Aptamers are nucleic acid sequences with strong, selective affinities for binding target molecules. They have become popular tools in nanotechnology as they offer better selectivity than anti-bodies while maintaining high levels of target-bound stability. More importantly, nucleic acid aptamer strands are easily modifiable, making them applicable to a variety of chemical instrumentations and techniques. Here in the Strouse lab, we are interested in employing these aptamers in designing optical sensors for target detection. We construct molecular beacon-style optical probes for small-molecule detection using the aptamers appended to gold nanoaprticles. These concentration-based optical assays combine the distance-based theory for energy transfer, NSET, with conformationally-active aptamers. In our work with the ATP DNA aptamer, we show that this molecular-beacon based approach is useful for spanning several magnitudes of target concentration detection (pM-mM) by relocating the specific aptamer sequence in the stem-loop configuration. In addition, by studying these systems optically, site-specific binding information is available that is inaccessible by NMR, EPR, electrochemical detection, etc. The future of this work entails multiple flourescent-dye labels on the aptamers to triangulate distal changes in the nucleic acid's conformation.