ZnO NSs Research Articles

Integration of mesoporous ZnO and Au@ZnO nanospheres into sensing device for the ultrasensitive CH3COCH3 detection down to ppb levels

Surface modification of metal oxide nanostructures with noble metals has attracted significant attention of researchers because of their importance in gas sensing applications. In this regard, mesoporous zinc oxide nanospheres (ZnO NSs) were designed through a simple template-free solvothermal approach and successive anchoring of gold nanoparticles (Au NPs) onto it was achieved through a chemical process followed by thermal treatment. The synergistic effects of different Au NPs loadings onto the structure, surface morphology, element contents, as well as chemiresistive gas sensing activities of solvothermal-mediated ZnO NSs were examined thoroughly and discussed. Gas sensing studies demonstrated that the sensor based on Au@ZnO-3 NSs exhibits excellent acetone (CH3COCH3) sensing characteristics (Response = 194) compared to pristine ZnO NSs sensor (Response = 2.86) at a lower temperature of 170 °C. Besides, Au@ZnO NSs sensor is able to detect CH3COCH3 concentration down to ppb-levels (500 ppb) with excellent response repeatability. Observed CH3COCH3 sensing performances of all the Au loaded ZnO NSs sensors were found to be almost 50 times higher than pristine ZnO NSs sensor. Such an excellent CH3COCH3 sensing performance of Au@ZnO NSs is mainly credited to the catalytic activity of Au NPs and the strong metal-semiconductor contacts between Au NPs and ZnO NSs.

Decorating spherical In2O3 nanoparticles onto ZnO nanosheets for outstanding gas-sensing performances

The presence and detection of hazardous environmental gases at deficient concentrations are essential to protect human beings from intensive gas exposures. Therefore, the development of high-response gas sensors is vital to overcome these overwhelming issues. The spherical In2O3 nanoparticles are successfully decorated onto ZnO nanosheets in ZnO@In2O3 (ZIO) nanocomposites via a simple co-precipitation method. The as-prepared nanocomposites are exposed to gas-sensing applications. The fabricated gas sensors exhibit high sensing response and selectivity towards NO2 gas than other gases, tested at various working temperatures and different range of gas concentrations. The gas-sensing property of ZnO nanosheets and ZIO nanocomposites has been investigated, which reveals that 10 wt% ZIO nanocomposites shows the outstanding response of 68 at 70 ppm (1.88% higher than pristine ZnO NSs), possesses fast response/recovery time (43, 65 s) respectively, and demonstrates excellent stability and repeatability. A plausible nanostructure formation and gas-sensing mechanism are also discussed in detail. The fabricated sensors are considered potential applicants in the development of the NO2-based gas sensor industry.

Fast Detection and Flexible Microfluidic pH Sensors Based on Al-Doped ZnO Nanosheets with a Novel Morphology.

In this study, a flexible and stable pH sensor based on aluminum-doped zinc oxide nanosheets (Al-doped ZnO NSs) was developed by a low-cost hydrothermal method. The results obtained from this study indicated that Al ions could be doped successfully into the ZnO nanostructure, which could change the morphology and improve the pH-sensing properties. The pH sensitivity of Al-doped ZnO nanosheets reached 50.2 mV/pH with a correlation coefficient of around 0.99468 when compared with that of ZnO film (34.13 mV/pH) and pure ZnO nanowires (45.89 mV/pH). The test range of pH values was widened by Al-doping, and the Al-doped ZnO NS sensor could detect the pH value ranging from 2 to 12. It was observed that in a more acidic environment, especially at pH 2, the sensor, Al-doped ZnO nanosheet, was strongly stable over 12 weeks of testing. It was noted that the response time was utterly fast and the response time of the sensors for each pH standard buffer solutions was around 0.3 s. Thus, the response time and performance were quite stable. The microchannel provided a novel testing method for the pH sensor, where the liquid to be tested was just 5 mL. Hence, it was suggested to be useful for many medical diagnoses and treatments. The benefits of Al-doped ZnO nanosheet pH sensor were high sensitivity, good long-term usage, good flexible property, and requirement of a small amount of test liquid, which could make the sensors viable candidates for practical applications.

