Bare Zinc Oxide Nanoparticles Research Articles

Fabrication of gum acacia protected zinc oxide nanoparticles for UV assisted photocatalysis of methyl green textile dye

In this communication, zinc oxide (ZnO) nanoparticles using zinc acetate as precursor, potassium hydroxide as reducing agent and natural polysaccharide (gum acacia) as capping agent is prepared to photocatalytically degrade methyl green textile dye. Surface modification of ZnO nanoparticles with gum acacia leads to change in morphology coupled with reduction in size from 31 to 16 nm. Gum acacia capped ZnO nanoparticles as photocatalyst shows greater efficiency (95%) of degrading methyl green than the bare ZnO nanoparticles (90%). Therefore, gum acacia capped zinc oxide nanoparticles could be used to treat various dye effluents from textile industries.

High Performance Dye Sensitized Solar Cells by Plasmonic Enhancement of Silver Nanoparticles in ZnO Photoelectrode with Betanin Pigment

Metal nanoparticles (NPs) introduced in sensitive places in Dye Sensitized Solar Cells (DSSCs) has demonstrated superior performance due to surface plasmon resonance effect. Herein, a systematic investigation by introducing plasmonic silver nanoparticles (AgNPs) in the photoanode of DSSCs with Zinc oxide (ZnO) is investigated. The broadening of the absorption band in the visible region is made possible using the natural pigments betanins. The combined effect of UV-visible absorption spectroscopy, XRD technique, SEM and solar simulator were used to explore the surface plasmon resonance effect. The ZnO photoanode without Ag- NPs shows a Power Conversion Efficiency (PCE) of 0.156 %, Current Density (Jsc) of 0.477 mAcm-2, Open Circuit Voltage (Voc) of 0.762 V and Fill Factor (FF) of 0.431. On coating AgNPs on the pristine photoanode, the PCEs were improved significantly as compared with the pure ZnO based device. The AgNPs were deposited in cycles (2 cycles, 4 cycles and 6 cycles). The device with 2 cycles of Ag NPs, shows a PCE of 0.373 % which demonstrates an enhancement of 2.39 times to that of the prestine device.Also depositing 4 cycles of AgNPs results to PCE of 0.290 % which shows a leading of 0.134 % ahead of the reference PCE. With 6 cycles of AgNPs deposited on the photoanode of bare ZnO NPs, it results to PCE of 0.244%, FF of 0.592, Jsc of 0.572 mAcm-2 and Voc of 0.722 V which also shows an enhancement of - 1.56 times, 1.37 times and 1.20 times in PCE, FF and Jsc over the device lacking AgNPs. These results show significant increment in performances of all the devices with silver inclusion. The performance is attributed to the reduced recombination of electron–hole pairs due to the Ag-ZnO junction and the generation of intense electric fields at the immediate vicinity of the sensitizer, resulting in enhanced light absorption.

Photocatalytic and Biological Activity of ZnO Nanoparticles Using Honey

The innovation and development of water purification methods have been at the center of extensive research for several decades. Many nanoparticles are frequently seen in industrial waste water. In this research, zinc oxide nanoparticles (ZnO) were synthesized following an autocombustion method with and without honey capping. Structural crystallinity and bonding structure were examined via X-ray diffraction (XRD) analysis and Fourier transform infrared (FTIR) spectroscopy. Optical behavior was analyzed using ultraviolet–visible (UV–Vis) spectroscopy and photoluminescence (PL). Size estimation and surface morphology were studied using scanning electron microscopy (SEM), while energy-dispersive spectroscopy (EDS) was performed to analyze the sample purity and elemental composition. The photocatalytic degradation of methylene blue (MB) by ZnO was assessed as it is an efficient water treatment process with high potential. The biological activity of ZnO nanoparticles was also investigated in terms of antibacterial and antifungal activities against different bacterial and fungal species. Surprisingly, the as-synthesized ZnO nanoparticles were found to be substantially bioactive compared to conventional drugs. Honey-mediated nanoparticles displayed 86% dye degradation efficiency, and that of bare ZnO was 60%. Therefore, the involvement of honey in the synthesis of ZnO nanoparticles has great potential due to its dual applicability in both biological and environmental remediation processes.

