Temperature and Magnetic-Field Dependence of Radiative Decay in Colloidal Germanium Quantum Dots

Robel, Istva&#x301,n,Shabaev, Andrew,Lee, Doh C.,Schaller, Richard D.,Pietryga, Jeffrey M.,Crooker, Scott A.,L. Efros, Alexander,Klimov, Victor I. American Chemical Society 2015 Nano letters Vol.15 No.4

<P>We conduct spectroscopic and theoretical studies of photoluminescence (PL) from Ge quantum dots (QDs) fabricated via colloidal synthesis. The dynamics of late-time PL exhibit a pronounced dependence on temperature and applied magnetic field, which can be explained by radiative decay involving two closely spaced, slowly emitting exciton states. In 3.5 nm QDs, these states are separated by ∼1 meV and are characterized by ∼82 μs and ∼18 μs lifetimes. By using a four-band formalism, we calculate the fine structure of the indirect band-edge exciton arising from the electron–hole exchange interaction and the Coulomb interaction of the Γ-point hole with the anisotropic charge density of the <I>L</I>-point electron. The calculations suggest that the observed PL dynamics can be explained by phonon-assisted recombination of excitons thermally distributed between the lower-energy “dark” state with the momentum projection <I>J</I> = ± 2 and a higher energy “bright” state with <I>J</I> = ± 1. A fairly small difference between lifetimes of these states is due to their mixing induced by the exchange term unique to crystals with a highly symmetric cubic lattice such as Ge.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-4/acs.nanolett.5b00344/production/images/medium/nl-2015-003445_0005.gif'></P>

Binding of EBP50 to Nox organizing subunit p47^<i>phox</i> is pivotal to cellular reactive species generation and altered vascular phenotype

Al Ghouleh, Imad,Meijles, Daniel N.,Mutchler, Stephanie,Zhang, Qiangmin,Sahoo, Sanghamitra,Gorelova, Anastasia,Henrich Amaral, Jefferson,Rodre&#x301,í,guez, Andre&#x301,s I.,Mamonova, Tatyana,So National Academy of Sciences 2016 Proceedings of the National Academy of Sciences Vol.113 No.36

<P>Despite numerous reports implicating NADPH oxidases (Nox) in the pathogenesis of many diseases, precise regulation of this family of professional reactive oxygen species (ROS) producers remains unclear. A unique member of this family, Nox1 oxidase, functions as either a canonical or hybrid system using Nox organizing subunit 1 (NoxO1) or p47(phox), respectively, the latter of which is functional in vascular smooth muscle cells (VSMC). In this manuscript, we identify critical requirement of ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50; aka NHERF1) for Nox1 activation and downstream responses. Superoxide (O-2(center dot-)) production induced by angiotensin II (AngII) was absent in mouse EBP50 KO VSMC vs. WT. Moreover, ex vivo incubation of aortas with AngII showed a significant increase in O-2(center dot-)-in WT but not EBP50 or Nox1 nulls. Similarly, lipopolysaccharide (LPS)-induced oxidative stress was attenuated in femoral arteries from EBP50 KO vs. WT. In silico analyses confirmed by confocal microscopy, immunoprecipitation, proximity ligation assay, FRET, and gain-/ loss-of-function mutagenesis revealed binding of EBP50, via its PDZ domains, to a specific motif in p47(phox). Functional studies revealed AngII-induced hypertrophy was absent in EBP50 KOs, and in VSMC overexpressing EBP50, Nox1 gene silencing abolished VSMC hypertrophy. Finally, ex vivo measurement of lumen diameter in mouse resistance arteries exhibited attenuated AngII-induced vasoconstriction in EBP50 KO vs. WT. Taken together, our data identify EBP50 as a previously unidentified regulator of Nox1 and support that it promotes Nox1 activity by binding p47(phox). This interaction is pivotal for agonist-induced smooth muscle ROS, hypertrophy, and vasoconstriction and has implications for ROS-mediated physiological and pathophysiological processes.</P>

Iron-Oxide-Supported Nanocarbon in Lithium-Ion Batteries, Medical, Catalytic, and Environmental Applications

Tuc&#x30c,ek, Jir&#x30c,í,Kemp, Kingsley Christian,Kim, Kwang Soo,Zbor&#x30c,il, Radek American Chemical Society 2014 ACS NANO Vol.8 No.8

