Environmental monitoring through gas sensors is paramount for the safety and security of industrial workers and for ecological protection. Graphene is among the most promising materials considered for next-generation gas sensing due to its properties such as mechanical strength and flexibility, high surface-to-volume ratio, large conductivity, and low electrical noise. While gas sensors based on graphene devices have already demonstrated high sensitivity, one of the most important figures of merit, selectivity, remains a challenge. In the past few years, however, surface functionalization emerged as a potential route to achieve selectivity. This review surveys the recent advances in the fabrication and characterization of graphene and reduced graphene oxide gas sensors chemically functionalized with aromatic molecules and polymers with the goal of improving selectivity toward specific gases as well as overall sensor performance.

This work reports the facile preparation of single-walled carbon nanotubes (SWCNTs) noncovalently functionalized with 3d transition metal (II) phthalocyanines MPcs (M=Mn, Fe, Co and Ni) and their electrochemical evaluation towards the oxygen evolution reaction (OER) in alkaline media. The modification of SWCNTs with MPcs improved the potential required for the oxygen evolution reaction in 0.1 M and 1 M KOH by lowering the potential by approximately 120 mV in comparison with unmodified SWCNTs, at a current density of 10 mA cm À 1 . The onset potential of the hybrids is close to the bulk Ni electrode in 1 M KOH and significantly outperforms Ni and Ir black electrodes in 0.1 M KOH solution. Nickel, cobalt and iron phthalocyanines showed auto-activation during extended cyclic voltammetry and long-term chronoamperometric measurements in both KOH concentrations. The excellent electrocatalytic activity of hybrids obtained and the straightforward method of their synthesis opens the possibility of exploring the proposed materials for applications in anion exchange membrane water electrolysis (AEMWE).

Solvent-free functionalization of graphene oxide paper with amines is facile, nondestructive, and attractive from economic and environmental points of view.

† Electronic supplementary information available: Comparison of FTIR spectra for GO before and after treatment with NH 4 OH solution of pH 12 without Ni(II) tetraazamacrocyclic complexes (control experiment); Raman and EPR spectra for GO, GO+[Ni(cyclam)] and GO+[Ni(tet b)]; XPS spectra (survey and deconvolution for C 1s and O 1s) of GO before functionalization; the data of magnetic susceptibility measurements; total energies calculated by DFT for GO model, macrocyclic dications [Ni(cyclam)] 2+ and [Ni(tet b)] 2+ , and the high-spin complexes GO+[Ni(cyclam)] and GO+[Ni(tet b)].

Solvent-free covalent functionalization of graphene oxide and nanodiamond with amines was performed in one step at 150–180 °C.