Synthesis and characterization of cadmium hydroxide nano-nest by chemical route

A facile chemical route based on room temperature chemical bath deposition (CBD) was developed to deposit the Cd(OH)₂ nano-nest. The growth mechanism follows two-stage crystallization with initial growth of nucleation centers, followed by subsequent anisotropic growth. The nano-nest morphological evolution of Cd(OH)₂ on different substrates has been carried out. These films have been characterized by the techniques; such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), optical absorption, contact angle measurement and thermoelectric power (TEP) measurements. The X-ray diffraction study revealed that the as deposited film consists of cadmium hydroxide (Cd(OH)₂) phase. The nano-nest consisted of wires with nearly uniform in dimensions, with diameter around 30 nm and length of few microns. As-deposited Cd(OH)₂ film used in this study showed water contact angle of 66°. The optical bandgap was found to be 3.2 eV, with n-type electrical conductivity as confirmed from thermo-emf measurements.     

Synthesis of nano and micro crystals of Cd(OH)2 and CdO in the shape of hexagonal sheets and rods

Cd(OH)₂ and CdO nano/micro crystals were synthesized in ethanol-water medium using cadmium foil as a source under solvothermal condition. The experimental parameters such as ratio of ethanol to water, concentration of NaOH and synthesis temperature all play important role in determining the size, shape and crystalline phase of the products. The products were characterized by X-ray diffraction and scanning electron microscopy. Nano/micro crystals of CdO were also achieved by thermal treatment of Cd(OH)₂ crystals in air at different temperatures.     

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.     

Effect of an In-Situ Nucleating Agent on the Polymorphs and Mechanical Properties of Isotactic Polypropylene

The influence of glutaric acid (GA)/cadmium hydroxide [Cd(OH)₂] mixtures on the crystallization and properties of isotactic polypropylene (iPP) was investigated by means of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), polarized light microscopy, and mechanical tests. It was found that the β-crystalline form was produced in the samples containing 0.15 wt% GA and more than 0.17 wt% Cd(OH)₂. The content of β-crystalline form was maximum, i.e. K_DSC = 65.4% and K_WAXD = 71.4%, when the sample was doped with GA (0.15 wt%)/Cd(OH)₂ (0.20 wt%) (the molar ratio of GA:Cd(OH)₂ was 1:1.2). It was also found that GA/Cd(OH)₂ mixtures not only induced the β-crystalline form but also made spherulites smaller. The results of mechanical tests showed that the toughness of iPP was greatly improved by bicomponent nucleator, while the stiffness decreased a little. Fourier transform infrared spectroscopy analysis indicated that an “in-situ” chemical reaction occurred between GA and Cd(OH)₂ during melt blending, yielding an effective β nucleator (cadmium glutarate).     

Preparation, conversion, and comparison of the photocatalytic property of Cd(OH)2, CdO, CdS and CdSe

In this paper, we report the hydrothermal preparation of Cd(OH)₂ nanowires and further conversion to CdO nanobelts, CdS nanowires and CdSe nanoparticles through thermal treatment, solvothermal and mixed-solvothermal routes, respectively. The as-obtained products were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FEMSEM). Research showed that four cadmium compounds were good photocatalysts for the degradation of organic dyes such as Safranine T and Pyronine B, under irradiation of 365 nm UV light. The order of catalytic activity of different materials was found to be Cd(OH)₂<CdO<CdS<CdSe.     

Ultrasonic synthesis of two nanostructured cadmium(II) coordination supramolecular polymers: Solvent influence,luminescence and photocatalytic properties

Two nanoparticles of cadmium(II) coordination polymers (CPs) formulated as [Cd(L)(DCTP)]_n (1) and [Cd(L)₂(DCTP)·2H₂O]_n (2) (L = 1,2-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H₂DCTP = 2,5-dichloroterephthalic acid) were prepared by the sonochemical approach in different solvents and characterized by elemental analysis, IR spectra, scanning electron microscopy (SEM), and powder X-ray diffraction. Structural determination reveals that CP 1 displays a 2D four-connected sql net layer, Whilst CP 2 exhibits a 1D “V”-like chain structure. Luminescence properties, thermal behavior, and photocatalytic activities of the nanoparticles of CPs 1 and 2 on the degradation of methylene blue were investigated. The photocatalytic mechanism is carried out by introducing t-butyl alcohol (TBA) as a widely used OH scavenger. Furthermore, the influence of solvents, reaction time, and ultrasound irradiation temperature on the morphology and size of the nanostructure CPs 1 and 2 were investigated. The results indicated that an increase of time and ultrasound irradiation temperature decreased the nanostructured size.     

