CdS Nanotubes Research Articles

CdS Nanotubes and Y-Branched Nanochannels in AAM Fabricated by a Double Diffusion Route

Polycrystalline CdS nanotubes and a novel partition nanostructure were prepared in an anodic alumina membrane (AAM) template using a double diffusion method at room temperature. Transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX) investigations indicate that the nanotubes consisting of CdS grains have been synthesized in the AAM nanoholes. The influence of the reagent concentration on the morphology of the nanotubes has been systemically studied using a field emission scanning electron microscope (FE-SEM). It is confirmed that the Y-branched nanochannels can only formed under certain concentrations of the reactants ( and solutions). This novel Y-branched nanostructure may have potential applications for preparation of complicated nanostructure materials.

Sacrificial template method for the synthesis of CdS nanosponges and their photocatalytic properties

Using corresponding metal elemental nanowires as a self-sacrificed template, large-scale nanosponges consisted of curving CdS nanotubes have been successfully fabricated through a gas–solid sulfurization reaction. The products were characterized by X-ray powder diffraction, transmission electron microscopy, field-emission scanning electron microscopy and photoluminescence spectrum. The growth pathway can be described in terms of Kirkendall effect based on the experimental results. Furthermore, the CdS nanotubes exhibit high photocatalytic activity for degradation of the nonbiodegradable rhodamine B under visible irradiations probably due to the accessibility of both inner and outer surfaces through the pores in the walls.

Controlled Synthesis of Semiconducting Metal Sulfide Nanowires

We describe the preparation and characterization of (a) discrete, individual motifs and (b) arrays of crystalline and pure semiconducting transition metal sulfide (CuS, PbS, and CdS) nanowires, synthesized via an inexpensive, generalizable, simplistic, and ambient modified template-directed technique. We have demonstrated control over the diameters and lengths of our one-dimensional (1-D) nanostructures through corresponding variations in the template membrane’s pore size and thickness. We have not only successfully generated cubic-phase 1-D CdS nanowires but also produced, at slightly elevated temperatures, unusual CdS cactus-like, hierarchical nanostructures, consisting of tiny nanoneedles projecting out from the outer surfaces of parent CdS nanotube motifs. Opto-vibrational properties of all of these metal sulfide nanomaterials have been extensively studied. In addition, our results indicate that our as-prepared hexagonal-phase CdS cactus-like nanotubes evinced a higher photocatalytic degradation activ...

Field Emission Properties and Fabrication of CdS Nanotube Arrays.

A large area arrays (ca. 40 cm2) of CdS nanotube on silicon wafer are successfully fabricated by the method of layer-by-layer deposition cycle. The wall thicknesses of CdS nanotubes are tuned by controlling the times of layer-by-layer deposition cycle. The field emission (FE) properties of CdS nanotube arrays are investigated for the first time. The arrays of CdS nanotube with thin wall exhibit better FE properties, a lower turn-on field, and a higher field enhancement factor than that of the arrays of CdS nanotube with thick wall, for which the ratio of length to the wall thickness of the CdS nanotubes have played an important role. With increasing the wall thickness of CdS nanotube, the enhancement factorβdecreases and the values of turn-on field and threshold field increase.

Computation of structural and electronic properties of single-wall II–VI compound nanotubes

A theoretical investigation on the structural and electronic properties of single-wall II–VI compound CdS and ZnO nanotubes (NTs) of different length (2–6 ring long) and chirality has been carried out by performing semiempirical molecular orbital self-consistent field calculations at the level of parametric, PM3 (modified neglect of diatomic overlap, parametric method number 3) method. The calculation and results are presented for the NTs diameter, length, bond length, bond angle, surface area, volume, heat of formation, interfrontier molecular energy gap, dipole moment, electric charge distribution and electrostatic potential surface. Both CdS and ZnO make nanotubes of uniform diameter across the length in armchair model only. The interfrontier energy gap in case of CdS is found to be almost identical in both the configurations (zigzag and armchair), whereas in ZnO, it is more in the armchair model as compared to the zigzag model. We have also established some linear equations that can predict binding energy and heat of formation for longer nanotubes for a given number of rings. According to the results obtained, we conclude that all the II–VI compound NTs studied in present work show insulating properties.

Water-dissolvable and Reactive KCdCl3 Nanowires: Precursor and Template for Preparation of CdS and CdSe Nanotubes

Abstract CdS and CdSe polycrystalline nanotubes self-assembled from nanocrystals have been successfully prepared using water-dissolvable and reactive KCdCl3 nanowires as precursor and template at room temperature.

Photochemical growth of cadmium-rich CdS nanotubes at the air–water interface and their use in photocatalysis

Cadmium-rich CdS nanotubes were directly obtained at the air–water interface by a new photochemical route. Under ultraviolet light irradiation, branch-like lamellas were first formed on the surface of the precursor solution, and then they bent into nanotubes because of the composition difference between the two sides of lamellas during photochemical reactions and sulfur–air reactions. A typical nanotube has one spherical seal and one open end. Most of the cadmium was contained in the tubes and a little was doped in the tube-walls during their formation. Such nanotubes showed higher photocatalytic activity than the corresponding pure CdS nanotubes in the photodegradation of methylene blue because of the existence metal cadmium. This route is green, template/surfactant-free, reproducible and can be extended to prepare other binary compound semiconductor nanostructures containing elements that can react either with air or another gas.

