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  • 1
    Electronic Resource
    Electronic Resource
    Infrared characterization of amorphous and polycrystalline D2O ice on controlled wettability self-assembled alkanethiolate monolayers (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 3038-3048 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared reflection–absorption spectroscopy has been used to characterize thin overlayers (1–200 Å) of D2O ice deposited in UHV onto a set of self-assembled alkanethiolate monolayers (SAMs) of controlled wettabilities on gold. The SAMs were prepared from a series of controlled composition, mixed solutions of HS(CH2)15CH3 and HS(CH2)16OH, making it possible to investigate the whole wettability range from θ(approximate)0° to θ=112°, where θ is the static contact angle with water. Dosing of D2O and infrared measurements were carried out at selected sample temperatures between 82 and 150 K. Experimental spectra of ice overlayers recorded below 100 K on all SAM substrates are in good agreement with simulated reflection–absorption spectra, derived from the optical constants of amorphous ice. This agreement allows accurate film thickness determination. In contrast, lack of correspondence in spectral signature is noted between the spectra of annealed films and simulated polycrystalline (or amorphous) ice spectra. We interpret this discrepancy to suggest that significant substrate-induced differences between thin overlayers and bulk ice persist in the latter case. Spectral indications of ice–substrate interaction are also seen for amorphous ice, and are especially prominent in the case of highly hydrophobic (pure CH3-terminated, θ=112°) substrates. In this case the substrate effect extends up to an average film thickness (150–200 Å) corresponding to ∼50 ice monolayers, in contrast to highly hydrophilic OH-terminated substrates where the substrate effects appear to vanish beyond ∼5 monolayers (15–20 Å average thickness). Annealing of thin ice overlayers (2–3 monolayers) clearly demonstrates a strong correlation between the onset as well as progression of the transition from amorphous to polycrystalline ice and the exact substrate wettability or chemical composition. The data further suggest the existence of metastable intermediate forms, that are neither purely amorphous nor polycrystalline. We discuss these observations in terms of substrate–overlayer interaction. A tentative "phase diagram" summarizing these results is presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473049
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  • 2
    Electronic Resource
    Electronic Resource
    Imaging surface plasmon resonance sensor based on multiple wavelengths: Sensitivity considerations (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3530-3538 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new, multiple wavelength surface plasmon resonance apparatus for imaging applications is presented. It can be used for biosensing, e.g., for monitoring of chemical and biological reactions in real time with label-free molecules. A setup with a fixed incident angle in the Kretschmann configuration with gold as the supporting metal is described, both theoretically and experimentally. Simulations of the sensor response based on independently recorded optical (ellipsometric) data of gold show that the sensitivity for three-dimensional recognition layers (bulk) increases with increasing wavelength. For two-dimensional recognition layers (adlayer) maximum sensitivity is obtained within a limited wavelength range. In this situation, the rejection of bulk disturbances, e.g., emanating from temperature variations, decreases, with increasing wavelength. For imaging surface plasmon resonance the spatial resolution decreases with increasing wavelength. Hence, there is always a compromise between spatial resolution, bulk disturbance rejection, and sensitivity. Most importantly, by simultaneously using multiple wavelengths, it is possible to maintain a high sensitivity and accuracy over a large dynamic range. Furthermore, our simulations show that the sensitivity is independent of the refractive index of the prism. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287631
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  • 3
    Electronic Resource
    Electronic Resource
    Difference in hydrogen sensitivity between Pt and Pd field-effect devices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4275-4280 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An explanation is given for the large differences in the hydrogen sensitivity in air observed for gas sensitive field-effect devices with palladium and platinum gates, respectively. It is demonstrated that this difference is mainly due to a difference in the hydroxyl formation rate between the two metals. The water production rates are, however, almost the same for the two metals. The considerably smaller sensitivity of platinum devices in air is then due to the much lower steady-state hydrogen atom concentration on the platinum surface compared with the palladium surface. This leads to a smaller coverage of hydrogen atoms at the metal–oxide interface and thus a smaller response of the device at a given hydrogen concentration in air. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1448874
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  • 4
    Electronic Resource
    Electronic Resource
    Reversible hydrogen annealing of metal-oxide-silicon carbide devices at high temperatures (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3203-3205 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a reversible hydrogen annealing effect observed in platinum–silicon dioxide–silicon carbide structures at temperatures above about 650 °C. It appears as a decrease of the inversion capacitance in the presence of hydrogen. This phenomenon is shown to depend on hydrogen atoms, created on the catalytic metal, that pass through the oxide and interact with charge generation sites at the oxide–silicon carbide interface. The consequence of the observation for chemical sensors based on silicon carbide is discussed. The results are phenomenological, since no details of the annealing chemistry could be developed from the present experiments. We find, however, that the annealing process and its reversal have activation energies of about 0.9 eV and 2.9 eV/site, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115163
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  • 5
    Electronic Resource
    Electronic Resource
    Generation of response maps of gas mixtures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6953-6961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large area field effect structures with thin catalytic metal gates can be used to generate two dimensional images of the response of the metal to gas mixtures. This is done by using a scanning light pulse technique to determine polarization changes occurring in the thin metal film due to chemical reactions on the metal. Such images appear to be a new concept in chemical sensing. The present contribution is a first attempt to predict the shape of these images. We show that the occurrence of maxima in the response at certain points on the surface is most likely due to temperature dependent chemical rate constants and to the consumption of molecules on the catalytic metal surface. Experimental results of the detection of methanol, ethanol, and hydrogen on palladium and platinum, with a temperature gradient along the metals, are used to support the theoretical arguments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355045
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of creatinine by an ammonia-sensitive semiconductor structure and immobilized enzymes (1986)
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 145-148 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00292a035
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  • 7
    Electronic Resource
    Electronic Resource
    Palladium gate metal-oxide-semiconductor oxygen sensors (1990)
    s.l. : American Chemical Society
    Analytical chemistry 62 (1990), S. 542-544 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00204a023
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  • 8
    Electronic Resource
    Electronic Resource
    New observation on thin discontinuous metal films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 420-421 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown from the capacitance-voltage curves of metal-insulator-semiconductor structures that molecular species in an electrolyte interact with thin discontinuous, hydrophobic platinum films in a way similar to that in a gas phase. It is suggested that this is due to the presence of air volumes in the cracks of the discontinuous metal. This suggestion is supported by theoretical models for the wetting of thin films. The observation may have implications for the use of thin metal layers as the sensing material in chemical sensors for molecular species in solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111117
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  • 9
    Electronic Resource
    Electronic Resource
    The Reflectometer: (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 501 (1987), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1987.tb45779.x
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  • 10
    Electronic Resource
    Electronic Resource
    Orientation of a tripeptide on platinum (1990)
    s.l. : American Chemical Society
    Langmuir 6 (1990), S. 1551-1557 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00100a005
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