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Zinc Oxide Nanomaterials and Based Devices

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 65226

Special Issue Editors


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Guest Editor
Department of Materials Science, University of Patras, Greece and Institute of Chemical Engineering Sciences (FORTH/ICE-HT), Patras, Greece
Interests: biological mineralization; calcium phosphates; calcium phosphate bone cements; crystal growth; controlled drug delivery systems based on biopolymers; synthesis and characterization of ZnO
Special Issues, Collections and Topics in MDPI journals

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Department of Chemistry, Faculty of Science and Arts and Promising Centre for Sensors and Electronic Devices, Najran University, Najran, Saudi Arabia
Interests: semiconductor nanotechnology; functional nanomaterials; sensors; electronic and energy devices; environmental remediation; bio-applications of functional nanomaterials
Special Issues, Collections and Topics in MDPI journals

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Special Issue Information

Dear Colleagues,

Zinc oxide (ZnO), a II-VI semiconductor, is considered to be one of the most important and multifunctional materials due to its own properties and, hence, wide applications. The tetrahedral coordinated bonding geometry of ZnO crystallizes in the form of a zinc blende type structure or, most commonly, in the hexagonal wurtzite structure. Because of their multifunctional properties, various ZnO nanomaterials such as nanotubes, nanorods, nanowires, nanobelts, nanonails, nanoflowers, hierarchical nanostructures, and so on were synthesized using several synthetic techniques—to name a few, the vapor–liquid–solid thermal sublimation method, hydrothermal growth, electrochemical deposition, molecular beam epitaxy, decomposition of zinc precursor compounds, colloidal or solution based synthesis, etc.

Including various other properties, such as wide band gap and high exciton binding energy, ZnO possesses noncentrosymmetric structures which enable it to be used for the fabrication of various piezoelectric devices and systems. ZnO also possesses interesting biocompatible and environmental benign properties and is thus efficiently used for various chemicals, gases, and biosensors and various other environmental remediation applications. Further, due to their excellent optical, piezoelectric, pyroelectric, and photoconducting properties, ZnO nanostructures are used in a wide range of modern technological applications, including electronic and optoelectronic devices, such as light emitting diodes, sensors and actuators, field emitters, dye-sensitized solar cells, piezoelectric nanogenerators, and so on. Moreover, due to its high isoelectric point, ZnO has the ability to bind biological molecules, making this material suitable for the development of biosensors and other bioanalytical devices.

This Special Issue is a timely approach to surveying recent progress in the area of ZnO nanomaterials and their applications. The articles presented in this Special Issue will cover various topics, ranging from materials preparation, engineering, functionalization, and their various applications, such as sensors (chemical, biological, gas, and so on), environmental remediation, biological labeling, fuel cell, electrocatalysis, catalysis, photocatalysis, electronic devices, bio-applications of nanomaterials, and so on. Certainly, the coverage is not complete, but it is our intention that this Special Issue will offer a unique glimpse of what has been achieved and what remains to be explored in ZnO nanomaterials.

The Special Issue will cover (but not be limited to) the following topics:

  • Synthesis and characterizations of zinc oxide nanomaterials;
  • ZnO-based Sensors (bio, chemical, gas, optical, etc.) ;
  • ZnO-based catalysis and photocatalysis;
  • Environmental remediation using ZnO nanomaterials;
  • Electronic devices based on ZnO nanomaterials;
  • Energy devices based on ZnO nanomaterials;
  • Bio applications based on ZnO nanomaterials;
  • Theoretical studies;
  • Etc.

It is our pleasure to invite you to submit review articles, original papers, and communications for this Special Issue, "Zinc Oxide Nanomaterials and Based Devices".

Prof. Bouropoulos Nikolaos
Prof. Ahmad Umar
Prof. Sotirios Baskoutas
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ZnO nanostructures
  • ZnO quantum dots
  • ZnO nanowires and nanorods
  • ZnO nanocomposites
  • ZnO thin films
  • ZnO random laser diodes
  • ZnO based sensors and biosensors
  • ZnO heterostructure
  • ZnO based devices

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Published Papers (13 papers)

