Effect of water vapor on the thermal decomposition process of zinc hydroxide chloride and crystal growth of zinc oxide

Thermal decomposition process of zinc hydroxide chloride (ZHC), Zn₅(OH)₈Cl₂·H₂O, prepared by a hydrothermal slow-cooling method has been investigated by simultaneous X-ray diffractometry and differential scanning calorimetry (XRD-DSC) and thermogravimetric-differential thermal analysis (TG-DTA) in a humidity-controlled atmosphere. ZHC was decomposed to ZnO through β-Zn(OH)Cl as the intermediate phase, leaving amorphous hydrated ZnCl₂. In humid N₂ with P_H2O=4.5 and 10 kPa, the hydrolysis of residual ZnCl₂ was accelerated and the theoretical amount of ZnO was obtained at lower temperatures than in dry N₂, whereas significant weight loss was caused by vaporization of residual ZnCl₂ in dry N₂. ZnO formed by calcinations in a stagnant air atmosphere had the same morphology of the original ZHC crystals and consisted of the c-axis oriented column-like particle arrays. On the other hand, preferred orientation of ZnO was inhibited in the case of calcinations in 100% water vapor. A detailed thermal decomposition process of ZHC and the effect of water vapor on the crystal growth of ZnO are discussed.     

ZnO/MgO nanocomposites generated from alcoholic solutions

A process was proposed for the synthesis of ZnO/MgO nanocomposites from alcoholic solutions by means or the consecutive precipitation of coprecipitation of alcoholic solutions of zinc acetate and magnesium with an alkali solution followed by annealing in the range 400–500°C. X-ray powder diffraction showed crystalline ZnO and MgO phases in the resulting composite. Zinc oxide particle sizes in the composite with magnesium oxide were determined by transmission electron microscopy and from X-ray diffraction peak broadening. The zinc oxide nanoparticle size was weakly affected by the molar ratio of zinc to magnesium and the concentration of the precipitated component. The ZnO exciton peak in cathodoluminescence spectra for nanocomposites synthesized at low temperatures (400 and 500°C) shifted toward the UV. At ≥600°C or higher, Mg_{1 ? x} Zn _x O solid solution was generated, as evidenced by X-ray diffraction and cathodoluminescence data.     

A simple method for systematically controlling ZnO crystal size and growth orientation

We present a simple, easy and reproducible method to systematically control the dimension and shape evolution of zinc oxide (ZnO) as thin film on glass substrate by chemical bath deposition (CBD). The only varying factor to control crystal transformation is the molar ratio of Cd²⁺/Zn²⁺, R_m, in the initial chemical solution. With the increase of R_m, ZnO crystals transformed from long-and-slim hexagonal rods to fat-and-short hexagonal pyramids, and then to twinning hexagonal dots as observed by scanning electron microscopy (SEM). Film crystallinity was characterized by X-ray diffraction (XRD). Chemical component analysis by energy dispersive spectroscopy (EDS) showed that most cadmium was present in the residual solution instead of the developed film and the precipitate at the bottom of beaker. The mechanism of the cadmium effect, with different initial concentrations, on ZnO crystal transformation was tentatively addressed. We believe that cadmium influences the chelate ligands adsorption onto plane of ZnO crystals, alters the crystal growth orientation, and thus directs the transformation of the size and shape of ZnO crystals.     

