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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hybrid polymer films consist of quantum dots (QDs) dispersed in a polymer matrix. A key fundamental challenge that is hindering their optimisation in optoelectronic devices such as hybrid solar cells is overcoming uncontrolled aggregation of the QDs. In an effort to direct aggregation, and trigger self-assembly, we added a bilinker ligand (1,2-ethanedithiol) to dispersed PbS QDs in polymer solutions prior to film deposition by spin casting. Turbidity studies of the PbS QD/1,2-ethanedithiol dispersions enabled a relationship to be established between the extent of 1,2-ethanedithiol-triggered QD aggregation and the nominal fractional coverage of the QDs by 1,2-ethanedithiol. The extent of aggregation (and self-assembly) increased with nominal fraction coverage. Above a value of about 1.0 QD aggregation increased substantially. TEM images showed that at low 1,2-ethanedithiol concentrations triggered assembly of network-like QD structures occurred. At high 1,2-ethanedithiol concentrations the QDs self-assembled into more-ordered micrometre-sized crystals. The results suggest that 1,2-ethanedithiol decreases the inter-QD separation in dispersion as a result of rapid ligand exchange and this process results in QD aggregation as well as self-assembly. The assembled QD structures were successfully trapped within polymer films by spin casting of PbS QD/1,2-ethanedithiol dispersions containing added polystyrene or polytriarylamine.
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PMID:Triggered aggregation of PbS nanocrystal dispersions; towards directing the morphology of hybrid polymer films using a removable bilinker ligand. 2145 25

Nanocomposite thin films consisting of ligand-connected metal nanoparticles were deposited by iteration of ligand assembly, surface complex formation and reduction. This novel and convenient approach combines characteristics of the layer-by-layer (LbL) and the successive ion layer adsorption and reaction (SILAR) techniques. In contrast to classical LbL assembly, the nanoparticle formation is performed in situ, avoiding separate reduction, protection and attachment steps. To demonstrate the versatility of the approach, different metal precursors (Pd, Ag and Au salts) and linkers (1,2-ethanedithiol, 1,4-benzenedithiol and polythiol) were applied. The formation of dithiol-linked nanoparticle films was confirmed by TEM and XPS. By combining the deposition protocol with ion track etched polycarbonate templates, nanotubes and nanowires with high aspect ratios of up to 300 could be fabricated.
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PMID:Synthesis of nanoparticle/ligand composite thin films by sequential ligand self assembly and surface complex reduction. 2306 61

Remarkable magneto-optical properties of a new isolator material, that is, europium sulfide nanocrystals with gold (EuS-Au nanosystem), has been demonstrated for a future photo-information technology. Attachment of gold particles that exhibit surface plasmon resonance leads to amplification of the magneto-optical properties of the EuS nanocrystals. To construct the EuS-Au nanosystems, cubic EuS and spherical Au nanocrystals have been joined by a variety of organic linkers, that is, 1,2-ethanedithiol (EDT), 1,6-hexanedithiol (HDT), 1,10-decanedithiol (DDT), 1,4-bisethanethionaphthalene (NpEDT), or 1,4-bisdecanethionaphthalene (NpDDT) . Formation of these systems was observed by XRD, TEM, and absorption spectra measurements. The magneto-optical properties of the EuS-Au nanosystem have been characterized by using Faraday rotation spectroscopy. The Faraday rotation angle of the EuS-Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS-Au nanosystems was observed. The spin configuration in the excited state of the EuS-Au nanosystem was also investigated using photo-assisted electron paramagnetic resonance.
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PMID:Enhanced magneto-optical properties of semiconductor EuS nanocrystals assisted by surface plasmon resonance of gold nanoparticles. 2410 39

Due to the emerging issue of the contamination of sartan medicines and drinking water with N-nitrosodimethylamine (NDMA) and/or N-nitrosodiethylamine (NDEA), the detection of NDMA/NDEA has become an important theme. In this study, we utilized the focused ion beam (FIB) technique to fabricate gold nanorods (Au NRs) and Surface-enhanced Raman Scattering (SERS) substrates and modified them with 1,2-ethanedithiol to quench the high luminescence excitation background signals derived from the high density of localized surface plasmon resonance. To improve the surface hydrophilicity, zwitterionic copolymer PGMA-r-PSBMA was grafted onto the nanosurface of Au NRs, which was confirmed by contact angle analysis and AFM. Raman spectra of the copolymer were observed to confirm the successful grafting of Au NRs, which was also corroborated by TEM and SEM. The Au NRs could easily trap the small polar NDMA and NDEA molecules in aqueous solution due to strong zwitterionic hydrophilicity. Furthermore, the self-association of the anions and cations of the polymeric chain grafted in the hot spot zone assisted in trapping the NDMA/NDEA polar molecules. The Raman scattering cross-section of NDMA/NDEA molecules could be enhanced through the chemical linkage of 1,2-ethanedithiol and the self-association behavior of the zwitterionic copolymer. Accordingly, for the first time, we detected the characteristic peaks of NDMA/NDEA through SERS with detection limit of 10-8 M for both molecules.
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PMID:The surface-enhanced Raman scattering detection of N-nitrosodimethylamine and N-nitrosodiethylamine via gold nanorod arrays with a chemical linkage of zwitterionic copolymer. 3184 33