New method of synthesizing In2O3 nanoparticles for application in volatile organic compounds (VOCs) gas sensors

In2O3 nanoparticles have increasingly attracted interest over the past decade due to their novel properties [1]. They are usually synthesized by using chemical routes such as sol-gel and solid-state reaction methods [2, 3]. However, there are some limitations such as a low yield rate, impurity pollution and agglomerates in these techniques. Recently, we have developed a new specific device in which inductive resource and continuous wave CO2 laser beam were compounded to synthesize metal and their oxide nanoparticles, which can overcome the above-mentioned limitations [4]. Using this hybrid induction and laser heating (HILH) method, refractory cobalt amorphous or crystalline nanoparticles as well as Sb2O3 nanoparticles were synthesized [5, 6]. Also tetrapod-like ZnO nanowiskers were synthesized using this novel method and its yield rate can reach several kilograms per hour [7]. In this study, the In2O3 nanoparticles were synthesized by means of HILH, and the characteristics of the nanoparticles was systematically investigated by transmission electron microscope (TEM) and X-ray diffraction (XRD). As a gas sensing material, In2O3 has been extensively applied to detect O3, NO2 and CO etc. [8–10]. We believe that the gas-sensing properties of In2O3 for volatile organic compounds (VOCs), especially toxic VOCs that are harmful to human health and the environment, have not been broadly studied. So the gassensing properties for five VOCs (benzene, toluene, xylene, acetone and alcohol) of thick films based on as-synthesized In2O3 nanoparticles were studied in this letter. The experimental setup of HILH is described in the literature elsewhere [6]. The experimental procedures were as follows: the metallic indium was heated to a certain temperature by induction-heating in a vacuum chamber with a flowing mixed Ar+O2 gas at a pressure of 1.0× 104 Pa, where the oxygen partial pressure was kept fixed at about 2× 103 Pa by controlling the oxygen flux. Subsequently, the continuous wave CO2