Formation of nanocrystalline ZnO particles into bacterial cellulose pellicle by ultrasonic-assisted in situ synthesis

Nanocrystalline zinc oxide particles were synthesized and simultaneously incorporated into a three-dimensional nanofibrous matrix of bacterial cellulose (BC) pellicles by a newly created method called “ultrasonic-assisted in situ synthesis”. The BC pellicles were first immersed in a zinc acetate solution. Then the Zn²⁺-absorbed BC pellicle was further immersed in ammonium hydroxide solution with simultaneous ultrasonic treatment. The effect of immersion time of the BC pellicles in zinc acetate solution and ultrasonic treatment time on crystalline size and percent incorporation of ZnO into the BC pellicles were determined. The crystalline size of ZnO incorporated in BC pellicles was in the range of ~54–63 nm that were similar to the diameter of BC nanofibrils. The amount of ZnO into the BC pellicles was found to increase with increasing immersion time. A longer ultrasonic treatment time resulted in smaller crystalline size of the incorporated ZnO. The particle size, morphology and dispersion of the synthesized ZnO in the BC matrix were examined by transmission electron microscope and scanning electron microscope with inbuilt energy dispersive X-ray analysis. The mechanism of the formation of the nanocrystalline ZnO particles onto the BC nanofibrils was discussed. Moreover, the antibacterial activity of the nanocrystalline ZnO particle-incorporated BC sheet against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) was also evaluated.     

Electrodeposition of ZnO coatings from aqueous Zn(NO3)2 baths: effect of Zn concentration, deposition temperature, and time on orientation

Cathodic reduction of zinc nitrate solution results in the deposition of ZnO crystallites with a strong c-axis orientation. The orientation of crystallites can be switched to 10l (l?=?1, 2, 3) direction by varying the bath concentration (0.04–0.1?M) and the deposition conditions (T, 50–70?°C; t, 30–90?min). The range of concentrations yielding c-axis orientation can be widened at a high deposition temperature. At 0.1?M bath concentration and long deposition times, crystallites are oriented along 10l (l?=?3) direction. At low temperature (50?°C), 100 oriented nanostructured ZnO coatings are obtained (crystallite size, 20–35?nm). The c-axis-oriented crystallites grow as hexagonal columns perpendicular to substrate and 10l-oriented crystallites grow tilted at different angles to the substrate surface.     

Tuning physical surface properties of tin dioxide nanopowders using zinc oxide as template

With a view to energetic and (opto)electronic applications, tin (IV) oxide (SnO₂) nanoparticles have been successfully prepared at the nanoscale by a templating approach based on the use of zinc (II) oxide (ZnO) as template. The procedure consisted in preparing a mixture of tin precursor and template, subsequently calcined at 650 °C under air to lead to the formation of a SnO₂/ZnO composite material. Finally, the material was washed with an alkali solution to remove the template. The template/tin precursor mass ratio was varied in order to tailor the tin (IV) oxide material, especially with a view to main particle size. The resulting SnO₂ nanomaterials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption and electron microscopy. The tin (IV) oxide nanomaterial exhibited enhanced textural and physical surface properties (particle size, surface area, pore size) correlated to an increasing template/tin precursor mass ratio. For instance, from optimized experimental conditions, the specific surface area and pore volume were heightened twofold, reaching values of 49 m²/g and 0.32 cm³/g, respectively.     

Influence of temperature on curative interactions with the participation of metal carboxylates as adhesive promoters: the interactions of Cu(II) hexadecanoate with stearic acid,N,N′-dicyclohexylbenzothiazole-2-sulfenamide,sulfur and zinc oxide

The influence of temperature on the interactions between Cu(II) hexadecanoate (CuC₁₆) and N,N′-dicyclohexylbenzothiazole-2-sulfenamide (DCBS), stearic acid, sulfur and zinc oxide (ZnO) were studied by differential scanning calorimetry, infrared spectroscopy, electron paramagnetic resonance spectroscopy and X-ray analysis in the absence of rubber. Comparison of the results reveals that in most cases physical processes (dissolution, melting) occurred in the studied systems.However, the most favorable thermal reaction appears to be the formation of Cu(II) complexes with DCBS (or DCBS fragments) and the formation of zinc stearate in the presence of stearic acid and ZnO on the action of heat.     

化学气相输运法(CVT)制备微米级的喇叭管状ZnO晶体

氧化锌为直接带隙宽禁带半导体材料,由于其优良的光电性能,预计在未来光电信息领域有着巨大的应用前景,引起了广泛的研究兴趣.     

