Source Of Zinc Ions Research Articles

Hierarchical ZnO Nanomaterials with Superior Photocatalytic Properties

A well-controlled multistage hydrothermal technique was developed to synthesise hierarchical zinc oxide (ZnO) nanomaterials with a high surface-to-volume ratio. Hierarchical ZnO nanomaterials, hierarchical nanowires (HNWs) and hierarchical nanodiscs (HNDs), assembled from initial mono-morphological nanomaterials, ZnO nanowires, and ZnO nanodiscs respectively were prepared by sequential nucleation and growth following a hydrothermal course. The hierarchical nanomaterials composed of one-dimensional nanowire building blocks were obtained by introducing zinc nitrate as a source of zinc ions during the second growth phase. In comparison to their initial monomorphological counterparts, the prepared HNWs and HNDs showed superior photocatalytic performances. The improvement in the photocatalytic performance was ascribed to the reduction in dimensionality, the ultrahigh surface-to-volume ratio, the expanded proportion of the exposed polar area, and the creation of nanojunctions between the secondary nanowires and initial ZnO nanowires or nanodiscs. This work paves the way for the low-cost, large-scale, and low-temperature production of ZnO nanomaterials with superior photocatalytic properties.

Hierarchical zinc oxide nanobrushes ultraviolet photodetector

In order to synthesise hierarchical zinc oxide (ZnO) nanomaterials with a high surface-to-volume ratio, a well-controlled multistage hydrothermal method was developed. Hierarchical ZnO nanobrushes (ZNBs) built from initial mono-morphological nanomaterials, ZnO nanowires (ZNWs), and ZnO nanoplates (ZNPs) were developed using sequential nucleation and growth following a hydrothermal process. Hierarchical nanomaterials which are comprised of one-dimensional (1D) nanowire building blocks were obtained via a zinc ion source (zinc nitrate) during the second growth phase. In comparison to their first mono-morphological equivalents, the hierarchical nanomaterials which were grown showed improved ultraviolet (UV) detection, as well as improved sensitivity (∼104), an ultra-fast response time (235 ms), and a good recovery time (310 ms). Improvements to the response and recovery times were a result of distinct nanojunction barrier-dominated resistance. Moreover, the enhanced sensitivity of the ZNB photodetector (PD) was because of the reduced dimensionality and the ultrahigh surface-to-volume ratio. This work lays the groundwork for lower-cost, larger-scale, and lower-temperature production of high-performance nanostructured ZnO-based PDs on transparent and flexible substrates.

Study of the optical properties of ZnO semiconductor nanoparticles using Origanum vulgare and its effect in Rhodamine B degradation

In this work, the effects of different Oregano (Origanum vulgare) extract concentrations on the green synthesis of zinc oxide nanoparticles (ZnO NPs) were studied and their effects on the Band gap values and photocatalytic application in Rhodamine B (RhB) degradation. During the green synthesis of ZnO NPs, a zinc ion source is used as the metal precursor and another of natural extracts as stabilizing agents; with this regard, here in Origanum vulgare extracts were used at 0.1%, 0.5% and 4% (% weight-volume). In order to define the ZnO NPs properties, they were characterized by FTIR, XRD, UV-Vis, HR-TEM, XPS and photoluminescence. In the FTIR analysis, the Zn-O bond can be seen at 384 cm−1; by means of XRD, the hexagonal crystalline phase of ZnO is distinguished (Wurtzite). The extract concentration used influences the ZnO NPs crystallite size and Band gap values as well as the degradation percentage of RhB. The ZnO NPs hold irregular shapes, the majority of which are oval with certain spherical tendencies and they vary in size distribution, which ranges from 37 to 8 nm, the smallest sizes resulting from the highest extract concentrations. The Band gap values are 2.94, 2.77, and 2.29 eV for ZnO-OV-0.1%, ZnO-OV-0.5% and ZnO-OV-4%, respectively, rising as the extract concentrations increase. These materials present good photocatalytic activity, nonetheless, the ZnO NPs synthesized using 4% extract showed the best results, degrading 94.24% of RhB in 100 min in UV light and 93% in 180 min in solar light.

