Nanostructured ZnO Films Research Articles

Tailoring the optical and physical properties of La doped ZnO nanostructured thin films

The modification and tailoring characteristics of nanostructured materials are of great interest due to controllable and unusual inherent properties in such materials. A simple spray pyrolysis technique was used to prepare pure and La-doped ZnO films. The influence of La concentration (0, 0.33, 0.45, 0.66, 0.92 and 1.04 at. %) on the structural, optical, and magnetic properties of ZnO was investigated. The exact nominal compositions of the prepared films were determined from the field emission scanning electron microscope occupied with EDX. X-ray diffraction confirmed that the samples possessed single-phase hexagonal wurtzite structure. The main crystal size was decreased from 315.50 Å to 229.04 Å depending on La dopant concentration. This decrease is due to the small ionic radius of Zn ions in compared to La ions. The band gap values were found to be depend strongly on La3+ ion content. Introducing La into ZnO induces a clear magnetic moment without any distortion in the geometrical symmetry, it also reveals the ferromagnetic coupling. The saturation magnetic moment of 1.04 at.% La-doped ZnO shows the highest value of 0.014 emu, which is ∼23 times higher than pure ZnO sample. The obtained results were discussed and compared with other literature data and showed an acceptable agreement.

Synthesis and Characterization of c-Axis Oriented Zinc Oxide Thin Film and Its Use for the Subsequent Hydrothermal Growth of Zinc Oxide Nanorods

ABSTRACTOriented ZnO seed layers were deposited by three different techniques, namely, simple drop casting (DC), sol-gel derived dip coating (DPC) and spin coating of ball-milled ZnO powder solution(BMD) for the subsequent growth of vertically aligned ZnO nanorods along the substrate normal. X-ray diffraction (XRD) analyses revealed that ZnO(DC) seed layer exhibit the highest preferential c-axis texturing among the ZnO seed layers synthesized by different techniques. The Scanning Electron Microscopy (SEM) analysis evident that the morphology of ZnO seed layer surface is compact and coherently carpets the underlying substrate. ZnO nanorods(NRs) were then grown by hydrothermal method atop the ZnO seeded and non-seeded substrates grown by different techniques to elucidate the best ZnO seed layer promoting well-aligned ZnO Nanorods. The presence of c-axis oriented ZnO(DC) seeding layers was found to significantly affect the surface morphology and crystallographic orientation of the resultant ZnO NRs films. The optical band gap of ZnO(DC) seed and ZnO NRs were estimated to be 3.30 eV and in the range of 3.18 – 3.25 eV respectively by using UV-VIS-NIR diffuse reflection spectroscopy. The room temperature photoluminescence analyses revealed that nanostructured ZnO films exhibit a sharp near-band-edge luminescence peak at ∼380 nm consistent with the estimated optical band gap and the ZnO nanorod arrays are notably free from defect-related green-yellow emission peaks.

Study the Structural Properties of ZnO Prepared by Pulsed Laser Deposition Technique

In this research, ZnO nanostructure films were prepared using pulsed laser deposition method on glass substrates ina room temperature. The ZnO nanostructures were characterized by X-ray diffraction and atomic force microscopy (XRD, AFM). Thegrownthin films have a polycrystalline wurtzite structure, it can be seen that the highest texture coefficient was inplane (101), with grain sizes between (41nm-65nm), morphology of the film wasstudied and showed that the average root mean squareincreases with the thickness of the films, with RMS between (197nm-206nm).

Tailoring the properties of zinc oxide films by incorporating gold nanoparticles using RF magnetron sputtering

