An in vitro assessment of the interaction of cadmium selenide quantum dots with DNA, iron, and blood platelets.

Cadmium selenide (CdSe) quantum dots have gained increased attention for their potential use in biomedical applications. This has raised interest in assessing their toxicity. In this study, water-soluble, cysteine-capped CdSe nanocrystals with an average size of 15 nm were prepared through a one-pot solution-based method. The CdSe nanoparticles were synthesized in batches in which the concentration of the capping agent was varied with the aim of stabilizing the quantum dot core. The effects of the CdSe quantum dots on DNA stability, aggregation of blood platelets, and reducing activity of iron were evaluated in vitro . DNA damage was observed at a concentration of 200 µg/mL of CdSe quantum dots. Furthermore, the CdSe nanocrystals exhibited high reducing power and chelating activity, suggesting that they may impair the function of haemoglobin by interacting with iron. In addition, the CdSe quantum dots promoted aggregation of blood platelets in a dose dependent manner.

Noninjection facile synthesis of Gram-scale highly luminescent CdSe multipod nanocrystals.

Nearly all reported approaches for synthesis of high quality CdSe nanocrystals (NCs) involved two steps of preparation of Cd or Se stock solution in advance and then mixing the two reactants via hot-injection in high temperature. In this manuscript, Gram-scale CdSe multipod NCs were facilely synthesized in a noninjection route with the use of CdO and Se powder directly as reactants in paraffin reaction medium containing small amount of oleic acid and trioctylphosphine. The influence of various experimental variables, including reaction temperature, nature and amount of surfactants, Cd-to-Se ratio, and the nature of reactants, on the morphology of the obtained CdSe NCs have been systematically investigated. After deposition of ZnS shell around the CdSe multipod NCs, the PL QY of the obtained CdSe/ZnS can be up to 85%. The reported noninjection preparation approach can satisfy the requirement of industrial production bearing the advantage of low-cost, reproducible, and scalable. Furthermore, this facile noninjection strategy provides a versatile route to large-scale preparation of other semiconductor NCs with multipod or other morphologies.

Synthesis of high quality and stability CdS quantum dots with overlapped nucleation-growth process in large scale.

A low-cost, green, and reproducibly non-injection one-pot synthesis of high-quality CdS quantum dots (QDs) is reported. The synthesis was performed in the open air by mixing precursors cadmium stearate and S powder into a new solvent N-oleoylmorpholine. An overlapped nucleation-growth stage followed by a dominated growth stage was observed. The resulting QDs exhibited well-resolved absorption fine substructure and a dominant band-edge emission with a narrow size distribution (the full width at half maximum (fwhm) was only 22-24nm). The maximum photoluminescence (PL) quantum yield (QY) was as high as 46.5%. Highly monodispersed CdS QDs with tunable sizes and similar PL fwhm and QYs could also be obtained from the CdS QDs in a large-scale synthesis. The high-resolution transmission electron microscopy (HRTEM) images and powder X-ray diffraction (XRD) pattern suggested that the as-prepared QDs with high crystallinity had a cubic structure. A significant PL improvement and a continuous QY increase for the CdS QDs were observed during a long storage time in air and in a glovebox under room temperature. A slow surface reconstruction was proposed to be the cause for the PL enhancement of CdS QDs.

Nanostructured ZnS and CdS films synthesized using layered double hydroxide films as precursor and template.

Anion exchange reactions in layered double hydroxide films (M(OH)(2-x)(NO(3))(x).mH(2)O) followed by solid state conversion reactions are shown to yield micrometer-sized unsupported metal sulfide (M = Zn, Cd) films with unique textured morphologies. The characteristic three-dimensional nanostructured film morphology and crystallinity of the initial films are retained in the metal sulfide films although these conversion reactions involve anion exchanges concomitant with significant rearrangements of the crystal structures. Surface areas of 42 m(2)/g for zinc sulfide and 50 m(2)/g for cadmium sulfide thin films are observed. These values correspond to an increase in surface area of 75% for the Zn(5)(OH)(8)(NO(3))(2).2H(2)O to zinc sulfide conversion, while the cadmium sulfide films exhibit more than three times the surface area of their precursor material, Cd(OH)(NO(3)).H(2)O. The three-dimensional morphology of the resulting films is thus observed to combine the physical properties of the bulk materials with the advantages of higher surface areas typically associated with nanostructured or porous materials. The layered double hydroxide materials used in this study to provide both structural and chemical templates were prepared using the mild conditions of a biologically inspired vapor-diffusion catalytic synthesis.

Synthesis and application of DNA-CdS nanowires within a minute using microwave irradiation.

A very fast, electroless, microwave method is described to synthesize electrically conductive CdS nanowires on DNA just within 60 s. The electrical characterization indicates that the CdS wires are continuous, have very low contact resistance, and exhibit Ohmic behavior. Highly selective deposition on DNA is obtained by specific complexation between the Cd(II) ion and DNA, followed by decomposition of thioacetamide to S(2-) to form CdS. The nanowires are found to have a diameter of 140-170 nm and a length of approximately 8-12 microm. The one-step process developed here does not perturb the overall conformation of the DNA chain. The nanowires we fabricated can be used as building blocks for functional nanodevices, tiny computers, sensors, and optoelectronics.

CdS nanoparticles grown in a polymer matrix by chemical bath deposition.

Nanocrystallites of CdS have been grown by chemical bath deposition within the pores of poly(vinyl alcohol) (PVA) on glass and Si substrates. The CdS-PVA composite films are transparent in the visible region. XRD and TEM diffraction patterns confirmed the nanocrystalline CdS phase formation. TEM study of the film revealed the manifestation of nano CdS phase formation and the average particles size was varied in the range 5-12 nm. UV-vis spectrophotometric measurement showed high transparency (nearly 80% in the wavelength range 550-900 nm) of the films with a direct allowed band gap lying in the range 2.64-3.25 eV. Particle sizes have also been calculated from the shift of band gap with respect to that of bulk value and were found to be in the range 3.3-6.44 nm. The high dielectric constant (lies in the range 120-250 at high frequency) of PVA/CdS nanocomposite compared to that of pure PVA (-28) has been observed. The dielectric constant decreases with increase of dispersibility of the CdS nanoparticles within PVA. The nanocrystalline PVA/CdS thin films have also showed field emission properties with a turn-on field of approximately 6.6 V/microm, whereas only PVA thin film and bulk CdS on PVA have shown no field emission.