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14 pages, 3900 KiB

Open AccessArticle

A Simple Ball Milling and Thermal Oxidation Method for Synthesis of ZnO Nanowires Decorated with Cubic ZnO₂ Nanoparticles

by Antonio Rinaldi, Marialilia Pea, Andrea Notargiacomo, Eloisa Ferrone, Sebastiano Garroni, Luciano Pilloni and Rodolfo Araneo

Nanomaterials 2021, 11(2), 475; https://doi.org/10.3390/nano11020475 - 13 Feb 2021

Cited by 7 | Viewed by 2057

Abstract

In this work, we propose the synthesis of ZnO nanostructures through the thermal oxidation of ball-milled powders with the introduction of Mg and Sn doping species at the preliminary step of milling. We investigate the advantages and challenges of this two steps process [...] Read more.

In this work, we propose the synthesis of ZnO nanostructures through the thermal oxidation of ball-milled powders with the introduction of Mg and Sn doping species at the preliminary step of milling. We investigate the advantages and challenges of this two steps process for the production and fabrication of highly crystalline ZnO nanowires. This simple method allows us to fabricate ZnO nanowires with a higher quality core crystal at a much lower temperature and for a shorter processing time than the state-of-the-art, and decorated with by ZnO₂ nanoparticles as determined via TEM analysis. The main findings will show that the crystalline core of the nanowires is of hexagonal ZnO while the nanoparticles on the surface are ZnO₂ cubic type. Generally, the method proves to be suitable for applications that require a high surface-to-volume ratio, for example, catalysis phenomena, in which the presence of zinc oxides species can play an important role. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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10 pages, 3300 KiB

Open AccessEditor’s ChoiceArticle

Polarization Dependent Excitation and High Harmonic Generation from Intense Mid-IR Laser Pulses in ZnO

by Richard Hollinger, Paul Herrmann, Viacheslav Korolev, Maximilian Zapf, Valentina Shumakova, Robert Röder, Ingo Uschmann, Audrius Pugžlys, Andrius Baltuška, Michael Zürch, Carsten Ronning, Christian Spielmann and Daniil Kartashov

Nanomaterials 2021, 11(1), 4; https://doi.org/10.3390/nano11010004 - 22 Dec 2020

Cited by 9 | Viewed by 4301

Abstract

The generation of high order harmonics from femtosecond mid-IR laser pulses in ZnO has shown great potential to reveal new insight into the ultrafast electron dynamics on a few femtosecond timescale. In this work we report on the experimental investigation of photoluminescence and [...] Read more.

The generation of high order harmonics from femtosecond mid-IR laser pulses in ZnO has shown great potential to reveal new insight into the ultrafast electron dynamics on a few femtosecond timescale. In this work we report on the experimental investigation of photoluminescence and high-order harmonic generation (HHG) in a ZnO single crystal and polycrystalline thin film irradiated with intense femtosecond mid-IR laser pulses. The ellipticity dependence of the HHG process is experimentally studied up to the 17th harmonic order for various driving laser wavelengths in the spectral range 3–4 µm. Interband Zener tunneling is found to exhibit a significant excitation efficiency drop for circularly polarized strong-field pump pulses. For higher harmonics with energies larger than the bandgap, the measured ellipticity dependence can be quantitatively described by numerical simulations based on the density matrix equations. The ellipticity dependence of the below and above ZnO band gap harmonics as a function of the laser wavelength provides an efficient method for distinguishing the dominant HHG mechanism for different harmonic orders. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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11 pages, 2352 KiB

Open AccessArticle

Influence of PDA Coating on the Structural, Optical and Surface Properties of ZnO Nanostructures

by Daina Damberga, Viktoriia Fedorenko, Kārlis Grundšteins, Şahin Altundal, Andris Šutka, Arunas Ramanavičius, Emerson Coy, Radosław Mrówczyński, Igor Iatsunskyi and Roman Viter

Nanomaterials 2020, 10(12), 2438; https://doi.org/10.3390/nano10122438 - 06 Dec 2020

Cited by 24 | Viewed by 3171

Abstract

Polydopamine (PDA) is a new biocompatible material, which has prospects in biomedical and sensor applications. Due to functional groups, it can host wide range of biomolecules. ZnO nanostructures are well known templates for optical sensors and biosensors. The combination of ZnO and PDA [...] Read more.

