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Nanomaterials
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ZnO Nanorods: Synthesis, Characterization and Applications
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ZnO Nanorods: Synthesis, Characterization and Applications

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (30 June 2019) | Viewed by 13319

Special Issue Editor

Prof. Dr. Marwan Al-Haik

E-Mail Website
Guest Editor
Aerospace Engineering, Embry-Riddle Aeronautical University, Daytona Beach, USA
Interests: composite materials; nanomaterials; additive mnaufacturing; blast tolerant materials; radiation damage mitigation; thermal barrier coatings; high energy radiation detection; synthesis and characterization of lanthanides nanoparticles for gamma ray scintillators; synthesis of nanoparticles and WS2 nanofibers via plasma torch; synthesis of graphitic structures by design; processing of nanotube/polymer composites; magnetic annealing of engineering materials; residual stress development in super alloys; durability of polymeric composites; nanoindentation of thin films; nano impact and nano fatigue testing of thin films; thermomechanical analysis of polymers; light and electron microscopy and mechanical testing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The nanotechnology revolution ignited in-depth exploration of nanomaterials’ synthesis, characterization and potential applications. Among the leading semiconductor nanomaterials for the development of nanostructures and devices, Zinc Oxide (ZnO) has brought a tremendous impact to the electronics industry due to its multifaceted characteristics. This Special Issue is aimed at harvesting some of the recent and novel aspects of ZnO nanorods synthesis and applications. The motivation for this special issue stems from the recent applications of ZnO in several electronic devices such as transistors and transducers, energy harvesting devices and recent applications in structural composites as embedded structural health monitoring devices. While the research focusing on ZnO goes back several decades, the renewed interest is fueled by the novel synthesis techniques of Zno nanostructures and the tailorability of their microstructures and their emerging applications beyond the electronics sector. The Special Issue is envisioned to serve as a reference for students, researchers or other relevant personnel to promote the development of further research on this rather intriguing nanomaterial.

Prof. Marwan Al-Haik
Guest Editor

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 submissions that pass pre-check are 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. Nanomaterials is an international peer-reviewed open access semimonthly 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 2900 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 nanorods
  • synthesis
  • piezoelectric
  • composites
  • sensors
  • energy harvesting

Published Papers (4 papers)

