Covalently Functionalized MXenes for Highly Sensitive Humidity Sensors.

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Transition metal carbides and nitrides (MXenes) are 2D materials with tunable properties due to surface functional groups.
• Covalent functionalization methods for MXenes are limited, with diazonium salt grafting and silylation being primary examples.
• Developing new functionalization strategies is crucial for expanding MXene applications.

Purpose of the Study:

• To report an unprecedented two-step covalent functionalization of Ti3C2Tx MXenes.
• To utilize functionalized MXenes for fabricating high-performance chemiresistive humidity sensors.
• To demonstrate the potential of these sensors for real-time monitoring.

Main Methods:

• A two-step functionalization process involving (3-aminopropyl)triethoxysilane tethering to Ti3C2Tx MXenes.
• Subsequent attachment of organic bromides via C-N bond formation.
• Fabrication and testing of thin films as chemiresistive humidity sensors.

Main Results:

• Functionalized Ti3C2Tx thin films exhibited increased hydrophilicity.
• The fabricated sensors demonstrated a broad operating range (0-100% RH) and high sensitivity.
• Devices showed fast response/recovery times and high selectivity for water vapor.

Conclusions:

• The developed two-step functionalization method enables advanced MXene material properties.
• The Ti3C2Tx-based humidity sensors surpass the state-of-the-art in operating range and sensitivity.
• These sensors are highly suitable for real-time humidity monitoring applications.