Designed Synthesis of Mesoporous Solid-Supported Lewis Acid-Base Pairs and Their CO₂ Adsorption Behaviors

Zakharova, Maria V.,Masoumifard, Nima,Hu, Yimu,Han, Jongho,Kleitz, Freddy,Fontaine, Fre&#x301,dé,ric-Georges American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.15

<P>Conventional amines and phosphines, such as diethylenetriamine, diphenylpropylphosphine, triethylamine, and tetramethylpiperidine, were grafted or impregnated on the surface of metalated SBA-15 materials, such as <B>Ti</B>-, <B>Al</B>-, and <B>Zr</B>-SBA-15, to generate air-stable solid-supported Lewis acid-base pairs. The Lewis acidity of the metalated materials before and after the introduction of Lewis bases was verified by means of pyridine adsorption-Fourier transform infrared spectroscopy. Detailed characterization of the materials was achieved by solid-state <SUP>13</SUP>C and <SUP>31</SUP>P MAS NMR spectroscopy, low-temperature N<SUB>2</SUB> physisorption, X-ray photoelectron spectroscopy, and energy-dispersive X-ray mapping analyses. Study of their potential interactions with CO<SUB>2</SUB> was performed using CO<SUB>2</SUB> adsorption isotherm experiments, which provided new insights into their applicability as solid CO<SUB>2</SUB> adsorbents. A correlation between solid-supported Lewis acid-base pair strength and the resulting affinity to CO<SUB>2</SUB> is discussed based on the calculation of isosteric enthalpy of adsorption.</P> [FIG OMISSION]</BR>

Novel Mn(II)-Based Metal–Organic Frameworks Isolated in Ionic Liquids

Xu, Ling,Kwon, Young-Uk,de Castro, Baltazar,Cunha-Silva, Lui&#x301,s American Chemical Society 2013 Crystal Growth & Design Vol.13 No.3

<P>An unprecedented series of Mn<SUP>2+</SUP>-based metal–organic framework (MOF) materials prepared and isolated in ionic liquids (ILs) is reported. Ionothermal reactions of Mn(OAc)<SUB>2</SUB> with H<SUB>3</SUB>btc (benzene-1,3,5-tricarboxylic acid) in two groups of [rmi]X (rmi = 1-alkyl-3-methylimidazolium; r = ethyl or propyl, X = Cl, Br, or I) ILs produced three slightly different 3D MOFs formulated as [rmi][Mn(btc)] [r = ethyl (<B>1</B>), propyl (<B>2</B>), and (<B>3</B>)], whose architectures can be envisaged as (3,6)-connected pyr topological nets. Compounds <B>1</B>–<B>3</B> are the preferred products when the metal center is half filled d-shelled Mn with the cations of ILs being [emi]<SUP>+</SUP> or [pmi]<SUP>+</SUP>. The comparison of the ionothermal synthesized M-btc systems suggests a significant combinatorial influence of metal-direction and ILs’ cationic template, contrasting with subtle effect of ILs’ halides on the MOF structures.</P><P>Mn-H<SUB>3</SUB>btc based system was investigated in two groups of [emi]X and [pmi]X ILs, leading to a novel series of 3D MOF compounds which are simplified into the same (3,6)-connected pyr topological net. The results suggest that [rmi][M(btc)] are favorite products when the metal center possess full or half filled d-shells and the cations of ILs are [emi]<SUP>+</SUP> or [pmi]<SUP>+</SUP>, indicating a crucial combination influence of metal-direction, the ILs’ cationic template, and only a subtle effect of ILs’ halides on the formation and structure of the MOFs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cgdefu/2013/cgdefu.2013.13.issue-3/cg301725z/production/images/medium/cg-2012-01725z_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cg301725z'>ACS Electronic Supporting Info</A></P>

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>

Tuning the Direction of Intramolecular Charge Transfer and the Nature of the Fluorescent State in a T-Shaped Molecular Dyad

Felouat, Abdellah,D’Ale&#x301,o, Anthony,Charaf-Eddin, Azzam,Jacquemin, Denis,Le Guennic, Boris,Kim, Eunsun,Lee, Kwang Jin,Woo, Jae Heun,Ribierre, Jean-Charles,Wu, Jeong Weon,Fages, Fre&#x301,dé American Chemical Society 2015 The Journal of physical chemistry A Vol.119 No.24

