Metal Zinc Oxide Research Articles

Zinc Oxide Defect Microstructure and Surface Chemistry Derived from Oxidation of Metallic Zinc: Thin-Film Transistor and Sensor Behavior of ZnO Films and Rods.

Zinc oxide thin films are fabricated by controlled oxidation of sputtered zinc metal films on a hotplate in air at temperatures between 250 and 450 °C. The nanocrystalline films possess high relative densities and show preferential growth in (100) orientation. Integration in thin‐film transistors reveals moderate charge carrier mobilities as high as 0.2 cm2 V−1s−1. The semiconducting properties depend on the calcination temperature, whereby the best performance is achieved at 450 °C. The defect structure of the thin ZnO film can be tracked by Doppler‐broadening positron annihilation spectroscopy as well as positron lifetime studies. Comparably long positron lifetimes suggest interaction of zinc vacancies (VZn) with one or more oxygen vacancies (VO) in larger structural entities. Such VO‐VZn defect clusters act as shallow acceptors, and thus, reduce the overall electron conductivity of the film. The concentration of these defect clusters decreases at higher calcination temperatures as indicated by changes in the S and W parameters. Such zinc oxide films obtained by conversion of metallic zinc can also be used as seed layers for solution deposition of zinc oxide nanowires employing a mild microwave‐assisted process. The functionality of the obtained nanowire arrays is tested in a UV sensor device. The best results with respect to sensor sensitivity are achieved with thinner seed layers for device construction.

Latest Novelties on Plasmonic and Non-Plasmonic Nanomaterials for SERS Sensing.

An explosion in the production of substrates for surface enhanced Raman scattering (SERS) has occurred using novel designs of plasmonic nanostructures (e.g., nanoparticle self-assembly), new plasmonic materials such as bimetallic nanomaterials (e.g., Au/Ag) and hybrid nanomaterials (e.g., metal/semiconductor), and new non-plasmonic nanomaterials. The novel plasmonic nanomaterials can enable a better charge transfer or a better confinement of the electric field inducing a SERS enhancement by adjusting, for instance, the size, shape, spatial organization, nanoparticle self-assembly, and nature of nanomaterials. The new non-plasmonic nanomaterials can favor a better charge transfer caused by atom defects, thus inducing a SERS enhancement. In last two years (2019–2020), great insights in the fields of design of plasmonic nanosystems based on the nanoparticle self-assembly and new plasmonic and non-plasmonic nanomaterials were realized. This mini-review is focused on the nanoparticle self-assembly, bimetallic nanoparticles, nanomaterials based on metal-zinc oxide, and other nanomaterials based on metal oxides and metal oxide-metal for SERS sensing.

Oxidative ionothermal synthesis for micro and macro Zn-based materials

Zn-Based materials produced by direct oxidation of metallic zinc in aqueous [C4C1im]Cl solutions.

Anticancer and genotoxicity effect of (Clausena lansium (Lour.) Skeels) Peel ZnONPs on neuroblastoma (SH-SY5Y) cells through the modulation of autophagy mechanism

Nanotechnology is an emerged field to develop the plant mediated metal based nanodrugs by green method. In this current study, the zinc oxide metal based nanoparticles were developed using (Clausena lansium (Lour.) Skeels) Peel aqueous extracts and zinc nitrate. The C.L extract zinc nanoparticleswere indicated by the sharp peak seen at 350 nm utilizing the Ultraviolet–Visible spectroscopy (UV–Vis). The high peaks indicate the presence of phytochemicals and its functional groups in ZnONPs were studied by the Fourier Transform Infrared Spectroscopy (FT-IR). The X-Ray Diffraction analysis (XRD) explores the pattern and structure of ZnONPs as spherical and base-centered monoclinic crystalline shapes. The C.L extract with Zn nanoparticles were spherical in nature and the size of the synthesized particles were about 28.42 nm respectively. The autophagy (Beclin-1, LC3-I, LC3-II and ATG4B) and apoptotic (Bax, Bcl-2 and Caspase-3) proteins were regulated by the treatment with ZnONPs in SH-SY5Y neuroblastoma cells. The DNA loss or damage was occurred in the ZnONPs treatment and it was performed using Comet assay. The ZnONPs treatment generates the ROS in the cells and decreased its stability and viability. Addition of NAC prevents ROS in the cultured SH-SY5Y cells and prevents the cells from the apoptosis. We concluded that the ZnONPs potentially kills the neuroblastoma cells by producing the intracellular ROS.

