On Oxygen‐Containing Groups in Chemically Modified Graphenes

Abstract

Reduced graphenes (belonging to the class of chemically modified graphenes, CMG) are one of the most investigated and utilized materials in current research. Oxygen functionalities on the CMG surfaces have dramatic influences on material properties. Interestingly, these functionalities are rarely comprehensively characterized. Herein, the four most commonly used CMGs, mainly electrochemically reduced graphene oxide (ER-GO), thermally reduced graphene oxide (TR-GO), and the corresponding starting materials, that is, graphene oxide and graphite oxide, were comprehensively characterized by a wide variety of methods, such as high-resolution X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, UV/Vis spectroscopy, transmission electron microscopy (TEM), and voltammetry, to establish connections between the structures of these materials that carry different oxygen functionalities and their electrochemical behaviors. This was followed by the quantification of the negatively charged oxygen-containing groups (OCGs) by UV/Vis spectroscopy and of the electrochemically reducible OCGs by voltammetry. Lastly, a biofunctionalization with gold nanoparticle (AuNP)-modified DNA sequences was performed by the formation of covalent bonds with the carboxylic groups (-COOH) on the CMG surfaces. There was an evident predominance of functionalizable -COOH groups on the ER-GO surface, as confirmed by a higher amount of Au detected both with differential-pulse voltammetry and impedance spectroscopy, coupled with visualization by TEM. We exploited the DNA-Au bioconjugates as highly specific stains to localize and visualize the positions of carboxylic groups. Our findings are very important to clearly identify the presence, nature, and distribution of oxygen functionalities on different chemically modified graphenes.

All‐in‐One: Electroactive Nanocarbon as Simultaneous Platform and Label for Single‐Step Biosensing

“…Metal nanoparticles, semiconductor quantum dots,a nd 2D layered nanomaterials have been employed as electroactive labels in ac ost-effective and more promising alternative to optical detection. [11][12][13] The presence of electrochemically reducible oxygen groups is particularly useful,a st hey generate intrinsic electrochemical signals that can be exploited for biosensing applications. Electroactive carbon nanomaterials such as nano-graphene oxide have shown great promise as electrochemicall abels for the detection of biomolecules.…”

Induced Helical Chirality of Perylenebisimide Aggregates Allows for Enantiopurity Determination and Differentiation of α‐Hydroxy Carboxylates by Using Circular Dichroism

“…In the case of both electrochemically and chemically reduced CMGs, this can be explained by the larger electroactive surface area and better electrical conductivity of reduced graphenes compared to the bare GC electrode 8. On the other end, the lower peak current obtained on GO‐modified electrode can be attributed to the larger concentration of oxygen functionalities present on the GO surface, which makes the material poorly conductive and has a detrimental effect on the electron‐transfer kinetics 25. In fact, at pH>4, both gallic acid and the graphene surface are negatively charged due to the deprotonation of carboxylic groups, and this in turn can contribute to the weakening of the π–π interaction network between the electrochemical platform and the analyzed probe, thus resulting in a lower electrochemical signal 26.…”

A Reduced Graphene Oxide‐based Electrochemical DNA Biosensor for the Detection of Interaction between Cisplatin and DNA based on Guanine and Adenine Oxidation Signals

“…Electrochemically reduced graphene oxide electrode (ERGO/GCE) : The GO/GCE was electrochemically reduced in 1 M KCl solution (previously deaerated by bubbling N 2 ) by cycling in the potential range from 0.0 to −1.2 V at the scan rate of 50 mV s −1 for 20 cycles . The reduction of epoxide, aldehyde and peroxide functionalities are expected to occur at this potential but not the carboxyl groups . The electrode was rinsed with water and dried in air at room temperature.…”