<P>Owing to the three different orbital hybridizations carbon can adopt, the existence of various carbon nanoallotropes differing also in dimensionality has been already affirmed with other structures predicted and expected to emerge in the future. Despite numerous unique features and applications of 2D graphene, 1D carbon nanotubes, or 0D fullerenes, nanodiamonds, and carbon quantum dots, which have been already heavily explored, any of the existing carbon allotropes do not offer competitive magnetic properties. For challenging applications, carbon nanoallotropes are functionalized with magnetic species, especially of iron oxide nature, due to their interesting magnetic properties (superparamagnetism and strong magnetic response under external magnetic fields), easy availability, biocompatibility, and low cost. In addition, combination of iron oxides (magnetite, maghemite, hematite) and carbon nanostructures brings enhanced electrochemical performance and (photo)catalytic capability due to synergetic and cooperative effects. This work aims at reviewing these advanced applications of iron-oxide-supported nanocarbon composites where iron oxides play a diverse role. Various architectures of carbon/iron oxide nanocomposites, their synthetic procedures, physicochemical properties, and applications are discussed in details. A special attention is devoted to hybrids of carbon nanotubes and rare forms (mesoporous carbon, nanofoam) with magnetic iron oxide carriers for advanced environmental technologies. The review also covers the huge application potential of graphene/iron oxide nanocomposites in the field of energy storage, biomedicine, and remediation of environment. Among various discussed medical applications, magnetic composites of zero-dimensional fullerenes and carbon dots are emphasized as promising candidates for complex theranostics and dual magneto-fluorescence imaging.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-8/nn501836x/production/images/medium/nn-2014-01836x_0047.gif'></P>

Evolution of gene regulation in ruminants differs between evolutionary breakpoint regions and homologous synteny blocks

Farre&#x301,, Marta,Kim, Jaebum,Proskuryakova, Anastasia A.,Zhang, Yang,Kulemzina, Anastasia I.,Li, Qiye,Zhou, Yang,Xiong, Yingqi,Johnson, Jennifer L.,Perelman, Polina L.,Johnson, Warren E.,Warren, We Cold Spring Harbor Laboratory Press 2019 Genome research Vol.29 No.4

<P>The role of chromosome rearrangements in driving evolution has been a long-standing question of evolutionary biology. Here we focused on ruminants as a model to assess how rearrangements may have contributed to the evolution of gene regulation. Using reconstructed ancestral karyotypes of Cetartiodactyls, Ruminants, Pecorans, and Bovids, we traced patterns of gross chromosome changes. We found that the lineage leading to the ruminant ancestor after the split from other cetartiodactyls was characterized by mostly intrachromosomal changes, whereas the lineage leading to the pecoran ancestor (including all livestock ruminants) included multiple interchromosomal changes. We observed that the liver cell putative enhancers in the ruminant evolutionary breakpoint regions are highly enriched for DNA sequences under selective constraint acting on lineage-specific transposable elements (TEs) and a set of 25 specific transcription factor (TF) binding motifs associated with recently active TEs. Coupled with gene expression data, we found that genes near ruminant breakpoint regions exhibit more divergent expression profiles among species, particularly in cattle, which is consistent with the phylogenetic origin of these breakpoint regions. This divergence was significantly greater in genes with enhancers that contain at least one of the 25 specific TF binding motifs and located near bovidae-to-cattle lineage breakpoint regions. Taken together, by combining ancestral karyotype reconstructions with analysis of <I>cis</I> regulatory element and gene expression evolution, our work demonstrated that lineage-specific regulatory elements colocalized with gross chromosome rearrangements may have provided valuable functional modifications that helped to shape ruminant evolution.</P>

Immobilization of Lambda Exonuclease onto Polymer Micropillar Arrays for the Solid-Phase Digestion of dsDNAs

Oliver-Calixte, Nyote&#x301,J.,Uba, Franklin I.,Battle, Katrina N.,Weerakoon-Ratnayake, Kumuditha M.,Soper, Steven A. American Chemical Society 2014 ANALYTICAL CHEMISTRY - Vol.86 No.9

<P>The process of immobilizing enzymes onto solid supports for bioreactions has some compelling advantages compared to their solution-based counterpart including the facile separation of enzyme from products, elimination of enzyme autodigestion, and increased enzyme stability and activity. We report the immobilization of λ-exonuclease onto poly(methylmethacrylate) (PMMA) micropillars populated within a microfluidic device for the on-chip digestion of double-stranded DNA. Enzyme immobilization was successfully accomplished using 3-(3-dimethylaminopropyl) carbodiimide/<I>N</I>-hydroxysuccinimide (EDC/NHS) coupling to carboxylic acid functionalized PMMA micropillars. Our results suggest that the efficiency for the catalysis of dsDNA digestion using λ-exonuclease, including its processivity and reaction rate, were higher when the enzyme was attached to a solid support compared to the free solution digestion. We obtained a clipping rate of 1.0 × 10<SUP>3</SUP> nucleotides s<SUP>–1</SUP> for the digestion of λ-DNA (48.5 kbp) by λ-exonuclease. The kinetic behavior of the solid-phase reactor could be described by a fractal Michaelis–Menten model with a catalytic efficiency nearly 17% better than the homogeneous solution-phase reaction. The results from this work will have important ramifications in new single-molecule DNA sequencing strategies that employ free mononucleotide identification.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2014/ancham.2014.86.issue-9/ac5002965/production/images/medium/ac-2014-002965_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac5002965'>ACS Electronic Supporting Info</A></P>

