Energy-Level Alignment at TiO₂@NH₂-MIL-125 Interface for High-Performance Gas Sensing

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Metal oxide (MO)-based chemiresistive sensors face challenges of high working temperatures and poor selectivity due to their thermally activated sensing mechanisms.
• Metal-organic frameworks (MOFs) offer tunable structures for precise modulation of MO heterojunction interfaces, potentially overcoming these limitations.

Purpose of the Study:

• To engineer MO@MOF heterojunctions for optimized chemiresistive gas sensing performance.
• To investigate the effect of energy band structure modulation on sensor properties.

Main Methods:

• Fabrication of TiO2@MOF heterojunctions with varying -NH2 functionalization (x=0, 1, 2) on MIL-125.
• Modulation of the interfacial band structure from straddling gap to staggered gap via -NH2 functionalization.
• Evaluation of gas-sensing properties, including sensitivity, selectivity, response time, and stability at room temperature.

Main Results:

• The TiO2@NH2-MIL-125 heterojunction exhibited a modulated band structure, enabling light-activated sensing.
• Achieved highly sensitive detection of NO2 at 1 ppb with a rapid response time (<0.3 min) at room temperature.
• Demonstrated excellent selectivity and long-term stability for NO2 detection.

Conclusions:

• Energy band engineering of MO@MOF heterojunctions is a viable strategy to enhance chemiresistive sensor performance.
• TiO2@NH2-MIL-125 represents a breakthrough in room-temperature, light-activated gas sensing.
• This approach offers a pathway to overcome limitations in current sensor materials for environmental and diagnostic applications.