Zang Trace Explosives Detection Presentation


Published on

Published in: Technology, Business
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Zang Trace Explosives Detection Presentation

  1. 1. Organic Semiconductor Nanowires:<br />1D Enhanced Optoelectronic Properties<br />&<br />Applications in Vapor Sensing<br />Ling Zang, USTAR Prof.<br />Department of Materials Science and Engineering<br />Director, Utah Center of Trace Explosives Detection (UCTED) <br /><br />
  2. 2. 1D self-assembly through solution or surface processing <br />Zang et al. Accounts of Chemical Research,  2008, <br />Special Issue on Nanoscience, vol. 41, pp1596-1608.<br />
  3. 3. Advantages of Organic Materials:<br /><ul><li>Unlimited choices of molecules: electronic structure (color), configuration, size, shape …
  4. 4. Easy to modify: chemical interactions.
  5. 5. Flexible for processing: vapor, liquid/solution, solid.
  6. 6. Adaptable to various substrate.
  7. 7. Cheap for manufacturing, processing, packaging.
  8. 8. …</li></li></ul><li>Organic Semiconductors: perspectives and challenges<br />nanowires, nanodevices, optoelectronic sensors, lasers, and more…<br />the Zang Research Group, Dept of MSE, University of Utah <br />
  9. 9. Integrated for multi-target detection<br />
  10. 10. Linearly polarized emission : single-nanobelt study by NSOM<br />J. Phys. Chem. B, 110 (2006), 12327-12332 <br />
  11. 11. Waveguide:just another 1D confinement<br />Chem. Mater. 21(2009) 2930-34. <br />
  12. 12. Waveguide:just another 1D confinement<br />Chem. Mater. 21(2009) 2930-34. <br />
  13. 13. Self-waveguide emission: dominated by exciton migration at elevated temperature<br />300 K<br />4 K<br />Lupton, Zang, et al. Nano. Lett. 11 (2011) 488-492. <br />
  14. 14. Thermo-enhanced exciton diffusion<br />Waveguiding<br />dominated<br />Lupton, Zang, et al. Nano. Lett. 11 (2011) 488-492. <br />
  15. 15. Fluorescence<br />emission<br />illumination<br />X<br />Fluorescence<br />emission<br />Fluorescence<br />emission<br />illumination<br />illumination<br />TNT<br />*<br />*<br />*<br />*<br />*<br />Charge transfer occurs between<br />the Excited state (exciton) and TNT<br />Nanofiber: enhanced fluorescence sensing<br />Long-range exciton migration enables amplification of fluorescence quenching: locally formed excited state can be quenched by an explosive molecule randomly adsorbed on surface.<br />
  16. 16. piling<br />Enhanced sensitivity<br />Nanofibril film: for improved sensitivity<br /><ul><li>Amplified emission quenching;
  17. 17. Continuous porosity  expedient diffusion of gaseous molecules;
  18. 18. Large surface area  increased adsorption.</li></ul>Zang et al. Accounts of Chemical Research,  2008, <br />Special Issue on Nanoscience, invited.<br />
  19. 19. Efficient fluorescence quenching upon exposure to TNT vapor<br />5 ppb<br />detection limit,<br />< 10 ppt<br />J. Am. Chem. Soc.129 (2007) 6978-6979 <br />
  20. 20. Quenching efficiency independent on film thickness--- easy for manufacturing<br />Long-range <br />exciton migration<br />+<br />Cross-film diffusion <br />of explosives<br />Thickness independence<br />J. Am. Chem. Soc.129 (2007) 6978-6979 <br />
  21. 21. Efficient fluorescence sensing of amines vapor<br />amine<br />Nano Lett.,8 (2008) 2219-2223<br />
  22. 22. Maximal adsorption produces maximal sensing sensitivity<br />
  23. 23. expedient diffusion of guest molecules<br />fast sensing response: milliseconds<br />continuous porosity<br />Nano Lett.,8 (2008) 2219-2223<br />
  24. 24. Tubular fibrils for enhanced vapor sampling and trapping<br />
  25. 25. Emission intensity of tubular fibrils in response to TNT <br />Emission quenching data from NRL vapor generator<br />
  26. 26. Emission intensity of tubular fibrils in response to RDX <br />Emission quenching data from NRL vapor generator<br />
  27. 27. 1D enhancement of electrical conductivity via cofacial p-electronic delocalization of doped charges <br /> Leading to a sensor for reducing reagents.<br />J. Am. Chem. Soc.129 (2007) 6354-6355 and 129 (2007) 7234-7235. <br />
  28. 28. Bare nanowire<br />The conductivity estimated: 1.310-3 S m-1,<br />about 1 order of magnitude higher than that measured from polymer nanowires, e.g., polythiophene, F8T2.<br />The conductivity estimated: <br />ca. 1.0 S m-1, about 3 order of<br />magnitude higher than that of<br />undoped silicon, 1.610-3 S m-1. <br />Current enhancement upon exposure to hydrazine vapor<br />e-<br />amine<br />J. Am. Chem. Soc.129 (2007) 6354-6355 <br />
  29. 29. Low conductivity for pristine organic semiconductor: <br />neutral molecules, zero doping<br />Long axis of nanowire<br />zero charge carriers<br />Photo-doping via D-A charge separation to enhance the conductivity<br />J. Am. Chem. Soc. 132 (2010) 5743-5750. <br />
  30. 30. Photo-doping of n-type nanowires via D-A charge separation<br />Photoinduced<br />ET<br />Photoinduced<br />ET<br />electrons<br />No ET<br />Too fast<br />Just right<br />High conductivity: balance between intra- and inter-molecular ET.<br />J. Am. Chem. Soc. 132 (2010) 5743-5750. <br />
  31. 31. High 1D photo-conductivity<br />0.3 mW/mm2<br />0.03<br />On/off ratio > 1,000<br />@<br />low irradiation<br />0.4 mW/mm2<br />J. Am. Chem. Soc. 132 (2010) 5743-5750. <br />
  32. 32. Vapor sensing through charge-carrier depletion<br />Photoinduced<br />ET<br />electrons<br />explosives<br />Suited for sensing weak-oxidizing reagents that are difficult to detect by fluorescent sensors.<br />J. Am. Chem. Soc. 132 (2010) 5743-5750. <br />
  33. 33. Enhanced electrical vapor sensing via photo-doping<br />Fast blowing of nitro-methane vapor<br />volatile, weak-oxidizing, difficult to detect …<br />
  34. 34. Ideal sensor for vapor detection <br />High sensitivity or low detection limit: stand-off detection (> 50 m, ideally 100 m), trace TNT (40 ppt) over buried landmines. <br />Fast response:seconds, porous structure and continuous channel both enhancing the penetration of gaseous molecules into the film, strong chemical interaction (sticking) at interface improving the accumulation of target molecules within the film. <br />Stability: thermal damage, photobleaching, thick film desired for improved stability, sustainability, reliability and reproducibility. <br />Selectivity: against environment interferences.<br />Cost effective: cheap for materials and processing, flexible for materials modification and improvement, adaptable to various substrates for device fabrication --- all can be satisfied with organic materials. <br />Easy to use, minimal maintenance, …<br />
  35. 35. Thinner Fibers for Enhanced Vapor Sensing<br />amine<br />diameter<br />350 nm<br />40 nm<br />ChemComm. 2009, p5106.<br />
  36. 36. Enhanced Vapor Sensing of Aniline by shrinking down the size of fibers<br />40 nm <br />nanofiber<br />350 nm <br />nanofiber<br />Detection limit down to a few ppt<br />
  37. 37.
  38. 38. TNT<br />
  39. 39. TNT<br />