Nanoplasmonic Ruler for Measuring Separation Distance between Supported Lipid Bilayers and Oxide Surfaces

Ferhan, Abdul Rahim,S&#x30c,pac&#x30c,kova&#x301,, Barbora,Jackman, Joshua A.,Ma, Gamaliel J.,Sut, Tun Naw,Homola, Jir&#x30c,í,Cho, Nam-Joon American Chemical Society 2018 ANALYTICAL CHEMISTRY - Vol.90 No.21

<P>Unraveling the details of how supported lipid bilayers (SLBs) are coupled to oxide surfaces is experimentally challenging, and there is an outstanding need to develop highly surface-sensitive measurement strategies to determine SLB separation distances. Indeed, subtle variations in separation distance can be associated with significant differences in bilayer-substrate interaction energy. Herein, we report a nanoplasmonic ruler strategy to measure the absolute separation distance between SLBs and oxide surfaces. A localized surface plasmon resonance (LSPR) sensor was employed to track SLB formation onto titania- and silica-coated gold nanodisk arrays. To interpret measurement data, an analytical model relating the LSPR measurement response to bilayer-substrate separation distance was developed based on finite-difference time-domain (FDTD) simulations and theoretical calculations. The results indicate that there is a larger separation distance between SLBs and titania surfaces than silica surfaces, and the trend was consistent across three tested lipid compositions. We discuss these findings within the context of the interfacial forces underpinning bilayer-substrate interactions, and the nanoplasmonic ruler strategy provides the first direct experimental evidence comparing SLB separation distances on titania and silica surfaces.</P> [FIG OMISSION]</BR>

High-Voltage Cathode Materials for Lithium-Ion Batteries: Freeze-Dried LiMn_0.8Fe_0.1M_0.1PO₄/C (M = Fe, Co, Ni, Cu) Nanocomposites

Iturrondobeitia, Amaia,Gon&#x303,i, Aintzane,Gil de Muro, Izaskun,Lezama, Luis,Kim, Chunjoong,Doeff, Marca,Cabana, Jordi,Rojo, Teo&#x301,filo American Chemical Society 2015 Inorganic Chemistry Vol.54 No.6

<P>Four LiMn<SUB>0.8</SUB>Fe<SUB>0.1</SUB>M<SUB>0.1</SUB>PO<SUB>4</SUB>/C (M = Fe, Co, Ni, Cu) cathode materials have been synthesized via a freeze-drying method. The samples have been characterized by powder X-ray diffraction, transmission electron microscopy, magnetic susceptibility, and electrochemical measurements. The composition and effective insertion of the transition-metal substituents in LiMnPO<SUB>4</SUB> have been corroborated by elemental analysis, the evolution of the crystallographic parameters, and the magnetic properties. The morphological characterization of the composites has demonstrated that the phosphate nanoparticles are enclosed in a matrix of amorphous carbon. Among them, LiMn<SUB>0.8</SUB>Fe<SUB>0.1</SUB>Ni<SUB>0.1</SUB>PO<SUB>4</SUB>/C is the most promising cathode material, providing a good electrochemical performance in all aspects: high voltage and specific capacity values, excellent cyclability, and good rate capability. This result has been attributed to several factors, such as the suitable morphology of the sample, the good connection afforded by the in situ generated carbon, and the amelioration of the structural stress provided by the presence of Ni<SUP>2+</SUP> and Fe<SUP>2+</SUP> in the olivine structure.</P><P>Four nanosized LiMn<SUB>0.8</SUB>Fe<SUB>0.1</SUB>M<SUB>0.1</SUB>PO<SUB>4</SUB>/C (M = Fe, Co, Ni, Cu) cathode materials have been synthesized via a freeze-drying method. The effective insertion of the substituents in LiMnPO<SUB>4</SUB> have been corroborated by elemental analysis, the evolution of the crystallographic parameters, and the magnetic properties. LiMn<SUB>0.8</SUB>Fe<SUB>0.1</SUB>Ni<SUB>0.1</SUB>PO<SUB>4</SUB>/C is the most promising material, providing a good electrochemical performance in all aspects: high voltage and specific capacity values, excellent cyclability, and good rate capability.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2015/inocaj.2015.54.issue-6/ic5028306/production/images/medium/ic-2014-028306_0007.gif'></P>