Polydopamine (PDA) is a new biocompatible material, which has prospects in biomedical and sensor applications. Due to functional groups, it can host wide range of biomolecules. ZnO nanostructures are well known templates for optical sensors and biosensors. The combination of ZnO and PDA results in a change of optical properties of ZnO–PDA composites as a shift of photoluminescence (PL) peaks and PL quenching. However, to date, the effect of the PDA layer on fundamental properties of ZnO–PDA nanostructures has not been studied. The presented paper reports on optical and surface properties of novel ZnO–PDA nanocomposites. PDA layers were chemically synthesized on ZnO nanostructures from different solution concentrations of 0.3, 0.4, 0.5 and 0.7 mg/mL. Structure, electronic and optical properties were studied by SEM, Raman, FTIR, diffuse reflectance and photoluminescence methods. The Z-potential of the samples was evaluated in neutral pH (pH = 7.2). The response of the samples towards poly-l-lysine adsorption, as a model molecule, was studied by PL spectroscopy to evaluate the correlation between optical and surface properties. The role of the PDA concentration on fundamental properties was discussed. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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15 pages, 3901 KiB

Open AccessArticle

Biocompatibility and Antibacterial Properties of ZnO-Incorporated Anodic Oxide Coatings on TiZrNb Alloy

by Oleksandr Oleshko, Yevheniia Husak, Viktoriia Korniienko, Roman Pshenychnyi, Yuliia Varava, Oksana Kalinkevich, Marcin Pisarek, Karlis Grundsteins, Oksana Pogorielova, Oleg Mishchenko, Wojciech Simka, Roman Viter and Maksym Pogorielov

Nanomaterials 2020, 10(12), 2401; https://doi.org/10.3390/nano10122401 - 30 Nov 2020

Cited by 19 | Viewed by 2647

Abstract

In a present paper, we demonstrate novel approach to form ceramic coatings with incorporated ZnO nanoparticles (NPs) on low modulus TiZrNb alloy with enhanced biocompatibility and antibacterial parameters. Plasma Electrolytic Oxidation (PEO) was used to integrate ZnO nanoparticles (average size 12–27 nm), mixed [...] Read more.

In a present paper, we demonstrate novel approach to form ceramic coatings with incorporated ZnO nanoparticles (NPs) on low modulus TiZrNb alloy with enhanced biocompatibility and antibacterial parameters. Plasma Electrolytic Oxidation (PEO) was used to integrate ZnO nanoparticles (average size 12–27 nm), mixed with Ca(H₂PO₂)₂ aqueous solution into low modulus TiZrNb alloy surface. The TiZrNb alloys with integrated ZnO NPs successfully showed higher surface porosity and contact angle. XPS investigations showed presence of Ca ions and absence of phosphate ions in the PEO modified layer, what explains higher values of contact angle. Cell culture experiment (U2OS type) confirmed that the surface of as formed oxide-ZnO NPs demonstrated hydrophobic properties, what can affect primary cell attachment. Further investigations showed that Ca ions in the PEO coating stimulated proliferative activity of attached cells, resulting in competitive adhesion between cells and bacteria in clinical situation. Thus, high contact angle and integrated ZnO NPs prevent bacterial adhesion and considerably enhance the antibacterial property of TiZrNb alloys. A new anodic oxide coating with ZnO NPs could be successfully used for modification of low modulus alloys to decrease post-implantation complications. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 6498 KiB

Open AccessArticle

Synthesizing CuO/CeO₂/ZnO Ternary Nano-Photocatalyst with Highly Effective Utilization of Photo-Excited Carriers under Sunlight

by Kaiyi Luo, Jing Li, Wenyu Hu, Han Li, Qiuping Zhang, Huan Yuan, Fei Yu, Ming Xu and Shuyan Xu

Nanomaterials 2020, 10(10), 1946; https://doi.org/10.3390/nano10101946 - 29 Sep 2020

Cited by 20 | Viewed by 2924

Abstract

The construction of heterostructured photocatalyst with an appropriate energy band structure will help realize highly efficient photo-excited charge separation. In this study, ternary CuO/CeO₂/ZnO nano-particle (NP) composites were synthesized by a facile two-step sol-gel method, which exhibit significantly enhanced photocatalytic degradation [...] Read more.

