Auf dem Weg zu Graphan – ausgeprägte Fluoreszenz von polyhydriertem Graphen

Abstract

Chemie trifft Graphan: Gefrorenes Wasser als sanfte Protonenquelle führt in einer Birch‐Reaktionssequenz zur Exfolierung von Graphit und zur Bildung von polyhydriertem Graphen mit elektronisch entkoppelten π‐Nanodomänen. Man beobachtet eine ausgeprägte Fluoreszenz dieses hoch funktionalisierten Graphens.

Highly Hydrogenated Graphene through Microwave Exfoliation of Graphite Oxide in Hydrogen Plasma: Towards Electrochemical Applications

“…[29] In the case of FTIR spectroscopy, two peaks are observed at about 2850-2950 cm À1 in all three samples of hydrogenated graphenes ( Figure S2 in the Supporting Information). These double bands correspond to alkyl CÀH stretches [2,[30][31][32] and therefore confirm that the microwave hydrogen plasma had resulted in the formation of C À H bonds within the carbon backbone. Other bands include a weak and broad absorption from 3300 to 3500 cm À1 arising from the O À H vibrations of hydroxyls and carboxyls, and a small peak approximately at 1100 cm À1 , due to CÀO stretches of alcohols and aromatic acids ( Figure S3 in the Supporting Information).…”

“…Graphane and hydrogenated graphenes collectively form a group of materials that have a variety of important uses in devices and applications, exhibiting interesting properties, such as a tunable band gap, [1] fluorescence, [2] ferromagnetism, [3] and the possibility to reversibly store hydrogen. [2] Much conceptual effort has been dedicated to produce graphane from the hydrogenation of graphene, using approaches that vary from gas-phase hydrogenation techniques to wet chemistry methods. [4] Although pure graphane still remains an intangible goal, partial hydrogenation of graphene (which we herein refer to as hydrogenated graphene) is an interesting subject on its own, because some properties may be potentially controllable by tuning the degree of hydrogenation.…”

Hydrogenated Graphenes by Birch Reduction: Influence of Electron and Proton Sources on Hydrogenation Efficiency, Magnetism, and Electrochemistry

“…[25] Nonetheless, our primary interest is in the CÀHs tretches at 2850 and 2950 cm À1 ,t he presence of which effectively confirms successfulh ydrogenation of the sp 2 -carbon backbone. [4,6,8,15] The twinning of CÀHs tretching bondsi ndicates ah igh concentration of terminal hydrogenatedc arbon atoms at which CH 2 or even some CH 3 functional groups can be formed. This is ob- served only on samples with the highest degrees of hydrogenation and may furtheri ndicateh igher density of defects.…”

“…Graphenes and chemically modified graphenes are practically ubiquitous in the chemistry literature today,a rguably because of the sp 2 -carbon structure, which evokes many familiarr eactions from traditional synthetic chemistry.Awide range of covalent functionalisation reactionsh ave been attained for numerous purposes, including functionalisation with hydrogen. [1][2][3] Hydrogenated graphenes have demonstrated am yriad of interesting properties, such as fluorescence [4] andf erromagnetism, [5,6] and valuable applicationsi nd evices, including lithium batteries [7] and also for the reversible storageo fh ydrogen. [8] Overall, two approaches to graphene hydrogenation exist, [9] with liquid-phase (wet chemistry) hydrogenation generally provingm ore effective than gaseous procedures that employ hydrogen plasmas [10,11] or high temperature and pressure.…”

“…[12,13] Since ar eport in 2001, numerousg roups have applied the venerated Birch reduction [14] on carbon materials, firstly with graphite and carbon nanotubes, to later attempts with graphite oxides (GOs) intended towards the production of reduced graphenes and hydrogenated graphenes. [4,[6][7][8][15][16][17] In the case of simple molecules, such as benzene, hydrogenation is achieved on carbons at the 1a nd 4p ositions by using as olution of solvated electrons obtained by dissolvinga lkali metals( typically Li or Na) in liquid NH 3 ,f ollowed by their protonation with alcohols. In thec ase of large aromatic systems, such as graphene, however,h ydrogenation occurs to am uch highere xtent due to greater electron delocalisation.…”