Strongly photoluminescent Eu(III) tetrazolate ternary complexes with phosphine oxides as powerful sensitizers

The Eu(III) cation forms electrically neutral photoluminescent complex with 5-(2-pyridyl-1-oxide)tetrazolate (PTO) anion. Although the photoluminescence properties of such tertiary Eu(III) and Tb(III) complexes were not as high (13 and 31% photoluminescence quantum yield, respectively) as reported for other diketonate lanthanide complexes probably because of high number of nitrogen atoms involved in PTO which leads to attachment of water molecules, reducing the luminescence quantum yield with vibrational and rotational quenching. Here, we report the removal of quencher molecules from the coordination sphere of tris–europium tetrazolate oxide complex by replacing them with various phosphine oxides which leads to improved photoluminescence quantum yield for the complexes by acting as auxiliary co-ligands with that of the main antenna 5-(2-pyridyl-1-oxide)tetrazolate. The coordination sphere in these complexes can be complemented by aromatic phosphine oxides to provide highly photoluminescent Eu(III) complexes. The highest quantum yield was 38% in 3 [Eu(PTO)₃·DPEPO](H₂O)₅ containing bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) as compared to tris–europium complex with 5-(2-pyridyl-1-oxide)tetrazolate.     

Cascade Processes in Muonic Hydrogen Atoms

The QCMC scheme created earlier for cascade calculations in heavy hadronic atoms of hydrogen isotopes has been modified and applied to the study of cascade processes in the μp muonic hydrogen atoms. The distribution of μp atoms over kinetic energies has been obtained and the yields of K-series X-rays per one stopped muon have been calculated. Comparison with experimental data indicated directly that for muonic and pionic atoms new types of non-radiative transitions are essential, while they are negligible for heavy (kaonic, antiprotonic, etc.) atoms. These processes have been considered and their probabilities have been estimated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Scenedesmus dimorphus (Turpin) Kützing growth with digestate from biogas plant in outdoor bag photobioreactors

Digestate coming from an Anaerobic Digestion unit in a Biogas Plant, feeded on cow manure and vegetable waste from markets, has been used. About 8–35 L polyethylene transparent bags have been employed as cultivation container, outdoor. Different aliquots of digestate, alone or mixed with commercial liquid fertiliser, were employed to cultivate in batch Scenedesus dimorphus, a freshwater green microalga, in the ENEA facilities of Casaccia Research Center, near Rome, Italy. The cultivation period was June–July 2013. The average daily yields of dry microalgae biomass varied from 20 mg/L/d to 60 mg/L/d, mean 38.2 mg/L/d. Final dry biomass concentration varied from 0.18 to 1.29 g/L, mean 0.55 g/L. S. dimorphus proved to be very efficient in removing N and P from the culture medium. Another fact emerged from these trials is that S. dimorphus inner composition resulted to be variable in response to the tested different culture conditions.     

Optimization and development of a high‐performance liquid chromatography method for the simultaneous determination of vitamin E and carotenoids in tomato fruits

A simple and reliable high‐performance liquid chromatography method was developed and validated for the simultaneous determination of lipophilic antioxidants in tomato fruits using C₃₀ column operated at 15°C and a gradient mobile phase based on acetonitrile/methanol/dichloromethane in a total run time of 30 min. Diode array and fluorescence detectors were used respectively for the detection of carotenoids (lutein, zeaxanthin, cryptoxanthin, lycopene, and β‐carotene) and vitamin E analogs (α‐, β‐, γ‐, and δ‐tocopherols, and tocotrienols). The best extraction yield of analytes in tomato fruits was achieved by employing ethyl acetate/hexane (1:1, v/v) after several treatments with various solvents. In addition, low extraction yields were obtained for carotenoids compared to tocopherols by adopting solid‐phase extraction as a second clean‐up step. The method was validated on the basis of recovery, precision, linearity, and limit of detection and quantification using spiked tomato samples. The method was applied to cherry and medium‐sized tomato fruits. Lycopene was found to be present in largest amount in tomato pulp, followed by β‐carotene and lutein. Due to its simplicity, rapidity, and efficiency, the method is suitable for routine analysis of lipophilic antioxidants in tomato fruits, and may also be applied to other vegetables of similar phytochemical profiles.     

