One-step Aqueous Synthesis Research Articles

One-step aqueous synthesis of CdS nanoparticles as a novel fluorescence probe for the ultrasensitive detection of DNA

One-step aqueous synthesis of CdS nanoparticles as a novel fluorescence probe for sensitive and selective determination of DNA with synchronous fluorescence spectrometric method has been developed. Different from the traditional organometallic route, in which toxic precursors or solvents might be used, the wet chemical approach demonstrated in this paper is superior in terms of simplicity, using of nontoxic materials, mild synthetic condition and good reproducibility. When Δ λ =255 nm, maximum synchronous fluorescence is produced at 264 nm, the synchronous fluorescence intensity of the composite nanoparticles is significantly decreased in the presence of trace DNA at PH 0.91. Under optimal conditions, the linear ranges of the calibration curves are 0.08–30.0 μg mL −1 for ctDNA and 0.05–35.0 μg mL −1 for hsDNA, respectively. The detection limits are 1.5 ng mL −1 for ctDNA and 2.2 ng mL −1 for hsDNA, respectively. Furthermore, the method is successfully applied to the quantification of DNA in synthetic samples. The results show that this proposed method is stable, sensitive and practical for the determination of trace DNA.

One-Step Synthesis of Au@Pd Core−Shell Nanooctahedron

Octahedral Au@Pd core-shell nanoparticles have been prepared by a one-step aqueous synthesis method where both metal precursors are present simultaneously with the use of cetyltrimethylammonium chloride as both reductant and stabilizer.

Surface-defect-states photoluminescence in CdS nanocrystals prepared by one-step aqueous synthesis method

CdS nanocrystals were prepared by a simple one-step aqueous synthesis method using thioglycolic acid (TGA) as the capping molecule, and characterized by X-ray powder diffraction (XRD), UV–vis absorption spectra and photoluminescence (PL) emission spectroscopy. The effects of both TGA/Cd and Cd/S molar ratio on the surface-defect-state PL intensity of CdS nanocrystals have been investigated. It was found that all of the as-prepared CdS nanocrystals showed a strong broad emission in the range of 450–700 nm centered at 560 nm, which was attributed to the recombination of an electron trapped in a sulfur vacancy with a hole in the valance band of CdS. The surface-defect-states emission intensity of CdS nanocrystals significantly increased with the increase of Cd/S molar ratio, and showed a maximum when Cd/S molar ratio was 2.0. If Cd/S molar ratio continued to increase, namely more than 2.0, the surface-defect-states emission intensity would decrease. It was found that the surface-defect-states emission intensity increased with the increase the TGA/Cd molar ratio, and showed a maximum when the TGA/Cd molar ratio was equal to 1.8, and a further increase of the TGA/Cd molar ratio would lead to the decrease of the surface-defect-states emission intensity.

One-step aqueous synthesis of stoichiometric Fe–Cu nanoalloy

Fe 50 − x Cu 50 − x B 2 x alloy was obtained by an aqueous chemical reduction at pH = 7.0, using fast and slow NaBH 4 solution addition methods. According to X-ray diffraction patterns, TEM and HRTEM observations, smaller than 10 nm nanocrystals of fcc-FeCuB were formed when the fast method was employed. The room temperature Mössbauer spectrum of this FeCuB nanoalloy shows a quadrupole doublet with an isomer shift of 0.355(1) mm/s and a quadrupole splitting of 0.772(2) mm/s, and a broadened magnetic sextet with a quadrupole splitting of 0.020(3) mm/s and an isomer shift of 0.436(5) mm/s, exhibiting a distinctive high average magnetic field of 40.57(5) T. Grains with a size larger than 10 nm were obtained for a slow method nanoalloy, and its Mössbauer spectrum consisted only of a broadened sextuplet characteristic of an fcc-FeCuB alloy.

Strong enhancement of band-edge photoluminescence in CdS nanocrystals prepared by one-step aqueous synthesis method

CdS nanocrystals were prepared by a simple one-step aqueous synthesis method using thioglycolic acid (TGA) as the capping molecule. The effects of Cd precursor concentration and the TGA/Cd molar ratio on the photoluminescence properties of the CdS nanocrystals were investigated. It was found that both the remained free cadmium monomers and Cd-(SR) x complexes played an important role in the nanocrystal nucleation growth and surface reconstruction. CdS nanocrystals with desired surface state could be obtained at high Cd precursor concentration and low TGA/Cd molar ratio.

Non-heavy-metal ZnS quantum dots with bright blue photoluminescence by a one-stepaqueous synthesis

We have examined the aqueous synthesis of non-heavy-metal ZnS quantum dots(QDs) using 3-mercaptopropionic acid (MPA) as the capping molecule atvarious pH and MPA:Zn:S ratios. Transmission electron microscopy (TEM)and x-ray diffraction (XRD) indicated that the aqueous ZnS QDs were3–5 nm in size with a zinc blende structure. We showed that, at pH 12 with aMPA:Zn:S = 8:4:1 ratio, the ZnS QDs with optimal blue emission could be obtained in a one-step,room-temperature aqueous process that exhibited a quantum yield of 31%, higher than that ofthe commercial CdSe/ZnS core–shell QDs. The present ZnS QDs could pass through a50 kD filter. This indicated that they were smaller than 5 nm in size, consistent with thoseestimated from the UV–vis absorption edge and the TEM image. At a lower pH (e.g.pH = 8), the room-temperature synthesized ZnS QDs exhibited nophotoluminescence. Although further hydrothermal annealing at100 °C could improve the photoluminescence of the ZnS QDs, the resultant emission was not asbright as that obtained at pH 12 at room temperature. The blue emission of aqueous ZnSQDs was likely the result of trap-state emissions involving the defect states of the QDs.The present ZnS QDs were bright, small and contained non-heavy-metal elements, thusoffering the potential for in vivo bioimaging.