Synthesis of hydrophobic zinc borate nanoflakes and its effect on flame retardant properties of polyethylene

Zinc borate (2ZnO·3B₂O₃·3.5H₂O) has relatively high dehydration on-set temperature which property permits processing in a wide range of polymer system. But zinc borate particles are hardly dispersed in a polymer matrix so that they prevent their using in industry. To address this problem, we synthesized hydrophobic zinc borate (2ZnO·3B₂O₃·3.5H₂O) nanoflakes by employing solid-liquid reaction of zinc oxide (ZnO) and boric acid (H₃BO₃) in the presence of oleic acid. This method does not bring pollution. By conducting morphological and microscopic analyses, we found that this compound displayed nanoflake morphology with particle size of around 100-200 nm, thickness less than 100 nm and there were uniform mesopores with the diameter about 10 nm within the particles. Furthermore, our products had an effect on flame retardant of polyethylene, especially when the zinc borate was modified by oleic acid.     

Structures and optical properties of Zn1?x Ni x O nanoparticles by coprecipitation method

Nanocrystals of undoped and nickel-doped zinc oxide (Zn_1?x Ni _x O, where x?=?0.00?C0.05) were synthesized by the coprecipitation method. Crystalline size, morphology, and optical absorption of prepared samples were determined by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and UV?Cvisible spectrometer. XRD and SEM studies revealed that Ni-doped ZnO crystallized in hexagonal wurtzite structure. Doping of ZnO with Ni²⁺ was intended to enhance the surface defects of ZnO. The incorporation of Ni²⁺ in place of Zn²⁺ provoked an increase in the size of nanocrystals as compared to undoped ZnO. Crystalline size of nanocrystals varied from 10 to 40?nm as the calcination temperature increased. Enhancement in the optical absorption of Ni-doped ZnO indicated that it can be used as an efficient photocatalyst under visible light irradiation. Optical absorption measurements indicated a red shift in the absorption band edge upon Ni doping. The band gap value of prepared undoped and Ni-doped ZnO nanoparticles decreased as annealing temperature was increased up to 800?°C.     

Fabrication,characterization and exploration of cobalt (II) ion doped,modified zinc oxide thick film sensor for gas sensing characteristics of some pernicious gases

The present research deals with the synthesis of zinc oxide (ZnO) nanoparticles by the co-precipitation (CPT) method. The CPT method was successfully utilized for the synthesis of ZnO nanoparticles. The structural properties of undoped ZnO and cobalt doped ZnO were confirmed by employing an X-ray diffraction (XRD) study, from which the average particle size for each prepared material was calculated from the Debye Scherer formula. The average particle size confirms the nano range fabrication of undoped and cobalt doped ZnO material. The surface characteristics, morphology, texture, and porosity properties of undoped ZnO and cobalt doped ZnO were investigated from scanning electron microscopy (SEM). The elemental composition was investigated from energy dispersive spectroscopy (EDS). The High-resolution transmission electron microscopy (HRTEM) results revealed the hexagonal phase of prepared material. Furthermore, the undoped ZnO and 5% cobalt doped ZnO gas sensors prepared by screen printing technology were utilized for gas sensing purposes for testing the gases like H₂S, NO₂, SO₂, and methanol. For the gases examined, the cobalt modified ZnO sensor proved to be quite effective, especially for H₂S and NO₂ gas vapors. The Co²⁺ doped ZnO sensor showed 70.12% sensitivity for H₂S gas at 150 ⁰C and 68.75% gas response for NO₂ gas vapors at 120 ⁰C. In addition, the cobalt modified sensor was also investigated for reusability test to get concrete gas response results with the time interval of 15 days. In conclusion, it can be mentioned that the cobalt doped ZnO thick film sensor is a promising sensor for H₂S and NO₂ gas vapors.     

