A comparative study of thin films of Zn(O;OH)S and In(O;OH)S deposited on CuInS2 by chemical bath deposition method

In this work, a study of synthesis of thin films of Zn(O;OH)S and In(O;OH)S deposited by chemical bath deposition (CBD) is presented. The thin films of Zn(O;OH)S and In(O;OH)S were deposited from different chemical bath systems on absorber layers of CuInS₂ (CIS), indium tin oxide substrates (ITO) and soda lime glass substrates (SL). The differences on the growth rate, optical, morphological and structural properties of the thin films Zn(O;OH)S and In(O;OH)S are studied. The Growth studies showed that thin films of Zn(O;OH)S and In(O;OH)S grown faster on CIS than on SL and ITO substrates. The optical and morphological studies showed that both thin films present high transmittance in visible electromagnetic spectrum and covered uniformly the surface of the substrate, furthermore it was observed that thin films of Zn(O;OH)S and In(O;OH)S were polycrystalline. Finally, the results suggest that thin films of Zn(O;OH)S and In(O;OH)S obtained in this work could be used as buffer layer to replace the thin films of CdS, which are conventionally used as buffer layer in chalcopyrite based solar cells.     

Synthesis and characterization of Zn(O,OH)S and AgInS2 layers to be used in thin film solar cells

In this paper AgInS₂ and Zn(O,OH)S thin films were synthesized and characterized. AgInS₂ layers were grown by co-evaporation from metal precursors in a two-step process, and, Zn(O,OH)S thin films were deposited from chemical bath containing thiourea, zinc acetate, sodium citrate and ammonia. X-ray diffraction measurements indicated that AgInS₂ thin films grown with chalcopyrite structure, and the as-grown Zn(O,OH)S thin films were polycrystalline. It was also found that the AgInS₂ films presented p-type conductivity, a high absorption coefficient (greater than 10⁴ cm⁻¹) and energy band-gap E_g of about 1.95 eV, Zn(O,OH),S thin films presented E_g of about 3.89 eV. Morphological analysis showed that under this synthesis conditions Zn(O,OH),S thin films coated uniformly the absorber layer. Additionally, the Zn(O,OH)S kinetic growth on AgInS₂ layer was studied also. Finally, the results suggest that these layers possibly could be used in one-junction solar cells and/or as top cell in a tandem solar cell.     

Facile fabrication of Zn/Zn5(OH)8Cl2·H2O flower-like nanostructure on the surface of Zn coated with poly (N-methyl pyrrole)

Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructures was electrodeposited on the coated Zn with poly (N-methyl pyrrole) in 0.1 M Zn (NO₃)₂ and 0.1 M KCl solution. The morphology and the structure of the Zn/Zn₅(OH)₈Cl₂·H₂O were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis (XRD). The FT-IR results showed special peaks at 908 and 728 cm⁻¹ related to Zn₅(OH)₈Cl₂·H₂O. The FESEM results indicated that Zn/Zn₅(OH)₈Cl₂·H₂O consists of a flower-like nanostructure and these flower-shaped structures contain many shaped nanopetals with the thickness of 27.8 nm. The XRD result confirmed that the major phase of electrodeposited product in 0.1 M KCl as supporting electrolyte was Zn₅(OH)₈Cl₂·H₂O. The ability of PMPy to create a thin film and the existence of several pores in its matrix act as a mold for the growth of Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructure. The trapping of Cl⁻ and OH⁻ within pores can be considered as the reason for the formation of flowerlike Zn/Zn₅(OH)₈Cl₂·H₂O nanostructures in 0.1 M KCl.     

Hydrothermal growth and characterization of La(OH)3 nanorods and nanocables with Ni(OH)2 coating

La(OH)₃/Ni(OH)₂ nanocables and La(OH)₃ nanorods were synthesized by the reaction of KOH with La(NO₃)₃ and Ni(NO₃)₂ at 180 °C under a hydrothermal conditions. X-ray diffraction, transmission electron microscopy and thermal analyses indicated that the nanocable consists of La(OH)₃ core and Ni(OH)₂ outer shell. The diameters of the La(OH)₃ nanorods range from 20 to 30 nm and the lengths range from 150 to 1000 nm. The thickness of the Ni(OH)₂ coating ranges from 10 to 20 nm. The formation mechanism of the nanocables is discussed.     

Dynamic scaling and optical properties of Zn（S,O, OH） thin film grown by chemical bath deposition

The scaling behavior and optical properties of Zn(S, O and OH) thin films deposited on soda-lime glass substrates by chemical bath deposition method were studied by combined roughness measurements, scanning electron microscopy and optical properties measurement. From the scaling behaviour, the value of growth scaling exponent β , 0.38±0.06, was determined. This value indicated that the Zn(S, O, OH) film growth in the heterogeneous process was influenced by the surface diffusion and shadowing effect. Results of the optical properties measurements disclosed that the transmittance of the film was in the region of 70%-88% and the optical properties of the film grown for 40 min were better than those grown under other conditions. The energy band gap of the film deposited with 40 min was around 3.63 eV.     

