SEARCH · Search PubMed

Results for “Cadmium Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources

PubMed2006

Self-assembled stripe patterns of CdS nanorods.

Sterically stabilized CdS nanorods, 3-5 nm in diameter with aspect ratios ranging from 4 to 15, were observed to self-align into networks of stripes several micrometers long when drop-cast from dispersions at submonolayer coverage. The stripes are two to three nanorods thick with nanorods assembled side-by-side with their long axes parallel to the stripe direction. Energetic forces between nanorods, such as van der Waals and dipole-dipole attractions, favor parallel nanorod alignment; however, we propose that pattern formation is kinetically limited, or mediated, by solvent evaporation.

Anisotropy↗

PubMed2006

Ultrafast electronic relaxation and charge-carrier localization in CdS/CdSe/CdS quantum-dot quantum-well heterostructures.

The relaxation and localization times of excited electrons in CdS/CdSe/CdS colloidal quantum wells were measured using subpicosecond spectroscopy. HRTEM analysis and steady-state PL demonstrate a narrow size distribution of 5-6 nm epitaxial crystallites. By monitoring the rise time of the stimulated emission as a function of pump intensity, the relaxation times of the electron from the CdS core into the CdSe well are determined and assigned. Two-component rise times in the stimulated emission are attributed to intraband relaxation of carriers generated directly within the CdSe well (fast component) and charge transfer of core-localized carriers across the CdS/CdSe interface (slow component). This is the first reported observation of simultaneous photon absorption in the core and well of a quantum-dot heterostructure. With increasing pump intensity, the charge-transfer channel between the CdS core CdSe well contributes less to the stimulated emission signal because of filling and saturation of the CdSe well state, making the interfacial charge-transfer component less efficient. The interfacial charge-transfer time of the excited electron was determined from the slow component of the stimulated emission build-up time and is found to have a value of 1.2 ps.

Cadmium Compounds↗

PubMed2006

Photoinduced charge transfer and efficient solar energy conversion in a blend of a red polyfluorene copolymer with CdSe nanoparticles.

We present measurements of charge transfer and the photovoltaic effect in a blend of the alternating polyfluorene copolymer poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)) with branched CdSe nanoparticles. Quasi-steady-state photoinduced absorption measurements identified a long-lived charged species that formed after photoexcitation at room temperature. Photovoltaic devices based on this blend system showed a spectral response extending to 650 nm and gave a solar power conversion efficiency of 2.4% under Air Mass 1.5 Global (AM1.5G) conditions.

Cadmium Compounds↗

PubMed2006

Zero-phonon linewidth in CdSe/ZnS core/shell nanorods.

High-resolution spectral hole-burning studies of CdSe/ZnS core/shell nanorods reveal a sharp zero-phonon line, with a line width dependent on the measurement time scale. The zero-phonon line width is attributed to contributions from radiative decay, spectral diffusion induced by surface electric field fluctuations, and phonon-assisted migration of excitons localized in the nanorods. A decoherence rate as small as 4.5 GHz has been observed, when the effects of spectral diffusion are suppressed in the spectral hole-burning measurement. Comparison between zero-phonon line widths in nanorods and spherical nanocrystals also elucidates important differences in the decoherence process between the one- and zero-dimensional nanostructures.

Cadmium Compounds↗

PubMed2006

"Self-corralling" nanorods under an applied electric field.

Producing densely packed arrays of nanoscopic anisotropic objects, while necessary for applications in photovoltaic and field emission devices, presents considerable challenges. Here, we present findings on the phase separation of ligand-functionalized nanorods in a polymer matrix under an applied electric field. Densely packed hexagonal arrays of nanorods are produced by this method, where the rods are oriented in the direction of the applied field. Minimization of interfacial energy between the array of nanorods and the surrounding polymer serves to corral the nanorods into the densely packed arrays observed. These findings carry implications toward advancing organic-inorganic heterojunction photovoltaic devices that are expected to benefit from the oriented, densely packed ordered arrays of nanorods produced here.

Cadmium Compounds↗

PubMed2006

Nanocrystal shape and the mechanism of exciton spin relaxation.

The rate of exciton spin relaxation (flips) between the bright exciton states (F = +/-1) of CdSe nanocrystals is reported as a function of shape, for dots and nanorods. The spin relaxation is measured using an ultrafast transient grating method with a crossed linearly polarization sequence. It is found that the spin relaxation rate depends on the radius, not length, of the nanocrystals. That observation is explained by deriving an expression for the electronic coupling matrix element that mixes the bright exciton states.

Cadmium Compounds↗

PubMed2006

Electric-field-driven accumulation and alignment of CdSe and CdTe nanorods in nanoscale devices.

