| 1. |
- Guidi, V., et al.
(författare)
-
Diffusion-equation approach to describe ionic mobility in nanostructured titania
- 2005
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 72:15
-
Tidskriftsartikel (refereegranskat)abstract
- The linear diffusion equation is proposed to provide a macroscopic description of ionic mobility in nanostructures. This approach has been demonstrated to account for diffusion processes in nanostructured titania-based films. The formulation of a classical diffusion inverse problem and the experimental determination of concentration profiles by Rutherford backscattering spectrometry were used for the purpose. The model has allowed the measurement of the diffusion coefficient of W and Mo impurities in titania. © 2005 The American Physical Society.
|
|
| 2. |
- Pardo, M., et al.
(författare)
-
Data preprocessing enhances the classification of different brands of Espresso coffee with an electronic nose
- 2000
-
Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 69:3, s. 397-403
-
Tidskriftsartikel (refereegranskat)abstract
- Two different ways of preprocessing chemical sensor data are presented as a means to improve the interpretation and the classification ability of an electronic nose (EN). The practical problem at hand is the distinction between four commercial coffee blends - containing up to 12 types of coffees - all of which are to be consumed as Espresso. Coffee was sampled in three successive preparation phases: a beans, ground (powder) or liquid (the actual Espresso). In the case of beans, stress is put on the improved clusters visualization after the preprocessing and before the actual classification is performed. Different catalysed sensors and successive extractions were used to differentiate the response pattern towards the various coffees. The features which permitted the best samples' classification as judged from Principal Component Analysis (PCA) score plots were selected. To this end, an empirical search strategy inside the feature space is presented. Scores from PCA were subsequently utilized as inputs for a feed forward multilayer perceptron (MLP) with cross-validation resulting in 100% correct classification with just two sensors. In the case of ground coffee, a (supervised) drift compensation algorithm was developed. It essentially consists of removing the first principal component (PC) for every cluster since this is seen to be given by the drift. An 87.5% classification performance was achieved. Liquid coffee, on the other hand, was not successfully classified, probably due to the difficulty in assuring reproducible sampling conditions.
|
|
| 3. |
- Vomiero, Alberto, et al.
(författare)
-
Application of ion beam analysis to the selective sublimation processing of thin films for gas sensing
- 2006
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 249:1-2 SPEC. ISS., s. 302-305
-
Tidskriftsartikel (refereegranskat)abstract
- Ion beam analysis was successfully applied to a novel technique, named selective sublimation process (SSP), for deposition of nanostructured gas-sensing films through reactive sputtering. The method consists of the co-deposition of a mixed oxide, one of which has a relatively low sublimation temperature. Annealing at suitable temperature causes the sublimation of the most volatile compound, leaving a layer with adjustable composition. The appropriate choice of thermal treatments and the consequent tailoring of the composition play a crucial role in the determination of the microstructural properties. We developed a model based on diffusion equations that provides a useful guide to control the deposition and processing parameters and we applied the model on the systems TiO2-WO3 and TiO2-MoO3. Rutherford backscattering (RBS) was demonstrated to be effective for the characterization of the diffusion and sublimation processes during SSP. Experimental results fully agree with theoretical prediction, and allowed the calculation of all the parameters involved in SSP. © 2006 Elsevier B.V. All rights reserved.
|
|
| 4. |
- Comini, E., et al.
(författare)
-
Influence of iron addition on ethanol and CO sensing properties of tin oxide prepared with the RGTO technique
- 2006
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 115:2, s. 561-566
-
Tidskriftsartikel (refereegranskat)abstract
- Effects of iron introduction in RGTO prepared tin oxide gas sensors are presented. The films were deposited by sputtering from a tin target with the introduction of an adjustable number or iron inset. Iron content was varied in the range 0-7%. The thin films are investigated by the volt-amperometric technique for electrical and gas-sensing properties. The layers are capable of sensing CO and ethanol, no evidence of surface poisoning is detected, and recovery of the resistance is complete. The response of the sensors is stable and reproducible at all operating temperatures tested (200-500 °C) during 3 months of operation. © 2005 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Ortolani, L., et al.
(författare)
-
Electrical and holographic characterization of gold catalyzed titania-based layers
- 2007
-
Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 27:13-15, s. 4131-4134
-
Tidskriftsartikel (refereegranskat)abstract
- The sensing properties of titanium oxide have been tailored through doping with niobium and dispersion of nanosized Au particles. The microstructural features of the gold-titania composite system were investigated by transmission electron microscopy and the electronic properties of Au nanoparticles were specifically investigated by electron holography. Holography provides quantitative determination of the mean inner potential with the high spatial resolution attained by transmission electron microscopy. Large increase of the mean inner potential has been measured for ultra small Au particles arising from the nano-scale assembling. Electrical tests were performed at low operating temperatures and demonstrated the considerable enhancement of CO sensitivity owing to the extremely high catalytic activity of gold particles. © 2007 Elsevier Ltd. All rights reserved.
|
|
| 6. |
- Sberveglieri, G., et al.
