High-Performance and Sensitive Humidity Sensors Based on Reduced Graphene Oxide/Nickel Ferrite Nanocomposites

Abstract

This work reports the fabrication of highly sensitive humidity sensors using reduced graphene oxide (rGO), nickel ferrite nanoparticles (NiFe2O4 NPs), and their nanocomposites. rGO and NiFe2O4 NPs, obtained by the modified Hummers method and the wet chemical coprecipitation method, respectively, were used to synthesize rGO/NiFe2O4 nanocomposites at two different compositions. XRD analysis confirmed both the spinel structure of NiFe2O4 and the reinstatement of π-conjugated structure of graphene. Average crystallite sizes, calculated by XRD, were 17.80 nm, 13.60 nm, and 8.22 nm for NiFe2O4 NPs, rGO/NiFe2O4 (70/30), and rGO/NiFe2O4 (90/10), respectively. FTIR affirmed the successful reduction of graphene oxide to rGO. Optical bandgaps of 1.83 eV and 2.18 eV were obtained for rGO and NiFe2O4 respectively using Tauc plot. SEM confirmed the films’ porosity, providing more active sites for the adsorption of water molecules. Our results demonstrate that NiFe2O4 NPs show the highest response and sensitivity within the 35–90 RH% range. Additionally, the rGO/NiFe2O4 (70/30) nanocomposite achieved the fastest response/recovery time of 8/4 s at 100 Hz, with good repeatability and stability. These findings suggest that rGO/NiFe2O4 NCs are promising candidates for advanced humidity sensing applications due to their rapid response, sensitivity, and long-term reliability.