Wire-Like Tip-To-Tip Linked Assemblies of CdSe-CdS Quantum Rods Promoted on Supramolecular Nanofibers of Hybrid Organo- and Hydrogels

A variety of core-shell CdSe-CdS nanorods or quantum rods (QRs), both sphere (CdSe) in rod (CdS) and rod (CdSe) in rod (CdS) have been synthesized in a seeded-growth approach using a very efficient and highly thermally stable steroidal cadmium precursor replacing the more common CdO: cadmium deoxycholate. The core-shell QRs display high photoluminescence quantum yields (40-75%) and high molar absorption co-efficient (epsilon=10(6) M-1 cm(-1)). Sphere-in-rods QRs can be co-assembled with the organogelator diethylaminolithocholyl iodide in 1,2-dichlorobenzene and with the hydrogelator calcium cholate in water to form hybrid gels. These organic-inorganic hybrid soft materials are translucent and brightly red-luminescent. The nanofibers composing the gel network act as a scaffold to support the dispersed QRs and impede their self-aggregation. Furthermore, formation of original wire-like assemblies of the nanorods is promoted in these gels, in particular in the hydrogel. This orientation occurs by a QR tip-to-tip interaction and is proposed to be driven by the amphiphilic behaviour of the QRs: laterally capped by negatively charged TGA (thioglycolic acid) ligands and un-capped on the tips due to TGA unbinding. The combination of nanofiber-forming hydrogelators and elongated quantum rods is promising in the perspective to form hybrid nanostructures with anisotropic optic or electronic properties.