| 1. |
- Bravo, L, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 2. |
- Tabiri, S, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 3. |
- Glasbey, JC, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Abom, A.E., et al.
(författare)
-
Experimental evidence for a dissociation mechanism in NH3 detection with MIS field-effect devices
- 2003
-
Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 89:1-2
-
Tidskriftsartikel (refereegranskat)abstract
- The gas response mechanism of ammonia detection with Pt-based metal-insulator-semiconductor (MIS) field-effect sensors was investigated. An experimental model system was designed which compares the responses of thick continuous Pt layers with controlled morphology and surface chemical composition, with the response of thin, discontinuous layers. The surface of a thick, continuous sputter-deposited Pt film is modified, either by (i) the deposition of a thin SiO2 overlayer, (ii) reactive sputter deposition of PtOx, or (iii) co-deposition of Pt with SiO2 in Ar + O2 atmospheres. We show that the ammonia response is caused by the formation of atomic hydrogen through the dissociation of NH3 at temperatures <200 °C. It is found that the modified surfaces exhibit increased ammonia selectivity compared to a pure Pt film. Results from this work indicate that the reason for the changed selectivity is the appearance of an oxidized PtOx phase or triple phase boundaries between Pt, SiO2 and the ambient gas, rather than for solely morphological reasons. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 7. |
- Abom, A.E., et al.
(författare)
-
Thin oxide films as surface modifiers of MIS field effect gas sensors
- 2002
-
Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 85:1-2, s. 109-119
-
Tidskriftsartikel (refereegranskat)abstract
- The catalytic activity at the surface of Pt based MIS field effect gas sensors is modified by the deposition of thin films of SnO2, Al2O3 and SiO2, grown by reactive sputtering. It is found that a very thin layer (<10 nm) of SiO2 and SnO2 changes the catalytic activity towards higher NH3 selectivity, but with thicker films the sensor response vanishes. Since the response mechanism for these sensors is dependent on dissociation of molecules, it is likely that at low temperatures (140 °C), neither dissociation on nor transport/diffusion through the thicker films takes place. However, with Pt in conjunction with SiO2 or SnO2, the surface reactions will be altered, with enhanced NH3 selectivity as a result. A thin film of Al2O3, on the other hand, has a much smaller influence on the gas response to the test gases used in this work. Furthermore the sputtering process is found to strongly influence the sensor responses, and specifically reduce the sensitivity of the sensor. A thin intermediate layer of evaporated Pt does not completely protect the underlying structure from sputter induced damage. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 8. |
- Adrich, P., et al.
(författare)
-
Production of antihydrogen atoms by 6 keV antiprotons through a positronium cloud
- 2023
-
Ingår i: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 83:11
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the first production of an antihydrogen beam by charge exchange of 6.1 keV antiprotons with a cloud of positronium in the GBAR experiment at CERN. The 100 keV antiproton beam delivered by the AD/ELENA facility was further decelerated with a pulsed drift tube. A 9 MeV electron beam from a linear accelerator produced a low energy positron beam. The positrons were accumulated in a set of two Penning-Malmberg traps. The positronium target cloud resulted from the conversion of the positrons extracted from the traps. The antiproton beam was steered onto this positronium cloud to produce the antiatoms. We observe an excess over background indicating antihydrogen production with a significance of 3-4 standard deviations.
|
|
| 9. |
- Blumer, P., et al.
(författare)
-
Positron accumulation in the GBAR experiment
- 2022
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1040
-
Tidskriftsartikel (refereegranskat)abstract
- We present a description of the GBAR positron (e+) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H¯) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion (H¯+), which has been cooled to a low temperature, and observing the subsequent H¯ annihilation following free fall. To produce one H¯+ ion, about 1010 positrons, efficiently converted into positronium (Ps), together with about 107 antiprotons (p¯), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) × 109 positrons in 1100 s.
|
|
| 10. |
- Charlton, M., et al.
(författare)
-
Positron production using a 9 MeV electron linac for the GBAR experiment
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 985
-
Tidskriftsartikel (refereegranskat)abstract
- For the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN's Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5 x 10(7) slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux.
|
|
| 11. |
- Galstyan, V., et al.
