ZnO Nanoarrays Research Articles

Preparation and photoelectric properties of Bi doped ZnO nanoarrays

ZnO has a large band gap, which affects its photoelectric catalytic performance to a certain extent. In this paper, Bi-doped ZnO nanoarray was successfully prepared by electrochemical deposition to improve the photoelectrochemical performance of ZnO as a photoanode. XRD results show the prepared Bi-doped ZnO is a typical hexagonal wurtzite crystal, and the SEM results also proved this point. The prepared Bi-doped ZnO presents a neat nano-array, and the doping of Bi also reduces the diameter of the nanorods from the original 500–350 nm. The results of XPS show that Bi is successfully doped into the ZnO nanoarrays, and it exists in the form of Bi2O3. Subsequently, the prepared Bi-doped ZnO was analyzed by fluorescence spectroscopy and photoelectrochemical properties, and it was found that when the doping concentration was 5%, the fluorescence intensity was the lowest, and at this time the carrier recombination rate corresponding was the lowest, the photoelectric catalytic effect was the best.

Preparation of ZnO/Bi2O3 Composites as Heterogeneous Thin Film Materials with High Photoelectric Performance on FTO Base

In recent years, ZnO nanomaterials have achieved great performance in solar energy applications. How to synthesize a ZnO nanocomposite structure with high photoelectric conversion efficiency has become an urgent problem to solved. In this paper, a narrow band gap bismuth trioxide (Bi2O3) coated on a ZnO nanoarray by magnetron sputtering was used to prepare a composite heterojunction ZnO/Bi2O3. Studies have found that ZnO/Bi2O3 exhibits excellent photoelectric conversion performance. By preparing a composite heterostructure of ZnO/Bi2O3, it can effectively compensate for the insufficient absorption of ZnO in the visible light range and inhibit the recombination of carriers within the material. The influence of Bi2O3 thickness on the microstructure and electronic structure of the ZnO/Bi2O3 composite structure was explored and analyzed. The energy gap width of the composite heterostructure decreases with the increase in the Bi2O3 thickness on the surface of the ZnO nanorod array. At the same time, the conductive glass composite film structure is simple to prepare and is very environmentally friendly. The ZnO/Bi2O3 composite heterogeneous material prepared this time is suitable for solar cells, photodetectors, photocatalysis and other fields.

Low-Cost Electrodeposition of Size-Tunable Single-Crystal ZnO Nanorods

In this paper we report a low cost, simple, electrochemical method for large-area growth of single crystal ZnO nanorods. The method utilizes a metallic zinc foil as the source of the necessary zinc ions for ZnO growth on indium-doped tin oxide (ITO) glass slides. The method is thoroughly discussed and investigated varying all the parameters involved. The resulting ZnO nanorods are highly oriented along c-axis and densely packed, while their length and diameter can be tuned by varying the growth parameters. Two different types of seed layers on the ITO glass slides are tested. A seed layer made by spin coating of ZnO nanoparticles results in a twofold increase of the ZnO nanorod surface density as compared with a ZnO thin film seed layer by physical vapor deposition. Additionally, the effect of oxygen supply during electrodeposition was investigated as a crucial regulatory parameter not only for the geometrical and topological characteristics of the ZnO nano-arrays but for their physical properties as well.

Skin‐like Elastomer Embedded Zinc Oxide Nanoarrays for Biomechanical Energy Harvesting

AbstractEnergy harvesting (EH) technologies have been rapidly developed to replace the batteries of biomechanical electronics, but efforts are still needed to close the technology gaps in achieving flexible and biocompatible energy harvesters. Current flexible energy harvesters based on ZnO nanoarrays require complex fabrication processes, and they are non‐stretchable as they are usually fabricated on hard substrates. In this work, a facile approach is reported for fabricating a substrate‐free energy harvester with ZnO nanoarrays directly and fully embedded in a skin‐like polydimethylsiloxane (PDMS) elastomeric matrix that shares a similar mechanical property with that of human skin. The flexible device, with an elastic modulus of 3.3 MPa, can be stretched to 250% of its original length, generates an open‐circuit voltage up to 9.2 Vpp and power LEDs from finger‐hand motions. Further, the device collects energy from hand‐finger motions and heartbeats through ex and in vivo tests. A ≈0.3 Vpp open circuit voltage is generated from the device installed on a leadless pacemaker in a porcine model. This work suggests a generic design strategy that overcomes the mechanical mismatch between the energy materials and soft tissues for a wide range of biomechanical EH applications from wearables to implantable ones.

