Speciation, Luminescence, and Alkaline Fluorescence Quenching of 4-(2-methylbutyl)aminodipicolinic acid (H2MEBADPA)

4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa\u27s) and photophysical measurements. The pKa\u27s were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pKas and quenching constants, the fluorescent intensity of MEBADPA2– has been successfully modeled as a function of pH

Spectre Raman de résonance et fonction de l'énergie potentielle du bromure d'iode en solution

Le spectre Raman de résonance de IBr est enregistré dans divers solvants. Une progression de 17 harmoniques a pu être observée, ce qui permet le calcul, avec une bonne précision, des constantes spectroscopiques ωe et d'anharmonicité ωexe et ωeye, ainsi que la fonction de l'énergie potentielle de IBr en solution : V = [math] x 2 x 105q2 — 1,49 x 1013q3 + 1,55 x 1021q4 La diminution de l'anharmonicité de IBr en solution dans les solvants non ou peu polaires est interprétée par une contribution importante des forces répulsives entre soluté et solvant

Endommagement combine (diffusion de l'eau sous contraintes mecaniques) de materiaux composites a matrice epoxyde

INIST AR 13443 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc