Modified Zinc Oxide Research Articles

Fast NMR relaxation, powder wettability and Hansen Solubility Parameter analyses applied to particle dispersibility

The selection of appropriate solvents into which inorganic and organic sub-micron particles can be dispersed is important for product manufacturability and performance. Molecular-level interactions determine solvent suitability but are difficult to measure; existing experimental approaches require slow/expensive tests of dispersion stability. Solvent relaxation NMR measurements are shown to be a fast indicator of solvent suitability, with sensitivity to the solvent-particle intermolecular forces making it a reliable proxy for stability measurements. A structured approach to relaxation measurements with a selection of both good and poor solvents yields the Hansen Solubility Parameters (HSP) for the particle surface. Suitable solvents can be selected from a database of HSP values, and solvents can be blended to match the particle interface. The application of the approach is illustrated using a range of surface modified zinc oxide and aluminum oxide particles, with similarities and differences between the particle surfaces becoming evident through the analysis.

Room-temperature ferromagnetism on ZnO nanoparticles doped with Cr: An experimental and theoretical analysis

The experimental and theoretical structural, optical, and magnetic properties of Cr modified Zinc Oxide nanoparticles synthesized by thermal decomposition route were studied, finding a good agreement between them. Rietveld refinement of the XRD data shows that the samples belong to the P63mc space group with a Wurtzite structure. Moreover, a slight decrease in lattice parameters indicates that Cr substitutes Zn atoms in the lattice. The absorption spectra show a decrease in bandgap energy with increasing Cr doping, confirming the decisive role of Cr ion in the optical properties of ZnO. First-principles calculations also confirmed the reduction of the band-gap because of the introduction of impurity states. Magnetic measurements exhibit room temperature weak-ferromagnetism (RTFM) and increase the remnant magnetization (Mr) with increasing Cr doping. Furthermore, first-principles calculations demonstrate the presence of ferromagnetism for Cr doping up to 8% supported by experimental results. When Cr doping is 8%, theoretical results suggest possible agglomeration of the Cr atoms to form metallic-antiferromagnetic chromium oxide. However, when Cr is well dispersed into the lattice -as suggested by XRD measurements-, both ferromagnetic and antiferromagnetic behavior are degenerated, making possible the room-temperature ferromagnetic behavior.

Suppressing the Photocatalytic Activity of Zinc Oxide Electron-Transport Layer in Nonfullerene Organic Solar Cells with a Pyrene-Bodipy Interlayer.

Organic solar cells based on nonfullerene acceptors have recently witnessed a significant rise in their power conversion efficiency values. However, they still suffer from severe instability issues, especially in an inverted device architecture based on the zinc oxide bottom electron transport layers. In this work, we insert a pyrene-bodipy donor-acceptor dye as a thin interlayer at the photoactive layer/zinc oxide interface to suppress the degradation reaction of the nonfullerene acceptor caused by the photocatalytic activity of zinc oxide. In particular, the pyrene-bodipy-based interlayer inhibits the direct contact between the nonfullerene acceptor and zinc oxide hence preventing the decomposition of the former by zinc oxide under illumination with UV light. As a result, the device photostability wassignificantlyimproved. Theπ-π interaction between the nonfullerene acceptor and the bodipy part of the interlayer facilitates charge transfer from the nonfullerene acceptor toward pyrene, which is followed by intramolecular charge transfer to bodipy partand then to zinc oxide. The bodipy-pyrene modified zinc oxide also increased the degree of crystallization of the photoactive blend and the face-on stacking of the polymer donor molecules within the blend hence contributing to both enhanced charge transport and increased absorption of the incident light. Furthermore, it decreased the surface work function as well as surface energy of the zinc oxide film all impacting in improved power conversion efficiency values of the fabricated cells with champion devices reaching values up to 9.86 and 11.80% for the fullerene and nonfullerene-based devices, respectively.

Defect modified zinc oxide with augmenting sonodynamic reactive oxygen species generation

Poor chemical stability, low tumor enrichment, and weak therapeutic effects of commonly used organic sonosensitizers significantly hinder further clinical applications of sonodynamic therapy (SDT). Encouraged by the principles of semiconductor catalysis and defect chemistry, we obtained a defect-rich gadolinium (Gd) doped zinc oxide (D-ZnOx:Gd) semiconductor sonosensitizer by defect engineering for efficient deep tumor sonodynamic eradication. The abundant oxygen defect can promote the separation of the electron (e−) and hole (h+) of D-ZnOx:Gd, which significantly enhances the sonodynamic effect. In addition, D-ZnOx:Gd is more easier to adsorb water and oxygen molecules due to its rich oxygen-deficient, greatly enhancing the capacities of ROS production. A significantly higher sonodynamic ROS generation abilities and anti-deep tumor efficiency against breast cancer are obtained in such defect-rich ZnO nanobullets. This work not only broadens the applications of ZnO semiconductor nanoagent in the field of nanomedicine, but also reveals the mechanism of how the oxygen deficiency enhanced the sonodynamic efficacy of zinc oxide, providing a new application of defect engineering in the field of cancer therapy.

