g-C₃N₄/CoN₄ heterojunction as a sensor for detecting volatile organic compounds: a density functional study

Area of Science:

• Materials Science
• Computational Chemistry
• Chemical Sensing

Background:

• Exhaled breath analysis is crucial for non-invasive disease diagnosis.
• Developing sensitive and selective gas sensors is essential for detecting volatile organic compounds (VOCs) in breath.
• Graphitic carbon nitride (g-C3N4) based materials are explored for gas sensing applications.

Purpose of the Study:

• To investigate the adsorption behavior of key exhaled breath biomarkers on pristine g-C3N4 and g-C3N4/CoN4 composite surfaces using DFT calculations.
• To understand the interaction mechanisms between gas molecules and sensor surfaces by analyzing adsorption energy, electronic properties, and charge distribution.
• To evaluate the potential of g-C3N4/CoN4 as a material for reusable gas sensors for biomarker detection.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Adsorption energies, electronic density of states (DOS), band structures, charge density difference, conductivity, and work function were analyzed.
• The adsorption of benzene, toluene, aniline, and o-toluidine on g-C3N4 and g-C3N4/CoN4 surfaces was simulated.

Main Results:

• The g-C3N4/CoN4 composite significantly enhanced the chemical reactivity and stability of g-C3N4, improving gas adsorption.
• Benzene, toluene, and aniline exhibited reversible adsorption on g-C3N4/CoN4, indicating suitability for reusable sensors.
• O-toluidine showed irreversible binding, potentially limiting its reusability.
• Aniline demonstrated the strongest interaction with g-C3N4/CoN4, showing the lowest band gap, highest conductivity, and highest sensitivity.
• Band structure analysis confirmed improved electrical conductivity of the composite upon aniline adsorption, even at room temperature.

Conclusions:

• The g-C3N4/CoN4 composite is a promising material for developing selective and sensitive gas sensors for exhaled breath biomarkers.
• The material exhibits enhanced adsorption properties and electrical conductivity, particularly for aniline detection.
• Theoretical findings provide guidelines for experimental validation of g-C3N4/CoN4 for VOC sensing in breath analysis.