Study on a quartz crystal microbalance sensor based on chitosan-functionalized mesoporous silica for humidity...

Area of Science:

• Materials Science
• Sensor Technology
• Nanotechnology

Background:

• Chitosan exhibits good film-forming properties but is prone to swelling in humid conditions, affecting sensor performance.
• Mesoporous silica MCM-41 offers a stable porous structure but lacks inherent sensitivity for certain applications.
• Quartz crystal microbalance (QCM) sensors are sensitive to mass changes, making them suitable for humidity detection.

Purpose of the Study:

• To develop a chitosan-functionalized mesoporous silica MCM-41 (Chi/M41) composite material.
• To enhance the sensitivity, reliability, and stability of QCM humidity sensors.
• To investigate the water molecule adsorption mechanism on the composite sensitive films.

Main Methods:

• Mild preparation method for chitosan-functionalized mesoporous silica MCM-41 (Chi/M41) composite.
• Fabrication of QCM sensors utilizing the Chi/M41 composite as the sensitive layer.
• Characterization of sensor performance, including sensitivity, humidity hysteresis, variation coefficient, response/recovery times, and long-term stability.
• Application of Langmuir adsorption isotherm model and Gibbs free energy calculations to study adsorption mechanisms.

Main Results:

• The Chi/M41 composite effectively mitigated chitosan swelling, improving sensor repeatability and reliability at high relative humidity (RH).
• The composite structure significantly enhanced sensor sensitivity compared to pure chitosan or MCM-41.
• The optimal Chi/M41 QCM sensor demonstrated excellent sensitivity (58.4 ± 0.3 Hz/% RH), negligible humidity hysteresis (0.8 ± 0.1% RH), a small variation coefficient (1.1 ± 0.1), and rapid response/recovery times (18 s/15 s).
• The sensor exhibited good long-term stability.

Conclusions:

• Chitosan-functionalized MCM-41 is a promising composite material for developing high-performance QCM humidity sensors.
• The composite structure provides a synergistic effect, enhancing both sensitivity and reliability.
• The study provides insights into the water adsorption mechanism on these novel sensitive films.