The construction of heterostructured photocatalyst with an appropriate energy band structure will help realize highly efficient photo-excited charge separation. In this study, ternary CuO/CeO₂/ZnO nano-particle (NP) composites were synthesized by a facile two-step sol-gel method, which exhibit significantly enhanced photocatalytic degradation performance for various organic pollutants under UV and visible light excitation. The photo-responses to both UV and visible light, as well as the visible light absorption and utilization rates of ZnO are found to be synergistically intensified by CeO₂ and CuO co-coupling. The first-order kinetic constants (K) of 3%CuO/CeO₂/ZnO for methylene blue (MB) degradation are ~3.9, ~4.1 and ~4.8 times higher than ZnO under UV light, visible light and simulated sunlight illumination, respectively. The roles of CuO and CeO₂ in optical properties and photo-degradation under UV and visible light were explored. Besides, the photogenic holes (h⁺) of ZnO, CeO₂, and the produced hydroxyl radicals (·OH) are proved to be the main active species under UV light. Dissimilarly, under visible light, the superoxide radicals (·O₂⁻) formed by the reactions between oxygen molecules and the photo-generated electrons (e⁻) of CuO moving towards the catalysts surface are also found to be important for promoting dye decomposition. The improved photo-responses, the well-matched band structure that facilitates charge transfer processes, and the highly efficient utilization of the photo-excited carriers of the ternary nano-heterostructure are suggested to be the key factors for the remarkable enhancement of photocatalytic performance of ZnO nano-photocatalyst. This work offers a low-cost strategy to acquire highly active UV and visible light-driven photocatalyst. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 4445 KiB

Open AccessArticle

Highly Sensitive UV Photodiode Composed of β-Polyfluorene/YZnO Nanorod Organic-Inorganic Hybrid Heterostructure

by Youngmin Lee, Soo Youn Kim, Deuk Young Kim and Sejoon Lee

Nanomaterials 2020, 10(8), 1486; https://doi.org/10.3390/nano10081486 - 29 Jul 2020

Cited by 8 | Viewed by 2453

Abstract

The highly sensitive ultra-violet (UV) photodiode was demonstrated on the organic-inorganic hybrid heterostructure of β-phase p-type polyfluorene (PFO)/n-type yttrium-doped zinc oxide nanorods (YZO-NRs). The device was fabricated through a simple fabrication technique of β-phase PFO coating onto YZO-NRs that had been directly grown [...] Read more.

The highly sensitive ultra-violet (UV) photodiode was demonstrated on the organic-inorganic hybrid heterostructure of β-phase p-type polyfluorene (PFO)/n-type yttrium-doped zinc oxide nanorods (YZO-NRs). The device was fabricated through a simple fabrication technique of β-phase PFO coating onto YZO-NRs that had been directly grown on graphene by the hydrothermal synthesis method. Under UV illumination (λ = 365 nm), the device clearly showed excellent photoresponse characteristics (e.g., high quantum efficiency ~690%, high photodetectivity ~3.34 × 10¹² cm·Hz^1/2·W⁻¹, and fast response time ~0.17 s). Furthermore, the ratio of the photo current-to-dark current exceeds 10³ even under UV illumination with a small optical power density of 0.6 mW/cm². We attribute such superb photoresponse characteristics to both Y incorporation into YZO-NRs and conformation of β-phase PFO. Namely, Y dopants could effectively reduce surface states at YZO-NRs, and β-phase PFO might increase the photocarrier conductivity in PFO. The results suggest that the β-phase p-PFO/n-YZO-NR hybrid heterostructure holds promise for high-performance UV photodetectors. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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15 pages, 3581 KiB

Open AccessArticle

Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets

by Yuan-Chang Liang, Chen-Shiang Hung and Wei-Cheng Zhao

Nanomaterials 2020, 10(7), 1352; https://doi.org/10.3390/nano10071352 - 11 Jul 2020

Cited by 23 | Viewed by 2697

Abstract

Porous ZnO sheets containing various degrees of a nanoscaled pore were successfully synthesized using a simple hydrothermal method and various postannealing procedures. The porosity features of the ZnO sheets can be easily tuned by changing both the annealing temperature and annealing atmosphere. The [...] Read more.