Characterization of Zinc oxide Nanostructures prepared by hydrothermal method with Antibacterial property

In this study, Zinc oxide nanostructures were synthesized via a hydrothermal method by using zinc nitrate hexahydrate and sodium hydroxide as a precursor. Three different annealing temperatures were used to study their effect on ZnO NSs properties. The synthesized nanostructure was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Atomic force microscope (AFM), and Fourier Transform Infrared Spectroscopy (FTIR). Their optical properties were studied by using UV -visible spectroscopy. The XRD analysis confirms that all ZnO nanostructures have the hexagonal wurtzite structure with average crystallite size within the range of (30.59 - 34.52) nm. The crystallite size increased due to the incensement of annealing temperature. FESEM analysis indicates that ZnO has hexagonal shape of cylindrical pores, plate-like nanocrystals and Nanorods. AFM analysis shows that the average surface roughness of ZnO Nanostructures increases from 3.96 to 19.1 nm with the increase of annealing temperature. The FTIR peaks indicate successful preparation of ZnO Nanostructures. The FTIR method was used to analyses the chemical bonds which conformed the present of the Zn-O group in the region between (400-500) cm-1. The UV-visible showed a red shift in the absorption spectra related to the shift in the energy gap related to increase in the particle size. the band gap energy has been calculated from the optical absorption spectra. The annealing process has been fond more effective on the value of energy gap. As the annealing temperature increases, the value of energy gap, increases as well; from (3.12to 3.22) eV. The prepared Nanostructure is used for antibacterial property. It shows strong antibacterial activity against S. aureus and P.aeuruginosa bacteria by the agar disc diffusion method. The white precipitate of ZnO NSs has superior antibacterial activity on gram-positive (S. aureus) than the gram-negative (P.aeuruginosa) bacteria.

Tunable synthesis of pH-responsive biodegradable ZnO nanospheres assembled from ultrasmall particles for cancer chemotherapy

The biodegradable nanoparticles hold tremendous potential in the field of nanomedicine because of the negligible toxicity concerns in healthy tissues/organs. We reported a simple route for the synthesis of pH-responsive biodegradable ZnO nanospheres (ZnO NSs) assembled from ultrasmall particles (sizes ranging from 4 to 8 nm, average 6 nm) with a suitable size. The nanoplatform could be responsively decomposed into small fragments under the weak acid environment to meet the requirement for pH-stimulus drug release and in favor of the biodegradation. The confocal laser scanning microscopy (CLSM) studies showed that the ZnO NSs could be efficiently internalized by cancer cells, and the loaded doxorubicin (DOX) in the NSs could be successfully released under acidic intracellular environment. Notably, the cell viabilities of DOX-loaded NSs with different sizes towards HepG-2 and HeLa cells for different incubation time were investigated, which exhibited dose-dependent and time-dependent effects. Furthermore, in vivo experiments showed that the DOX-loaded NSs displayed a significant antitumor effect (79% average inhibition rate relative to the control group) without distinct side effects. All in all the designed NSs as drug delivery systems not only achieved the excellent cancer chemotherapy but also could be rapidly decomposed or metabolized to reduce their toxicity.

Improving Field Electron Emission Properties of ZnO Nanosheets with Ag Nanoparticles Adsorbed by Photochemical Method.

Zinc oxide is a low cost and practical II–VI chemical material, which is utilized to absorb silver (Ag) nanoparticles (NPs) on zinc oxide nanosheets (ZnO NSs). Using the Ag NP-decorated ZnO NSs can improve the electrical characteristics of zinc oxide. Field electron emission characteristics of ZnO NSs and Ag–ZnO NSs indicate the turn-on fields were 5.3 and 3.2 V/μm in the dark, whereas the turn-on field were 4.3 and 2 V/μm under UV light, respectively. In addition, the field electron emission characteristics of ZnO NSs and Ag–ZnO NSs indicate the enhanced field enhancement factors were 3002 and 3420 in the dark and 3276 and 4815 under UV light, respectively.

