Commercial ZnO Nanoparticles Research Articles

A Multi-Method Approach for Quantification of Surface Coatings on Commercial Zinc Oxide Nanomaterials.

Surface functionalization is a key factor for determining the performance of nanomaterials in a range of applications and their fate when released to the environment. Nevertheless, it is still relatively rare that surface groups or coatings are quantified using methods that have been carefully optimized and validated with a multi-method approach. We have quantified the surface groups on a set of commercial ZnO nanoparticles modified with three different reagents ((3-aminopropyl)-triethoxysilane, caprylsilane and stearic acid). This study used thermogravimetric analysis (TGA) with Fourier transform infrared spectroscopy (FT-IR) of evolved gases and quantitative solution 1H nuclear magnetic resonance (NMR) for quantification purposes with 13C-solid state NMR and X-ray photoelectron spectroscopy to confirm assignments. Unmodified materials from the same suppliers were examined to assess possible impurities and corrections. The results demonstrate that there are significant mass losses from the unmodified samples which are attributed to surface carbonates or residual materials from the synthetic procedure used. The surface modified materials show a characteristic loss of functional group between 300–600 °C as confirmed by analysis of FT-IR spectra and comparison to NMR data obtained after quantitative release/extraction of the functional group from the surface. The agreement between NMR and TGA estimates for surface loading is reasonably good for cases where the functional group accounts for a relatively large fraction of the sample mass (e.g., large groups or high loading). In other cases TGA does not have sufficient sensitivity for quantitative analysis, particularly when contaminants contribute to the TGA mass loss. X-ray photoelectron spectroscopy and solid state NMR for selected samples provide support for the assignment of both the functional groups and some impurities. The level of surface group loading varies significantly with supplier and even for different batches or sizes of nanoparticles from the same supplier. These results highlight the importance of developing reliable methods to detect and quantify surface functional groups and the importance of a multi-method approach.

Plant extract-assisted biosynthesis of zinc oxide nanoparticles and their antibacterial application

ZnO nanoparticles are multi-purposes materials that can be synthesized by several methods, including physical and chemical routes. A novel synthesis method of ZnO nanoparticles is the biological method using plant extracts as reducing and capping agents, such as the fruit extract of Averrhoa bilimbi. Plant extracts are superior agents for synthesizing nanoparticles because it provides essential phytochemical substances as reductor, capping agents, and free from toxicants. In this study, the effects of precursor concentrations and the amount of plant extract on the formation and morphology of nanoparticles were investigated. The characteristics of ZnO particles were studied by UV-Vis spectroscopy, XRD, FTIR, TEM, and DLS. The study showed that the formation of ZnO nanoparticles occurred after five hours reaction at 70°C, as indicated by color change of the solution. ZnO nanoparticle formation was confirmed by the maximum absorption at the wavelength of 372 nm and XRD analysis. FTIR analysis showed that the as-synthesized ZnO contained significant organic compounds on its surface, especially compared to commercial ZnO. Reduction reactions using A.bilimbi produce nanoparticles in the size from 35.4 to 59.5 nm with round shape and some agglomeration that were observed by TEM. The ZnO antibacterial property was tested against planktonic and biofilm Escherichia coli. The result showed that as-synthesized ZnO have comparable antibacterial antibiofilm property as the commercial ZnO nanoparticles at low concentration. Interestingly, this property was diminished when as-synthesized ZnO nanoparticles were used at high concentrations.

Green synthesis of zinc oxide nanoparticles using Citrus sinensis peel extract and application to strawberry preservation: A comparison study

