Showing papers by "Zsombor Miskolczy published in 2015"

Reversible Nanoparticle–Micelle Transformation of Ionic Liquid–Sulfonatocalix[6]arene Aggregates

Abstract: The effect of temperature and NaCl concentration variations on the self-assembly of 1-methyl-3-tetradecylimidazolium (C14mim+) and 4-sulfonatocalix[6]arene (SCX6) was studied by dynamic light scattering and isothermal calorimetric methods at pH 7. Inclusion complex formation promoted the self-assembly to spherical nanoparticles (NP), which transformed to supramolecular micelles (SM) in the presence of NaCl. Highly reversible, temperature-responsive behavior was observed, and the conditions of the NP–SM transition could be tuned by the alteration of C14mim+:SCX6 mixing ratio and NaCl concentration. The association to SM was always exothermic with enthalpy independent of the amount of NaCl. In contrast, NPs were produced in endothermic process at low temperature, and the enthalpy change became less favorable upon increase in NaCl concentration. The NP formation was accompanied by negative molar heat capacity change, which further diminished when NaCl concentration was raised.

Effect of host–guest complex formation on the fluorescence of 6-methoxy-1-methyl-quinolinium cation with 4-sulfonatocalix[4]arene: utilization as a fluorescent probe for the study of difenzoquat binding

Abstract: The complexation of the highly fluorescent 6-methoxy-1-methyl-quinolinium (C1MQ) and the widely used herbicide, difenzoquat (DFQ), with 4-sulfonatocalix[4]arene (SCX4) macrocycle was studied by isothermal titration calorimetry, fluorescence and NMR spectroscopy in aqueous solutions at 298 K. Both guests produced 1:1 complexes with SCX4, but the binding affinity of C1MQ was more than one order of magnitude larger than that of DFQ in neutral medium. The higher stability of C1MQ-SCX4 complex originated from the significant enthalpy gain upon its formation. The encapsulation of C1MQ in SCX4 in the ground state resulted in an efficient fluorescence quenching due to electron transfer from the host to the excited guest. The marked difference in the fluorescence quantum yields for free and bound C1MQ was used to detect the competitive complexation of DFQ in SCX4.