Formation of ZnO@Cd(OH)2 core-shell nanoparticles by sol-gel method: An approach to modify surface chemistry for stable and enhanced green emission

We report the formation of highly stable and luminescent ZnO@Cd(OH)₂ core-shell nanoparticles by simple introduction of cadmium salt in the initial precursor solution, used to synthesize ZnO nanoparticles by sol-gel route. The cadmium to zinc salt concentration ratio has been also varied to control the growth of ZnO nanoparticles at the smaller particle size. Formation of ZnO@Cd(OH)₂ core-shell nanostructure has been confirmed by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). UV-vis absorption spectroscopy exhibits blue-shift in absorption edge on increasing cadmium concentrations. The photoluminescence emission spectra showed the remarkably stable and enhanced visible (green) emission from suspended ZnO@Cd(OH)₂ nanoparticles in comparison to bare ZnO nanoparticles. It is postulated that Cd(OH)₂ layer at the surface of ZnO nanoparticles prevents the agglomeration of nanoparticles and efficiently assists the trapping of hole at the surface site, a first step necessary for visible emission. The Fourier transform infrared spectroscopy (FTIR) also supports our assumption about surface chemistry.     

Colloidal semiconductor quantum dots: Potential tools for new diagnostic methods

We present and discuss the application of colloidal semiconductor quantum dots for diagnostic purposes, with special emphasis for cancer. We prepared and applied core-shell cadmium sulfide-cadmium hydroxide (CdS/Cd(OH)₂) semiconductor quantum dots in aqueous medium. Tissue and cells labeling was evaluated by laser scanning confocal microscopy as well as by conventional fluorescence microscopy. The procedure presented in this work, shown to be a promising tool for fast, low-cost and precise cancer diagnostic protocols.     

Synthesis and characterization of cadmium hydroxide nanowires by arc discharge method in de-ionized water

In this study, Cd(OH)₂ nanowires have been synthesized by using arc discharge method in de-ionized water. The morphology and properties of the Cd(OH)₂ nanowires were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and UV–Vis spectroscopy. TEM observations revealed that Cd(OH)₂ nanowires were abundant morphology in synthesized nanostructures, and the diameter of the Cd(OH)₂ nanowires ranges from 5 to 40 nm with several micrometers of length. In addition, the width of nanowires is not uniform and varies throughout the nanowire. XRD analysis revealed that the Cd(OH)₂ nanowires grow along [001] direction. Furthermore, hexagonal- and irregular-shaped Cd(OH)₂ nanoplates were synthesized during arc discharge. It was obtained that required arc current is 50 A for the effective and large scale production of Cd(OH)₂ nanowires. Furthermore, the optical properties of the nanowires have been characterized by UV–Vis spectra. By the means of the optical studies, the direct band gap of Cd(OH)₂ nanowires was found to be 4.0 eV with strong quantum size effect. It is also shown that a simple and cheap method which does not require relatively expensive vacuum and laser equipment stipulates an economical alternative for the synthesis of Cd(OH)₂ nanowires.     

Room temperature synthesis and characterization of ultralong Cd(OH)2 nanowires: a simple and template-free chemical route

Ultralong Cd(OH)₂ nanowires were fabricated in high yield by a convenient chemical method using alkali medium at room temperature without using any templates. The preparation conditions induce a unilateral growth of nanowires, despite the absence of any template. The length of the nanowires reached several hundreds of micrometers, giving an aspect ratio of a few thousands. The X-ray diffraction shows that the Cd(OH)₂ nanostructures crystallized in the wurtzite structure without any special orientation. The photoluminescence spectrum of Cd(OH)₂ nanostructures appears as two emission bands: one related to green emission at 475–510 nm, and the other related to deep level emission at 510–540 nm. Also the formation mechanisms of the nanowires are presented. The growth mechanism involves the irreversible and specifically oriented self-assembly of primary nanocrystals and results in the formation of the nanowires.     

Formation of CdO films from chemically deposited Cd(OH)2 films as a precursor

Formation of cadmium hydroxide at room temperature onto glass substrates from an aqueous alkaline cadmium nitrate solution using a simple soft chemical method and its conversion to cadmium oxide (CdO) by thermal annealing treatment has been studied in this paper. The as-deposited film was given thermal annealing treatment in oxygen atmosphere at 450 °C for 2 h for conversion into cadmium oxide. The structural, surface morphological and optical studies were performed for as-deposited and the annealed films. The structural analyses revealed that as-deposited films consists of mixture of Cd(OH)₂ and CdO, while annealed films exhibited crystalline CdO. From surface morphological studies, conversion of clusters to grains after annealing was observed. The band gap energy was changed from 3.21 to 2.58 eV after annealing treatment. The determination of elementals on surface composition of the core-shell nanoparticles of annealed films was carried out using X-ray photoelectron spectroscopy (XPS).     

