZnO nanoparticles blended diesel-water emulsion on the performance and emission characteristics of a VCR diesel engine at various compression ratios. The test fuels used for the investigation were neat diesel, diesel-water emulsion and ZnO nanoparticles incorporated diesel-water emulsion. The diesel-water emulsion consists of 88% neat diesel, 10% of distilled water and 2% surfactants. The dispersion of ZnO nanoparticles into the diesel-water emulsion varies by 50 ppm and 100 ppm with the help of ultrasonic agitation. During the investigation, the CR increased from 16.5 to 18.5 with one step, and load on the engine increased from 0% to 100% in the steps of 25. The test results showed a greater improvement in BTE and BSFC for ZnO nanoparticles blended test fuels compared to other test blends by increasing the CR of the engine. The emissions of CO, HC were reduced significantly whereas CO2 emissions were increased for ZnO nanoparticles blended test fuels with an increase in the CR. It is also observed that NOx emissions increase with increasing the CR, even though at all CR’s ZnO nanoparticles blended test fuel show lower NOx levels than other test blends. Based on the test the optimal results are observed at CR 18.5 for DW10Z100 blend.

Three-Dimensional Graphene Oxide-Supported Zinc Oxide Scaffold as a High-Efficiency Adsorbent for Desulfurization

Sulfur oxides are air pollutants derived mainly from the combustion of gasoline. Reducing the sulfur content of fluid catalytic cracking (FCC) gasoline is of key importance for the prevention and control of atmospheric pollution. We describe herein the fabrication and characterization of a porous, three-dimensional (3D) graphene oxide-supported zinc oxide (GO/ZnO) scaffold as an adsorbent for desulfurization with various model compounds and real FCC gasoline. The uniform and stable dispersion of ZnO nanoparticles on the surface of GO facilitates the specific binding of sulfides. Moreover, GO synergistically adsorbs aryl sulfides via [Formula: see text]–[Formula: see text] stacking interactions. The GO/ZnO nanosheets were further self-assembled into a 3D porous scaffold that effectively trapped sulfides and inhibited desorption. These scaffolds exhibited excellent desulfurization performance with maximum sulfur capacity up to 29.73[Formula: see text]mg S/g. This work provides a novel perspective on the fabrication of high-efficiency adsorbents for gasoline pretreatment.

ZnO nanodispersion as pseudohomogeneous catalyst for alcoholysis of polyethylene terephthalate

Chemical depolymerization and recycling of polyethylene terephthalate (PET) is a sustainable way to preserve the resources and protect the environment. In this work, methanol and ethylene glycol dispersions of ultrasmall ZnO nanoparticles are firstly adopted as pseudohomogeneous catalysts for alcoholysis of PET. The as-prepared ZnO nanoparticles have a uniform size of 4 nm and can be stable in dispersions for 6 months. In the methanolysis process of PET, the effects of various parameters on the conversion of PET and the yield of dimethyl terephthalate (DMT) were investigated. The results show that higher temperature (170 °C) was beneficial to the conversion of PET and the yield of DMT, which can reach about 97% and 95% after 15 min, respectively. The excellent activity of 553 g PET h−1 (g ZnO)−1 was achieved. Furthermore, the methanolysis of PET have shorter reaction time (1/4) and higher activity (4.7 times) than the glycolysis of PET.

DC surface flashover characteristics of ZnO/Epoxy composites at room temperature and 77 K

Epoxy (EP) resin based nano-composites are widely used in high voltage direct current (HVDC) high temperature superconducting (HTS) power cable. In this paper, the DC surface flashover characteristics of ZnO/EP composites were studied at both room temperature and 77 K. The samples were made by dispersing ZnO nano-particles into EP resin with various weight percentages of 0%, 1%, 3%, 6% and 10%, respectively. The experiments were carried out with a cryogenic system in which DC high voltages ranging from 0 kV to 100 kV were supplied. The results showed that the surface flashover voltages increased with the increase of ZnO content at both room temperature and 77 K, and the surface flashover voltages at 77 K were higher than that at room temperature for composites with the same ZnO content.