ZnO nanoparticles synthesized by Citrus sinensis peel extract (SNP) were characterized and compared with commercial ZnO nanoparticles (CNP), and were then applied as nanocoatings on fresh strawberries to evaluate the preservation effect. The results revealed that SNP had a similar crystal structure to CNP, but a higher crystallinity and a larger particle size. The cytotoxicity of SNP towards human umbilical vein endothelial cells (HUVECs) was close to CNP when the concentration was below 25 mg/L. Furthermore, SNP and CNP had a similar minimum inhibitory concentration (MIC) against E. coli and S. aureus, but SNP showed a significantly lower minimum bactericidal concentration (MBC) against E. coli compared with CNP. Higher antifungal activities of CNP against Botrytis cinereal purified from mildewed strawberries compared with SNP were found when the concentration was lower than 400 mg/L. When SNP and CNP were incorporated into carboxymethylcellulose sodium (CMC) and coated on fresh strawberries, both coatings significantly decreased the weight loss and the rate of rotting, and also improved the storage quality. Therefore, SNP prepared by the green method has great potential in food packaging application.

Antimicrobial Bilayer Nanocomposites Based on the Incorporation of As-Synthetized Hollow Zinc Oxide Nanotubes.

An antimicrobial polymeric bilayer structure based on the application of an acrylic coating containing hollow zinc oxide nanotubes over a polymeric substrate was developed in this work. Firstly, zinc oxide nanotubes (ZnONT) were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers followed by polymer removal through calcination with the purpose of obtaining antimicrobial nanostructures with a high specific area. Parameters of electrospinning, ALD, and calcination processes were set in order to obtain successfully hollow zinc oxide nanotubes. Morphological studies through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) microscopies confirmed the morphological structure of ZnONT with an average diameter of 180 nm and thickness of approximately 60 nm. Thermal and X-ray diffraction (XRD) analyses provided evidence that calcination completely removed the polymer, resulting in a crystalline hexagonal wurtzite structure. Subsequently, ZnONT were incorporated into a polymeric coating over a polyethylene extruded film at two concentrations: 0.5 and 1 wt. % with respect to the polymer weight. An antimicrobial analysis of developed antimicrobial materials was performed following JIS Z2801 against Staphylococcus aureus and Escherichia coli. When compared to active materials containing commercial ZnO nanoparticles, materials containing ZnONT presented higher microbial inhibition principally against Gram-negative bacteria, whose reduction was total for films containing 1 wt. % ZnONT. Antiviral studies were also performed, but these materials did not present significant viral reduction.

The effect of different nanocatalysts for photocatalytic degradation of methylene blue

The aim of this study was to investigate photodegradation of Methylene Blue (MB) in water by using ZnO and TiO2 nanoparticles. Adsorption and photocatalytic oxidation studies were carried out by using produced TiO2, commercial TiO2 and commercial ZnO nanoparticles. In order to evaluate performance tests, 5 mg/l of MB solution was used. The samples were mixed in the dark for 2 hours for establishing adsorption-desorption equilibrium. The photocatalytic tests of the samples were performed by assessing the decomposition rate of MB solutions under UV light. The results of the photocatalytic showed that the highest color removal efficiencies was obtained by TiO2 catalyst where Methylene blue solution was completely degraded.

VO2-ZnO composite films with enhanced thermochromic properties for smart windows

VO2 film is a promising thermochromic material in smart windows due to its reversible metal to insulator transition (MIT) accompanied with an abrupt change of transmittance in near-infrared region at around 68 °C (T>68 °C, translucent; T < 68 °C, transparent), but which has not been widely applied because its low luminous transmittance (<60%) and solar modulation efficiency (<10%) are difficult to be improved simultaneously. In order to solve this problem, the ZnO-VO2 composite film was prepared by a facile method, in which commercial ZnO nanoparticles (NPs) and VO2 micro-particles were mixed by ball milling method to form the composites. By introducing ZnO NPs into the composite film, the luminous transmittance (Tlum) of the composite film was increased by 16.9% (from 54.9% to 63.9%) and the solar modulation efficiency (ΔTsol) was increased by 14.1% (from 9.9% to 11.3%) compared to the pure VO2 composite film. This was because ZnO NPs not only played the role of antireflection, but also prevented VO2 particles from agglomeration by dispersing around VO2 particles. Furthermore, the two-layered film based on ZnO-VO2 composites exhibited an astonishing ΔTsol of 18.8%, while maintaining excellent Tlum of 54.3%. This work could provide a simple and novel idea for us to improve the thermochromic properties of VO2 films and simultaneously to promote their practical application.