Electrochemical synthesis and characterization of dark nanoporous zinc oxide films

Dark nanoporous layers of zinc oxide were obtained by simple anodic oxidation of metallic zinc and characterized by various physicochemical methods. Anodization was performed in 1 M NaOH electrolyte at the potentials of 2 V, or 4 V. All processes were carried out for 30 min at room temperature without stirring of the electrolyte. Selected samples were annealed in air at 200 °C for 2 h. The characterization of morphology and composition of as obtained materials was performed. It was confirmed that such kind of anodic films were porous in nature and exhibited a sponge-like morphology, rather than a channel-like structure typically observed in other types of anodic oxides. XRD, XPS and Raman spectroscopy confirmed that ZnO was obtained directly during anodization. Moreover, it was found out that the material was highly disordered with a high amount of oxygen vacancies and zinc interstitials, despite the applied anodizing potential. However, a significant improvement in the crystallinity of ZnO was achieved due to the annealing process for the samples anodized at higher potential. The UV–Vis spectroscopy confirmed the low reflectance of the obtained layers related to their black color. The hydrophilic character of the layers was confirmed by contact angle measurements. The characterization of porous ZnO films confirmed both a high surface area and strong absorption of the visible light that can be utilized in photoelectrochemical and photocatalytic applications.

Spectroscopic and FMO Studies of Cholesteryl Stereate Complexes for Electrooptical Activity

Computational studies have attracted the attention of researchers to understand the structural behavior of the molecules. These methods grade complex systems for novel properties with new predictions in areas of physics, chemistry and biology useful for conduct of experimental studies. Nanoparticles in present day technologies have become integral part in diverse areas of science mostly with metal oxide nanoparticles. To understand the role of nanoparticles in physicochemical process, iron, zinc, aluminum and copper oxide nano particles were conjugated with cholesteryl stereate in formation of complexes with ultrasonication. Infrared and Raman spectra confirm bonding between cholesteryl stereate and metal oxide nanoparticles. Computational studies of cholesteryl stereate complexes with Gaussian 03 were analyzed for deterministic properties i.e. dipole moment, energy gap, electrophilicity index, polarisability and first order hyperpolarizability that are responsible for electrooptical activity. Interestingly iron oxide and zinc oxide metal nano particles has significant contribution in electrooptical activity than copper and aluminum oxide nano particles.

A Novel Approach of In-Situ Electrobiosynthesis of Metal Oxide Nanoparticles Using Crude Plant Extract as Main Medium for Supporting Electrolyte

Abstract The release of dyes into the environment during textile fibre dyeing and finishing processes is a main source of water pollution. There is a need to look for effective treatment processes to overcome this problem. Photocatalytic method becomes the most effective to remove the dyes. In this study, in-situ electrobiosynthesis of various metal oxide such as silver oxide (AgO), copper oxide (CuO), zinc oxide (ZnO), and nickel oxide (NiO) using plant extract as new green electrolyte was performed with enhancement behaviour and structural of the catalyst for excellent photodegradation of malachite green (MG) dye from aqueous solution. The MG was successfully degraded at optimum condition of 10 mg/L of initial concentration with 0.5 g/L of catalyst dosage of AgO, CuO, ZnO, and NiO; at pH of 2 under visible light irradiation within 1 hour of contact time at room temperature which were 91.7 %, 94.0%, 98.5 %, and 97.3 %, respectively. Therefore, the effectiveness of eelctrobiosynthesis of AgO, CuO, ZnO, and NiO metal catalyst via electrochemical method using 100 % crude plant extract as new supporting electrolyte was established and confirmed through this study. The synthesized metal oxide catalyst has a great potential as a photocatalyst in photocatalytic reaction for degradation of organic pollutants in wastewater.