Ce, Eu incorporation through doping of ALD-ZnO thin films for enhancing their photoluminescent properties

Nanostructured ZnO nanoarrays deposited on silicon oriented substrates is a very promising area in the study of the control of physicochemical properties, in which photoluminescence plays a crucial role. This optical property inherent to ZnO, can be favorably modified through the inclusion of doping elements, with the purpose of appropriately modifying their optical absorption and luminescence. Following this objective, in the present work we present the development of Zn(1−x–y)Ce(x)Eu(y)O nanostructured thin films. The samples were produced in two steps process by atomic layer deposition technique followed by a solvothermal synthesis. The purpose of Cerium and Europium incorporation into the ZnO compound is to enhance the photoluminescence in ZnO thin films. In a first stage textured thin films were obtained from diethylzinc at a temperature of 190 °C and a pressure of 3.29 × 10−4 atm, on silicon substrates (111). Subsequently, the perpendicular growth of nanostructures was induced under a solvothermal process, where Zn(NO3)2 was used as Zn precursor and hexamethylene-tetramine operating as a dual-ligand to promote the linking of Zn2+ ions. The growth of cerium-europium ZnO nanostructures was promoted with Ce(C2H3O2)3·H2O and Eu(NO3)3·5H2O. The obtained Zn(1–x–y)Ce(x)Eu(y)O nanostructured thin films, were examined through SEM-microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and photoluminescence studies. The attained results show that it is feasible to produce Ce–Eu-doped ZnO nanostructures with tailored photoluminescence and crystal size. Interestingly the Ce–Eu doping induces a strong shift in comparison to the typical UV emission of ZnO; an effect that can be related with the increase of lattice defects in ZnO.

ZnO nanoarrays via a thermal decomposition–deposition method for sensitive and selective NO2 detection

ZnO nanoarrays deposited by a thermal decomposition–deposition (TDD) strategy demonstrate a high response for NO2 detection.

Vertical nanoarrays with lithiophilic sites suppress the growth of lithium dendrites for ultrastable lithium metal batteries

Lithium (Li) metal has emerged as an ideal anode for advanced energy storage devices due to its high theoretical capacity. However, Li dendrite formation and large volume change during continuous charge/discharge processes lead to low Coulombic efficiency and severe safety issues, hindering the commercial application of Li metal batteries. Herein, a 3D conductive host comprising lithiophilic ZnO nanoneedle arrays grown on a flexible carbon cloth is designed to pre-store Li via thermal infusion strategy and Li@ZnO@carbon cloth (denoted as Li@ZnO@CC) electrode is formed. The 3D carbon cloth offers the advantages of sufficient free space for Li storage and massive Li nucleation sites. Besides, the presence of lithiophilic ZnO nanoarrays induces homogeneous Li deposition, thus significantly suppresses Li dendrite nucleation and growth. Compared with bare Li electrode (80 cycles), Li@ZnO@CC can stably cycle over 480 cycles under a Li plating/stripping capacity of 1 mAh cm−2 at the current density of 3 mA cm−2. When coupled with LiFePO4 cathode, the full cells display high specific capacity (163 mAh g−1 at 0.2 C), excellent rate performance and outstanding cycle stability, highlighting the possible application of Li@ZnO@CC anode for next-generation, high-energy density and safe batteries.

Ultrafast physical bacterial inactivation and photocatalytic self-cleaning of ZnO nanoarrays for rapid and sustainable bactericidal applications

Various nanostructured surfaces have been developed recently to physically inactivate bacteria, for reducing the rapidly spreading threat of pathogenic bacteria. However, it generally takes several hours for these surfaces to inactivate most of the bacteria, which greatly limits their application in the fields favoring rapid bactericidal performance. Besides, the accumulated bacteria debris left on these surfaces is rarely discussed in the previous reports. Herein we report the nanotip-engineered ZnO nanoarrays (NAs) with ultrafast physical bactericidal rate and the ability to photocatalytically remove the bacteria debris. Neither chemical (Zn2+ or reactive oxygen species) nor photocatalytic effect leads to the ultrafast bactericidal rate, where 97.5% of E. coli and 94.9% of S. aureus are inactivated within only 1 min. The simulation analysis further supported our proposed mechanism attributing the ultrafast bactericidal activity to the great stress enabled by the uneven topography. Moreover, the re-exposure of the ZnO NAs nanotips can be achieved in only 10 min under a mild UV light source. This study not only presents an ultrafast physical bactericidal activity, but also demonstrates the potential of the recyclable and photocatalytic self-cleaning functions of theses surfaces for applications that desire rapid and sustainable bactericidal performance.

