| This dissertation explored ways of merging chemically and biologically guided assembly of nanoparticle building blocks with surface-templated nanofabrication using dip-pen nanolithography (DPN), a scanning-probe based lithography. The factors that affect the activity of DNA-modified gold nanoparticles, specifically, the surface coverage and hybridization of these hybrid materials were determined. In addition, the conditions for generating stable DNA-modified nanoparticles were examined, as well as the effects of DNA length and sequence on particle properties. Importantly, a protocol was developed for controlling the average number of active DNA strands per particle. The details of the interaction of DNA with gold surfaces was further elucidated by using reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) mass spectroscopy to directly measure the strengths of interaction of the DNA bases and corresponding nucleosides to gold thin films. Desorption of films of the adsorbates from gold revealed significant differences in base-gold binding affinities. Significantly, the results reflect the trends observed for nucleoside adsorption onto gold nanoparticles and point to ways of designing stable, tailorable nanoparticle building blocks.; DPN was used to generate chemical and biological nanoscale templates for particle assembly. First, charged dot arrays were formed on gold substrates. These combinatorial chemical templates were screened to determine optimum dot size for immobilization of single charged polystyrene spheres. Next, to increase the sophistication of the assembly approach, DPN was used to generate DNA nanostructures. Two-component nanoscale DNA patterns were generated by coupling amine-modified DNA to chemically patterned surfaces. Assembly of two different sizes of DNA modified gold nanoparticles onto the DNA patterns through specific orthogonal DNA hybridization interactions was demonstrated. Finally, the conditions for direct-write DPN of DNA and properties of the resulting DNA nanostructures on metal and insulating substrates were investigated. It was found that DNA pattern size varies predictably with tip-surface contact time, and the rate of patterning rate is dictated by relative humidity. Resulting DNA nanostructures exhibited high selectivity with respect to organization of DNA-modified gold nanoparticles. |