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13 pages, 3739 KiB  
Article
Effect of CeO2-ZnO Nanocomposite for Photocatalytic and Antibacterial Activities
by Asad Syed, Lakshmi Sagar Reddy Yadav, Ali H. Bahkali, Abdallah M. Elgorban, Deshmukh Abdul Hakeem and Nagaraju Ganganagappa
Crystals 2020, 10(9), 817; https://doi.org/10.3390/cryst10090817 - 16 Sep 2020
Cited by 36 | Viewed by 4851
Abstract
The impact of a CeO2-ZnO nanocomposite on the photocatalytic and antibacterial properties compared to bare ZnO was investigated. A CeO2-ZnO nanocomposite was synthesized using Acacia nilotica fruit extract as a novel fuel by a simple solution combustion method. The [...] Read more.
The impact of a CeO2-ZnO nanocomposite on the photocatalytic and antibacterial properties compared to bare ZnO was investigated. A CeO2-ZnO nanocomposite was synthesized using Acacia nilotica fruit extract as a novel fuel by a simple solution combustion method. The obtained CeO2-ZnO nanocomposite was confirmed structurally by XRD, FTIR, Raman and UV-DRS and morphologically by SEM/TEM analysis. The XRD pattern indicates the presence of both hexagonal Wurtzite-structured ZnO (major) and cubic-phase CeO2 (minor). FTIR shows the presence of a Ce-O-Ce vibration at 468 cm−1 and Zn-O vibration at 445 cm−1. The existence of a band at 460 cm−1 confirmed the F2g Raman-active mode of the fluorite cubic crystalline structure for CeO2. Diffused reflectance spectroscopy was used to estimate the bandgap (Eg) from Kubelka–Munk (K–M) theory which was found to be 3.4 eV. TEM analysis shows almost spherical-shaped particles, at a size of about 10–15 nm. The CeO2-ZnO nanocomposite shows a good BET specific surface area of 30 m2g−1. The surface defects and porosity of the CeO2-ZnO nanocomposite caused methylene blue (MB) dye to degrade under sunlight (88%) and UV light (92%). The CeO2-ZnO nanocomposite also exhibited considerable antibacterial activity against a pathogenic bacterial strain. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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Figure 1
<p>(<b>a</b>) Acacia nilotica tree, (<b>b</b>) fruits of Acacia nilotica.</p>
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<p>Interaction of ions between metals and amino acids.</p>
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<p>XRD pattern of CeO<sub>2</sub>-ZnO and ZnO NPs with standard JCPDS.</p>
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<p>FTIR spectrum of CeO<sub>2</sub>-ZnO NPs.</p>
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<p>Raman spectrum of CeO<sub>2</sub>-ZnO NPs.</p>
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<p>Band gap plots of (<b>a</b>) ZnO NPs (inset DRS graph) and (<b>b</b>) the CeO<sub>2</sub>-ZnO (inset DRS graph) nanocomposite.</p>
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<p>Photoluminescence spectrum of the CeO<sub>2</sub>-ZnO nanocomposite.</p>
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<p>(<b>a</b>,<b>b</b>) SEM images and (<b>c</b>) EDS pattern of the CeO<sub>2</sub>-ZnO nanocomposite.</p>
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<p>(<b>a</b>–<b>c</b>) TEM and (<b>d</b>) HRTEM (Inset: SAED pattern) images of the CeO<sub>2</sub>-ZnO nanocomposite.</p>
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<p>(<b>a</b>) N<sub>2</sub> adsorption–desorption isotherms and (<b>b</b>) pore size distribution of ZnO-CeO<sub>2</sub> nanocomposites.</p>
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<p>Photocatalytic degradation of MB dye of (<b>a</b>) ZnO and (<b>b</b>) CeO<sub>2</sub>-ZnO NPs.</p>
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<p>Zone of inhibition of pathogenic bacterial strains <span class="html-italic">K. aerogenes</span> (K) and <span class="html-italic">S. aureus</span> (S) for the CeO<sub>2</sub>-ZnO nanocomposite.</p>
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18 pages, 6854 KiB  
Article
Microwave Irradiation to Produce High Performance Thermoelectric Material Based on Al Doped ZnO Nanostructures
by Neazar Baghdadi, Numan Salah, Ahmed Alshahrie and Kunihito Koumoto
Crystals 2020, 10(7), 610; https://doi.org/10.3390/cryst10070610 - 13 Jul 2020
Cited by 15 | Viewed by 3849
Abstract
Microwave irradiation is found to be effective to provide highly crystalline nanostructured materials. In this work, this technique has been used to produce highly improved thermoelectric (TE) material based on aluminum (Al) doped zinc oxide (ZnO) nanostructures (NSs). The effect of Al dopant [...] Read more.
Microwave irradiation is found to be effective to provide highly crystalline nanostructured materials. In this work, this technique has been used to produce highly improved thermoelectric (TE) material based on aluminum (Al) doped zinc oxide (ZnO) nanostructures (NSs). The effect of Al dopant at the concentration range 0.5–3 mol % on the structural and TE properties has been investigated in more details. The optimum concentration of Al for better TE performance is found to be 2 mol %, which could significantly increase the electrical conductivity and reduce the thermal conductivity of ZnO NSs and thus enhance the TE performance. This concentration showed almost metallic conductivity behavior for ZnO NSs at low temperatures, e.g., below 500 K. The electrical conductivity reached 400 S/m at room temperature, which is around 200 times greater than the value recorded for the pure ZnO NSs. Remarkably, the measured room temperature thermal conductivity of the microwave synthesized ZnO NSs was very low, which is around 4 W/m·K. This value was further reduced to 0.5 W/m·K by increasing the Al doping to 3 mol %. The figure of merit recorded 0.028 at 675 K, which is 15 times higher than that of the pure ZnO NSs. The output power of a single leg module made of 2 mol % Al doped ZnO NSs was 3.7 µW at 485 K, which is higher by 8 times than that of the pure sample. These results demonstrated the advantage of the microwave irradiation rout as a superior synthetic technique for producing and doping promising TE nanomaterials like ZnO NSs. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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Figure 1
<p>X-ray diffraction of pure and Al doped ZnO NSs (<b>A</b>), magnified area of (1, 0, 0) plane (<b>B</b>).</p>
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<p>SEM images of (<b>A</b>) pure and Al doped ZnO NSs, (<b>B</b>) 0.5 mol %, (<b>C</b>) 1 mol %, (<b>D</b>) 2 mol %, and (<b>E</b>) 3 mol %.</p>
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<p>SEM images of (<b>A</b>) pure and Al doped ZnO NSs, (<b>B</b>) 0.5 mol %, (<b>C</b>) 1 mol %, (<b>D</b>) 2 mol %, and (<b>E</b>) 3 mol %.</p>
