Biomod/2013/NCSU

UNDER CONSTRUCTION

Macroscale Ordering of Asymmetrical Heterodimers

Ordering particles is difficult on the nanoscale and unfortunately becomes harder on larger length scales. Assembling particles on greater length scales allow for the design of structures with finely tuned properties not to mention precise arrangements. To accomplish macroscale ordering of nanoscale particles, one can either construct an ordered array via controlled assembly and placement; requiring fine-tuned reactions and kinetics resulting in a difficult game of nanoscale tetris, or by arranging the particles after their creation into an ordered array. While the first method requires precise control over the reactions and kinetics of the particles the second method allows for a less sensitive procedure. Using heterodimers composed of gold nanorods and quantum dots linked together with an oligonucleotide we hope to create a macroscale ordered array to exploit the plasmonic properties of gold nanorods on a higher length-scale. A recent paper demonstrated the alignment of gold nanorods suspended within a polymer (PEO) parallel to the axis of the electrospun polymer fibers. By electrospinning our heterdimer’s in Su-8 we hope to align our particles within the fibers to create a macroscale array of nanoscale heterodimers. This alignment will allow us to exploit the plasmonic properties of the gold nanorods on a higher length-scale than previously possible.

Experiment

Asymmetrical Heterodimers

Our heterodimers are composed of a gold nanorod (20 nm in diameter by 80 nm long) and a spherical quantum dot with a radius of 7 nm. They are linked by complementary oligonucleotides bonded to he surface by thiol groups.

In order to select for an asymmetrical orientation we designed a DNA origami sheet that will wrap around the gold rod preventing the quantum dot from binding anywhere except at the poles of the gold nanorod.

Functionalizing the gold nanorods and quantum dots has been a challenge. Below are two gels run on promising test runs. If the QD and QRs were functionalized with DNA they would have been pulled through the gel at different rates due to their different sizes.

This gel looked promising but both wells moved the same distance. The wells glowed under UV light revealing that the bands in the gel were unattached DNA strands.

This gel reveals the same problem.

Electrospinning

Once created our heterodimers will be suspended in SU-8 2015 and electrospun. This will align the gold rods parrallel to the axis of the polymer fiber aligning the entire heterodimer.