Electrochemical Fluorographane: Hybrid Electrocatalysis of Biomarkers, Hydrogen Evolution, and Oxygen Reduction

Sensitive Electrochemical Detection of Caffeic Acid in Wine Based on Fluorine-Doped Graphene Oxide

We report here a novel electrochemical sensor developed using fluorine-doped graphene oxide (F-GO) for the detection of caffeic acid (CA). The synthesized graphene oxide (GO) and F-GO nanomaterials were systematically characterized with a scanning electron microscope (SEM), and the presence of semi-ionic bonds was confirmed in the F-GO using X-ray photoelectron spectroscopy. The electrochemical behaviours of bare glassy carbon electrode (GCE), F-GO/GCE, and GO/GCE toward the oxidation of CA were studied using cyclic voltammetry (CV), and the results obtained from the CV investigation revealed that F-GO/GCE exhibited the highest electrochemically active surface area and electrocatalytic activity in contrast to the other electrodes. Differential pulse voltammetry (DPV) was employed for the analytical quantitation of CA, and the F-GO/GCE produced a stable oxidation signal over the selected CA concentration range (0.5 to 100.0 μM) with a low limit of detection of 0.018 μM. Furthermore, the acquired results from the selectivity studies revealed a strong anti-interference capability of the F-GO/GCE in the presence of other hydroxycinnamic acids and ascorbic acid. Moreover, the F-GO/GCE offered a good sensitivity, long-term stability, and an excellent reproducibility. The practical application of the electrochemical F-GO sensor was verified using various brands of commercially available wine. The developed electrochemical sensor successfully displayed its ability to directly detect CA in wine samples without pretreatment, making it a promising candidate for food and beverage quality control.

Origin of the catalytic activity of phosphorus doped MoS2 for oxygen reduction reaction (ORR) in alkaline solution: a theoretical study

Phosphorus doped MoS₂ nanosheets (P-doped MoS₂) have been reported as excellent oxygen reduction reaction (ORR) catalysts with four-electron selectivity in alkaline solution. By performing density functional theory (DFT) calculations, we revealed the detailed reaction mechanism and the key reaction sites on surface of P-doped MoS₂ for ORR catalysis. The double P-doped MoS₂ (2P-MoS₂) is calculated to be more stable than the single P-doped MoS₂ (P-MoS₂), and the configuration with two P atoms in neighboring sites exhibits the highest stability. The surface of P-doped MoS₂ is found highly active for dissociation of O₂. Comparative calculations reveal that P-MoS₂ is unsuitable as ORR catalyst due to the high dissociation barrier of H₂O (1.19 and 2.06 eV for the first and second adsorbed H₂O), while the 2P-MoS₂ shows good ORR catalytic activity with much lower dissociation barrier of H₂O (0.62 eV). Furthermore, we elucidated that the ORR catalytic activity in 2P-MoS₂ originates from the activated S2 atom, which provides an extra adsorption site for the first H₂O and the following OH group benefited from the enhanced hydrogen bond interaction. Our results illustrate the mechanisms of doped MoS₂ based catalysts and provide rational way for designing ORR catalysts with high activity.

Towards stoichiometric analogues of graphene: graphane, fluorographene, graphol, graphene acid and others

Stoichiometric derivatives of graphene, having well-defined chemical structure and well-defined chemical bonds, are of a great interest to the 2D materials research.