One-pot sonochemical synthesis route for the synthesis of ZnO@TiO2/DW hybrid/composite nanofluid for enhancement of heat transfer in a square heat exchanger

The thermophysical properties of ZnO@TiO2/DW composite nanofluids with (0.1, 0.075, 0.05 and 0.025)mass% concentrations have been experimentally studied. The equal and homogenous dispersion of both ZnO and TiO2 nanoparticles with 50:50 ratio each in distilled water (DW) was attained by the sonochemical method. The efforts are directed to examine the effective thermal conductivity of the different mass% concentrations of ZnO@TiO2/DW composite nanofluid for a selected range of temperatures at 20 to 45 °C. The maximum improvement in thermal conductivity for ZnO@TiO2/DW composite nanofluid was noticed for 0.1 mass% concentration, and the maximum enhancement was spotted 47% higher than the base fluid (DW). The heat transfer properties of ZnO@TiO2/DW composite nanofluids with (0.1, 0.075, 0.05 and 0.025) mass% concentrations and base fluid (DW) in a square heat exchanger were also investigated. Average and local heat transfer values and growth in Nusselt values were conquered for different velocities and corresponding to specific Reynolds numbers range from 4550 to 20,360. The maximum improvement increases about 57% in average heat transfer (h) and Nusselt numbers correspondingly, while local heat transfer for 0.1 mass% is about 500 to 1750 W m−2 K, for 0.075 mass% is 500 to 1500 W m−2 K, for 0.05 mass% is 500 to 1370 and for 0.025 mass% is 500 to 1150 of the composite nanofluid which is greater than base fluid (DW). The ZnO and TiO2 mixture gives the best combination to enhance the overall heat transfer coefficient (h).

Sensing of Oxygen Partial Pressure in Air with ZnO Nanoparticles.

The demand for sensors in response to oxygen partial pressure in air is increasingly high in recent years and small-size sensors on a micrometer scale and even a nanometer scale are particularly desirable. In this paper, the sensing of oxygen partial pressure in air was realized by a solution-processed ZnO nanoparticle (NP). Thin-film ZnO NP was prepared by spin-coating and a highly sensitive sensor was then fabricated. The oxygen sensing performance was characterized in air and compared with that in nitrogen, which showed an increase in electrical conductance by more than 100 times as a result of decreasing oxygen partial pressure from 103 mBar to 10−5 mBar. Moreover, higher sensitivity was achieved by increasing the annealing temperature and the effect of thermal annealing was also investigated. Furthermore, ZnO NP lines with 7 μm in width were successfully patterned with low cost by a mould-guided drying technique from ZnO NP dispersion, which makes ZnO NP extremely promising for miniaturized and integrated sensing applications.

Dispersion of Zinc Oxide Nanoparticles in Maxillofacial Silicone Elastomer by Ultrasonication: A Morphological Study

Objective: Aggregation and agglomeration of nanoparticles in silicone elastomer is a common problem that adversely affects the mechanical properties of the silicone because the aggregations act as a weak and stress concentrating point within the silicone elastomer matrix. The objective of this study was to evaluate the effect of sonication on the dispersion of ZnO nanoparticles in M-511 heat vulcanized maxillofacial silicone. 
 Methods: Nano-ZnO was added in concentrations of 1%, 2%, 3%, and 5% by weight to Cosmesil M-511 heat vulcanized maxillofacial silicone elastomer, after sonication of ZnO nanoparticles in ethanol for 30 minutes at room temperature, and 1%, 2%, 3%, and 5% were added by weight without sonication of ZnO nanoparticles. Then field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) tests were used to assess the efficiency of the dispersion method and to monitor the particle size of nano-ZnO.
 Results: FESEM test showed a reduction in cluster size of nano-ZnO as a result of sonication. XRD and FESEM showed a homogenous dispersion of ZnO nanoparticles within the silicone matrix.
 Conclusions: Based on the results of this morphological study, sonication of nano-ZnO in ethanol represented an effective and easy way to disperse nano-ZnO in a silicone elastomer matrix. This led to a superior quality nanocomposite without affecting the base material and without the need for a coupling agent or addition of any third material.

Facile fabrication of ZIF-derived graphene-based 2D Zn/Co oxide hybrid for high-performance supercapacitors

Abstract Recently, rational design and synthesis of two-dimensional (2D) nanoflake based architectures have attracted great attention in energy storage systems due to their unique properties, such as high specific surface area, superior electrical and thermal conductivity. Zeolitic imidazolate frameworks (ZIFs) with 2D structure can be synthesized by a facile aqueous method and be used to obtain 2D metallic/binary metallic oxides. In this paper, graphene oxide and Zn2+ were added in the synthesis of Co-ZIF, and its derived oxide (ZnCoO-G) exhibits 2D nanosheet structure with well dispersed Co3O4 and ZnO nanoparticles after heat treatment. Compared with the derivatives without graphene oxide (ZnCoO) and Zn2+ (CoO-G), ZnCoO-G demonstrates the highest specific capacitance of 711.6 F g−1 at 1 A g−1 with a capacitance retention of 63.6% at 5 A g−1 after 1000 cycles. Also, an asymmetric supercapacitor (ASC) with ZnCoO-G and commercial active carbon as positive and negative electrodes has a maximum energy density of 18.7 W h kg−1 at a power density of 800 W kg−1.

