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Detecting Danger at NanoscaleOrganic Nanowires for Trace Vapor Sensing of Explosives and Other Threatening Chemicals
The Zang Research Group, Department of Materials Science and EngineeringTel. 801-587-1551, Email: [email protected], Web: www.eng.utah.edu/~lzang
Long-range exciton migration enables amplification of fluorescence quenching
Electron delocalization leads to a sensor for reducing reagents
Optical and Electrical Sensing
Enhanced sensitivity
• Amplified emission quenching;
• Continuous porosity expedient diffusion of gaseous molecules;
• Large surface area increased adsorption
Materials covering both n-type and p-type:• n-type: electron accepting sensing for
reductive (e-donating) molecules, e.g., amines.• p-type: electron donating sensing for
oxidative (e-accepting) molecules, e.g., nitro-aromatics. 1 2 3 4 5 6 7 8 9 10
0
20
40
60
80
100
1. TNT (5 ppb); 2. Pantene Pro-V Mousse; 3. Loreal Studioline Hair Spray; 4. Head&Shoulders 2 in1 shampoo; 5. Pond's dry skin cream; 6. Olay UV moisturizing lotion; 7. Neutrogena men face lotion SPF 20; 8. Colgate Total toothpaste; 9. Chanel Allure perfume; 10. Fendi Theorema perfume.
I / I 0
% (c
orr.
for 2
% p
hoto
blea
chin
g)
Before exposure After exposure
Potential Interference from Cosmetics (10 s exposed to sat. vapor)
CH3
NO2
NO2
O2N
TNT
Selectivity against ambient interferenceEfficient fluorescence sensing of explosives vapor
TNT (5 ppb)
J. Am. Chem. Soc. 2007, 129, 6978-6979
Electrical sensing of hydrazine vapor
J. Am. Chem. Soc. 2007, 129, 6354-6355.
+ -PTCDI nanowireglass
Bare nanowire
aminee-
1E-3 0.01 0.1 1 10 100 10001E-4
1E-3
0.01
0.1
1
Vapor concentration (ppb)
5 ppt
0.1 ppb 1 ppb5 ppb
Que
nchi
ng e
ffici
ency
(1-I/
Io)
Vapor Sensing of Aniline
350 nm nanofiber
Detection limit down to a few ppt
40 nm nanofiber
Ultimate fine nanowires: cross-section of just one molecule!
AcknowledgmentsZang Group:Kaushik Balakrishnan
Aniket Datar
Tammene Naddo
Jialing Huang
Steve Loser
Meagan Hatfield
Randy Oitker
Ryan Rakher
Jay Moon
Ryan Martin
Dr. Xiaomei Yang
Dr. Yanke Che
Dr. Jianhua Gao
Dr. Chengyi Zhang
$$Support $$ :• MTC Grant, 2004, 2005;• CARS program;• K.C. Wong Foundation (Hong Kong);• Argonne National Lab;• NSF: CMMI, CAREER, CBET, MRI;• ACS-PRF;• FHWA-State DOT Partnership (07-10);• NSFC;• Department of Homeland Security;• USTAR, UU-MSE.
Instrumentation Support:UU Nanofab, Microfab, NMR of Chemistry, Argonne, APS; UIUC, DOE-CMM.
Collaborators:Group of Jeff Moore, UIUCGroup of NJ Tao, ASUGroup of Jim Zuo, UIUCDr. David Tiede at Argonne National labMater. Tech Center of SIU
Organic Semiconductor: competitive for silicon
nanodevices, optoelectronic sensors, lasers, etc.
1D self-assembly through molecular π−π stacking
Accounts of Chemical Research, 41 (2008) 1596-1608. J. Am. Chem. Soc. 2005, 10496-10497, 2006, 6576-6577, 7390-7398, 2007, 6354-6355, 6978-6979, 7234-7235.
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.
Nano Lett. 2008; 8, 2219-2223.
Efficient fluorescence sensing of amines vapor Quenching efficiency independent on film thickness--- easy for manufacturing
Long-range exciton migration
+Cross-film diffusion
of explosives
Thickness independence
15 30 45 60 75 900
20
40
60
80
100
Que
nchi
ng (%
)
Film Thickness / nm
CH3
NO2
NO2
O2N
TNT
CH3
NO2
NO2
DNT
High stability for repeated use
Ultrathin nanowires for increased surface area and more confined exciton diffusion and charge transport
Freshly deposited nanobelt
Broken after high current
