Highly fluorescent organic nanoparticles, films and crystals for sensing and lasing applications

In this work the photophysical properties of novel phenylenediacetonitrile (PDACN) derivatives bearing systematically introduced different side-groups are investigated in their different forms (liquid and solid solution, neat films and nanoparticles). It was determined that emission properties can be tuned in a controlled manner by changing film/nanoparticle morphology by varying preparation conditions or altering molecular structure. Demonstrated tunability of fluorescence spectra and intensity via induced changes in morphology encourages technological application of PDACN compounds in threshold temperature or volatile organic vapour fluorescence sensing. Although organic materials expressing efficient fluorescence and high radiative decay rates have been of interest as a gain medium in lasing applications for a few last decades, no systematic studies of amplified spontaneous emission (ASE) concentration behaviour in such a wide concentration range (0.1 – 100%) were carried out so far. Thorough assessment of concentration effects on ASE properties of new fluorene- and benzo[c]fluorene-cored oligomers allowed to achieve extremely low ASE thresholds at very high compound concentrations and in the neat amorphous films, which are required for future organic laser applications. Moreover, new bifluorene derivatives bearing different linking groups were inspected as building materials for highly fluorescent organic single crystals, attractive for electrically pumped laser applications. Control of intermolecular interactions, achieved by chemical structure design, allowed to demonstrate record low ASE threshold values (700 W/cm2) in organic single crystals grown by physical vapour transport