Development of a durable fiber-optic oxygen sensor for harsh underground environments

Area of Science:

• Materials Science
• Chemical Sensors
• Environmental Monitoring

Background:

• Fiber-optic oxygen sensors are vital for environmental monitoring.
• Harsh underground conditions necessitate durable and stable sensing materials.
• Ruthenium (II) complexes are effective oxygen-sensing compounds but require protection.

Purpose of the Study:

• To develop a stable and durable fiber-optic oxygen sensor for harsh underground environments.
• To investigate the protective effects of silicone resin overcoating on ruthenium (II) complex-based optodes.
• To evaluate the impact of silicone resin on sensor sensitivity, response time, and long-term stability.

Main Methods:

• Preparation of composite films using silicone resin and ruthenium (II) complexes via spin coating.
• Fabrication of silicone resin overcoated ruthenium (II) complex films.
• Accelerated degradation tests using hot water (80°C) and simulated underground water.
• Sensitivity and response time measurements under varying dissolved oxygen and 100% oxygen gas conditions.

Main Results:

• Composite films showed increased sensitivity with exposure time, indicating instability.
• Silicone resin overcoating significantly improved the stability of ruthenium (II) complex films.
• Overcoated films exhibited stable sensitivity but slower response times (approx. 35x slower).
• Response time was directly influenced by the thickness of the silicone resin overcoating.

Conclusions:

• Silicone resin overcoating is effective in protecting fiber-optic oxygen sensors in harsh environments.
• The overcoating enhances sensor durability for mid- and long-term dissolved oxygen monitoring.
• Further optimization of overcoating thickness is needed to balance stability and response speed.