Substrate free Defect-rich one dimensional ZnO nanostructures

One dimensional (1-D) nanostructures of ZnO have been grown using modified ultrasonic-assisted hydrothermal method at low temperature (95οC) in order to investigate its structural, optical and photoluminescence properties. Zinc nitrate and HMT acts as a source of zinc ions (Zn2+) and hydroxide ions (OH−) respectively for the growth of ZnO nanostructures. 1-D ZnO nanostructures consist of well-defined hexagonal shaped nanoscale rods and tubes-like morphologies. The X-ray diffraction pattern confirms the formation of hexagonal wurtzite phase of ZnO with good crystallinity. The crystallite size corresponding to major peaks lies between 39 and 44 nm. The crystallinity corresponding to (0 0 2) plane is found to be 2.061. The optical band gap is found to be 3.42 eV. Room temperature photoluminescence spectrum of 1-D ZnO nanostructures revealed the existence of high concentration of defect emissions i.e. violet, blue-green, green and yellow emissions.

A novel strategy to maintain the long-term viscosity stability of konjac glucomannan hydrosol by using zinc ion

The viscosity of konjac glucomannan (KGM) hydrosol dropped sharply after a period of approximately 12 h. This is a well-known problem which producers are trying to solve. Several salts were added to KGM hydrosols to attempt to improve the long-term viscosity stability of KGM hydrosol. Compared with native KGM hydrosol and KGM hydrosol with Ca2+ and Mg2+, the initial apparent viscosity of KGM hydrosol with Zn2+, in the form of zinc chloride was higher, and the long-term viscosity stability was also significantly increased. This was attributed to Zn2+ preventing the degradation of KGM induced by microbial growth. Bacillus and Paenibacillus were “culprits” in the viscosity reduction of KGM hydrosol. Zn2+ maintained the long-term viscosity stability of the hydrosol by inhibiting microbial growth and enzyme activity of β-mannanase. Zinc sulfate, zinc acetate, and zinc gluconate being edible salts were also used as a source of zinc ions and showed a similar long-term stabilization effect on the viscosity of the KGM hydrosol. These provided a realistic strategy to replace non-edible additives with edible zinc salts for food industry applications.

Hierarchical zinc oxide nanorings with superior sensing properties

Morphology controlled hydrothermal synthesis techniques have been realised to produce hierarchical zinc oxide (ZnO) nanostructures with high surface-to-volume ratios and more exposed polar facets. Hierarchical ZnO nanorings (HNRs) were produced by growing secondary nanowires (NWs) on initial mono-morphological nanodisks (NDs). In the two steps of growth process, zinc sulphate and zinc nitrate were used as the source of zinc ions, respectively. In comparison with NWs and NDs, the grown HNRs showed more enhanced performance as gas sensors. HNRs were substantially sensitive and faster in responding to acetone. This high performance in gas sensing is due to the increased surface-to-volume ratio and small size of the NW building blocks as well as the increased proportion of (0001) polar facets. This work represents a guide to structure induced improvement of sensing properties by controlling the morphology of nanostructures.

The effect of annealing temperature and Al dopant on characterization of ZnO thin films prepared by sol-gel method

Abstract In this project, the sol-gel technique was used to prepare Zinc Oxide (ZnO) thin film and deposited on glass substrate by dip coating method. Zinc acetate dihydrate was used as a source of Zinc ions. The effect of annealing temperature temperatures (300, 400 and 500) °C, Aluminum dopant concentration (3 wt% and 5 wt%) on the properties of ZnO thin film were investigated and analyzed by using X-ray diffraction for structural properties, SEM for morphological properties, UV–VIS for optical properties. X-ray diffraction result has confirmed the formation of hexagonal wurtzite ZnO structure. And the film crystallinity increases with increase the annealing temperature while it decreases with increase Al dopant concentration. The SEM revealed to the formation of a uniform compact surface with ganglia-like hills. The energy band gap (3.28–3.22 eV) found to be decrease with increase the annealing temperature and increase with Al dopant concentrations.

A Controlled Growth of ZnO Nanostructures on ZnS

ZnO nanostructures were developed on a microsphere of ZnS:Cu,Cl phosphor (ZC) for a potential application to a new light source. The growth mechanisms of these nano-structures are very different from those of previously reported methods due to the difference in the zinc ion source of ZnO on the micro-sphere ZC. In this report, ZnO plays two different roles: provision of a seed site and a zinc ion source during the swelling and hydrothermal reaction. In building nanostructures, nano-wires appeared nano-wires first appeared and played a key role in the growth of seed sites of nano-flowers. Additionally, a significant luminance enhancement in the CL spectrum is observed from the emission of the flowers/ZC apparently caused by secondary excitation due to the emission from ZnO nanoflowers.