Synthesis and characterization of chitosan encapsulated zinc oxide (ZnO) nanocomposite and its biological assessment in pepper (Capsicum annuum) as an elicitor for in vitro tissue culture applications

Nanotechnology paves the way for introducing nanoscale fertilizers, pesticides, and elicitors. This study intends to address the synthesis of chitosan/zinc oxide nanocomposite (CS-ZnONP) and its biological assessment in in-vitro conditions. The zinc oxide nanoparticles (ZnONPs) were successfully coated with the chitosan (CS) polymer through a cost-effective approach. Transmission electron microscopy and Fourier transform infrared spectroscopy assessments proved the surface capping of chitosan polymer on ZnONP. The nanocomposite was more capable of improving growth and biomass than the bare ZnONPs. The application of the nanocomposite increased the concentration of chlorophylls (51%), carotenoids (70%), proline (2-fold), and proteins (about 2-fold). The supplementation of culture medium with the nanomaterials upregulated enzymatic antioxidant biomarkers (catalase and peroxidase). The activity of the phenylalanine ammonia-lyase enzyme also displayed a similar significant upward trend in response to the nano-supplements. The CS-ZnONP treatment considerably enhanced the accumulation of alkaloids (60.5%) and soluble phenols (40%), implying stimulation in secondary metabolism. The micropropagation test revealed that the CS-ZnONP treatment improved the organogenesis performance. Overall, the nanocomposite can be considered a highly potent biocompatible elicitor.

Hydrophobic Surface Coating Can Reduce Toxicity of Zinc Oxide Nanoparticles to the Marine Copepod Tigriopus japonicus.

Coated zinc oxide nanoparticles (ZnO-NPs) are more commonly applied in commercial products but current risk assessments mostly focus on bare ZnO-NPs. To investigate the impacts of surface coatings, this study examined acute and chronic toxicities of six chemicals, including bare ZnO-NPs, ZnO-NPs with three silane coatings of different hydrophobicity, zinc oxide bulk particles (ZnO-BKs), and zinc ions (Zn-IONs), toward a marine copepod, Tigriopus japonicus. In acute tests, bare ZnO-NPs and hydrophobic ZnO-NPs were less toxic than hydrophilic ZnO-NPs. Analyses of the copepod's antioxidant gene expression suggested that such differences were governed by hydrodynamic size and ion dissolution of the particles, which affected zinc bioaccumulation in copepods. Conversely, all test particles, except the least toxic hydrophobic ZnO-NPs, shared similar chronic toxicity as Zn-IONs because they mostly dissolved into zinc ions at low test concentrations. The metadata analysis, together with our test results, further suggested that the toxicity of coated metal-associated nanoparticles could be predicted by the hydrophobicity and density of their surface coatings. This study evidenced the influence of surface coatings on the physicochemical properties, toxicity, and toxic mechanisms of ZnO-NPs and provided insights into the toxicity prediction of coated nanoparticles from their coating properties to improve their future risk assessment and management.

Adsorptive removal of eriochrome black T (EBT) dye by using surface active low cost zinc oxide nanoparticles: A comparative overview

The ecological toxicity imparted by non-biodegradable organic dyes has been considered as a major risk to handle in front of mankind. In this view, the low-cost zinc oxide nanoparticles (ZnO-NPs) were facially synthesized by coating the surface with surfactant (CTAB) and ionic liquid (BMTF) molecules for the effective removal of Eriochrome Black T (EBT) from aqueous media. Various advanced characterization techniques have given insight into the morphological features, crystalline structure and physio-chemical properties of as-synthesized ZnO-NPs. The systematic analysis of the adsorption isotherms and kinetics models specifies that the adsorption of EBT follow Freundlich model and pseudo-second-order kinetics. The intraparticle diffusion model displayed a linear relationship (R2 = 0.98, 0.97 and 0.94 for BMTF@ZnO, CTAB@ZnO and bare ZnO-NPs), which shows that pore diffusion rate is affected by surface modification and effects the overall EBT adsorption process. Furthermore, after the removal of 87% and 84% of EBT dye by BMTF@ZnO-NPs and CTAB@ZnO-NPs, the fabricated nanoadsorbents of ZnO were successfully regenerated and reused after the treatments up to four times. The adsorption aptitude of ZnO-NPs towards EBT dye was systematically explored in real wastewater samples and interference study of inorganic metallic salts was also performed. The toxicity estimations of the treated dye solutions were made using floral and fungal activities, to ascertain their non-toxic nature before releasing into the environment. These outcomes have supported the immense potential of ZnO-NPs towards the removal of EBT in a cost effective manner.

