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Applications of SPCE to Pharmaceutical Research

Applications of SPCE to Pharmaceutical Research. Kathleen Hamilton, Tom Laue, and James Harper Presentation at the 2007 BITC Meeting University of New Hampshire Durham, New Hampshire July 12, 2007. Main Results. A compact apparatus has been constructed to measure SPCE signals

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Applications of SPCE to Pharmaceutical Research

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  1. Applications of SPCE to Pharmaceutical Research • Kathleen Hamilton, Tom Laue, and James Harper • Presentation at the 2007 BITC Meeting • University of New Hampshire • Durham, New Hampshire • July 12, 2007

  2. Main Results • A compact apparatus has been constructed to measure SPCE signals • Depending on step size, a full 180˚ scan can be completed in < 5 minutes • Reproducible scans can be made with resolutions up to 0.5˚ • SPCE signals have been measured with novel material sets 2

  3. Outline • Introduction to SPCE • Description of an automated apparatus • Results • Future Direction

  4. SPCE • SPCE uses surface plasmons for emission at wavelength dependent angles • Fluorescing molecules above a metal will induce plasmons in the metal • Plasmons will couple to photons via glass interface 4

  5. SPCE generation(Reverse Kretschmann configuration) • Incident light excites fluorescence • Fluorescing molecules induce plasmons on metal surface • Plasmons are coupled to photons at glass interface • Resulting light is emitted at angles determined by plasmon wavenumber 5

  6. Sample Preparation a: adhesion layer b: passivation layer • Two Components • Thin films deposited by sputtering • Thin fluorescent dye deposited by spin coating 6

  7. Sputter Deposition • Physical vapor deposition • Deposition under vacuum reduced impurities in films • Rotation of substrate creates films of uniform thickness • Reactive gas sputtering creates material for passivation layer 7

  8. Apparatus Design and Construction • Three Mechanical Components • Excitation • Rotation • Detection • Computer Interface and Control (LabVIEW) 8

  9. Excitation with 5 mW laser (  = 532 nm) • Driven by 2.85 V (DC) • Beam divergence < 0.069˚ 9

  10. Rotational motion is driven by a stepper motor • Step resolution: 0.0281º • Accuracy: <1º • Repeatability: < 0.1º 10

  11. 200 µm aperture amplifier Wavelength filter PMT • Fluorescence detection is made by a photomultiplier Amplifier is needed to convert PMT output from current to voltage 11

  12. Results • Repeatable measurements are possible with angular resolution of 0.5° • Depending on step size, a full 180º scan can be completed in < 5 minutes • SPCE has been measured from different material sets 12

  13. Geometry of an SPCE scan • Scans begin at 0˚ and traces out an angle  • Peaks are measured in two regions:  < 90˚ and  > 90˚

  14. SPCE Measurement 14

  15. 5 repeated scans at 0.84 V Signal Intensity (V) Theta (deg.) First (red), second (blue), third (black), fourth (green), fifth (magenta) 15

  16. 3 scans at 0.84 V Signal Intensity (V) Theta (deg.) 16

  17. Repeated Scan Characteristics • Angular Reproducibility • Variant peaks at same voltage • Altering the voltage of consecutive scans led to uniformity 17

  18. Conclusions • The apparatus provides a way to measure the fluorescent signal from a thin dye layer • Dimensions of apparatus: 18’’L x 12’’D x 10’’H • Measurements are made quickly and accurately • Three-film stacks can be created by two magnetron sources

  19. Future Work • Adaption to biological applications • Incorporation of microfluidics • Improve angular sensitivity • Improve fluorescence intensity consistency

  20. Spin Coating • Small volume of dye deposited on substrate • Rotated at high speeds (2200-3000 rpm) • Result is thin, uniform coating 21

  21. Higher Resolution Scans • Previous scans were made with step sizes of 1.0º • Scans were made with smaller step sizes, 0.75º, 0.5º, 0.25º, 0.2º, 0.1º • Step sizes > 0.5º show similar angular reproducibility as the 1.0º step size scans • Step sizes < 0.5º show poor angular reproducibility 22

  22. Smaller Step Scans Signal Intensity (V) Signal Intensity (V) Theta (deg.) Theta (deg.) Left: Step sizes of 1.0º (red), and 0.5º (black) Right: Step sizes of 0.1˚ (black), 0.15˚ (blue), and 0.2˚ (red) 23

  23. Reverse Scans • Second LabVIEW program written executes two scans • First scan done in clockwise direction • Second scan done in counter-clockwise direction • Angular resolution is the same for both directions • Reversed direction scans were done to check angular reproducibility 24

  24. Clockwise and Counter-clockwise scans at 1.0º step size Signal Intensity (V) Theta (deg.) Clockwise (red) and counterclockwise (black) 25

  25. Clockwise and Counter-clockwise scans at 0.2º step size Signal Intensity (V) Theta (deg.) Clockwise (red) and counterclockwise (black) 26

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