Light scattering and spectroscopic studies of polymerization processes. 2. Thermal polymerization of styrene

1982 ◽  
Vol 15 (2) ◽  
pp. 561-569 ◽  
Author(s):  
Benjamin Thomas Peng Nien Chu ◽  
Georg Fytas
Keyword(s):  
Light Scattering ◽  
Spectroscopic Studies ◽  
Thermal Polymerization

scholarly journals Spectroscopic Studies of Dual Fluorescence in 2-(4-Fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole: Effect of Molecular Aggregation in a Micellar System

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2861 ◽  
Author(s):  
Grzegorz Czernel ◽  
Arkadiusz Matwijczuk ◽  
Dariusz Karcz ◽  
Andrzej Górecki ◽  
Agnieszka Niemczynowicz ◽  
...  
Keyword(s):  
Light Scattering ◽  
Fluorescence Spectra ◽  
Single Photon ◽  
Spectroscopic Studies ◽  
Fluorescence Probes ◽  
Molecular Aggregation ◽  
Micellar System ◽  
Dual Fluorescence ◽  
Fluorescence Measurements ◽  
Ionic Detergent

The article presents the results of spectroscopic studies focused on a selected compound from the 1,3,4-thiadiazole group—2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thia-diazole (FABT)—in a micellar system formed by Triton X-100, a non-ionic detergent. Fluorescence measurements revealed the phenomenon of dual fluorescence whose emergence is related to the particular molecular organisation of the compound, which depends both on the concentration of the detergent and, most of all, the concentration of the compound itself. Dual fluorescence of FABT in a micellar system was observed for the compound dissolved in a methanol aqueous system, i.e., an environment wherein the dual fluorescence of the compound had never been reported before. Based on the interpretation of UV-Vis electronic absorption, resonance light scattering (RLS), emission and excitation fluorescence spectra, as well as measurements of dynamic light scattering (DLS) and Principal Component Analysis (PCA), we were able to relate the occurrence of this effect to the process of molecular aggregation taking place between FABT molecules in the micellar system in question. Results of fluorescence spectra measurements and time-correlated single photon counting (TCSPC) indicate that dual fluorescence occurs at detergent concentrations necessary to form micellar systems, which in turn facilitate the process of aggregation of FABT molecules. The correlation between the observed fluorescence effects and the previous measurements performed for analogues from this group suggests the possibility of charge transfer (CT) within the range of detergent concentrations wherein the aforementioned fluorescence effects are observed. It ought to be emphasised that this type of fluorescence effects are relatively easy to induce, which predisposes this groups of fluorophores as ideal fluorescence probes in the context of biological samples.

Spectroscopic studies of aggregation behavior of meso-tetra(4-hydroxyphenyl)porphyrin in aqueous AOT solution

2008 ◽  
Vol 12 (02) ◽  
pp. 101-108 ◽  
Author(s):  
Hongmin Ma ◽  
Shuting Sun ◽  
Xin Chen ◽  
Dan Wu ◽  
Peihua Zhu ◽  
...  
Keyword(s):  
Surface Tension ◽  
Light Scattering ◽  
Aqueous Solutions ◽  
Absorption Spectroscopy ◽  
Fluorescence Anisotropy ◽  
Soret Band ◽  
Spectroscopic Studies ◽  
Resonance Light Scattering ◽  
Scattering Signal ◽  
Resonance Light Scattering Technique

The interactions of two amphiphilic porphyrins with anionic surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in aqueous solutions were studied by UV-vis absorption spectroscopy, fluorescence spectroscopy, resonance light scattering technique, fluorescence anisotropy and surface tension measurements. The two porphyrins, meso-tetra(4-hydroxyphenyl)porphyrin (THPP) and meso-tetra(3,5-dibromo-4-hydroxylphenyl)porphyrin (T(DBHP)P), exist as irregular aggregates in aqueous solutions with a broad and low absorption peak near the maximum of monomer peak. The interaction of THPP with AOT leads to the formation of a fluorescent aggregate of porphyrin which was assigned as J-type aggregate according to exciton theory. A long red-shifted Soret band together with a new strong Q-band, a broad emission peak and a sharply peaked resonance light scattering signal are observed for this J-aggregate. The formation of J-aggregate is independent of the initial THPP concentration and can be influenced greatly by ionic strength. The aggregation kinetics has been investigated by UV-vis absorption spectroscopy and fluorescence anisotropy. Conversion of the porphyrin monomers to J-aggregate is observed. The addition of THPP increases the surface tension of solution and changes the critical micelle concentration of AOT. J-aggregate was not observed for T(DBHP)P in AOT solutions which only shows solubilization. The mechanism of aggregation was discussed.

Sign in / Sign up

Export Citation Format

Share Document