High-Efficiency Dye-Sensitized Solar Cells Based on a ZnO Nanorod/ Nanosheet Hierarchical Structure

Aqueous solution of Zn(NO₃)₂*6H₂O-C₆H₂N₄-PEI and Zn(NO₃)₂*6H₂O-CO(NH₂)₂ were used as raw materials to fabricate hierarchically structured films of ZnO nanorods/nanosheets (ZnO NRs/NSs) via a two-step hydrothermal synthesis, and the films of ZnO NRs/NSs were applied as photoanodes for application in dye-sensitized solar cells (DSSCs). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were utilized to characterize the morphologies of the ZnO films. The current density-voltage curves and the incident monochromatic photon-to-electron conversion efficiency of DSSCs were measured. Through electrochemical impedance spectroscopy, intensity modulated photovoltage spectroscopy , and intensity modulated photocurrent spectroscopy, the conditions of the internal electron transport and transfer of ZnO-based DSSCs were tested and analyzed. The results indicate that the ZnO NRs/NSs photoanodes not only have properties of rapid electron transport and high electron collection efficiency but also show a relatively large amount of dye absorption. Therefore, for DSSCs based on ZnO NRs/NSs, the short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoelectric conversion efficiency (PCE) were 11.82 mA cm-2, 0.66 V, 0.58, and 4.59%, respectively. The PCE of the DSSCs was improved by 178.18% with respect to that of pure ZnO NRs cells (1.65%) and was improved by 21.42% with respect to the pure ZnO NSs cells (3.78%).

Facile synthesis of ZnO nanosheets: Structural, antibacterial and photocatalytic studies

Two dimensional (2D) hexagonal sheet-like Zinc Oxide nanostructures (ZnO NSs) have been synthesized by Sodium Dodecyl Sulphate (SDS)-assisted atmospheric microplasma electrochemical technique at room temperature. The synthesized nanostructures were investigated by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), UV–Visible spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. The viable formation mechanism of sheet-like ZnO NSs has been proposed. XRD pattern confirmed the ZnO NSs of fine crystallinity with hexagonal phase. Rietveld refinement of XRD patterns provides accurate values for the lattice parameters. The sharp UV absorption peak at 363 nm suggested the synthesis of high-quality crystalline ZnO NSs. These NSs also showed significant antibacterial activities against various bacterial strains. In addition, ZnO NSs displayed excellent Photocatalytic activity in the degradation of Rhodamine B (Rhd B) dye in aqueous solution.

Synergistic effect of low and high intensity ultrasonic irradiation on the direct growth of ZnO nanostructures on the galvanized steel surface: investigation of the corrosion behavior

Considering the current interest in the preparation of modified surfaces with fixed nanostructures, in this research, the hot water treatment was chosen as a simple and efficient procedure for the direct growth of ZnO nanostructures (ZnO NSs) on the metallic surface. To improve the method and reduce the cost of experiments, the commercial galvanized steel (steel containing a thin layer of zinc) was used as the base substrate. The use of the galvanized steel as an inexpensive and available metal surface has advantages compared to the pure Zn foil (used in other researches). In addition, in the present work, the effective pretreatment of the base substrate surface by applying the chemical etching under the low intensity ultrasonic irradiation facilitated the reaction progress (Zn → ZnO) in a shorter time and relatively low temperature in comparison to many reports. To find the effect of acoustic energy on the final ZnO morphology, the hot water treatment was carried out under conventional and sonochemical conditions. Finally, as a practical application, resulting surfaces were coated with electroless Ni-P deposits and the effect of as-grown ZnO NSs (as the sublayer) on improvement in the corrosion protection of binary Ni-P deposits was evaluated by the electrochemical method.