Nanoscale noble metal-incorporated ZnO nanostructures can have potential applications in developing chemical and biological sensors, optical filters, ultrafast switching devices, etc. The structural, morphological and optical properties of the as-deposited pure and Au-incorporated RF-sputtered ZnO films were investigated. XRD analysis suggests that the presence of Au nanoparticles strongly promotes the growth of well-crystalline grains of ZnO along $$\left\langle {00{\text{1}}} \right\rangle$$ direction. Surface morphology examined using AFM and FESEM micrographs and compositional analysis using EDX spectra reveal that Au acts as a nucleating center for the growth of high-crystalline grains, leading to the formation of specific structures. The observed reduction in transmittance with Au incorporation concentration can be attributed to LSPR of gold nanoparticles, scattering, increased surface roughness and increased thicknesses of the films. Systematic increase in the intensity of the plasmonic peak along with a shift in its position towards longer wavelength region is observed with increase in Au incorporation concentration. The PL spectra of the films show a NBE emission due to excitonic transition in ZnO and blue emission originating from deep-level defects in ZnO. The influence of Au nanoparticles on the crystallization of ZnO grains, evolution of surface morphology of ZnO nanostructured films and modification in the UV emission efficiency of ZnO films due to SPR of Au nanoparticles are studied in detail.

PH-controlled surface engineering of nanostructured ZnO films generated via a sustainable low-temperature H2O oxidation process

Developing a consistent and sustainable protocol for fabricating predetermined ZnO nanostructures is of significant interest in materials science and industry, owing to the emergence of ZnO-based devices and applications. Herein, the design of novel nanostructured ZnO films via a green, sustainable and low-temperature H2O oxidation technique is presented. Surface engineering was achieved by controlling the pH value of H2O during oxidation of Zn thin films. Diverse ZnO nanostructures of high structural and optical qualities including nanoparticles, microparticles composed of smaller rods, columnar nanorods and nanotubes having different growth orientations emerged. The morphology, chemical composition, structure, surface chemistry and optical properties of the nanomaterials were comprehensively characterized as a function of pH value. The experimental results and proposed growth mechanism for each nanostructure were presented and thoroughly discussed to have a deeper understanding on the physical insights governing the pH-controlled development of the nanostructures. This in-depth examination could pave the way to pioneering properties and functionalities that could sustainably fulfill the requirements of next generation optoelectronic devices.

Structural, optical and dielectric properties of gadolinium incorporated laser ablated ZnO thin films

Gadolinium doped ZnO nanostructured thin films were prepared on quartz substrates by pulsed laser ablation. The effects of thermal annealing at temperatures 400 to 600 °C on the structural, optical and dielectric properties were investigated. The as deposited film is amorphous in nature and all the annealed films show polycrystalline nature with hexagonal wurtzite crystal structure. The AFM images of the doped films show a porous structure for the films. An enhanced transmittance and surface smoothness with increase in annealing temperature were observed. The band gap energy was increasing with decrease in particle size. The porosity and refractive indices of the films were calculated from the transmittance and reflectance spectra. The complex dielectric constant and the loss factor of the ZnO thin films were calculated. From the Photoluminescence spectra all the films show PL emission in the UV and visible region. The Oi type defects are responsible for the enhanced green emission.

Hierarchical ZnO nanoflowers and urchin-like shapes synthesized via sol-gel electrophoretic deposition with enhanced photocatalytic performance

In this study, we report a simple sol-gel electrophoretic deposition method for growing two different morphologies of ZnO using triethylamine (TeA) and diethanolamine (DEA) as stabilizers in order to systematically investigate the importance of morphological and structural properties on photocatalytic applications of ZnO. FESEM imaging shows that the morphology of the ZnO nanostructured films can be tuned from ZnO urchin-like shapes assembled by nanoparticles to nanoplate arrays-built flower-like hierarchical nanostructures when TeA and DEA are used as additives, respectively, by selecting the appropriate reactants and optimizing the sol concentration, molar ratio of additive to precursor, time, and voltage of deposition. The specific mechanisms for the formation of these two morphologies are also proposed based on the observation of time-dependent experiments. The large specific surface area of flower shapes compared to urchins result in enhanced absorption of methylene blue and improved photocatalytic activity.

