DOEBES Workshop Basic Research Needs to Counter Terrorism Chemical Threats

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DOE/BES Workshop Basic Research Needs to Counter
TerrorismChemical Threats

• 2/28/02
• Michael J. Sailor
• Department of Chemistry and Biochemistry
• University of California, San Diego
• La Jolla, CA 92093-0358
• msailor_at_ucsd.edu

Devices
Systems
Materials
80 mm
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Death on the Danube
The Economist, 2/15/00
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Basic Science Needs

• Prevention
• Detection
• Individual and Collective Protection
• Remediation
• Medical Countermeasures

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Water and Air Quality Monitors

• TICs, TIMsMetal ionsHydrocarbonsHalocarbonsBlo
  od, Blister agentsPesticidesHerbicides

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Molecules vs Particles
Sarin 1nm
Anthrax spores 1000 nm
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Molecules vs Particles
Sarin 1nm
Anthrax spores 1000 nm
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Molecules vs Particles
Sarin 1nm
Anthrax spores 1000 nm
TOOLS Antibody/Antigen interactions, PCR slow
TOOLS Spectroscopy (IR, Mass, UV/Vis,
SAW,) fast
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Issues

• Science Transducer, Sample collection, Sample
  Prep
• Engineering Systems Integration,
  Miniaturization, Microfluidics
• Financial Medical vs Environmental Markets
• Transition to the forcesNIH, Power,
  refrigeration, disposables (logistics tail)

BAWS III
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Semiconductor Technology

• Drivers
• Smaller
• Faster
• Cheaper

Pentium III Xeon 24 million transistors
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Chip Technologies used in BioTech

• Fluorescent DNA probes on Silicon Chips

Michael Heller, Sadik Esener
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Synthesis of Nanocrystalline Porous Si Films

• High surface area (200 m2/g)
• Tunable Pore Dimensions
• Chemically Modifiable

20 mm
Background Properties of Porous Silicon
Canham, L., Ed. EMIS Datareviews, INSPEC
London, 1997 Vol. 18.
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Recombination Pathways Available to Si
Nanocrystallites
Funding DOE, NSF
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Structures of Common High Explosives
2,4-DNT
TNT
1,3-DNB
1,3,5-TNB
N
N
N
N
N
N
N
N
RDX
Tetryl or nitramine
HMx
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Catalysis to Provide Specificity TNT Detector
Channel 1
Channel 1 Channel 2
SIGNAL
CCD
Channel 2 (with catalyst)
Lens filter
Porous silicon chip
TNT Detection Limit 4 ppb Using Pt catalyst to
obtain specificity2Content, S. Trogler, W. C.
Sailor, M. J., Chem. Europ. J., 2000, 6,
2205-2213.
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Detection of TNT (4 ppb in air)
Channel 1
Channel 2
TNT/no catalyst
TNT/with catalyst
t 0/5/10/ 15/20/25/ 30/35...min
t 0/5/10/ 15/20/25/ 30/35...min
Quenching 55
Quenching lt 1
Catalyst PdO
Signal Ch1/Ch2 gt 1
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Luminescent Silicon Nanowire TNT Sensors
Luminescence Quenching for sensing of Explosives
and Nerve AgentsThe materials operate by
electron transfer quenching. Quenching is
induced by an IR-emitting chromophore (for
fluorophosphate nerve agent detection) or by the
strongly electron-accepting class of
nitroaromatic explosives (demonstrated with TNT
and Picric acid).
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Silicon Nanowire (Polysilole) TNT Sensors
Detection of ExplosivesTNT-contaminated
thumbprint on a transit ticket from the San
Francisco BART line. The ticket on the left was
not exposed to TNT and serves as a control. After
exposure, the paper was coated with a fine mist
of polysilole. The image was taken under a black
light.
Detection of Explosives in SeawaterTwo paper
tickets coated with polysilole, then soaked for
30 sec in seawater (collected off Scripps Pier,
La Jolla, CA). The seawater used in the bottom
ticket was spiked with 50 ppb of purified TNT.
The top ticket is the control. The image was
taken under a black light.
control
TNT
Dip line
Funding DARPA
Sohn, H. Calhoun, R. M. Sailor, M. J. Trogler,
W. C., Angew. Chem. Int. Ed., 40, 2104-5 (2001).
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Amplification by Molecular Wires-T. Swager, MIT
Swager, T. M. Accts. Chem. Res. 1998, 31, 201-7
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Analyte detection (acetone) in a nanostructured
film
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Photonic Bandgap Nanostructures
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Amplified Gas Sensing in Nanoporous Media
Capillary condensation Liquids spontaneously
condense from vapor into cracks and pores as bulk
liquid.
Schematic of a PS sample
Kelvin Equation
Surface energy
P
1
kBTln( ) ?Vm( )
Ps
RK
Effective pore radius
Molar volume of the liquid
Gao, J. Gao, T. Sailor, M. J., Appl. Phys.
Lett., 77, 901-3 (2000).
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Specificity Catalytic Hydrolysis of CW Agents
HF
H2O
SiO2(s) HF(g) SiF4(g) H2O(g)
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1
5
10
20
Right half exposed to vapor over aqueous HF at
the indicated concentrations
Létant, S. Sailor, M. J., Adv. Mater., 12,
355-359 (2000).
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Laser Interferometer using Nanocrystalline Porous
Si Transducers

• Detection Limit (ethanol) 500 ppb
• Dynamic range 5 decades
• A Porous Silicon Vapor Sensor Based on Laser
  Interferometry, Gao, J. Gao, T. Sailor, M. J.,
  Appl. Phys. Lett., 77, 901-3 (2000).

Handheld nanosensor device for nerve agent
developed for DARPA Micro Unattended Ground
Sensors program (P.M. Dr. Ed Carapezza)
Sarin run showing response to Sarin at 10 ppm
within 7 min of introduction. The sampling
chamber depleted of agent ca. 10 min into the
run. (Dr. Kwok Ong, APGEA)
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Pore Dimensions can be Varied in Porous Si
Vicki Chin
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Sizing Proteins in a Nanostructured Film
Fringe Response Observed
Protein (BSA) Response
200
150
100
Change in OT, nm
50
0
1
2
3
4
5
6
7
8
9
10
11
-50
Distance from electrode (mm)
Collins, Adv. Func. Mat., in press
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Detection and SamplingStandoff Detection
YOUR TECHNOLOGY HERE
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Nanostructured Smart Dust Sensors Si photonic
bandgap particles
80 micron PBG squares on Si substrate
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Standoff Detection of VOCs With nanostructured
Si photonic bandgap particles
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Bioassay with Encoded Particles
Fluorescence and optical reflectivity spectra
(background correction applied) for the two sets
of rugate-encoded particles. A) Particles
functionalized with rat albumin, then assayed
with the FITC-conjugated secondary antibody. B)
Control particles treated with bovine albumin and
assayed with the FITC-conjugated anti-rat
secondary antibody. Approximate rugate unit cell
dimension is 180 nm and 250 nm, respectively.
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Outlook

• There is no Grand Unified Sensor
• Integration of multisensor elements will be key
• Triggers will be more important than specificity,
  especially for emerging threats