Improved asymmetric electrochemical capacitor using Zn-Co co-doped Ni(OH)2 positive electrode material

The performance of Ni-foam pasted Ni(OH)₂ prepared from co-precipitated Ni(OH)₂ with Zinc (Zn) and Cobalt (Co) as the positive electrode active material of an asymmetric electrochemical capacitor (EC) is studied for the enhancement of the capacitor’s specific energy and power densities. A co-precipitated Ni(OH)₂/activated carbon (AC) composite material and AC were used as a positive and negative electrode material. The AC in the positive electrode is used as an electrolyte reservoir to reduce ionic diffusion resistance regardless of charge/discharge current density. In addition, the simultaneous presence of Zn and Co ions in the Ni(OH)₂ layer improves the efficiency of the active material and reduces the resistance of the unit cell. It was observed that through the effects of the additives in the positive electrode, the asymmetric EC exhibits a high energy density with 35.7 Wh/kg, based on the active material. Furthermore, the energy density decreasing behavior at a high discharge current density was retarded. PACS 81.20.Ev; 73.40.Mr; 66.30.Pa; 66.30.Dn     

Thermo‐Raman spectroscopy of selected layered double hydroxides of formula Cu6Al2(OH)16CO3 and Zn6Al2(OH)16CO3

Raman spectroscopy using a hot stage was used to characterise layered double hydroxides (LDHs) of the formula (Cu,Zn)₆Al₂(OH)₁₆(CO₃)^·4H₂O. The spectra were used to assess the molecular assembly of the cations in the LDH structure. The sharp band at 1058 cm⁻¹for the Zn₆Al₂(OH)₁₆(CO₃)^·4H₂O is assigned to the ν₁CO₃²⁻ symmetric stretching mode. This band shifts to higher wavenumbers and is observed at 1103 cm⁻¹at 600 °C. It is proposed that metal carbonate species formed during the decomposition of the hydrotalcite structure is responsible for the increase in the band position. The Cu–Al hydrotalcite did not show the same trend. The symmetric stretching mode of carbonate is observed at around 1110 cm⁻¹, and at temperatures above 200 °C a shoulder appears at around 1210 cm⁻¹, suggested to be due to CuCO₃. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and investigation of magnetic properties of Gd-substituted Mn–Zn ferrite nanoparticles as a potential low-TC agent for magnetic fluid hyperthermia

Gd-substituted Mn–Zn ferrite nanoparticles of different compositions were synthesized by chemical co-precipitation method. To study the reduction of the Curie temperature (T_C) for different samples, their magnetic properties in dependence from the composition and cationic distribution were investigated. An attempt to lower the T_C of superparamagnetic particles to the optimal temperature required in magnetic fluid hyperthermia (44–47 °C) was made.     

Morphology controlled solvothermal synthesis of Cd(OH)2 and CdO micro/nanocrystals on Cd foil

Cadmium hydroxide (Cd(OH)₂) and cadmium oxide (CdO) nano and micro crystals were synthesized in ethanol-water medium using cadmium foil both as a source and substrate under solvothermal condition. Different concentrations of ammonium hydroxide, hydrazine hydrate, sodium hydroxide and potassium hydroxide were added to study the structural and morphological variations in the products. Synthesis was carried out at different temperatures to study the growth stages of the nano/microstructures. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The as-prepared Cd(OH)₂ products were transformed to CdO by thermal treatment in air. The possible growth mechanism for the formation of different morphologies at different basic medium has been proposed. The optical absorption measurement was carried out to determine the values of the band gap of CdO.     

Synthesis and characterization of Gd(OH)3 nanobundles

Gd(OH)₃ nanobundles, which consisted of bundle-like nanorods, have been prepared through a simple and facile hydrothermal method. The crystal, purity, morphology and structural features of Gd(OH)₃ nanobundles are investigated by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive X-ray (EDX). A possible formation mechanism of Gd(OH)₃ nanobundles is briefly discussed.     