<P>Controlling photoinduced intramolecular charge transfer at the molecular scale is key to the development of molecular devices for nanooptoelectronics. Here, we describe the design, synthesis, electronic characterization, and photophysical properties of two electron donor–acceptor molecular systems that consist of tolane and BF<SUB>2</SUB>-containing curcuminoid chromophoric subunits connected in a T-shaped arrangement. The two π-conjugated segments intersect at the electron acceptor dioxaborine core. From steady-state electronic absorption and fluorescence emission, we find that the photophysics of the dialkylamino-substituted analogue is governed by the occurrence of two closely lying excited states. From DFT calculations, we show that excitation in either of these two states results in a distinct shift of the electron density, whether it occurs along the curcuminoid or tolane moiety. Femtosecond transient absorption spectroscopy confirmed these findings. As a consequence, the nature of the emitting state and the photophysical properties are strongly dependent on solvent polarity. Moreover, these characteristics can also be switched by protonation or complexation at the nitrogen atom of the amino group. These features set new approaches toward the construction of a three-terminal molecular system in which the lateral branch would transduce a change of electronic state and ultimately control charge transport in a molecular-scale device.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2015/jpcafh.2015.119.issue-24/acs.jpca.5b03699/production/images/medium/jp-2015-03699g_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b03699'>ACS Electronic Supporting Info</A></P>

Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission

Quan, Li Na,Zhao, Yongbiao,Garci&#x301,a de Arquer, F. Pelayo,Sabatini, Randy,Walters, Grant,Voznyy, Oleksandr,Comin, Riccardo,Li, Yiying,Fan, James Z.,Tan, Hairen,Pan, Jun,Yuan, Mingjian,Bakr, Osman American Chemical Society 2017 NANO LETTERS Vol.17 No.6

<P>Organo-metal halide perovskites are a promising platform for optoelectronic applications in view of their excellent charge-transport and bandgap tunability. However, their low photoluminescence quantum efficiencies, especially in low-excitation regimes, limit their efficiency for light emission. Consequently, perovskite light-emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield, even at low excitation intensities. We tailor the composition of quasi-2D perovskites to direct the energy transfer into the lowest-bandgap minority phase and to do so faster than it is lost to nonradiative centers. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm(2), yielding a ratio of quantum yield to excitation intensity of 0.3 cm(2)/mW; this represents a decrease of 2 orders of magnitude in the excitation power required to reach high efficiency compared with the best prior reports. Using this strategy, we report light-emitting diodes with external quantum efficiencies of 7.4% and a high luminescence of 8400 cd/m(2).</P>

Acid-Assisted Ligand Exchange Enhances Coupling in Colloidal Quantum Dot Solids

Jo, Jea Woong,Choi, Jongmin,Garci&#x301,a de Arquer, F. Pelayo,Seifitokaldani, Ali,Sun, Bin,Kim, Younghoon,Ahn, Hyungju,Fan, James,Quintero-Bermudez, Rafael,Kim, Junghwan,Choi, Min-Jae,Baek, Se-Woong American Chemical Society 2018 NANO LETTERS Vol.18 No.7

<P>Colloidal quantum dots (CQDs) are promising solution-processed infrared-absorbing materials for optoelectronics. In these applications, it is crucial to replace the electrically insulating ligands used in synthesis to form strongly coupled quantum dot solids. Recently, solution-phase ligand-exchange strategies have been reported that minimize the density of defects and the polydispersity of CQDs; however, we find herein that the new ligands exhibit insufficient chemical reactivity to remove original oleic acid ligands completely. This leads to low CQD packing and correspondingly low electronic performance. Here we report an acid-assisted solution-phase ligand-exchange strategy that, by enabling efficient removal of the original ligands, enables the synthesis of densified CQD arrays. Our use of hydroiodic acid simultaneously facilitates high CQD packing via proton donation and CQD passivation through iodine. We demonstrate highly packed CQD films with a 2.5 times increased carrier mobility compared with prior exchanges. The resulting devices achieve the highest infrared photon-to-electron conversion efficiencies (>50%) reported in the spectral range of 0.8 to 1.1 eV.</P> [FIG OMISSION]</BR>

Defect Annihilation Pathways in Directed Assembly of Lamellar Block Copolymer Thin Films

Hur, Su-Mi,Thapar, Vikram,Rami&#x301,rez-Herna&#x301,ndez, Abelardo,Nealey, Paul F.,de Pablo, Juan J. American Chemical Society 2018 ACS NANO Vol.12 No.10

<P>Defects in highly ordered self-assembled block copolymers represent an important roadblock toward the adoption of these materials in a wide range of applications. This work examines the pathways for annihilation of defects in symmetric diblock copolymers in the context of directed assembly using patterned substrates. Past theoretical and computational studies of such systems have predicted minimum free energy pathways that are characteristic of an activated process. However, they have been limited to adjacent dislocations with opposite Burgers vectors. By relying on a combination of advanced sampling techniques and particle-based simulations, this work considers the long-range interaction between dislocation pairs, both on homogeneous and nanopatterned substrates. As illustrated here, these interactions are central to understanding the defect structures that are most commonly found in applications and in experimental studies of directed self-assembly. More specifically, it is shown that, for dislocation dipoles separated by several lamellae, multiple consecutive free energy barriers lead to effective kinetic barriers that are an order of magnitude larger than those originally reported in the literature for tightly bound dislocation pairs. It is also shown that annihilation pathways depend strongly on both the separation between dislocations and their relative position with respect to the substrate guiding stripes used to direct the assembly.</P> [FIG OMISSION]</BR>

