silicon and cadmium-sulfide

Topics: Cadmium Compounds; Crystallization; Electron Transport; Macromolecular Substances; Materials Testing; Molecular Conformation; Nanostructures; Nanotechnology; Particle Size; Silicon; Sulfides; Surface Properties

In this work we used a setup consisting of an optical tweezers combined with a nonlinear microspectroscopy system to perform scanning microscopy and obtain emission spectra using two photon excited (TPE) luminescence of captured single living cells labeled with core-shell fluorescent semiconductor quantum dots (QDs). The QDs were obtained via colloidal synthesis in aqueous medium with an adequate physiological resulting pH. Sodium polyphosphate was used as the stabilizing agent. The results obtained show the potential presented by this system as well as by these II-VI fluorescent semiconductor quantum dots to perform spectroscopy in living trapped cells in any neighborhood and dynamically observe the cell chemical reactions in real time.

Topics: Animals; Cadmium Compounds; Macrophages, Peritoneal; Mice; Mice, Inbred BALB C; Microscopy, Confocal; Microspectrophotometry; Optical Tweezers; Quantum Dots; Selenium Compounds; Silicon; Spectrometry, Fluorescence; Spectrum Analysis, Raman; Sulfides; Tellurium; Titanium; Zinc Compounds

High quality wurtzite CdS nanowires have been synthesized by thermal evaporation of CdS powder onto Si substrate in the presence of Au catalyst at 650 degrees C by using pure H2 as a carrier gas. The nanowires were 10 nm in diameter and a few tens of micrometers in length. XRD patterns demonstrated that as prepared CdS is a pure crystalline material. High-resolution transmission electron microscopy of the materials showed that all CdS nanowires grew along (0001). According to analysis of selective area electron diffraction patterns taken from the interface, we proposed that there is a kind of epitaxy relationship in the interface region between Au catalyst and CdS grown, i.e., (0001)CdS // (111)Au, and [1210]CdS // [011]Au.

Topics: Cadmium Compounds; Catalysis; Crystallization; Electrons; Metal Nanoparticles; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Models, Chemical; Nanoparticles; Nanotechnology; Nanowires; Phase Transition; Silicon; Spectrophotometry, Ultraviolet; Sulfides; Temperature; X-Ray Diffraction

Topics: Animals; Cadmium Compounds; Cytophotometry; Light; Mice; Microfluidic Analytical Techniques; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Microspheres; Nanostructures; Nanotechnology; NIH 3T3 Cells; Quantum Dots; Semiconductors; Silicon; Silicon Compounds; Spectrum Analysis; Sulfides

Nanocrystalline cadmium sulphide thin films were prepared by the chemical bath (CB) deposition using a mixed aqueous solution of cadmium chloride, thiourea, and ammonium chloride. The XRD patterns showed that the CdS films were of hexagonal phase with preferred (002) orientation. From ellipsometric measurements, the film thickness was found to be in order of 66 nm and the optical band gap was estimated to be 2.4 eV.

Topics: Ammonium Chloride; Cadmium Chloride; Cadmium Compounds; Crystallization; Crystallography; Electrochemistry; Macromolecular Substances; Materials Testing; Models, Chemical; Models, Statistical; Nanotechnology; Silicon; Spectrophotometry; Sulfides; Surface Properties; Thiourea; X-Ray Diffraction

Topics: Cadmium Compounds; Catalysis; Gold; Hot Temperature; Light; Microscopy, Electron, Scanning; Nanoparticles; Nanotechnology; Powders; Semiconductors; Silicon; Spectrometry, Fluorescence; Sulfides; Temperature; X-Ray Diffraction

GeS2-CdSe superlattices and composite films are prepared by consecutive thermal evaporation of CdSe and GeS2 in vacuum. CdSe layer thickness varies between 1 and 10 nm, while the thickness of GeS2 layers is either equal (in superlattices) to or 20 times greater (in composite films) than that of CdSe layers. Standard spectral photocurrent measurements and various constant photocurrent methods are used to study optical absorption of all samples. An overall blueshift is observed with decreasing CdSe layer thickness of superlattices. This shift is related to a size-induced increase of the optical band gap of CdSe due to one-dimensional carrier confinement in the continuous nanocrystalline CdSe layers. A number of features are observed in the absorption spectra of composite films containing CdSe nanocrystals with average radii of approximately 2.5 and approximately 3.3 nm. They are discussed in terms of three-dimensional carrier confinement and are considered a manifestation of excited electron states in CdSe nanocrystals embedded in GeS2 thin film matrix. In addition to these discrete features, the exponential dependence of the optical absorption (Urbach) edge indicates a distribution of "valence band" tail states associated with disorder. Transient photoconductivity measurements made on similarly prepared SiOx-CdSe superlattices exhibit a rapid fall in photocurrent by a power law decay over several orders of magnitude of time, which is consistent with multi-pletrapping transport via an extensive distribution of deep defects.

Topics: Cadmium Compounds; Crystallization; Electric Conductivity; Germanium; Light; Materials Testing; Nanotechnology; Photochemistry; Quality Control; Reproducibility of Results; Semiconductors; Sensitivity and Specificity; Silicon; Silicon Dioxide; Spectrophotometry; Sulfides