1. Group Members: William Ballik Robbie Edwards Alex Klotz Gio Mitchell
DNA Nanowires
Phys Group 3
Group Members: William Ballik Robbie Edwards
Alex Klotz Gio Mitchell

2. Introduction
Carbon nanotubes: interesting properties, difficult to manufacture
Biological template-DNA
DNA can be plated with cobalt to create magnetic cobalt nanowires.
Manufacturing is electroless

3. Preparation DNA from virus treated in buffer
Palladium clusters are adsorbed onto DNA surface
Molecules placed on MICA substrate or silanized glass
Conditions: 50ºC, pH 6.

4. Fabrication Three chemical reactions: Pd (II) + DNA bases  Pd(II):DNA
Pd (II):DNA + DMAB  Pd(0):DNA
Pd(0):DNA + DMAB + Co (II)  Pd(0)Co(0):DNA + DMAB+

5. Fabrication
The palladium activation expected to produce more uniform deposition of cobalt; cobalt only bonds to the palladium-coated DNA surface
Palladium acts as catalyzing agent in electroless plating, with DMAB chemical acting as reducing agent
If Pd activation is not done, but Pd and Co added in solution, expect aggregates to form non-uniformly

6. Fabrication Metalization bath of cobalt mixed with prepared DNA
Treated for minutes or more.
DNA molecules could be oriented with molecular comb: bound to silanized glass and stretched through evaporation.
Final products examined with AFM and UV/X-ray spectroscopy

7. Results: UVS
UVS (ultra-violet spectroscopy) used to verify Pd bonded to DNA
Note that in activated case (left) the “shoulder” at 260 nm—absorbed by DNA—disappears after time. Otherwise doesn’t.

8. Results: EDX
EDX (Energy Dissipative X-Ray) used to find spectrum of nanowire, shows presence of Co.

9. Results: AFM Used tapping mode.
Produced cobalt plated DNA nanotubes ~10x35 nm in cross section
Plating was 70-80% continuous in non-activated case; near 100% in activated case
Random clumping of Co and Pd form nanoparticles.

10. Results: AFM
Images compare non-activated (A) and activated (B) samples after cobalt plating.

11. Results: AFM Nanowires could be oriented by molecular combing.
Free Pd causes faster growth, but harder to control than bound Pd.
Non metallized DNA proved unsuitable for Co deposition

12. Comparision with carbon nanotubes
Much faster fabrication, no electric potential required
Ferromagnetic
Inhomogeneous surface compared to CNT
Most likely lacks unique material properties.
Original DNA strand acts as template for standardized and simple fabrication.

13. Applications Wires can be used for nanoelectronics
Preparation process can also be used to create nanoparticles.
Magnetic nanowires can be used for high-density storage.

14. Is this nano? Self-assembly of particles onto surfaces
The creation of extremely small-scale memory devices: islands or clumps only a few atoms wide
This is mostly chemistry, and not so much quantum effects
Useful for nano properties, but formation is not primarily quantum/nano behaviour

15. Questions?