EPR of Mn2+ in single crystals of calcium hexachlorostannate hexahydrate

An EPR study has been carried out on Mn²⁺-doped single crystals of calcium hexachlorostannate hexahydrate [Ca(H₂O)6] SnCl₆ in the temperature range 77–378 K at X-band frequencies (9.3 GHz). Mn²⁺ ions substituting the divalent metal exhibit a unique magnetic complex with the z-axis directed along the c-axis of the crystal. The temperature dependence of the zero-field splitting parameter is discussed.     

Synthesis and Characterization of Zinc Oxide Nano-particles by Solid State Chemical Reaction Method

Several important synthetic parameters such as precursor concentration, reaction time are found to determine the growth of ZnO nanostructures. These reaction parameters can be tuned to produce a variety size of nanostructures. In this work we show the importance of these parameters on the size of synthesized zinc oxide nano-powders. ZnO nanoparticles are synthesized by the solid-state reaction using ZnSO₄·7H₂O and NaOH as the reagents. In this method Zn(OH)₂ is the intermediate product of the reaction, we show that by adjusting the molar ratio of the reagents and grinding time, we can be removed this unwanted component in the final product so for obtaining pure ZnO nanostructures the calcinations process is not necessary, also we can tune the size of ZnO nanoparticles. XRD spectra of the nanoparticles demonstrate typical diffraction peaks of a well-crystalline Wurtzite ZnO structure transmission electron microscopic observations show that these nanoparticles are of hexagonal phase ZnO mostly in round shapes and he composition analysis by EDX indicate that final product is pure ZnO. In the optimum conditions by XRD analysis we see that the mean grain size of synthesized zinc oxide nano-particles is about 44 nm.     

Reactivity of nanoparticles; interaction between zinc and copper oxide nanoparticles and iron ions in an alkaline medium

The reactivity of zinc and copper oxide nanoparticles was investigated upon their interaction with iron oxides. It was ascertained that, depending on the reaction conditions, nanoparticles of zinc and copper ferrites (ZnFe₂O₄ and CuFe₂O₄) or core/shell nanoparticles (Fe₃O₄/ZnO) are produced. Size, composition, and structure of the resulting nanoparticles were determined by transmission electron microscopy and X-ray diffraction analysis. The average size of zinc and copper ferrite nanoparticles was ascertained to be 9–10 and 2–3 nm, respectively. For core/shell Fe₃O₄/ZnO nanoparticles, the average size is 20 nm. It was experimentally proved that the photoluminescence radiative characteristics of ZnO nanoparticles are retained in core/shell Fe₃O₄/ZnO nanoparticles.     

Microwave assisted hydrothermal synthesis of zinc hydroxystannate films on glass substrates

Zinc stannate (ZnSnO₃, Zn₂SnO₄) and its precursor, i.e. zinc hydroxystannate (ZnSn(OH)₆), have emerged as technological nanomaterials for different applications. Herein, we report synthesis of polycrystalline zinc hydroxystannate (ZHS) film on glass substrate through facile and efficient microwave assisted hydrothermal growth. The method comprises of three steps; deposition of ZnO seed films on glass substrates through spray pyrolysis, growth of ZnO nanorod arrays over the seeded substrates through microwave assisted hydrothermal method and transformation of the as-synthesized ZnO nanorod arrays into the ZHS films through microwave treatment in aqueous precursor solution of SnCl₄ and NaOH. The films were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction and scanning electron microscopy (SEM). The films contain two crystalline phases namely ZnO with [002] as preferred growth direction and ZnSn(OH)₆ preferably grown along [200] vector. The obtained ZHS films consist of crystals of exclusively cubic structure with sizes up to several microns. Microwave irradiation time, NaOH/SnCl₄ molar ratio, concentration of Sn⁴⁺ ions, and the applied power are the four parameters which influence the size, aerial density and growth rate of ZHS microblocks.     

Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction

Well-crystallized zinc oxide nanorods have been fabricated by single step solid-state reaction using zinc acetate and sodium hydroxide, at room temperature. The sodium lauryl sulfate (SLS) stabilized zinc oxide nanorods were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. The X-ray diffraction revealed the wurtzite structure of zinc oxide. The size estimation by XRD and TEM confirmed that the ZnO nanorods are made of single crystals. The growth of zinc oxide crystals into rod shape was found to be closely related to its hexagonal nature. The mass ratio of SLS:ZnO in the nanorods was found to be 1:10 based on the thermogravimetric analysis. Blue shift of photoluminescence emission was noticed in the ZnO nanorods when compared to that of ZnO bulk. FT-IR analysis confirmed the binding of SLS with ZnO nanorods. Apart from ease of preparation, this method has the advantage of eco-friendliness since the solvent and other harmful chemicals were eliminated in the synthesis protocol.     

Synthesis of Zinc Oxide Nanoparticles Using Rubus fairholmianus Root Extract and Their Activity against Pathogenic Bacteria

Recently, the biosynthesis of zinc oxide nanoparticles (ZnO NPs) from crude extracts and phytochemicals has attracted much attention. Green synthesis of NPs is cost-effective, eco-friendly, and is a promising alternative for chemical synthesis. This study involves ZnO NPs synthesis using Rubus fairholmianus root extract (RE) as an efficient reducing agent. The UV spectrum of RE-ZnO NPs exhibited a peak at 357 nm due to intrinsic bandgap absorption and an XRD pattern that matches the ZnO crystal structure (JCPDS card no: 36-1451). The average particle size calculated from the Debye–Scherrer equation is 11.34 nm. SEM analysis showed that the RE-ZnO NPs spherical in shape with clusters (1–100 nm). The antibacterial activity of the NPs was tested against Staphylococcus aureus using agar well diffusion, minimum inhibitory concentration, and bacterial growth assay. The R. fairholmianus phytochemicals facilitate the synthesis of stable ZnO NPs and showed antibacterial activity.     

Electrochemical/chemical synthesis of highly-oriented single-crystal ZnO nanotube arrays on transparent conductive substrates

Arrays of ZnO nanotube (ZNT) were prepared by a two-step electrochemical/chemical process on a transparent, conductive substrate from an aqueous solution at 85 °C. The as-grown ZNTs are single crystals with wurtzite structure and have good crystalline state. The tubular morphology was formed by the proton generated from anodic splitting of water and defect-selective etching of the electrodeposited ZnO nanorod (ZNR) along the c-axis. The photoluminescence and cathodoluminescence spectra of the ZNT arrays show two emission bands located in the ultraviolet (UV) and visible region, respectively. It was found that the PL intensity in the UV band as well as the ratio of I_uv/I_visible increased with increasing of the excitation intensity.     

Preferential growth orientation of laser-patterned LiNbO3 crystals in lithium niobium silicate glass

Dots and lines consisting of LiNbO₃ crystals are patterned on the surface of 1CuO-40Li₂O-32Nb₂O₅-28SiO₂ (mole ratio) glass by irradiations of continuous-wave Nd:YAG laser (wavelength: λ=1064 nm), diode laser (λ=795 nm), and Yb:YVO₄ fiber laser (λ=1080 nm), and the feature of laser-patterned LiNbO₃ crystal growth is examined from linearly polarized micro-Raman scattering spectrum measurements. LiNbO₃ crystals with the c-axis orientation are formed at the edge parts of the surface and cross-section of dots. The growth direction of an LiNbO₃ along the laser scanning direction is the c-axis. It is proposed that the profile of the temperature distribution in the laser-irradiated region and its change along laser scanning would be one of the most important conditions for the patterning of crystals with a preferential growth orientation. Laser irradiation giving a narrow width is also proposed to be one of the important factors for the patterning of LiNbO₃ crystal lines with homogeneous surface morphologies.