Effect of synthesis variables on the fluorescence properties of CdSe-polystyrene latexes

The development of photoluminescent materials based on the incorporation of quantum dots (QDs) into polymeric latexes has gained importance due to the multiple potential applications. Through the process of miniemulsion polymerization it is possible to encapsulate quantum particles into polymer matrix to provide both chemical stability and to maintain emission properties. The polymerization process was achieved with continuous magnetic stirring and nitrogen atmosphere. Cetyl trimethylammonium bromide (CTAB) was used as surfactant at concentration levels of 1.3 × 10^-3, 3.2 × 10^-3 and 5.4 × 10^-3 M. The initiator 2,2-azobisisobutyronitrile (AIBN) was used at 0.50 and 0.75 wt% and CdSe QDS were used at 0.075, 0.15 and 0.225 wt%, both in relation to monomer content. A STEM study on the composite latexes and later a statistical study on the measurement of polymer particle diameter let us corroborate that the increment in surfactant concentration produces a decrement in polymer particle size. The obtained composite latexes were stable and showed fluorescence by excitation with UV light. The spectrofluorometry studies indicated that in composite latexes fluorescent emission was a function of polymer particle size, showing higher intensity those formulations with smaller surfactant concentrations and bigger polymer particle size.