Porous ZnO sheets containing various degrees of a nanoscaled pore were successfully synthesized using a simple hydrothermal method and various postannealing procedures. The porosity features of the ZnO sheets can be easily tuned by changing both the annealing temperature and annealing atmosphere. The dense porous nature of ZnO sheets is beneficial to enhance light absorption. Moreover, the substantially increased oxygen vacancies in the ZnO sheets were observed especially after the hydrogen treatment as revealed in the X-ray photoelectron spectroscope and photoluminescence analyses. The high density of surface crystal defect enhanced the photoinduced electron-hole separation rate of the ZnO sheets, which is crucial for an improved photoactivity. The porous ZnO sheets formed at a hydrogen atmosphere exhibited superior photoactive performance than the porous ZnO sheets formed at the high-temperature ambient air annealing. The dense pores and massive crystal defects formed by a hydrogen atmosphere annealing in the ZnO crystals might account for the observed photoactive behaviors in this study. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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20 pages, 3928 KiB

Open AccessArticle

Ultraviolet Photodetection Based on High-Performance Co-Plus-Ni Doped ZnO Nanorods Grown by Hydrothermal Method on Transparent Plastic Substrate

by Hafiz Muhammad Salman Ajmal, Fasihullah Khan, Kiyun Nam, Hae Young Kim and Sam Dong Kim

Nanomaterials 2020, 10(6), 1225; https://doi.org/10.3390/nano10061225 - 23 Jun 2020

Cited by 42 | Viewed by 3204

Abstract

A growth scheme at a low processing temperature for high crystalline-quality of ZnO nanostructures can be a prime stepping stone for the future of various optoelectronic devices manufactured on transparent plastic substrates. In this study, ZnO nanorods (NRs) grown by the hydrothermal method [...] Read more.

A growth scheme at a low processing temperature for high crystalline-quality of ZnO nanostructures can be a prime stepping stone for the future of various optoelectronic devices manufactured on transparent plastic substrates. In this study, ZnO nanorods (NRs) grown by the hydrothermal method at 150 °C through doping of transition metals (TMs), such as Co, Ni, or Co-plus-Ni, on polyethylene terephthalate substrates were investigated by various surface analysis methods. The TM dopants in ZnO NRs suppressed the density of various native defect-states as revealed by our photoluminescence and X-ray photoelectron spectroscopy analysis. Further investigation also showed the doping into ZnO NRs brought about a clear improvement in carrier mobility from 0.81 to 3.95 cm²/V-s as well as significant recovery in stoichiometric contents of oxygen. Ultra-violet photodetectors fabricated with Co-plus-Ni codoped NRs grown on an interdigitated electrode structure exhibited a high spectral response of ~137 A/W, on/off current ratio of ~135, and an improvement in transient response speed with rise-up and fall-down times of ~2.2 and ~3.1 s, respectively. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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25 pages, 3011 KiB

Open AccessArticle

Zinc Oxide Nanoparticles Damage Tobacco BY-2 Cells by Oxidative Stress Followed by Processes of Autophagy and Programmed Cell Death

by Ľudmila Balážová, Matej Baláž and Petr Babula

Nanomaterials 2020, 10(6), 1066; https://doi.org/10.3390/nano10061066 - 30 May 2020

Cited by 24 | Viewed by 2889

Abstract

Nanomaterials, including zinc oxide nanoparticles (ZnO NPs), have a great application potential in many fields, such as medicine, the textile industry, electronics, and cosmetics. Their impact on the environment must be carefully investigated and specified due to their wide range of application. However, [...] Read more.

