How are Hydroxyl Groups Localized on a Graphene Sheet?

Abstract

Arrangements of hydroxyl groups on graphene sheets were systematically investigated using density functional theory calculations that included van der Waals interactions. Results show that hydroxyl groups tend to gather at para-positions on graphene sheets to generate perfect ring-like hexahydroxyl group adsorption. The close proximity of hydroxyl groups is in good agreement with the experimental separation between unoxidized, aromatic and oxidized, saturated regions in graphene oxide. The orientation of hydrogen atoms in hydroxyl groups creates both O–H···O and O–H···π hydrogen bonds. Calculations also indicated that the binding energy per hydroxyl group follows a logarithmic function with respect to the number of hydroxyl groups. Besides, the opening band gap was observed for several derivatives, and the relationship between the band gap and O/C ratio was found to be nonmonotonic. Analysis of the density of states showed that bands around the Fermi levels of derivatives between graphene and hydroxyl groups are mainly composed of 2p z orbitals of carbon and oxygen atoms.

Graphene Oxide‐BODIPY Conjugates as Highly Fluorescent Materials

“…Such conclusions are based both on the geometry of the diol defects in GO and the structure of the phenylboronic ester. [38][39][40] This arrangement avoids strong electronic communications between them in the ground state, in contrast to what is observed in the case of GO-NH-BODIPY. In the latter, the flexible spacer allows π-π stacking of BODIPY onto the GO surface, leading to broadened and redshifted absorptions (Figure 2b).…”

“…This observation is attributed to the phenylboronic ester that connects GO with BODIPY, which is likely to result in a rigid perpendicular arrangement of BODIPY with respect to the GO surface. Such conclusions are based both on the geometry of the diol defects in GO and the structure of the phenylboronic ester [38–40] . This arrangement avoids strong electronic communications between them in the ground state, in contrast to what is observed in the case of GO‐NH‐BODIPY.…”

Unravelling the sensing efficacy of graphene oxide towards hazardous volatile organic compounds in the polyurethane industry

“…2a) with a band gap of 1.71 eV. 42 The formation energy of the stable, hexa-ring-hydroxyl GO slab was computed to be À0.622 eV. The introduction of the hydroxyl groups resulted in distortion of the planarity of GO, seen in Fig.…”

“…Tran et al explored this prospect computationally and carried out an indepth analysis. 42 GO slabs with variations in the number of hydroxyl groups between one and six were investigated and their formation energies and structural orientations were evaluated. With a formation energy of À10.92 eV, the hexa-ring-oriented hydroxyl system displayed higher stability, mainly attributed to the formation of O-HÁ Á ÁO and O-HÁ Á Áp hydrogen bonds.…”

“…With a formation energy of À10.92 eV, the hexa-ring-oriented hydroxyl system displayed higher stability, mainly attributed to the formation of O-HÁ Á ÁO and O-HÁ Á Áp hydrogen bonds. 42 Corroborating from this inference, it seemed reasonable to employ a ring-like hexahydroxyl-based GO slab to evaluate the adsorption efficacy of chlorine-based VOCs. To the best of our knowledge, limited reports are available on the adsorption of these hazardous VOCs on hydroxyl-enriched GO that attracted our attention to explore the sensitivity of GO towards the detection of PhG and its hazardous by-products.…”