The effects of modified zinc oxide nanoparticles on the mechanical/thermal properties of epoxy resin

AbstractCharacterized by its strength, durability, and thermal properties, epoxy resin has been widely used as an adhesive, paint, and coating in many applications in the aerospace, civil and automotive industries. Despite this, the thermoset polymer resin has been known for its brittleness and low fracture resistance. This study focuses on the reinforcement of an epoxy resin system (diglycidyl ether of bisphenol A) with zinc oxide (ZnO) nanoparticles in their pristine form and a further modified form. The modification took place in two ways: coating with polydopamine (PDA) and covalently functionalizing them with (3‐aminopropyl)triethoxysilane (APTES) and (3‐glycidoxypropyl)trimethoxysilane (GPTMS). Therefore, four different types of nanoparticles were used: pristine ZnO, ZnO/PDA, ZnO/GPTMS, and ZnO/APTES aiming to improve the interfacial bonding between the polymeric matrix and the reinforcement. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy characterization and imaging techniques were used to prove that the ZnO nanoparticles were successfully modified prior to manufacturing the epoxy composites. While tensile testing showed that using pristine ZnO increases the composite's strength by 32.14%, the fracture toughness of the resin was improved by 9.40% when reinforced with ZnO functionalized with APTES. TGA showed that the addition of functionalized nanoparticles increases the material's degradation temperature by at most 7.31 ± 4.9°C using ZnO/APTES. Differential scanning calorimetry and dynamic mechanical analysis testing proved that the addition of any type of nanoparticles increases the resin's glass transition temperature by as much as 7.83°C (ZnO/APTES).

Highly sensitive C2H2 gas sensor based on Ag modified ZnO nanorods

The sliver (Ag) modified zinc oxide (ZnO) nanorods were successfully obtained with a simplified and environmentally friendly solvothermal method. Materials characterization indicated that the metallic Ag was located on the outside of ZnO nanorods after annealing. In comparison with ZnO nanorods, Ag modified ZnO (Ag–ZnO) nanorods exhibited a considerably enhanced response to C2H2. The response of the 3 at% Ag–ZnO based sensor operating at 175 °C is 539 (Ra/Rg), which is the highest value among all the sensors in detecting 100 ppm C2H2. The Ag–ZnO based sensors exhibited fast response speed, lower operation temperature and higher selectivity.

Improvement in hole transporting ability and device performance of quantum dot light emitting diodes.

In this research, we demonstrate a novel approach to improve the device performance of quantum dot light emitting diodes (QLEDs) by blending an additive BYK-P105 with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the hole transport layer. In addition, for the first time, polyethylenimine ethoxylated (PEIE)-modified zinc oxide nanoparticles (ZnO NPs) as the electron transport layer were applied in regular-type QLEDs for achieving high device efficiency. A very high brightness of 139 909 cd m−2 and current efficiency of 27.2 cd A−1 were obtained for the optimized device with the configuration of ITO/PEDOT:PSS + BYK-P105/PVK/CdSe QDs/ZnO NPs/PEIE/LiF/Al that shows promising use in light-emitting applications.

Modified Zinc Oxide Nanoparticles for Corrosion Resistance Applications

Atmospheric corrosion is a big threat to the steel structures. This is because it compromises its structural integrity, aesthetic aspects and overall efficiency. An attempt has been made to counteract this through surface engineering of substrates including glass and steel by using modified zinc oxide nanoparticles to increase hydrophobicity. The synthesis of zinc oxide nanoparticles is carried out by using sol-gel method, thereafter these particles were modified by using stearic acid; a fatty acid. The zinc oxide nanoparticles were characterized by using X-ray diffraction analysis (XRD) which confirms the presence of hexagonal wurtzite structure. Moreover, the Scanning Electron microscopy (SEM) reveals the hexagonal wurtzite morphology of as prepared nanoparticles. Fourier transform infrared spectroscopy (FTIR) confirms the grafting of stearic acid on the surface of ZnO in bidentate form. The water Contact Angle obtained by using sessile drop method gives a statistical value of 140o which is of great interest due to higher water repellency and lower surface contact area. Finally, corrosion test was carried out on the coated steel substrate by means of conventional corrosion testing technique and it is observed that the coated sample decays three times slower than that of its bare steel counterpart.