Nanomaterials, including zinc oxide nanoparticles (ZnO NPs), have a great application potential in many fields, such as medicine, the textile industry, electronics, and cosmetics. Their impact on the environment must be carefully investigated and specified due to their wide range of application. However, the amount of data on possible negative effects of ZnO NPs on plants at the cellular level are still insufficient. Thus, we focused on the effect of ZnO NPs on tobacco BY-2 cells, i.e., a widely accepted plant cell model. Adverse effects of ZnO NPs on both growth and biochemical parameters were observed. In addition, reactive oxygen and nitrogen species visualizations confirmed that ZnO NPs may induce oxidative stress. All these changes were associated with the lipid peroxidation and changes in the plasma membrane integrity, which together with endoplasmatic reticulum and mitochondrial dysfunction led to autophagy and programmed cell death. The present study demonstrates that the phytotoxic effect of ZnO NPs on the BY-2 cells is very complex and needs further investigation. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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18 pages, 9371 KiB

Open AccessArticle

Synthesis and Memristor Effect of a Forming-Free ZnO Nanocrystalline Films

by Roman V. Tominov, Zakhar E. Vakulov, Vadim I. Avilov, Daniil A. Khakhulin, Aleksandr A. Fedotov, Evgeny G. Zamburg, Vladimir A. Smirnov and Oleg A. Ageev

Nanomaterials 2020, 10(5), 1007; https://doi.org/10.3390/nano10051007 - 25 May 2020

Cited by 25 | Viewed by 3399

Abstract

We experimentally investigated the effect of post-growth annealing on the morphological, structural, and electrophysical parameters of nanocrystalline ZnO films fabricated by pulsed laser deposition. The influence of post-growth annealing modes on the electroforming voltage and the resistive switching effect in ZnO nanocrystalline films [...] Read more.

We experimentally investigated the effect of post-growth annealing on the morphological, structural, and electrophysical parameters of nanocrystalline ZnO films fabricated by pulsed laser deposition. The influence of post-growth annealing modes on the electroforming voltage and the resistive switching effect in ZnO nanocrystalline films is investigated. We demonstrated that nanocrystalline zinc oxide films, fabricated at certain regimes, show the electroforming-free resistive switching. It was shown, that the forming-free nanocrystalline ZnO film demonstrated a resistive switching effect and switched at a voltage 1.9 ± 0.2 V from 62.42 ± 6.47 (R_HRS) to 0.83 ± 0.06 kΩ (R_LRS). The influence of ZnO surface morphology on the resistive switching effect is experimentally investigated. It was shown, that the ZnO nanocrystalline film exhibits a stable resistive switching effect, which is weakly dependent on its nanoscale structure. The influence of technological parameters on the resistive switching effect in a forming-free ZnO nanocrystalline film is investigated. The results can be used for fabrication of new-generation micro- and nanoelectronics elements, including random resistive memory (ReRAM) elements for neuromorphic structures based on forming-free ZnO nanocrystalline films. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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12 pages, 1913 KiB

Open AccessArticle

Atomic Layer Deposition of ZnO on Mesoporous Silica: Insights into Growth Behavior of ZnO via In-Situ Thermogravimetric Analysis

by Piyush Ingale, Kristian Knemeyer, Mar Piernavieja Hermida, Raoul Naumann d’Alnoncourt, Arne Thomas and Frank Rosowski

Nanomaterials 2020, 10(5), 981; https://doi.org/10.3390/nano10050981 - 20 May 2020

Cited by 15 | Viewed by 3847

Abstract

ZnO is a remarkable material with many applications in electronics and catalysis. Atomic layer deposition (ALD) of ZnO on flat substrates is an industrially applied and well-known process. Various studies describe the growth of ZnO layers on flat substrates. However, the growth characteristics [...] Read more.

ZnO is a remarkable material with many applications in electronics and catalysis. Atomic layer deposition (ALD) of ZnO on flat substrates is an industrially applied and well-known process. Various studies describe the growth of ZnO layers on flat substrates. However, the growth characteristics and reaction mechanisms of atomic layer deposition of ZnO on mesoporous powders have not been well studied. This study investigates the ZnO ALD process based on diethylzinc (DEZn) and water with silica powder as substrate. In-situ thermogravimetric analysis gives direct access to the growth rates and reaction mechanisms of this process. Ex-situ analytics, e.g., N₂ sorption analysis, XRD, XRF, HRTEM, and STEM-EDX mapping, confirm deposition of homogenous and thin films of ZnO on SiO₂. In summary, this study offers new insights into the fundamentals of an ALD process on high surface area powders. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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22 pages, 5603 KiB