Surface enhanced lithography with adhesion agent to achieve large-scale ZnO nanostructure on stainless steel substrate

We present a novel point of view to fabricate an enhanced stability controllable growing, large-scale, direct, fast and template assisted nanostructure ZnO with twin –OH group terminated of compound containing –OH group by electrochemical deposition (ECD). In this paper, the collected potassium acid phthalate with twin –OH group was printed to form a matrix as template to synthesize a ZnO nanostructure. Structural analyses showed that the ZnO nanostructure is wurtzite in structure, without any secondary phases. Various features of Raman mapping and X-ray photoelectron spectroscopy of the as-prepared ZnO were found to mark variety of the characteristic of the as-prepared ZnO before and after tape test. A direct link between growing ZnO and potassium acid phthalate with twin –OH group was established, suggesting that this special twin –OH group between nanostructure ZnO and substrate (stainless steel) plays a vital role in forming a firm nanostructure ZnO film on the surface of the substrate. Furthermore, we raised a mechanism to explicate the functional process of twin –OH group on ZnO film. We believe that this facile method to fabricate a controllable nanostructure ZnO here is equally applicable to other semiconductors which are critical in optoelectronics, lasing and luminescence applications.

Erbium-doped nanoparticles/films for enhancing percentage photodegradation of direct red-31 dye

Nowadays, the demand for synthetic dyes has grown manifold as there are being widely used in leather, textile, food industries. This paper reports Erbium doped ZnO nanostructured films were deposited on to the glass substrate by a sol–gel spin coating technique. Atomic weight percentage of Erbium was varied from 2.0, 2.5, 3.0, and 3.5 at.wt% namely EZ-1, EZ-2, EZ-3 and EZ-4 and the film characterization were carried out by means of X-Ray diffraction, FESEM, UV–Vis spectrophotometer, Raman spectroscopy, LCR and photoluminescence measurements. XRD result revealed the existence of Er2O3 and ZnO phases for varied Er concentration. FESEM reveals rod-shaped morphology of the film of the order of the size of 40–75 nm. Absorbance and optical band gap was obtained from UV–Vis spectrophotometer. This revealed optical band gap widening with a molar ratio in the range of 3.26–3.32 eV. Raman spectroscopy indicates the tensile stress in Er-doped ZnO films. Photoluminescence intensity near 594 nm indicates more oxygen vacancies which led to high photocatalytic performance. The prepared films were used for photodegradation of DR-31 dye. From the photocatalytic experiment, the degradation percentage was increased with increase in Er concentration up to a molar ratio of 3.0 at.wt%. Thus the optimum molar ratio of the prepared films (3.0 at.wt%) exhibits almost complete degradation of DR-31 dye only in 48 min under UV illumination. The kinetic study reveals the rate constant of nanospheres like particles is 0.07428 min−1. The Er-doped films with different molar ratio result in almost same photocatalytic performance after regular interval of the time. The comparative study of nanoparticles with the film will make for photodegradation of DR-31 dye under same experimental conditions. Despite kinetic study of prepared films were better as compared to bulk form (powder) but the percentage degradation of nanoparticles was found to be better than films.

Structural, electronic, magnetic, optical and optoelectronic properties of the sprayed cobalt doped ZnO nanostructured thin films

In this paper, we theoretically and experimentally investigated the structural, electronic, optical and magnetic properties of Cobalt doped ZnO. We used the the SPRAY Pyrolysis technique on preheated substrate glass. Samples were characterized using x-ray Diffraction. Optical parameters such as the optical band gap energy (Eg), the refractive index (n), the dielectric constants (ϵr, ϵi) and the optical conductivity (σ) as a function of photon energy have been investigated. As main result, 2% Co doping leads to improve the optical and optoelectronic properties of ZnO with a higher refractive index, optical conductivity and absorption near infrared region. Furthermore, we investigated the doping concentration effect on the magnetic and structural properties by first principal calculations and found a promising phase change temperature which is higher than room temperature.