Modified Zinc Oxide Nanoparticles for Corrosion Resistance Applications

Atmospheric corrosion is a big threat to the steel structures. This is because it compromises its structural integrity, aesthetic aspects and overall efficiency. An attempt has been made to counteract this through surface engineering of substrates including glass and steel by using modified zinc oxide nanoparticles to increase hydrophobicity. The synthesis of zinc oxide nanoparticles is carried out by using sol-gel method, thereafter these particles were modified by using stearic acid; a fatty acid. The zinc oxide nanoparticles were characterized by using X-ray diffraction analysis (XRD) which confirms the presence of hexagonal wurtzite structure. Moreover, the Scanning Electron microscopy (SEM) reveals the hexagonal wurtzite morphology of as prepared nanoparticles. Fourier transform infrared spectroscopy (FTIR) confirms the grafting of stearic acid on the surface of ZnO in bidentate form. The water Contact Angle obtained by using sessile drop method gives a statistical value of 140o which is of great interest due to higher water repellency and lower surface contact area. Finally, corrosion test was carried out on the coated steel substrate by means of conventional corrosion testing technique and it is observed that the coated sample decays three times slower than that of its bare steel counterpart.

Near-infrared emission from modified zinc oxide hybrid nanostructures

Near-infrared emission is receiving of attention due to its wide range of applications in imaging, optoelectronics and telecommunication. Here, we synthesize rare earth based organic complexes and use them to endow near-infrared emission capability into two-dimensional nanostructured transparent conducting oxide, specifically zinc oxide nanowalls. The hybrid ZnO nanowalls with Nd3+ complex are found to successfully generate characteristic near-infrared emissions at 887, 1066 and 1334 nm. X-ray photoelectron spectroscopy and theoretical calculations show that the interfacial interactions between ZnO and the Nd3+ complex are driven by nitrate anions in the complex. Based on these results, we propose an unique cascade energy transfer mechanism from ZnO to Nd3+ via 1,10-phenanthroline, which could be generalized to account for emission of other similar hybrid systems.

Reduced graphene oxide modified zinc oxide composites synergistic photocatalytic activity under visible light irradiation

Semiconductor photocatalytic technology is widely regarded as a potential solution to global energy shortages and defense against environmental degradation. Here we demonstrate zinc oxide (ZnO) nanosheets (NSs)-reduced graphene oxide (rGO) nanocomposites were synthesized by a facile one-step hydrothermal method. The as-obtained ZnO/rGO-x (x = 2–12 wt %) samples with different rGO contents are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), infra-red (IR) spectroscopy, the ultraviolet-visible spectroscopy (UV–vis), diffuse spectroscopy and photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and their photocatalytic are also evaluated. In the photocatalytic process, graphene modified zinc oxide can achieve interface enhancement, reduce the fast recombination efficiency of electron-hole pairs, and enhance its absorption in the visible area. The content of GO shows an obvious effect on their photocatalytic properties, ZnO/rGO-8 sample can completely degrade methylene blue within 80 min under the same conditions. The excellent photocatalytic properties of the nanocomposites are due to the synergy between ZnO and rGO.

NIR light active ternary modified ZnO nanocomposites for combined cancer therapy

Recent developments in nanomedicine for cancer therapy enable nanoparticles for tumour specific therapeutics. Certain nanoparticles with their inherent physical/chemical properties can themselves act as drugs. Also they can be designed to respond to either tumor microenvironment or externally applied physical stimuli such as temperature, light, magnetic field, and ultrasound for tumor-targeted and enhanced anticancer efficacy. In this study, a simple design of cost-effective ternary modified zinc oxide nanocomposites possessing near-infrared (NIR) absorbance were synthesized using simple, fast, thermal decomposition route with hydrazine precursors. The in vitro cytotoxicity of these nanocomposites studied on human breast cancer cells (MCF-7) and the human embryonic kidney normal cells (HEK 293) by MTT assay show that they are highly selective and are dose dependent against both the cell lines. The developed nanocomposites can be used for combined photothermal (PTT) and photo dynamic (PDT) cancer therapy.

