• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Zang Trace Explosives Detection Presentation
 

Zang Trace Explosives Detection Presentation

on

  • 2,439 views

 

Statistics

Views

Total Views
2,439
Views on SlideShare
1,482
Embed Views
957

Actions

Likes
0
Downloads
21
Comments
0

2 Embeds 957

http://www.vaporsens.com 927
http://www.weebly.com 30

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Zang Trace Explosives Detection Presentation Zang Trace Explosives Detection Presentation Presentation Transcript

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