Open AccessArticle

Seedless Hydrothermal Growth of ZnO Nanorods as a Promising Route for Flexible Tactile Sensors

by Ilaria Cesini, Magdalena Kowalczyk, Alessandro Lucantonio, Giacomo D’Alesio, Pramod Kumar, Domenico Camboni, Luca Massari, Pasqualantonio Pingue, Antonio De Simone, Alessandro Fraleoni Morgera and Calogero Maria Oddo

Nanomaterials 2020, 10(5), 977; https://doi.org/10.3390/nano10050977 - 19 May 2020

Cited by 14 | Viewed by 3923

Abstract

Hydrothermal growth of ZnO nanorods has been widely used for the development of tactile sensors, with the aid of ZnO seed layers, favoring the growth of dense and vertically aligned nanorods. However, seed layers represent an additional fabrication step in the sensor design. [...] Read more.

Hydrothermal growth of ZnO nanorods has been widely used for the development of tactile sensors, with the aid of ZnO seed layers, favoring the growth of dense and vertically aligned nanorods. However, seed layers represent an additional fabrication step in the sensor design. In this study, a seedless hydrothermal growth of ZnO nanorods was carried out on Au-coated Si and polyimide substrates. The effects of both the Au morphology and the growth temperature on the characteristics of the nanorods were investigated, finding that smaller Au grains produced tilted rods, while larger grains provided vertical rods. Highly dense and high-aspect-ratio nanorods with hexagonal prismatic shape were obtained at 75 °C and 85 °C, while pyramid-like rods were grown when the temperature was set to 95 °C. Finite-element simulations demonstrated that prismatic rods produce higher voltage responses than the pyramid-shaped ones. A tactile sensor, with an active area of 1 cm², was fabricated on flexible polyimide substrate and embedding the nanorods forest in a polydimethylsiloxane matrix as a separation layer between the bottom and the top Au electrodes. The prototype showed clear responses upon applied loads of 2–4 N and vibrations over frequencies in the range of 20–800 Hz. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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11 pages, 2998 KiB

Open AccessArticle

Remarkable Stability Improvement of ZnO TFT with Al₂O₃ Gate Insulator by Yttrium Passivation with Spray Pyrolysis

by Jewel Kumer Saha, Ravindra Naik Bukke, Narendra Naik Mude and Jin Jang

Nanomaterials 2020, 10(5), 976; https://doi.org/10.3390/nano10050976 - 19 May 2020

Cited by 32 | Viewed by 4228

Abstract

We report the impact of yttrium oxide (YO_x) passivation on the zinc oxide (ZnO) thin film transistor (TFT) based on Al₂O₃ gate insulator (GI). The YO_x and ZnO films are both deposited by spray pyrolysis at 400 [...] Read more.

We report the impact of yttrium oxide (YO_x) passivation on the zinc oxide (ZnO) thin film transistor (TFT) based on Al₂O₃ gate insulator (GI). The YO_x and ZnO films are both deposited by spray pyrolysis at 400 and 350 °C, respectively. The YO_x passivated ZnO TFT exhibits high device performance of field effect mobility (μ_FE) of 35.36 cm²/Vs, threshold voltage (V_TH) of 0.49 V and subthreshold swing (SS) of 128.4 mV/dec. The ZnO TFT also exhibits excellent device stabilities, such as negligible threshold voltage shift (∆V_TH) of 0.15 V under positive bias temperature stress and zero hysteresis voltage (V_H) of ~0 V. YO_x protects the channel layer from moisture absorption. On the other hand, the unpassivated ZnO TFT with Al₂O₃ GI showed inferior bias stability with a high SS when compared to the passivated one. It is found by XPS that Y diffuses into the GI interface, which can reduce the interfacial defects and eliminate the hysteresis of the transfer curve. The improvement of the stability is mainly due to the diffusion of Y into ZnO as well as the ZnO/Al₂O₃ interface. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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12 pages, 2427 KiB

