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

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 Main Results

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

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

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

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

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

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

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

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

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

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 Results 12

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

SPCE Measurement 14

5 repeated scans at 0.84 V Run  SPCE ± ± ± ± ± ± ± ± ± ±0.3 First (red), second (blue), third (black), fourth (green), fifth (magenta) 15 Theta (deg.) Signal Intensity (V)

3 scans at 0.84 V Run  SPCE ± ± ± ± ± ± Theta (deg.) Signal Intensity (V)

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

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

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

Spin Coating Small volume of dye deposited on substrate Rotated at high speeds ( rpm) Result is thin, uniform coating 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

Smaller Step Scans 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 Theta (deg.) Signal Intensity (V)

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

Clockwise and Counter-clockwise scans at 1.0º step size Run  SPCE CW67.3 ± ± 0.3 CCW68.2 ± ± 0.3 Clockwise (red) and counterclockwise (black) 25 Signal Intensity (V) Theta (deg.)

Clockwise and Counter-clockwise scans at 0.2º step size Run  SPCE CW48.2 ± 0.1 CCW56.1 ± 0.1 Clockwise (red) and counterclockwise (black) 26 Theta (deg.) Signal Intensity (V)