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<p>TEM images of pure (<b>A</b>,<b>B</b>) and Al doped ZnO (<b>C</b>,<b>D</b>) at a concentration of 3 mol %. The corresponding HRTEM <span class="html-italic">d</span>-spacing measurements are shown in (<b>E</b>,<b>F</b>).</p>
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<p>TEM images of pure (<b>A</b>,<b>B</b>) and Al doped ZnO (<b>C</b>,<b>D</b>) at a concentration of 3 mol %. The corresponding HRTEM <span class="html-italic">d</span>-spacing measurements are shown in (<b>E</b>,<b>F</b>).</p>
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<p>Elemental analysis of ZnO NSs doped with 3 mol % Al. (<b>A</b>) SEM mapping images of all the elements. Individual mapping of (<b>B</b>) Zn, (<b>C</b>) O, (<b>D</b>) Al. EDS quantitative and qualitative analysis is shown in (<b>E</b>).</p>
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<p>FTIR spectra of pure and Al doped ZnO NSs.</p>
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<p>Raman spectra of pure ZnO and Al-doped ZnO NSs.</p>
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<p>X-ray photoelectron spectroscopy of pure and 3 mol % Al doped ZnO NSs. (<b>A</b>) survey scan of the doped sample, the narrow scan of Zn2p<sub>3/2</sub> in the doped sample (<b>B</b>), narrow scan of Al2p in the doped sample (<b>C</b>), and O1s in the doped sample (<b>D</b>). The peak positions of O1s in both pure and Al doped ZnO NSs is shown in (<b>E</b>).</p>
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<p>X-ray photoelectron spectroscopy of pure and 3 mol % Al doped ZnO NSs. (<b>A</b>) survey scan of the doped sample, the narrow scan of Zn2p<sub>3/2</sub> in the doped sample (<b>B</b>), narrow scan of Al2p in the doped sample (<b>C</b>), and O1s in the doped sample (<b>D</b>). The peak positions of O1s in both pure and Al doped ZnO NSs is shown in (<b>E</b>).</p>
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<p>Thermo-electrical properties of pure and Al doped ZnO NSs. (<b>A</b>) Seebeck coefficient, (<b>B</b>) electrical conductivity, (<b>C</b>) power factor measurements, (<b>D</b>) thermal conductivity, and (<b>E</b>) figure of merit.</p>
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<p>Power measurement analysis of the pure and the 2 mol % Al doped ZnO NSs. Voltage–current curves of the pure ZnO NSs (<b>A</b>), and voltage–current curves of the 2 mol % Al doped ZnO NSs (<b>B</b>), output power measurements variation between the pure and 2 mol % Al doped ZnO NSs samples (<b>C</b>).</p>
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10 pages, 2521 KiB  
Article
Quantum-Sized Zinc Oxide Nanoparticles Synthesised within Mesoporous Silica (SBA-11) by Humid Thermal Decomposition of Zinc Acetate
by Tariq Aqeel and Heather F. Greer
Crystals 2020, 10(6), 549; https://doi.org/10.3390/cryst10060549 - 26 Jun 2020
Cited by 12 | Viewed by 3924
Abstract
A modified facile method is presented to synthesise quantum-sized zinc oxide nanoparticles within the pores of a mesoporous silica host (SBA-11). This method eliminates the 3 h alcohol reflux and the basic solution reaction steps of zinc acetate. The mesoporous structure and the [...] Read more.
A modified facile method is presented to synthesise quantum-sized zinc oxide nanoparticles within the pores of a mesoporous silica host (SBA-11). This method eliminates the 3 h alcohol reflux and the basic solution reaction steps of zinc acetate. The mesoporous structure and the ZnO nanoparticles were analysed by X-ray diffractometry, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, nitrogen sorption analysis and UV–VIS spectroscopy. These tests confirm the synthesis of ~1 nm sized ZnO within the pores of SBA-11 and that the porous structure remained intact after ZnO synthesis. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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Figure 1
<p>(<b>a</b>) Low-angle XRD patterns of (*) SBA-11 and (#) ZnO-SBA-11, (<b>b</b>) wide-angle XRD pattern of ZnO-SBA-11.</p>
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<p>(<b>a</b>–<b>c</b>) Bright-field TEM images from different sections of ZnO-SBA-11, (<b>d</b>) is the dark-field TEM image of (<b>c</b>), (<b>e</b>) is the corresponding energy dispersive X-ray spectroscopy (EDX) of (<b>c</b>,<b>d</b>), and (<b>f</b>) is an enlargement of (<b>e</b>).</p>
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<p>XPS of (<b>a</b>,<b>c</b>) SBA-11 and (<b>b</b>,<b>d</b>,<b>e</b>) ZnO-SBA-11.</p>
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<p>N<sub>2</sub> sorption analysis for (<b>a</b>,<b>d</b>) SBA-11, (<b>b</b>,<b>e</b>) control SBA-11 and (<b>c</b>,<b>f</b>) ZnO-SBA-11.</p>
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<p>UV–VIS spectroscopy of ZnO-SBA-11 in the solid state.</p>
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16 pages, 5365 KiB  
Article
Green Synthesis of ZnO Nanostructures Using Salvadora Persica Leaf Extract: Applications for Photocatalytic Degradation of Methylene Blue Dye
by Fahad A. Alharthi, Abdulaziz Ali Alghamdi, Asma A. Alothman, Zainab M. Almarhoon, Munairah F. Alsulaiman and Nabil Al-Zaqri
Crystals 2020, 10(6), 441; https://doi.org/10.3390/cryst10060441 - 30 May 2020
Cited by 54 | Viewed by 5219
Abstract
Various ZnO nanomaterials such as nanorods, nanoparticles, and nanosheets were synthesized using Salvadora persica leaf extract via the sol–gel method. The prepared nanomaterials possess a large number of nanocavities. The synthesized nanomaterials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible [...] Read more.
Various ZnO nanomaterials such as nanorods, nanoparticles, and nanosheets were synthesized using Salvadora persica leaf extract via the sol–gel method. The prepared nanomaterials possess a large number of nanocavities. The synthesized nanomaterials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible diffuse reflectance studies (UV-DRS), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HT-TEM), and these nanomaterials were used to test photocatalytic applications for the degradation of highly hazardous methylene blue dye. The degradation efficiency was higher for materials with nanorods and nanosheets with nanocavities; this was due to the presence of the nanocavities, which made the catalyst more sensitive to light absorption. This method offers a green synthesis of different nanomaterials in bulk quantity at low cost. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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Figure 1
<p>(<b>a</b>,<b>b</b>) SEM images of ZnO nanoparticles prepared.by procedure (a); (<b>c</b>,<b>d</b>) SEM images of ZnO nanoparticles prepared by procedure (b) using <span class="html-italic">S. persica</span> leaf extract.</p>
