作者:Rafia Azmat、Nida Saleem
DOI:10.1007/s11458-011-0235-8
日期:2011.6
An investigation of the thionine sensitized aerobic photooxidation of thiourea was observed spectrophotometrically at a wavelength of 598 nm. Articles reported two types of reactions which generally occur in the presence of oxygen: 1) Singlet oxygen, produced by dye sensitization due to the hydrolysis that reacts with thiourea to form oxidative products like urea and other sulfur-containing fragments and 2) bleaching of dye, which leads to the reduction. The rate of reaction in all studied parameters followed first order kinetics with respect to maximum absorption of the dye in the visible band region. Reaction kinetics was significantly dependent upon the medium and the reaction accelerated more rapidly at low pH. A direct relation was exhibited between the thiourea concentration and dye sensitizer, which was not pragmatic with the concentration of dye. The reaction was effected by the temperature, and the values of energy parameters suggested that the energy of activation was low while the entropy of activation increases with the rise in temperature, which indicated a highly solvated state of intermediate complex. Lower value of ΔH* and ΔG* at elevated temperature showed that free energy is the driving force for the completion of reaction. A mechanism based on the above findings has been suggested.
通过分光光度法,在波长为598 nm处观察了硫脲对噻吩敏化的有氧光氧化的研究。文章报道了两种通常在氧气存在下发生的反应:1)单线态氧,由染料敏化产生,由于水解与硫脲反应形成氧化产物,如尿素和其他含硫碎片;2)染料的漂白,导致还原。在所有研究参数中,反应速率遵循一阶动力学,与染料在可见光波段的最大吸收有关。反应动力学明显取决于介质,在低pH值下反应加速更快。硫脲浓度与染料敏化剂之间存在直接关系,这与染料浓度无关。反应受温度影响,能量参数值表明活化能较低,而活化熵随温度升高而增加,这表明中间体复合物处于高度溶解状态。高温下ΔH*和ΔG*的较低值表明自由能是完成反应的驱动力。基于上述发现,提出了一个机制。