(författare)
-
Fabrication of pure and Nb-TiO 2 nanotubes and their functional properties
- 2012
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 536:SUPPL.1, s. S488-S490
-
Tidskriftsartikel (refereegranskat)abstract
- TiO 2 and Nb-doped TiO 2 nanotubes were obtained on flexible polymeric substrates (Kapton HN) and alumina with high roughness (alumina substrate with granular surface). Nanotubes were prepared by electrochemical anodization of a Ti thick film. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the morphology of the structures and the roughness of the substrates. The functional properties of tubular arrays obtained on flexible and rough substrates were investigated towards two applications, namely, chemoresistive gas sensors and flexible dye sensitized solar cells. © 2011 Elsevier B.V. All rights reserved.
|
|
| 12. |
- Galstyan, V., et al.
(författare)
-
Fabrication of TiO 2 and TiO 2 nanotubular arrays and their gas sensing properties
- 2011
-
Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 25, s. 757-760
-
Tidskriftsartikel (refereegranskat)abstract
- Pure TiO 2 and TiO 2 nanotubular arrays were successfully sensitized. Nanotubular arrays were prepared by electrochemical anodization of thin films of Ti and of Ti-Nb deposited on alumina substrates with two different roughness. Morphological characterization and functional properties are presented. The gas sensing properties of TiO 2 and TiO 2 nanotubes with different gases have been tested in a wide range of operating temperatures. © 2011 Published by Elsevier Ltd.
|
|
| 13. |
- Husson, A., et al.
(författare)
-
A pulsed high-voltage decelerator system to deliver low-energy antiprotons
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1002
-
Tidskriftsartikel (refereegranskat)abstract
- The GBAR (Gravitational Behavior of Antihydrogen at Rest) experiment at CERN requires efficient deceleration of 100 keV antiprotons provided by the new ELENA synchrotron ring to synthesize antihydrogen. This is accomplished using electrostatic deceleration optics and a drift tube that is designed to switch from -99 kV to ground when the antiproton bunch is inside – essentially a charged particle “elevator” – producing a 1 keV pulse. We describe the simulation, design, construction and successful testing of the decelerator device at -92 kV on-line with antiprotons from ELENA.
|
|
| 14. |
|
|
| 15. |
- Kim, B. H., et al.
(författare)
-
Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment
- 2020
-
Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 137:2, s. 122-125
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment.
|
|
| 16. |
- Niang, S., et al.
(författare)
-
Accumulation of Positrons from a LINAC Based Source
- 2020
-
Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 137:2, s. 164-166
-
Tidskriftsartikel (refereegranskat)abstract
- The GBAR experiment aims to measure the gravitational acceleration of antihydrogen (H) over bar. It will use (H) over bar (+) ions formed by the interaction of antiprotons with a dense positronium cloud, which will require about 1010 positrons to produce one (H) over bar (+). We present the first results on the positron accumulation, reaching 3.8 +/- 0.4x10(8) e(+) collected in 560 s.
|
|
| 17. |
- 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.
|
|
| 18. |
- 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.
|
|
| 19. |
- 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.
|
|
| 20. |
- 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.
|
|
| 21. |
- Galstyan, V., et al.
(författare)
-
TiO 2 nanotubular and nanoporous arrays by electrochemical anodization on different substrates
- 2011
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 1:6, s. 1038-1044
-
Tidskriftsartikel (refereegranskat)abstract
- The preparation of nanotubular arrays on different substrates and nanoporous structures on titanium foil by means of electrochemical anodization of titanium layer has been investigated. Highly aligned nanotubes of TiO 2 on flexible, rough and flat substrates are reported. Modification of anodization conditions of titanium on specific substrates such as polyethylene terephthalate (PET), conducting glass and granular alumina was found to affect the morphology of TiO 2 nanotubes. Two different kinds of aqueous electrolytes have been applied, containing either glycerol or H 2SO 4, in order to investigate the effect of ion mobility on anodization process. Galvanostatic and potentiostatic anodization modes have been investigated: transition from nanotubes to nanoporous structures has been highlighted in galvanostatic mode, depending on the intensity of anodization current density. These results pave the way for massive production of TiO 2 nanotubes over, in principle, whatever substrate, enabling exploitation of new functional properties derived from the combination of tubes and substrates. This journal is © The Royal Society of Chemistry 2011.
|
|
| 22. |
- 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.
|
|
| 23. |
- Jimenez-Cadena, G., et al.
