Developed Low-Temperature Anionic 2H-MoS₂/Au Sensing Layer Coated Optical Fiber Gas Sensor

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Molybdenum disulfide (MoS₂) is a promising material for optical sensing applications.
• Achieving stable and efficient semiconductor properties in MoS₂-based optical fiber sensors remains a challenge.
• Carboxyl functionalization (COOH) can enhance the properties of MoS₂ nanosheets.

Purpose of the Study:

• To develop a novel optical fiber sensor using carboxyl-functionalized molybdenum disulfide (COOH-MoS₂) nanosheets.
• To investigate the phase transformation and adhesion properties of COOH-MoS₂ on optical fibers.
• To evaluate the sensing performance for volatile organic compounds (VOCs) and cross-sensitivity to humidity.

Main Methods:

• Facile low-temperature hydrothermal synthesis of COOH-MoS₂ nanosheets.
• Deposition of Au thin film on unclad optical fiber for COOH-MoS₂ sensing layer.
• Phase transformation of 1T-MoS₂ to 2H-MoS₂ facilitated by Au thin film.
• Evanescent wave intensity variation principle for gas detection.
• Quantitative detection of ethanol, propanol, and methanol vapors.

Main Results:

• Successfully prepared COOH-MoS₂ nanosheets with improved semiconducting properties and adhesion on optical fibers.
• The developed sensor demonstrated high sensitivity and linearity (R² = 0.999) for methanol detection at room temperature.
• The sensor exhibited a maximum response to methanol among the tested VOCs.
• Cross-sensitivity to relative humidity was evaluated.

Conclusions:

• The developed COOH-MoS₂/Au-coated optical fiber sensor offers a promising platform for sensitive and selective VOC detection.
• The integration of Au thin film effectively addresses the limitations of semiconducting properties and adhesion of COOH-MoS₂ on optical fibers.
• This sensing system shows potential for real-world applications in environmental monitoring and gas sensing.