Modulation of the exfoliated graphene work function through cycloaddition of nitrile imines

Abstract

After the feasibility of the 1,3-dipolar cycloaddition reaction between nitrile imines and exfoliated graphene by density functional theory calculations was proved, very few-layer graphene was effectively functionalized using this procedure. Hydrazones with different electronic properties were used as precursors for the 1,3-dipoles, and microwave irradiation as an energy source enabled the reaction to be performed in a few minutes. The anchoring of organic addends on the graphene surface was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis.Ultraviolet photoelectron spectroscopy (UPS) was used to measure the work function and band gap of these new hybrids. Our results demonstrate that it is possible to modulate these important electronic valence band parameters by tailoring the electron richness of the organic addends and/or the degree of functionalization.

Cycloaddition of Nitrile Oxides to Graphene: a Theoretical and Experimental Approach

“…The covalent functionalization of graphene through [3+2] cycloaddition chemistry has been described in the literature only through the generation of azomethine ylide or nitrile imine intermediates, affording the corresponding pyrrolidine and pyrazoline derivatives, respectively. However, the cycloaddition of other dipoles to the graphene sheets, such as nitrile oxides, has neither been described theoretically nor experimentally.…”

“…Cycloaddition chemistry allowsa ne xcellent control of the functionalization degree and the introduction of aw ide variety of functional groups to carbonn anostructures (fullerenes, CNTsa nd graphene). [6,12,13] Among them, the 1,3-dipolar cycloaddition reactiono fa zomethine ylides affording fulleropyrrolidines is the most popular; [14,15] however,o ther [3+ +2] dipolar cycloadditions,s uch as those involving nitrile imines [16][17][18] as dipoles, have also been described in the literature.…”

“…Moreover,t he electronic properties of the carbon nanostructures (fullereneorCNTs) attached to the isoxazolinering are different than those of other fullerene derivatives as fulleropyrrolidines; in fact, the reduction potential of the fullerene cage in fulleroisoxazolines is similart ot hat of pristine C 60 but around 150 mV higher in fulleropyrrolidines. [19] The covalent functionalization of graphene through [3+ +2] cycloaddition chemistry has been described in the literature only through the generation of azomethine ylide [30] or nitrile imine [18] intermediates,a ffording the correspondingp yrrolidine and pyrazoline derivatives, respectively.H owever,t he cycload- dition of other dipoles to the graphene sheets,s uch as nitrile oxides, has neither been described theoretically nor experimentally.…”

Covalently Modified Graphenes in Catalysis, Electrocatalysis and Photoresponsive Materials

“…Scheme summarizes some of the strategies employed for covalent functionalization of Gs for their subsequent application as (photo‐ or electro)catalysts or for optoelectronic devices. Recently, band gap modulation of exfoliated G through 1,3‐dipolar cycloaddition reaction with nitrile amines has been also reported (Scheme ) . Similarly, benzylamine exfoliated G has been covalently functionalized using microwave‐assisted Bingel reaction with cyclopropanated malonate units bearing electro‐active tetrathiafulvalene moiety .…”

“…[84] Sonication-assisted exfoliation of Gi ns olvents avoids the creation of defects on the p-extended Go rbitala nd, therefore, minimizes alteration in the intrinsic mechanical, optical and electrical properties of G. [13,85] Then, the exfoliated Gs heets can be functionalized applying similar organic reactions to those already used for CNT or fullerenef unctionalization such as 1,3-dipolar cycloadditionso rd iazonium decomposition leadingt oa ddition to sp 2 carbons of G. [66] Scheme 3s ummarizes some of the strategies employed for covalent functionalization of Gs for their subsequenta pplication as (photo-or electro)catalysts or for optoelectronic devices.R ecently,b and gap modulation of exfoliated Gt hrough 1,3-dipolar cycloaddition reactionw ith nitrile amines has been also reported (Scheme 3). [86] Similarly, benzylamine exfoliated Gh as been covalently functionalized using microwave-assisted Bingel reactionw ith cyclopropanated malonate units bearinge lectro-active tetrathiafulvalene moiety. [84] Other examples on the use of covalently modified Gs with active molecules andt heir applicationf or photoinduced electron/energy transfer process are based on the use of GO as starting material via amidation, [87][88][89][90][91][92][93][94] sulfonamidation, [95] as well as esterification.…”