Abstract
Hollow spheres of pure ZnFe2O4 and of composites of ZnFe2O4 and reduced graphene oxide (rGO) with different rGO content were prepared via a simple solvothermal method followed by a high-temperature annealing process in an inert atmosphere. The X-ray diffraction analysis confirmed that the introduction of rGO had no effect on the spinel structure of ZnFe2O4. In addition, the results of field-emission scanning electron microscopy and (high-resolution) transmission electron microscopy indicated that the synthesized samples had the structure of hollow spheres distributed uniformly onto rGO nanosheets. The diameters of the spheres were determined as about 600–1000 nm. The gas sensing test revealed that the introduction of rGO improved the performance of the sensing of acetone to low concentration, and the ZnFe2O4/rGO composite gas sensor containing 0.5 wt % of rGO exhibited a high sensitivity in sensing test using 0.8–100 ppm acetone at 200 °C. The response of the 0.5 wt % ZnFe2O4/rGO sensor to 0.8 ppm acetone was 1.50, and its response to 10 ppm acetone was 8.18, which is around 2.6 times more pronounced than the response of pure ZnFe2O4 (10 ppm, 3.20). Moreover, the sensor showed a wide linear range and good selectivity.
Highlights
As a synthetic raw material in industrial production, acetone is chemically active and extremely flammable
The characteristic peaks of reduced graphene oxide (rGO), that should be observed at about 24°, are not clearly identified in the patterns, which may be ascribed to the low mass fraction of rGO in the ZnFe2O4/ rGO composites [35,36]
The results demonstrate that the response of the hollow spheres made of pure ZnFe2O4 and of ZnFe2O4/rGO with 0.5 wt % rGO are more intense at higher concentration of acetone
Summary
As a synthetic raw material in industrial production, acetone is chemically active and extremely flammable. It is toxic if its concentration exceeds 173 ppm, and long-term exposure to acetone poses a serious threat to human health [1,2]. According to the related literature, the concentration of acetone in the exhaled gas of healthy people is less than 0.8 ppm, while that in exhaled gas of diabetic patients is higher than 1.8 ppm [3,4]. In this view, it may be possible to diagnose diabetes using a nondestructive testing technology based on sensing acetone. It is necessary to develop novel micro/nanomaterials, which can be applied as high-performance gas sensors to detect acetone at low concentration or to monitor variations of its concentration
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