First-principles study of two-dimensional van der Waals heterostructure based on ZnO and Mg(OH)2: A potential photocatalyst for water splitting

In this study, the structural, electronic and optical properties of the two-dimensional heterostructure based on ZnO and Mg(OH)₂ are investigated by first-principle calculations. The ZnO/Mg(OH)₂ heterostructure, formed by van der Waals (vdW) interaction, possesses a type-II band structure, which can separate the photogenerated electron–holes constantly. The heterostructure has decent band edge positions for the redox reaction to decompose the water at pH 0 and 7. As for the interfacial properties of the heterostructure, the trend of band bending of the ZnO and Mg(OH)₂ layers in the heterostructure is addressed, which will result a built-in electric field. Besides, the charge-density difference and potential drop across the interface of the ZnO/Mg(OH)₂ vdW heterostructure are also calculated. Finally, the heterostructure is demonstrated that it not only has excellent ability to capture the light near the visible spectrum region, but also can improve the optical performance for the monolayered ZnO and Mg(OH)₂.     

Syntheses and characterization of Sr(OH)2 and SrCO3 nanostructures by ultrasonic method

The Sr(OH)₂ and SrCO₃ nanostructures were synthesized by reaction of strontium(II) acetate and sodium hydroxide or tetramethylammonium hydroxide (TMAH) via ultrasonic method. Reaction conditions, such as the concentration of the Sr²⁺ ion, aging time, power of the ultrasonic device and alkali salts show important roles in the size, morphology and growth process of the final products. The pure crystalline SrCO₃ were obtained by heating of product at 400 °C. The Sr(OH)₂ and SrCO₃ nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermal gravimetric (TG), differential thermal analyses (DTA) and the infrared spectroscopy (IR).     

Flower-like Ni3(NO3)2(OH)4@Zr-metal organic framework (UiO-66) composites as electrode materials for high performance pseudocapacitors

Zr-metal organic frameworks (Zr-MOFs, UIO-66) as a kind of crystalline porous material possess controllable porous structure and strong thermal stability up to 753 K. In this paper, we synthesized Ni₃(NO₃)₂(OH)₄, Zr-MOF with high specific surface area (1073 m² g⁻¹) and Ni₃(NO₃)₂(OH)₄@Zr-MOF composite for pseudocapacitor material. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were taken to characterize the structure and morphology of Ni₃(NO₃)₂(OH)₄, Zr-MOF, and Ni₃(NO₃)₂(OH)₄@Zr-MOF. The porous structure of Zr-MOF favors the utilization of the active material Ni₃(NO₃)₂(OH)₄ and interfacial charge transport and provides short diffusion paths for ions, which results in a high specific capacitance. Electrochemical properties are evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge measurement. A maximum specific capacitance (SC) of 992 F/g was obtained from CV at a scan rate of 5 mVs⁻¹, which is higher than Zr-MOF (∼134 F g⁻¹) and Ni₃(NO₃)₂(OH)₄ (∼753 F g⁻¹). Meanwhile, the Ni₃(NO₃)₂(OH)₄@Zr-MOF composite electrode exhibits a good cycling stability over 3000 cycles.

     

Preparation of Al(OH)3/Acrylic Copolymer Latex by Emulsion Polymerization

The Al(OH)₃/acrylic copolymer latexes were synthesized through the emulsion polymerization of acrylic monomers, butyl acrylate and 2-ethylhexyl acrylate in the presence of surface-functionalized Al(OH)₃ filler particles. The polymerization was stabilized by polyoxyethylene (50) nonyl phenyl ether (NP-1050, nonionic surfactant) and ammonium (POE) alkyl aryl ether sulfate (EU-S133D, anionic surfactant) to produce stable composite latexes. The improved compatibility of Al(OH)₃ surface with acrylic monomers was achieved by the modification with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS). Transmission electron microscopy showed that nano-sized Al(OH)₃ particles were slightly agglomerated in the copolymer latex. When pristine Al(OH)₃ was used as a filler or γ-MPS-modified Al(OH)₃ particles were added above 30 wt% with respect to monomers, unstable latexes were obtained, which were partially precipitated out on standing for prolonged time. The flame retardation effect was not apparent with the incorporation of Al(OH)₃ in the latexes by 30 wt% as shown by LOI test.     

A new chemical bath deposition method for fabricating ZnS,Zn(OH)<Subscript>2</Subscript>, and ZnO thin films,and the optical and structural characterization of these materials

ZnS thin films were deposited on glass and polymer substrates using a reaction between thiourea and a stable zinc complex, Zn(en)₃SO₄ (en: ethylenediamine) or Zn(trien)(ClO₄)₂ (trien: triethylenetetraamine), in alkaline media. In a weak alkaline solution, Zn(OH)₂ films were formed. The deposition reactions were controlled by the supply of sulfide ions from thiourea at a suitable rate in alkaline media and by the dissociation of free-metal ions from the metal complex used, the stability of which defined the free Zn²⁺ concentration throughout the reaction. The ZnS films showed emission peaks at ca. 450 and 485 nm, and the transmittance decreased with decreasing wavelength of the incident light in the visible region of the spectrum. ZnO thin films were deposited by decomposition of Zn(en)₃SO₄ in the presence of Cu(en)₂(ClO₄)₂ and thiourea; the copper(II) complex catalyzes this reaction. The ZnO films exhibited an emission peak at ca. 420 nm, and the absorbance was constant in the visible region of the spectrum. The scanning electron microscope images showed the formation of a fairly uniform surface with fine crystalline particles. PACS 81.15.-z; 68.55.-a; 81.05.Dz     