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<p>(<b>a</b>,<b>b</b>) Transmission electron microscopy (TEM) images of ZnO nanoparticles (A1) prepared.by procedure (a); (<b>c</b>,<b>d</b>) TEM images of ZnO nanoparticles (B1) prepared by procedure (b) using <span class="html-italic">S. persica</span> leaf extract.</p>
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<p>(<b>a</b>), (<b>b</b>) TEM images. (<b>c</b>) HR-TEM images. (<b>d</b>) SAED pattern of material of <span class="html-italic">S. persica</span> leaf extract.</p>
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<p>XRD pattern of <b>A1</b> and <b>B1</b> synthesized using <span class="html-italic">S. persica</span> leaf extract.</p>
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<p>FT-IR spectra of <b>A1</b> and <b>B1</b> synthesized using <span class="html-italic">S. persica</span> leaf extract.</p>
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<p>(<b>a</b>) UV-visible diffuse reflectance spectrum. (<b>b</b>) Bandgap calculation graph.</p>
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<p>Degradation efficiency of catalysts <b>A1</b> and <b>B1</b>.</p>
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<p>Photoluminescence spectrum indicating generation of OH<sup>•</sup> ion by B1 at different time intervals.</p>
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<p>Degradation of MB with varying dye concentration and a constant catalyst load (B1).</p>
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<p>Degradation of MB with varying catalyst loads (B1) and constant dye concentration.</p>
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<p>Degradation of MB with varying pH in the solution, constant catalyst load (B1) and dye.</p>
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<p>Degradation of MB carried out using recycling of the catalyst load (B1).</p>
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<p>Structure of (<b>a</b>) salvadorine, (<b>b</b>) salvadoside, and (<b>c</b>) salvadoricine.</p>
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<p>Flow chart of the two different synthetic protocols applied for the synthesis of ZnO nanoparticles.</p>
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<p>Schematic representation of the role of phytomolecules of <span class="html-italic">S. persica</span> leaf extract in the synthesis process of ZnO nanorods/nanoparticles.</p>
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24 pages, 7637 KiB  
Article
Enhancement of ZnO Nanorods Properties Using Modified Chemical Bath Deposition Method: Effect of Precursor Concentration
by Ahmed Fattah Abdulrahman, Sabah Mohammed Ahmed, Naser Mahmoud Ahmed and Munirah Abullah Almessiere
Crystals 2020, 10(5), 386; https://doi.org/10.3390/cryst10050386 - 9 May 2020
Cited by 43 | Viewed by 4608
Abstract
In this study, the effects of different precursor concentrations on the growth and characteristics properties of the zinc oxide (ZnO) nanorods (NRs) synthesized by using modified and conventional chemical bath deposition (CBD) methods were investigated. The morphologic, structural and optical properties of synthesized [...] Read more.
In this study, the effects of different precursor concentrations on the growth and characteristics properties of the zinc oxide (ZnO) nanorods (NRs) synthesized by using modified and conventional chemical bath deposition (CBD) methods were investigated. The morphologic, structural and optical properties of synthesized ZnO NRs with different precursor concentrations were studied using various characterization techniques. The experimental results show that the varying precursor concentration of the reactants has a remarkable and significant effect on the growth and characteristics properties of ZnO NRs. In addition, the characteristic properties of ZnO NRs grown using the modified method showed significantly improved and enhanced properties. The average length of grown ZnO NRs increased with increased precursor concentration; it can be seen that longer ZnO NRs have been investigated using the modified CBD methods. The ZnO NRs synthesized at 0.05 M using the modified method were grown with high aspect ratios than the ZnO NRs grown using conventional means which were 25 and 11, respectively. The growth rate increased with increased precursor concentration; it can be observed that a higher growth rate was seen using the modification CBD method. Furthermore, XRD results for the two cases reveal that the grown ZnO samples were a nanorod-like in shape and possessed a hexagonal wurtzite structure with high crystal quality. No other phases from the impurity were observed. The diffraction peaks along (002) plane became higher, sharper and narrower as precursor concentration increased, suggesting that the crystalline quality of ZnO NRs grown using the modified method was more enhanced and better than conventional methods. However, optical studies show that the transmittance at each concentration was more than two times higher than the transmittance using the modified CBD method. In addition, optical studies demonstrated that the ZnO NRs grown by using modified and conventional methods had a direct Eg in the range of (3.2–3.26) eV and (3.15–3.19) eV, respectively. It was demonstrated in two methods that ZnO NRs grown at a precursor concentration 0.05 M gave the most favorable result, since the NRs had best characteristic properties. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>Schematic of Modified and Conventional CBD Method.</p>
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<p>FESEM images of ZnO nanorods grown for different precursor concentrations, no air bubbles: (<b>a</b>) 0.01 M, (<b>b</b>) 0.025 M, (<b>c</b>) 0.05 M &amp; (<b>d</b>) 0.075 M and Air Bubble: (<b>e</b>) 0.01 M, (<b>f</b>) 0.025 M, (<b>g</b>). 0.05 M and (<b>h</b>) 0.075 M. The insets at the upper right corner represent the cross-section of ZnO nanorods for each concentration representing the cross-section of nanorods.</p>
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<p>Effect of different precursor concentrations on ZnO nanorods grown using conventional and modified methods: (<b>a</b>) average diameter, (<b>b</b>) average length, (<b>c</b>) aspect ratio and (<b>d</b>) growth rate.</p>
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<p>Effect of precursor concentration on the initial and final growth solution pH values for ZnO nanorods synthesized in the presence and absence of air bubbles.</p>
