Poli(propileno-imino) dendrimerų UV spektrų savybės

Ištirti įvairių generacijų (G 1... GS) poli(propileno-imino) (PPI) dendrimerų, funkcionalizuotų aminogrupėmis, tirpalų dichlorometane sugerties spektrai. Nustatyta būdinga visiems ištirtiems junginiams dviguba juosta ties 270-290 nm ir jos kitimas priklausomai nuo dendrimerų generacijos ir tirpalo koncentracijos. Gauta, kad sugertis priklausė tiesiškai nuo dendrimero molinės koncentracijos tirpale, esant nedidelėms 1.10-5 M koncentracijoms. Aukštesnės generacijos (G3 ... GS) dendrimerų tirpalai pasižymėjo didele sklaida, kuri atitiko Rayleigh sklaidos dėsningumusThe UV optical spectra of amine terminated poly(propylene-imine) (PPI) dendrimers of generations G1 to G5 were investigated experimentally. The occurrence of double band at 270–290 nm in absorption spectra of amine terminated dendrimer and the dependence of the spectra on the generation number and concentration in dichloromethane solution were discussed. The lineshape of double band was similar in the sequence G1 to G5, though some redistribution of the intensity of components was observed. A linear dependence of the absorbance in the double band was determined in the solutions at low concentrations of order 1·10−5 M. Experimental data have indicated that double band is caused by several optical transitions related to the core electronic excitations. A significant Rayleigh light scattering was found for higher dendrimer generationsPuslaidininkių fizikos institutasVilniaus universiteto Teorinės fizikos ir astronomijos institutas, [email protected] Didžiojo universitetasŠvietimo akademij

Physical studies of porphyrin-infiltrated opal crystals

Artificial opals made of silica spheres and infiltrated with aqueous solution of iron porphyrin (FeTPPS) possessing the absorption band in a visible spectral range were studied. The structural, optical and magnetic properties of composite structures were investigated. Bulk samples of opal structure were obtained by sedimentation technique from colloidal solution Of SiO2 spheres of diameter 240 and 245 nm. The structure of the samples was examined by atomic force microscopy. The properties of photonic crystals were demonstrated by optical measurements in transmission and reflection modes. The stop band was observed in the region 510-550 nm. In samples annealed at 900 degrees C the width of the stop band increased to similar to 70 nm. Aqueous solutions of FeTPPS of concentration similar to 1.0 mM and various pH-values were used for infiltration. The infiltration has led to a change of photonic characteristics, position of the stop band and dependence on light incidence angle. The absorption bands typical of FeTPPS were observed in the vicinity of the stop band. The photonic properties of infiltrated opal structures were determined to depend on the acidity of aqueous solution, which was used in technological procedure. Magnetic properties of FeTPPS-infiltrated opal samples, which have been studied at 5-300 K in magnetic fields up to 5 T, were discussedPuslaidininkių fizikos institutasVytauto Didžiojo universitetasŠvietimo akademij