Catalytic Electrogenerated Chemiluminescence and Nitrate Reduction at CdS Nanotubes Modified Glassy Carbon Electrode

Electrochemical and electrogenerated chemiluminescence (ECL) properties of a glassy carbon electrode modified with CdS nanotubes (CdS-GCE) are investigated in neutral media. The cyclic voltammogram (CV) shows two cathodic peaks (P(C1) and P(C2)) at -0.76 and -0.97 V and an anodic peak (P(A)) at -0.8 V, while two ECL peaks around -0.76 V are observed. Similar mechanisms of both ECLs are supposed and possibly related to the capture of an electron at a surface trap, that is, the surface sulfide vacancy (V(S)(2+)) of CdS nanotubes and its electrocatalytic reduction to H(2)O(2) generated from the dissolved oxygen. P(C2) and P(A) are ascribed to the two-electron redox at V(S)(2+). Moreover, electrocatalysis to nitrate reduction is also found at P(C2), with a good linear relationship between nitrate concentration and electrocatalytic peak current in CV.

Novel CdS Nanostructures: Synthesis and Field Emission

Here, we reported the success in the synthesis of novel CdS nanostructures, nanotubes, core-sheath nanowires, and tube−wire nanojunctions, by thermal evaporation of CdS powder and purposed a model for the growth mechanism. The core−sheath nanowires consist of a crystalline core and amorphous sheath. The photoluminescence characterization indicated that the CdS nanostructures were crystalline and showed a narrow peak at 516.5 nm. In addition, the CdS nanostructures exhibited better field emission properties with a field enhancement factor of 1.5 × 10 4 and turn-on field of 1.4 V/μm.

Synthesis of quantum-confined CdS nanotubes

CdS nanotubes with wall thickness comparable to excitonic diameter of the bulk material are synthesized by a chemical route. A change in experimental conditions result in formation of nanowires, and well-separated nanoparticles. The diameter and wall thickness of nanotubes measured to be 14.4 ± 6.1 and 4.7 ± 2.2 nm, respectively. A large number of CdS nanocrystallites having wurzite structure constitute these nanotubes. These nanotubes show high energy shifting of optical absorption and photoluminescence peak positions, compared to its bulk value, due to quantum confinement effect. It is proposed that nucleation and growth of bubbles and particles in the chemical reaction, and their kinetics and interactions are responsible for the formation of nanotubes.

Preparation and characterization of CdS nanotubes and nanowires by electrochemical synthesis in ion-track templates

CdS nanotubes and nanowires have been synthesized with controlled dimensions by means of template-electrodeposition method in etched ion-track membranes. The diameters of nanotubes and nanowires are between 20 and 110 nm, and the lengths are up to tens of micrometers. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern investigations demonstrate that CdS nanotubes and nanowires are polycrystalline in nature. The UV–vis absorption spectra of CdS nanotubes and nanowires embedded in polycarbonate (PC) membranes show that the absorption edges of PC films shift towards the shorter wavelength, with decreasing diameters of the deposited nanostructures. The results indicate that nanowires are formed from nanotubes by nanotube-stuffing-growth mechanism.

Directed Assembly of Hierarchical CdS Nanotube Arrays from CdS Nanoparticles: Enhanced Solid State Electro‐chemiluminescence in H2O2 Solution

Hierarchical CdS nanotube arrays (see figure) are assembled in an anodic aluminum oxide template from CdS nanoparticles by using a controlled solution precipitation method. The hierarchical nanotube arrays, with high porosity and uniform alignment, display considerably varied photoluminescence and enhanced solid state electro-chemiluminescence in H2O2 solution compared with those of random nanoparticle aggregates. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2007/c1386_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Photocatalytic formation of porous CdS/ZnO nanospheres and CdS nanotubes

It was found that ZnO nanocrystals have photocatalytic activity in the formation of CdS during the reduction of sulfur in the presence of cadmium acetate. It was shown that mesoporous spheres measuring 150–170 nm and consisting of CdS/ZnO particles measuring 5–8 nm are formed during the irradiation of ZnO particles measuring 5.5 nm. During the photodeposition of CdS by the action of light on nanorods produced by ultrasonic treatment of microcrystalline zinc oxide nanotubes of CdS 0.5–0.8 µm in length and 15–110 nm in internal diameter are formed. A mechanism, in which they appear at the ends of the ZnO nanorods and grow on the surface of the CdS/ZnO heterojunction, is proposed for the formation of the CdS nanotubes.