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<p>Typical EDX analysis of ZnO nanorods for different precursor concentrations in the absence of air bubbles: (<b>a</b>) 0.01 M, (<b>b</b>) 0.025 M, (c) 0.05 M and (<b>d</b>) 0.075 M and the presence of air bubbles: (<b>e</b>) 0.01 M, (<b>f</b>) 0.025 M, (<b>g</b>) 0.05 M and (<b>h</b>) 0.075 M.</p>
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<p>X-ray diffraction (XRD) patterns of ZnO nanorods for different precursor concentrations in the absence of air bubbles: (<b>a</b>) 0.01 M, (<b>b</b>) 0.025 M, (<b>c</b>) 0.05 M and (<b>d</b>) 0.075 M and the presence of air bubbles: (<b>e</b>) 0.01 M, (<b>f</b>) 0.025 M, (<b>g</b>) 0.05 M and (<b>h</b>) 0.075 M.</p>
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<p>Precursor concentrations versus intensity of ZnO nanorods along diffraction peak (002) plane in the presence and absence of air bubbles.</p>
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<p>(<b>a</b>) Variation of crystalline size and (<b>b</b>) full-width at half-maximum FWHM along diffraction peak (002) at precursor concentrations of ZnO nanorods grown in in the presence and absence of air bubbles.</p>
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<p>Variation of dislocation density at several precursor concentrations for both preparation methods, conventional and modified CBD, respectively.</p>
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<p>Effect of precursor concentration on (<b>a</b>) volume of hexagonal cell (<b>b</b>) bond length along diffraction peak (002) of synthesized ZnO nanorods in the presence and absence of air bubbles.</p>
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<p>Optical transmittance spectrum of ZnO nanorods synthesized at different precursor concentration in the (<b>a</b>) absence and (<b>b</b>) presence of air bubbles.</p>
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<p>Precursor concentration versus average transmittance of synthesized ZnO nanorods in the presence and absence of air bubbles.</p>
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<p>Optical transmittance spectrums versus average length of ZnO nanorods grown by both conventional and modified CBD methods at different precursor concentrations.</p>
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<p>Variation of (αhν)<sup>2</sup> versus applied energy (hν) of the synthesized ZnO nanorods using conventional CBD method at several precursor concentration, (<b>a</b>) 0.01 M, (<b>b</b>) 0.025 M, (<b>c</b>) 0.05 M and (<b>d</b>) 0.075 M.</p>
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<p>Variation of (αhν)<sup>2</sup> versus applied energy (hν) of the synthesized ZnO nanorods using modified CBD method at several concentration, (<b>a</b>) 0.01 M, (<b>b</b>) 0.025 M, (<b>c</b>) 0.05 M and (<b>d</b>) 0.075 M.</p>
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9 pages, 1693 KiB  
Article
ZnO@TiO2 Core/Shell Nanowire Arrays with Different Thickness of TiO2 Shell for Dye-Sensitized Solar Cells
by Liqing Liu, Hui Wang, Dehao Wang, Yongtao Li, Xuemin He, Hongguang Zhang and Jianping Shen
Crystals 2020, 10(4), 325; https://doi.org/10.3390/cryst10040325 - 21 Apr 2020
Cited by 11 | Viewed by 3652
Abstract
The ZnO@TiO2 core/shell nanowire arrays with different thicknesses of the TiO2 shell were synthesized, through depositing TiO2 on the ZnO nanowire arrays using the pulsed laser deposition process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that [...] Read more.
The ZnO@TiO2 core/shell nanowire arrays with different thicknesses of the TiO2 shell were synthesized, through depositing TiO2 on the ZnO nanowire arrays using the pulsed laser deposition process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that these core/shell nanowires were homogeneously coated with TiO2 nanoparticles with high crystallinity, appearing to be a rather rough surface compared to pure ZnO nanowires. The efficiency of ZnO@TiO2 core/shell structure-based dye-sensitized solar cells (DSSCs) was improved compared with pure ZnO nanowires. This is mainly attributed to the enlarged internal surface area of the core/shell structures, which increases dye adsorption on the anode to improve the light harvest. In addition, the energy barrier which formed at the interface between ZnO and TiO2 promoted the charge separation and suppressed the carrier recombination. Furthermore, the efficiency of DSSCs was further improved by increasing the thickness of the TiO2 shell. This work shows an efficient method to achieve high power conversion efficiency in core/shell nanowire-based DSSCs. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>Schematic drawing of the synthesis process of the samples. (<b>a</b>) FTO glass substrate; (<b>b</b>) ZnO seed layer; (<b>c</b>) ZnO nanowire arrays; (<b>d</b>) TiO<sub>2</sub> shell is deposited on ZnO surface by PLD; (<b>e</b>) ZnO@TiO<sub>2</sub> nanowire arrays; (<b>f</b>) sandwich structure of solar sell.</p>
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<p>Cross-sectional SEM images of aligned ZnO nanowire arrays (<b>a</b>,<b>b</b>) and ZnO@TiO<sub>2</sub> core/shell nanowire arrays by microwave heating method followed by PLD process, depositing TiO<sub>2</sub> with 3000 pulses (<b>c</b>,<b>d</b>).</p>
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<p>SEM of ZnO@TiO<sub>2</sub> core/shell nanowire arrays synthesized with 1000 pulses (<b>a</b>) and 5000 pulses (<b>b</b>), respectively.</p>
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<p>EDX spectra of ZnO (1#) and ZnO@TiO<sub>2</sub> core/shell nanowire arrays with different pulse number of 1000 (2#), 3000 (3#) and 5000 (4#). Inset shows the Ti atomic ratio as the function of pulse number.</p>
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<p>TEM (<b>a</b>,<b>b</b>) and HRTEM (<b>c</b>,<b>d</b>) images of ZnO@TiO<sub>2</sub> core/shell nanowire arrays fabricated by pulsed laser deposition (PLD) depositing TiO<sub>2</sub> layer on ZnO nanowire.</p>
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<p>Photocurrent density-voltage curves of ZnO and ZnO@TiO<sub>2</sub> core/shell nanowire arrays, with different thicknesses of the TiO<sub>2</sub> shell.</p>
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9 pages, 2885 KiB  
Communication
Fabrication of Lettuce-Like ZnO Gas Sensor with Enhanced H2S Gas Sensitivity
by Ziyang Yu, Jie Gao, Longxiao Xu, Tianyu Liu, Yueying Liu, Xiangyue Wang, Hui Suo and Chun Zhao
Crystals 2020, 10(3), 145; https://doi.org/10.3390/cryst10030145 - 26 Feb 2020
Cited by 34 | Viewed by 3312
Abstract
In this work, a lettuce-like ZnO gas sensor with high sensitivity for H2S detection was successfully fabricated by a one-step hydrothermal method. Characterization analysis of the phases, crystallinities, morphology, and chemical compositions indicated that lettuce-like ZnO has a lettuce-like microsphere structure [...] Read more.
