Thermal Imprint Introduced Crystallization of A Solution Processed Subphthalocyanine Thin Film

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134175/1/admi201600179.pd

DNA Adsorption by ZnO Nanoparticles near Its Solubility Limit: Implications for DNA Fluorescence Quenching and DNAzyme Activity Assays

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, © 2016 American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see Ma, L., Liu, B., Huang, P.-J. J., Zhang, X., & Liu, J. (2016). DNA Adsorption by ZnO Nanoparticles near Its Solubility Limit: Implications for DNA Fluorescence Quenching and DNAzyme Activity Assays. Langmuir, 32(22), 5672–5680. https://doi.org/10.1021/acs.langmuir.6b00906Zinc oxide (ZnO) is a highly important material, and Zn2+ is a key metal ion in biology. ZnO and Zn2+ interconvert via dissolution and hydrolysis/condensation. In this work, we explore their interactions with DNA, which is important for biointerface, analytical, and bioinorganic chemistry. Fluorescently labeled DNA oligonucleotides were adsorbed by a low concentration (around 5 mu g/mL) of ZnO nanoparticles, near the solubility limit. Right after mixing, fluorescence quenching occurred, indicating DNA adsorption. Then, fluorescence recovered, attributable to ZnO dissolution. The dissolution rate followed A(5) > T-5 > C-5. Dissolution was slower with longer DNA. The adsorption affinity was also measured by a displacement assay to be G(5) > C-5 > T-5 > A(5), suggesting that tightly adsorbed DNA can retard ZnO dissolution. Electrostatic interactions are important for DNA adsorption because ZnO is positively charged at neutral pH, and a high salt concentration inhibits DNA adsorption. Next, in situ formation of ZnO from Zn2+ was studied. First, titrating Zn2+ into a fluorescently labeled oligonucleotide at pH 7.5 resulted in an abrupt fluorescence quenching beyond 0.2 mM Zn2+. At pH 6, quenching occurred linearly with the Zn2+ concentration, suggesting the effect of Zn2+ precipitation at pH 7.5. Second, a Zn2+-dependent DNA-cleaving DNAzyme was studied. This DNAzyme was inhibited at higher than 2 mM Zn2+, attributable to Zn2+ precipitation and adsorption of the DNAzyme. This paper has established the interplay between DNA, Zn2+, and ZnO. This understanding can avoid misinterpretation of DNA assay results and adds knowledge to DNA immobilization.Natural Sciences and Engineering Research Council of Canada (NSERC

Bulk Assembly of Organic Metal Halide Nanoribbons

Organic metal halide hybrids with low-dimensional structures at the molecular level have received great attention recently for their exceptional structural tunability and unique photophysical properties. Here we report for the first time the synthesis and characterization of a one-dimensional (1D) organic metal halide hybrid material, which contains metal halide nanoribbons with a width of three octahedral units. It is found that this material with a chemical formula C$_8$H$_{28}$N$_5$Pb$_3$Cl$_{11}$ shows a dual emission with a photoluminescence quantum efficiency (PLQE) of around 25% under ultraviolet (UV) light irradiation. Photophysical studies and density functional theory (DFT) calculations suggest the coexisting of delocalized free excitons and localized self-trapped excitons in metal halide nanoribbons leading to the dual emission. This work shows once again the exceptional tunability of organic metal halide hybrids that bridge between molecular systems with localized states and crystalline ones with electronic bands.Comment: 6 pages, 4 figures, plus supporting informatio

A New Type of Quartz Smog Chamber : Design and Characterization

Publisher Copyright: ©Since the 1960s, many indoor and outdoor smog chambers have been developed worldwide. However, most of them are made of Teflon films, which have relatively high background contaminations due to the wall effect. We developed the world's first medium-size quartz chamber (10 m(3)), which is jointed with 32 pieces of 5 mm thick polished quartz glasses and a stainless-steel frame. Characterizations show that this chamber exhibits excellent performance in terms of relative humidity (RH) (2-80%) and temperature (15-30 +/- 1 degrees C) control, mixing efficiency of the reactants (6-8 min), light transmittance (>90% above 290 nm), and wall loss of pollutants. The wall loss rates of the gas-phase pollutants are on the order of 10(-4) min(-1) at 298 K under dry conditions. It is 0.08 h(-1) for 100-500 nm particles, significantly lower than those of Teflon chambers. The photolysis rate of NO2 (J(NO2)) is automatically adjustable to simulate the diurnal variation of solar irradiation from 0 to 0.40 min(-1). The inner surface of the chamber can be repeatedly washed with deionized water, resulting in low background contaminations. Both experiments (toluene-NOx and alpha-pinene-ozone systems) and box model demonstrate that this new quartz chamber can provide high-quality data for investigating SOA and O-3 formation in the atmosphere.Peer reviewe