Raman spectroscopy of zinc oxide nanoplatelets modified with ruthenium (II) complexes

AbstractWe analyzed and compared the unmodified and three modified zinc oxide nanoplatelet materials. The three components used in zinc oxide modification were the 4,4apos;‐bipyridine and two ruthenium (II) complexes, namely, the trans‐[Ru (bpy)(bpyCOO)Cl2]2– and cis‐[Ru (bpy)(bpyCOO)Cl2]2–. The obtained results revealed that after modification, ZnO nanoplatelets became smaller and embedded in the materials used for the modification. When ZnO was modified with either of the two ruthenium (II) complexes, the interaction between them led to a higher activity of ZnO. The metal‐to‐ligand charge transfer that was also detected in the two cases of ZnO nanoplatelets modified with the ruthenium (II) complexes caused significant alteration of the Raman spectrum and consequent changes of the optical properties. Various forms of ruthenium (II) complexes were used in several published studies related to dye‐sensitized solar cells and biomedicine. The biomedical applications include, for example, the ATP (adenosine‐5apos;‐triphosphate) detection, interaction with human serum albumin, DNA analysis, and cancer detection and treatment. The properties of the ZnO nanoplatelets modified with the two ruthenium (II) complexes presented here indicate that it may be worth exploring if the studied materials are applicable in the dye sensitized solar cells and biomedicine. Possible advantage of our results is that they were obtained at room temperature.

Preparation Of Superhydrophobic Zinc Oxide Nanorods Coating On Stainless Steel Via Chemical Bath Deposition

The stearic acid modified zinc oxide nanorod surface was coated with a stainless steel substrate to improve the contact angle and the sliding angle. Facilitated through ZnO seeding on the substrate, the ZnO nanorod was deposited via chemical bath deposition at different precursor concentrations. The surface hydrophobicity was modified by varying concentrations of stearic acid at and submmersion time. The contact angle was investigated in relation to the surface microstructure and modification. Results indicate that the density of ZnO nanorods on the substrate surface and stearic acid coverage are prerequisites for improving surface hydrophobicity. Superhydrophobic properties with a contact angle of 162° was obtained for ZnO deposited with 35 mM zinc nitrate and submerged in 8 mM stearic acid for 36 h, which allowed 5 μL water droplets to slide at 3.8°.

Effect of modified nano zinc oxide on physico-chemical and antimicrobial properties of gamma-irradiated sawdust/epoxy composites

The present study aims to investigate the influence of modified zinc oxide nanoparticles content on the physico-chemical properties of sawdust/epoxy composite specimens. The results show an improvement in the mechanical properties in terms of flexural strength, impact strength, and hardness with increasing the modified zinc oxide nanoparticles content up to 5%, while the physical properties such as water absorption and thickness swelling percentages are decreased directly with increasing the content of modified zinc oxide. In addition, the behavior of irradiated composite specimens containing 5% modified zinc oxide nanoparticles at different gamma-irradiation doses, 10, 30, and 50 kGy, has been studied. The results indicate that the irradiated composite specimens at 10 kGy have better physico-chemical properties as compared to the unirradiated specimens. Furthermore, the antimicrobial properties of composite specimens containing 5% modified zinc oxide at 0 kGy and 10 kGy against different plant pathogenic fungi and bacteria are also discussed. The results demonstrate that the growth activity of fungi and bacteria on the composite specimens are reduced to a great extent as compared to the control composite specimens (0% of zinc oxide nanoparticles). Thermal behavior and morphology of the prepared specimens are detected using thermogravimetric analysis and scanning electron microscopy technique.

Eco-friendly castor oil-based UV-curable urethane acrylate zinc oxide nanocomposites: Synthesis and viscoelastic behavior

Attention to environmental problems and the importance of maintaining it have caused the researchers to pay more attention in this regard. The production of polymers and resins has increased in recent years and has affected by environmental pollution due to their long-term degradation. An appropriate solution to this problem is the synthesis of degradable and environmentally friendly polymers and resins. Using natural materials in the synthesis of polymers and resins can help them to be environmentally friendly. The purpose of this research is to synthesize urethane acrylate resins using natural resources. For this purpose, the urethane acrylate pre-polymer was synthesized with castor oil. Then, using modified zinc oxide nanoparticles with 1, 3 and 5 wt% urethane acrylate zinc oxide nanocomposites were produced. The use of castor oil as a degradable part and lack of organic solvent in radiation systems led to the creation of an environmentally friendly resin. Subsequently, the viscoelastic behavior of the prepared nanocomposite was evaluated. Spectrometry results confirm the synthesized resin structure. The morphology of nanocomposites confirmed the proper particle size distribution in a 3 wt.% sample. The results of the dynamic mechanical thermal analysis test showed that increasing the amount of modified nano ZnO could increase the glass transition temperature, and the maximum value was observed in 5 wt.% modified nano ZnO (69.7℃).

