Piezoelectricity of ZnO Films Prepared by Sol-Gel Method

"ZnO piezoelectric thin films were prepared on crystal substrate Si(111) by sol-gel technology, then characterized by scanning electron microscopy, X-ray diffraction and atomic force microscopy (AFM). The ZnO films characterized by X-ray diffraction are highly oriented in (002) direction with the growing of the film thickness. The morphologies, roughness and grain size of ZnO film investigated by AFM show that roughness and grain size of ZnO piezoelectric films decrease with the increase of the film thickness. The roughness dimension is 2.188-0.914 nm. The piezoelectric coeocient d33 was investigated with a piezo-response force microscope (PFM). The results show that the piezoelectric coeocient increases with the increase of thickness and (002) orientation. When the force reference is close to surface roughness of the films, the piezoelectric coefficient measured is inaccurate and fluctuates in a large range, but when the force reference is big, the piezoelectric coeocient d33 changes little and ultimately keeps constant at a low frequency."     

UV Curable Hard Transparent Hybrid Coating Materials on Polycarbonate Prepared by the Sol-Gel Method

UV curable, hard, transparent inorganic/organic composites with covalent links between the inorganic and the organic networks were prepared by the sol-gel method. These hybrid coating materials were synthesized using a commercially available, acrylate end-capped polyester or polyurethane oligomeric resin (EBC80, EBC284), hexanedioldiacrylate (HDDA) as a reactive solvent, 3-(trimethoxysilyl)propoxymethacrylate (TMSPM) as a coupling agent between the organic and inorganic phase, and a metal alkoxide, tetraethylorthosilicate (TEOS). The materials were applied on primer or oxygen plasma pretreated polycarbonate sheets and UV cured, followed by a thermal treatment to give a transparent coating with a good adhesion and abrasion resistance. The high transmission and the thermogravimetric behavior indicate the presence of a nanoscale hybrid composite, as is confirmed by SAXS and TEM measurements. In a Taber Abrasion Test, uncoated polycarbonate sheets exhibit a 48% decrease in light transmittance at 600 nm after 300 wear cycles, whereas the EBC80 hybrid coating system containing 9 wt% SiO₂ (EBC80/25Si) shows only 28% decrease in light transmittance. A maximal improvement of the abrasion resistance is achieved when 23 wt% SiO₂ is incorporated (EBC80/60Si, EBC284/60Si) with only 20% decrease in light transmittance. The abrasion resistance of glass is not yet encountered. For optimal results, it is essential that the rate of condensation of the silanol groups is sufficiently high to form a dense three-dimensional network.     

基于ZnO溶胶-凝胶固定的酪氨酸酶传感器的研制

通过使用带正电荷的ZnO溶胶-凝胶在玻碳电极表面固定酶,研制了一种简单有效的酪氨酸酶传感器。结果表明,ZnO溶胶-凝胶的等电点为酪氨酸酶的固定提供了有利的微环境,酪氨酸酶能很好地保持其生物活性。所研制的传感器达到95%稳定状态电流的时间在10 s以内。酚类化合物可通过酶催化产生的醌在-200 mV(对饱和甘汞电极)直接还原而测定,传感器对苯酚测定的灵敏度为168μA.mmol-1.L-1,线性范围为1.5×10-7~4.0×10-5mol.L-1,检出限为8.0×10-8mol.L-1。该传感器使用二周后活性仍保持原有活性的75%。     

Crystallization Behavior and Properties of B-Doped ZnO Thin Films Prepared by Sol-Gel Method with Di erent Pyrolysis Temperatures

Boron-doped zinc oxide transparent (BZO) films were prepared by sol-gel method. The effect of pyrolysis temperature on the crystallization behavior and properties was systematically investigated. XRD patterns revealed that the BZO films had wurtzite structure with a preferential growth orientation along the c-axis. With the increase of pyrolysis temperature, the particle size and surface roughness of the BZO films increased, suggesting that pyrolysis temperature is the critical factor for determining the crystallization behavior of the BZO films. Moreover, the carrier concentration and the carrier mobility increased with increasing the pyrolysis temperature, and the mean transmittance for every film is over 90% in the visible range.     

Gasochromic Effect in Platinum-Doped Tungsten Trioxide Films Prepared by the Sol-Gel Method

Tungsten oxide doped by a complex of platinum exhibits a gasochromic effect. A reversible coloration is observed on successive exposure to hydrogen and air. The films were prepared by the sol-gel method at room temperature. They showed strong darkening (blue color) on exposure to hydrogen and were bleached completely when exposed to air. The proccess has been reproduced completely hundreds of times without any losses. The cycling of the coloration was obtained from UV-Vis spectra and the mechanism deduced from both visible and Fourier transform infrared (FTIR) spectra. Colorimetric properties of the gasochromic films were expressed in color space chromaticity diagram.     