Antibiofilm activity of zinc oxide nanosheets (ZnO NSs) using Nocardiopsis sp. GRG1 (KT235640) against MDR strains of gram negative Proteus mirabilis and Escherichia coli

Activity of zinc oxide nanosheets (ZnO NS) synthesized using actinomycetes of Nocardiopsis sp. GRG1 (KT235640) was analyzed for anti-biofilm activity against multidrug resistant (MDR) strains of Proteus mirabilis BDUMS1 (KY617768) and Escherichia coli BDUMS3 (KY617770) uropathogens. Characterization of synthesized ZnO NSs was done using scanning electron microscopy (SEM), UV–vis absorption spectrum, fourier transform infrared (FTIR), X-ray diffraction (XRD) pattern, raman spectrum, and energy-dispersive X-ray spectroscopy (EDS). Biofilm formation was evaluated by tissue culture plate method (TCP) and congo red agar assay (CRA). It was observed that the synthesized ZnO NSs showed significant antibacterial activity against the selected MDR strains. Further, these synthesized ZnO NSs holds the capability to deliver antibiofilm activity against MDR strains such as P. mirabilis BDUMS1 (KY617768) and E. coli BDUMS3 (KY617770).

Surfactant assisted synthesis of ZnO nanostructures using atmospheric pressure microplasma electrochemical process with antibacterial applications

In this study, surfactant assisted synthesis of zinc oxide nanostructures (ZnO NSs) by facile atmospheric microplasma electrochemical processes at room temperature have been reported. We have investigated the effect of ionic surfactants and nonionic fructose on the morphology of synthesized samples and their antibacterial activity against various bacterial pathogens. The samples were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), Photoluminescence (PL) spectroscopy and Fourier Transform infrared (FTIR) Spectroscopy. We obtained nanosheets, nanodrums and nanoneedles using different type of surfactants. XRD spectra indicated ZnO nanomaterial with hexagonal phase. The antibacterial activity of the as synthesized samples against various bacteria of clinical interests was carried out by diffusion well method. The results showed the significant antibacterial activity against all bacterial strains. Thus, ZnO nanomaterial exhibited potential application as a bacteriostatic agent in the visible light and could be developed as antibacterial agent to control and prevent the spreading of bacterial infections.

Photonic sintering of a ZnO nanosheet photoanode using flash white light combined with deep UV irradiation for dye-sensitized solar cells

The present report details research work on the photonic sintering of ZnO nanosheets (ZnO NSs), which were synthesized via a solid-state synthesis method.

Flexible Organic/Inorganic Hybrid Field-Effect Transistors with High Performance and Operational Stability.

The production of high-quality semiconducting nanostructures with optimized electrical, optical, and electromechanical properties is important for the advancement of next-generation technologies. In this context, we herein report on highly obliquely aligned single-crystalline zinc oxide nanosheets (ZnO NSs) grown via the vapor-liquid-solid approach using r-plane (01-12) sapphire as the template surface. The high structural and optical quality of as-grown ZnO NSs has been confirmed using high-resolution transmission electron microscopy and temperature-dependent photoluminescence, respectively. To assess the potential of our NSs as effective building materials in high-performance flexible electronics, we fabricate organic (parylene C)/inorganic (ZnO NS) hybrid field-effect transistor (FET) devices on flexible substrates using room-temperature assembly processes. Extraction of key FET performance parameters suggests that as-grown ZnO NSs can successfully function as excellent n-type semiconducting modules. Such devices are found to consistently show very high on-state currents (Ion) > 40 μA, high field-effect mobility (μeff) > 200 cm2/(V s), exceptionally high on/off current modulation ratio (Ion/off) of around 109, steep subthreshold swing (s-s) < 200 mV/decade, very low hysteresis, and negligible threshold voltage shifts with prolonged electrical stressing (up to 340 min). The present study delivers a concept of integrating high-quality ZnO NS as active semiconducting elements in flexible electronic circuits.