Local electric fields generated by nanopatterned electrodes were used to control the position and orientation of well-isolated as well as closely packed colloidal semiconducting CdTe and CdSe nanorods (NRs) drop-cast from solution. Postdeposition imaging using transmission-electron microscopy and atomic-force microscopy revealed strong NR alignment to the direction of the applied field and dense accumulation around and onto voltage-biased electrodes when deposited from dilute and concentrated solutions, respectively. The degree of alignment under the applied electric field is characterized by a nematic order parameter S approximately 0.8 in contrast to the zero-field case when S approximately 0.1.

Cadmium Compounds↗

PubMed2004

Stereoselective synthesis of natural N-(1-Deoxy-D-beta-fructos-1-yl)-L-amino acids and their effect on lead decorporation.

N-(1-Deoxy-D-fructos-1-yl)-l-amino acids isolated from hog liver are endogenous lead decorporation substances with low toxicity and cell membrane crossing ability. To simulate the effect of the natural N-(1-deoxy-D-fructos-1-yl)-l-amino acids on lead decorporation, a series of the epimerically pure N-(1-deoxy-D-fructos-1-yl)-l-amino acids (6a-e beta) were synthesized, and their usefulness as antagonists of lead intoxication was investigated. The results suggest that after treatment with 6a-e beta the liver, kidney, bone, and brain, lead levels of mice were significantly reduced in comparison with the control group. Except for bone and brain lead levels of the mice after chelating treatment with 6d beta, all of the other tissue lead levels of mice after chelating treatment with 6a-e beta are significantly lower than those of mice after treatment with dl-penicillamine (p < 0.05). All fecal lead levels of mice after treatment with 6a-e beta are significantly higher than those of mice after treatment with 0.9% saline (controls) and dl-penicillamine (p < 0.05-0.01). The effects of all chelating agents on urinary excretion of lead in mice are clearly superior to the control (p < 0.05-0.01). The results of the present studies on repeated lead exposure indicated that at tested levels of i.p. injections, the fructose-amino acids were effective antagonists of lead poisoning under the experimental conditions. After treatment with the chelators, the concentration of essential metals in mice did not exhibit change as compared to the control. The effects of the compounds on cadmium decorporation were also investigated, and similar results were observed.

Amino Acids↗

PubMed1999

Cloning sulfur assimilation genes of Brassica juncea L.: cadmium differentially affects the expression of a putative low-affinity sulfate transporter and isoforms of ATP sulfurylase and APS reductase.

The heavy-metal accumulator Brassica juncea L. is a high-biomass crop able to extract heavy-metal ions from the soil, a substantial part being translocated from root to shoot. Previous work has shown that Cd accumulation is accompanied by massive formation of phytochelatins (PCs). Rapid de novo synthesis of PCs in roots and leaves requires an increased synthesis of the tripeptide glutathione (GSH), which in turn depends on increased sulfur assimilation. Therefore. we have cloned cDNAs for three enzymes involved in sulfur assimilation, i.e. a putative low-affinity sulfate transporter (LAST) and two isoforms each for ATP sulfurylase (ATPS) and APS reductase (APSR). As degradation of glucosinolates might provide an additional sulfur source under stress, we also cloned a myrosinase (MYR). RNA blot analysis of transcript amounts indicated that upon Cd exposure (25 microM) the expression of ATPS and APSR in roots and leaves of 6-week-old Brassica juncea plants was strongly increased, whereas the expression of MYR was unaffected. LAST transcripts were significantly reduced in the root but remained unchanged in the leaves. Concomitant with Cd induction of ATPS and APSR mRNAs, cysteine concentrations in roots and leaves increased by 81% and 25%, respectively, whereas GSH concentrations decreased in roots and leaves by 39% and 48%, respectively. In agreement with our previous report on Cd induction of gamma-glutamylcysteine synthetase in B. juncea, the results indicate coordinate changes of expression for several sulfur assimilation enzymes in response to an increased demand for cysteine during PC synthesis.

Amino Acid Sequence↗

PubMed1997

Accumulation of ubiquitinated proteins in mouse neuronal cells induced by oxidative stress.

Ubiquitin protein conjugates are commonly detected in neuronal brain inclusions of patients with neurodegenerative disorders. The failure to eliminate the ubiquitin-protein deposits in the degenerating neurons may result from changes in the activity of the ubiquitin/ATP-dependent proteolytic pathway. This proteolytic pathway plays a major role in the degradation of short lived, abnormal and denatured proteins. Cadmium is a potent cell poison and is known to affect the ubiquitin pathway and to cause oxidative stress. Increases in protein mixed-disulfides (Pr-SSG) and decreases in glutathione (GSH) are often used as markers of oxidative stress. To investigate the relationship between the ubiquitin pathway and cellular glutathione (GSH), we treated HT4 cells (a mouse neuronal cell line) and rat mesencephalic primary cultures with different concentrations of the heavy metal. We observed marked increases in Pr-SSG as well as decreases in GSH, after exposure of HT4 cells or primary mesencephalic cultures to Cd2+. Furthermore, our results show that Cd2+ induced the accumulation of ubiquitinated proteins. Detection was by Western blotting of total cell extracts probed with antibodies that recognize ubiquitin-protein conjugates. These results suggest that the ubiquitin-pathway is closely involved in the cell response to cadmium-mediated oxidative stress.

