Understanding H-aggregates crystallization induced emissive behavior: insights from theory.

We conducted a theoretical investigation into how the molecular stacking effect impacts the photophysical properties in solid phases. Our findings indicated that in the aggregated state, the out-of-plane distorted vibration and imidazole ring stretching vibration of triimidazo-[1,3,5] triazinethe are significantly suppressed, which decreased the Huang-Rhys factor and the corresponding reorganization energy of the photophysical process, as a result, this restricted intramolecular motions and dissipation pathways of excess energy in the excited state, therefore, aggregation induced enhancement emission (AIEE) was found for the title compound from dichloromethane solution to solid state. Analysis of the emission spectrum through discrete spectral lines revealed that the main peak was affected by the vibrational modes with lower frequencies, while the middle-frequency modes influenced the shoulder peak. Furthermore, the predicted intersystem crossing rate (kiosk) and reverse intersystem crossing rate (krisc) using Marcus theory confirmed that an electron can successfully shift from its S1 state to the T1 state, however, the reverse T1 → S1 process can not come into being due to very small krisc (10-6-10-9 s-1), therefore the phosphorescence can be observed. At last, we explored the influence of charge transfer process of the title compound, our theoretical data declared this process can be ignored due to its low transfer rate.

The luminescent and reaction mechanisms of a fluorescent probe for the detection of hypochlorous acid: Insights from theory.

We have designed and synthesized a novel fluorescent probe BMH for detection of hypochlorous acid (HClO), which can increase dramatically the fluorescence intensity and had ultrafast response, a low detection limit and a wide pH range of application. In this paper, we further studied its fluorescence quantum yield and photoluminescence mechanism theoretically. The calculated results indicated the first excited states of BMH and BM (it was the oxidized product by HClO) were bright states with large oscillator strengths, however, due to more larger reorganization energy of BMH, the predicted internal conversion rate kIC of BMH was four orders of magnitude larger than that of BM; moreover, owing to the effect of heavy atom from sulfur atom in BMH, the predicted intersystem crossing rate kisc of BMH was five orders of magnitude larger than that of BM; meanwhile there was no significant difference found between both the predicted radiative rates kr, thus the calculated fluorescence quantum yield of BMH was nearly zero and that of BM was more than 90%, the data showed the BMH had no fluorescence but its oxidated produce BM possessed strong fluorescence. In addition, the reaction mechanism of BMH transforming into BM has been investigated too, according to the potential energy profile, we found that the course of BMH converting into BM consisted of three elementary reactions. The research results revealed the solvent effect can decreased the activation energy, which was more favorable for these elementary reactions.

Morpholinyl dendrimer phthalocyanine: synthesis, photophysical properties and photoinduced intramolecular electron transfer.

In this work, a novel series of morpholinyl dendrimer phthalocyanines were synthesized. Their structures were characterized by 1H NMR, IR, elemental analysis, ESI-MS as well as MALDI-TOF MS. The photophysical properties of these phthalocyanines were studied by UV/Vis and fluorescence spectroscopic methods. The photophysical properties of these dendrimer phthalocyanines exhibited dependence on the number of morpholinyl groups and the central ion. The photoinduced intramolecular electron transfer from the morpholinyl groups to the phthalocyanine ring was evidenced by the remarkably quenched fluorescence intensity and shortened lifetime of the silicon phthalocyanine. This difference in photoinduced intramolecular electron transfer effect for axially and peripherally substituted morpholinyl dendrimer phthalocyanines was also studied. Besides, introduction of morpholinyl groups on the dendrimer structure could enhance water solubility as well as increase the singlet oxygen quantum yield.

Particle formation by supercritical fluid extraction and expansion process.

Supercritical fluid extraction and expansion (SFEE) patented technology combines the advantages of both supercritical fluid extraction (SFE) and rapid expansion of supercritical solution (RESS) with on-line coupling, which makes the nanoparticle formation feasible directly from matrix such as Chinese herbal medicine. Supercritical fluid extraction is a green separation technology, which has been developed for decades and widely applied in traditional Chinese medicines or natural active components. In this paper, a SFEE patented instrument was firstly built up and controlled by LABVIEW work stations. Stearic acid was used to verify the SFEE process at optimized condition; via adjusting the preexpansion pressure and temperature one can get different sizes of particles. Furthermore, stearic acid was purified during the SFEE process with HPLC-ELSD detecting device; purity of stearic acid increased by 19%, and the device can purify stearic acid.