Open AccessArticle

Green and Economic Fabrication of Zinc Oxide (ZnO) Nanorods as a Broadband UV Blocker and Antimicrobial Agent

by Seyedeh-Masoumeh Taghizadeh, Neha Lal, Alireza Ebrahiminezhad, Fatemeh Moeini, Mostafa Seifan, Younes Ghasemi and Aydin Berenjian

Nanomaterials 2020, 10(3), 530; https://doi.org/10.3390/nano10030530 - 15 Mar 2020

Cited by 68 | Viewed by 4343

Abstract

Zinc oxide (ZnO) nanoparticles have gained widespread interest due to their unique properties, making them suitable for a range of applications. Several methods for their production are available, and of these, controlled synthesis techniques are particularly favourable. Large-scale culturing of Chlorella vulgaris produces [...] Read more.

Zinc oxide (ZnO) nanoparticles have gained widespread interest due to their unique properties, making them suitable for a range of applications. Several methods for their production are available, and of these, controlled synthesis techniques are particularly favourable. Large-scale culturing of Chlorella vulgaris produces secretory carbohydrates as a waste product, which have been shown to play an important role in directing the particle size and morphology of nanoparticles. In this investigation, ZnO nanorods were produced through a controlled synthesis approach using secretory carbohydrates from C. vulgaris, which presents a cost-effective and sustainable alternative to the existing techniques. Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) analysis, transmission electron microscopy (TEM), and UV-Vis spectroscopy were used to characterise the nanorods. The prepared nanorods exhibited a broad range of UV absorption, which suggests that the particles are a promising broadband sun blocker and are likely to be effective for the fabrication of sunscreens with protection against both UVB (290–320 nm) and UVA (320–400 nm) radiations. The antimicrobial activity of the prepared nanorods against Gram-positive and Gram-negative bacteria was also assessed. The nanostructures had a crystalline structure and rod-like appearance, with an average length and width of 150 nm and 21 nm, respectively. The nanorods also demonstrated notable antibacterial activity, and 250 μg/mL was determined to be the most effective concentration. The antibacterial properties of the ZnO nanorods suggest its suitability for a range of antimicrobial uses, such as in the food industry and for various biomedical applications. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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Review

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150 pages, 44868 KiB

Open AccessReview

A Review of Microwave Synthesis of Zinc Oxide Nanomaterials: Reactants, Process Parameters and Morphologies

by Jacek Wojnarowicz, Tadeusz Chudoba and Witold Lojkowski

Nanomaterials 2020, 10(6), 1086; https://doi.org/10.3390/nano10061086 - 31 May 2020

Cited by 219 | Viewed by 32857

Abstract

Zinc oxide (ZnO) is a multifunctional material due to its exceptional physicochemical properties and broad usefulness. The special properties resulting from the reduction of the material size from the macro scale to the nano scale has made the application of ZnO nanomaterials (ZnO [...] Read more.

Zinc oxide (ZnO) is a multifunctional material due to its exceptional physicochemical properties and broad usefulness. The special properties resulting from the reduction of the material size from the macro scale to the nano scale has made the application of ZnO nanomaterials (ZnO NMs) more popular in numerous consumer products. In recent years, particular attention has been drawn to the development of various methods of ZnO NMs synthesis, which above all meet the requirements of the green chemistry approach. The application of the microwave heating technology when obtaining ZnO NMs enables the development of new methods of syntheses, which are characterised by, among others, the possibility to control the properties, repeatability, reproducibility, short synthesis duration, low price, purity, and fulfilment of the eco-friendly approach criterion. The dynamic development of materials engineering is the reason why it is necessary to obtain ZnO NMs with strictly defined properties. The present review aims to discuss the state of the art regarding the microwave synthesis of undoped and doped ZnO NMs. The first part of the review presents the properties of ZnO and new applications of ZnO NMs. Subsequently, the properties of microwave heating are discussed and compared with conventional heating and areas of application are presented. The final part of the paper presents reactants, parameters of processes, and the morphology of products, with a division of the microwave synthesis of ZnO NMs into three primary groups, namely hydrothermal, solvothermal, and hybrid methods. Full article

(This article belongs to the Special Issue ZnO Based Nanostructures: Synthesis, Characterization and Applications)

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