Phytogenic fabrication of ZnO and gold decorated ZnO nanoparticles for photocatalytic degradation of Rhodamine B

Pure Zinc Oxide (ZnO) nanoparticles (NPs) and gold (Au) decorated (Au-ZnO) hetero-nanostructures were synthesized using green-synthesis method employing pecan nuts (Carya illinoinensis) leaves extract as reducing agent. The structural and optical properties studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM) and UV–vis spectrophotometer (UV–vis). Structural modification with the introduction of Au in ZnO have been confirmed by the XRD and TEM results. UV data confirmed the decrease in Au-ZnO energy band-gap Eg value, which validates the formation of hetero-structure. The modulation of energy band-gap causes visible light absorption and hence enhances the photodegradation activity of Au-ZnO. Photocatalytic activity was carried-out by degradation of RhB dye under UV light irradiation in aqueous solution. The maximum degradation of 95 % was obtained during the time of 180 min for the basic pH of the dye. The Enhanced degradation in Au-ZnO as compared with bare ZnO NPs, was attributed to Au, which controls the amount of electron and suppress electron-hole ratio at ZnO surface. In the recycling study of the Au-ZnO Photocatalyst, the hetero-structure showed good stability up to five cycles.

Surface-Modified Zinc Oxide Nanoparticles for Antialgal and Antiyeast Applications

We explored the factors and mechanisms of the antiyeast and antialgal effect of zinc oxide nanoparticles (ZnONPs) coated with zinc sulfide (ZnS), silica (SiO2), poly(sodium 4-styrenesulfonate) sodium salt (PSS), and poly(allylamine hydrochloride) (PAH) polyelectrolytes. We examined the activity of various concentrations of bare and surface modified ZnONPs toward microalgae (C. reinhardtii) and yeast (S. cerevisiae) cells upon illumination with UV light compared with that under visible light and in dark conditions to evaluate the impact of the oxidative stress due to the reactive oxygen species (ROS). We also prepared ZnS-coated ZnONPs, SiO2-coated ZnONPs, and combinations of polyelectrolyte (PSS and PAH)-coated ZnONPs and examined their antiyeast and antialgal effects. The nanoparticles of the anionic surface (ZnONPs/ZnS, ZnONPs/SiO2, and ZnONPs/PSS) showed much lower antialgal and antiyeast activity than the ones with a cationic surface functionality (ZnONPs/PSS/PAH and bare ZnONPs). The effect of the Zn...

Development of a Hybrid Chitosan- and Niacinamide-Coupled ZnO Nanoparticle Composite for Sun Protection Application

Zinc oxide nanoparticles (ZnO) have long been utilized as UV-protective sunscreen components due to their high durability and lower skin irritation while maintaining capability for blocking UV rays. However, the dispersal and transparency properties of ZnO need to be enhanced in order to improve the capacity for creating effective sunscreen through control of the physiochemical properties of ZnO. In this study, chitosan or niacinamide, which are suitable functional cosmetic compounds and effective skin lightening agents, are combined with ZnO for the development of better UV-protective products. Each biocompatible coating material is individually attached on its surface after the synthesis of ZnO. The size is 70 nm using the sol-gel method. Their morphology and chemical structure are characterized by FT-IR, XRD, SEM, TEM, TGA, and zeta potential. The results indicate that approximately 50% of chitosan and 5% niacinamide were coated on the ZnO. To confirm the capacity of each surface-coated ZnO with chitosan and niacinamide as a sunscreen, we measured their transmission, reflectance, and sun protection factor (SPF) using a UV spectrophotometer and SPF. As a result, the niacinamide-coated ZnO shows remarkably lower transmission and high reflectance against UV rays than that of bare ZnO and chitosan-coated ZnO. Furthermore, niacinamide-coated ZnO exhibits great lightening effects. Consequently, these results demonstrate that niacinamide coating is highly effective for the production of sunscreen emulsions.

