Complexes of silver with histidine and imidazole investigated by the calorimetric and potentiometric methods

The stability constants and enthalpies of formation of silver (I) complexes with histidine and imidazole were determined. Two types of complexes were found: AgL+ and AgL+ 2 . The second is much more stable that is evidenced by the higher stability constants and enthalpies of formation. For the two systems, the respective constants and enthalpies are very close one to another that suggests similar complexation mechanisms. Most probably, the linear complexes through the N-3 pyridinic atoms are being formed. The calorimetric and potentiometric methods gave virtually the same results for the system silver + imidazole. However, the potentiometric method failed for the histidine system. The molecule of histidine has three protonation spots, two of these probably do not take part in the complexation but their protonation equilibria may shift upon joining the ions of silver and influence the pH of the system in that way

Long-lived emission from Eu3+:PbF2 nanocrystals distributed into sol-gel silica glass

This paper reports an optical investigation of Eu3+:PbF2 nanocrystals distributed into silica glasses fabricated by sol–gel methods. The sample microstructure was investigated using scanning transmission electron microscopy. The β-cubic PbF2 crystalline phase was identified using X-ray diffraction analysis. The observed emission bands correspond to 5D0 → 7FJ (J = 0–4) transitions of Eu3+. The spectroscopic parameters for Eu3+ ions were determined based on excitation and emission measurements as well as luminescence decay analysis. Emission originating from 5D0 state of Eu3+ ions in sample containing PbF2 nanocrystals is long-lived in comparison to precursor sol–gel silica glasses

Influence of Mixed Cationic-nonionic Surfactant Systems on the Spectral Properties of C.I. Mordant Blue 29 and Its Complexes with Iron(III)

<div>Interactions of the anionic form of C.I. Mordant Blue 29 with cationic and nonionic surfactants have been studied by</div><div>absorption spectroscopy. The dye interacts strongly with oppositely charged surfactants in the pre-micellar concentration range with an accompanying change in its spectral properties, while its interaction with the polyoxyethylene group of nonionic surfactants does not have such remarkable effects. In ternary mixtures, however, the influence of the polyoxyethylene group on the optical properties of C.I. Mordant Blue 29 tetradecyltrimethylammonium bromide and C.I.</div><div>Mordant Blue 29-octadecyltrimethylammonium chloride systems is quite different. In addition, the influence of the</div><div>interaction between the HL3– form of C.I. Mordant Blue 29 and the surfactants on the formation of chelate complexes with iron(III) has been studied. The optimized structures of Fe-Mordant Blue 29 complexes are also reported herein.</div><div>Geometries have been calculated by the Hartree–Fock method with the cc-pVDZ basis set.</div