CdS-oleic acid quantum dots as long-wavelength photoinitiators in organic solvent and preparation of luminescent, colloidal CdS/polymer nanocomposites

Abstract

Photoexcitation of luminescent semiconductor quantum dots (QDs) generates an electron–hole pair, which can be utilized for photoinitiation of radical polymerization reactions. Here, oleic acid coated CdS QDs (CdS–OA) are demonstrated as successful photoinitiators in the absence of a protic solvent or a hole scavenger for the first time. This provides photopolymerization of hydrophobic methyl methacrylate in toluene, providing colloidal and strongly luminescent CdS/poly(methacrylic acid) (PMMA) hybrid structures with improved stability of the CdS. Besides, successful photopolymerization of poly(ethylene glycol)diacrylate at different excitation windows (320–480 and 400–500 nm) is demonstrated. This indicates that CdS–OA can act as a long-wavelength initiator. Electron spin resonance (ESR) studies and control experiments suggest decarboxylation of the oleic acid as the initial source of the free radical. This method represents a unique and very simple way to create luminescent, small, stable, and colloidal QD/polymer hybrids.