Photocatalytic treatment of a multicomponent petrochemical wastewater by floatable ZnO/Oak charcoal composite: Optimization of operating parameters

This paper aims to investigate the potential of photocatalytic processes for the degradation of multicomponent industrial wastewaters. Commercial ZnO nanoparticles were immobilized on pieces of carbonized Oak as a floatable support and it was applied for the decontamination of industrial ammonia wastewater from a petrochemical plant under UV irradiation. Wastewater characterization confirmed the presence of ammonia, BOD, COD, CaCO3, Cl− and SO42−. Box-Behnken experimental design was used to find out the best experimental conditions and the maximum ammonia removal. A second-order polynomial model in terms of pH, catalyst dosage and light intensity was suggested for prediction of the maximum efficiency of ammonia removal. Accuracy of the model was verified by p-value of the model (< 0.0001), p-value of lack of fit (0.3987), R2 (0.9854) and adjusted R2 (0.9666). This model suggested that light intensity is the most effective parameter maximizing the ammonia removal. The optimum conditions under which the maximum ammonia removal of 86.7% was observed are as follows: pH 9, catalyst dosage of 2 g/L, and light intensity of 250 W. This efficiency is close to the predicted value of 93%. The other contaminants present in the wastewater were also decomposed significantly by ZnO/Oak charcoal composite. This study can be useful for who are working on the real applications of photocatalysis processes.

Visible Light-driven Photocatalytic Performance of Zno Coupled with Up-conversion Phosphors for the Removal of Methylene Blue

In this work it was investigated the photocatalytic activity of ZnO coupled with inorganic “up-conversion” phosphors for the treatment of aqueous solutions polluted with methylene blue (MB), in the presence of visible light irradiation. Specifically, the successfully prepared “up-conversion” phosphors nanoparticles emit, when excited with visible light, UV light with main emission at 365 nm. The photocatalytic tests were carried out in a cylindrical pyrex photoreactor equipped with a magnetic stirrer to ensure the continuous mixing of the physical mixtures of “up-conversion” phosphors and commercial ZnO nanoparticles in the solution and irradiated by visible light instead of UV light normally required to excite ZNO. Experimental results were analysed by evaluating the MB decolourization through spectrophotometric method and the total organic carbon (TOC) through high temperature combustion method. In particular, it was found that the photocatalytic performances obtained using ZnO nanoparticles coupled with “up-conversion” phosphors are strongly increased compared to the use of ZnO alone. These results confirmed the enhancement of photocatalytic performances induced by UV photons emitted by “up-conversion” phosphors nanoparticles, able to activate ZnO, demonstrating how their use in photocatalytic systems can be an alternative to the traditional UV lamps, thus preserving human health, environmental and, at the same time, allows to save the energy in process management.

Double-sided plasmonic silver nanoparticles decorated copper oxide/zinc oxide heterostructured nanomaces with improving photocatalytic performance

The CuO/ZnO heterostructured nanomaces can be directly grown on the copper gauze substrates with CuO nanowires by a wet chemical approach at the lower reaction temperature. The concentration of ZnO precursor can easily control the sizes of ZnO branched nanowires. CuO/ZnO heterostructured nanomaces presented superior photocatalytic activity toward rhodamine 6 G removal compared with commercial ZnO or TiO2 nanoparticles under low-powered UV-light irradiation. Further investigation has revealed that CuO/ZnO heterostructured nanomaces significantly improved activity as a recyclable photocatalyst for the degradation of rhodamine 6 G. Also, the uniform sizes of Ag nanoparticles can decorate onto the interface and surface of CuO/ZnO heterostructured nanomaces via a sample ion-beam sputtering method. The quaternary CuO/Ag/ZnO/Ag heterostructured nanomaces can provide the adequate separation of photoinduced electron-hole pairs and more surface active sites, which exhibited a higher photocatalytic efficiency rather than CuO/ZnO heterostructured nanomaces.

Direct sunlight-driven degradation of 2-chlorophenol catalyzed by kaolinite-supported ZnO

Commercial and laboratory-prepared ZnO nanoparticles are assessed here as a photocatalyst in photodegradation of aqueous 2-chlorophenol under direct sunlight. Kaolinite is used as a support for ZnO to enable its recovery after reuse. The composite ZnO/kaolinite is prepared by growing ZnO nanoparticles directly on kaolinite surface and is characterized by a number of methods such as electronic absorption spectra, photoluminescence spectra, X-ray diffraction and scanning electron microscopy. All ZnO systems (commercial, synthetic and supported) exhibit the wurtzite phase. The composite ZnO/kaolinite shows higher photocatalysis efficiency in 2-chlorophenol degradation over both commercial and synthetic ZnO powders. The composite ZnO/kaolinite is also easier to recover and reuse, showing no observable loss in its catalyst efficiency even after five cycles. These features highlight the merit of using composite ZnO/kaolinite as photocatalyst in water purification with direct sunlight for the first time. All catalyst systems are more efficient in basic media (pH ~ 8.5) than in neutral and acidic media, as rationalized by the point of zero charge concepts here. Moreover, the composite ZnO/kaolinite shows enhanced catalytic efficiency in 2-chlorophenol photodegradation in a wider pH range, compared to other counterparts, which shows another added value.

Low-cost writing method for self-powered paper-based UV photodetectors utilizing Te/TiO2 and Te/ZnO heterojunctions.

It has always been a challenge to prepare self-powered ultraviolet photodetectors (UV PDs) utilizing a green, facile and low-cost method. Here, we provide such an approach for fabricating self-powered photodetectors based on Te nanowire/TiO2 nanoparticle (NP) and Te nanowire/ZnO nanoparticle (NP) heterojunctions. It is noteworthy that such devices were prepared via simply brushing non-toxic solution-processed Te nanowires and commercial TiO2 and ZnO nanoparticles onto paper. The as-obtained UV PDs can work under zero bias due to photovoltaic effects from the Te/TiO2 and Te/ZnO heterojunctions. This study not only presents high-performance UV PDs, but also provides a general and effective method for developing environmentally-friendly and energy-efficient optoelectronic devices for practical applications. The concept of employing daily-use brushes and recyclable paper provides a facile way to fabricate green low-cost PDs.

Sulfuric acid treatment of ZnO photoelectrode for photovoltaic improvement in dye-sensitized solar cell

Chemical wet treatment of ZnO films using the diluted sulfuric acid for dye-sensitized solar cell application was performed. The ZnO films were prepared from commercial ZnO nanoparticles using screen printing method and annealed. The films were treated by dipping into diluted sulfuric acid for different treatment times. Morphology of the treated ZnO films shows the nanowire formation for long treatment time. The treated ZnO films were then used as photoelectrode of dye-sensitized solar cell. The power conversion efficiency is achieved to be maximal value for the dye-sensitized solar cell fabricated with the treated ZnO films. It reveals the higher than the dye-sensitized solar cell fabricated with the non-treated ZnO films. The enhancement is due to the increased open-circuit voltage, the increased fill factor, the increased shunt resistance, and the decreased charge transfer resistance. In addition, the effect of sulfuric acid treatment is found to improve the charge transfer behaviour due to the nanowire formation. Therefore, the sulfuric acid treatment of ZnO photoelectrode has potential to provide charge transfer rate for better dye-sensitized solar cell application.

Novel meta- and AB-Polybenzimidazole/Zinc oxide polymer hybrid nanomaterials for photocatalytic degradation of organic dyes

New nanocomposites of m-PBI/ZnO and AB-PBI/ZnO – powders and films, containing 2.5 wt% and 5 wt% ZnO, were prepared using two different approaches: mixing commercial ZnO nanoparticles with dimethylacetamide solution of m-PBI and in situ synthesis of ZnO in alkali-ethanol AB-PBI solution. The photocatalytic activity of the materials prepared was tested for photodegradation under UV-light of model organic dyes pollutants, in aqueous media. The powder catalysts exhibit higher photocatalytic efficiency towards degradation of all three tested dyes, compared to the films. The materials containing 2.5 wt% ZnO are usually more efficient than these with 5 wt% ZnO. The highest degree of degradation (97%) was achieved for Malachite Green dye, using m-PBI/2.5 wt% ZnO powder.

