Microwave surface impedance measurements on reduced graphene oxide

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Reduced graphene oxide (rGO) is a promising material with applications in various fields.
• Understanding the interaction of rGO with water is crucial for its practical use.
• Existing methods for water content analysis may be contact-based or less sensitive.

Purpose of the Study:

• To develop and validate a non-contact microwave technique for measuring water content in reduced graphene oxide.
• To investigate the behavior of adsorbed water in rGO films during heating and cooling cycles.
• To differentiate between surface-adsorbed and intercalated water in multilayer rGO samples.

Main Methods:

• Utilized a high Q dielectric resonator perturbation technique for microwave surface impedance measurements.
• Modeled plane wave propagation of microwaves interacting with graphene on quartz substrates.
• Derived analytical solutions for resonant frequency and microwave loss changes based on water layer thickness.

Main Results:

• Successfully measured the presence of adsorbed water layers in reduced graphene oxide films.
• Demonstrated that low-temperature annealing effectively removes water from both single and multilayer rGO samples.
• Indicated that water is intercalated between layers in multilayer samples, not just surface-adsorbed.

Conclusions:

• The non-contact microwave method is effective for quantifying water in rGO.
• Water can be released from intercalated spaces in multilayer rGO via mild heating.
• This technique offers a sensitive approach to study water interactions with graphene-based materials.