Fabrication of a quantum dot-polymer matrix by layer-by-layer conjugation

A polymer-quantum dot (QD) composite matrix was fabricated by a simple layer-by-layer (LBL) covalent conjugation of cadmium selenide (CdSe) QDs to poly(dimethylsiloxane) (PDMS) films. LBL covalent conjugation was preferred in the current work for avoiding possible phase separation of QDs into microdomains when directly mixed with polymers. A PDMS film was fabricated by thermal curing of a pre-polymer mixture and was silanized using 3-mercaptopropyltrimethoxy silane (3MPS). A monolayer of CdSe QDs was conjugated to the polymer film through thiol coupling. By repeating the fabrication of PDMS film on the QD layer, silane coupling, and QD conjugation we have successfully prepared an optically transparent multilayer polymer-QD matrix. We selected PDMS as a host polymer considering (1) photoluminescence (PL) of QDs was not affected by PDMS, (2) simple chemical conjugation of QDs to PDMS, (3) flexible structural fabrication, and (4) optical transparency. Formation of individual layers of polymer and QDs was characterized using atomic force microscopy (AFM) imaging, and the presence of QD layers inside the PDMS matrix was identified from fluorescence imaging. Besides a simple demonstration of LBL conjugation of QDs to PDMS, the preparation of an optically transparent polymer-QD matrix where PL properties of QDs are intact would be useful during the construction of QD based optical and optoelectronic devices supported in host matrixes.