A high-performance moisture sensor based on ultralarge graphene oxide

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Graphene oxide (GO) is a promising material for humidity sensing.
• The lateral size of GO sheets can influence sensor performance.
• Understanding GO size effects is crucial for optimizing humidity sensor design.

Purpose of the Study:

• To investigate the impact of graphene oxide (GO) lateral size on humidity sensing properties.
• To compare the performance of sensors fabricated with ultralarge graphene oxide (UGO) and small-sized graphene oxide (SGO).
• To evaluate the potential of UGO-based sensors for advanced applications.

Main Methods:

• Fabrication of humidity sensors using gold electrodes coated with UGO (47.4 ± 22.2 μm) and SGO (0.8 ± 0.5 μm).
• Measurement of in-plane conductance changes with relative humidity (RH) from 7% to 100%.
• Analysis of sensor sensitivity, response/recovery times, and stability.
• Evaluation of proton conductivity via activation enthalpy (Ea).

Main Results:

• UGO sensors exhibited a four-order-of-magnitude increase in conductance, compared to three orders for SGO sensors.
• Maximal sensitivity was higher for UGO (4339 ± 433) than SGO (1982 ± 122).
• UGO sensors demonstrated ultrafast response/recovery times (0.2/0.7 s) and excellent stability (±4.6% variation over five days).
• Lower activation enthalpy for UGO (0.63 eV) vs. SGO (1.14 eV) indicated improved proton conductivity.

Conclusions:

• The lateral size of graphene oxide significantly impacts humidity sensing performance.
• Ultralarge graphene oxide sheets offer superior sensitivity and response times for humidity sensors.
• UGO-based sensors show potential for touchless interface applications, including fingertip moisture detection.