The isotopic dependence of the spin-rotation interaction: the rotational spectrum of cadmium hydride in its XΣ state

Far-infrared rotational transitions within the X²Σ⁺ (v=0) state of cadmium hydride (CdH) were recorded over the range N″=2-17 for 12 different isotopomers, using the technique of tunable far-infrared (TuFIR) spectroscopy. The molecule was made by heating cadmium metal in the presence of a DC electric discharge in hydrogen. Fine structure arising from the electron spin-rotation interaction and hyperfine structure from the ¹¹¹Cd, ¹¹³Cd, and ¹H nuclei were resolved and analyzed. All of the isotopic data were fitted together using a Hamiltonian containing mass-independent, Dunham-type rotational parameters U_kl and small correction terms Δ_kl described by Watson [J. Mol. Spectrosc. 80 (1980) 411]. The spin-rotation interaction was modeled in an analogous way using Dunham-like U_γ,kl parameters, and fitting its isotopic dependence properly required the use of four Δ_γ,kl correction terms.     

Synthesis and separation property of flower-like Cd(OH)2 microstructures via a simple solution route

Well-defined flower-like Cd(OH)₂ microstructures have been successfully synthesized via a simple aqueous solution route, using CdCl₂ and NaOH as the reactants, and triethanolamine (TEA) as the modifying agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis spectrometer were used to characterize the products. SEM and TEM images illustrated that the flower-like Cd(OH)₂ bundles consisted of hexagonal nanoplates with thickness of about 50 nm. The adsorption of TEA on (0 0 1) plane of the growing Cd(OH)₂ crystal leads to the flower petals in appearance. Further experiments evidenced that the positively charged Cd(OH)₂ could effectively adsorb or separate the negatively charged dye molecules.     

Kinetics of luminescence induced by sputtering metallic cadmium by a pulsed fast electron beam in helium

Results of an experimental study of the kinetics of luminescence observed when a metallic cadmium foil is bombarded in a helium medium by a 3-ns pulsed beam of 150-keV fast electrons are reported. The foil was irradiated at gas pressures from 76 to 2280 Torr. At a foil temperature of T = 240° C, the de-excitation time of the Beitler levels of the Cd II ion was measured as a function of the buffer gas pressure and the constant of collision quenching of the 5s22D_5/2 level of Cd II by He atoms was determined as k ≈ 3 × 10^-29 cm⁶/s. The experimental data were compared with calculations performed for the gas—vapor mixture in order to find the fraction of excited Cd II ions in the 5s²2D_5/2 state produced directly as a result of sputtering of metallic cadmium by high-energy electrons and by components of the helium plasma. At a helium buffer gas pressure of P ≤ 2.5 atm and a temperature of the cadmium target of T = 240° C, the value of this quantity was found to be α = 0.28 + 0.23P (where P is the helium pressure in atmospheres).     

Phase- and shape-controlled synthesis of cadmium hydroxyl chloride microstructures via an ammonia-assisted conversion of 1D CdQCl (Q=quinoline) complex microwires

In this paper we reported a NH₃·H₂O-assisted solvothermal route for successful synthesis of cadmium hydroxyl chlorides (Cd_x(OH)_yCl_z) microstructures with different phases and shapes, employing 1D CdQCl (Q=quinoline) complex microwires as the precursor. Experiments contained two processes: firstly, CdQCl complex microwires with 500–600 nm in diameter and several hundreds of micrometers in length were prepared by the complexation between CdCl₂·2.5H₂O and quinoline at room temperature; then, CdQCl microwires were solvothermally treated at 150 °C for 10 h in the presences of different amounts of NH₃·H₂O to produce Cd_x(OH)_yCl_z microstructures with various phases and shapes. The as-obtained precursor and Cd_x(OH)_yCl_z microstructures were characterized by scanning electron microscopy, transmission electron microscopy, Infrared spectrometry and X-ray powder diffraction. Experiments showed that hexagonal Cd(OH)Cl was obtained from water–methanol system, while rhombohedral Cd₄(OH)₅Cl₃ from methanol system. Also, it was found that the shapes of Cd_x(OH)_yCl_z could be tuned by the amounts of NH₃·H₂O. Furthermore, the UV diffuse reflection and photoluminescence spectra of the precursor and Cd_x(OH)_yCl_z were also investigated.     

