structure formation, melting and the optical properties of gold/dna nanocomposites sung yong park...
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Structure Formation, Melting and the Optical Properties of Gold/DNA Nanocomposites
Sung Yong Park and David Stroud
Department of Physics, Ohio State University, Columbus, OH 43210.
Work Supported by NSF DMR04-13395 and DMR01-04987. Calculations carried out using facilities of the Ohio Supercomputer Center
1. Introduction
DNA/Au nanoparticle colloids and linking strands
Linker DNA
R. Jin, et. al, J. Am. Chem. Soc. 125, 1643 (2003).
R. Elghanian, et. al., Science 277, 1078 (1997).
Linker DNA
Recent Experiments
Particle-size dependence of Melting
Measured Melting Curves
R.Elghanian, et. al., Science 277, 1078 (1997). C.-H. Kiang, Physica A 321, 164 (2003).
Particlediameter
DNA only
DNA/Au
DNA/Au DNA only
R. Jin, et. al, J. Am. Chem. Soc. 125, 1643 (2003).
Recent Experiments: Rebound Effect
2. Calculation of Optical Properties
Maxwell’s Equations Strategy: Consider each particle as a single dipole
Comparison DDA with more accurate method (89 13nm Au particle)
K.L. Kelly, et. al, CSE, (2001).
3. Structure at low temperature
Recipe for Reaction Limited Aggregations
1. Irrevesible process of bonding
2. Slow reaction (fractal dimension 2.1)
Cf. DLCA (lower fractal dimension)
At low T, this system satisfies these conditions.
TEM Images of Linked DNA Gold Nanoparticles
http://www.chem.nwu.edu/~mkngrp/view1.html
Aggregate of 13 nm diameter DNA/gold nanocomposites Increased magnification image
Comparison with fast processGold-MUA nanoparticles(mercaptoundecanoic acid)
Y. Kim, et. al, Nano Lett. 1, 165 (2001).
?
Morphology dependence of extinction cross section
Theory Experiment
Comparison of size dependence of the extinction cross section
RLCA cluster Simple Cubic Cluster
4. Melting Transition
My strategy for explaining the results in experiments
1. DNA hybridizationo Two-state model
o “Multiple link per bond” effect
2. Cluster configuration at given temperature T
o Bond percolation model
o Model the system as simply as possible
3. Calculation of Extinction Cross Sectiono Discrete Dipole Approximation (Draine & Flatau, 1994)
o Dilute cluster limit
o Reaction limited cluster aggregation model
DSS
KD
SS
][
]][[
Two State Model
)exp( TG
3)()( MM TTbTTaG
We treat p as static probability.
][D : Concentration of duplex
: Total concentration of DNA
probability that DNA pair remains hybidized is
1. DNA hybridization
“multiple DNA per bond” effect
p p =1-(1-p)
n
eff
n
Particle-size dependence of avg. no of DNA per bond <n>
Temperature dependence of Peff
= Prob. that pair of Au particles have > 1 DNA links
Particle diameter
1. DNA hybridization
My strategy for explaining the results in experiments
1. DNA hybridizationo Two-state model
o “Multiple link per bond” effect
2. Cluster configuration at given temperature T
o Bond percolation model
o Model the system as simply as possible
3. Calculation of Extinction Cross Sectiono Discrete Dipole Approximation (Draine & Flatau, 1994)
o Dilute cluster limit
o Reaction limited cluster aggregation model
1. Prepare the low-T config.
Schematics of melting for a regular square lattice
2. Cut bonds with prob. 1-p
3. Place the connected clusters into
larger box with random position and random orientation.
p=0.95 p=0.50
p=0.0
p=0.25>pc
Our model: melting of a regular simple cubic cluster
Bond percolationthreshold
p=0.15<pc
My strategy for explaining the results in experiments
1. DNA hybridizationo Two-state model
o “Multiple link per bond” effect
2. Cluster configuration at given temperature T
o Bond percolation model
o Model the system as simply as possible
3. Calculation of Extinction Cross Sectiono Discrete Dipole Approximation (Draine & Flatau, 1994)
o Dilute cluster limit
o Reaction limited cluster aggregation model
Calculation of extinction cross section
Using Discrete Dipole Approximation (DDA)
Dilute Cluster LimitTemperature dependence of extinction cross section at 520nm
DNA only
DNA only (higher concentration)
DNA only
DNA/Au
DNA/Au
DNA only
Theory vs. Experiment
D
Temperature dependence of extinction cross section at 520nm
Theory Experiment
DNA only
DNA only (higher concentration)
5. Effects of Restructuring
If T increases, bonding becomes reversible.Thus it becomes compact cluster.
Thus, the model to mimic this feature is needed.
o Bond percolation model
+ Reaction limited cluster aggregation model
Radius of gyration
RLCA case
Slope=fractal dimension =2.1
With RLCA + BP
Long time: 3.0
Short time=2.1
P=0.9
N MC=0 N MC=7000
N MC=70000 MC=70000
N MC=7000
RLCA
6. Summary
DNA/Au nanocomposite system
R. Jin, et. al, J. Am. Chem. Soc. 125, 1643 (2003).
R. Elghanian, et. al., Science 277, 1078 (1997).
Linker DNA
1. Expected phase diagram
2. Morphologies from a structural model
3. DDA calculation of extinction cross section
gel sol Ind. particles
Gel-sol transition
meltingtransition T0
gel sol
near melting transition
Gel-soltransition
meltingtransition
Experiment