Wearable Battery-Free Perspiration Analyzing Sites Based on Sweat Flowing on ZnO Nanoarrays

HighlightsWearable battery-free perspiration analyzing sites based on sweat flowing on ZnO nanoarrays was fabricated.Coupling of hydrovoltaic effect and enzymatic reaction were analyzed.The wearable wireless physiological status monitoring system has potential application in constructing sports big data.

Effect of Al Doping on Hydrothermal Growth and Physical Properties of Doped ZnO Nanoarrays for Optoelectronic Applications

Abstract Renewable energy production via solar energy is a promising solution to advent the globally mounting energy needs. Therefore, our work has been planned to develop, high efficient optoelectronic devices, which are cost effective and easily fabricated. Successfully, we developed Al doped ZnO nanorods (NRs) by two step process. Initially by using sol-gel technique we grow the seed layers and further we succeed ZnO nanorods by a simple hydrothermal process without using any toxic solvents. The obtained nanorods show remarkable electrical and optical properties characterized by I-V characteristics, UV- vis, Photoluminescence (PL) spectroscopy techniques. In addition, we have also investigated the surface morphological properties from FESEM which indicates that NRs are hexagonal in shape and the diameter of the rod varies from 232 nm to 297 nm as the Al concentration changes from 1% to 10% in ZnO. Band gap of Al doped ZnO NR decreases on increasing the concentration of doping from 3.23 to 2.73 eV. The PL spectrum shows emission peaks in the UV and visible region. From this we conclude that, these materials are good candidate for the optoelectronic applications. Thus, our approach will probably fetch and derive a noble route for the fabrication of new materials.

Electric-field assisted growth and mechanical bactericidal performance of ZnO nanoarrays with gradient morphologies

Abstract In response to the widespread bacterial threat, mechanical bactericidal nanostructures with various morphologies have been reported for years. However, the relationship between morphology and bactericidal properties is still yet to be elucidated due to the lack of a fair comparison under similar density of the nanostructures. For this purpose, an electrical-field assisted hydrothermal growth method were utilized to prepare the ZnO nanoarrays with similar array density (1.9×109 rod·cm2-2.4 ×109 rod·cm2) but gradient morphologies from hexagonal prism, hexagonal prismoid to hexagonal pyramid on stainless steel sheets. Moreover, in dark condition, a bactericidal activity was observed on the ZnO nanoarray surfaces within 30 min contact for both E. coli and S. aureus cells. The bactericidal rate was rapidly enhanced as the average tip width of the nanorods decreasing from 137 to 38 nm. These results suggest that the hexagonal pyramid ZnO nanoarrays have a rapid, efficient and broad-spectrum bactericidal activity, which could contribute to the next-generation aquatic pathogens control strategies.

Nanostructured ultrathin catalyst layer with ordered platinum nanotube arrays for polymer electrolyte membrane fuel cells

Abstract Fabrication of novel electrode architectures with nanostructured ultrathin catalyst layers is an effective strategy to improve catalyst utilization and enhance mass transport for polymer electrolyte membrane fuel cells (PEMFCs). Herein, we report the design and construction of a nanostructured ultrathin catalyst layer with ordered Pt nanotube arrays, which were obtained by a hard-template strategy based on ZnO, via hydrothermal synthesis and magnetron sputtering for PEMFC application. Because of the crystallographically preferential growth of Pt (111) facets, which was attributed to the structural effects of ZnO nanoarrays on the Pt nanotubes, the catalyst layers exhibit obviously higher electrochemical activity with remarkable enhancement of specific activity and mass transport compared with the state-of-the-art randomly distributed Pt/C catalyst layer. The PEMFC fabricated with the as-prepared catalyst layer composed of optimized Pt nanotubes with an average diameter of 90(±10) nm shows excellent performance with a peak power density of 6.0 W/mgPt at 1 A/cm2, which is 11.6% greater than that of the conventional Pt/C electrode.

