Photoswitchable dual-color fluorescent particles from seeded emulsion polymerization and role of some affecting parameters on FRET process

Here, azocarbazole ethyl acrylate (AzoCzEA) and spiropyran ethyl acrylate (SPEA) chromophores were copolymerized with methyl methacrylate through seeded emulsion polymerization to obtain photoswitchable dual-color fluorescent polymer particles. The proposed strategy introduces spectacular advantages on incorporation of the desired values of hydrophobic AzoCzEA and hydrophilic SPEA to the polymer backbone in a one-pot two-step polymerization reaction that was a serious restriction before. Inclusion of various ratios of AzoCzEA to SPEA into the polymer particles was investigated by absorption intensity measurement. UV-Vis analysis of the obtained polymer particles and their solutions (in different solvents) demonstrate that the polymer particles dispersion in water is preferred due to the alleviated surrounding effects. The effect of solvent polarity and zwitterionic nature of MC isomer on absorption intensity of AzoCzEA and occurrence of FRET phenomenon are discussed before and after UV irradiation at 365 nm and it is concluded that polymer particles have outstanding benefits over their solutions. Particle size and size distribution of dual-color particles have been studied by SEM and DLS analyses and it was found that particles size shows an increasing trend with the increase in SPEA concentration, and consequently enhances undesired light scattering. Efficiency of fluorescence quenching for the optimized sample was obtained from fluorescence emission analysis and found to be 873% for the optimum sample. (C) 2017 Elsevier Ltd. All rights reserved.