In this work, a lettuce-like ZnO gas sensor with high sensitivity for H2S detection was successfully fabricated by a one-step hydrothermal method. Characterization analysis of the phases, crystallinities, morphology, and chemical compositions indicated that lettuce-like ZnO has a lettuce-like microsphere structure composed of wurtzite hexagonal ZnO sheets. A gas sensitivity test of the lettuce-like ZnO showed that the sensor had a high H2S response (113.04 for 100 ppm H2S) and H2S selectivity. The lettuce-like ZnO sensor has fast response characteristics while maintaining high sensitivity, and has a response time as low as 15 seconds and a recovery time of 90 seconds, and the detection limit reaches 1 ppm. The sensitive mechanism of lettuce-like ZnO sensor to H2S is also discussed. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>XRD pattern of the as-prepared lettuce-like ZnO.</p>
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<p>Representative SEM images of (<b>a</b>) the ZnO precursor before calcination; (<b>b</b>–<b>d</b>) the as-prepared lettuce-like ZnO.</p>
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<p>(<b>a</b>) Gas sensing response of lettuce-like ZnO sensors and commercial ZnO at different operating temperatures to 100 ppm H<sub>2</sub>S, (<b>b</b>) the selectivity of lettuce-like ZnO sensors to 100 ppm different gases, (<b>c</b>) the repeatability of lettuce-like ZnO sensors at 150 °C to 100 ppm H<sub>2</sub>S, (<b>d</b>) the response and recovery of lettuce-like ZnO sensors to 100 ppm H<sub>2</sub>S, (<b>e</b>) the dynamic response of lettuce-like ZnO sensors to 1−100 ppm H<sub>2</sub>S at 150 °C, (<b>f</b>) the response of lettuce-like ZnO sensors to 1−100 ppm H<sub>2</sub>S at 150 °C.</p>
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<p>The long-term stability of the lettuce-like ZnO sensor to 100 ppm H<sub>2</sub>S.</p>
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<p>The schematic diagram of the gas-sensing reaction process.</p>
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12 pages, 4369 KiB  
Article
Hydrothermal Synthesis of (001) Facet Highly Exposed ZnO Plates: A New Insight into the Effect of Citrate
by Shirui Luo, Ruosong Chen, Lan Xiang and Jing Wang
Crystals 2019, 9(11), 552; https://doi.org/10.3390/cryst9110552 - 24 Oct 2019
Cited by 15 | Viewed by 4480
Abstract
In this work, two synthesis routes were applied to investigate the effect of citrates on the construction of the ZnO structure. Well-dispersed ZnO plates with (001) facet highly exposed were prepared via one-step hydrothermal route, while ZnO nanoparticles were obtained via two-step route. [...] Read more.
In this work, two synthesis routes were applied to investigate the effect of citrates on the construction of the ZnO structure. Well-dispersed ZnO plates with (001) facet highly exposed were prepared via one-step hydrothermal route, while ZnO nanoparticles were obtained via two-step route. In one-step route, citrates were added before the formation of Zn(OH)2 precursor, while citrates were added after the formation of Zn(OH)2. For the first time, the interaction between citrates and the Zn(OH)2 precursor was investigated and citrates that participated in the formation of Zn(OH)2 were the main cause for (001) facet exposed structure construction. A growth mechanism about the formation of ZnO plates in the presence of citrates was proposed. The as-prepared ZnO plates showed enhanced photocatalytic activity for the degradation of methylene blue (MB). Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>XRD patterns for all products.</p>
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<p>SEM images for all products and TEM image for ZnO-OS: (<b>a</b>)ZnO-OS; (<b>b</b>) ZnO-TS; (<b>c</b>) ZnO-NC; and (<b>d</b>)TEM and SAED images for ZnO-OS.</p>
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<p>SEM images of products obtained in OS route at different times: (<b>a</b>) 0 min; (<b>b</b>) 10 min; (<b>c</b>) 20 min; (<b>d</b>) 30 min; (<b>e</b>) 50 min; and (<b>f</b>) 70 min.</p>
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<p>Variation of soluble zinc concentration with reaction time.</p>
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<p>XRD pattern of the strip precursor taken at 20 min in OS route.</p>
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<p>Phase analysis of the particle aggregates precursor at 0 min in OS route: (<b>a</b>) TEM and SAED pattern; (<b>b</b>) FT-IR spectra; and (<b>c</b>) XRD pattern.</p>
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<p>FT-IR spectrum of OS products at 0, 30, and 60 min.</p>
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<p>Schematic illustration of mechanism of citrate capping effect in: (<b>a</b>) OS route; and (<b>b</b>)TS route.</p>
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<p>Photodegradation of MB solution with: (<b>a</b>) no samples; (<b>b</b>) ZnO nanorods; and (<b>c</b>) ZnO-OS.</p>
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13 pages, 3227 KiB  
Article
Direct Growth of Flower-Shaped ZnO Nanostructures on FTO Substrate for Dye-Sensitized Solar Cells
by Ahmad Umar, Mohammad Shaheer Akhtar, Tubia Almas, Ahmed Abdulbaqi Ibrahim, Mohammed Sultan Al-Assiri, Yoshitake Masuda, Qazi Inamur Rahman and Sotirios Baskoutas
Crystals 2019, 9(8), 405; https://doi.org/10.3390/cryst9080405 - 4 Aug 2019
Cited by 20 | Viewed by 5394
Abstract
The proposed work reports that ZnO nanoflowers were grown on fluorine-doped tin oxide (FTO) substrates via a solution process at low temperature. The high purity and well-crystalline behavior of ZnO nanoflowers were established by X-ray diffraction. The morphological characteristics of ZnO nanoflowers were [...] Read more.
The proposed work reports that ZnO nanoflowers were grown on fluorine-doped tin oxide (FTO) substrates via a solution process at low temperature. The high purity and well-crystalline behavior of ZnO nanoflowers were established by X-ray diffraction. The morphological characteristics of ZnO nanoflowers were clearly revealed that the grown flower structures were in high density with 3D floral structure comprising of small rods assembled as petals. Using UV absorption and Raman spectroscopy, the optical and structural properties of the ZnO nanoflowers were studied. The photoelectrochemical properties of the ZnO nanoflowers were studied by utilizing as a photoanode for the manufacture of dye-sensitized solar cells (DSSCs). The fabricated DSSC with ZnO nanoflowers photoanode attained reasonable overall conversion efficiency of ~1.40% and a short-circuit current density (JSC) of ~4.22 mA cm−2 with an open circuit voltage (VOC) of 0.615 V and a fill factor (FF) of ~0.54. ZnO nanostructures have given rise to possible utilization as an inexpensive and efficient photoanode materials for DSSCs. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>Typical XRD pattern of flower-shaped ZnO nanostructures directly grown on fluorine-doped tin oxide (FTO) substrate.</p>
