Analysis of competitive binding of several metal cations by graphene oxide reveals the quantity and spatial distribution of carboxyl groups on its surface

Abstract

The sorption capacity of graphene oxide (GO) toward different metal cations has been the subject of several recent studies. However, the reported quantitative data are controversial, and the mechanism of chemical bonding between GO and metal cations is poorly understood. Clarifying these questions can eventually help to reveal the fine chemical structure of GO that remains ambiguous. In this work, we study the binding of Gd and Mn by GO in the presence of several competing metal cations by the H NMR relaxation method. As a general trend, the efficiency of the metal cations to bind to GO increases with ionic charge, and depends on their ability to form coordinate-covalent bonds with GO oxygen groups. The efficiency of the competing metal cations to "replace" Gd and Mn increases in the order Na < Cs < Ca < Sr < Ga < Lu. GO contains two different types of binding sites, bonding to which results in either high or low NMR relaxivity of the resulting Gd-GO and Mn-GO solutions. Gd and Mn, being replaced from the high-relaxivity sites by the large excess of competing cations, are not released into the bulk solution, but only migrate to the low-relaxivity sites, remaining covalently bonded to GO. The absolute majority of the existing carboxyl groups in GO are located at tiny few-carbon-atom-vacancy defects on the major planes. The density of these vacancy defects is estimated as one per every 200 carbon atoms.

New insights into the mechanism of graphene oxide and radionuclide interaction

“…Therefore, it is unlikely that most of the actinides are sorbed by sulfate groups present in the GO. The sorption mechanism related to interaction with sulfur groups was proposed previously in several works [33,[61][62][63].…”

Single Co‐Atoms as Electrocatalysts for Efficient Hydrazine Oxidation Reaction

“…Surface-functionalized graphene derivatives, in particular, can render strong interactions with the single atoms, and thereby stabilize SACs and prevent their aggregation and transformation into nanoparticles during catalytic reactions. [17,[19][20][21][22][23][24][25][26][27] To this end, herein we present a novel approach to anchor single Co(II) ions on cyanographene (GCN) sheets to obtain Co-based single atom catalysts (G(CN)Co SACs). The synthetic process is schematically described in Scheme 1.…”

“…Surface‐functionalized graphene derivatives, in particular, can render strong interactions with the single atoms, and thereby stabilize SACs and prevent their aggregation and transformation into nanoparticles during catalytic reactions. [ 17,19–27 ]…”

Metal Cation‐Modified Graphene Oxide as Precursor for Advanced Materials: Thin Films of Graphene/Prussian Blue Analogues

“…The metallic species into the modified films is demonstrated to be effective reactants to produce PB(A) through a heterogeneous electrochemical reaction with [Fe(CN) 6 ] 3À , yielding graphene/ PB(A) nanocomposite thin films. Several recent works have been published dealing with the incorporation of different metal cations into GO structure, [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] through different adsorption processes or ion-exchange reactions, aiming ion-exchange membranes, [51,52] materials for water purification [53,54] and desalinization processes. [55,56] For example, Klimová et al [57] conducted a study of sorption of different ions on the graphene oxide, showing high sorption capacity, mainly due to the metal coordination with ketone and carboxylic acid groups; Dimiev et al [58][59][60][61] use the NMR relaxation technique to monitor reactions between aqueous dispersed GO and different transition metal cations, demonstrating both covalent and electrostatic interactions, directly dependent on several factors such as the concentration of GO and metals; the pH; the chemical nature of the metals; the ionic charge of cations.…”