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Research

18 pages, 4633 KiB  
Article
High-Performance Flexible Ultraviolet Photodetectors with Ni/Cu-Codoped ZnO Nanorods Grown on PET Substrates
by Hafiz Muhammad Salman Ajmal, Fasihullah Khan, Noor Ul Huda, Sunjung Lee, Kiyun Nam, Hae Young Kim, Tae-Hyong Eom and Sam Dong Kim
Nanomaterials 2019, 9(8), 1067; https://doi.org/10.3390/nano9081067 - 25 Jul 2019
Cited by 38 | Viewed by 4384
Abstract
As a developing technology for flexible electronic device fabrication, ultra-violet (UV) photodetectors (PDs) based on a ZnO nanostructure are an effective approach for large-area integration of sensors on nonconventional substrates, such as plastic or paper. However, photoconductive ZnO nanorods grown on flexible substrates [...] Read more.
As a developing technology for flexible electronic device fabrication, ultra-violet (UV) photodetectors (PDs) based on a ZnO nanostructure are an effective approach for large-area integration of sensors on nonconventional substrates, such as plastic or paper. However, photoconductive ZnO nanorods grown on flexible substrates have slow responses or recovery as well as low spectral responsivity R because of the native defects and inferior crystallinity of hydrothermally grown ZnO nanorods at low temperatures. In this study, ZnO nanorod crystallites are doped with Cu or Ni/Cu when grown on polyethylene terephthalate (PET) substrates in an attempt to improve the performance of flexible PDs. The doping with Ni/Cu or Cu not only improves the crystalline quality but also significantly suppresses the density of deep-level emission defects in as-grown ZnO nanorods, as demonstrated by X-ray diffraction and photoluminescence. Furthermore, the X-ray photoelectron spectroscopy analysis shows that doping with the transition metals significantly increases the oxygen bonding with metal ions with enhanced O/Zn stoichiometry in as-grown nanorods. The fabricated flexible PD devices based on an interdigitated electrode structure demonstrates a very high R of ~123 A/W, a high on-off current ratio of ~130, and a significant improvement in transient response speed exhibiting rise and fall time of ~8 and ~3 s, respectively, by using the ZnO nanorods codoped by Ni/Cu. Full article
(This article belongs to the Special Issue ZnO Nanorods: Synthesis, Characterization and Applications)
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15 pages, 12891 KiB  
Article
Antibacterial Application on Staphylococcus aureus Using Antibiotic Agent/Zinc Oxide Nanorod Arrays/Polyethylethylketone Composite Samples
by Dave W. Chen, Kuan-Yi Lee, Min-Hua Tsai, Tung-Yi Lin, Chien-Hao Chen and Kong-Wei Cheng
Nanomaterials 2019, 9(5), 713; https://doi.org/10.3390/nano9050713 - 08 May 2019
Cited by 22 | Viewed by 2759
Abstract
In this study, zinc oxide (ZnO) nanorod arrays as antibiotic agent carriers were grown on polyetheretherketone (PEEK) substrates using a chemical synthesis method. With the concentration of ammonium hydroxide in the precursor solution kept at 4 M, ZnO nanorod arrays with diameters in [...] Read more.
In this study, zinc oxide (ZnO) nanorod arrays as antibiotic agent carriers were grown on polyetheretherketone (PEEK) substrates using a chemical synthesis method. With the concentration of ammonium hydroxide in the precursor solution kept at 4 M, ZnO nanorod arrays with diameters in the range of 100–400 nm and a loading density of 1.7 mg/cm2 were grown onto the PEEK substrates. Their drug release profiles and the antibacterial properties of the antibiotic agent/ZnO/PEEK samples in the buffer solution were investigated. The results showed that the concentrations of antibiotic agents (ampicillin or vancomycin) released from the samples into the buffer solution were higher than the value of minimum inhibitory concentration of 90% for Staphylococcus aureus within the 96 h test. The bioactivities of ampicillin and vancomycin on substrates also showed around 40% and 80% on the Staphylococcus aureus, respectively. In the antibacterial activity test, sample with the suitable loading amount of antibiotic agent had a good inhibitory effect on the growth of Staphylococcus aureus. Full article
(This article belongs to the Special Issue ZnO Nanorods: Synthesis, Characterization and Applications)
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11 pages, 2942 KiB  
Communication
Growth Condition-Oriented Defect Engineering for Changes in Au–ZnO Contact Behavior from Schottky to Ohmic and Vice Versa
by Abu ul Hassan Sarwar Rana and Hyun-Seok Kim
Nanomaterials 2018, 8(12), 980; https://doi.org/10.3390/nano8120980 - 27 Nov 2018
Cited by 7 | Viewed by 2702
Abstract
ZnO has the built-in characteristics of both ionic and covalent compound semiconductors, which makes the metal–ZnO carrier transport mechanism quite intricate. The growth mechanism-centric change in ZnO defect density and carrier concentration also makes the contact formation and behavior unpredictable. This study investigates [...] Read more.
ZnO has the built-in characteristics of both ionic and covalent compound semiconductors, which makes the metal–ZnO carrier transport mechanism quite intricate. The growth mechanism-centric change in ZnO defect density and carrier concentration also makes the contact formation and behavior unpredictable. This study investigates the uncertainty in Au–ZnO contact behavior for application-oriented research and the development on ZnO nanostructures. Herein, we explain the phenomenon for how Au–ZnO contact could be rectifying or non-rectifying. Growth method-dependent defect engineering was exploited to explain the change in Schottky barrier heights at the Au–ZnO interface, and the change in device characteristics from Schottky to Ohmic and vice versa. The ZnO nanorods were fabricated via aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. For further investigations, one ACG sample was doped with Ga, and another was subjected to oxygen plasma treatment (OPT). The ACG and Ga-doped ACG samples showed a quasi-Ohmic and Ohmic behavior, respectively, because of a high surface and subsurface level donor defect-centric Schottky barrier pinning at the Au–ZnO interface. However, the ACG-OPT and MAG samples showed a more pronounced Schottky contact because of the presence of low defect-centric carrier concentration via MAG, and the removal of the surface accumulation layer via the OPT process. Full article
(This article belongs to the Special Issue ZnO Nanorods: Synthesis, Characterization and Applications)
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12 pages, 4526 KiB  
Article
Migration Energy Barriers for the Surface and Bulk of Self-Assembly ZnO Nanorods
by Feng-Ming Chang, Zhong-Zhe Wu, Jing-Heng Huang, Wei-Ting Chen, Sanjaya Brahma and Kuang Yao Lo
Nanomaterials 2018, 8(10), 811; https://doi.org/10.3390/nano8100811 - 09 Oct 2018
Cited by 5 | Viewed by 2684
Abstract
Post-annealing treatment is a necessary process to create/eliminate/repair defects in self–assembly (SA) metal oxide by providing enough thermal energy to the O atoms to overcome the migration energy barrier in ZnO. The height of migration energy barrier is dependent on the depth from [...] Read more.
Post-annealing treatment is a necessary process to create/eliminate/repair defects in self–assembly (SA) metal oxide by providing enough thermal energy to the O atoms to overcome the migration energy barrier in ZnO. The height of migration energy barrier is dependent on the depth from the surface, which is hard to be estimated by theoretical calculations, as well as the optical analyses. SA ZnO nanorods (ZNRs) have high surface-to-volume ratio to provide complete picture between the optical and surface properties obtained by photoluminescence (PL) and ultraviolet/X-ray photoemission spectroscopy (UPS/XPS), which is used to investigate the evolution of structure and chemical states of the surface layers to reveal mutual agreement on all observations in PL, XPS, and UPS. We demonstrate variation of the surface structure of SA-ZNRs by scanning over a range of annealing temperatures and time to regulate the structure variation of SA-ZNRs, and their optical analyses agrees well with PL, XPS and UPS, which indicates the dependence of migration energy barriers on the depth from the surface of ZNR. The results reveal the well ZNRs formed at 570 °C and the further oxidation process and the formation of hydroperoxide on the Zn-rich surface of ZNRs at 640 °C. Full article
(This article belongs to the Special Issue ZnO Nanorods: Synthesis, Characterization and Applications)
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