Abstract
Graphene has become a material of choice for an increasing number of scientific and industrial applications. It has been used for gas sensing due to its favorable properties, such as a large specific surface area, as well as the sensitivity of its electrical parameters to adsorption processes occurring on its surface. Efforts are ongoing to produce graphene gas sensors by using methods that are compatible with scaling, simple deposition techniques on arbitrary substrates, and ease of use. In this paper, we demonstrate the fabrication of carbon dioxide gas sensors from Langmuir–Blodgett thin films of sulfonated polyaniline-functionalized graphene that was obtained by using electrochemical exfoliation. The sensor was tested within the highly relevant concentration range of 150 to 10,000 ppm and 0% to 100% at room temperature (15 to 35 °C). The results show that the sensor has both high sensitivity to low analyte concentrations and high dynamic range. The sensor response times are approximately 15 s. The fabrication method is simple, scalable, and compatible with arbitrary substrates, which makes it potentially interesting for many practical applications. The sensor is used for real-time carbon dioxide concentration monitoring based on a theoretical model matched to our experimental data. The sensor performance was unchanged over a period of several months.
Highlights
Carbon dioxide (CO2 ) sensing has important applications across various industries, including pollution monitoring [1], hazard detection [2], smoke detection [3], room ventilation monitoring [4], and personal protection
The supplier performed electrochemical exfoliation from graphite in a process that resulted in sulfonated polyaniline (PANI) functionalization of graphene nanosheets in a solution of N-methyl pyrrolidone (NMP) at a concentration of >2 mg/mL
Given that the time required for reaching the set concentration in our homebuilt gas sensing chamber is estimated to be in the order of 1 s, it is reasonable to assume based on the results shown in Figure 4 that τ is determined by the kinetics of the adsorption–desorption (AD) process on the sensing surface
Summary
Carbon dioxide (CO2 ) sensing has important applications across various industries, including pollution monitoring [1], hazard detection [2], smoke detection [3], room ventilation monitoring [4], and personal protection. As CO2 is one of the most important greenhouse gases, monitoring its concentration is indispensable in environmental protection, climate change monitoring [2], and carbon emissions cutting [5]. Graphene reacts to the presence of analyte gases by charge transfer from the substrate or electrical contacts, which causes a change in its electrical properties, such as carrier density [11]. As opposed to bulk graphite, exfoliated graphene has an electron cloud in pi orbitals above the surface, with which analytes can readily react.
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