Graphene-Encapsulated Silver Nanoparticles for Plasmonic Vapor Sensing

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Silver nanoparticles (AgNPs) exhibit unique optical properties due to surface plasmon resonance.
• Graphene is a promising material for sensor applications due to its unique electronic and surface properties.
• Local Surface Plasmon Resonance (LSPR) is sensitive to the surrounding dielectric environment, making it useful for sensing.

Purpose of the Study:

• To develop and characterize graphene-covered silver nanoparticles (G/AgNPs) on graphite substrates for vapor sensing.
• To investigate the substance-specific optical responses of G/AgNPs to various volatile organic compounds (VOCs) and water vapor.
• To explore the impact of graphene defects, introduced by O2 plasma, on the sensor performance and recovery.

Main Methods:

• Preparation of G/AgNPs directly on highly oriented pyrolytic graphite (HOPG) substrates.
• Characterization using atomic force microscopy (AFM).
• UV-Vis reflectance spectroscopy to measure LSPR shifts upon exposure to acetone, ethanol, 2-propanol, toluene, and water vapor.
• Principal component analysis (PCA) for data interpretation.
• Introduction of point defects using O2 plasma and subsequent annealing for recovery.

Main Results:

• G/AgNPs exhibited substance-specific optical responses to different vapors.
• PCA confirmed the distinct spectral fingerprints for each analyte.
• O2 plasma treatment altered the LSPR, indicating sensitivity to graphene defects.
• Annealing successfully recovered the LSPR signal after plasma treatment.
• Defects modulated the sensor response: increased for toluene and water, decreased for acetone.

Conclusions:

• G/AgNPs on HOPG are effective for selective vapor detection.
• Graphene defects significantly influence the LSPR-based sensing mechanism.
• The ability to tune sensor response via defect engineering and recovery offers a pathway for developing advanced chemical sensors.