Plasma Treatment of Metal Oxide Nanoparticles: Development of Core–Shell Structures for a Better and Similar Dispersibility

Low-pressure plasma polymerization of cyclopropylamine was employed for the surface functionalization of commercial ZnO, Al2O3, and ZrO2 nanoparticles in a homemade hollow cathode plasma reactor. The analysis of the modified nanoparticles by X-ray photoelectron spectroscopy (XPS) revealed the incorporation of reactive functional groups such as primary and secondary amines, which was confirmed by Fourier transform infrared spectroscopy (FTIR). The raw and the plasma functionalized nanoparticles were evaluated in terms of dispersibility. Application of Hansen solubility parameters (HSP) theory showed that the efficient plasma polymerization that led to the deposition of an approximately 5 nm thick plasma polymer film, as determined by transmission electron microscopy (TEM), causes a similar shift toward the Hansen solubility space for the functionalized nanoparticles and changes their physicochemical affinity within selected solvents, regardless of the kind of nanoparticles used. Hence, a combined exploitat...

In-situ functionalization of mesoporous hexagonal ZnO synthesized in task specific ionic liquid as a photocatalyst for elimination of SO2, NOx, and CO

A novel mesoporous structure of zinc oxide was synthesized in hydrothermal autocalve in the presence of a functional ionic liquid (FIL) {[CH2CH2] O2 (mm)2}. This FIL with ether groups was used simultaneously as a designer templating agent and a source of the hydroxyl radical. The presence of this ionic liquid led to producing ethylene glycol in the reaction media, which adsorb on the surface of mesoporous hexagonal ZnO plates. These mesoporous structures can adsorb pollutant gases and increase photocatalytic oxidation of pollutant gases in compare with commercial ZnO nanoparticles and agglomerated nanoparticles synthesized in this work. XPS data confirmed ethylene glycol production by the ionic liquid, which could prove a role for ionic liquids as designers. The estimated BET surface area values of ZnO hexagonal mesoporous plates and agglomerated particles were 84m2/g and 12m2/g respectively. Optical properties of the mesoporous structures were analyzed by photoluminescence spectroscopy and diffuse reflectance UV–visible spectroscopy. The performance of these structures as efficient photocatalysts was further demonstrated by their removal of NOx, SO2, and CO under UV irradiation. The removal of NOx, SO2, and CO under UV irradiation was 56%, 81%, and 35% respectively, after 40min of irradiation time. Reusability of the photocatalyst was determined; the results show no significant decrease of activity of photocatalyst. after five cycles.

Methodology for sample preparation and size measurement of commercial ZnO nanoparticles

This study discusses the strategies on sample preparation to acquire images with sufficient quality for size characterization by scanning electron microscope (SEM) using two commercial ZnO nanoparticles of different surface properties as a demonstration. The central idea is that micrometer sized aggregates of ZnO in powdered forms need to firstly be broken down to nanosized particles through an appropriate process to generate nanoparticle dispersion before being deposited on a flat surface for SEM observation. Analytical tools such as contact angle, dynamic light scattering and zeta potential have been utilized to optimize the procedure for sample preparation and to check the quality of the results. Meanwhile, measurements of zeta potential values on flat surfaces also provide critical information and save lots of time and efforts in selection of suitable substrate for particles of different properties to be attracted and kept on the surface without further aggregation. This simple, low-cost methodology can be generally applied on size characterization of commercial ZnO nanoparticles with limited information from vendors.

