Rhodamine 6G-doped mesostructured silica is prepared by an acidic sol−gel route using poly-b-poly(propylene oxide)-b-poly(ethylene oxide) (EOx−POy−EOx) block copolymer surfactants. Using low-refractive-index (n ∼ 1.2) mesoporous SiO2 as a support, the synthesis is combined with soft lithography to produce high-quality waveguides. This enables efficient waveguiding in the line-patterned rhodamine 6G-doped mesostructured domains, which have a higher refractive index than both the mesoporous support and cladding. For the structure-directing block copolymer surfactants used, (EO)20(PO)70(EO)20 (P123) and (EO)106(PO)70(EO)106 (F127), X-ray diffraction patterns and transmission electron microscopy reveal hexagonal mesophases, whose longitudinal cylinder axes are aligned predominantly parallel to the substrate plane. For samples made by micromolding-in-capillaries (MIMIC), the longitudinal axes are also aligned along the longitudinal waveguide axes. Samples made by micromolding also possess a high mesostructural order, though in the absence of an aligning flow field, their long-range order (ca. several hundred nanometers) is lower than for samples processed using the MIMIC technique. When optically pumped, the rhodamine 6G-doped waveguides exhibit amplified spontaneous emission with thresholds as low as ∼6 kW cm-2, substantially lower than rhodamine 6G-doped sol−gel glasses. This is attributed to the ability of the polymeric surfactant to co-assemble with the dye molecules, thereby leading to high dye dispersions and reduced dye dimerization. Additionally, rhodamine 6G shows good photostablility in the mesostructured waveguides, similar to that of rhodamine 6G in organically modified silicates.
Epigenetic variations in peripheral blood have potential as biomarkers for disease. This systematic review assesses the association of lung function and chronic obstructive pulmonary disease (COPD) with DNA methylation profiles in peripheral blood from population-based studies. Online databases Medline, Embase, and Web of Science were searched. Google Scholar was searched to identify grey literature. After removing duplicate articles, 1155 articles were independently screened by two investigators. Peer reviewed reports on population-based studies that examined peripheral blood DNA methylation in participants with measured lung function (FEV1, FEV1/FVC ratio) or known COPD status were selected for full-text review. Six articles were suitable for inclusion. Information regarding study characteristics, designs, methodologies and conclusions was extracted. A narrative synthesis was performed based on published results. Three of the six articles assessed the association of COPD with DNA methylation, and two of these also included associations with lung function. Overall, five reports examined the association of lung function with DNA methylation profiles. Five of the six articles reported 'significant' results. However, no consistent CpG sites were identified across studies for COPD status or lung function values. DNA methylation patterns in peripheral blood from individuals with reduced lung function or COPD may be different to those in people with normal lung function. However, this systematic review did not find any consistent associations of lung function or COPD with differentially methylated CpG sites. Large studies with a longitudinal design to address reverse causality may prove a more fruitful area of research. PROSPERO 2016: CRD42016037352 .
ADVERTISEMENT RETURN TO ISSUENanosecondsNEXTNanowire SuperlatticesCharles M. LieberView Author Information Department of Chemistry, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138 Cite this: Nano Letters 2002, 2, 2, 81–82Publication Date (Web):January 25, 2002Publication History Received21 January 2002Published online25 January 2002Published inissue 1 February 2002https://pubs.acs.org/doi/10.1021/nl020289dhttps://doi.org/10.1021/nl020289dnewsACS PublicationsCopyright © 2002 American Chemical SocietyRequest reuse permissionsArticle Views2107Altmetric-Citations98LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Chemical structure,Epitaxy,Lattices,Nanoscale,Nanowires Get e-Alerts
This Review discusses ionic electrets: their preparation, their mechanisms of formation, tools for their characterization, and their applications. An electret is a material that has a permanent, macroscopic electric field at its surface; this field can arise from a net orientation of polar groups in the material, or from a net, macroscopic electrostatic charge on the material. An ionic electret is a material that has a net electrostatic charge due to a difference in the number of cationic and anionic charges in the material. Any material that has ions at its surface, or accessible in its interior, has the potential to become an ionic electret. When such a material is brought into contact with some other material, ions can transfer between them. If the anions and cations have different propensities to transfer, the unequal transfer of these ions can result in a net transfer of charge between the two materials. This Review focuses on the experimental evidence and theoretical models for the formation of ionic electrets through this ion-transfer mechanism, and proposes--as a still-unproved hypothesis--that this ion-transfer mechanism may also explain the ubiquitous contact electrification ("static electricity") of materials, such as organic polymers, that do not explicitly have ions at their surface.
We review recent studies of solution-based hierarchical organization of nanowire building blocks. Nanowires have been aligned with controlled nanometer to micrometer scale separation using the Langmuir-Blodgett technique, transferred to planar substrates in a layer-by-layer process to form parallel and crossed nanowire structures over centimeter length scales, and then efficiently patterned into repeating arrays of controlled dimensions and pitch using photolithography. The hierarchically-organized nanowires open up key opportunities in several general areas of nanoscale science and technology. First, hierarchically-assembled nanowire arrays have been used as masks to define nanometer scale metal lines and surface features over large areas. Second, hierarchically-assembled nanowire arrays have been used to fabricate fully-scalable centimeter size arrays of field-effect transistors in high yields without requiring alignment of individual nanowires to output electrodes. Diverse applications of this approach for enabling a broad range of functional nanosystems, including macroelectronic and sensing applications, are described.
