Synthesis of oxygen-doped graphitic carbon nitride and its application for the degradation of organic pollutants via dark Fenton-like reactions

Exploiting the Electrostatic Binding of Ruthenium Hexamine Molecular Redox Nanowires onto DNA/OGCN Biohybrid Electrodes toward the Electrochemical Detection of COVID-19

The Coronavirus Disease 2019 (COVID-19) recently emerged as a life-threatening global pandemic that has ravaged millions of lives. The affected patients are known to frequently register numerous comorbidities induced by COVID-19 such as diabetes, asthma, cardiac arrest, hypertension, and neurodegenerative diseases, to name a few. The expensiveness and probability of false negative results of conventional screening tests often delay timely diagnosis and treatment. In such cases, the deployment of a suitable biosensing platform can readily expedite the rapid diagnosis process for enhanced patient outcomes. We report the development of an electrochemical genosensor based on DNA/OGCN (DNA/oxygenated graphitic carbon nitride) nanohybrids for the quantification of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) DNA─the key biomarker for COVID-19. This is achieved by exploiting the molecular nanowire-formation capability of the [Ru(NH3)6]2+/3+ redox probe onto the DNA phosphate backbone via electrostatic interactions. The microstructural characterization of OGCN was performed using scanning electron microscopy (SEM) coupled with an energy-dispersive X-ray (EDX) module, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. The electrochemical analyses were performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), while the analytical performance of the sensor was evaluated using square wave voltammetry (SWV). The developed sensor exhibited a wide linear detection range within 10 fM-10 μM, with a limit of detection (LoD) of ∼7.23 fM with a high degree of selectivity toward SARS-CoV-2 target DNA, thereby indicating its potential to be employed in a point-of-care scenario toward providing affordable healthcare to the global populace.

Dual-Mechanism Study of Metal-Free g-C3N4 Catalysts for Advanced Oxidation Under Non-Photocatalytic Conditions

Metal-free materials have been proved to be promising replacements of traditional metal-based catalysts for advanced oxidation reactions. Carbon nitride was found to be able to activate H2O2 and generate hydroxyl radicals (•OH). Nevertheless, the performance of carbon nitride is highly dependent on an external light source. In this work, we report a light-independent, metal-free catalyst based on g-C3N4 prepared using a facile calcination method. It is revealed that two reaction pathways, a radical (•OH) one and a nonradical (H2O2) one, coexist in organics oxidation on g-C3N4. The dominant reaction pathway is dependent on the condensation temperature of UCN. In addition, this g-C3N4 exhibited excellent stability after being recycled and reused for five cycles. The findings in this work can be used for the design of efficient and robust metal-free catalysts with both superior catalytic performance and high stability for various heterogeneous catalytic processes.

Enhanced Photocatalytic Properties of All-Organic IDT-COOH/O-CN S-Scheme Heterojunctions Through π-π Interaction and Internal Electric Field

Herein, we present a distinct methodology for the in situ electrostatic assembly method for synthesizing a conjugated (IDT-COOH)/oxygen-doped g-C3N4 (O-CN) S-scheme heterojunction. The electron delocalization effect due to π-π interactions between O-CN and self-assembled IDT-COOH favors interfacial charge separation. The self-assembled IDT-COOH/O-CN exhibits a broadened visible absorption to generate more charge carriers. The internal electric field between the IDT-COOH and the O-CN interface provides a directional charge-transfer channel to increase the utilization of photoinduced charge carriers. Moreover, the active species (•O2-, h+, and 1O2) produced by IDT-COOH/O-CN under visible light play important roles in photocatalytic disinfection. The optimum 40% IDT-COOH/O-CN can kill 7-log of methicillin-resistant Staphylococcus aureus (MRSA) cells in 2 h and remove 88% tetracycline (TC) in 5 h, while O-CN only inactivates 1-log of MRSA cells and degrades 40% TC. This work contributes to a promising method to fabricate all-organic g-C3N4-based S-scheme heterojunction photocatalysts with a wide range of optical responses and enhanced exciton dissociation.

Oxygen doped graphitic carbon nitride nanosheets for the degradation of organic pollutants by activating hydrogen peroxide in the presence of bicarbonate in the dark

The development of novel wastewater treatment processes that use heterogeneous catalysts to activate hydrogen peroxide (H2O2) with bicarbonate (HCO3 -) has been a subject of great interest in recent years; however, significant challenges remain, despite research into numerous metal-based catalysts. The work presented herein employed oxygen-doped graphitic carbon nitride (O/g-C3N4) as a non-metal catalyst for activating H2O2 in the presence of HCO3 -, and this method represented the first system capable of removing organic pollutants in the dark, to our knowledge. The catalysts were characterized using several microscopic imaging, spectroscopic, electrochemical, and crystallographic techniques, as well as N2-physorption procedures. Analysis of the results revealed that the O/g-C3N4 catalyst possessed a high specific surface area and many defect sites. Various operational parameters, including the relative amounts of HCO3 -, H2O2, and O/g-C3N4, were systemically investigated. A clear performance enhancement was observed in the degradation of organic contaminants when subjected to the HCO3 --H2O2-O/g-C3N4 system, and this result was ascribed to the synchronous adsorption and chemical oxidation processes. The novel system presented herein represented a new water treatment technology that was effective for removing organic contaminants.