Exploring the Carrier Dynamics in Zinc Oxide–Metal Halide-Based Perovskite Nanostructures: Toward Reduced Dielectric Loss and Improved Photocurrent

Metal halide-based perovskites have emerged as a potential candidate for optoelectronic applications because of their impressive performance achieved by tuning the optical/electrical properties through tailoring the perovskite nanostructures. Herein, we report the synthesis of composite nanostructures by incorporation of ZnO (∼6 nm) into the CsPbBr3 (CPB) perovskite framework, which shows significant enhancement of photocurrent because of efficient interfacial charge separation and reduced dielectric loss. Detailed steady-state and time-resolved photoluminescence studies have been carried out to understand charge transfer dynamics in the CsPbBr3/ZnO nanostructure composite system. Femtosecond transient absorption and broadband dielectric spectroscopy studies were carried out to determine the charge carrier relaxation and transfer mechanism. The redox energy-level diagram suggests that the photoexcited electron from the conduction band (CB) of CPB can be transferred to the CB of ZnO NP because of thermodyn...

Biosynthesis, characterization and antimicrobial activities of zinc oxide nanoparticles from leaf extract of Glycosmis pentaphylla (Retz.) DC

Biosynthesized nanoparticles have an incredible application in biomedicine owing to its simplicity, eco-friendly properties and low cost. The present study aims to determine the green synthesized zinc oxide nanoparticles from methanolic leaf extract of Glycosmis pentaphylla. The synthesized nanoparticles were characterized using UV-VIS Spectroscopy, Fluorescence spectrometer, FT-IR, XRD, SEM with EDAX and TEM. The confirmations of synthesized nanoparticles were characterized by peak at 351 and 410 nm in the UV-VIS spectrum and photoluminescence spectrum respectively. FT-IR studies revealed the functional group of the nanoparticles. The XRD data showed the crystalline nature of the nanoparticles and EDAX measurements indicated the 20.70% of highly pure zinc oxide metal. The morphological characterization of synthesized zinc oxide nanoparticles was analyzed by SEM and TEM and size of the particles were ranging from 32 to 36 nm. The synthesized zinc oxide nanoparticles exhibited interesting antimicrobial activity against pathogenic organisms. In addition, this is the first report on leaf mediated synthesis of zinc oxide (ZnO) nanoparticles from Glycosmis pentaphylla.

Bioinspired self-standing macroporous Au/ZnO sponges for enhanced photocatalysis

A self-standing macroporous noble metal-zinc oxide (ZnO) sponge of robust 3D network has been fabricated through in-situ growth method. The key to the construction of the bioinspired sponge lies in the choice of commercial polyurethane sponge (CPS) with interconnected and junction-free macroporous structure as the skeleton to support Au/ZnO nanorods (Au/ZnONRs). The resultant Au/ZnO/CPS not only exhibits hierarchical structures representing physical features of CPS, but also demonstrates durable superior photocatalytic activity and hydrogen generation capability. In addition, we have adopted various irradiations to investigate the effect of UV light and visible light on the photocatalytic performance of Au/ZnO/CPS individually. In detail, the photocatalytic properties of Au/ZnO/CPS and ZnO/CPS have been monitored and compared under irradiations of different wavelengths (200–1100, 350–780, 200–420 and 420–780 nm) for 90 min to reveal the effect of irradiation wavelength on the activity of photocatalysts. A possible mechanism between irradiation wavelength and photocatalytic degradation efficiency is proposed. The facile in-situ growth approach presented herein can be easily scaled up, affording a convenient method for the preparation of self-standing 3D macroporous materials, which holds great potential for the application in both environmental purification and solar-to-hydrogen energy conversion.

Study of polymorphism using patterned self-assembled monolayers approach on metal substrates

Polymorphism is a molecule’s ability to possess altered physical crystalline structures and has become an active interest in pharmaceuticals due to its ability to influence a drug’s physical and chemical properties. Crystal stability and solubility are crucial in determining a drug’s pharmacokinetics and pharmacodynamics. Changes in these properties due to polymorphisms have contributed to recalls and modifications in industrial production. For this study, the effects of surface interactions with pharmaceuticals were examined through surface modification methodology using organic phosphonic and sulfonic acid self-assembled monolayers (SAMs) developed on a nickel or zinc oxide metal substrate. Drugs analyzed included carbamazepine, cimetidine, tolfenamic acid, and flufenamic acid. All drugs were thermodynamically applied to the reformed surface to aid in recrystallization. It was hypothesized and confirmed that intermolecular bonds, especially hydrogen bonds between the SAMs and pharmaceutical drugs, were the force that assisted in polymorph development. The study was successful in revealing multiple forms for each drug, including their commercial form and at least one additional form using micro FT-IR, Raman spectroscopy, and PXRD. Visual comparisons of crystal polymorphisms were performed with IR microscopy.

