UV Plasmonics

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UV Plasmonics

  1. 1. UV PlasmonicsF. Mahdavi, X. Jiao, M. Diwekar, S. Attavar, and Steve BlairElectrical and Computer Engineering University of Utah Photonics Research Group
  2. 2. Why UV? Label-free biomolecule detection via native fluorescence •  aromatic amino acids •  DNA •  excitation 220nm to 280nm •  emission 320nm to 370nm UV resonant Raman interactions •  ~105 more efficient than non-resonant Raman Photochemical reactions •  photodissociation/ionization •  photo-crosslinking •  disulphide bonds free thiol •  aryl azides, diazirine rings, and anthraquinones •  photo-isomerizationRay K, Chowdhury MH, Lakowicz JR (2007) Aluminum nanostructured films as substrates for enhanced fluorescence in the ultraviolet-blue spectral region. Analytical Chemistry 79:6480– 6487Chowdhury MH, Ray K, Gray SK, Pond J, Lakowicz JR (2009) Aluminum nanoparticles as substrates for metal- enhanced fluorescence in the ultraviolet for the label-free detection of biomolecules. Anal Chem 81:1397–1403Taguchi A, Hayazawa N, Furusawa K, Ishitobia H, Kawata S (2010) Deep-UV tip-enhanced Raman scattering. J. Raman Spectroscopy 40:1324-1330 Photonics Research Group
  3. 3. What are the challenges? Materials •  high plasma frequency (> 7eV): Al, Ag, Au •  damping, interband transitions: Ag, Au •  surface modification schemes (Al, oxide) Absorption spectroscopy •  low absorption cross-sections (220nm – 280nm) Fluorescence spectroscopy •  low quantum yields •  “brightness” ~100x lower than organic dye labelsRay K, Chowdhury MH, Lakowicz JR (2007) Aluminum nanostructured films as substrates for enhanced fluorescence in the ultraviolet-blue spectral region. Analytical Chemistry 79:6480– 6487Chowdhury MH, Ray K, Gray SK, Pond J, Lakowicz JR (2009) Aluminum nanoparticles as substrates for metal- enhanced fluorescence in the ultraviolet for the label-free detection of biomolecules. Anal Chem 81:1397–1403Taguchi A, Hayazawa N, Furusawa K, Ishitobia H, Kawata S (2010) Deep-UV tip-enhanced Raman scattering. J. Raman Spectroscopy 40:1324-1330 Photonics Research Group
  4. 4. Materials •  Figure of merit – β’/β’’ for SPP @ metal – air interface •  Al has best response into the UVRay K, Chowdhury MH, Lakowicz JR (2007) Aluminum nanostructured films as substrates for enhanced fluorescence in the ultraviolet-blue spectral region. Analytical Chemistry 79:6480– 6487Aslan K, Previte MJR, Zhang Y, Geddes CD (2008) Surface plasmon coupled fluorescence in the ultraviolet and visible spectral regions using zinc thin films. Analytical Chemistry 80:7304– 7312 Photonics Research Group
  5. 5. Materials •  Figure of merit – ε’/ε’’ for sphere LSP @ metal – air interface •  Al has best response into the UV •  Zn has also been used in some studiesRay K, Chowdhury MH, Lakowicz JR (2007) Aluminum nanostructured films as substrates for enhanced fluorescence in the ultraviolet-blue spectral region. Analytical Chemistry 79:6480– 6487Aslan K, Previte MJR, Zhang Y, Geddes CD (2008) Surface plasmon coupled fluorescence in the ultraviolet and visible spectral regions using zinc thin films. Analytical Chemistry 80:7304– 7312 Photonics Research Group
  6. 6. UV Plasmonic Structures bow-tie antenna Data and image courtesy of Dr. Reuven Gordon, U. Victoria(dual polarization) bullseye Photonics Research Group
  7. 7. UV Plasmonic Structures Data and image courtesy of Dr. Reuven Gordon, U. Victoria Photonics Research Group
  8. 8. UV Plasmonic Structures Data and image courtesy of Dr. Reuven Gordon, U. Victoria Photonics Research Group
  9. 9. UV Enhancement - aperture Al Au Ag 50nm aperture diameter, 100nm thicknessF. Mahdavi and S. Blair, “Nanoaperture fluorescence enhancement in the ultraviolet,” Plasmonics 5, 169-174 (2010) Photonics Research Group
  10. 10. Fluorescence Enhancement fluorescence emission κ = collection efficiency k rad φ= = quantum efficiency krad + k nrad σI e krad ,knrad = radiative, non - radiative rates CRM = κφ σ = absorption cross - section 1+ Ie /Ie Ie = excitation intensity ktot Is = = saturation intensity σ (1+ kisc /kd )€ there are two limits in excitation CRM I → κφσIe e <<I sat € CRM I → κφσIs ≈ κk rad e >>I sat a “universal” emission enhancement factor can be defined κkrad measured fluorescence signal €   T F ( t ) = ∫ CRM ( r )C ( r ,t ) dr 3 F= ∫ F(t)dt 0 where C(r,t) is the concentration and T the integration time S. Blair and J. Wenger, “Enhancing fluorescence with sub-wavelength metallic apertures,” in Metal Enhanced Fluorescence, ed. by Chris Geddes (2008) Photonics Research Group €