Synthesis of Dopant Zno Thin Films with Al Using Dip Coating for Gas Sensors

The sol-gel technique (dip coating method) used to synthesize pure Zinc Oxide and Aluminum doped Zinc Oxide thin films on glass substrate for gas sensing application. Zinc acetate dehydrate was used as source of Zinc ions. The influence of annealing temperature of pure ZnO thin films with three different temperatures (300,400,and 500 ) °C, Aluminum dopant concentration with two different concentration (3wt% and 5wt% ) and annealing temperature for AZO thin films with three different temperatures (300,400,and 500 ) °C on gas sensing properties was studied. The results show that ZnO was to be sensitive toward CO gas and its sensitivity decrease with increase in annealing temperature of pure ZnO and (5wt.%) AZO thin films. It is found that the sensitivity of pure ZnO thin films decrease from 67% at 300 °C to 54% and 38% at 400 and 500 °C respectively. Likewise, for 5wt. % AZO thin film the sensitivity improved by increase the Aluminum dopant concentration with fixed annealing temperature 500 °C. It is found that the sensitivity increase form 49% to 57% when doped with Al at (3 wt. %) and (5 wt. %) respectively.

Effect of dopant concentration on structural and optical properties Mn doped ZnS films prepared by CBD method

We present in this work the preparation and characterization of ZnS and Mn doped ZnS thin films. Nanoparticles ZnS:Mn films were prepared by chemical bath deposition method (CBD), for various dopant concentrations. Thin films were deposed onto commercial microscope glass slides substrates. Zinc acetate, manganese acetate and thiourea were used as zinc ion source, manganese ion source and sulfide ion source respectively, in alkaline bath. X-ray diffraction (XRD) analyses were carried out at room temperature with CuKα radiation. The average crystallite size in the deposited films was obtained from a Debye–Scherrer’s formula.The morphology of the film was examined by scanning electron microscopy. IR spectra samples were recorded with the FTIR between 400 and 4000cm−1.The transmittance was performed with the UV–vis spectrometer in the wavelength range 200–800nm.

ZnO nanorod films fabricated on zinc foil for photoelectrochemical water splitting

A photoanode based on ZnO nanorod array film has been successfully synthesised on zinc foil by a simple approach in the NaOH aqueous solution, without the assistance of any catalyst, templates or high temperature and its implementation as photoanode in photoelectrochemical cells for hydrogen generation from water splitting was studied. In this approach, zinc foil was used not only as a substrate but also as a zinc ion source for the direct growth of ZnO nanorod arrays. ZnO nanorod array films were characterised by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The resulting ZnO nanorod showed a diameter of about 70–90 nm and the average length is estimated to be in the range of 0·5–2·0 μm. The good photoresponse of this ZnO nanorod array films have wide applications in the photoelectrochemical field. Therefore, these results suggest substantial potential of ZnO nanorod films in photoelectrochemical water splitting applications.

Easy emission-color-control of Mn-doped zinc silicate phosphor by use of pH and supercritical water conditions

Emission of Zn2SiO4:Mn2+ can be readily controlled to have continuously variable colors between green and yellow by adjusting the pH of the starting solutions in supercritical water syntheses. Mostly single phase β-Zn2SiO4:Mn2+ exhibiting yellow emission was formed at a pH of 10.5. By changing pH of the starting solution from low values (ca. 2.8) to high values (ca. 12.5), emission color could be proportionally varied from green emission to yellow emission because the amount of each phase was found to change. The selectivity of α- and β-Zn2SiO4 crystallization in supercritical water is strongly related to the solubility of dissolved species of the zinc ion source, Zn(OH)2 in water. Photoluminescence results showed that the reaction atmosphere determines emission color over a wide range of dominant wavelengths, 534–571nm, according to the crystalline phases formed. The use of pH with supercritical water allows a simple control strategy for emission color control of Zn2SiO4:Mn2+ phosphors.

Effect Zinc Ion Concentration on Structural and Optical Properties of ZnS Thin Films Prepared by Chemical Bath Deposition Technique

In this work, ZnS films were prepared by chemical bath deposition technique where the zinc nitrate salt (Zn(NO3)2) was used as a source of zinc ions(Zn+2) and thiourea (SC(NH2)2) as a source of negative sulphide ions(S-2). The effect cadmium ion concentration at 0.05 M and 0.1 M on the structural and optical properties is described. Annealing process is carried out in air at temperature 473K for 2h. The structural properties were studied by X-ray diffraction, where found that for ZnS films

Superhydrophobic properties of cotton fabrics functionalized with ZnO by electroless deposition

Cotton fabrics were coated with arrays of ZnO hexagonal prisms using an electroless (catalytic/autocatalytic) deposition process. A typical three step method, similar to those used for electroless deposition of metals on insulating substrates, consisting of pre-activation, activation and deposition steps was employed. The low-dimensional ZnO particles were grown from an aqueous solution containing zinc nitrate as source of zinc ions and dimethylamineborane as reducing agent. The as-obtained ZnO-coated cotton fabrics were characterized from the point of view of structure by X-ray diffraction (XRD) and morphology by scanning electron microscopy (SEM). The XRD studies demonstrate that the ZnO particles have a hexagonal wurtzite crystalline structure. The SEM observations prove that the cotton fibers are homogeneously covered by hexagonal prisms which have uniform base size of approximately 500 nm and height of 1 μm. Optical spectroscopy measurements show that the functionalization with ZnO strongly decreases the transmittance in the UV–vis region of the cotton fabrics. An important characteristic is that the ZnO-functionalized cotton fabrics exhibit superhydrophobicity, with water contact angles exceeding 150°. The technique described is highly reproducible, easy scalable and cheap, allowing a wide range of applications.

Zinc Oxide Nanostructures by Solvothermal Synthesis

The synthesis, characterization, and properties of three types of one-dimensional zinc oxide nanostructures are described. They were obtained by solvothermal treatment of nanometric zinc oxide as zinc ion source (i.e., starting from pure oxide), from a mixture of the oxide with stearic acid, and from intercalated oxide in the layered nanocomposite ZnO(stearic acid)0.38. The reactions were performed at 180°C in a (1:1) ethanol/water mixture. Depending on the precursor and reaction times, morphologically homogenous phases corresponding to ZnO nanoneedles, nanorods or nanowires were obtained. Photoluminescence emissions were observed and are attributed to exciton transitions and to the presence of intrinsic defects such as oxygen and zinc interstitials. The band gap energies (Eg) were comparable to the values of bulk ZnO. The prepared nanostructures showed photocatalytic activities with respect to the degradation of methylene blue which were comparable to that of bulk zinc oxide.

Comparative studies on energy-dependence of reduced effective mass in quantum confined ZnS semiconductor nanocrystals prepared in polymer matrix

Cubic ZnS nanocrystals have been successfully prepared by the wet chemical route at different temperature in polyvinyl alcohol (PVA) matrix. Starting reagents were zinc acetate as a zinc ion source and sodium sulfide as a sulfur ion source. A variety of techniques (Scanning electron microscopy, UV–vis spectroscopy and X-ray diffraction) used to characterize the morphology and optical properties of ZnS nanocrystals. Using Effective Mass Approximation (EMA) and Hyperbolic Band Model (HBM), the variation of reduced effective mass of charge carriers in ZnS nanocrystals is analyzed. Experimental data for band gap energies and size of nanocrystals are used for effective mass calculations. There is a blue shift in band gap of ZnS semiconductor nanocrystals with respect to the bulk value. The average size of nanocrystals are compared with the theoretical predictions and in the most cases are in good agreement with the experimental data. It was found that the value of the reduced effective mass of charge carriers in ZnS nanoparticles differs from its bulk crystals and depends on preparation methods of nanocrystals.

Low-Temperature Growth and Dye-Sensitized Solar Cells Applications of Flower-Shaped ZnO Hexagonal Nanorods

Flower-shaped ZnO structures composed of hexagonal nanorods were grown in a large-quantity via simple aqueous solution process by using zinc nitrate as a source of zinc ions at low-temperature of approximately 85 degrees C. The as-grown flower-shaped ZnO structures composed of hexagonal nanorods were characterized in terms of their structural, optical and photovoltaic properties by using X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) pattern, FTIR, UV-Vis and Raman-scattering spectroscopy. The detailed structural investigations confirmed that the as-synthesized products are well-crystalline and possessing wurtzite hexagonal phase. For the application point of view, the as-grown flower-shaped ZnO structures composed of hexagonal nanorods were used as photo-anode materials to fabricate the dye sensitized solar cells (DSSCs). An overall light to electricity conversion efficiency of 1.1% with a short-circuit current of 4.34 mA/cm2, open-circuit voltage of 0.554 V and fill factor of 0.45, were achieved for the fabricated solar cell based on flower-shaped ZnO structures composed of hexagonal nanorods.

