The challenge of nanotechnology is to discover new effects on already known materials and to convert exciting new findings into advanced technologies that are useful for industrial applications.
In ...these years, researchers have achieved the ability to produce quasi-one-dimensional (Q1D) structures in a variety of morphologies such as nanowires, core shell nanowires, nanotubes, nanobelts, hierarchical structures, nanorods, nanorings. In particular, Q1D Metal OXides (MOX) are attracting an increasing interest in gas sensing application: nanosized dimension ensures high specific surface that leads to the enhancement of catalytic activity or surface adsorption. Moreover, single-crystalline structures with well-defined chemical composition and surface terminations are not prone to thermal instabilities suffered from MOX polycrystalline counterpart. All these peculiarities can help to fill the gap between research and industrial application needs, aiming at the development of a reliable, low cost gas sensor.
This chapter presents an up-to-date survey of the research on Q1D metal oxide materials for gas sensing application, addressing the preparation techniques of sensing nano-crystals in connection with their electrical and optical properties. The application as resistive, transistor-based or optical-based gas sensors will be treated.
Interest in quasi ID nanostructures of semiconducting oxides is exponentially grown in the last years, due to their attracting potential applications in electronic, optical and sensor field. After ...comparing the characteristics of several MOX nanowires recently published we discussed on the sensing properties of metal oxide nanowires and nanotubes, as conductometric and optical gas sensors, prepared by the authors. Single crystal nanostructures were synthesized with the aim of exploring and studying their capabilities as nanosized sensors in form of multi and single nanowire sensors.
Interest in nanowires of semiconducting oxides is exponentially grown in the last years, due to their attracting potential applications in electronic, optical and sensor field. We have focused our ...attention on the sensing properties of metal oxide nanowires as conductometric and optical gas sensors and conductometric DNA sensor. Single crystal nanostructures were synthesized with the aim of exploring and studying their capabilities as nanosized sensors in form of multi nanowires sensors.
Extra virgin olive oil (EVOO) is characterized by its aroma and other sensory attributes. These are determined by the geographical origin of the oil, extraction process, place of cultivation, soil, ...tree varieties, and storage conditions. In the present work, an array of metal oxide gas sensors (called S3), in combination with the SPME-GC-MS technique, was applied to the discrimination of different types of olive oil (phase 1) and to the identification of four varieties of Garda PDO extra virgin olive oils coming from west and east shores of Lake Garda (phase 2). The chemical analysis method involving SPME-GC-MS provided a complete volatile component of the extra virgin olive oils that was used to relate to the S3 multisensory responses. Furthermore, principal component analysis (PCA) and k-Nearest Neighbors (k-NN) analysis were carried out on the set of data acquired from the sensor array to determine the best sensors for these tasks and to assess the capability of the system to identify various olive oil samples. k-NN classification rates were found to be 94.3% and 94.7% in the two phases, respectively. These first results are encouraging and show a good capability of the S3 instrument to distinguish different oil samples.
Layered multi-oxide concept was applied for fabrication of photoanodes for dye-sensitized solar cells based on ZnO and SnO2, capitalizing on the beneficial properties of each oxide. The effect of ...different combinations of ZnO@SnO2 layers was investigated, aimed at exploiting the high carrier mobility provided by the ZnO and the higher stability under UV irradiation pledged by SnO2. Bi-oxide photoanodes performed much better in terms of photoconversion efficiency (PCE) (4.96%) compared to bare SnO2 (1.20%) and ZnO (1.03%). Synergistic cooperation is effective for both open circuit voltage and photocurrent density: enhanced values were indeed recorded for the layered photoanode as compared with bare oxides (Voc enhanced from 0.39 V in case of bare SnO2 to 0.60 V and Jsc improved from 2.58 mA/cm(2) pertaining to single ZnO to 14.8 mA/cm(2)). Improved functional performances of the layered network were ascribable to the optimization of both high chemical capacitance (provided by the SnO2) and low recombination resistance (guaranteed by ZnO) and inhibition of back electron transfer from the SnO2 conduction band to the oxidized species of the electrolyte. Compared with previously reported results, this study testifies how a simple electrode design is powerful in enhancing the functional performances of the final device.
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