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The arrangement of two-dimensional graphene oxide sheets has been shown to influence physico-chemical properties of the final bulk structures. In particular, various graphene oxide microfibers remain of high interest in electronic applications due to their wire-like thin shapes and the ease of hydrothermal fabrication. In this research, we induced the internal ordering of graphene oxide flakes during typical hydrothermal fabrication via doping with Calcium ions (~6 wt.%) from the capillaries. The Ca2+ ions allowed for better graphene oxide flake connections formation during the hydrogelation and further modified the magnetic and electric properties of structures compared to previously studied aerogels. Moreover, we observed the unique pseudo-porous fiber structure and flakes connections perpendicular to the long fiber axis. Pulsed electron paramagnetic resonance (EPR) and conductivity measurements confirmed the denser flake ordering compared to previously studied aerogels. These studies ultimately suggest that doping graphene oxide with Ca2+ (or other) ions during hydrothermal methods could be used to better control the internal architecture and thus tune the properties of the formed structures.
Krzysztof Tadyszak; Jacek K. Wychowaniec; Karol Załęski; Emerson Coy; Łukasz Majchrzycki; Raanan Carmieli. Tuning Properties of Partially Reduced Graphene Oxide Fibers upon Calcium Doping. Nanomaterials 2020, 10, 957 .
AMA StyleKrzysztof Tadyszak, Jacek K. Wychowaniec, Karol Załęski, Emerson Coy, Łukasz Majchrzycki, Raanan Carmieli. Tuning Properties of Partially Reduced Graphene Oxide Fibers upon Calcium Doping. Nanomaterials. 2020; 10 (5):957.
Chicago/Turabian StyleKrzysztof Tadyszak; Jacek K. Wychowaniec; Karol Załęski; Emerson Coy; Łukasz Majchrzycki; Raanan Carmieli. 2020. "Tuning Properties of Partially Reduced Graphene Oxide Fibers upon Calcium Doping." Nanomaterials 10, no. 5: 957.
A new and simple design of electrochemical setup for in‐situ generation of free radicals to be measured using X‐band (9.5 GHz) electron paramagnetic resonance (EPR) spectrometer is described. The cell parts are all from commercially available components and requires no specially made glassware. The EPR performance of the setup is demonstrated by in‐situ electrochemical generation of organic radical cations and radical anions such as quinones, perylene‐diimide, pyrene, flavin, tryptophan and tyrosine through oxidation or reduction in solution. The well‐resolved EPR spectra of the radical products were simulated and analyzed and the hyperfine coupling constants have been assigned for the interactions of the unpaired electron with the various ring protons and the nitrogen nuclei.
Maya Toybenshlak; Raanan Carmieli. A New and Robust Method for In‐situ EPR Electrochemistry. Israel Journal of Chemistry 2019, 59, 1020 -1026.
AMA StyleMaya Toybenshlak, Raanan Carmieli. A New and Robust Method for In‐situ EPR Electrochemistry. Israel Journal of Chemistry. 2019; 59 (11-12):1020-1026.
Chicago/Turabian StyleMaya Toybenshlak; Raanan Carmieli. 2019. "A New and Robust Method for In‐situ EPR Electrochemistry." Israel Journal of Chemistry 59, no. 11-12: 1020-1026.
The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol is an important research challenge. Mostly thermochemical approaches have been studied, but these still have various drawbacks. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates that are easily hydrolyzed by water yielding the corresponding phenols is presented. The formylation reaction occurs on a Pt anode in the presence of [Co(III)W12O40]5- as catalyst and Li formate as electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR. Hydrogen was formed at the Pt cathode. The sum transformation is ArH + H2O ArOH + H2. Non-optimized reaction conditions showed a Faradaic efficiency of 75 % and selective formation of the mono-oxidized product in a 35 % yield. Decomposition of formic acid to CO2 and H2 is the side-reaction. This electrocatalytic reaction may lead to new processes for arene hydroxylation.
Alexander M. Khenkin; Miriam Somekh; Raanan Carmieli; Ronny Neumann. Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom. Angewandte Chemie 2018, 130, 5501 -5505.
AMA StyleAlexander M. Khenkin, Miriam Somekh, Raanan Carmieli, Ronny Neumann. Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom. Angewandte Chemie. 2018; 130 (19):5501-5505.
Chicago/Turabian StyleAlexander M. Khenkin; Miriam Somekh; Raanan Carmieli; Ronny Neumann. 2018. "Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom." Angewandte Chemie 130, no. 19: 5501-5505.
The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol is an important research challenge. Mostly thermochemical approaches have been studied, but these still have various drawbacks. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates that are easily hydrolyzed by water yielding the corresponding phenols is presented. The formylation reaction occurs on a Pt anode in the presence of [Co(III)W12O40]5- as catalyst and Li formate as electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR. Hydrogen was formed at the Pt cathode. The sum transformation is ArH + H2O ArOH + H2. Non-optimized reaction conditions showed a Faradaic efficiency of 75 % and selective formation of the mono-oxidized product in a 35 % yield. Decomposition of formic acid to CO2 and H2 is the side-reaction. This electrocatalytic reaction may lead to new processes for arene hydroxylation.
Alexander M. Khenkin; Miriam Somekh; Raanan Carmieli; Ronny Neumann. Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom. Angewandte Chemie International Edition 2018, 57, 5403 -5407.
AMA StyleAlexander M. Khenkin, Miriam Somekh, Raanan Carmieli, Ronny Neumann. Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom. Angewandte Chemie International Edition. 2018; 57 (19):5403-5407.
Chicago/Turabian StyleAlexander M. Khenkin; Miriam Somekh; Raanan Carmieli; Ronny Neumann. 2018. "Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom." Angewandte Chemie International Edition 57, no. 19: 5403-5407.