ZnO Nanoparticles Coated with Amphiphilic Polyurethane for Transparent Polyurethane Nanocomposites with Enhanced Mechanical and UV-Shielding Performance

To optimize the dispersion and interfacial interaction of ZnO nanoparticles in UV-curing poly(urethane acrylate) (PUA) nanocomposites, a series of amphiphilic polyurethane (APU)-functionalized ZnO ...

Stabilization and Dispersion of ZnO Nanoparticles in PVA Matrix

In the present work ZnO nano particles have been synthesized and stabilized by polyvinyl alcohol, PVA, under in situ and ex situ condition and focused on the effect of reaction conditions on the stabilization and dispersion of ZnO nano particles in PVA. From particle size analysis it is evident that, the rate of agglomeration is slower for ex situ synthesis method. It was also observed that the peak has shifted towards lower diameter value of the nano particles. The synthesis of ZnO nano particle has further been established with UV–VIS peak at around 350 nm and morphology study by FESEM study. EDAX spectra exhibited that weight percent of ZnO NP formed is around 2.5%. Dynamic mechanical study and thermal study was also made with the samples. It has been observed that mechanical property under dynamic condition is better with ex situ samples and storage modulus is 1.7 times higher than the in situ sample. Thermal property of PVA has been improved with composite formation as the percent char has been increased in case of composites.

Nanorods Versus Nanoparticles: A Comparison Study of Au/ZnO-PMMA/Au Non-Volatile Memory Devices Showing the Importance of Nanostructure Geometry on Conduction Mechanisms and Switching Properties

Hybrid organic-inorganic devices offer a simple and low cost route to the fabrication of resistive memory devices. However the switching and conduction mechanisms are not well established. This work compares ZnO-based devices made in the same manner but having two different nanostructure geometries, vertically aligned ZnO nanorods and randomly dispersed ZnO nanoparticles, both embedded within a PMMA host material and sandwiched between two gold electrodes in a crossbar device configuration. Both device types do not require a forming step to initiate switching and exhibit bipolar switching at relatively low operating voltages. In the low field regime both device types exhibit Ohmic behavior, however in the high field regime their switching and conduction mechanisms are distinctly different. ZnO nanorod-based devices exhibit smooth I-V curves and smooth switching behavior and a conduction mechanism that changes from Poole-Frenkel to Schottky emission when switching from the ON state to the OFF state. In contrast, ZnO nanoparticle devices exhibit sharp switching properties with SCLC behavior in the OFF state and Ohmic conduction in the ON state. These differences in the conduction and switching properties of devices containing the same materials clearly demonstrates the importance of the nanostructure geometry and device architecture on the switching and conduction properties of memristor devices. For each device type we discuss the results and propose plausible mechanisms to account for their different behavior.

Nano-ZnO functionalized biochar as a superhydrophobic biosorbent for selective recovery of low-concentration Re(VII) from strong acidic solutions

A novel nano-ZnO functionalized biochar with superhydrophobic surface was successfully synthesized and tested for selective recovery of Re(VII) anions in strong acidic solutions. The as-synthesized biochar was characterized by XRD, XPS, FT-IR, EDX, TEM, STEM-HAADF, SAXS, N2 adsorption-desorption isotherm and water contact angle measurements. The characterization results revealed that the functionalized biochar was composed of highly dispersed ZnO nanoparticles bound to biochar matrix and displayed superhydrophobicity with water contact angle of about 151–156°. Because of the synergistic effect of surface superhydrophobicity and metal affinity, the new biochar exhibited excellent selectivity and high efficiency to Re(VII) in the presence of various competing ions. Adsorption mechanism exploration found that inner-sphere complexation on homogeneous surface would be the dominant interaction, while liquid film diffusion was considered as the rate-controlling step in the sorption process. Due to its excellent selectivity, high efficiency and easy synthesis process, the obtained superhydrophobic biosorbent is ideal candidate for Re(VII) recovery from copper smelting acidic wastewater.

Investigations for the optimal combination of zinc oxide nanoparticle-diesel fuel with optimal compression ratio for improving performance and reducing the emission features of variable compression ratio diesel engine

