An NETL and University of Pittsburgh research team demonstrated how the use of plasmonic nanomaterials (pNPs) and porous polymer composite coating in optical fiber sensing technologies can detect energy-relevant gases, such as carbon dioxide (CO₂) and methane (CH₄).

The technology can help ensure safer, quicker, and more secure underground storage and pipeline monitoring. The results appeared in a paper published in Advanced Materials, one of the world’s most prestigious multidisciplinary research journals that straddles materials science, innovative technologies, and real-world applications.

Optical fiber sensors offer advantages over other types of sensors because they are small, lightweight, can endure high temperatures and pressures, and are immune to electromagnetic interference. In addition, the optical fiber sensors feature long-reach and spatially distributed monitoring.

The latest research demonstrates how plasmonic nanoparticles (pNPs) can be incorporated into the porous polymer coating to enhance the monitoring capabilities of optical fiber sensors to build on extensive distributed sensor technology research at NETL.

pNPs — including gold, silver and platinum particles — are discrete metallic particles or metal oxide particles such as tin-doped indium oxide (ITO) that have unique optical properties due to their size and shape and are increasingly being incorporated into commercial products and technologies. They have unique optical, electrical, and thermal properties that make them effective for use in applications such as antimicrobial coatings and molecular diagnostics.

Sensing technologies based on pNPs are of interest for various chemical, biological, environmental, and medical applications. Plasmonic gas sensors exhibit high sensitivity, but until recently have not been demonstrated to the chemically stable gases such as CO₂ at room temperature. In this specific case, NETL researchers Ki-Joong Kim, Jeffrey T. Culp, Jeffrey Wuenschell, Ali K. Sekizkardes, and former NETL researchers Roman A. Shugayev,and  Paul R. Ohodnicki developed the highly sensitive material that can be used to detect CO₂ (or CH₄ ) in ambient environments.

The paper describes how researchers created a composite film that provides distinct and tunable optical features on a fiber optic platform that can be used as a signal transducer for gas sensing under atmospheric conditions.

Researchers explain in the paper that by varying the pNPs content in a polymer matrix, the optical behavior of the composite film can be tuned to affect the operational wavelength by over several hundred nanometers and the sensitivity of the sensor in the near-infrared range. Tuning plasmon resonance across the near-infrared range is particularly important in distributed or quasi-distributed sensing approaches, which are more compatible with distributed interrogation systems.

The research also demonstrated that the pNPs-polymer composite film exhibits remarkable long-term stability by mitigating the physical aging issue of the polymer. The sensor can operate at atmospheric conditions without significant signs of degradation.

“Developments of sensing technologies are important to a clean energy future, including safe underground storage of CO₂ and detection of CH₄ leaks,” according to Ruishu Wright of NETL’s functional materials team, “Visibility  and monitoring are important for evaluating and managing operational risks of underground CO₂ storage. Real-time monitoring is needed to assure storage and pipeline infrastructure integrity and to detect early signs of gas leakage.”

She said there are many commercial gas sensors for CO₂ or CH₄ in operation, including catalytic combustion sensors, electrochemical sensors, thermo-conductivity sensors, resistive sensors, acoustic leak sensors, and optical-based sensors. But the challenge is that existing sensor technologies are mostly point or standoff sensors.

“There is a real need for wide-area and long-distance monitoring for CO₂ and CH₄ leak detection in large-scale storage facilities and for CH₄ gas detection at well sites and industrial facilities. Early leak detection of the greenhouse gases will help to mitigate gas emissions and combat global warming.”

NETL is a U.S. Department of Energy national laboratory that drives innovation and delivers technological solutions for an environmentally sustainable and prosperous energy future. By using its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.