| 초록 |
Chemiresistive electronic noses (CENs), including the integrated metal oxides sensor array, have been commercially applied and widely used in analysis tools for applications such as indoor/ outdoor air quality system, home security, food safety, medical diagnosis, military and automobile fields and environmental monitoring. Of these applications, environmental monitoring system (EMS) for protection and restoration has been led to a serious and keen attraction due to high increase of global energy usage, odors and unwanted atmosphere pollutants by the industrialization of developing countries. One of the most important components of EMS is highly sensitive and selective gas sensor array whose signal output is analyzed with pattern recognition techniques and principle component analysis software. However, conventional gas analysis methods such as gas chromatography mass spectrometry (GC-MS) and Fourier transform infrared (FT-IR) spectrometry generally are bulky, slow, high cost, and even miniaturized sensor array has never been commercialized and is still challenging. Compare to these analyzers, the electronic nose (e-nose) based on semiconducting metal oxide (SMO) has the potential to be miniaturized, fast, and inexpensive. Therefore, the SMO-based e-nose has been demonstrated to be promising technologies to address concerns about the pristine environmental degradation. To achieve the advanced technology, CEN based on metal oxide nanostructures such as nanowires, nanotubes, and nanofibers has attracted attention regarding their application in the miniature e-nose. For representative example, heterogeneous metal oxide nanowire microsensor array announced by Dante DeMeo et al. was integrated with four different sensing elements by hydrothermal synthesis and has shown the possibility to distinguish between acetone, methanol and ammonia due to the large responses to them by MnOx, and VOx. However, the use of metal oxide nanowires by chemical reaction method is still under challenging stage in how to integrate them with low-cost, low reproducibility and synthesis in place (selected area or sensing layer) for array configuration. As an alternative approach, metal oxide nanostructures by physical vapor deposition (PVD) are considered as more desirable configuration for CEN due to simplicity in synthesis, high stability and reproducibility, and excellent compatibility with semiconductor processes. Moreover, the combination of different types (thin films, metal catalyst, and metal oxide nanostructures) in CEN by PVD can simultaneously be implemented various sensing performances due to their distinguished sensing mechanisms. As far as we know, the different types of metal oxide nanostructures-based CEN has not been studied yet, in particular under a highly humid environment. In this study, we describe the novel procedures of CEN (3ⅹ3 sensor array) which allow three different architectures of three materials including tungsten trioxide (WO3), tin dioxide (SnO2), and indium oxide (In2O3), and demonstrate chemiresistive sensing properties of a 9-sensor array. The CEN composed of the thin films, Au nano-clusters on thin films, and nanostructures with a high specific surface area which have been achieved using glancing angle deposition by e-beam deposition. In order to investigate whether the CEN was able to distinguish between various gases, principle component analysis (PCA) was applied to 9 samples and even analyzed PCA in gas mixture (NO2 + H2S). Consequently, highly sensitive and selective sensing properties of our CEN by PCA suggest the great potential for gas monitoring. |
