# Impact of GO Chemical Composition on the Performance of Humidity Sensors

## TL;DR

This paper shows how the chemical composition of graphene oxide affects its performance in humidity sensors, with one type showing much higher sensitivity.

## Contribution

The study introduces a comparative analysis of three graphene oxide types for humidity sensing, highlighting the role of chemical composition and structural defects.

## Key findings

- GO-II-based sensors showed the highest sensitivity (2113 ± 2%) compared to GO-I and GO-III.
- GO-II's improved performance is attributed to higher quantities of polar oxygenated functional groups and structural defects.
- All sensors operated at low voltage (0.1 V), making them suitable for low-power systems.

## Abstract

Graphene oxide (GO), a structurally defective 2D carbon
nanomaterial,
is very promising for relative humidity (RH) sensing applications
due to the presence of diverse oxygenated functional groups (OFGs)
in its structure. The characteristics of GO, such as flake size, degree
of oxidation and exfoliation, permanent structural defects, and chemical
composition, directly impact the RH detection performance of GO. In
this work, we investigated the performance of resistive RH sensors
based on three types of GO, prepared using modifications of the Hummers’
method, namely, GO-I, GO-II, and GO-III, having different chemical
composition, degree of oxidation, as well as different levels of permanent
structural defects (carbon vacancies) at the basal plane. GO-based
RH sensors were fabricated by drop-casting GO suspensions onto aluminum
interdigitated electrodes thermally evaporated onto glass substrates.
Among the three characterized RH sensors, GO-II-based devices showed
superior performance, with a sensitivity of 2113 ± 2% compared
to 1592 ± 1% for GO-I and 388.1 ± 0.1% for GO-III, respectively.
All GO sensors demonstrated rapid response and recovery times (ca.
2 and 3 s). Our results indicate that improved quantities of highly
polar OFGs, such as carbonyl and hydroxyl groups, and the associated
permanent structural defects in GO-II, significantly improved its
RH sensing properties. In addition, all GO-based RH sensors can be
operated at only 0.1 V, making them suitable for integration into
low-power systems.