Integration of ZnO nanoarrays on partially imidized polyimide substrates

ZnO seed and nanoarrays were effectively integrated on polyimide (PI) substrates by depositing the ZnO seed during thermal imination of PI. The surface roughness of PI films with different imidization degrees was different; the maximum root-mean square-value was achieved when the imidization degree was 80%. The prepared wurtzite-type ZnO seed and nanorods showed preferential c-axis orientation and offered good adhesion to flexible PI substrates. The light transmittance of the functionalized film, which mainly depends on PI, was sufficiently large in the visible region. Therefore, the proposed methodology is a novel route for synthesizing a variety of nanostructures on PI films at a low cost.

Green Approach for Metal Oxide Deposition at an Air-Liquid-Solid Triphase Interface with Enhanced Photocatalytic Activity.

Bioinspired superhydrophobic substrates have been used in many scientific and technological areas. These substrates can trap atmosphere-linked air pockets at the solid–liquid interface, offering an opportunity to address the oxygen-deficit problem in many reaction systems. Herein, we addressed the oxygen-deficit problem in metal oxide electrochemical deposition by using a triphase electrode possessing an air−liquid−solid joint interface. Oxygen in the interface is directly available from the air phase for sufficient OH– production via oxygen cathodic reaction, thereby offering us a green approach to fabricate two-dimensional mesoporous ZnO nanoarrays over a wide range of current densities. Further, because metal oxides are deposited at the triphase interface, sufficient O2, a natural electron scavenger required in photocatalytic reaction to suppress the recombination of photogenerated electron–hole pairs, can be directly supplied, and we demonstrated their enhanced photocatalytic reaction kinetics in water remediation. The present work highlights a powerful interface-engineering strategy for fabricating metal oxides with unprecedented photocatalytic ability.

Three-Dimensional Structures of Nanoporous NiO/ZnO Nanoarray Films for Enhanced Electrochromic Performance.

An electrochromic device with the as-obtained nanoporous NiO /ZnO nanoarray as a working electrode was constructed and assembled. The nanoporous NiO/ZnO nanoarray film with a three-dimensional structure was prepared on indium tin oxide (ITO) glass substrate through a two-step route that combined chemical bath deposition method with a hydrothermal method. The nanoporous NiO/ZnO nanoarray electrode reveals a noticeable improvement in electrochromism compared with that of nanoporous NiO alone, including higher optical modulation (81 %), higher coloration efficiency (78.5 cm2 C-1 ), faster response times (2.6 and 9.7 s for coloring and bleaching, respectively), and favorable durability performance. Such enhancements are mainly attributed to the three-dimensional structures of nanoporous NiO coated on ZnO nanoarray, namely, 1) the uniform hexagonal ZnO nanoarray loads more nanoporous NiO, 2) nanoporous NiO cross-linked with ZnO nanorods provides a loose interspace morphology, 3) stronger adhesion between ZnO nanorods and ITO covered with ZnO seed, 4) core-shell and cross-linked structures promote electrolyte infiltration, and 5) appropriate band gaps improve charge transfer.

Core–shell assembly of Co3O4@NiO-ZnO nanoarrays as battery-type electrodes for high-performance supercapatteries

Core–shell Co3O4@NiO-ZnO nanoarrays are fabricated by annealing metal–organic framework assisted precursors and investigated as battery-type electrode for supercapattery.

Durable superhydrophobic and underwater superoleophobic cotton fabrics growing zinc oxide nanoarrays for application in separation of heavy/light oil and water mixtures as need

Based on controlling ZnO nanoarrays morphology and employing fluorine-free modification agent, superhydrophobicity in air and superoleophobicity under water were successfully achieved on the prepared cotton fabric surfaces via a two-step hydrothermal reaction. To increase adhesion between ZnO crystal layer and substrate surface, two kinds of silane coupling agents (hydrophobic TTOP-12 and hydrophilic KH550) were added selectively in the pretreatment process. The as-prepared fabric exhibited great tolerance and durableness towards external harsh environments, such as mechanical abrasion, UV radiation, immersion of acid or alkali, and high temperature. In comparison, superhydrophobic fabrics showed superior separation effect for heavy oil and water mixture, while underwater superoleophobic fabric can also show efficient separation of water and light oil with high separation efficiency and flux. In a word, heavy/light oil and water mixtures can be separated efficiently as need by choosing cotton fabrics with various wettabilities.