(författare)
-
Synthesis of different ZnO nanostructures by modified PVD process and potential use for dye-sensitized solar cells
- 2010
-
Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 124:1, s. 694-698
-
Tidskriftsartikel (refereegranskat)abstract
- Different ZnO nanostructures were synthesized by physical vapor deposition on glass-ITO substrates. Nanowires and nanosheets were obtained by a single step process using gold nanoparticles and gold thin films as catalyst. 3D nanoarchitectures were obtained by a two-step modified process; the morphology of these structures depends on the catalyst used for the second deposition: gold nanoparticles or zinc acetate seeds. All the nanostructures were characterized by SEM and TEM analyses, which showed the different morphology under same conditions of temperature, pressure, oxide precursor and deposition time. Dye-sensitized solar cells based on these ZnO structures were successfully assembled, using N179 as sensitizer with efficiencies between 0.1% and 0.5%. In spite of the low efficiency of the cells, a novel double PVD process is presented and its integration capability into solar cell devices has been proven. © 2010 Elsevier B.V. All rights reserved.
|
|
| 24. |
- 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.
|
|
| 25. |
- 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.
|
|
| 26. |
- 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.
|
|
| 27. |
- Sberveglieri, G., et al.
(författare)
-
Semiconducting tin oxide nanowires and thin films for Chemical Warfare Agents detection
- 2009
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 517:22, s. 6156-6160
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we report the preparation and structural characterization of tin oxide nanowires as functional materials for the development of chemical sensors. Aspects of material preparation relevant for gas sensing applications, such as the control of the wire diameter, are emphasized. The functional characterization is focused on the detection of Chemical Warfare Agents (CWAs) simulants, with particular regard to poisoning effects induced by dimethyl methyl phosphonate (DMMP), a simulant for Sarin nerve agent. Tin oxide thin films, prepared by means of rheotaxial growth and thermal oxidation (RGTO) technique, are used as reference to better compare the performance of nanowires with thin films traditionally used in gas sensing field. © 2009 Elsevier B.V. All rights reserved.
|
|
| 28. |
- Sberveglieri, G., et al.
(författare)
-
Synthesis and characterization of semiconducting nanowires for gas sensing
- 2007
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 121:1, s. 208-213
-
Tidskriftsartikel (refereegranskat)abstract
- Quasi one-dimensional nanostructures of semiconducting metal oxides are promising for the development of nano-devices. Tin, indium, and zinc oxides were produced in form of single-crystalline nanowires through condensation from vapor phase. Such a growth occurs in controlled thermodynamical condition and size reduction effects on the electrical and optical response to gases have been exploited. Preparation, microstructural, and electrical characterization of nanowires are presented and the peculiarities of these innovative structures are highlighted. © 2006 Elsevier B.V. All rights reserved.
|
|
| 29. |
- 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.
|
|
| 30. |
- Vomiero, Alberto, et al.
(författare)
-
In2O3 nanowires for gas sensors : morphology and sensing characterisation
- 2007
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:23, s. 8356-8359
-
Tidskriftsartikel (refereegranskat)abstract
- Thin and densely packed In2O3 nanowires have been synthesised on alumina substrates via transport and condensation method, starting from nanoparticles of indium or palladium as catalysts for the condensation process. Indium catalyst promoted wires growth according to vapour-solid (VS) mechanism, while palladium catalyst leads to wires formation based on vapour-liquid-solid (VLS) condensation. Electron microscopy and related diffraction analysis demonstrated that the wires are monocrystalline, with atomically sharp termination of the lateral sides, and are free from extended defects. The sensing properties of nanowires bundles have been tested to acetone using the flow through technique in the temperature range between 100 and 500 °C. © 2007 Elsevier B.V. All rights reserved.
|
|
| 31. |
- 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.
|
|
| 32. |
- Vomiero, Alberto, et al.
