Optical waveguiding and temperature dependent photoluminescence of nanotubulars grown from molecular building blocks

Optical waveguiding of blue light after UV-excitation is demonstrated in bundles of organic nanotubulars obtained via template assisted aggregation of the small π-conjugated non planar molecules 17H-Tetrabenzo[a,c,g,i]fluorene (17H-Tbf) and 17-Trimethylsilyltetrabenzo[a,c,g,i]fluorene (TMS-Tbf). The propagating blue light is strongly attenuated due to self-absorption. Vibronic spectra for both nanotubulars and macroscopic crystallites for temperatures between 5 and 300 K show a behavior of TMS-Tbf that resembles that of long chained molecules while 17H-TbF resembles that of small organic molecules. For both molecular species crystallites and nanostructures have large average Huang–Rhys factors indicating strong phononic coupling promoted by the polycrystallinity of the samples.