brett goldsmith, alexander kane, vaikunth khalap, john coroneus, gregory weiss, phil collins...

Brett Go ldsmith , A l exander Kane , Va i kun th Kha lap , J ohn Coroneus , Gregory We i ss , Ph i l Co l l i n s

Depar tment o f Phys i cs and As t ronomyUn iver s i t y o f Ca l i f o rn i a I r v ine

Electrical Measurement of Single Molecule Catalysis using Carbon Nanotubes

Outline

Single Molecule Sensor Construction

Measurement of Catalysis Reaction Rate

Dynamics of the Bound State

Single Molecule Sensors Ensemble Stochastic

present absent

binding analyte absent present absent

binding analyte absent

Device Construction

ReferenceCounter

Source Drain

PMMAcoating

Electrolytedrop

PMMA

PMMA

Source

Drain

Coroneus, et al. Chem. Phys. Chem. accepted

Goldsmith, et al. Science 2007, 315, 77.

Device Characterization

The Catalysis Reaction

EDC binds to the carboxyl group on the nanotube.

EDC

+ +

attached EDC 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

Time Bonded Waiting Time

Turnover Time

Single Molecule Rate Constant

Time Bonded Waiting Time

Turnover Time

k-1= 58.9 ± 18.3 s

Bound State Lifetime

k-1= 58.9 ± 18.3 s

Bound State Lifetime:<tbound> = 12.4 ± 2.1 s

Bound vs. Unbound

Dynamics of the Bound State

Energy of a Two Level System

DE = kBT ln(<tlo>/<thi>)

~11% of these states arevery different

Energy of a Two Level System

90%

10%

at experimental pH = 4.5

Reaction Intermediate States

Summary

Dr. Phil CollinsBrett GoldsmithAlex KaneBucky KhalapSteve HuntDanny WanTatyana Sheps

Dr. Gregory WeissJohn Coroneus

ACS-PRF

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

Other Samples…

EDC Pthalic Anhydride

JMR…

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.