Inhibition of H1N1 influenza virus infection by zinc oxide nanoparticles: another emerging application of nanomedicine

BackgroundCurrently available anti-influenza drugs are often associated with limitations such as toxicity and the appearance of drug-resistant strains. Therefore, there is a pressing need for the development of novel, safe and more efficient antiviral agents. In this study, we evaluated the antiviral activity of zinc oxide nanoparticles (ZnO-NPs) and PEGylated zinc oxide nanoparticles against H1N1 influenza virus.MethodsThe nanoparticles were characterized using the inductively coupled plasma mass spectrometry, x-ray diffraction analysis, and electron microscopy. MTT assay was applied to assess the cytotoxicity of the nanoparticles, and anti-influenza activity was determined by TCID50 and quantitative Real-Time PCR assays. To study the inhibitory impact of nanoparticles on the expression of viral antigens, an indirect immunofluorescence assay was also performed.ResultsPost-exposure of influenza virus with PEGylated ZnO-NPs and bare ZnO-NPs at the highest non-toxic concentrations could be led to 2.8 and 1.2 log10 TCID50 reduction in virus titer when compared to the virus control, respectively (P < 0.0001). At the highest non-toxic concentrations, the PEGylated and unPEGylated ZnO-NPs led to inhibition rates of 94.6% and 52.2%, respectively, which were calculated based on the viral loads. There was a substantial decrease in fluorescence emission intensity in viral-infected cell treated with PEGylated ZnO-NPs compared to the positive control.ConclusionsTaken together, our study indicated that PEGylated ZnO-NPs could be a novel, effective, and promising antiviral agent against H1N1 influenza virus infection, and future studies can be designed to explore the exact antiviral mechanism of these nanoparticles.

Mini submersible pump assisted sonochemical reactors: Large-scale synthesis of zinc oxide nanoparticles and nanoleaves for antibacterial and anti-counterfeiting applications

Low cost, environmentally friendly and industrial-scale approaches for the synthesis of anti-counterfeiting and antibacterial materials are a challenging task. The current research reports novel and inexpensive approaches for the synthesis of zinc oxide nanostructures (ZnO-NSs) using Mini Submersible Pump (MSP) assisted sonochemical reactors. Zinc oxide nanoleaves (ZnO-NLs) were synthesized using MSP assisted sonochemical mixing reactor at gram-scale (4 g). Zinc oxide nanoparticles (ZnO-NPs) were synthesized using MSP assisted sonochemical flow loop reactor at gram-scale (11.5 g). Synthesized ZnO-NSs were characterized by UV–visible spectroscopy, fluorescence spectroscopy, XRD, FTIR, TGA, BET, FEG-SEM, and FEG-TEM. Bare ZnO-NPs and ZnO-NPs coated cotton fabric showed high antibacterial activity against diseases causing Gram-positive bacteria Staphylococcus aureus. Based on the UV fluorescence property of the ZnO-NLs, invisible security ink was developed for anti-counterfeiting applications. The invisible security ink was tested as a rubber stamp and fountain pen inks which were found to be stable on the various kinds of microporous papers. As compared to our previously reported method, disperser assisted sonochemical approach for ZnO-NLs synthesis; the current approach reduces the cost of equipment used from ∼1700 to 4 USD. Both reactors are designed simply (less complicated), based on an environmentally friendly approach, highly scalable, increases the effectiveness of the sonochemical technique and suitable for industrial applications.