ZnO纳米棒薄膜的湿化学法制备及光致发光特性

在80 ℃水浴下, 采用简易的湿化学法在不导电玻璃基底上制备了ZnO纳米棒阵列, 利用X射线衍射仪(XRD)和场发射扫描电镜(FE-SEM)对样品的结构形貌进行了表征. 结果表明, 晶化30 min所得产物为六方纤锌矿相的ZnO纳米棒, 直径大约为80~90 nm. 为了分析不同的低温退火温度和退火气氛对其光致发光性能的影响, 研究了ZnO纳米棒薄膜在不同的后处理条件下的光致发光谱(PL). 实验结果表明, 在O₂气氛下于450 ℃退火1 h后, ZnO纳米棒薄膜的红光发射(约650 nm)强度相对在空气和5%H₂/95%N₂气氛下退火的样品变得更强, 而且该样品的激发波长范围(200~370 nm)与近紫外发光二极管(LEDs)的发射波长范围(350~420 nm)匹配得很好.     

Preparation of Superhydrophobic ZnO Films on Zinc Substrate by Chemical Solution Method

Superhydrophobic surface was prepared on the zinc substrate by chemical solution method via immersing clean pure zinc substrate into a water solution of zinc nitrate hexahydrate[Zn(NO₃)₂·6H₂O] and hexamethylenetetraamine( C₆H₁₂N₄) at 95 ℃ in water bath for 1.5 h, then modified with 18 alkanethiol. The best resulting surface shows superhydrophobic properties with a water contact angle of about 158° and a low water roll-off angle of around 3°. The prepared samples were characterized by powder X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy(EDX), transmission electron microscopy(TEM), and scanning electron microscopy(SEM). SEM images of the films show that the resulting surface exhibits flower-shaped micro- and nano-structure. The surfaces of the prepared films were composed of ZnO nanorods which were wurtzite structure. The special flower-like micro- and nano-structure along with the low surface energy leads to the surface superhydrophobicity.     

Inhibition of Pb-Leaching from Lead Crystal Glass by Coating with Films Prepared by the Sol-Gel Method

The chemical durability of lead glass tumblers (24% PbO) in a 4% (v/v) acetic acid solution before and after coating with sol-gel derived SiO2 films was assessed to determine the extent of reduction in Pb-leaching that can be achieved. It was found that by coating the internal surface of the glass tumblers with 1 ml of 10% TEOS solutions at 100°C and densifying the coating formed at 500°C for 1 h, it was possible to reduce Pb-leaching to about one quarter of that of the uncoated glass.     

Studies on the Structure of Gel during Preparing ZnO Thin Films by Sol-gel Method

<正>Transparent thin films of ZnO have been prepared on ordinary glass substrates by the inorganic sol-gel method using citric acid as chelating agent and zinc nitrate as the starting material.A novel structure on zinc citrate complex was put forward by using DTA-TG and FT-IR absorbance spectrum of citrate gels.Phase formation,morphology and optical properties of ZnO films are investigated by XRD,AFM and UV-vis transmittance spectra.The experimental results show that ZnO thin films derived from zinc citrate sol-gel method showed a(002)oriented hexagonal wurtzite structure,good crystalline property,a uniform range of grain size(40 nm), smooth surface of films,band gap of 3.28 eV and optical transmittances ratio over 90%in the visible range.     

Low Dielectric Constant Organosilicate Films Prepared by Sol-Gel and Templating Methods

Low dielectric constant organosilicate films with controllable microstructure have been successfully synthesized by multiple-step sol-gel process and templating method, which are the two basic methods to establish porous network in the films. Ultra-low dielectric constant (k) of around 2.0 can be achieved for both films. The microstructure such as porosity, pore interconnection and pore size of the two types of the films have been studied and compared. It has been found that the sol-gel films have a higher level of porosity comparing to the templating films to obtain the same k value. The sol-gel film has a majority of closed pores with pore size around 5 nm. The templating film has a closed pore structure with pore size around 10 nm. Preliminary results present a very positive prospective for intermetal dielectric applications.     