Fully solution-processed zinc oxide MIS capacitors by ultrasonic spray pyrolysis in air ambient

In this work, the fabrication and characterization of fully solution-processed zinc oxide metal–insulator–semiconductor (MIS) capacitors by ultrasonic spray pyrolysis (USP) are presented. Fluorine tin oxide by USP was used as transparent electrode, while spin-on glass by spin-coatingwas used as dielectric and zinc oxide by USP was used as active layer. Also, the zinc oxide film was characterized using photoluminescence spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The MIS capacitors were fabricated over glass slides and were highly transparent in the visible range, which makes their use feasible in transparent electronics. Employing capacitance–voltage and current–voltage measurements, the MIS capacitors were characterized.

Visible-blind ultraviolet photodiode fabricated by UV oxidation of metallic zinc on p-Si

A UV photodiode fabricated by the UV oxidation of a metallic zinc thin film on p-Si has manifested unique photoresponse characteristics. The electron concentration found by the Hall measurement was 3 × 1016 cm−3, and such a low electron concentration resulted in a low visible photoluminescence. UV illumination enhances the oxidation at low temperatures and decreases the concentration of the oxygen vacancies. The I-V characteristic showed a good rectification with a four-order magnitude difference in the forward and reverse currents at 2 V, and its linear and frequency independent C−2–V characteristic confirmed an abrupt pn junction. The photoresponse showed a visible blindness with a responsivity ratio of UV and visible light as high as 100. Such a visible-blind photoresponse was attributed to the optimum thickness of the SiO2 formed on the Si surface during the UV oxidation at 400 °C. A lower potential barrier to holes at the ZnO/SiO2 interface facilitates Fowler-Nordheim tunneling of the photo-generated holes during the UV illumination, while a higher potential barrier to electrons efficiently blocks transport of the photo-generated electrons to the ZnO during the visible light illumination. The presence of oxide resulted in a slow photoresponse to the turn-on and off of the UV light. A detailed analysis is presented to understand how the photo-generated carriers contribute step by step to the photocurrent. In addition to the slow photoresponse associated with the SiO2 interfacial layer, the decay of the photocurrent was found extremely slow after turn-off of the UV light. Such a slow decay of the photocurrent is referred to as a persistent photoconductivity, which is caused by metastable deep levels. It is hypothesized that Zn vacancies form such a deep level, and that the photo-generated electrons need to overcome a thermal-energy barrier for capture. The ZnO film by the UV oxidation at 400 °C was found to be rich in oxygen and deficient in zinc.

Gas-phase synthesis of zinc oxide nanorods

Gas-phase synthesis of zinc oxide (ZnO) nanorods on silicon and glass substrates has been studied. Using the proposed method, arrays of ZnO nanorods can be grown on these substrates without preliminary deposition of a thin ZnO sublayer and/or metal catalyst. The influence of the temperature regime, substrate arrangement, and growth time on the synthesis is considered. The shape, dimensions, and orientation of nanorods have been studied by electron microscopy and X-ray diffraction. Luminescence spectra and X-ray diffraction patterns of oriented arrays of nanorods have been investigated.

Mechanochemical synthesis of zinc oxides with the use of liquid and gaseous media

X-ray phase analysis, thermogravimetry, and volumometry were used to study the mechanochemical synthesis of zinc oxide. The conversion of metallic zinc was calculated in relation to the time and method of mechanical activation and to the oxidizing medium used. The most optimal conditions of oxidation of metallic zinc were determined.

