Fabricação e caracterização de sensores de umidade híbridos baseados em óxido de grafeno rico em grupo hidroxila e nanopartículas de ouro via espectroscopia de impedância

Abstract

Humidity sensors have applications in meteorological monitoring, industrial/agricultural processes, food storage, medical devices, automotive systems, and energy management, among others. Continuous improvements to these sensors aim to enhance their properties and applications. This development involves the incorporation of specific materials, such as ceramics, organic thin films, polymers, and carbon-based materials. Among them, carbon nanomaterials, like Graphene Oxide (GO), have enhanced detection properties, promising significant advancements in humidity sensor technology. In this context, this work aims to synthesize and characterize hydroxyl-rich graphene oxide (HGO) and fabricate devices containing HGO and gold nanoparticles (AuNP) for efficient humidity detection. Different device configurations were evaluated, including layer-by-layer deposition of thin films of these two materials and the deposition of a single film of the HGO mixture. Spectroscopic analyses of the materials highlighted the successful modification of HGO with AuNP through spectral changes indicative of structural distortions in the HGO lattice. Scanning electron microscopy and atomic force microscopy revealed the distribution of nanoparticles on HGO sheets and their sizes, with an average diameter of 18 nm. Impedance spectroscopy showed high sensitivity with 0.032 log Z / %RH and response times of approximately 0.2 seconds for the HGO sensor modified with AuNP, highlighting the synergy between both materials, primarily through a charge transfer process elucidated by a review of the humidity detection mechanism.