Animals↗

PubMed1998

Modulation of adrenal cell functions by cadmium salts. 5. Cadmium acetate and sulfate effects on basal and ACTH-stimulated steroidogenesis.

In vitro and in vivo cadmium toxicity studies focus almost exclusively on CdCl2 effects. Only a few studies have used adrenocortical cells and tissue to determine cadmium salt effects during stress of adrenocorticotropin stimulation. Because several biologically relevant water-soluble cadmium salts exist, this study extended work with CdCl2 to evaluate the acute adrenocortical cell steroid secretory responses to non-lethal cadmium acetate (CdAc2) and CdSO4 concentrations. Control or ACTH-stimulated cultured Y-1 mouse adrenal tumor cells (ATCC) which secrete 20alpha-dihydroprogesterone (20-DHP) were incubated for 0.5 h in serum-free medium (FMEM) with or without 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0 and 1000.0 microg CdAc2 or CdSO4/ml FMEM (1.9, 3.8, 19.0, 38.0, 190.0, 380.0 and 1900.0 micromol/L, respectively). For each salt, cell viability was measured at the end of the incubation using live cell trypan blue exclusion. In addition, cumulative CdAc2 effects during 4 h incubations and effect reversibility were determined for control and stimulated cells. After each experimental incubation, the 20-DHP secreted into the medium was determined by radioimmunoassay. Over 80% of all control or ACTH-stimulated cells were viable after incubation in the presence or absence of various CdAc2 or CdSO4 concentrations. Cadmium acetate and sulfate inhibited basal and ACTH-stimulated steroid secretion in a dose-dependent manner. For basal steroid secretion the CdAc2 concentration that first significantly inhibited was 0.5 microg/ml medium (1.9 micromol/L); stimulated secretion was significantly inhibited beginning at 5.0 microg/ml (19.0 micromol/L) and the concentration reducing stimulated 20-DHP secretion by 50% (IC50) was 5.6 microg/ml (21.3 micromol/L). Similarly, the first CdSO4 concentration to significantly inhibit basal and ACTH-stimulated steroid secretion was 10.0 microg/ml medium (39.0 micromol/L); the IC50 was 7.8 microg/ml (29.8 micromol/L). Except that basally secreting Cd2+-treated cells almost doubled 20-DHP secretion after Cd2+ removal and subsequent incubation with ACTH, all basal and ACTH-stimulated steroid secretion was irreversibly inhibited by every CdAc2 concentration. All CdAc2 concentrations initiated and maintained cumulative inhibitory effects on basal and ACTH-stimulated steroid secretion over a 4 h period. Reversibility and cumulative CdSO4 treatment studies were not conducted. Based on the results from the present studies, both CdAc2 and CdSO4 appeared to incrementally inhibit control and ACTH-stimulated steroidogenesis without affecting cell viability and to be more potent inhibitors of adrenocortical cell steroid secretion than CdCl2. Finally, CdAc2 effects on control and stimulated cells were cumulative and irreversible.

20-alpha-Dihydroprogesterone↗

PubMed2004

Colloidal cdS fluorescence quenching by MV2+ under continuous irradiation.

This paper describes the photochemical behavior of the colloidal CdS/MV2+/COP system in excess of Na2S. We determined the rate constants for all the reactions which take place in solution under continuos irradiation and put into evidence the following intermediates: the monomer radical MVradical+ which dimerizes in (MVradical+)2 radical and the double reduced form MV0 of methylviologen. By this continuos irradiation technique we showed that the same reactions which take place on CdS particle surface with ultra fast rates can undergo also in bulk, but with a much slower rates.

Cadmium Compounds↗

PubMed2004

Optical detection of thymine dinucleoside monophosphate and its cis-syn photodimer by inorganic nanoparticles.

The Watson-Crick DNA double helix is an averaged ideal of multitudinous natural sequence-directed local structural deviations. By effectively derailing normal cellular physiological processes, damaged bases can induce noncanonical irregularities in the local structure of DNA if not efficiently repaired. Pyrimidine bases, especially thymine, are prone to dimerization when exposed to ultraviolet light. A [2 + 2] photocyclo-addition between adjacent thymine bases predominantly produces the cis-syn photodimer. These lesions, implicated in skin cancer, bend DNA by approximately 30 degrees due to their structural and conformational changes. Such changes in molecular properties can be detected by differential quenching of CdS nanoparticle luminescence and by surface-enhanced Raman scattering spectroscopy on metal nanoparticle substrates.

Cadmium Compounds↗

PubMed2001