Optimization of the heterogeneous Fenton-oxidation of the model pollutant 2,4-xylidine using the optimal experimental design methodology

Among advanced oxidation processes (AOP), the photochemically enhanced Fenton reaction (photo-Fenton) may be particularly effective for the treatment of industrial waste water, and the possibility to use solar light is an additional advantage of this process. In the present work, a Fe³⁺-exchanged zeolite Y was tested as a heterogeneous photo-Fenton catalyst for the degradation of the model organic pollutant, 2,4-xylidine. The performance of the catalyst was investigated using a bench photochemical reactor as well as solar reactors. The incident solar radiant powers (determined by ferrioxalate actinometry) showed linear correlations with the outputs of a Si-photodiode and a bolometer mounted on the solar unit, and could therefore be easily estimated from the on-line observation of the sensor outputs. The experimental design methodology was used for planning the experiments under normalized conditions and for modeling the rates of 2,4-xylidine oxidation as a function of the concentrations of the additives (Fe³⁺-exchanged zeolite catalyst and hydrogen peroxide). Although a direct quantitative comparison between both reactors is difficult (different geometries and volumes, different spectral distribution of the radiation sources), the performance of the solar reactor appears to compare favorably with that of the bench photochemical reactor.     

Toward High Performance Photoelectrochemical Water Oxidation: Combined Effects of Ultrafine Cobalt Iron Oxide Nanoparticle

Photocleavage of H₂O into clean and storable H₂ fuel by photoelectrochemical (PEC) cell is a vital part of the sustainable hydrogen economy. However, thus far one of the limitations confronted by PEC cell to preferable performance is the insufficient behavior of photoanode for water oxidation half‐reaction. One of the strategies to elevate the photoanode performance is integrating with an oxygen evolution catalyst (OEC) to remove the bottleneck of the water oxidation kinetics. Herein, an ultrafine cobalt iron oxide (CIO) nanocrystalline is reported as a novel OEC for photoelectrochemical water splitting. The CIO evenly distributing on the surface of hematite nanorod arrays not only greatly facilitates the surface hole injection, but also promotes the charge separation along with passivating the surface states. Such combined effects of CIO finally lead to an impressive 1.71 fold enhancement on the photocurrent density at 1.23 V_RHE and ≈170 mV negative shift of onset potential, even overwhelms the commonly utilized Co‐Pi. Along with its excellent long‐term stability, the CIO possesses a great potential application in PEC water splitting devices.     

The effect of co-initiator structure on photoinitiating efficiency of photoredox couples composed of quinoline[2,3-b]-1H-imidazo[1,2-a]pyridinium bromide and phenoxyacetic acid or N,N-dimethylaniline derivatives.

Summary  Two groups of electron donors (phenoxyacetic acid derivatives, PAADs, and the family of N,N-dimethylaniline derivatives DMADs) in combination with quinoline[2,3-b]-1H-imidazo[1,2-a]pyridinium bromide (QIPB) were applied as photoinitiator for free radical polymerization induced with UV emission of an argon-ion laser (351 and 361 nm). Analysis of the data obtained for the initial time of photoinitiated polymerization indicates that both, the rate of electron transfer process between QIPB and tested co-initiators as well as the structure of obtained free radical can affect the overall photoinitiation ability of tested photoredox pairs.     

Control and selectivity of photosensitized singlet oxygen production: challenges in complex biological systems

Singlet molecular oxygen is a reactive oxygen species that plays an important role in a number of biological processes, both as a signalling agent and as an intermediate involved in oxidative degradation reactions. Singlet oxygen is commonly generated by the so-called photosensitization process wherein a light-absorbing molecule, the sensitizer, transfers its energy of excitation to ground-state oxygen to make singlet oxygen. This process forms the basis of photodynamic therapy, for example, where light, a sensitizer, and oxygen are used to initiate cell death and ultimately destroy undesired tissue. Although the photosensitized production of singlet oxygen has been studied and used in biologically pertinent systems for years, the photoinitiated behaviour is often indiscriminate and difficult to control. In this Concept, we discuss new ideas and results in which spatial and temporal control of photosensitized singlet oxygen production can be implemented through the incorporation of the sensitizer into a conjugate system that selectively responds to certain triggers or stimuli.     

Model systems for activation of nucleic acid encoded prodrugs

The development of more selective chemotherapeutic agents for benign treatments of malicious diseases is highly desirable. In recent years model systems for the release of small molecule drugs from nucleic acid conjugates by templated chemical or photochemical reactions have been designed. Common for these systems is that the stoichiometric or catalytic drug release is controlled by the highly selective hybridization between complementary strands of nucleic acids. Herein, the concepts of the new field of nucleic acid templated release reactions are outlined.     

二硫代水杨酸衍生物对光固化材料性能的影响

设计、合成了一种二硫代水杨酸衍生物(MAPBS),详细研究了MAPBS对丙烯酸酯类单体光聚合动力学及其聚合物膜体积收缩、耐热性能及硬度的影响。研究结果表明,在365 nm LED光源照射下,MAPBS能够引发甲基丙烯酸酯类单体聚合和降低聚合物膜体积收缩。随着MAPBS含量的增加,光聚合体系的双键转化率和聚合速率随之增加,分别达到64.9%和1.19%/s,而体积收缩呈现先降低再增加的趋势,聚合物膜热稳定性略微降低,硬度略有增加。MAPBS兼具引发和降低体积收缩的双重功能,在LED光聚合体系表现出一定的应用潜力。     

PHOTOCHEMICAL REACTION OF CHRYSENE IN ACETONITRILE/WATER

The photochemical reaction of chrysene under UVA light irradiation in acetonitrile/water yields 1,4- and 5,6-chrysenequinones and one lactone, H-benzo[d]naphtha[1,2-b]pyran-6-one. Solvent-dissolved oxygen is necessary for the photolysis. The presence of TiO₂, Al₂O₃, La₂O₃, KI, or I₂ decreased the photolysis rate. The free radical scavenger, Na₂S₂O₃, greatly suppressed the chrysene photolysis, indicating that a free radical process was involved. Also, a self-catalysis phenomenon for chrysene photolysis was observed and investigated.