Influence of ZnCl2 concentration on the structural and optical properties of electrochemically deposited nanostructured ZnO

These works present the electrochemical deposition of ZnO nanostructured thin films on glass substrates covered by SnO2 thin films. Nanostructured ZnO films are obtained by an electrochemical process using a three-electrode system with a saturated calomel electrode as reference electrode, in aqueous solution containing ZnCl2 and KCl. The influence of ZnCl2 concentration on the structural properties of the obtained ZnO layers is investigated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and optical profilometry. The SEM micrographs show that the ZnO films consist of nanograins at lower ZnCl2 concentrations that transform in a shape of walls at the highest one. The XRD spectra demonstrate the polycrystalline nature of the films at all studied concentrations with the presence of (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0) and (1 0 3) characteristic reflexes of the ZnO. The influence of the ZnCl2 concentration on the transmittance and reflectance spectra and haze ratio of ZnO thin films is presented and discussed. The ZnO nanostructured layers exhibit high values of the diffuse transmission and reflection in the 400–900 nm spectral range; they can be applied as rear contacts of thin films solar cells thus increasing the light trapping.

Control of Charge Transfer in C60–ZnO Composite Under the Influence of UV Laser Radiation by the Methods of Raman Spectroscopy and Photoluminescence

Raman and photoluminescence spectra of nanostructured ZnO films with adsorbed C60 molecules were studied. The possibility of intensive C60–ZnO electronic coupling forming in this composite was investigated. It is shown that such an electron coupling can be significantly enhanced by irradiating the composite with high intensity UV laser radiation (λ = 325 nm).

Surface modification of ZnO nanostructured film prepared by hot water oxidation

ZnO nanostructured films with tunable morphology were fabricated using hot water oxidation of etched Zn foils at 90 °C under varying solution conditions. At high pH, coarse ZnO nanostructured film, consisting of short nanorods, was produced. When the pH was lowered to about 3.8, no ZnO nanostructures were produced. On the other hand, a 1D-2D composite ZnO nanostructured film, consisting of nanorods and nanosheets, was formed by adding 0.05 to 0.20 M ZnCl2 during hot water oxidation. Increasing the ZnCl2 concentration further produced simonkolleite platelets instead of ZnO. The as-synthesized ZnO nanostructured films showed excellent wettability with static water contact angle ranging from 0 to 22.37°. Surface modification with stearic acid and 1-hexadecene under UV illumination effectively altered the wetting properties of the ZnO nanostructured films, resulting to superhydrophobic surfaces with static water contact angles of 149.90–156.62° and contact angle hysteresis as low as 1.63°. The 1-hexadecene-treated pencil-like ZnO nanorods achieved the highest water contact angle and retained its superhydrophobicity even after mechanical abrasion.

Multiscale design of ZnO nanostructured photocatalysts.

A systematic investigation of the photocatalytic activity (PCA) of nanostructured ZnO films showed how this is directly affected by the films' morphology at different scales, from the macroscale morphology of films (e.g. thickness and surface area), to the microscale feature arrangement (e.g. aligned vs. randomly oriented structures or interpenetrated ones), to the nanoscale structure (e.g. crystal size and orientation). The interest in immobilizing photocatalysts in water treatment stems from concerns about the potential toxicity of their slurry form, which requires expensive downstream removal. Immobilisation, though, leads to a reduction in PCA, generally attributed to a lower surface area. By reducing the films' feature size to the nanoscale, an immobilized photocatalyst with high surface area can be achieved. At this scale, however, feature structuring and morphology become important as they determine the interaction between light and the photocatalytic material. In this work, nanostructured ZnO films with different morphology, arrangement and structure were produced by electrochemical anodization of zinc and were tested using the degradation of phenol in a batch reactor as a model system. Results show that the PCA for immobilized catalysts can be optimised by controlling microscale arrangement (light absorbance capacity) and nanoscale structure (crystal size and orientation) rather than macroscale morphology (surface area). These results provide a clear direction to maximising the photocatalytic activity of immobilised photocatalysts for the removal of organic pollutants from water.

Morphology control of low temperature fabricated ZnO nanostructures for transparent active layers in all solid-state dye-sensitized solar cells

Based on the controlled nanostructured ZnO films, long-term stable solid-state dye-sensitized solar cells with transparent active layers are prepared at low-temperature conditions.