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<p>Typical field-emission scanning electron microscopy (FESEM) images (<b>a–d</b>) of flower-shaped ZnO nanostructures directly grown on FTO substrate.</p>
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<p>Room temperature PL spectrum of flower-shaped ZnO nanostructures directly grown on FTO substrate.</p>
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<p>Typical Raman scattering spectrum of flower-shaped ZnO nanostructures directly grown on FTO substrate.</p>
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<p>Typical XPS (<b>a</b>) full survey, (<b>b</b>) Zn 2p, and (<b>c</b>) O1s spectrum of flower-shaped ZnO nanostructures directly grown on FTO substrate.</p>
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<p>Typical (<b>a</b>) current density-voltage (<span class="html-italic">J</span>–<span class="html-italic">V</span>) characteristics and (<b>b</b>) incident photon-to-current conversion efficiency (IPCE) curve of manufactured dye-sensitized solar cells (DSSCs) with flower-shaped ZnO nanostructures based photoanode.</p>
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<p>Nyquist plot of fabricated DSSC with flower-shaped ZnO nanostructure-based photoanode and inset shows equivalent circuit of fabricated device.</p>
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8 pages, 1865 KiB  
Article
Raman Spectra and Microstructure of Zinc Oxide irradiated with Swift Heavy Ion
by Yin Song, Shengxia Zhang, Chonghong Zhang, Yitao Yang and Kangyuan Lv
Crystals 2019, 9(8), 395; https://doi.org/10.3390/cryst9080395 - 31 Jul 2019
Cited by 108 | Viewed by 14303
Abstract
Zinc oxide (ZnO) materials irradiated with 350 MeV 56Fe21+ ions were studied by Raman spectroscopy, Photoluminescence spectra (PL) and Transmission electron microscope (TEM). After 56Fe21+ ion irradiation, a strong oxygen vacancy (Vo) related defect absorption peak at [...] Read more.
Zinc oxide (ZnO) materials irradiated with 350 MeV 56Fe21+ ions were studied by Raman spectroscopy, Photoluminescence spectra (PL) and Transmission electron microscope (TEM). After 56Fe21+ ion irradiation, a strong oxygen vacancy (Vo) related defect absorption peak at 576 cm−1 and an interstitial zinc (Zni) -related defect at 80 cm−1~200 cm−1 formed, and with the increase of dose, the absorption peak was obviously enhanced. Through theoretical calculation, different Raman incident light test methods wereused to determine the oxygen vacancy defect (Vo). There were no significant variation tendencies in the other Raman characteristic lines. Our results demonstrate an energy loss process contributing to the defect structure during irradiation. TEM images showed a lot of fundamental defects. But we see no distinct amorphization in the samples in the electron diffraction images, indicating that the higher energy and irradiation dose hardly affected the structure and performance of zinc oxide. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>Raman spectra of ZnO irradiated and unirradiated by <sup>56</sup>Fe<sup>21+</sup> ions were measured. Direction of the laser was along the axis [0001] of the crystal. The ZnO structure of wurtzite is shown in the figure. The Raman peaks are assigned by corresponding atomic oscillations (the motion of the dominant atom is indicated by the red arrow).</p>
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<p>Raman spectra (incident light is perpendicular to the axis [0001]) of ZnO irradiated by <sup>56</sup>Fe<sup>21+</sup> ion with irradiation does of 1 × 10<sup>14</sup> ions/cm<sup>2</sup>. The incident ions were along [0001] of the crystal. The zinc oxide structure of wurtzite is shown in the image. The Raman peaks are described by corresponding atomic oscillations. (The motion of the dominant atom is indicated by the red arrows).</p>
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<p><b>TEM</b> images and corresponding diffraction patterns of <sup>56</sup>Fe<sup>21+</sup> ion irradiated ZnO at different depths ((<b>a</b>) is 2 μm, (<b>b</b>) is 10 μm, (<b>c</b>) is 25 μm, (<b>d</b>) is 32 μm) along the incident direction of <sup>56</sup>Fe<sup>21+</sup> ions. Irradiation does of heavy ions were 1 × 10<sup>14</sup> ions/cm<sup>2</sup>.</p>
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<p>PL spectra of ZnO irradiated with <sup>56</sup>Fe<sup>21+</sup> ions measured by excited light at 340 nm. The image on the upper right is a panorama of the image.</p>
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<p>PL spectra of ZnO irradiated with 1 × 10<sup>13</sup> ions/cm <sup>256</sup>Fe<sup>21+</sup> ions. Experimental data (black line) were fitted with Voigt peaks, the red curve represents the sum of fitted peaks (green peaks) plus background.</p>
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<p>Phonon dispersion relationship of wurtzite zinc oxide are calculatedat Γ point in the specified direction of the Brillouin zonecenter by using the lattice dynamics equation. Molecular vibration represented by red font (<span class="html-italic">E</span><sub>1</sub>, <span class="html-italic">E</span><sub>2</sub>, <span class="html-italic">A</span><sub>1</sub>) can be observed through Raman scattering, while <span class="html-italic">B</span><sub>1</sub> mode represented by green font can’t be observed through Raman scattering.</p>
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9 pages, 2818 KiB  
Article
Passivation Effect on ZnO Films by SF6 Plasma Treatment
by Yumeng Xu, Baoxue Bo, Xin Gao and Zhongliang Qiao
Crystals 2019, 9(5), 236; https://doi.org/10.3390/cryst9050236 - 5 May 2019
Cited by 23 | Viewed by 4427
Abstract
The passivation effects of SF6 plasma on zinc oxide (ZnO) films prepared by magnetron sputtering were researched. After the SF6 plasma passivation of ZnO films, the grain size increases, there is low surface roughness, and a small amount of Zn-F bonds [...] Read more.
