Optically Anisotropic Films of Colloidal Nanocrystals/Photoluminescent Dye Doped Polymers

Abstract

Semiconductor colloidal nanocrystals are attractive materials since they can be adapted to polymers to form hybrid materials and are compatible with many optical applications. Here, synthesis of CdSe/CdS nanorods (NRs) via hot injection method is carried out, followed by preparation of hybrid polymer films from polyethylene glycol monomethyl ether-block-poly(glycidyl methacrylate)-block-poly[2-(diethylamino)ethyl methacrylate] triblock copolymer (MPEG-b-PGMA-b-DEAEMA) at a liquid-air interface. The optical properties of the films are finely adjusted to form optically anisotropic (i.e. dual-color emissive) films by using dyes for the other emitter as desired. Thiazolo[5,4-d] thiazole (TTz)-based dye and 6-carboxy fluorescein were used for this purpose. Tunable emission of TTz dye from blue to green dependent on changing pH value resulted in blue-green emissive polymer films, while red emission of CdSe/CdS NRs caused red emissive films. Phase separation of these materials is achieved by the hexane-insoluble nature of MPEG-b-PGMA-b-DEAEMA and the high solubility of NRs in it. These dual emissive films are promising candidates for waveguides and optical sensors.