(författare)
-
Preparation of transparent conducting oxide nanostructures for dye-sensitized solar cells
- 2008
-
Ingår i: 2008 33rd IEEE Photovoltaic Specialists Conference. - Piscataway, NJ : IEEE Communications Society. - 9781424416417
-
Konferensbidrag (refereegranskat)abstract
- ZnO, SnO2, Indium-tin oxide (ITO) nanostructures have been produced on glass substrates coated with a transparent conducting oxide (TCO) electrode for application in dye sensitized solar cells (DSC). Quasi one-dimensional (1D) nanostructures of different TCOs have been synthesized using the vapour transport-and-condensation technique. Nanostructures with different shape and aspect-ratio can be obtained by properly tailoring of the condensation conditions and the substrate preparation. A multi technique approach, using electron microscopy and DC electrical characterization, has been applied for micro-structural and functional characterization of the nanostructures. © 2008 IEEE.
|
|
| 7. |
- Vomiero, Alberto, et al.
(författare)
-
Integration of metal oxide nanowires in dye sensitized solar cells
- 2009
-
Ingår i: 2009 34th IEEE Photovoltaic Specialists Conference : (PVSC 2009). - Piscataway, NJ : IEEE Communications Society. - 9781424429509 ; , s. 001325-001326
-
Konferensbidrag (refereegranskat)abstract
- One of the most promising architectures of third generation solar cells is integration of single crystalline nanowires as electron transporters in anodes of electrochemical cells.[1-3] The nanowire-based cells aim at significantly increase cell efficiency thanks to the higher mobility of electrons along the single crystalline lattice of the nanowires with respect to traditional polycrystalline networks, greatly reducing electron-hole recombination controllable by passivation, functionalization or coaxial coating of the nanowire. The nanonetworks have been integrated in DSCs using the traditional N719 dye and the I-3/I-3 redox couple. The functional properties of the cells under 1 sun irradiation have been compared with traditional polycrystalline TiO2 photoanodes. ©2009 IEEE.
|
|
| 8. |
- Bianchi, S., et al.
(författare)
-
Indium oxide quasi-monodimensional low temperature gas sensor
- 2006
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 118:1-2, s. 204-207
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the sensing properties of indium oxide nanostructures and tailored the deposition conditions in order to obtain nano-wires of indium oxide. We have comparatively tested the gas sensing properties of nano-wires with micrometric or even nanometric size. The micro-wires feature interesting gas sensitivity at room temperature, particularly in the case of nitrogen dioxide detection. The sensing performance is improved as the lateral dimension of the wire decreases. © 2006 Elsevier B.V. All rights reserved.
|
|
| 9. |
- Comini, E., et al.
(författare)
-
Functional nanowires of tin oxide
- 2007
-
Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 89:1, s. 73-76
-
Tidskriftsartikel (refereegranskat)abstract
- Quasi-one-dimensional nanostructures of tin oxide were produced in controlled conditions through condensation from the vapor phase. The preparation was assisted by noble metal catalysts and uniform single-crystalline nanowires were produced. The nucleation of nanowires was achieved at 470 °C, owing to the vapor-liquid-solid growth mechanism activated by the catalytic Pt clusters. The peculiar microstructural properties of these semiconducting metal oxide nanostructures will be summarized. The high aspect ratio and the high degree of crystallinity achieved for the nanowires foresee their functional exploitation. © 2007 Springer-Verlag.
|
|
| 10. |
- Comini, E., et al.
(författare)
-
Quasi-one dimensional metal oxide semiconductors : Preparation, characterization and application as chemical sensors
- 2009
-
Ingår i: Progress in Materials Science. - : Elsevier BV. - 0079-6425 .- 1873-2208. ; 54:1, s. 1-67
-
Tidskriftsartikel (refereegranskat)abstract
- The continuous evolution of nanotechnology in these years led to the production of quasi-one dimensional (Q1D) structures in a variety of morphologies such as nanowires, core-shell nanowires, nanotubes, nanobelts, hierarchical structures, nanorods, nanorings. In particular, metal oxides (MOX) are attracting an increasing interest for both fundamental and applied science. MOX Q1D are crystalline structures with well-defined chemical composition, surface terminations, free from dislocation and other extended defects. In addition, nanowires may exhibit physical properties which are significantly different from their coarse-grained polycrystalline counterpart because of their nanosized dimensions. Surface effects dominate due to the increase of their specific surface, which leads to the enhancement of the surface related properties, such as catalytic activity or surface adsorption: key properties for superior chemical sensors production. High degree of crystallinity and atomic sharp terminations make nanowires very promising for the development of a new generation of gas sensors reducing instabilities, typical in polycrystalline systems, associated with grain coalescence and drift in electrical properties. These sensitive nanocrystals may be used as resistors, and in FET based or optical based gas sensors. This article presents an up-to-date review of Q1D metal oxide materials research for gas sensors application, due to the great research effort in the field it could not cover all the interesting works reported, the ones that, according to the authors, are going to contribute to this field's further development were selected and described. © 2008 Elsevier Ltd. All rights reserved.
|
|
