Fluorescent nanohybrids based on asymmetrical cyanine dyes decorated carbon nanotubes

Official URL: http://risc01.sabanciuniv.edu/record=b1615024 (Table of Contents)

In this thesis, we focused on imparting new optical properties to carbon nanotubes (CNTs) to allow their optical detection and visualization in biomedical applications. We investigated the interactions of CNTs and DNA wrapped CNTs with asymmetrical cyanine dye molecules to study the applicability of resulting hybrid materials to fluorescent based systems. When CNTs interacted with asymmetrical cyanine dyes, they constructed a light absorbing nanoarray. However, the fluorescence emission of the two component structure was quenched. Alternatively, when single stranded DNA (ssDNA) wrapped CNTs interacted with asymmetrical cyanine dye molecules not only the absorbance intensity was altered but also the fluorescence intensity increased several fold. The assembly of CNT/dye nanohybrids and ssDNA/CNT/dye nanohybrid was also demonstrated by a shift in Raman spectrum indicating noncovalent binding. The thermal stability of ssDNA/CNT/dye nanostructures was investigated by fluorescence-based thermal analysis. Additionally, individually dispersed ssDNA/CNT nanohybrids and ssDNA/CNT/dye nanohybrids were visualized by transmitted electron microscopy (TEM) and scanning electron microscopy (SEM). Moreover the fluorescence of three component nanohybrids was visualized with confocal microscopy. When CNTs were excited with UV light, they became fluorescent. We have demonstrated that ssDNA wrapped CNTs can act as a scaffold on which asymmetrical cyanine dyes can self-assemble with increased quantum yields. Our work demonstrates the first example that a fluorophore lights up when it binds CNTs, thus provides a novel approach for the fluorescent labeling of CNTs.