Surface Effects on Anisotropic Photoluminescence in One-Dimensional Organic Metal Halide Hybrids

One-dimensional (1D) organic metal halide hybrids exhibit strongly anisotropic optical properties, highly efficient light emission, and large Stokes shift, holding promises for novel photodetection and lighting applications. However, the fundamental mechanisms governing their unique optical properties and in particular the impacts of surface effects are not understood. Here, we investigate 1D C4N2H14PbBr4 by polarization-dependent time-averaged and time-resolved photoluminescence (TRPL) spectroscopy, as a function of photoexcitation energy. Surprisingly, we find that the emission under photoexcitation polarized parallel to the 1D metal halide chains can be either stronger or weaker than that under perpendicular polarization, depending on the excitation energy. We attribute the excitation-energy-dependent anisotropic emission to fast surface recombination, supported by first-principles calculations of optical absorption in this material. The fast surface recombination is directly confirmed by TRPL measurements, when the excitation is polarized parallel to the chains. Our comprehensive studies provide a more complete picture for a deeper understanding of the optical anisotropy in 1D organic metal halide hybrids

Management of singlet and triplet excitons for efficient white organic light-emitting devices

Lighting accounts for approximately 22 per cent of the electricity consumed in buildings in the United States, with 40 per cent of that amount consumed by inefficient (similar to 15 lm W-1) incandescent lamps(1,2). This has generated increased interest in the use of white electroluminescent organic light-emitting devices, owing to their potential for significantly improved efficiency over incandescent sources combined with low-cost, high-throughput manufacturability. The most impressive characteristics of such devices reported to date have been achieved in all-phosphor-doped devices, which have the potential for 100 per cent internal quantum efficiency(2): the phosphorescent molecules harness the triplet excitons that constitute three-quarters of the bound electron-hole pairs that form during charge injection, and which (unlike the remaining singlet excitons) would otherwise recombine non-radiatively. Here we introduce a different device concept that exploits a blue fluorescent molecule in exchange for a phosphorescent dopant, in combination with green and red phosphor dopants, to yield high power efficiency and stable colour balance, while maintaining the potential for unity internal quantum efficiency. Two distinct modes of energy transfer within this device serve to channel nearly all of the triplet energy to the phosphorescent dopants, retaining the singlet energy exclusively on the blue fluorescent dopant. Additionally, eliminating the exchange energy loss to the blue fluorophore allows for roughly 20 per cent increased power efficiency compared to a fully phosphorescent device. Our device challenges incandescent sources by exhibiting total external quantum and power efficiencies that peak at 18.7 +/- 0.5 per cent and 37.6 +/- 0.6 lm W-1, respectively, decreasing to 18.4 +/- 0.5 per cent and 23.8 +/- 0.5 lm W-1 at a high luminance of 500 cd m(-2).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62889/1/nature04645.pd

Flexible, Highly Efficient All-Polymer Solar Cells

All-polymer solar cells have shown great potential as flexible and portable power generators. These devices should offer good mechanical endurance with high power-conversion efficiency for viability in commercial applications. In this work, we develop highly efficient and mechanically robust all-polymer solar cells that are based on the PBDTTTPD polymer donor and the P(NDI2HD-T) polymeracceptor. These systems exhibit high power-conversion efficiency of 6.64%. Also, the proposed all-polymer solar cells have even better performance than the control polymer-fullerene devices with phenyl-C 61 -butyric acid methyl ester (PCBM) as the electron acceptor (6.12%). More importantly, our all-polymer solar cells exhibit dramatically enhanced strength and flexibility compared withpolymer/PCBM devices, with 60- and 470-fold improvements in elongation at break and toughness, respectively. The superior mechanical properties of all-polymer solar cells afford greater tolerance to severe deformations than conventional polymer-fullerene solar cells, making them much better candidates for applications in flexible and portable devices.ope

Continuous and comprehensive atmospheric observations in Beijing : a station to understand the complex urban atmospheric environment

Peer reviewe