Transcript Electrical Measurement of Single Molecule Catalysis using

Electrical Measurement of Single
Molecule Catalysis using Carbon
Nanotubes
Brett Goldsmith, Alexander Kane, Vaikunth Khalap,
John Coroneus, Gregory Weiss, Phil Collins
Department of Physics and Astronomy
University of California Irvine
Outline
 Single Molecule Sensor Construction
 Measurement of Catalysis Reaction Rate
 Dynamics of the Bound State
Single Molecule Sensors
Ensemble
binding
analyte
absent
present
Stochastic
absent
binding
analyte
absent
present
absent
Device Construction
Elec trolyte
drop
Counter
Reference
Source
Drain
Source
PMMA
coating
PMMA
PMMA
Drain
Coroneus, et al. Chem. Phys. Chem. accepted
Goldsmith, et al. Science 2007, 315, 77.
Device Characterization
The Catalysis Reaction
EDC
attached EDC
+
EDC binds to the carboxyl
group on the nanotube.
urea
+
The bound EDC perturbs the
current in the nanotube.
A reaction with water releases the
bound EDC as a mixed urea.
Functionalized CNTs in Buffer
Interaction With EDC
Goldsmith et al. Nano Lett., 8 (1), 189 -194, 2008
Interaction With EDC
Turnover Time
Time Bonded
Waiting Time
Single Molecule Rate Constant
Turnover Time
Time Bonded
Waiting Time
k-1= 58.9 ± 18.3 s
Bound State Lifetime
Bound State Lifetime:
<tbound> = 12.4 ± 2.1 s
k-1= 58.9 ± 18.3 s
Bound vs. Unbound
Dynamics of the Bound State
Energy of a Two Level System
DE = kBT ln(<tlo>/<thi>)
~11% of these states are
very different
Energy of a Two Level System
90%
10%
at experimental pH = 4.5
Reaction Intermediate States
Summary
Goldsmith, et al. Science 2007, 315, 77.
Goldsmith et al. Nano Lett., 8 (1), 189 -194, 2008
Goldsmith et al. JMR, accepted
Coroneus, et al. Chem. Phys. Lett., accepted
Dr. Phil Collins
Brett Goldsmith
Alex Kane
Bucky Khalap
Steve Hunt
Danny Wan
Tatyana Sheps
ACS-PRF
Dr. Gregory Weiss
John Coroneus
Other Samples…
EDC
JMR…
Pthalic Anhydride
Timescale of the Two Level System
Amplitude of the Two Level System
The amplitude of the two groups of bound states also differs.
These different bound state properties could be due to the
~10% protonated EDC in solution at our conditions.