Chlorobenzene sensor based on Pt-decorated porous single-crystalline ZnO nanosheets

Detection of chlorobenzene is a challenge for metal oxide gas sensors because of its stable molecule structure. In this work, Pt-decorated porous single-crystalline ZnO nanosheets (PSC ZnO NSs) were successfully synthesized via a one-pot hydrothermal method followed by a liquid phase reduction process. The morphology and structure of the as-prepared sample were well characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive spectrum (EDS) and ICP-MS analysis. From gas-sensing test, it can be found that the decoration of Pt nanoparticles largely enhanced the sensing performance of the PSC ZnO NSs. The Pt-decorated PSC ZnO NSs showed good response to low concentrations of chlorobenzene from 10 to 500ppb. In contrast, the Au and Ag-decorated PSC ZnO NSs had still no response to 500ppb of chlorobenzene. The enhancement sensing mechanism of Pt nanoparticle decoration has also been discussed in detail.

Effect of Electric Field and Temperature in Electrochemical Dissolution and Deposition Process on Morphologies of ZnO Nanostructures

Zinc oxide nanostructures were synthesized by an electrochemical dissolution and deposition process. The zinc plates were immerged in deionized water and used as two electrodes. The process was operated by applying the electric field of 10, 12.5, 25 and 50 V/cm, the constant voltage of 10 V and varied the temperatures from room temperature to 70 °C during 1 h. It was found that the electric field and temperature of electrolyte solution had affected to morphologies of ZnO NSs and were grown in forms of nanoflakes, nanoparticles and nanorods.

Fabrication of highly sensitive uric acid biosensor based on directly grown ZnO nanosheets on electrode surface

Here we report the direct synthesis of ZnO nanosheets (ZnO NSs) on the electrode surface by one step low temperature solution process and characterized in detail using various techniques. The directly grown ZnO NSs used for fabrication of uric acid biosensor (Nafion/Uricase/ZnO NSs/Ag/Si) and performance of fabricated has been examined for uric acid detection. This biosensor showed high sensitivity of 129.81μAcm−2mM−1 in wide-linear range (0.05–2.0mM) with high correlation coefficient of R2=0.9993. A rapid response time of ∼5s, low detection limit of 0.019μM (based on S/N ratio) and lower value of apparent Michaelis–Menten constant (Kmapp) of 0.026mM was calculated for the fabricated biosensor. The lower value of Kmapp shows a high affinity between the uric acid and uricase immobilized on ZnO NSs. The anti-interference ability, reproducibility and long-term storage stability of biosensor were examined. These results suggests that our fabricated biosensors are highly reproducible, selective and stable for favorable determination of uric acid and can be effectively used for application in real samples with good precision and accuracy.

Detection of trivalent-iron based on low-dimensional semiconductor metal oxide nanostructures for environmental remediation by ICP-OES technique

A large-scale synthesis of undoped low-dimensional semiconductor metal oxide nanostructures (ZnO nanoparticles, NPs) by simple wet-chemical method was performed using reducing agents at low temperature. The NPs were characterized in terms of their morphological, structural, and optical properties, and efficiently applied for the metal ions uptake. The detailed structural, compositional, and optical characterizations of the NPs were evaluated by powder X-ray diffraction pattern (XRD), Fourier-transform infra-red spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Electron dispersion spectroscopy (EDS), and UV–vis. spectroscopy, respectively which confirmed that the obtained NPs are well-crystalline undoped ZnO and possessed good optical properties. The ZnO NSs morphology was investigated by FESEM, which confirmed that the calcined materials were spherical shape in nano-level and growth in huge-quantity. The analytical efficiency of newly synthesized ZnO NPs was also investigated for a selective separation of trivalent iron [Fe(III)] prior to its determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of ZnO NPs towards different metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ni(II), Zn(II), and Zr(IV), was studied. Data obtained from the selectivity study suggested that that ZnO NPs phase was the most selective towards Fe(III). The static uptake capacity of Fe(III) was found to be ~79.80mgg−1. Moreover, adsorption isotherm data also provided that the adsorption process was mainly monolayer on a homogeneous adsorbent surface.