Synthesis of High‐Quality Wurtzite Cu2ZnSn(S1−x,Sex)4 Nanocrystals With Non‐Toxic Selenium Precursor and the Photoelectrochemical Performance of ZnO NAs/CZTSSe Heterojunction

Fabrication of high performing CZTSSe absorber material from environmental benign nanocrystals ink is very important for large‐scale manufacturing production. Herein, the high‐quality metastable wurtzite Cu2ZnSnS4 (W‐CZTS) and wurtzite Cu2ZnSn(S1−x,Sex)4 (W‐CZTSSe) nanocrystals with small sizes have been synthesized successfully using dodecanethiol (DDT) and Se‐octadecylamine (Se‐ODA) as the sulfur and selenium sources, respectively. Compared to the thin film obtained from W‐CZTS nanocrystals ink, the thickness of small grain layer in the thin film obtained from W‐CZTSSe nanocrystals is reduced significantly. Further the ZnO nanoarrays (NAs)/CZTSSe heterojunction thin‐film grows on fluorine‐doped tin oxide (FTO) substrate and it exhibits superior photoelectrochemical (PEC) performance under light illumination. The ZnO NAs/CZTSSe heterojunction thin film shows the photocurrent density of 3.44 mA cm−2, which is nearly 2.7‐fold higher than the photocurrent density of ZnO NAs. The PEC efficiencies of ZnO NAs and ZnO NAs/CZTSSe are 0.4% and 1.89%, respectively. Our results demonstrate that the as‐synthesized W‐CZTSSe nanocrystals by using Se‐ODA are a promising precursor to fabricate high performing thin film, the Se‐ODA can be applied to prepare the precursors of chalcogenide thin film (including CISe, CIGSe, and CZTSSe).

A Wearable All-Solid Photovoltaic Textile

Flexible solar cell has received a wide range of interests due to the development of wearable electronics. Herein, we have come up with the idea of wire-shaped solar cell, which has provided a new solution to get rid of expensive TCO substrates. We present a solution to power the portable electronics in a wearable manner by fabricating an all-solid photovoltaic textile. The photoanode is fabricated by assembling dye-sensitized ZnO nano-arrays on low-cost Mn-plated wire. And then, it was woven with Cu wires and colorful polymer fibers, for specially designed electrical connection and a colorful outlook. Colorful and flexible photovoltaic textile modules with arbitrary size and various knitting patterns were demonstrated as a wearable power source for portable and flexible electronics. As a result, a flexible photovoltaic textile with a Voc of 4.6 V was realized, which could directly power up a commercial calculator. With such features as low-cost, thinness, light-weight, being flexible and wearable, as well as colorful appearance, this work represents a significant step towards the development of large scale solar energy harvesting for wearable electronics and self-powered home technology.

Effect of Sn doping on structural, mechanical, optical and electrical properties of ZnO nanoarrays prepared by sol-gel and hydrothermal process

Undoped and Sn doped Zinc oxide nanorods were prepared by two step process: initially growth of seed layers by sol-gel spin coating technique and then zinc oxide nanorods by hydrothermal process using the precursors zinc nitrate hexahydrate, hexamine and tin chloride. The effects on the electrical, optical, mechanical and structural properties for various Sn concentrations were studied. The crystalline phase determination from X-ray diffraction (XRD) confirms that Sn doped ZnO nanorods have hexagonal wurtzite structure. The variations of stress and strain with different doping concentration of Sn in ZnO nanorods were studied. The doping effect on electrical properties and optical bandgap is estimated by current voltage characteristics and absorbance spectra respectively. The surface morphology was studied with field emission scanning electron microscope (FESEM), which shows that the formation of hexagonal nanorods arrays with increasing Sn concentration. The calculated value of Young's modulus of elasticity (Y) for all the samples remains same. These results can be used in optoelectronic devices.