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High-Performance Supercapacitors Based on Poly(ionic liquid)-Modified Graphene Electrodes
Kim, Tae Young,Lee, Hyun Wook,Stoller, Meryl,Dreyer, Daniel R.,Bielawski, Christopher W.,Ruoff, Rodney S.,Suh, Kwang S. American Chemical Society 2011 ACS NANO Vol.5 No.1
<P>We report a high-performance supercapacitor incorporating a poly(ionic liquid)-modified reduced graphene oxide (PIL:RG-O) electrode and an ionic liquid (IL) electrolyte (specifically, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide or EMIM-NTf<SUB>2</SUB>). PIL:RG-O provides enhanced compatibility with the IL electrolyte, thereby increasing the effective electrode surface area accessible to electrolyte ions. The supercapacitor assembled with PIL:RG-O electrode and EMIM-NTf<SUB>2</SUB> electrolyte showed a stable electrochemical response up to 3.5 V operating voltage and was capable of yielding a maximum energy density of 6.5 W·h/kg with a power density of 2.4 kW/kg. These results demonstrate the potential of the PIL:RG-O material as an electrode in high-performance supercapacitors.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-1/nn101968p/production/images/medium/nn-2010-01968p_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn101968p'>ACS Electronic Supporting Info</A></P>
Atomic-layer deposition of crystalline BeO on SiC
Lee, Seung Min,Jang, Yoonseo,Jung, Jongho,Yum, Jung Hwan,Larsen, Eric S.,Bielawski, Christopher W.,Wang, Weijie,Ryou, Jae-Hyun,Kim, Hyun-Seop,Cha, Ho-Young,Oh, Jungwoo Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.469 No.-
<P><B>Abstract</B></P> <P>For the first time, an epitaxial beryllium oxide (BeO) film was grown on 4H silicon carbide (4H-SiC) by atomic layer deposition (ALD) at a low temperature of 250 °C. The BeO film had a large lattice mismatch with the substrate (>7–8%), but it was successfully grown to a single crystal by domain-matching epitaxy (DME). The bandgap energy, dielectric constant, and thermal conductivity properties of crystalline BeO are suitable for power transistors that require low leakage currents and fast heat dissipation in high electric fields. Physical characterization confirmed the single-crystalline BeO (0 0 2). Raman analysis showed that the E<SUB>1</SUB> and A<SUB>1</SUB> phonon modes of ALD BeO were intermixed with the E<SUB>2</SUB> and A<SUB>1</SUB> phonon modes of SiC, resulting in a significant increase in phonon intensity. After heat treatment at a high temperature, a small amount of SiO<SUB>2</SUB> interfacial oxide was formed but the stoichiometry of BeO was maintained. From the capacitance-voltage (<I>C-V</I>) curves, we obtained a dielectric constant of 6.9 and calculated a low interface trap density of 6 × 10<SUP>10</SUP> cm<SUP>−2</SUP>·eV<SUP>−1</SUP> using the Terman method at <I>E<SUB>c</SUB> </I>-<I>E<SUB>t</SUB> </I> = 0.6 eV. The high bandgap, thermal conductivity, and excellent crystallinity reduced the dangling bonds at the interface of BeO-on-SiC.</P> <P><B>Highlights:</B></P> <P> <UL> <LI> Single-crystalline BeO films are epitaxially grown on 4H-SiC substrates by ALD. </LI> <LI> Domain structures of BeO/4H-SiC (8/7 and 9/8) have residual mismatches of 0.023 nm. </LI> <LI> Bandgap (10.6 eV), permittivity (6.9) and thermal conductivity (330 W/m-K) of BeO are suitable for power transistor. </LI> <LI> Interface trap density of ALD-BeO film is about 6 × 10<SUP>10</SUP> cm<SUP>−2</SUP> eV<SUP>−1</SUP> at <I>E<SUB>c</SUB> </I>-<I>E<SUB>t</SUB> </I> = 0.6 eV. </LI> </UL> </P>
Liu, Di,Bielawski, Christopher W John Wiley Sons, Ltd 2017 Polymer international Vol.66 No.1
<P><B>Abstract</B></P><P>Azido‐functionalized isotactic polypropylene was prepared via the direct CH azidation of a commercially available polymer using a stable azidoiodinane. Including imidazole or benzimidazole in the reaction mixture was found to significantly improve the yields of the post‐polymerization modification. Although chain cleavage was observed, the methodology afforded high‐molecular‐weight (<I>M</I><SUB>w</SUB> > 100 kDa) functionalized polypropylene containing up to 3 mol% of azido groups and enabled access to polypropylene‐<I>graft</I>‐poly(ethylene glycol) copolymers via azide–alkyne cycloaddition chemistry. © 2016 Society of Chemical Industry</P>
Ionic Liquid Crystals: Versatile Materials
Goossens, Karel,Lava, Kathleen,Bielawski, Christopher W.,Binnemans, Koen American Chemical Society 2016 Chemical reviews Vol.116 No.8
<P>This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the 'state-of-the-art' in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.</P>
Burgess Reagent Facilitated Alcohol Oxidations in DMSO
Sultane, Prakash R.,Bielawski, Christopher W. American Chemical Society 2017 Journal of organic chemistry Vol.82 No.2
<P>The Burgess reagent ([methoxycarbonylsulfamoyl]triethylammonium hydroxide) has historically found utility as a dehydrating agent. Herein we show that, in the presence of dimethyl sulfoxide, the Burgess reagent efficiently and rapidly facilitates the oxidation of a broad range of primary and secondary alcohols to their corresponding aldehydes and ketones in excellent yields and under mild conditions, and can be combined with other transformations (e.g., Wittig olefinations). A mechanism similar to those described for the Pfitzner-Moffatt and Swern oxidations is proposed.</P>
Metal-promoted C1 polymerizations
Cahoon, Collin R.,Bielawski, Christopher W. Elsevier 2018 Coordination chemistry reviews Vol.374 No.-
<P><B>Abstract</B></P> <P>C1 polymerizations provide a means to grow polymer chains one carbon atom at a time. Such methodology enables the synthesis of persubstituted polymers that are challenging to prepare using conventional C2 polymerizations, which typically utilize alkene-based monomers and thus grow polymer chains two carbons at a time. Persubstituted polymers feature higher densities of pendant functional groups and, as such, offer the potential to exhibit enhanced physical and/or chemical properties over their monosubstituted C2 polymer analogues. This review summarizes the various metals that have been used to promote C1 polymerizations in a catalytic or stoichiometric manner. Discussions are stratified according to the monomers used, which are formally carbenes or carbynes and typically employed as their respective ylides, isocyanides, diazo compounds, or geminal di- or trihalides. Emphasis is placed on the scope of the polymerization chemistry, underlying mechanisms, and outstanding opportunities in the field.</P> <P><B>Highlights</B></P> <P> <UL> <LI> C1 polymerizations offer access to highly substituted polymers. </LI> <LI> C1 polymers often exhibit unique properties due to the high densities of functional groups. </LI> <LI> Polymerizations of diazo compounds have been catalyzed by Cu, Au, Pd, and Rh. </LI> <LI> Polymerizations of isocyanides have been catalyzed by Ni, Co, Pd, and Rh. </LI> <LI> Polymerizations of geminal di- and trihalides have been promoted with Mg, Li, Zn, and Na/K. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>