Influence of defects of nanostructured ZnO films on the photovoltaic characteristics of perovskite solar cells

The influence of the defects in ZnO films on the electrical and photovoltaic properties of perovskite solar cells was investigated in the work. According to the results of the research it was established that the defects in ZnO films affects the concentration of defects of perovskite films synthesized on the ZnO surface. However, the difference in the defect concentration in perovskite films is about 30%, while the concentration of defects in ZnO differs by 1000 times. A less significant influence is the concentration of ZnO defects on the electrical and photovoltaic properties of perovskite solar cells. The magnitude of the short-circuit photocurrent and the open voltage of the cells are affected by the concentration of perovskite defects and the quality of the perovskite-ZnO interface.

ZnO nanoparticles and biocidal effect of nanostructured ZnO films on Escherichia coli

The biocidal effect of ZnO nanostructured films was studied using Escherichia coli ATCC 43897. TheZnO nanoparticles were synthesized in diethylene glycol by using zinc acetate forced hydrolysis.X-ray diffraction analysis confirmed the formation of single wurtzite-type ZnO phase with a crystallitesize of 20.59 nm. Transmission electron microscopy observations revealed spherical-shaped particlesin the nanoscale regime with a mean particle size of 21.96 nm. It was found that the addition oftrioctylphosphine during synthesis favored much improved dispersion of ZnO nanoparticles, withsmaller particle size; that is, 16.28 nm. Meanwhile, ZnO film grown onto glass substrate by spin-coatingrevealed single phase with the formation of aggregates (≈700) having mushroom-like morphologyformed of very fine particles in the nanoscale regime. The as-deposited nanostructured films exhibiteda hydrophilic character. The classical bacteriological and electrochemical impedance spectroscopymeasurements enabled the biocidal effect of ZnO nanostructured films with 94% inactivation efficiencyafter 90 min of contact time.

Physical properties of solution processable n-type Fe and Al co-doped ZnO nanostructured thin films: Role of Al doping levels and annealing

The role of annealing temperature and Fe and Al co-doping on structural, optical, electrical and magnetic properties of solution processable ZnO thin films were investigated. ZnO:Fe thin films fixed with 2% of typical ferrous component were obtained to examine the role of 1–10% Al doping. X-ray diffraction analyses clearly indicates that the films to be polycrystalline and preferentially oriented along the c-axis of the hexagonal wurtzite structure. The film thickness, homogeneous distribution and decreasing/increasing of grain size dependence on Al content/annealing temperature (TA) were assessed by scanning electron microscopy. X-ray photoelectron spectroscopy revealed that Al3+ and Fe2+ ions to substitute for Zn2+ without changing the wurtzite structure. A slight decrease in the optical band gap of ZnO at fixed Fe dopant and a considerable increase of the optical band gap with increased Al doping concentrations and TA were observed. The refractive index increases with the fixed Fe dopant level and then decreases by Al doping levels, whereas the extinction coefficient clearly increases depended on both of Fe and Al concentrations. The refractive index and extinction coefficient both decrease with TA. Hall measurements show n-type conductivity and the increase of charge carrier concentration by Al doping levels and TA. Magnetic studies indicate room temperature ferromagnetism in Al and Fe co-doped ZnO thin films, whereas no room temperature ferromagnetism for the Fe-doped ZnO thin films was observed. An enhanced room temperature ferromagnetism in Al and Fe co-doped ZnO thin films was observed to depend on TA.

Effect of reduced graphene oxide on photocatalytic properties of electrodeposited ZnO

ZnO-nanostructured films were obtained by electrodeposition in the presence of varying content of graphene oxide (GO) in reduced (rGO) and non-reduced state. The hybridized ZnO nanostructures were studied by X-ray diffraction measurements, scanning electron microscopy, atomic force microscopy and Raman spectroscopy and transmittance measurements. The results showed the ZnO structure and morphology are markedly influenced by graphene state (GO/rGO) and content. The photocatalytic tests indicated the ability of electrodeposited ZnO-nanostructured films to photodegrade methylene blue depends on the morphology and structure characteristics induced by both on oxygen content and sp2 recovery of carbon network in the rGO, upon a fine tuning of the rGO content in the deposited films. The obtained results demonstrate the electrodeposition as a viable approach for tuning the properties of ZnO complex structures for improved performance in various fields of application such as photocatalysis or optoelectronics.

