Tuning Optical Properties of Functionalized Gold Nanorods through Controlled Interactions with Organic Semiconductors

A novel nanohybrid assembly consisting of gold nanorods (AuNRs) and organic semiconductors (OSCs) to tune optical properties is presented. OSCs are bound to specific areas of the AuNRs (e.g., end or side) by controlling the surface chemistry of the AuNRs. AuNRs anisotropically functionalized with cetrimonium bromide (CTAB) cysteine, poly­(ethylene oxide) (PEO), and/or DNA. Rhodamine B (RhB) 5(6)-carboxyfluorescein (CF), or cyanine3 (Cy3) are incubated with the anisotropically functionalized AuNRs. The resulting optical properties of the dispersed AuNRs are characterized via steady-state UV–vis absorption and photoluminescence (PL) spectroscopies as a function of OSC concentration. We found that CF and RhB adsorb to the AuNR differently depending on the AuNR surface chemistry, which results in unique optical properties of the assembly. The distinctive spectra were used to determine the interaction between the OSC and the AuNR. Finally, we found that attaching Cy3 specifically to the ends of the AuNR via a DNA tether results in a larger emission quenching process than when Cy3 is not attached. This method of nanohybrid assembly can be extended to other metal nanostructures and OSCs. Its generic nature qualifies it as new methodology to precisely assemble nano- and molecular objects with controlled (opto)­electronic properties.