Determination of Catechol by a Novel Laccase Biosensor Based on Zinc-Oxide Sol-Gel

A biosensor was fabricated by incorporating laccase in a ZnO sol-gel with chitosan as a matrix for the determination of catechol. The ZnO nanoparticles were characterized by X-ray diffraction and atomic force microscopy. The conductivity of the chitosan/ZnO/glassy carbon electrode film was investigated by alternating current impedance. The biosensor was employed to monitor the reduction of catechol, and the peak current increased linearly with concentration between 1.0 × 10^?6 and 1.0 × 10^?4 mole per liter with a limit of detection of 2.9 × 10^?7 mole per liter. The laccase biosensor exhibited good stability, reproducibility, and some selectivity.     

Vanadium-Based Organic-Inorganic Hybrid Materials Prepared by a Sol-Gel Method

Synthesis and characterization of hybrid organic-inorganic nanocomposites based on reaction of vanadium i-propoxide with an organically functionalized poly(ethylene glycol) having di-carbonyl groups is reported. The bulk gels were characterized by thermal analyses (DSC, TGA and TMA) and FT-IR spectroscopy. The results revealed that the gels consist of vanadium-oxygen-vanadium groupings which are cross-linked with the functionalized polymer through the di-carbonyl groups. Gels doped with lithium salt show significant electrical conductivity.     

Study on the nanoscale current of ZnO film by photoassisted peak force tunnel atomic force: A novel technique for UV detection

ZnO film-based ultraviolet (UV) detector was fabricated by photoassisted peak force tunnel atomic force (PFTUNA) on fluorine tin oxide (FTO) substrate. The PFTUNA current in dark and in UV light was ~0.1 and 2.0 nA, respectively. The UV sensitivity (photocurrent/dark current) is more than 20. The response time and the recovery time are ~0.12 and 0.32 s, respectively. The UV sensing mechanism is that the holes will transport to the ZnO surface to capture the adsorbed oxygen ions to weaken the depletion layer under UV illumination. The PFTUNA current between the tip and the ZnO film is consistent with the Richardson–Schottky (RS) thermionic emission model.     

Atomic Force Microscopic Studies of Porous TiO2 Thin Films Prepared by the Sol-Gel Method

Porous titanium dioxide thin films were prepared from alkoxide solutions with and without polyethylene glycol (PEG) by the sol-gel method on soda-lime glass. The effects of PEG addition to the precursor solution on the microstructure and roughness of the resultant thin films were investigated by atomic force microscopy (AFM). It was found that TiO₂ films prepared from the precursor solution without PEG had granular microstructure and flat texture, and was composed of about 100 nm spherical particles. With an increase in the times of coating cycles, the roughness of films decreased and the size of TiO₂ particles increased. On the other hand, the larger the amount and molecular weight of the added PEG in precursor solutions, the larger the diameter and the depth of pores in the resultant films on the decomposition of PEG during heat-treatment. The surface of the films was also rougher, and fewer pores were produced during heat-treatment. The mechanism of porous structure formation in the TiO₂ films was explained using the principle of spinodal phase separation.     

溶胶凝胶辅助水热可控合成ZnO不同形貌分级结构光催化剂

以Zn(NO3)2·6H2O、柠檬酸和Na OH为原料,采用溶胶凝胶(sol-gel)辅助水热法,仅通过改变水热时间,就可得到片花、棒花及梭状3种不同形貌ZnO分级结构。利用XRD、SEM、UV-Vis DRS、光致发光光谱(PL)和氮低温吸附-脱附等手段对合成的ZnO样品进行了表征。推测了合成条件下不同形貌ZnO分级结构形成的机理。以活性翠兰(KGL)为模拟印染废水,考察了其光催化活性。结果表明,虽然所合成的不同形貌的ZnO样品在光照120 min后均能使KGL降解78%以上,但其中水热4 h得到的片花状ZnO光催化性能最好,可降解99%的KGL,这与其片花状的形貌、较大的比表面积、较多的表面氧缺陷和极性面有关。     

溶胶凝胶辅助水热可控合成ZnO不同形貌分级结构光催化剂

以Zn(NO₃)₂·6H₂O、柠檬酸和NaOH为原料,采用溶胶凝胶(sol-gel)辅助水热法,仅通过改变水热时间,就可得到片花、棒花及梭状3种不同形貌ZnO分级结构。利用XRD、SEM、UV-Vis DRS、光致发光光谱(PL)和氮低温吸附-脱附等手段对合成的ZnO样品进行了表征。推测了合成条件下不同形貌ZnO分级结构形成的机理。以活性翠兰(KGL)为模拟印染废水,考察了其光催化活性。结果表明,虽然所合成的不同形貌的ZnO样品在光照120 min后均能使KGL降解78%以上,但其中水热4 h得到的片花状ZnO光催化性能最好,可降解99%的KGL,这与其片花状的形貌、较大的比表面积、较多的表面氧缺陷和极性面有关。     