Polycrystalline Graphene with Single Crystalline Electronic Structure

Brown, Lola,Lochocki, Edward B.,Avila, Jose&#x301,Kim, Cheol-Joo,Ogawa, Yui,Havener, Robin W.,Kim, Dong-Ki,Monkman, Eric J.,Shai, Daniel E.,Wei, Haofei I.,Levendorf, Mark P.,Asensio, Marí,a,Shen American Chemical Society 2014 NANO LETTERS Vol.14 No.10

<P>We report the scalable growth of aligned graphene and hexagonal boron nitride on commercial copper foils, where each film originates from multiple nucleations yet exhibits a single orientation. Thorough characterization of our graphene reveals uniform crystallographic and electronic structures on length scales ranging from nanometers to tens of centimeters. As we demonstrate with artificial twisted graphene bilayers, these inexpensive and versatile films are ideal building blocks for large-scale layered heterostructures with angle-tunable optoelectronic properties.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-10/nl502445j/production/images/medium/nl-2014-02445j_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl502445j'>ACS Electronic Supporting Info</A></P>

Pyrrole- and Naphthobipyrrole-Strapped Calix[4]pyrroles as Azide Anion Receptors

Kim, Seung Hyeon,Lee, Juhoon,Vargas-Zu&#x301,n&#x303,iga, Gabriela I.,Lynch, Vincent M.,Hay, Benjamin P.,Sessler, Jonathan L.,Kim, Sung Kuk American Chemical Society 2018 Journal of organic chemistry Vol.83 No.5

<P>The binding interactions between the azide anion (N<SUB>3</SUB><SUP>-</SUP>) and the strapped calix[4]pyrroles <B>2</B> and <B>3</B> bearing auxiliary hydrogen bonding donors on the bridging moieties, as well as of normal calix[4]pyrrole <B>1</B>, were investigated via <SUP>1</SUP>H NMR spectroscopic and isothermal titration calorimetry analyses. The resulting data revealed that receptors <B>2</B> and <B>3</B> have significantly higher affinities for the azide anion in organic media as compared with the unfunctionalized calix[4]pyrrole <B>1</B> and other azide receptors reported to date. Single crystal X-ray diffraction analyses and calculations using density functional theory revealed that receptor <B>2</B> binds CsN<SUB>3</SUB> in two distinct structural forms. As judged from the metric parameters, in the resulting complexes one limiting azide anion resonance contributor is favored over the other, with the specifics depending on the binding mode. In contrast to what is seen for <B>2</B>, receptor <B>3</B> forms a CsN<SUB>3</SUB> complex in 20% CD<SUB>3</SUB>OD in CDCl<SUB>3</SUB>, wherein the azide anion is bound only vertically to the NH protons of the calix[4]pyrrole and the cesium cation is complexed within the cone shaped-calix[4]pyrrole bowl. The bound cesium cation is also in close proximity to a naphthobipyrrole subunit present in a different molecule, forming an apparent cation-π complex.</P> [FIG OMISSION]</BR>

Correlating Carrier Dynamics and Photocatalytic Hydrogen Generation in Pt Decorated CdSe Tetrapods as a Function of Cocatalyst Size

Karakus, Melike,Sung, Younghun,Wang, Hai I.,Mics, Zolta&#x301,n,Char, Kookheon,Bonn, Mischa,Ca&#x301,novas, Enrique American Chemical Society 2017 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.121 No.24

<P>We investigate photoinduced carrier dynamics by time resolved terahertz spectroscopy (TRTS) in Pt nanoparticle decorated CdSe tetrapods as a function of Pt nanoparticles size (and identical areal density). We find that the collection efficiency of electrons photo generated in the tetrapods by the Pt particle increases as a function of Pt nanoparticle size. However, the photocatalytic H-2 generation efficiency is reduced for tetrapods decorated with larger Pt particles. Our results demonstrate a competition between electron capture efficiency at the semiconducting/metal interface, increasing with nanoparticles size, and electron release efficiency at the metal/water interface, decreasing with nanoparticles size. This trade-off defines an optimum for photocatalytic H-2 generation in Pt cocatalyst decorated CdSe tetrapods as a function of Pt size.</P>