Investigation of chemical bath deposition of CdO thin films using three different complexing agents

Chemical bath deposition of CdO thin films using three different complexing agents, namely ammonia, ethanolamine, and methylamine is investigated. CdSO₄ is used as Cd precursor, while H₂O₂ is used as an oxidation agent. As-grown films are mainly cubic CdO₂, with some Cd(OH)₂ as well as CdO phases being detected. Annealing at 400 °C in air for 1 h transforms films into cubic CdO. The calculated optical band gap of as-grown films is in the range of 3.37-4.64 eV. Annealed films have a band gap of about 2.53 eV. Rutherford backscattering spectroscopy of as-grown films reveals cadmium to oxygen ratio of 1.00:1.74 ± 0.01 while much better stoichiometry is obtained after annealing, in accordance with the X-ray diffraction results. A carrier density as high as 1.89 × 10²⁰ cm⁻³ and a resistivity as low as 1.04 × 10⁻² Ω-cm are obtained.     

Optical properties of cadmium sulfide nanocrystal film prepared by electrochemical synthesis at liquid-liquid interface

Dendritic nanocrystalline CdS film was deposited at liquid-liquid interface of surfactants and an electrolyte containing 4 mmol L⁻¹ cadmium chloride (CdCl₂) and 16 mmol L⁻¹ thioacetamide (CH₃CSNH₂) with an initial pH value of 5 at 15 °C by electrochemical synthesis. The nanofilm was characterized by transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), ultraviolet visible (UV-vis) absorption spectroscopy and fluorescence spectroscopy. The surface morphology and particle size of the nanofilm were investigated by AFM, SEM and TEM, and the crystalline size was 30-50 nm. The thickness of the nanofilm calculated by optical absorption spectrum was 80 nm. The microstructure and composition of the nanofilm was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), showing its polycrystalline structure consisting of CdS and Cd. Optical properties of the nanofilm were investigated systematically by UV-vis absorption and fluorescence spectroscopy. A λ_onset blue shift compared with bulk CdS was observed in the absorption spectra. Fluorescence spectra of the nanofilm indicated that the CdS nanofilm emitted blue and green light. The nanocomposites film electrode will bring about anodic photocurrent during illumination, showing that the transfer of cavities produces photocurrent.     

Structural aspects of undoped and doped nickel hydroxides

Nickel hydroxide is widely used as an active material in Ni-Cd and Ni-MeH batteries. The electrochemical properties such as charge acceptance, electronic conductivity etc. can be dramatically influenced by doping β-Ni(OH)₂ with small amounts of Co, Cd or Zn. Stabilizing of α-Ni(OH)₂ offers the possibility to obtain nickel electrodes with enhanced capacity. The stabilizing of α-Ni(OH)₂ is achieved by replacing at least 20% of the nickel by a trivalent metal ion. The structural features of the undoped and doped nickel hydroxides and the resulting electrochemical properties are discussd and reviewed. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Determination by Fluorescence Spectroscopy of Cadmium at the Subnanomolar Level: Application to Seawater

This paper reports the development of a molecular fluorescence spectroscopy-based approach for the determination of cadmium in seawater. Anthrylazamacrocycle derivatives—the fluorescence of which is enhanced when chelated to zinc or cadmium—are used as chemosensors. A detection limit of 5 nM has been found at pH 10 for both metals, and spectral shifts allow simultaneous Cd(II)/Zn(II) determination using multiwavelength analysis. While cadmium emission behavior is similar at pH 13, zinc is not detected anymore. This enables the selective detection of cadmium even at a high Zn(II)/Cd(II) ratio. The detection limit is 1 nM. Interferent removal and preconcentration have been developed using a Dowex resin, with a view to determine cadmium in seawater. A global procedure including interferent elimination, cadmium preconcentration (30 fold), and fluorescence detection at pH 13 has been evaluated on certified reference material SLEW-2.     

Structural, optical and electrical properties of Cd-doped SnO2 thin films grown by RF reactive magnetron co-sputtering

Transparent conducting SnO₂:Cd thin films were prepared by RF reactive magnetron co-sputtering on glass slides at a substrate temperature of 500 °C using CdO as cadmium source. The films were deposited under a mixed argon/oxygen atmosphere. The structural, optical and electrical properties were analyzed as a function of the Cd amount in the target. The X-ray diffraction shows that polycrystalline films were grown with both the tetragonal and orthorhombic phases of SnO₂. The obtained films have high transmittance and conductivity. The figure of merit of SnO₂:Cd films are in the order of 10⁻³ Ω⁻¹, which suggests that these films can be considered as candidates for transparent electrodes.