As-obtained CdS Research Articles

A carbon dot-based clay nanocomposite for efficient heavy metal removal.

Carbon dots and their derivatives with fascinating photoluminescence properties have recently attracted tremendous scientific attention. This work describes the preparation of novel fluorescent bentonite clay (B), modified with carbon dot nanomaterials (CDs), and its usage as a lead removal platform. The CDs were prepared using a hydrothermal method from graphitic waste which served as the carbon source material. The as-obtained CDs were found to be fluorescent, being spherical in shape, positively charged, and smaller than 5 nm. Encouraged by their structure and photoluminescence features, they were used as surface modifiers to make fluorescent bentonite nanocomposites. Bentonite was used as a negatively charged model of aluminosilicate and reacted with the positively charged CDs. XRD, FTIR, XPS, and fluorescence analysis were used to characterize the prepared materials. The results indicate that the CDs intercalated inside the bentonite matrix were stable with excellent optical properties over time. They were finally used as an efficient hybrid platform for lead removal with a removal efficiency of 95% under light conditions, at room temperature, in an alkaline medium, and after only 10 min of reaction, compared to 70% under dark conditions. The pseudo-second-order kinetics and Langmuir isotherm models were better fitted to describe the adsorption process. The maximum adsorption capacity was equal to 400 mg g-1 toward Pb(ii) removal, at room temperature and pH = 8, under light conditions. To summarize, we have designed UV light stimuli responsive carbon dot-intercalated clay with high Pb(ii) adsorption capacity and long-term stability.

Multidimensional CdS nanowire/CdIn2S4 nanosheet heterostructure for photocatalytic and photoelectrochemical applications

Nanomaterial shapes can have profound effects on material properties, and therefore offer an efficient way to improve the performances of designed materials and devices. The rational fabrication of multidimensional architectures such as one dimensional (1D)–two dimensional (2D) hybrid nanomaterials can integrate the merits of individual components and provide enhanced functionality. However, it is still very challenging to fabricate 1D/2D architectures because of the different growth mechanisms of the nanostructures. Here, we present a new solvent-mediated, surface reaction-driven growth route for synthesis of CdS nanowire (NW)/CdIn2S4 nanosheet (NS) 1D/2D architectures. The as-obtained CdS NW/CdIn2S4 NS structures exhibit much higher visible-light-responsive photocatalytic activities for water splitting than the individual components. The CdS NW/CdIn2S4 NS heterostructure was further fabricated into photoelectrodes, which achieved a considerable photocurrent density of 2.85 mA·cm−2 at 0 V vs. the reversible hydrogen electrode (RHE) without use of any co-catalysts. This represents one of the best results from a CdS-based photoelectrochemical (PEC) cell. Both the multidimensional nature and type II band alignment of the 1D/2D CdS/CdIn2S4 heterostructure contribute to the enhanced photocatalytic and photoelectrochemical activity. The present work not only provides a new strategy for designing multidimensional 1D/2D heterostructures, but also documents the development of highly efficient energy conversion catalysts.

An efficient solid-state synthesis of fluorescent surface carboxylated carbon dots derived from C60 as a label-free probe for iron ions in living cells

In order to achieve the simple, easily repeated, and large scale preparation of fluorescent CDs, a new solid-state synthesis (SSS) approach was developed by calcining the mixture of fullerenes (C60) and solid sodium hydroxide. The cage of fullerenes could be opened and the hydroxyl and carboxyl were successfully introduced in the presence of sodium hydroxide under high temperature. The as-prepared surface carboxylated CDs possess many good properties, such as high water solubility, good photostability, salt tolerance, and nontoxicity. Especially, the fluorescence of CDs could be highly quenched by Fe3+ because of the strong interaction of hydroxyl or carboxyl on the as-obtained CDs with Fe3+, which realized a sensitive detection of Fe3+ in the linear range of 0.02–0.6μmol/L. What is more, we further applied the obtained CDs into the intracellular imaging of Fe3+.

Phosphine-free, low-temperature synthesis of tetrapod-shaped CdS and its hybrid with Au nanoparticles.

Tetrapod-shaped CdS colloidal nanocrystals are synthesized using a facile, phosphine-free synthesis approach at low temperature. The arm length and diameter of CdS tetrapods can be easily tuned by using different source of sulphureous precursors, i.e., sulfur powder, thioacetamide, and sodium diethyldithiocarbamate. Moreover, the growth of Au nanoparticles onto CdS to form metal-semiconductor hybrid nanocrystals is also demonstrated. The tetrapod-shaped CdS nanocrystals exhibit strong arm-diameter-dependent absorption and photoluminescence characteristics. Importantly, the as-obtained CdS tetrapods exhibit promising photocatalytic activity for the water-splitting reaction in photoelectrochemical cells.