Switching Off FRET in the Hybrid Assemblies of Diblock Copolymer Micelles, Quantum Dots, and Dyes by Plasmonic Nanoparticles

Kim, Ki-Se,Kim, Jeong-Hee,Kim, Hun,Laquai, Fre&#x301,dé,ric,Arifin, Eric,Lee, Jin-Kyu,Yoo, Seong Il,Sohn, Byeong-Hyeok American Chemical Society 2012 ACS NANO Vol.6 No.6

<P>Recently, it has been noticed that surface plasmon resonance of metal nanoparticles can alter the intrinsic properties of nearby fluorophores. Field enhancement and radiative decay engineering are major principles for understanding a number of experimental observations such as enhanced and quenched emission of fluorophores in the vicinity of metal nanoparticles. At the same time, there are apparent similarities between surface-plasmon-coupled fluorescence and fluorescence resonance energy transfer (FRET), as both are near-field through-space interactions. From this perspective, we hypothesize that donor–acceptor interaction in the FRET can be altered by metal nanoparticles. Our approach is based on diblock copolymer micelles, which have been widely applied for nanoscale arrangement of functionalities. By applying self-assembling techniques of copolymer micelles to organize the spatial location of semiconductor quantum dots, fluorescent dyes, and metal nanoparticles, the FRET in hybrid assemblies can be switched off by plasmonic effects.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-6/nn301893e/production/images/medium/nn-2012-01893e_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn301893e'>ACS Electronic Supporting Info</A></P>

Mixing and matching TREK/TRAAK subunits generate heterodimeric K_2P channels with unique properties

Blin, Sandy,Ben Soussia, Ismail,Kim, Eun-Jin,Brau, Fre&#x301,dé,e&#x301,ric,Kang, Dawon,Lesage, Florian,Bichet, Delphine National Academy of Sciences 2016 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.113 No.15

<P>The tandem of pore domain in a weak inwardly rectifying K+ channel (Twik)-related acid-arachidonic activated K+ channel (TRAAK) and Twik-related K+ channels (TREK) 1 and TREK2 are active as homodimers gated by stretch, fatty acids, pH, and G protein-coupled receptors. These two-pore domain potassium (K-2P) channels are broadly expressed in the nervous system where they control excitability. TREK/TRAAK KO mice display altered phenotypes related to nociception, neuroprotection afforded by polyunsaturated fatty acids, learning and memory, mood control, and sensitivity to general anesthetics. These channels have emerged as promising targets for the development of new classes of anesthetics, analgesics, antidepressants, neuroprotective agents, and drugs against addiction. Here, we show that the TREK1, TREK2, and TRAAK subunits assemble and form active heterodimeric channels with electrophysiological, regulatory, and pharmacological properties different from those of homodimeric channels. Heteromerization occurs between all TREK variants produced by alternative splicing and alternative translation initiation. These results unveil a previously unexpected diversity of K-2P channels that will be challenging to analyze in vivo, but which opens new perspectives for the development of clinically relevant drugs.</P>

Blue-Shifting Intramolecular Charge Transfer Emission by Nonlocal Effect of Hyperbolic Metamaterials

Lee, Kwang Jin,Lee, Yeon Ui,Fages, Fre&#x301,dé,ric,Ribierre, Jean-Charles,Wu, Jeong Weon,D’Ale&#x301,o, Anthony American Chemical Society 2018 NANO LETTERS Vol.18 No.2

<P>Metallic nanostructures permit controlling various photophysical processes by coupling photons with plasmonic oscillation of electrons confined in the tailored nanostructures. One example is hyperbolic metamaterial (HMM) leading to an enhanced spontaneous emission rate of emitters located nearby. Noting that emission in organic molecules is from either pi-pi* or intramolecular charge-transfer (ICT) states, we address here how HMM modifies ICT emission spectral features by comparing them with a spectral shift dependent on the local polarity of the medium. The 7.0 nm blue shift is observed in ICT emission from 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dispersed into a polymer matrix prepared on HMM multilayered structure, while no spectral shift is observed in pi-pi* emission from perylene diimide. In the frame of the Lippert-Mataga formalism, the blue shift is explained by the HMM nonlocal effects resulting from 8% decrease in refractive index and 18% reduction in dielectric permittivity. This phenomenon was also shown in a hemi-curcuminoid borondifluoride dye yielding 15.0 nm blue shift. Such a capability of spectral shift control in films by HMM structure opens new prospects for engineering organic light-emitting devices.</P>