ZnO:SBA-15 Nanocomposites for Potential Use in Sunscreen: Preparation, Properties, Human Skin Penetration and Toxicity

Aim: We evaluated the effects of the incorporation of zinc oxide (ZnO) nanoparticles in a mesoporous matrix, aiming to improve the textural, structural and morphological properties and verify their safety so that they can be applied in sunscreen cosmetics. Materials and Methods: ZnO nano­particles were incorporated into an ordered mesoporous silica matrix known as Santa Barbara Amorphous-15 (SBA-15), using post-synthesis methodology. The resulting nanocomposites were characterized using X-ray diffraction, small angle X-ray scattering, N₂ adsorption-desorption isotherms, Fourier transform infrared spectroscopy, scanning electron microscopy and predicted in vitro sun protector factor (SPF) estimation. Effectiveness and safety were evaluated by antimicrobial activity, in vitro cell toxicity and non-invasive multi-photon tomography with fluorescence lifetime imaging. Results: The structure of the nanocomposites was similar to that of SBA-15, with little perturbation caused by ZnO incorporation. Nanocomposites had an increased in vitro SPF, reduced cytotoxic activity and favourable antimicrobial properties compared to ZnO. ZnO:SBA-15 nanocomposites exhibited no measurable toxicity when applied to human skin in vivo. Conclusion: Due to their suitable physicochemical properties and improved safety compared to bare ZnO nanoparticles, the ZnO:SBA-15 nanocomposites show promise for use in cosmetic applications.

Fabrication and Characterization of Cysteine-Functionalized Zinc Oxide Nanoparticles for Enzyme Immobilization

ABSTRACTA green approach is reported for the synthesis of cysteine-functionalized zinc oxide nanoparticles using potato extract as a nontoxic and economical reducing agent. The cysteine-functionalized nanoparticles were used as a support for enzyme immobilization. The structural morphology, crystallinity, and surface functionalization were characterized by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy, respectively. Spherical nanoparticles from 150 to 200 nm were used to evaluate the immobilization efficiency for urease through covalent attachment on the glutaraldehyde-activated amino group of cysteine. In comparison to the unmodified nanoparticles, 62.9% enzyme loading with 72.45% of enzyme specific activity was recovered which was 56% higher than on bare zinc oxide nanoparticles. The point of addition of cysteine during the nanoparticle synthesis had a direct effect on the immobilization efficiency. The immobilized enzyme-specific activity was reduced to 34.32% when cysteine was added following the nanoparticle synthesis. With a facile synthesis procedure and significant immobilization efficiency, cysteine-functionalized zinc oxide nanoparticles were shown to be suitable for various clinical and industrial applications.

Differential Toxicity of Bare and Hybrid ZnO Nanoparticles in Green Pea (Pisum sativum L.): A Life Cycle Study.

The effect of surface or lattice modification of nanoparticles (NPs) on terrestrial plants is poorly understood. We investigated the impact of different zinc oxide (ZnO) NPs on green pea (Pisum sativum L.), one of the highest consumed legumes globally. Pea plants were grown for 65 d in soil amended with commercially available bare ZnO NPs (10 nm), 2 wt% alumina doped (Al2O3@ZnO NPs, 15 nm), or 1 wt% aminopropyltriethoxysilane coated NPs (KH550@ZnO NP, 20 nm) at 250 and 1000 mg NP/kg soil inside a greenhouse. Bulk (ZnO) and ionic Zn (zinc chloride) were included as controls. Plant fresh and dry biomass, changes in leaf pigment concentrations, elements (Zn, Al, Si), and protein and carbohydrate profile of green pees were quantified upon harvest at 65 days. With the exception of the coated 1000 mg/kg NP treatment, fresh and dry weight were unaffected by Zn exposure. Although, all treated plants showed higher tissue Zn than controls, those exposed to Al2O3@ZnO NPs at 1000 mg/kg had greater Zn concentration in roots and seeds, compared to bulk Zn and the other NP treatments, keeping Al and Si uptake largely unaffected. Higher Zn accumulation in green pea seeds were resulted in coated ZnO at 250 mg/kg treatments. In leaves, Al2O3@ZnO NP at 250 mg/kg significantly increased Chl-a and carotenoid concentrations relative to the bulk, ionic, and the other NP treatments. The protein and carbohydrate profiles remained largely unaltered across all treatments with the exception of Al2O3@ZnO NPs at 1000 mg/kg where sucrose concentration of green peas increased significantly, which is likely a biomarker of stress. Importantly, these findings demonstrate that lattice and surface modification can significantly alter the fate and phytotoxic effects of ZnO NPs in food crops and seed nutritional quality. To the authors' knowledge, this is the first report of a life cycle study on comparative toxicity of bare, coated, and doped ZnO NPs on a soil-grown food crop.

