Optical pH response of DNA wrapped HiPco carbon nanotubes

Solubilization of single-walled carbon nanotubes in aqueous solution by surface functionalization is of great interest for biosensor applications and separation of individual nanotubes. Here we have observed that HiPco nanotubes can be stably dispersed into double-stranded DNA aqueous solutions. Interestingly, the first optical interband transitions of the DNA wrapped semiconducting HiPco nanotubes possess a unique pH dependence, a phenomenon observed in SDS-encased and carboxylic group functionalized single-walled carbon nanotubes. The unique optical pH dependence of surface modified semiconducting nanotubes may have promising applications in optical biosensors.