Characterisation and Catalytic Properties of Vanadium Oxide Supported on Alumina Prepared by Sol-Gel Method

Vanadia-alumina xerogels were prepared by sol-gel method using organic precursors of metal and acetic acid as hydrolysis source. The purpose of this work is to study the change in the structure of dispersed vanadia as a function of preparation parameters, mainly the hydrolysis ratio k = [CH₃COOH]/[Al(O-s-Bu)₃] and the vanadium content V/V + Al (%).The amount of acetic acid affects considerably the solid texture, thus the pore size increases with the k ratio. In the same time, ⁵¹V NMR spectroscopy shows a decrease in the vanadium coordination from six-fold to fourfold. The investigation by temperature programmed reduction (TPR) shows that the reducibility of catalysts is determined in the order: K = 3 > K = 2 > K = 1. Furthermore, the catalytic activity in paraxylen oxidation follows a trend similar to that observed in TPR.The increase of vanadium content from 5 to 10%, favours the association of vanadium monomeric species, resulting in a new surface species. Hence, the coordination of vanadium changes from tetrahedral to octahedral, which induces a fall in partial oxidation selectivity.     

Third-Order Nonlinear Optical Properties and Dielectric Properties of Pb-Complex Perovskite Thin Films Prepared by Sol-Gel Method

The third-order nonlinear optical properties of the sol-gel derived Pb(Fe_1/2Nb_1/2)O₃-PbTiO₃ (PFN-PT) thin films have been investigated by the THG method. The χ⁽³⁾ values of PFN-PT thin films increased from 3.2×10⁻¹² esu (PT) to 8.5×10⁻¹² esu (PFN) with increasing content of Fe³⁺ ions which possessed very high second-hyperpolarizability, ψ(Fe_2/3O). It was experimentally confirmed that complex oxides such as ABO₃-type perovskites consisting of large non-transition metal A-site cations and small transition metal B-site cations exhibited high χ⁽³⁾ as expected from Lines' model. It was also found that the χ⁽³⁾ values of complex oxides could be estimated from the second-hyperpolarizabilities of the constituent single oxides reported so far. Because of the large remanent polarization, PT thin films may exhibit the highest χ⁽³⁾ among the ferroelectric PFN-PT thin films studied in the present work. The maximum dielectric constant, ε, of 1990 at room temperature was obtained for 0.5PFN·0.5PT thin films, whose composition corresponds to so-called morphotropic phase boundary (MPB).     

Preparation and Characterization of TiO2 Thin Films by Sol-Gel Method

Titanium dioxide (TiO₂) thin films have been deposited on silicon and glass substrates by the sol-gel process using titanium iso-propoxide [Ti(O-i-C₃H₇)₄]. The bond configuration of the TiO₂ thin films was analyzed by using FTIR in the wavenumber range from 400 to 4000 cm^–1. The spectral transmittance of as-deposited TiO₂ films deposited on fused silica glass was measured in the wavelength range from 200 to 900 nm. X-ray diffraction measurements were performed to determine the crystallinity of the TiO₂ films. As-deposited films were amorphous. As the film was annealed at higher temperature, the structure was transformed from amorphous to the anatase crystalline state. The chemical composition of the deposited film was investigated using X-ray photoelectron spectroscopy (XPS). The films are essentially stoichiometric with carbon as the dominant impurity on the surface. Raman spectra show the characteristic of TiO₂ anatase phase. The electrical properties of the TiO₂ films were measured using capacitance-voltage (C-V) and current-voltage techniques. From C-V measurements, the dielectric constants were calculated to be approximately 26 for the as-deposited films and 75–82 for films annealed at 700°C in different atmosphere. For the as-deposited samples, the breakdown voltage was 2.7 MV/cm, and for an electric field of 1 MV/cm, the leakage current was 5 × 10^–5 A/cm² and the resistivity was 2.2 × 10¹⁰ -cm.     

Preparation and Properties of Anti-Reflection/Anti-Static Thin Films for Cathode Ray Tubes Prepared by Sol-Gel Method Using Photoirradiation

A new technique for preparing anti-reflection/anti-static thin films for CRTs at low temperature has been developed. Double-layered films of SiO₂/SnO₂ were formed on a CRT panel surface by the sol-gel method using photoirradiation. The new method makes it possible to reduce heat treatment temperature (°C) by almost 50% and treatment time to approximately 33% of the conventional levels.