Special Issue "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 April 2020).

Special Issue Editors

Prof. Nikolaos Bouropoulos
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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
Prof. Dr. Ahmad Umar
Website
Guest Editor
Department of Chemistry, Faculty of Science and Arts and Promising Centre for Sensors and Electronic Devices, Najran University, Najran, Kingdom of Saudi Arabia
Interests: semiconductor nanotechnology; functional nanomaterials; sensors; electronic and energy devices; environmental remediation; bio-applications of functional nanomaterials
Special Issues and Collections in MDPI journals
Prof. Dr. Sotirios Baskoutas
Website
Guest Editor
Department of Materials Science, University of Patras, Patra, Greece
Interests: theoretical and computational methods for the study of the electronic and optical properties of semiconducting nanomaterials; synthesis with physical methods; characterization of amorphous and nanocrystalline materials
Special Issues and Collections in MDPI journals

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

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 1600 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

Published Papers (9 papers)

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Research

Open AccessArticle
Enhancement of ZnO Nanorods Properties Using Modified Chemical Bath Deposition Method: Effect of Precursor Concentration
Crystals 2020, 10(5), 386; https://doi.org/10.3390/cryst10050386 - 09 May 2020
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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Open AccessArticle
[email protected]2 Core/Shell Nanowire Arrays with Different Thickness of TiO2 Shell for Dye-Sensitized Solar Cells
Crystals 2020, 10(4), 325; https://doi.org/10.3390/cryst10040325 - 21 Apr 2020
Abstract
The [email protected]2 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 [email protected]2 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 [email protected]2 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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Open AccessCommunication
Fabrication of Lettuce-Like ZnO Gas Sensor with Enhanced H2S Gas Sensitivity
Crystals 2020, 10(3), 145; https://doi.org/10.3390/cryst10030145 - 26 Feb 2020
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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Open AccessArticle
Hydrothermal Synthesis of (001) Facet Highly Exposed ZnO Plates: A New Insight into the Effect of Citrate
Crystals 2019, 9(11), 552; https://doi.org/10.3390/cryst9110552 - 24 Oct 2019
Cited by 1
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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Open AccessArticle
Direct Growth of Flower-Shaped ZnO Nanostructures on FTO Substrate for Dye-Sensitized Solar Cells
Crystals 2019, 9(8), 405; https://doi.org/10.3390/cryst9080405 - 04 Aug 2019
Cited by 4
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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Open AccessArticle
Raman Spectra and Microstructure of Zinc Oxide irradiated with Swift Heavy Ion
Crystals 2019, 9(8), 395; https://doi.org/10.3390/cryst9080395 - 31 Jul 2019
Cited by 1
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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Open AccessArticle
Passivation Effect on ZnO Films by SF6 Plasma Treatment
Crystals 2019, 9(5), 236; https://doi.org/10.3390/cryst9050236 - 05 May 2019
Cited by 1
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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Open AccessArticle
The Decoloration of Anionic and Cationic Dyes Using ZnO and ZnO-Cu2O
Crystals 2019, 9(5), 229; https://doi.org/10.3390/cryst9050229 - 28 Apr 2019
Cited by 2
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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Open AccessArticle
Passivation Mechanism of Nitrogen in ZnO under Different Oxygen Ambience
Crystals 2019, 9(4), 204; https://doi.org/10.3390/cryst9040204 - 12 Apr 2019
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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