Preparation of Graphene Quantum Dots and Their Sensing Properties in Quartz Crystal Microbalance Acetone Sensor

Abstract

Acetone is a slightly toxic volatile organic gas, which exists in the breath and is closely related to diseases such as diabetes. In this paper, a quartz crystal microbalance (QCM) was used to fabricate an acetone sensor, and graphene quantum dots (GQDs) were used as a gas-sensing material to modify the QCM. GQDs were prepared by citrate pyrolysis and characterized by high-resolution transmission electron microscopy (TEM). The gas sensitivity of the sensor to low concentrations of acetone was investigated. It exhibited good linearity at acetone concentrations of less than 240 ppm with a sensitivity of 16.78 Hz/ppm and a minimum detection limit of 2.5 ppm, and the fitted line had a coefficient of determination R 2 of 0.95658. In a mixture of acetone, butanol, and isopropanol, the sensor exhibited good selectivity for acetone. For different acetone concentrations, the response speed of the same sensor was basically the same, and the response and recovery times were 32 and 48 s, respectively. We showed that the prepared gas sensor has good sensitivity, repeatability, and selectivity for low concentrations of acetone.

Recent development in carbon dot-based gas sensors

“…Modified Hummer's method along with microwave assistance was developed to produce GQDs where cleaving and reduction of carbon precursors dissolved in strong acids occurs under microwave irradiation resulting in rapid and uniform heating of reaction medium (figure 3b) [8]. Although the top down approach is simple and less expensive, they provide poor control of size and chemical homogeneity of synthesized CDs [2,15,16,21,22]. As particle size increases, specific surface area decreases which limits the active sites on CDs [15].…”

“…Here, CDs are obtained by carbonization of molecular precursors containing carbon, required functional group and doping elements (figure 4a) [4]. Bottom-up approach helps in achieving better structural and chemical homogeneity [21,22]. Some of the bottom-up synthesis routes are hydrothermal treatment, solvothermal, pyrolysis, microwave pyrolysis/irradiation, etc.…”

“…CDs have been grown by certain exotic routes such as confined reactions in nanoreactors, oxygen plasma treatment [2], microplasma process [10], etc. But the downside of the bottom-up synthesis approach is that these processes are complicated and the products obtained generally have poor solubility [22].…”

“…On exposure to acetone, gas molecules are physisorbed/chemisorbed on GQDs surface through Van der Waals interaction of gas molecules and hydroxyl, carboxyl and carbonyl groups on CDs and through percolation-diffusion process. Since GQDs possess large surface area, more of acetone molecules may be adsorbed which results in improved sensitivity sensors [22].…”

“…As a result, GQDs exhibit advantageous properties of both graphene and quantum dots [6,21,22]. CDs have been used as innocuous optical imaging probes and for sensing in solution or solid phase, as they exhibit excellent luminescence properties [6,23].…”