The influence of biofilms on the mobility of bare and capped zinc oxide nanoparticles in saturated sand and glass beads

Biofilms are a common constituent of the subsurface and are known to influence contaminant transport; however only a few studies to date have addressed microbial controls on nanoparticle mobility in porous media. The impact of a 3-day Pantoea agglomerans biofilm on the mobility of zinc oxide (ZnO) nanoparticles was studied in column experiments containing sand and glass beads at near-neutral pH and constant ionic strength. Bare ZnO nanoparticles (bZnO-NPs) and ZnO nanoparticles capped with tri-aminopropyltriethoxysilane (cZnO-NPs) were used in the experiments. Breakthrough curves demonstrate that the biofilm particularly slowed nanoparticle migration of bZnO-NPs in glass bead columns and cZnO-NPs in sand columns. With the exception of bZnO-NPs in sand columns, biofilm-coated porous media retained more nanoparticles than those of controls without biofilm. The biofilm may bear an impact on the surface charge of the porous medium, nullifying porous medium-specific effects. Although viable cell counts (VCCs) decreased after the introduction of electrolyte and before nanoparticle transport experiments, SEM and CLSM imaging of porous medium samples taken from columns after nanoparticle transport experiments, as well as total organic carbon (TOC) measurements reveal that biofilm was present in the columns throughout the experiments. Hence, it can be concluded that even a thin amount of biofilm can hinder nanoparticle migration in small-scale porous medium experiments. Moreover, nanoparticle mobility is dependent on the binding capacity of biofilms, rather than the type of porous media.

Zinc oxide: Conjugated polymer nanocomposite as cathode buffer layer for solution processed inverted organic solar cells

Cathode buffer layer (CBL) is one of the key issues influencing the performance of organic solar cells. In this article, a nanocomposite of zinc oxide nanoparticles (ZnO) together with a conjugated polymer, poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl)-fluorene] (PFN) was developed, and used as the CBL for solution processed inverted organic solar cells (OSC). In comparison with the bare ZnO, PFN or ZnO/PFN stacked layer, the ZnO:PFN nanocomposite CBL employing device showed superior device performance, in particular significantly improved fill factor. Optimized power conversion efficiency (PCE) of P3HT:PC61BM and PTB7:PC61BM device using ZnO:PFN composite CBLs reached to 3.56% and 7.17%, respectively. Influences of the mixing ratio and the layer thickness of the ZnO:PFN nanocomposite CBL on solar cell performance were carefully studied, and results indicated that ZnO:PFN CBL showed a wide tolerance of blend ratio and layer thickness. In particular, no obvious thickness dependent-device performance was found, even when the CBL layer thickness was higher than 125nm, providing a good printing processibility of the nanocomposite. Photoelectron spectroscopy, photoluminescence, as well as electric conductivity of the ZnO:PFN films were studied, and the results were compared with that of the other three reference CBLs. Results demonstrated that the interaction between ZnO and PFN decreases the work function of the blended film, leading to a more favorable energy level alignment for electron injection at the interface. Analysis on the dark J–V curves of the solar cells revealed that device using ZnO:PFN CBL had the best diode characteristics including lowest reverse saturated current density (J0), ideal factor (n), and series resistance (Rs), and highest shunt resistance (Rsh). Such an improvement was ascribed to the defect passivation by the conjugated polymer, which led to an improved charge carrier selectivity of the CBL and consequently enhanced the FF of the solar cells. In addition, long-term stability of organic solar cells was also improved by using ZnO:PFN nanocomposite as the CBL. The current work provides a valuable guideline for the development of high performance cathode buffer layer material for printable organic solar cells.

