1. Gold Nanorod Biosensors and Single Particle Spectroscopy Jason H. Hafner MURI site visit July 27, 2005

2. Gold Nanorods longitudinal transverse -Sharp, localized plasmon resonance. -Molecular size in short dimension

3. Localized Surface Plasmon Resonance Sensors Silver nanoparticles on substrate Antibodies conjugated to nanoparticles. wavelength absorbance

4. Localized Surface Plasmon Resonance Sensors wavelength absorbance Upon analyte binding, the resonance wavelength shifts: Silver nanoparticles on substrate By Nanosphere Lithography Antibodies conjugated to nanoparticles.

5. Localized Surface Plasmon Resonance Sensors Haes, Van Duyne Exper Rev. Mol. Diagn. 4, p. 528 (2004). -Simple physical mechanism: no surface enhancement, no aggregation. -Low cost technology: label-free, no purification or amplification of analyte. Use Gold Nanorods: More facile surface chemistry (gold). Entire substrate created by self assembly. Elongated shape and small size increases sensitivity (higher nm/RIUs).

6. Seed-Mediated, Surfactant Directed Gold colloid grows while surrounded by a surfactant bilayer which regulates the growth rate… Gold Nanorods Synthesis N + Br - CTAB Murphy, Langmuir 20, p. 6414 (2004). … a defect forms with poor surfactant binding to create anisotropic growth… … which results in an elongated structure. 50 mL of nanorod solution with OD=2 can be produced, but it is only stable in saturated surfactant.

7. PEG-SH displaces the CTAB, creating a strongly-bound buffer layer so nanorods may be put in arbitrary solutions. Nanorod PEGylation + 5000 MW PEG-thiol 400 500 600 700 800 900 1000 Nanorods in CTAB Nanorods in buffer PEG-Nanorods in buffer

8. Nanorod-Antibody Conjugation LC-SPDP IgG conjugated nanorods bind a complementary strip plate (left), while nanorods that are only PEGylated do not (right). +

9. Absorbance of Nanorods on a glass substrate 50:15 = 4.4 +/- 0.5 x 10 9 cm -1 M -1. air water SPR sensitivity = 150 nm/RIU (similar to nanosphere lithography)

10. 750.1 +/- 0.3 nm Gold Nanorod Biosensors

11. 750.1 +/- 0.3 nm 759.6 +/- 0.3 nm Gold Nanorod Biosensors

12. 750.1 +/- 0.3 nm 759.6 +/- 0.3 nm 763.0 +/- 0.2 nm Gold Nanorod Biosensors

13. Single Particle Spectroscopy To camera, CCD spectrometer, InGaAs spectrometer. Individual Gold Nanoshells, Dark Field 1. Determine more accurate optical properties of nanostructures. 2. Study complex nanostructure shapes. 3. Characterize tips for near field microscopy. 4. Find ultimate limit of LSPR biosensing. Completely removes effects of structural inhomogeneity

14. Size Dependent Dielectric Function = scattering rate = e-e + e-ph + e-d

15. Size Dependent Dielectric Function = scattering rate = e-e + e-ph + e-d + e-surface A = broadening parameter, depends on nature of surface scattering. A = 1, high dephasing A = 0, no dephasing

16. Bulk: A=1 Single: A=0 Nanoshell Line Width

17. Single Molecule LSPR Sensing? time peak Inject analyte *Analytes (proteins) similar size to nanoparticle. *Elongated particles: optimized for LSPR. *Admit analyte at very low concentration. *Observe spectral shifts at a rapid rate.

18. Solution: Gold Nanostars!

19. 400 1000 Wavelength (nm) Scattering Bulk Complicated particle shapes cant be made monodisperse. Single Particle Spectra reveal their optical properties. Solution: Gold Nanostars! Nanostars: large scattering cross section and sharp resonance.

20. Water n=1.33 Sucrose n=1.45 Nanostar LSPR Shift Oil n=1.52 584 nm / RIU279 nm / RIU

21. Single Nanostar LSPR Sensing Functionalization of gold nanostars with 16-mercaptohexadecanoic acid.

22. To camera, CCD spectrometer, InGaAs spectrometer. NSOM Tip Characterization