  11. 11. UV Enhancement - nanoaperture Tryptophan – native quantum efficiency ~ 13%F. Mahdavi and S. Blair, “Nanoaperture fluorescence enhancement in the ultraviolet,” Plasmonics 5, 169-174 (2010) Photonics Research Group
  12. 12. UV Enhancement - nanoaperture Tryptophan – native quantum efficiency ~ 13%F. Mahdavi and S. Blair, “Nanoaperture fluorescence enhancement in the ultraviolet,” Plasmonics 5, 169-174 (2010) Photonics Research Group
  13. 13. UV EnhancementF. Mahdavi and S. Blair, “Nanoaperture fluorescence enhancement in the ultraviolet,” Plasmonics 5, 169-174 (2010) Photonics Research Group
  14. 14. UV EnhancementF. Mahdavi and S. Blair, “Nanoaperture fluorescence enhancement in the ultraviolet,” Plasmonics 5, 169-174 (2010) Photonics Research Group
  15. 15. Controlling Photochemical Reactions light-directed capture molecule attachment •  ATFB – photoactivated cross-linker •  forms aryl nitrene under UV (365nm) •  highly reactive – insertion into C-H or N-H bonds •  attach biotinylated probeS. Attaver, M. Diwekar and S. Blair, “Photoactivated capture molecule immobilization in plasmonic nanoapertures inthe ultraviolst,” to appear Lab on a Chip (2011) Photonics Research Group
  16. 16. Large Area Plasmonic SubstratesWorking with Utah company – MOXTEK•  adapt existing manufacturing process for wire-grid polarizers•  process currently developed for Al•  must develop new passivation methodsProduce 1” x 3” microarray substrates•  can work with off the shelf instruments•  e.g. spotters, hybridization systems, scanners Photonics Research Group
  17. 17. Passivating Aluminum Substrates Need chemistry to prevent silanization of aluminum oxide layer Phosphonic and carboxylic acids •  attach to many metal oxides •  can prevent attachment to SiO2 After treatment, can directly silanizeS. Attavar, M. Diwekar, M. R. Linford, M. Davis, and S. Blair “Passivation of aluminum with alkyl phosphonic acidsfor biochip applications,” submitted to Applied Surface Science (2010) Photonics Research Group
  18. 18. Passivating Aluminum Substratesmolecule O(cta)D(ecyl)PA D(ecly)PA B(utyl)PA nonecontact ang Al film 116 103 83 ~10 Al array 114 97 ~25SIMSimagespassivation 450:1 200:1 N/Aratio Al + Silane Al + DPA Array + DPA Photonics Research Group
  19. 19. Passivating Aluminum Substratesmolecule O(cta)D(ecyl)PA D(ecly)PA B(utyl)PA nonecontact ang Al film 116 103 83 ~10 Al array 114 97 ~25SIMSimagespassivation 450:1 200:1 N/Aratio PO2- SiCO2H3 PO3- Photonics Research Group
  20. 20. Controlling Photochemical Reactions light-directed capture molecule attachment •  ATFB – photoactivated cross-linker •  forms aryl nitrene under UV (365nm) •  highly reactive – insertion into C-H or N-H bonds •  attach biotinylated probeS. Attaver, M. Diwekar and S. Blair, “Photoactivated capture molecule immobilization in plasmonic nanoapertures inthe ultraviolst,” to appear Lab on a Chip (2011) Photonics Research Group
  21. 21. Enhanced Photochemical Reaction Rate 550nm/200nm 650nm/250nm 500nm/200nm •  3.2x intensity enhancement @ 365nmS. Attaver, M. Diwekar and S. Blair, “Photoactivated capture molecule immobilization in plasmonic nanoapertures inthe ultraviolst,” to appear Lab on a Chip (2011) Photonics Research Group
  22. 22. UV Enhancement 550nm/200nm 650nm/250nm 500nm/200nmS. Attaver, M. Diwekar and S. Blair, “Photoactivated capture molecule immobilization in plasmonic nanoapertures inthe ultraviolst,” to appear Lab on a Chip (2011) Photonics Research Group
  23. 23. Enhanced Red FluorescenceS. Attaver, M. Diwekar and S. Blair, “Photoactivated capture molecule immobilization in plasmonic nanoapertures inthe ultraviolst,” to appear Lab on a Chip (2011) Photonics Research Group
  24. 24. Enhanced Red Fluorescence 8.2x 6.1x 3.3xS. Attaver, M. Diwekar and S. Blair, “Photoactivated capture molecule immobilization in plasmonic nanoapertures inthe ultraviolst,” to appear Lab on a Chip (2011) Photonics Research Group
  25. 25. OutlookBuilding blocks in place•  materials (e.g. Al)•  antenna designs•  nanofabrication•  surface modificationPossible applications•  label-free real-time binding arrays•  biomolecule analysis•  nanolithographyQuestion•  can we develop better materials? Photonics Research Group

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