Enhanced UV-detection properties of carbon nanotube impregnated ZnO nanourchins

The bare and carbon nanotube (CNT) impregnated zinc oxide (ZnO) nano-urchins were synthesized by chemical precipitation process from a super-saturated zinc nitrate bath. The synthesized samples were characterized by scanning electron microscopy, X-ray diffractometry and Raman spectroscopy. Ultra-violet photo-detection properties of the nanostructures were studied and compared with commercial ZnO nanopowder by fabricating a metal–semiconductor–metal (MSM) array in a purpose built apparatus. Although the different applied seed for chemical precipitation (ZnO nanoparticles and Carbon nanotube) yielded same nano-urchin morphology, the size of the needles of CNT impregnated ZnO nanourchin was substantially bigger than that of bare ZnO nanourchin. By incorporation of CNTs, the fast electron/hole recombination and slow electrons mobility of the bare ZnO nanoparticles was improved and consequently led to the stronger UV detecting performance (up to 34 times photosensitivity, photoresponsivity of 2.1A/W, signal to noise of 47.29dB in time of response of 16s) which proposed it as a worthwhile choice for practical applications.

Role of surface modification in zinc oxide nanoparticles and its toxicity assessment toward human dermal fibroblast cells.

The wide-scale applications of zinc oxide (ZnO) nanoparticles (NPs) in photocatalysts, gas sensors, and cosmetics may cause toxicity to humans and environments. Therefore, the aim of the present study was to reduce the toxicity of ZnO NPs by coating them with a silica (SiO2) layer, which could be used in human applications, such as cosmetic preparations. The sol–gel method was used to synthesize core ZnO with SiO2-shelled NPs (SiO2/ZnO NPs) with varying degrees of coating. Diverse studies were performed to analyze the toxicity of NPs against cells in a dose- and time-dependent manner. To ensure the decreased toxicity of the produced SiO2/ZnO NPs, cytotoxicity in membrane damage and/or intracellular reactive oxygen species (ROS) were assessed by employing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, lactate dehydrogenase, 2′,7′-dichlorofluorescin, and lipid peroxide estimations. The cores of ZnO NPs exhibited cytotoxicity over time, regardless of shell thickness. Nevertheless, the thicker SiO2/ZnO NPs revealed reduced enzyme leakage, decreased peroxide production, and less oxidative stress than their bare ZnO NPs or thinner SiO2/ZnO NPs. Therefore, thicker SiO2/ZnO NPs moderated the toxicity of ZnO NPs by restricting free radical formation and the release of zinc ions, and decreasing surface contact with cells.

Transport of bare and capped zinc oxide nanoparticles is dependent on porous medium composition

Zinc oxide (ZnO) nanoparticles are one of the most frequently used nanoparticles in industry and hence are likely to be introduced to the groundwater environment. The mobility of these nanoparticles in different aquifer materials has not been assessed. While some studies have been published on the transport of ZnO nanoparticles in individual porous media, these studies do not generally account for varying porous medium composition both within and between aquifers. As a first step towards understanding the impact of this variability, this paper compares the transport of bare ZnO nanoparticles (bZnO-NPs) and capped ZnO nanoparticles, coated with tri-aminopropyltriethoxysilane (cZnO-NPs), in saturated columns packed with glass beads, fine grained sand and fine grained calcite, at near-neutral pH and groundwater salinity levels. With the exception of cZnO-NPs in sand columns, ZnO nanoparticles are highly immobile in all three types of studied porous media, with most retention taking place near the column inlet. Results are in general agreement with DLVO theory, and the deviation in experiments with cZnO-NPs flowing through columns packed with sand is linked to variability in zeta potential of the capped nanoparticles and sand grains. Therefore, differences in surface charge of nanoparticles and porous media are demonstrated to be key drivers in nanoparticle transport.

Different strategies for the synthesis of graphene/ZnO composite and its photocatalytic properties

Owing to its unique physical and chemical properties, graphene has attracted tremendous attention in the preparation of graphene-based composites for various applications. In this study, two different strategies have been developed to load zinc oxide (ZnO) nanorods onto reduced graphene oxide (RGO) sheets, i.e., in situ growth and a self-assembly approach. The microstructure and morphology of the synthesized RGO/ZnO nanocomposites was investigated by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET) measurements. Fluorescence emission spectra (PL) of RGO/ZnO composites were performed to attribute quality of combination between RGO and ZnO. Significantly enhanced photocatalytic activity of RGO/ZnO nanocomposites in comparison to bare ZnO nanoparticles was revealed by the degradation of methylene blue under irradiation, which can be attributed to the inhibition of electron–hole pair recombination and enhanced adsorption due to the presence of RGO sheets.