DNA-Directed Assembly of Anisotropic Nanoparticles on Lithographically Defined Surfaces and in Solution
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DNA-Directed Assembly of Anisotropic Nanoparticles on Lithographically Defined Surfaces and in Solution Brian D. Reiss, Jeremiah N. K. Mbindyo, Benjamin R. Martin, Sheila R. Nicewarner, Thomas E. Mallouk, Michael J. Natan, and Christine D. Keating* Department of Chemistry, The Pennsylvania State University University Park, PA 16802, USA *Author to whom correspondence should be addressed at [email protected] Abstract Anisotropic, noble metal nanoparticles have been synthesized using a template synthesis strategy. In short, metallic salts are reduced in the nanometer scale pores of either an alumina or polycarbonate membrane. The particles can then been released from the template to form suspensions of anisotropic nanoparticles. These nanoparticles have been modified with deoxyribonucleic acid (DNA) oligomers of varying length using several different attachment chemistries. The thermodynamics and kinetics of modifying these particles with DNA has been explored. DNA has also been used to assemble the particles on planar Au surfaces as well as lithographically defined Au pads on Si wafers. In addition to surface assembly, DNA has been used to assemble the nanowires into simple, yet deterministic structures in solution. Introduction Since the mid twentieth century there has been a great deal of interest in the miniaturization of electronic devices. Currently state of the art photoloithographic technology can fabricate devices in the 100 nm size range, but there is an economic motivation to reduce the dimensions of electronic circuitry even further. Due to scientific constraints, there are limitations in the extent to which devices can be fabricated using photolithography.[1] For this reason, there has been a great deal of interest in the development of novel technologies for fabricating smaller devices than can be prepared using photolithography. One such alternative is the “bottom up” approach where devices are self-assembled from very small building blocks as opposed to being etched out of larger pieces of material (a “top down” strategy).[2] Such an approach offers two key advantages. First of all, since devices can be fabricated from nanoparticles or even individual molecules, it is feasible to fabricate much smaller devices than can be prepared using photolithography. The second key advantage is cost. Modern fabrication facilities for photolithography cost over a billion dollars to build, but one can start self assembling devices for a fraction of that cost. The goal of this research is to assemble anisotropic nanoparticles into functional electronic devices, including memory devices, logic gates, etc. To accomplish this task, two things are necessary: the anisotropic nanoparticles and a “smart glue” to make the particles self assemble into desirable geometries. DNA was chosen as a glue because it offers several unique advantages. [3-5] The primary advantage is selectivity, which results from the specificity an oligonucleotide has for its complementary oligonucleotide. Oligonucleotides have been shown to bind sel
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