Iodine release in potassium iodide solution has been investigated under the irradiations of ultrasound and visible light respectively and simultaneously. We have observed that the amount of iodine liberated under the combined irradiation of ultrasound and visible light is larger than the sum of that under the respective irradiations of ultrasound and visible light, indicating a synergistic effect of ultrasound and visible light irradiations. Based on the investigation of the reaction kinetics of iodine liberated, we have ascribed the synergistic effect to the perfect stirring of the photochemical reactor induced by the applying simultaneous ultrasound. The ideal stirring can result in the homogenization of the primary light effect in the whole reaction medium, which induces the acceleration of the photochemical reaction. On behavior of our knowledge, there are few reports on the investigations of utilizing the combination of ultrasonic energy and light energy to accelerate the reaction yield and rate as well as the kinetics of the reaction.
Metallomesogens Ln（bta）3L2 （Ln^3＋： La^3＋, Eu^3＋, and Ho^3＋; bta： benzoyltrifluoroacetonate; L： Schiff base） were prepared. Photoacoustic （PA） spectroscopy was used to study physicochemical properties of the liquid crystalline metal complexes. In the region of ligand absorption, PA intensity increases for Eu（bta）3L2, La（bta）3L2, and Ho（bta）3L2, in that order. It is found that the PA intensity of the ligand bears a relation to the intramolecular energy transfer process. For the first time, phase transitions of Eu（bta）3L2 from glass state to smectic A （SmA） phase and SmA phase to isotropic liquid are monitored by PA and fluorescence （FL） spectroscopy from two aspects： nonradiative and radiative transitions. The results show that PA technique may serve as a new tool for investigating the spectral properties and phase transitions of liquid crystals containing metal ions.
Yue-tao YangJun-jia LiXiao-jun LiuShu-yi ZhangJing Liu
Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic （PA） spectroscopy was used to study the spectral properties and phase transitions of liquid crystalline metal complexes. It was found that PA intensity of the ligand had a relationship with the probability of nonradiative transitions, which increased in the order of Eu（tta）3L2〈La（tta）3L2〈 Tb（tta）3L2〈Er（tta）3L2. The relaxation processes of the complexes were studied in depth from two aspects： radiative and non-radiative processes, combining with their fluorescence spectra. Phase transitions of europium（m） and erbium（m） complexes, in the temperature range of 383-358 K, could be clearly monitored by both PA amplitude and PA phase signals. As the temperature crossed the transition point, PA amplitude showed a minimum and PA phase a maximum. The results indicated that PA technique could serve as a new tool for investigating the physicochemical properties of liquid crystals containing metal ions.