Fabrication of CdS/CdSe bilayer thin films by chemical bath deposition and electrodeposition, and their photoelectrochemical properties

In this work, various kinds of CdS and CdS/CdSe thin films were fabricated on ITO conductive glass by chemical bath deposition (CBD) and/or electrodeposition (ED) methods. These films were characterized by XRD, XRF, SEM and optical absorption. Their photoelectrochemical properties were also investigated. First, two kinds of CdS thin films were firstly deposited on ITO conductive glass by CBD or ED. It was found that the two kinds of CdS films showed different compositions and crystal structures. The CdS film prepared by CBD is S-rich and has a cubic zinc blende structure, while the CdS film prepared by ED is Cd-rich and has a hexagonal wurtzite structure. Furthermore, CdSe was deposited on the as-obtained CdS films by a galvanostatical ED method, resulting in CdS/CdSe bilayer thin films. The achieved CdS/CdSe bilayer thin films showed enhanced optical absorption than the CdS monolayer thin film. For the photoelectrochemical properties, the CdS/CdSe bilayer thin film also exhibited enhanced photocurrent density and photoconversion efficiency in comparison with the CdS monolayer thin film. In particular, the CdS/CdSe bilayer thin film in which the CdS layer was obtained by ED, showed a maximum photocurrent density of about 6mA/cm2 and maximum photoconversion efficiency of 3.41%.

Quantum Dots Coupled ZnO Nanowire-Array Panels and Their Photocatalytic Activities

Fabrication and characterization of a heterojunction structured by CdS quantum dots@ZnO nanowire-array panels were presented. Firstly, ZnO nanowire-array panels were prepared by using a chemical bath deposition approach where wurtzite ZnO nanowires with a diameter of about 100 nm and 3 microm in length grew perpendicularly to glass substrate. Secondly, CdS quantum dots were deposited onto the surface of the ZnO nanowire-arrays by using successive ion layer absorption and reaction method, and the CdS shell/ZnO core heterojunction were thus obtained. Field emission scanning electron microscopy and transmission electron microscope were employed to characterize the morphological properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. X-ray diffraction was adopted to characterize the crystalline properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. Methyl orange was taken as a model compound to confirm the photocatalytic activities of the CdS shell/ZnO core heterojunction. Results indicate that CdS with narrow band gap not only acts as a visible-light sensitizer but also is responsible for an effective charge separation.

Synthesis of ultrathin CdS nanosheets as efficient visible-light-driven water splitting photocatalysts for hydrogen evolution

Ultrathin CdS nanosheets with a thickness of ~4 nm have been synthesized through an ultrasonic-induced aqueous exfoliation method involving lamellar CdS-DETA hybrid nanosheets as starting materials and L-cysteine as a stabilizing agent. The as-obtained CdS ultrathin nanosheets exhibit efficient photocatalytic activity and good stability for hydrogen production.

Synthesis and enhanced photocatalytic activity of monodisperse flowerlike nanoarchitectures assembled from CdS nanoflakes with exposed {0 0 1} facets

Monodisperse flowerlike nanoarchitectures assembled from CdS nanoflakes with a diameter of about 0.85μm were synthesized by a hydrothermal reaction of CdCl2 with thiocarbamide, polyvinylpyrrolidone and H2O at 180°C for 6.0h. The constituent CdS nanoflakes have perfect hexagonal shape with the side lengths of 0.37–0.38μm and the thicknesses of 60–70nm. Sphere like particles assembled from CdS nanocrystals formed firstly evolved into flowerlike architectures assembled from nanoflakes via an oriented attachment process due to the selective adsorption of PVP on (001) surface of CdS with the wurtzite structure. The as-obtained CdS flowerlike nanoarchitectures with exposed {001} facets show higher intrinsic photocatalytic activity than CdS branched nanostructures and commercial powders for degradation of malachite green.

One-pot solvothermal route to self-assembly of cauliflower-shaped CdS microspheres

Nearly monodispersed cauliflower-shaped CdS microspheres were prepared through a simple one-step solvothermal route on a large scale by employing sodium dodecyl sulfate (SDS) as the surfactant. Images by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) indicate that cauliflower-shaped CdS microspheres with diameters in the range from 1.3 to 4.5 μm are assembled by nanoparticles with an average diameter of approximately 30 nm. The possible formation mechanism of the cauliflower-shaped CdS microspheres was also proposed. The photovoltaic activity of cauliflower-shaped CdS architectures has been investigated, indicating that the as-obtained CdS microspheres exhibited higher photovoltaic performance in comparison with CdS nanoparticles.