Cytosolic zinc buffering and muffling: Their role in intracellular zinc homeostasis

Our knowledge of the molecular mechanisms of intracellular homeostatic control of zinc ions is now firmly grounded on experimental findings gleaned from the study of zinc proteomes and metallomes, zinc transporters, and insights from the use of computational approaches. A cell's repertoire of zinc homeostatic molecules includes cytosolic zinc-binding proteins, transporters localized to cytoplasmic and organellar membranes, and sensors of cytoplasmic free zinc ions. Under steady state conditions, a primary function of cytosolic zinc-binding proteins is to buffer the relatively large zinc content found in most cells to a cytosolic zinc(ii) ion concentration in the picomolar range. Under non-steady state conditions, zinc-binding proteins and transporters act in concert to modulate transient changes in cytosolic zinc ion concentration in a process that is called zinc muffling. For example, if a cell is challenged by an influx of zinc ions, muffling reactions will dampen the resulting rise in cytosolic zinc ion concentration and eventually restore the cytosolic zinc ion concentration to its original value by shuttling zinc ions into subcellular stores or by removing zinc ions from the cell. In addition, muffling reactions provide a potential means to control changes in cytosolic zinc ion concentrations for purposes of cell signalling in what would otherwise be considered a buffered environment not conducive for signalling. Such intracellular zinc ion signals are known to derive from redox modifications of zinc-thiolate coordination environments, release from subcellular zinc stores, and zinc ion influx via channels. Recently, it has been discovered that metallothionein binds its seven zinc ions with different affinities. This property makes metallothionein particularly well positioned to participate in zinc buffering and muffling reactions. In addition, it is well established that metallothionein is a source of zinc ions under conditions of redox signalling. We suggest that the biological functions of transient changes in cytosolic zinc ion concentrations (presumptive zinc signals) complement those of calcium ions in both spatial and temporal dimensions.

Growth, properties and dye-sensitized solar cells–applications of ZnO nanorods grown by low-temperature solution process

Hexagonal-shaped small ZnO nanorods were grown in a large-quantity via simple aqueous solution process by using zinc nitrate as a source of zinc ions at low temperature under stirring. The as-grown hexagonal-shaped ZnO nanorods were characterized in detail in terms of their structural, optical and photovoltaic properties. The detailed structural investigations by HRTEM, SAED and FFT revealed that the as-synthesized ZnO nanorods are well-crystalline, possessing a perfect hexagonal ideal growth habits of wurtzite zinc oxide and grown along the [0001] direction in preference. The optical properties, composition and quality of the as-synthesized nanorods were examined by using UV-visible and FTIR spectroscopy. Moreover, films of as-grown nanorods were used as photoanode materials to fabricate the dye sensitized solar cells (DSSCs). An overall light to electricity conversion efficiency of 0.70% with a fill factor of 47.2%, short-circuit current of 1.8 mA/cm 2 and open-circuit voltage of 0.76 V were achieved for the solar cell based on hexagonal-shaped small ZnO nanorods.

Highly Oriented 1-D ZnO Nanorod Arrays on Zinc Foil: Direct Growth from Substrate, Optical Properties and Photocatalytic Activities

Highly oriented and large-scale ZnO nanorod arrays have been successfully synthesized on zinc foil by a simple, low-temperature, solution-phase approach. In this approach, zinc foil was used not only as a substrate but also as a zinc-ion source for the direct growth of ZnO nanorod arrays. X-ray diffraction (XRD) analysis, high-resolution TEM (HRTEM) images, and selected-area electron diffraction (SAED) patterns indicated that the structure of the ZnO nanorod arrays on the zinc foil substrate was single-crystalline and grown in the [0001] direction with a wurtzite structure. The optical properties of the ZnO nanorod arrays were characterized by UV−vis diffuse reflectance, Raman, and photoluminescence spectroscopies. The photocatalytic activity of the ZnO nanorod arrays was tested by degradation of 4-chlorophenol (4-CP) under UV light irradiation compared to that of a ZnO nanorod film grown on a Ti substrate, indicating that the as-synthesized ZnO nanorod arrays exhibit excellent photocatalytic activity.