Synthesis,photophysical and photochemical properties of tetra- and octa-substituted gallium and indium phthalocyanines

The synthesis, photophysical and photochemical properties of the tetra- and octa-[4-(benzyloxyphenoxy)] substituted gallium(III) and indium(III) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, ¹H NMR spectroscopy and electronic spectroscopy. General trends are described for quantum yields of photodegredation, fluorescence quantum yields and lifetimes, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO). Substituted indium phthalocyanine complexes (7b–9b) showed much higher quantum yields of triplet state and shorter triplet lifetimes, compared to the substituted GaPc derivatives due to enhanced intersystem crossing (ISC) in the former. The gallium and indium phthalocyanine complexes showed phototransformation during laser irradiation due to ring reduction. The singlet oxygen quantum yields (Φ_Δ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.51 to 0.94. Thus, these complexes show potential as photodynamic therapy of cancer.     

Tuning Electron-Withdrawing Strength on Phenothiazine Derivatives: Achieving 100 % Photoluminescence Quantum Yield by NO2 Substitution

The weak fluorescence (quantum yield <1 % in cyclohexane) of phenothiazine ( PTZ ) impedes its further application. In addition, the nitro group (NO₂) is a well-known fluorescence quencher. Interestingly, we obtained a highly fluorescent chromophore by combining these two moieties, forming 3-nitrophenothiazine ( PTZ-NO₂ ). For comparison, a series of PTZ derivatives bearing electron-withdrawing groups (EWGs; CN and CHO) or electron-donating groups (EDGs; OMe) at the 3-position have been designed and synthesized. The phenothiazines bearing EWGs exhibited enhanced emission compared with the parent PTZ or EDG derivatives. Computational approaches unveiled that for PTZ and PTZ-OMe , the transitions are from HOMOs dominated by π orbitals to LUMOs of mixed sulfur nonbonding–π* orbitals, and hence are partially forbidden. In contrast, the EWGs lower the energy level of the lone-pair electrons on the sulfur atom, thereby suppressing the mixing of the nonbonding orbital with the π* orbital in the LUMO, such that the allowed ππ* transition becomes dominant. This work thus demonstrates a judicious chemical design to fine-tune the transition character in PTZ analogues, with PTZ-NO₂ attaining 100 % emission quantum yields in nonpolar solvent.     

离子速度成像方法研究C8H17Br分子的光解动力学

用离子速度成像方法, 研究了长链C8H17Br分子在234 nm激光下的光解过程. 通过2+1共振增强多光子电离探测了两种光解产物Br*(2P1/2)和Br(2P3/2), 得到了它们的相对量子产率. 从光解产物Br*(2P1/2)和Br(2P3/2)的速度图像得到了能量和角度分布. 并根据相对量子产率和角度分布, 计算了不同解离通道的比例. 实验发现C8H17Br分子解离过程中大部分能量都转化为内能, 该能量分配可以较好地用软反冲模型来解释, 并分析了这种能量分配跟烷基大小的关系.     

Photochemical study of electrocyclization of 4-aryl-5-hetarylimidazolones for information optical recording

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Oxidation of polyethylene under irradiation at low temperature and low dose rate. Part I. The case of “pure” radiochemical initiation

As part of a study on the kinetic modelling of polyethylene oxidation under irradiation at low temperature and low dose rate, this first part deals with the kinetic regime in which thermal initiation, linked to hydroperoxide decomposition, is negligible compared to radiochemical initiation due to polymer radiolysis. The kinetic analysis is based on results published 30 years ago by Decker, Mayo and Richardson. A small modification of their mechanistic scheme, consisting in the introduction of a non-terminating bimolecular combination of PO₂ radicals, leads to a more consistent set of radiochemical yield values. The most significant change is a decrease in the radiochemical yield of radicals G_i from 10 to 8. At 45 °C, termination of PO₂ radicals is not very efficient: 35-40% of the PO₂ + PO₂ encounters are non-terminating, 75% of the termination events lead to peroxide bridges, the rest is a disproportionation according to the Russell mechanism.     

Comparative studies of photophysical and photochemical properties of solketal substituted platinum(II) and zinc(II) phthalocyanine sets

A complete set of platinum(II) solketal substituted phthalocyanines has been synthesized and characterized. To evaluate their potential as Type II photosensitizers for photodynamic therapy, comparative studies of their photophysical and photochemical properties with analogous zinc(II) series have been achieved: electronic absorption, fluorescence quantum yields, lifetimes, and fluorescence quenching by benzoquinone, as well as singlet oxygen generation and photodegradation. It appears that platinum(II) phthalocyanines are worth being used as Type II photosensitizers, as they exhibit good singlet oxygen generation and appropriate photodegradation.