(författare)
-
One-dimensional nanostructured oxides for thermoelectric applications and excitonic solar cells
- 2012
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 1:3, s. 372-390
-
Tidskriftsartikel (refereegranskat)abstract
- Among the most interesting features offered by one-dimensional (1D) nanostructured oxides are their functional properties that can be usefully exploited in the field of energy conversion, in applications such as thermoelectrics and excitonic solar cells. Peculiar characteristics of 1D oxide structures with respect to polycrystalline or bulk counterpart, mainly related to their adjustable electronic conduction, render them strong candidates for the next generation of energy conversion devices. Furthermore, many of these materials are characterized by low-cost production, are non-toxic and relatively easy to produce, allowing a good perspective in large-scale assembly for the fabrication of end-user devices. In this paper we review the most recent achievements on 1D nanostructured oxides applied to thermoelectric devices and excitonic solar cells, highlighting the benefits offered by 1D shape on the functional properties of the devices and the possibility to manage energy transduction mechanisms in more efficient ways. © 2012 Elsevier Ltd.
|
|
| 33. |
- Vomiero, Alberto, et al.
(författare)
-
Preparation of radial and longitudinal nanosized heterostructures of in2O3 and SnO2
- 2007
-
Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 7:12, s. 3553-3558
-
Tidskriftsartikel (refereegranskat)abstract
- Radial and longitudinal nanosized In2O3-SnO 2 heterostructures were produced by applying a suitable methodology of transport and condensation. Sequential evaporation-condensation over In-seeded alumina promotes the formation of a radial heterostructure, driven by the direct vapor-solid growth mechanism. The single-crystalline In 2O3 nanowire nucleates and acts as the backbone for condensation of a polycrystalline SnO2 sheath. Fabrication of longitudinal heterostructures over sapphire is achieved through the application of a nanosized gold catalyst: the gold particles promote nucleation according to the vapor-liquid-solid mechanism, and lead to the formation of single-crystalline In2O3 nanowires with a gold droplet at the apex. Gold maintains its catalytic activity even during subsequent evaporation of SnO2 and induces the nucleation of a SnO2 single-crystal nanowire from the termination of an In2O3 nanowire. The electrical characterization of the longitudinally assembled In2O3-SnO2 structure highlighted a peculiar behavior, as the heterojunction of two n-type semiconducting oxides was revealed, tin oxide being reversely biased. These results hold great potential for the application of precisely shaped heterojunctions. © 2007 American Chemical Society.
|
|
| 34. |
- Vomiero, Alberto, et al.
(författare)
-
ZnO/ TiO2 nanonetwork as efficient photoanode in excitonic solar cells
- 2009
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 95:19
-
Tidskriftsartikel (refereegranskat)abstract
- An innovative nanonetwork composed of TiO2 nanoparticles and single-crystalline ZnO nanowires is demonstrated as efficient photoanode in excitonic solar cells. Such architecture benefits of the capability of high sensitizer loading offered by the nanoparticles and of the direct conduction path for electrons guaranteed by the nanowires. The combination of these features leads to improved light absorption, electron photogeneration, and charge collection. The nanonetwork was implemented in a dye-sensitized solar-cell architecture demonstrating threefold enhancement of the efficiency with respect to a nanowire photoanode of the same thickness. Cell efficiency of 1.6% was obtained in 1.5 μm thick nanonetwork. © 2009 American Institute of Physics.
|
|
| 35. |
- Waclawik, E.R., et al.
(författare)
-
Functionalised zinc oxide nanowire gas sensors: Enhanced NO 2 gas sensor response by chemical modification of nanowire surfaces
- 2012
-
Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 3:1, s. 368-377
-
Tidskriftsartikel (refereegranskat)abstract
- Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO2 produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO2 down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO2 compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ΔR/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ΔR/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2 target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles.
|
|