The continual hike in environmental pollution from diesel engines has raised the concern of researchers to identify certain clean fuels. For this purpose, experimental investigations are carried out to inspect the consequences of ZnO nanoparticles addition for performance and emissions features of a 4-stroke, single-cylinder diesel engine. ZnO nanoparticles were mixed with pure diesel in varying proportions ranging from 5 to 25 mg. The better dispersion of ZnO nanoparticles in diesel was attained by means of magnetic stirrer and ultrasonication process. The test fuels were experimented at varying engine loads of 2 kW, 4 kW, 6 kW, 8 kW, 10 kW and 12 kW at 1500 rpm engine speed. It was observed that among different test fuels, an enhancement in brake thermal efficiency was achieved by 15.58% and reduction of 11.11% in brake specific fuel consumption for 20ZnO60DF (20 mg ZNP + 20 mg CTAB surfactant + 600 ml diesel) at 12 kW engine load as compared with neat diesel. The toxic emissions of NOX, HC, CO, CO2 and particulate matter with the inclusion of 20ZnO60DF were significantly decreased by 57.46%, 78.78%, 58.93%, 41.85% and 42.51%, respectively, as correlated with pure diesel fuel at 12 kW condition with 18 compression ratio. The recommended optimal combination of ZnO nanoparticle-diesel with optimal compression ratio for better performance and reduced emissions level was found out to be 20ZnO60DF with compression ratio 18. So, it is concluded that ZnO nanoparticles addition to diesel could be accepted as a clean alternative fuel as it emits lesser emissions and acts as environmental-friendly fuel.

Uniform zeolitic imidazolate framework coating via in situ recoordination for efficient polysulfide trapping

The “shuttle effect” in lithium sulfur battery system is the most prominent challenge hampering its further development and application in the energy storage industry. Metal-organic framework (MOF) derived carbon materials are considered to be efficient sulfur hosts to confine the polysulfides because of the unique porous structure and the heteroatom doping. However, a strong acid wash step is usually needed to remove the metal or metal oxide residual after pyrolysis, which will produce a large amount of acidic waste solution and increase the complexity of the synthetic process. Herein, instead of being removed, the uniformly dispersed ZnO nanoparticles in the pyrolytic polyhedra from zeolitic imidazolate framework-8 (ZIF-8) is directly used as the metal source to prepare a new ZIF-8 coating layer. This novel structure possesses not only the unique inner porous structure and high conductivity of pyrolytic carbon, but also the extra protection from ZIF-8 layer with both physical confinement and chemisorption to polysulfides. The resulting cathode displays an initial capacity of 1410 mAh g−1 at 0.2 C, and desirable cycling stability and rate capability are also obtained.

Optical studies of n-octyloxy-cyanobiphenyl (8ocb) with dispersed ZnO nanoparticles for display device application

Liquid crystalline (LC) materials have the ability to transfer their long range orientation order in the dispersed materials such as nanoparticles and various colloids. ZnO nanoparticles have wide variety of applications and influence the birefringence properties of liquid crystalline molecules. The paper describes the systematic studies on liquid crystalline n-octyloxy-cyanobiphenyl (8ocb) compound with dispersed ZnO nanoparticles in different concentrations. The presence of ZnO nanoparticles in 8ocb are determined by optical, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies. The refractive indices and birefringence measurements are carried out at different wavelengths (460, 500, 570 and 635 nm) using wedge shaped cell with modified spectrometer. The birefringence (δn) increases from 14 to 35% with increasing weight concentration of ZnO nanoparticles in the nematic thermal range. This is due to strong Vander Waal’s interaction between LC molecules and ZnO nanoparticles which increases the alignment of the LC molecules. Further the order parameter S obtained from Kuczynski internal field model, Vuks model and Haller extrapolation methods are in good agreement. It is found that the order parameter S increases with increase in dispersion of concentration of ZnO nanoparticles from 11.2 to 23.9%. The prepared materials find potential applications in many optical devices.

Dissolution and Phosphate-Induced Transformation of ZnO Nanoparticles in Synthetic Saliva Probed by AGNES without Previous Solid-Liquid Separation. Comparison with UF-ICP-MS.

The variation over time of free Zn2+ ion concentration in stirred dispersions of ZnO nanoparticles (ZnO NPs) prepared in synthetic saliva at pH 6.80 and 37 °C was followed in situ (without solid-liquid separation step) with the electroanalytical technique AGNES (Absence of Gradients and Nernstian Equilibrium Stripping). Under these conditions, ZnO NPs are chemically unstable due to their reaction with phosphates. The initial stage of transformation (around 5-10 h) involves the formation of a metastable solid (presumably ZnHPO4), which later evolves into the more stable hopeite phase. The overall decay rate of ZnO NPs is significantly reduced in comparison with phosphate-free background solutions of the same ionic strength and pH. The effective equilibrium solubilities of ZnO (0.29-0.47 mg·L-1), as well as conditional excess-ligand stability constants and fractional distributions of soluble Zn species, were determined in the absence and presence of organic components. The results were compared with the conventional ultrafiltration and inductively coupled plasma-mass spectrometry (UF-ICP-MS) methodology. AGNES proves to be advantageous in terms of speed, reproducibility, and access to speciation information.