Electrogenerated chemiluminescence from CdS nanotubes and its sensing application in aqueous solution

Electrogenerated chemiluminescence (ECL) of CdS nanotubes in aqueous solution and its sensing application were studied by entrapping the CdS nanotubes in carbon paste electrode. Two ECL peaks were observed at −0.9 V (ECL-1) and −1.2 V (ECL-2), respectively, when the potential was cycled between 0 and −1.6 V. The electrochemically reduced nanocrystal species of CdS nanotubes could collide with the oxidized species in an annihilation process to produce the peak of ECL-1. The electron-transfer reaction between the reduced CdS nanocrystal species and oxidant coreactants such as S 2O 8 2−, H 2O 2, and reduced dissolved oxygen led to the appearance of the ECL-2 peak. Based on the enhancing effect of H 2O 2 on ECL-2 intensity, a novel CdS ECL sensor was developed for H 2O 2 detection. The sensor exhibited a detection limit of 0.1 μM and a linear range from 0.5 μM to 0.01 mM. The relative standard deviations of five replicate determinations of 5 μM H 2O 2 was 2.6%. In addition, the ECL spectrum in aqueous solution also exhibited two peaks at 500 and 640 nm, respectively.

Simultaneously inducing synthesis of semiconductor CdS nanotubes and nanospheres through living bio-membrane bi-template

Semiconductor CdS nanotubes with a small ratio of length to diameter and nanospheres were simultaneously synthesized in the light of biomineralization process through living bio-membrane bi-template of mungbean sprouts at room temperature. The outside diameter of the nanotube is 220–240 nm and the inner diameter is 200–220 nm, the length is up to 600–700 nm and the ratio of length to diameter is 2:1. The nanoshpheres are 25 nm in diameter and well distributed. The XRD pattern indicates that these nanocrystals were crystallized in the cubic structure with lattice a = 5.818 A. The optical properties of the products are illustrated, and their possible forming mechanism is explored.

Fabrication of CdS@TiO 2 coaxial composite nanocables arrays by liquid-phase deposition

A novel fabrication route for CdS@TiO 2 hybrid coaxial nanocables with the wall thickness controlled precisely is proposed using liquid-phase deposition (LPD) method with porous anodic aluminum oxide (AAO) as templates. Using LPD method, the thickness of the TiO 2 sheaths could be controlled precisely by adjusting the reaction conditions. Sequentially, the continuous and polycrystalline CdS nanotubes were deposited onto titanium oxide nanotubes by chemical bath deposition in order to form the coaxial CdS@TiO 2 nanocables. The core/sheath nanocables were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV–visible spectroscopic techniques.

Sacrificial template growth of CdS nanotubes from Cd(OH) 2 nanowires

A diffusion-controlled process was proposed for the preparation of inorganic nanotubes from nanowires. The preformed Cd(OH) 2 nanowires were used as the sacrificial templates to generate CdS nanotubes with different wall thickness. The axle–sleeve transition state found in-between the precursor and the formation of products proves the diffusion-controlled mechanism. CdS nanotubes can be prepared via this method at different temperature and with various sulfide sources. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results showed that all obtained CdS nanotubes consist conglomerated crystallites, and the crystallinity can be altered by changing the temperature of the growth process. The wall thickness of the produced CdS nanotubes can be controlled by changing the concentration of the sulfide source and stopping the reaction at different stages.

Single-crystalline nanotubes of IIB-VI semiconductors

Wurtzite-type CdS and CdSe nanotubes have been grown via a Sn nanowire-templated route under thermal annealing. The tubes are structurally uniform and defect-free single crystals, and partially or completely filled with Sn nanowires; most of the tubes display pin-like structures showing significant tapering along their axes. Cathodoluminescence spectra reveal that CdS and CdSe nanotubes have profound emission peaks at ∼512 and ∼724nm. The luminescence intensities vary between Sn filled and unfilled tube parts. Keeping in mind that ZnS and ZnSe nanotubes may also be synthesized using the similar technique, we propose that the present method is a universal synthetic route toward single-crystalline IIB-VI group semiconductor nanotubes.

Controlled synthesis of the semiconductor CdS quasi-nanospheres, nanoshuttles, nanowires and nanotubes by the reverse micelle systems with different surfactants

A series of CdS nanomaterials with different morphologies and structures were self-assembled in a simple reverse micelle solvent system containing cyclohexane, aqueous solution, n-pentanol and surfactant. CdS quasi-nanospheres (i.d. 200–500 nm), CdS nanoshuttles (i.d. 248 nm and length ∼450 nm), CdS nanowires (i.d. ∼46 nm and length 1.65–4.15 μm) and CdS nanotubes (inner i.d. 25 nm, outer i.d. 38 nm and length ∼400 nm long) were produced by employing the surfactant of Tween-80, Peregals, C 12E 9 and Triton X-100, respectively. The CdS nanomaterials were found to possess different optical properties from the bulk CdS when analyzed by photoluminescence and UV-visible spectroscopy. A mechanism involving the possible formation of nanomaterials based on surfactant microemulsion template was also proposed.

Double‐Template Synthesis of CdS Nanotubes with Strong Electrogenerated Chemiluminescence

Two templates are better than one! By combining the already known soft-template and sacrificial-template synthetic methodologies, hollow nanostructures of various shapes and materials can be designed without the need for complicated processes such as chemical etching or calcination. Here, CdS nanotubes are prepared from Cd(OH)Cl nanorods and thioacetamide, using biodegradable gelatin as the soft template (see HRTEM image).