The passivation effects of SF6 plasma on zinc oxide (ZnO) films prepared by magnetron sputtering were researched. After the SF6 plasma passivation of ZnO films, the grain size increases, there is low surface roughness, and a small amount of Zn-F bonds are formed, resulting in the narrowing of band gap. The photoluminescence (PL) intensity of SF6-passivated ZnO films has a 120% increase compared to the untreated samples, and the reduction in defects can increase the resistivity and stability of ZnO films. ZnO films are used in the preparation of ZnO/p-Si heterojunction diodes. The results of the measurement of current voltage (J–V) show that the reverse current is reduced after SF6 plasma passivation, indicating an improvement in the electrical properties of ZnO films. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>The X-ray diffraction (XRD) of ZnO films with and without SF<sub>6</sub> plasma treatment.</p>
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<p>The atomic force microscopy (AFM) of the surface of ZnO films with and without SF<sub>6</sub> plasma treatment, (<b>a</b>) without passivation, (<b>b</b>) with passivation.</p>
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<p>The X-ray photoelectron spectroscopy (XPS) measurement of the surface of ZnO films without and with SF<sub>6</sub> plasma treatment: (<b>a</b>) Zn 2p3/2, (<b>b</b>) F 1s, and (<b>c</b>) and (<b>d</b>) O 1s.</p>
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<p>(<b>a</b>) The photoluminescence (PL) of ZnO films with and without SF<sub>6</sub> plasma treatment and (<b>b</b>) the energy level diagram of ZnO.</p>
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<p>The low temperature PL spectra of ZnO films with and without SF<sub>6</sub> plasma passivation.</p>
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<p>The PL intensity stability of ZnO films with and without SF<sub>6</sub> plasma treatment.</p>
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<p>(<b>a</b>) ZnO/p-Si heterojunction diode and (<b>b</b>) the J–V curve of ZnO/p-Si heterojunction diode with and without SF<sub>6</sub> plasma treatment.</p>
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9 pages, 1817 KiB  
Article
The Decoloration of Anionic and Cationic Dyes Using ZnO and ZnO-Cu2O
by Jiang Dong Dai, Luo Gan, Hai Yan Zhang and Chun Ming Liu
Crystals 2019, 9(5), 229; https://doi.org/10.3390/cryst9050229 - 28 Apr 2019
Cited by 6 | Viewed by 3027
Abstract
ZnO and ZnO-Cu2O were grown on aluminum foam using hydrothermal method. Due to the positively charged sites on the surface, both ZnO and ZnO-Cu2O show higher adsorption capability towards anionic dyes, but poorer adsorption capability towards cationic dyes. The [...] Read more.
ZnO and ZnO-Cu2O were grown on aluminum foam using hydrothermal method. Due to the positively charged sites on the surface, both ZnO and ZnO-Cu2O show higher adsorption capability towards anionic dyes, but poorer adsorption capability towards cationic dyes. The adsorption ability of ZnO-Cu2O is smaller than that of ZnO since there is a depletion layer at the interface. In order to decolorize cationic dyes, ZnO and ZnO-Cu2O are used as sono-catalyst with ultrasonic irradiation. The ZnO-Cu2O is better than ZnO in sono-catalysis decoloration of cationic dyes. This may be due to the enhanced piezoelectricity and electrochemical activity, as the free electrons in ZnO are reduced in the depletion layer. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>The scanning electron microscopy (SEM) of ZnO (<b>a</b>), Cu<sub>2</sub>O (<b>b</b>), and ZnO-Cu<sub>2</sub>O (<b>c</b>) sample.</p>
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<p>The XRD of aluminum (Al) foam, ZnO, Cu<sub>2</sub>O and ZnO-Cu<sub>2</sub>O sample.</p>
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<p>The Zn 2p X-ray photoelectron spectroscopy (XPS) of ZnO and ZnO-Cu<sub>2</sub>O.</p>
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<p>The optical absorption of methyl orange (MO) decolorized by adsorption using ZnO (<b>a</b>), Cu<sub>2</sub>O (<b>b</b>), and ZnO-Cu<sub>2</sub>O (<b>c</b>) as adsorbents.</p>
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<p>The pseudo-first-order kinetics fit the concentration as a function of time.</p>
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<p>The decolorization of methylene blue (MB) with Al foam, ZnO, and ZnO-Cu<sub>2</sub>O as catalyst under ultrasonic irradiation.</p>
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<p>The decolorization of MB using ultrasonic irradiation.</p>
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<p>The mechanism of the enhancement of decoloration rate (DR) by depletion layer.</p>
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7 pages, 1213 KiB  
Article
Passivation Mechanism of Nitrogen in ZnO under Different Oxygen Ambience
by Xingyou Chen, Zhenzhong Zhang, Yunyan Zhang, Bin Yao, Binghui Li and Qian Gong
Crystals 2019, 9(4), 204; https://doi.org/10.3390/cryst9040204 - 12 Apr 2019
Cited by 4 | Viewed by 2959
Abstract
Nitrogen-doped ZnO thin films were grown on a-plane Al2O3 by plasma-assisted molecular beam epitaxy. Hall-effect measurements indicated that the nitrogen-doped ZnO films showed p-type behavior first, then n-type, with the growth conditions changing from oxygen-radical-rich to oxygen-radical-deficient ambience, accompanied with [...] Read more.
Nitrogen-doped ZnO thin films were grown on a-plane Al2O3 by plasma-assisted molecular beam epitaxy. Hall-effect measurements indicated that the nitrogen-doped ZnO films showed p-type behavior first, then n-type, with the growth conditions changing from oxygen-radical-rich to oxygen-radical-deficient ambience, accompanied with the increase of the N/O ratio in the plasmas. The increasing green emission in the low temperature photoluminescence spectra, related to single ionized oxygen vacancy in ZnO, was ascribed to the decrease of active oxygen atoms in the precursor plasmas. CN complex, a donor defect with low formation energy, was demonstrated to be easily introduced into ZnO under O-radical-deficient ambience, which compensated the nitrogen-related acceptor, along with the oxygen vacancy. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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<p>The XRD patterns of the undoped zinc oxide (ZnO), and ZnO:N films grown under (A) F<sub>NO</sub> = 0.8, F<sub>N2</sub> = 0.4, (B) F<sub>NO</sub> = 0.6, F<sub>N2</sub> = 0.6 and (C) F<sub>NO</sub> = 0.4, F<sub>N2</sub> = 0.8 (SCCM).</p>
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<p>Room temperature Raman backscattering spectra for samples (<b>a</b>) A, (<b>b</b>) B, and (<b>c</b>) C.</p>
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<p>N 1s XPS spectra for the samples (<b>a</b>) A, (<b>b</b>) B, and (<b>c</b>) C, respectively.</p>
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<p>PL spectra of the samples (<b>a</b>) A, (<b>b</b>) B, and (<b>c</b>) C at 83 K.</p>
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