Ce-Ag-ZnO/Fe3O4 nanocomposites: A novel magnetically separable photocatalyst for highly efficient photodegradation of contaminants

The preparation of Ce, Ag codoped ZnO/Fe3O4 nanoparticles (Ce-Ag-ZnO/Fe3O4) has been successfully performed employing the co-precipitation method. This method is performed in large scales, mild and does not include any template, surfactant or additive. The products have been characterized by some characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL) and vibrating sample magnetometer (VSM). Besides, photocatalytic behavior of the nanoparticles was examined by photodegradation of methylene blue (MB) under UV light irradiations. The photocatalyst of modified zinc oxide exhibited a higher photocatalytic activity rather than pure zinc oxide. Also, the highest photocatalytic activity was attributed to the Ce-Ag-ZnO/Fe3O4 samples, having the lowest recombination rate for the photogenerated electrons and holes and the lowest band gap energy as well. The obtained results indicated that the Ce-Ag-ZnO/Fe3O4 can potentially be employed as an efficient photocatalyst for practical wastewater treatment.

Surface Modified Zinc Oxide Nanoparticles as Smart UV Sensors

The present paper examines the synthesis of ZnO nanoparticles and their surface modification via the microwave assisted sonochemical method along with its successful application in designing a smart UV sensor. The structure of the prepared samples was investigated using XRD, XPS and its respective crystallinity studies. The photoluminescence spectroscopy identified an increase in the green emission intensity due to surface modification which is attributed to the density of oxygen vacancies. The variation in the dielectric constant and dielectric loss values with surface modification is clearly substantiated. As a case study, it was observed a smart UV sensor fabricated using this surface modified ZnO response and decay time that are 14 s and 16 s, respectively. Also, the possibility of surface modification in tuning the sensing responses has been investigated in detail.

Effects on structure, surface oxygen defects and humidity performance of Au modified ZnO via hydrothermal method

In this paper, different approaches for the preparation of gold (Au) modified zinc oxide (ZnO) humidity sensors were investigated. Experimental results show that ZnO modified with gold nanoparticles (AuNPs) or chloroauric acid (HAuCl4) enhances the concentration of oxygen vacancy defects on the surface of ZnO, which can improve the sensitivity of such a ZnO humidity sensor. As compared to AuNPs-modified ZnO, the modification of HAuCl4 reduces the size of ZnO and Au particles and exhibits better humidity performance. This is due to that smaller Au particles can further promote dissociation and electrolysis conduction processes so as to enhance the adsorption activity of HAuCl4-modified ZnO nanocomposites. Humidity experiments indicate that HAuCl4-modified ZnO acquires more than 4 orders of magnitude for the impedance changes in RH range from 11% to 95% with high sensitivity, good linearity, small hysteresis (~2.35%) and short response/recovery time (15 s/6 s). The results indicate that smaller Au particle can improve the hysteresis and response of the ZnO humidity sensor. Thus, Au particles with small size are a key parameter for the design of Au modified ZnO humidity sensors with high performance, which has a potential in the fast detection of humidity.

High-performance photoluminescence-based oxygen sensing with Pr-modified ZnO nanofibers

Praseodymium (Pr)-modified zinc oxide (ZnO) nanofibers have been fabricated using an electrospinning-calcination method. These Pr-modified ZnO nanofibers present porous morphologies containing numerous ZnO nanocrystallites with average sizes that are much smaller than those found in pure ZnO nanofibers formed by the same procedures. Most Pr is identified at the surface of / interface between the nanocrystallites. In addition to the morphological modifications, addition of Pr is also shown to enhance the crystalline quality of the ZnO. Consequently, the Pr-modified ZnO nanofibers have a higher UV emission efficiency and exhibit a much-enhanced UV emission-based O2 sensing performance than the pure ZnO nanofibers. By way of illustration, the Pr-modified nanofibers show O2 sensing responses of R = 39% at room temperature and R = 71% at 115 °C (cf. R = 19% and 52% with the pure ZnO nanofibers at these same operating temperatures). These results suggest that electrospun Pr-modified ZnO nanofibers hold real promise for high-performance optical gas sensing applications.