Selective Functionalization of OWL Nanostrutures Using Simple Wet-Etchant

Techniques

William A. Gallopp, Skidmore CollegeMatthew J. Rycenga, Chemisty

Chad A. Mirkin, ChemistryNorthwestern University

Outline

• Motivation and strategy of selective functionalization

• Fabrication of nanorods (On Wire Lithography)

• Optimized etchant parameters

• Energy Dispersive Spectroscopy analysis of

selectively functionalized rods

What is Selective Functionalization?

The ability to control the molecular coverage of a nanoparticle surface.

Selective Functionalization is Critical to Nanotechnology

P. Muhlschlegel, et al. Science, 2005, 308, 1607Y. Xia, et al. Adv. Mater., 2008, 308, 1607

Etching Sonication

1. Dissolve Template (NaOH )

Electrochemical Synthesis

Au or Ag

Ni

Au/Ti or SiO2

2. Disperse rods on Glass Slides

Deposit Backing(SiO2, metals)

Mirkin and coworkers, Science

On-Wire Lithography (OWL)

(Alumina Membrane)

HNO3

NaOH

Ag Evaporation

Ag Electrodeposition

Rinse

New Plating Sol’n

Reference electrodeCounter electrode

Working electrode

Rinse

New Plating Sol’n

Nanorod Fabrication

Length: 380 nm Au segment: 100 nm and 200 nm Diameter: 55 nm Ni segment : 80 nm

Scale bars = 300 nm (top) 100 nm (bottom)

Nano Lett. 2007, 7, 3849

Currently No Control Over Functionalization

Proposed Strategy for Selective Functionalization

= Streptavidin-FeO3NPs (d = 10 nm)

HS OO

OO

OO

NH

O

S

NH

HNO

Biotin thiol

MHA (Hydroxy thiol)

Monitoring Etching process by UV-Vis: Unprotected Rods

Unetched Rods

Etched Rods

200 nm

500 nm

Monitoring Etching process by UV-Vis: Unprotected Rods vs. Coated Rods

2.76mM HCl solution

MHA Coated Rods

Unprotected Rods

200 nm

200 nm

MHA Coated Rods require longer etch times and higher HCl concentration

27.7 mM HCl solution1.0 -1.5 hrs

500 nm 2.00 um200 nm

Energy-Dispersive X-Ray Spectroscopy (EDS)

EDS for Identification of FeO

Au Ni FeImage

Summary

• Importance of selective functionalize

• OWL and selective functionalization processes

• Optimized etchant parameters

• EDS Analysis of functionalized rods

Future work

• Optimize biotin/streptadvin coupling

• EDS confirmation of selective functionalization

• Deposit silica backing to nanorods (OWL)

• Selectively functionalize rods with DNA

Acknowledgements

• Prof. Chad Mirkin

• Dr. Matthew Rycenga

• Dr. Chad Shade

• Dr. Gilles Bourret

• NSF

EDS: Fe Particles