Synthesis and investigation of Indium doping and surfactant on the morphological, optical and UV/Vis photocatalytic properties of ZnO nanostructure

ZnO and Indium doped ZnO nanostructures with different morphologies have been synthesized by mild solvothermal method in the presence of cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS) and Tritron X-100 as cationic, anionic and nonionic surfactants, respectively. The hydrothermal growth mechanism was influenced by Indium impurity and surfactant. Hexagonal, flower, polyhedral and nearly spherical morphologies of ZnO were obtained. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) methods. The role of surfactant charge on the ZnO growth orientation was investigated and related mechanism discussed. The highest degradation rate constant was observed for In doped flower-like ZnO synthesized using CTAB. The effects of In doping and surfactant charge on the structure, morphology, optical properties and photocatalytic activity (PCA) of ZnO nanostructures were investigated and discussed in detail. Obtained results can be utilized in the synthesis of ZnO NSs with desired growth orientation and consequently enhanced properties.

Synthesis of Graphene-ZnO-Au Nanocomposites for Efficient Photocatalytic Reduction of Nitrobenzene

A simple hydrothermal method of preparing highly photocatalytic graphene-ZnO-Au nanocomposites (G-ZnO-Au NCs) has been developed. Zinc acetate and graphene oxide are reduced by catechin to form graphene-zinc oxide nanospheres (G-ZnO NSs; average diameter of (45.3 ± 3.7) nm) in the presence of ethylenediamine (EDA) as a stabilizing agent and gold nanorods (Au NRs) at 300 °C for 2 h. Then Au NRs are deposited onto as-formed G-ZnO NSs to form G-ZnO-Au NCs. Upon ultraviolet light activation, G-ZnO-Au NCs (4 mg mL(-1)) in methanol generates electron-hole pairs. Methanol (hydroxyl group) assists in trapping holes, enabling photogenerated electrons to catalyze reduction of nitrobenzene (NB) to aniline with a yield of 97.8% during a reaction course of 140 min. The efficiency of G-ZnO-Au NCs is 3.5- and 4.5-fold higher than those provided by commercial TiO2 and ZnO NSs, respectively. Surface assisted laser desorption/ionization mass spectrometry has been for the first time applied to detect the intermediates (nitrosobenzene and phenylhydroxylamine) and major product (aniline) of NB through photoelectrocatalytic or photocatalytic reactions. The result reveals that the reduction of NB to aniline is through nitrosobenzene to phenylhydroxylamine in the photoelectrocatalytic reaction, while via nitrosobenzene directly in the photocatalytic reaction. G-ZnO-Au NC photocatalyst holds great potential in removal of organic pollutants like NB and in the production of aniline.

Photovoltaic Performance of ZnO Nanosheets Solar Cell Sensitized with Beta-Substituted Porphyrin

The photoanode of dye-sensitized solar cell (DSSC) was fabricated using two-dimensional ZnO nanosheets (2D ZnO NSs) sensitized with beta-substituted porphyrins photosensitizer, and its photovoltaic performance in solid-state DSSC with TiO2nanotubes (TiO2TNs) modified poly (ethylene oxide) (PEO) polymer electrolyte was studied. The ZnO NSs were synthesized through hydrothermal method and were characterized through high-resolution scanning electron microscopy (HRSEM), diffused reflectance spectra (DRS), photoluminescence spectra (PL), and X-ray diffraction (XRD) analysis. The crystallinity of the polymer electrolytes was investigated using X-ray diffraction analysis. The photovoltaic performance of the beta-substituted porphyrins sensitized solar cells was evaluated under standard AM1.5G simulated illumination (100 mW cm−2). The efficiency of energy conversion from solar to electrical due to 2D ZnO NSs based DSSCs is 0.13%, which is about 1.6 times higher than that of the control DSSC using ZnO nanoparticles (ZnO NPs) as photoanode (0.08%), when TiO2NTs fillers modified PEO electrolyte was incorporated in the DSSCs. The current-voltage () and photocurrent-time () curves proved stable with effective collection of electrons, when the 2D ZnO nanostructured photoanode was introduced in the solid-state DSSC.