Shunai Che

Angewandte Chemie International EditionVolume 57, Issue 9 p. 2284-2284 Author ProfileFree Access Shunai Che First published: 17 November 2017 https://doi.org/10.1002/anie.201711485AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “The secret of being a successful scientist is to question any known results and conclusions. My favorite molecule is DNA, with the most beautiful structures and amazing functionalities ...” This and more about Shunai Che can be found on page 2284. Shunai Che The author presented on this page has recently published her 10th article in Angewandte Chemie in the last 10 years: “Silica Scaffold with Shifted ‘Plumber's Nightmare’ Networks and their Interconversion into Diamond Networks”: W. Mao, X. Cao, Q. Sheng, L. Han, S. Che, Angew. Chem. Int. Ed. 2017, 56, 10670; Angew. Chem. 2017, 129, 10810. Date of birth: August 2, 1964 Position: Professor, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University E-mail: chesa@sjtu.edu.cn; chesa@tongji.edu.cn Homepage: http://che.sjtu.edu.cn Education: 1984 Undergraduate degree, Jilin Institute of Chemical Technology 2002 PhD supervised by Takashi Tatsumi, Yokohama National University 2002–2003 Research fellowship, Yokohama National University Awards: 2015 International Mesostructured Materials Association Award; 2015 First Prize, Natural Science Award, Chinese Ministry of Education Research: Chiral inorganic materials, mesoporous materials Hobbies: Living environment design, including rooms, furniture, and clothing; housework The secret of being a successful scientist is to question any known results and conclusions. My favorite molecule is DNA, with the most beautiful structures and amazing functionalities. If I had one year of paid leave I would like to serve as a volunteer teacher to educate poor children. If I could be a piece of lab equipment, I would be a beaker. The most important thing I learned from my students is that to err is human and in errors we learn. What I appreciate most about my friends is that we share the same feeling and ideas. Science is fun because unexpected things always happen. The most important future applications of my research are expected to be in catalysis, separation, and optical devices. If I could be any age, I would like to be 40. I admire people who thinking of others first rather than themselves. I advise my students to be happy in their work. My favorite way to spend a holiday is to stay in a quiet place in the countryside. My 5 top papers: 1“A novel anionic surfactant templating route for synthesizing mesoporous silica with unique structure”: S. Che, A. E. Garcia-Bennett, T. Yokoi, K. Sakamoto, H. Kunieda, O. Terasaki, T. Tatsumi, Nat. Mater. 2003, 2, 801. (Controlled formation of micelles that template frameworks of highly ordered mesoporous materials.) 2“Synthesis and characterization of chiral mesoporous silica”: S. Che, Z. Liu, T. Ohsuna, K. Sakamoto, O. Terasaki, T. Tatsumi, Nature 2004, 429, 281. (An inorganic helical structure that implies a natural relation between organic and inorganic systems.) 3“Synthesis of a DNA–Silica Complex with a Rare Two-Dimensional-Square p4mm Symmetry”: C. Jin, L. Han, S. Che, Angew. Chem. Int. Ed. 2009, 48, 9268; Angew. Chem. 2009, 121, 9432. (The rod-shaped complexes are in an unusual non-close-packed structure because of their helical nature.) 4“Synthesis of chiral TiO2 nanofibre with electron transition-based optical activity”: S. Liu, L. Han, Y. Duan, S. Asahina, O. Terasaki, Y. Cao, B. Liu, L. Ma, J. Zhang, S. Che, Nat. Commun. 2012, 3, 1215. (Helically stacked achiral inorganic nanoparticles also induce optical chirality.) 5“Optically Active Nanostructured ZnO Films”: Y. Duan et al., Angew. Chem. Int. Ed. 2015, 54, 15170; Angew. Chem. 2015, 127, 15385. (Hierarchical chirality where multihelical inorganic structures result in a cooperative enhancement of optical activity.) Volume57, Issue9February 23, 2018Pages 2284-2284 ReferencesRelatedInformation