Luminescent quantum-dot-sized conjugated polymer nanoparticles-nanoparticle formation in a miniemulsion system

The synthesis of semiconducting polymer nanospheres (SPNs) by miniemulsion methods has been reported previously, (1,2) however the resulting materials have typically been significantly larger than quantum dots, the nanomaterial of choice for cell imaging. In the current work, we aimed to obtain quantum-dot-sized poly(ethylene-glycol) (PEG) functionalised SPNs by optimising the miniemulsion method reported previously. (1,3) We report that PEG functionalised SPNs with a narrow distribution of quantum dot sizes were successfully synthesised, with mean diameters ranging between 2 and 5 nm. PEG-dithiol was also used in one variant of the syntheses, allowing the purified sample to be examined by mass spectrometry (using sulfur as a reporter), confirming the inclusion of a significant number of PEG molecules in the nanoparticles. Also, the presence of PEG was found to significantly affect the yield of the reaction, suggesting it played a role in nanoparticle formation. The nanoparticles were characterized by TEM, absorption and emission spectroscopy, and were found to be stable in solution for months.