Hexagonal bottom-neck ZnO nano pencils: A study of structural, optical and antibacterial activity

We have shown a protocol for the synthesis of monodispersed, reproducible hexagonal bottom-neck ZnO nano pencils which eliminate the usage of specific reaction conditions and substrate for the growth of the particles. The particles were synthesized from the aqueous extract of pomegranate peels under the sunlight irradiation and were characterized by spectroscopic and microscopic techniques. We have studied the anti-bacterial activity of the synthesized nanoparticles using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). Furthermore, we compared the activity of the particles with the commercial ZnO nanoparticles and ZnO nano rods.

Effects of ageing conditions on degradation of acrylonitrile butadiene rubber filled with heat-treated ZnO star-shaped particles in rapeseed biodiesel

The degradation of acrylonitrile butadiene rubber (NBR) after exposure to biodiesel at different oxygen partial pressures in an automated ageing equipment at 80 °C, and in a high-pressure autoclave at 150 °C was studied. The oxidation of biodiesel was promoted by an increase in oxygen concentration, resulting in a larger uptake of fuel in the rubber due to internal cavitation, a greater decrease in the strain-at-break of NBR due to the coalescence of cavity, and a faster increase in the crosslinking density and carbonyl index due to the promotion of the oxidation of NBR. During the high-temperature autoclave ageing, less fuel was absorbed in the rubber, because the formation of hydroperoxides and acids was impeded. The extensibility of NBR aged in the autoclave decreased only slightly due to the cleavage of rubber chains by the biodiesel attack. The degradation of NBR in the absence of carbon black was explained as being due to oxidative crosslinking. The dissolution of ZnO crystals in the acidic components of biodiesel was retarded by removing the inter-particle porosity and surface defects through heat treating star-shaped ZnO particles. The rubber containing heat-treated ZnO particles swelled less in biodiesel than a NBR filled with commercial ZnO nanoparticles, and showed a smaller decrease in the strain-at-break and less oxidative crosslinking.

Effect of different nanoparticles based coating on the performance of textile properties

Facile approach has been developed for synthesis of coating layer for different textile fabrics. Coating layer composed from binder and metal oxide nanoparticles prepared by one step method using ultrasonication for uniform dispersion of nanoparticles. Then, prepared coating was coated on textiles imparting multifunctional properties to the treated textile fibers. Textile coating layer was prepared based on commercial binder, TiO2 and ZnO nanoparticles of an average particle size of 20 nm. Effect of dispersion and mass ratio of TiO2 and ZnO nanoparticles were studied. The ultraviolet protection factor of treated fabrics was significantly enhanced achieved more than six fold and 3 fold compared to untreated and binder treated samples respectively. Antibacterial behavior against staphylococcus aureus bacteria was studied achieved 23.5 mm clear inhibition zone compared to zero for blank textiles. Furthermore, mechanical properties of the untreated and treated samples were investigated. This is in addition to evaluation of the hydrophobic properties of coated textiles achieving super-hydrophobic surface with water contact angle of 160°.

Influence of water chemistry on the environmental behaviors of commercial ZnO nanoparticles in various water and wastewater samples

Zinc oxide nanoparticles (ZnO NPs) are widely used nanomaterials and their environmental impacts have received increasing attention. The fate and toxicity of ZnO NPs in the environment are determined by their stability and dissolution. In this study, the influence of water chemistry on aggregation, sedimentation, and dissolution of ZnO NPs was investigated. The stabilized ZnO NPs aggregated and precipitated when the aqueous pH closed to their zero point of charge (pHzpc). Counter-ions neutralized the surface charge of NPs and promoted their destabilization. However, a high concentration of counter-ion (SO42−, >10meq/L) made the NPs more stable because of the inverted surface potential. The stability of ZnO NPs was maintained by high concentration of Suwannee River humic acid (SRHA, 10mg/L) even the concentration of electrolytes was high. The influence of water chemistry on the stability and dissolution of ZnO NPs was further demonstrated in different wastewaters. In one wastewater sample, ZnO NPs was unexpectedly stable and with a high dissolution, which was due to the effects of pH value, organic matter concentration, as well as the concentration of counter ions. Our findings facilitate the predictions of the fate of stabilized ZnO NPs in the environment.