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Lieberzeit, P.; Afzal, A.; Rehman, A.; Dickert, F. |
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Title |
Nanoparticles for detecting pollutants and degradation processes with mass-sensitive sensors |
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Journal Article |
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Year |
2007 |
Publication |
Sensors and Actuators B: Chemical |
Abbreviated Journal |
Sensors and Actuators B: Chemical |
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Volume |
127 |
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1 |
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132-136 |
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Keywords |
molecular imprinted polymer, MIP, recognition, quartz crystal microbalance, QCM, mass-sensitive sensor, detector |
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Abstract |
Compared with thin films, nanoparticle layers as coatings for QCM offer substantially increased interaction areas and sensitivities with favourable response times. Molybdenum disulphide (MoS2), e.g. has turned out to be a highly suitable material for interacting with thiols. The resulting materials are sufficiently soft according to Pearson to bind sulphur containing compounds reversibly. Depositing MoS2 nanoparticle submonolayers (particle size 200–300 nm) leads to an increase in sensor response by a factor of ten compared to a pure gold layer. Additionally, the nanoparticle layers show fully reversible sensor signals. Particle synthesis can also be combined with the molecular imprinting approach: by a precipitation technique, it is possible to generate molecularly imprinted TiO2 particles for engine oil degradation measurements. Compared with deposited thin layers, particles incorporate oxidised compounds from lubricants by a factor of two better. |
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0925-4005 |
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568 |
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Kampfrath, Tobias; Perfetti, Luca; von Volkmann, Konrad; Aguirre, Carla M.; Desjardins, Patrick; Martel, Richard; Frischkorn, Christian; Wolf, Martin |
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Title |
Optical response of single-wall carbon nanotube sheets in the far-infrared spectral range from 1 THz to 40 THz |
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Journal Article |
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2007 |
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Physica Status Solidi (B) |
Abbreviated Journal |
Phys. Stat. Sol. (B) |
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244 |
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11 |
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3950-3954 |
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single wall, carbon nanotube, SWNT, SWCNT, CNT, detector, sensor, TDS |
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The optical properties of single-wall carbon nanotube sheets in the far-infrared have been investigated with THz time-domain spectroscopy. Over a wide frequency range from 1 THz to 40 THz, the complex dielectric function of the nanotube sample has been derived. Our data can be excellently reproduced by a Drude-Lorentz model function. The extracted fit parameters such as Lorentz resonance frequency and plasma frequency are consistent with values obtained by scanning tunneling techniques. We discuss the origin of both the Lorentz and Drude contribution in terms of direct and indirect optical transitions. |
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0370-1972 |
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569 |
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Kawano, Yukio; Ishibashi, Koji |
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An on-chip near-field terahertz probe and detector |
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Journal Article |
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2008 |
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Nature Photonics |
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Nature Photon |
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2 |
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10 |
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618-621 |
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single molecule, terahertz, THz, near-field, microscopy, imaging, 2DEG, GaAs/AlGaAs, detector, applications |
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The advantageous properties of terahertz waves, such as their transmission through objects opaque to visible light, are attracting attention for imaging applications. A promising approach for achieving high spatial resolution is the use of near-field imaging. Although this method has been well established in the visible and microwave regions, it is challenging to perform in the terahertz region. In the terahertz techniques investigated to date, detectors have been located remotely from the probe, which degrades sensitivity, and the influence of far-field waves is unavoidable. Here we present a new integrated detection device for terahertz near-field imaging in which all the necessary detection components — an aperture, a probe and a terahertz detector — are integrated on one semiconductor chip, which is cryogenically cooled. This scheme allows highly sensitive, high-resolution detection of the evanescent field alone and promises new capabilities for high-resolution terahertz imaging. |
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1749-4885 |
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570 |
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Siddiqi, I.; Prober, D. E. |
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Nb–Au bilayer hot-electron bolometers for low-noise THz heterodyne detection |
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Year |
2004 |
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Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
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84 |
Issue |
8 |
Pages |
1404 |
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HEB, mixers, dynamic range, saturation, LO power, local oscillator power, Nb |
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The sensitivity of present Nb diffusion-cooled hot-electron bolometer (HEB) mixers is not quantum limited, and can be improved by reducing the superconducting transition temperature TC. Lowering TC reduces thermal fluctuations, resulting in a decrease of the mixer noise temperature TM. However, lower TC mixers have reduced dynamic range and saturate more easily due to background noise. We present 30 GHz microwave measurements on a bilayer HEB system, Nb–Au, in which TC can be tuned with Au layer thickness to obtain the maximum sensitivity for a given noise background. These measurements are intended as a guide for the optimization of THz mixers. Using a Nb–Au mixer with TC = 1.6 K, we obtain TM = 50 K with 2 nW of local oscillator (LO) power. Good mixer performance is observed over a wide range of LO power and bias voltage and such a device should not exhibit saturation in a THz receiver. |
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0003-6951 |
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571 |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Papa, D. C.; Hunter, T. R.; Paine, S. N.; Patt, F.; Gol'tsman, G.; Cherednichenko, S.; Voronov, B.; Gershenzon, E. |
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Superconductive hot-electron-bolometer mixer receiver for 800-GHz operation |
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Journal Article |
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Year |
2000 |
Publication |
IEEE Trans. Microw. Theory Techn. |
Abbreviated Journal |
IEEE Trans. Microw. Theory Techn. |
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Volume |
48 |
Issue |
4 |
Pages |
683-689 |
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NbN HEB mixers, LO power, local oscillator power, saturation, linearity, dynamic range |
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In this paper, we describe a superconductive hot-electron-bolometer mixer receiver designed to operate in the partially transmissive 350-μm atmospheric window. The receiver employs an NbN thin-film microbridge as the mixer element, in which the main cooling mechanism of the hot electrons is through electron-phonon interaction. At a local-oscillator frequency of 808 GHz, the measured double-sideband receiver noise temperature is TRX=970 K, across a 1-GHz intermediate-frequency bandwidth centered at 1.8 GHz. We have measured the linearity of the receiver and the amount of local-oscillator power incident on the mixer for optimal operation, which is PLO≈1 μW. This receiver was used in making observations as a facility instrument at the Heinrich Hertz Telescope, Mt. Graham, AZ, during the 1998-1999 winter observing season. |
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0018-9480 |
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RPLAB @ lobanovyury @ |
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573 |
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