In brief

PAGE 105 The transient off-state thermal emission leakage currents of hydrogenated amorphous silicon and indium gallium zinc oxide metal oxide thin-film transistors fabricated on flexible plastic substrates have been examined by researchers in the US. They have also shown that the observed transient leakage currents result in a shot noise that is twenty times larger than predicted using only conventional static leakage current measurements. PAGE 111 Researchers in the UK have presented an RF energy harvesting technique for powering small devices. Their work focuses on harvesting power from ambient radio waves, which is particularly useful in sensor networks where energy requirements are low and appeals as a solution to make them self-sustaining. The observed shot noise was 20 times greater than static leakage current measurements predicted PAGE 107 The first experimental demonstration of a continuous wave two-pump fibre optic parametric amplifier has been reported by researchers in France. Their device is of primary interest in the amplification of chirped pulses, and should allow for an all-fibre parametric amplifier operating at 1 µm with a flat gain band. The RF energy harvesting technique is aimed at allowing self-sustaining sensor networks PAGE 98 Researchers in Korea have devised a simple and cost-effective epitaxial graphene fabrication technique that results in good electric performance. This approach is expected to pave the way for a more cost-effective formation of highly reliable, low sheet resistance graphene, particularly for SiC-based electronic devices, power devices, SiC-graphene hetero-junctions and graphene-on-insulator semiconductors. The amplifier uses a dispersion stabilised microstructured optical fibre with high nonlinearity and low loss PAGE 93 Researchers in France have realised and measured an innovative microwave transmission line which can be integrated into complex multilayer systems. A multilayer structure like transmission line is essential to any telecommunication and radar power devices, such as power modules, solid state power transmitters, filters or any distribution system in that frequency range. A simpler and cheaper way to make graphene with low sheet resistance Thermal simulations suggest the structures will handle 50W average RF powers making them suitable for x-band power combination

Comparison of the structural and optical properties of ZnO thin films deposited by three different methods for optoelectronic applications

ZnO thin films were deposited using three processes e.g.; thermal oxidation of metallic zinc (Zn), sol–gel and RF sputtering. The structural, optical and electrical properties of ZnO films were investigated and compared systematically using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), Raman spectroscopy, photoluminescence (PL) and UV measurements. Stoichiometric and surface morphological difference was observed in the films deposited by three different techniques. Thermally oxidized ZnO films and sol–gel derived ZnO film had naturally grown textured surface, while the surface of the sputtered ZnO film was relatively smooth. The electrical transport properties of the Pd/ZnO Schottky contact were studied by using microprobe arrangement. The values of ideality factor and barrier height were found to be significantly good for Schottky contact of thermally oxidized ZnO thin film. The study demonstrates that Pd/ZnO Schottky type contact fabricated by a simple and inexpensive growth technique can be used as a substitute of conventional Schottky diodes for electronic and optoelectronic applications.

Optical Characterization of ZnO Thin Films Grown by Thermal Oxidation of Metallic Zinc

-type Si (100) substrates by thermal oxidation of pre-deposited Zn films bythermal evaporation deposition in vacuum. The metallic Zn films were thermally oxidized at different tempera-tures ranging from 300 C to 500 C. The structural as well as optical characterizations of the thin films werecarried out by using XRD, AFM, Raman spectroscopy, UV measurements and photoluminescence (PL) respec-tively. The Raman spectra showed that only

High c-axis preferred orientation ZnO thin films prepared by oxidation of metallic zinc

Thin films of zinc oxide were grown on glass substrates by thermal oxidation. The metallic zinc films were thermally oxidized at different temperatures ranging from 300 to 600 °C to yield ZnO thin films. The structural property of the thin films was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The X-ray diffraction measurements showed that the films oxidized at 300 °C were not oxidized entirely, and the films deposited at 600 °C had better crystalline quality than the rest. When the oxidation temperature increased above 400 °C, the films exhibited preferred orientation along (002) and high transmittance ranging from 85% to 98% in vis–near-infrared band. Meanwhile, the films showed a UV emission at about 377 nm and green emission. With the increasing of oxidation temperature, the intensity of green emission peak was enhanced, and then decreased, disappearing at 600 °C, and the case of UV emission increased. Furthermore, a strong green emission was observed in the film sintered in pure oxygen atmosphere.

Zinc Oxide Nanorods Prepared in Mixed Solvents

In this paper, we demonstrate a novel and direct synthesis of hexagonal-shaped zinc oxide (ZnO) nanorods at very low temperature of ~ 80oC simply by using metallic zinc foil and de-ionized (DI) water with few drops of ethanol. The formation of ZnO structures by the reaction of metals with DI water is suggested to occur due to the oxidation of metallic zinc in presence of water. The synthesized ZnO products were characterized in terms of their structural and optical properties. By the morphological investigations using FESEM, it was observed that the grown products are hexagonal-shaped ZnO nanorods with the diameters in the range of 50-60 nm and length with ~ 1 micrometer. The EDS and XRD pattern confirmed the composition and crystallinity of the grown nanorods and revealed that the grown products are pure ZnO with the wurtzite hexagonal phase.