Fiber-optic microsensor for high resolution pCO2 sensing in marine environment

Area of Science:

• Environmental Science
• Analytical Chemistry
• Oceanography

Background:

• Accurate measurement of dissolved carbon dioxide (CO2) in marine sediments is crucial for understanding biogeochemical cycles.
• Existing microsensors often lack the required spatial resolution, sensitivity, or response time for in-situ marine sediment analysis.

Purpose of the Study:

• To develop and characterize a fast-responding fiber-optic microsensor for high-resolution pCO2 sensing in marine sediments.
• To achieve high sensitivity for detecting low dissolved CO2 levels typical in marine environments.

Main Methods:

• Fabrication of a fiber-optic microsensor with a tip diameter of 20-50 microm.
• Lipophilization of the pH-indicator 8-hydroxypyrene-1,3,6-trisulfonate with tetraoctylammonium [HPTS-(TOA)4] for matrix solubility.
• Application of a gas-permeable Teflon derivative coating to prevent ionic interferences.

Main Results:

• The microsensor demonstrated a detection limit of 0.04 hPa pCO2 (60 ppb dissolved CO2).
• Rapid response times of less than 1 minute were achieved.
• The sensor showed good performance regarding reproducibility, dynamic range, temperature behavior, and stability, with detailed analysis of hydrogen sulfide interference.

Conclusions:

• The developed fiber-optic microsensor provides a sensitive and rapid tool for high-resolution pCO2 measurements in marine sediments.
• The sensor design effectively mitigates common interferences, enhancing its applicability in complex marine environments.
• This technology facilitates improved understanding of carbon cycling and diagenetic processes in seafloor sediments.