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Optical Nanoparticle Trapping Sensor Darryl Benally†, Dr. Matt Kipper*‡, Dr. Randy Bartels†‡ †Department of Electrical Engineering, *Department of Chemical and Biological Engineering, ‡School of Biomedical Engineering Colorado State University, Fort Collins Colorado Project Goal We are developing novel biosensor design and strategies based on the binding of target analytes to gold nanoparticles. The first strategy is using an evanescent wave induced by surface plasmon resonance in a thin conducting film. Which will be placed near a dielectric interface to concentrate gold nanoparticles and gold nanoparticle attached bacteriophages. The concentrated nanoparticles will be probed using differential spectroscopy for detection. The second is to use heterdyne photothermal spectroscopy. The method will use the gold nanoparticle’s ability to absorb light in the visible green light spectrum. The absorbed light energy will be frequency modulated and converted to heat. Thus, making a time-modulated variation of the refractive index. A probe beam will be introduced causing a scattering field for detection. The technique used is called Laser Induced Scattering around a NanoAbsorber (LISNA). First Strategy (Not to Scale) Gaussian Beam Shape Polarizable Particle Evanescent Field Decay 532 nm Frequency Doubled Nd: YAG Laser Beam 2nd Strategy Dichroic Mirror Microscope Objective Microscope Objective x40 NA: 0.65 632.8 nm He-Ne Probe Laser Beam x40 NA: 0.65 Sample Lock-in Amplifier Results Second Strategy Frequency Modulated Green Beam 530 [nm] Dispersion Modulation 632.8 [nm] Image of gold nanoparticles using second strategy from CCD Signal [a.u.] Laser spectral width Photodiode Conclusion Reflected Radiation Reflected Radiation FSCAT 30 Lens Prism 532 nm Frequency Doubled Nd: YAG Laser Beam Incident TM Radiation Nonresonant Probe Red Beam Dichroic Mirror AOM Total Internal Reflection (TIR) FGRAD Ocean Optics USB 4000 Spectrometer Rotational Stage FSCAT X Incident TM Radiation White LED 1st Strategy Z Light Source for Absorption Spectrum Gaussian Beam Shape FGRAD Experimental Set Up 40 50 Time [s] 60 70 Measurered signal with and without the 532 nm frequency modulated laser beam • Verified the heterodyne photothermal experiment • Analyze and investigate measurement from the heterodyne photothermal experiment • Develop technique to determine gold nanoparticle size from both the image and photothermal measurement • Modify the “puck” design for greater angle acceptance •Continue with SPR and photothermal experiments Acknowledgements •Dr. Kipper’s Lab Group •Dr. Bartell’s Lab Group •Christopher Killingsworth