Synthesis of ZnO-SnO2 composite oxides by CTAB-assisted co-precipitation and photocatalytic properties

ZnO-SnO₂ composite oxides with various molar ratios of Sn:Zn have been synthesized at different calcination temperatures via a facile cetyltrimethylammonium bromide (CTAB)-assisted co-precipitation method with Zn(NO₃)₂·6H₂O and SnCl₄·5H₂O as starting materials. XRD, TEM, SEM and BET were employed to characterize the as-prepared samples. It has been found that amorphous intermediates appear between the evolutions of ZnO and SnO₂ crystals. The photocatalytic properties of the composite oxides were investigated using photocatalytic degradation of methyl orange as the probe reaction. The results show that the ZnO-SnO₂ composite oxide with a cube morphology exhibits the best photocatalytic activity, which was prepared with a molar ratio of Zn:Sn of 2:1 and calcination temperature of 700 °C.     

Investigation of Mg(OH)2 nanoparticles as an antibacterial agent

Our experimental results of using Mg(OH)₂ nanoparticles as an antibacterial agent are reported in this study. The antibacterial behavior of Mg(OH)₂ nanoparticles in liquid culture and in paper sheets was investigated. The colony forming units (CFU) counting and the headspace gas chromatography (HS-GC) measurement were used to determine the cell viability. Results indicate that Mg(OH)₂ nanoparticles are effective antibacterial agent against Escherichia coli (E. coli) and Burkholderia phytofirmans, and the OH^? and Mg²⁺ ions in Mg(OH)₂ water suspension were found not to be the reason for killing the bacteria. Mg(OH)₂ nanoparticles could be added directly to wood pulp to make paper sheets, whose antibacterial efficiency increased with the increase of the nanoparticle amount. The possible mechanism of antibacterial effect of Mg(OH)₂ nanoparticles is discussed.     

Dielectric and magnetic properties of(Zn,Co) co-doped SnO_2 nanoparticles

Polycrystalline samples of(Zn, Co) co-doped SnO2 nanoparticles were prepared using a co-precipitation method. The influence of(Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the(Zn, Co) co-doped SnO2 powder samples have the same tetragonal structure of SnO2. A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO2 samples exhibits room temperature ferromagnetism. Our results illustrate that(Zn, Co) co-doped SnO2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these(Zn, Co) co-doped SnO2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics.     

Facile synthesis and capacitive performance of the Co(OH)2 nanostructure via a ball-milling method

Co(OH)₂ nanoparticles were synthesized using only CoSO₄·7H₂O and NaOH as reactants without other auxiliary reagents via a simple, low-cost and practical ball-milling technique and investigated as the active electrode materials for supercapacitors. The structure and morphology of the resulting Co(OH)₂ samples were examined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The observations revealed the formation of brucite-like phase of β-Co(OH)₂, which had an irregular sphere-like shape with an average size of 50-100 nm. When investigated as electrode materials for supercapacitors, the β-Co(OH)₂ exhibited good energy-storage performances in terms of high specific capacitance of 599 F g⁻¹ and excellent capacity retention, suggesting its potential application in the electrode material for supercapacitors.     

Growth and characterization of Mg(OH)2 film on magnesium alloy AZ31

Magnesium-based biomaterials have been proposed as potential candidates for biodegradable implant materials, such as bone screws, bone plates, intraluminal stents and so on. However, the poor corrosion resistance inhibits their applications in surgery. They collapse before the injured tissues are healed. In this paper, Mg(OH)₂ nonstructural film was synthesized on the substrate of AZ31 magnesium alloy by hydrothermal method with NaOH solution as mineralizer to reduce the corrosion rate of magnesium-based materials. The obtained films were characterized by XRD, SEM, and XPS. The results showed that a Mg(OH)₂ film with nanostructure surface can be synthesized by hydrothermal method. It was observed that the thickness of film increased with the holding time. Corrosion rates of the films were studied by immersing the samples in Hank's solution (37 °C). Surface deposits of samples with films soaked in Hank's solution for 31 days were investigated by XRD, SEM, EDS, XPS, and FTIR. It verified that the corrosion rate of the magnesium alloy with grown film was slowed down in the Hank's solution and the behavior of corrosion was inhibited effectively. Amorphous calcium apatite precursor was observed to deposit on the surface of the film during corrosion experiments in Hank's solution. And the tape test revealed a strong adhesion between the film and the substrate.