Optical properties and electrical bistability of CdS nanoparticles synthesized in dodecanethiol

We reported the synthesis of CdS semiconductor nanoparticles using a simple one-pot reaction by thermolysis of cadmium acetylacetonate in dodecanethiol. Optical measurements of the as-obtained CdS nanoparticles revealed that their optical properties were closely related to surface effects. Based upon the cocktail of poly(N-vinylcarbazole) (PVK) and CdS nanoparticles, a bistable device was fabricated by a simple solution processing technique. Such a device exhibited a remarkable electrical bistability, which was attributed to the electric field-assisted charge transfer between PVK and the CdS nanoparticles capped by dodecaethiol. The conduction mechanism changed from an injection-controlled current to a bulk-controlled one during switching from OFF-state to ON-state.

Visible-light-induced photoelectric gas sensing to formaldehyde based on CdS nanoparticles/ZnO heterostructures

A visible-light-induced gas sensing element based on the heterostructures of CdS nanoparticles (NPs)/ZnO microcrystals has been successfully developed. Commercial ZnO microcrystals were coated with CdS nanoparticles by a sonochemical method to form the heterostructures. Compared with native CdS NPs, the as-obtained CdS NPs/ZnO showed enhanced photocurrent intensity. And the heterostructures-based element exhibited an excellent performance of photoelectric gas sensing to formaldehyde induced by visible-light. Moreover, the photocurrent intensity and sensitivity to formaldehyde were controllable by tuning the amount of CdS NPs attached on the surface of ZnO microcrystals. A possible explanation on the sensing mechanism has been proposed. In addition, the gas sensing element possessed good reproducibility. Our results demonstrate that the heterostructures of CdS NPs/ZnO is an efficient and promising material for visible-light-induced photoelectric gas sensors working at room temperature.

Direct Synthesis of Water-Soluble Ultrathin CdS Nanorods and Reversible Tuning of the Solubility by Alkalinity

Highly water-soluble ultrathin and fluorescent CdS nanorods are directly synthesized with the assistance of PEI. PEI plays as the passivator to control and induce the growth of the CdS nanorods and also makes the as-obtained nanorods dispersible in water. The as-obtained CdS nanorods are quite thin thus showing the quantum effect in the fluorescence. By adjusting the alkalinity of the solution, CdS nanorods can be controlled to precipitate or redisperse in water, which is believed to stem from the variation of the charges of the capping PEI molecules. These results provide an efficient and convenient way to directly synthesize water-soluble and fluorescent nanocrystals, which has potential application in biological labeling and detection.

Synthesis of brush-like CdS nanorod arrays through a novel hydrothermal reaction of simultaneous solvent-oxidation-hydrolysis

Brush-like CdS arrays composed of well-arranged nanorods have been successfully synthesized for the first time through a novel chemical reaction under the low-temperature hydrothermal condition. The reaction can be described as the solvent-oxidation-hydrolysis reaction among Cd, H2O and thiourea. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL). TEM results showed that these nanorods were about 20 nm wide with lengths varying from 1.25 µm to 3.5 µm. XRD pattern indicated that as-obtained CdS was hexagonal phase with good crystallinity. PL spectrum showed the products had novel optical property from the bulk counterpart. The formation mechanism was also explored.

In situ micelle–template–interface reaction route to CdS nanotubes and nanowires

CdS nanotubes and nanowires have been successfully synthesized via an in situ micelle–template–interface reaction (ISMTIR) route by adjusting the concentration of the surfactant. The whole reaction system is made up of SDS rod-like micelles as the template, CS2 as the oil phase and sulfur source, NH3 as the attacking agent and coordination-agent, and CdCl2 in water. It was found that SDS rod-like micelles were excellent templates for the growth of nanotubes and nanowires of small size. Due to a micelle diameter of 10–20 nm, the CdS nanotubes formed have an outer diameter of 15 nm on average and a wall thickness of ca. 5 nm, within the exciton diameter of bulk CdS. In particular, the formation of CdS nanowires was thought to occur by a “rolling-broken-growth” (RBG) process, in which the micelles could not support the strain of the CdS produced rolling. Thus, the diameter of as-obtained CdS nanowires was ca. 5 nm, within the exciton diameter, too. The UV-vis absorption spectra show the as-obtained CdS nanotubes and nanowires are well quantum-confined. In the future, this method is expected to be used to prepare other metal sulfide nanotubes and nanowires.