Optical sensor for carbon dioxide gas determination, characterization and improvements

Area of Science:

• Analytical Chemistry
• Materials Science

Background:

• Traditional CO2 sensors using luminophore-based membranes suffer from reduced efficiency and require specific atmospheric conditions.
• The use of tetraoctyl ammonium hydroxide (TOAOH) as a phase transfer agent leads to degradation and loss of sensor performance over time.

Purpose of the Study:

• To investigate alternative materials and methods for improving the stability and operational lifetime of gaseous CO2 sensors.
• To address the drawbacks of existing luminiscence-based CO2 sensors, specifically their efficiency loss and stringent environmental requirements.

Main Methods:

• Characterization of various sensing membranes for gaseous CO2 determination.
• Testing alternative phase transfer agents to TOAOH, focusing on those resistant to Hoffman degradation.
• Evaluating the use of hydrophilic polymers versus hydrophobic polymers for CO2 sensing membranes.

Main Results:

• Replacing TOAOH with tetramethyl ammonium (TMAOH) significantly improved sensor stability and sensitivity.
• Hydrophilic polymers enhanced sensor response time and stability compared to hydrophobic alternatives.
• Optimized membranes demonstrated a detection limit of 0.006%, with a response time of 19s and recovery time of 100s.

Conclusions:

• Tetramethyl ammonium (TMAOH) and hydrophilic polymers are effective in creating more stable and longer-lasting CO2 sensors.
• The developed sensors exhibit extended lifetimes (over 300-515 days) and do not require special atmospheric conditions beyond darkness.
• These advancements offer a promising solution for reliable and durable gaseous CO2 monitoring.