| 1. |
- Alm, Oscar, et al.
(författare)
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Tungsten oxide nanoparticles synthesised by laser assisted homogeneous gas-phase nucleation
- 2005
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 247:1-4, s. 262-267
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten oxide nanoparticles were generated by excimer (ArF) laser assisted chemical vapor deposition from WF6/H2/O2/Ar gas mixtures. The deposited particles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The deposition rate as a function of the partial pressures of the reactants and of the laser fluence was measured by X-ray fluorescence spectroscopy. The mean diameter of the deposited tungsten oxide particles varied with the experimental parameters and was typically 23 nm. Particles with a higher degree of crystallinity were observed at a laser fluence exceeding 130 mJ/cm2, and X-ray amorphous particles were obtained below 110 mJ/cm2. The amorphous tungsten oxide had a stoichiometry ranging from WO2.7 to WO3. Deposits were formed only when hydrogen was present in the gas mixture.
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| 2. |
- Bittencourt, C., et al.
(författare)
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Evaporation of WO3 on Carbon Nanotube Films : a new hybrid film
- 2006
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Ingår i: Smart materials and structures. - : IOP Publishing. - 0964-1726 .- 1361-665X. ; 15:6, s. 1555-1560
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid WO3-CNT ( carbon nanotube) films were prepared in two steps: in the first step, the drop coating method was employed for coating silicon substrates with a MWCNT (multiwalled CNT) film prepared with oxygen plasma functionalized MWCNTs; in the second step, a layer of WO3 nanoparticles was deposited over the MWCNT film by using an advanced gas deposition unit. The WO3 nanoparticles are formed by condensation. SEM images show that the morphology of the hybrid films is characterized by an overlayer formed from WO3 particles anchored at the surface of a well-dispersed MWCNT underlayer. TEM images show that the hybrid films are composed of a WO3 matrix supported through a dispersed mesh of CNTs-the CNTs act as internal pillars. This morphology increases the surface area for gas interaction.
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| 3. |
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| 4. |
- Elihn, Karine, et al.
(författare)
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Size and structure of nanoparticles formed via ultraviolet photolysis of ferrocene
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:3, s. 034311-
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Tidskriftsartikel (refereegranskat)abstract
- Iron nanoparticles enclosed in carbon shells were formed by laser-assisted chemical vapor decomposition of ferrocene (Fe(C5H5)2) vapor in Ar gas atmosphere. The particle size dependence on the total ambient gas pressure and on laser fluence of the pulsed ArF excimer laser was examined and, e.g., an effective size decrease of the iron core was observed at elevated laser fluences. Characterizations of the iron and carbon microstructures were performed by x-ray diffraction and transmission electron microscopy, while relative iron deposition rates were measured by x-ray fluorescence spectroscopy. Both -Fe and -Fe phases were found for the single crystalline iron cores, surrounded by graphitic (inner) and amorphous (outer) carbon layers. The temperature rise of the laser-excited particles was also determined by optical spectroscopy of the emitted thermal radiation, which allowed an estimation of the iron loss of the nanoparticles due to evaporation. The estimated and measured iron losses are in good agreement.
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| 5. |
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| 6. |
- Espinosa, E. H., et al.
(författare)
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Highly Selective NO2 Gas Sensors made of MWCNTs and WO3 Hybrid Layers
- 2007
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 154:5, s. J141-J149
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid gas sensors were fabricated by means of multiwalled carbon nanotubes (MWCNTs) covered by W O3 deposited by an advanced reactive gas deposition method. In order to increase the dispersion of nanotubes and attach functional groups to their surface so as to enhance their compatibility with other compounds, the MWCNTs were functionalized in two different radio-frequency plasmas (oxygen or hydrogen) under different operating conditions. X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy were employed to analyze the composition and morphology of the hybrid films. Gas sensors based on such films were found to be very selective to N O2 when operated at room temperature. No cross-sensitivity was found to other hazardous gases such as N H3 or CO.
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| 7. |
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| 8. |
- Heszler, Peter
(författare)
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A comparative study of an analogue optical Fourier transform quantum computer working in entanglement and non-entanglement mode
- 2006
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Ingår i: Fluctuation and Noise Letters. - 0219-4775 .- 1793-6780. ; 6:4, s. L433-L446
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Tidskriftsartikel (refereegranskat)abstract
- A gedanken model of an analog optical computer for general purpose Fourier transform tasks is built and studied assuming entangled or non-entangled photons appearing at the input. The performance of the entangled and non-entangled operation modes, regarding information content, power consumption, acquisition time, wavelength and bandwidth limitations are analyzed as function of qubit repetition rate and number of qubits in the entangled state, respectively, based on fundamental physical laws. The total number of input photons is assumed the same for the two operation modes. It is sown that the entangled mode outperforms the non-entangled one, but only above a certain number of qubits in the entangled state. It is argued that, for practical applications to general purpose computing, several limitations should be imposed regarding qubit repetition rate and number of qubits in the entangled state. In addition, it is pointed out that the conclusions that we present are equally valid for general purpose optical quantum computing and for quantum information processing, too.
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| 9. |
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| 10. |
- Kwan, Chiman, et al.
(författare)
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Advanced agent identification with fluctuation-enhanced sensing
- 2008
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 8:5-6, s. 706-713
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Tidskriftsartikel (refereegranskat)abstract
- Conventional agent sensing methods normally use the steady state sensor values for agent classification. Many sensing elements (Hines et al., 1999, Ryan et al., 2004, Young et al.,, 2003, Qian et al., 2004, Qian et al.,, 2006, Carmel et ad., 2003) are needed in order to correctly classify multiple agents in mixtures. Fluctuation-enhanced sensing (FES) looks beyond the steady-state values and extracts agent information from spectra and bispectra. As a result, it is possible to use a single sensor to perform multiple agent classification. This paper summarizes the application of some advanced algorithms that can classify and estimate concentrations of different chemical agents. Our tool involves two steps. First, spectral and bispectral features will be extracted from the sensor signals. The features contain unique agent characteristics. Second, the features are fed into a hyperspectral signal processing algorithm for agent, classification and concentration estimation. The basic idea here is to use the spectral/bispectral shape information to perform agent classification. Extensive simulations have been performed by using simulated nanosensor data, as well as actual experimental data using commercial sensor (Taguchi). It was observed that our algorithms are able to accurately classify different agents, and also can estimate the concentration of the agents. Bispectra contain more information than spectra at the expense of high-computational costs. Specific nanostructured sensor model data yielded excellent performance because the agent responses are additive with this type of sensor. Moreover, for measured conventional sensor outputs, our algorithms also showed reasonable performance in terms of agent classification.
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