Enhanced Photooxidation of Hydroquinone by Acetylacetone, a Novel Photosensitizer and Electron Shuttle

Abstract

Quinones are important electron shuttles as well as micropollutants in the nature. Acetylacetone (AA) is a newly recognized electron shuttle in aqueous media exposed to UV irradiation. Herein, we studied the interactions between AA and hydroquinone (QH 2 ) under steady-state and transient photochemical conditions to clarify the possible reactions and consequences if QH 2 and AA coexist in a solution. Steady-state experimental results demonstrate that the interactions between AA and QH 2 were strongly affected by dissolved oxygen. In O 2 -rich solutions, the phototransformation of QH 2 was AA-independent. Both QH 2 and AA utilize O 2 as the electron acceptor, but in O 2 -insufficient solutions, AA became an important electron acceptor for the oxidation of QH 2 . In all cases, the coexistence of AA increased the phototransformation of QH 2 , whereas the decomposition of AA in O 2saturated and oversaturated solutions was inhibited by the presence of QH 2 . The underlying mechanisms were investigated by a combination of laser flash photolysis (LFP) and reduction potential analysis. The LFP results show that the excited AA serves as a better electron shuttle than QH 2 . As a consequence, AA might regulate the redox cycling of quinones, leading to significant effects on many processes, ranging from photosynthesis and respiration to photodegradation.

UV/FeⅡNTA as a novel photoreductive system for the degradation of perfluorooctane sulfonate (PFOS) via a photoinduced intramolecular electron transfer mechanism

“…Nanosecond laser flash photolysis for the detection of eaqwas performed using an LP980 Edinburgh instrument (UK) with laser excitation at 266 nm from a Surelite I-10 Q-Switched Nd:YAG laser (35 mJ). Components of the laser flash photolysis apparatus were as described by Jin et al [48]. Detailed information about the instrument and experiment is available in the SI.…”

Diketone and UV based advanced oxidation/reduction technologies: molecular mechanisms and research advances

“…与醌相比, 3 [64] . 在光化学体系中, 当溶液中 O2 充足时, 激发态 AA 和氢醌都是 O2 的电子供体; 缺 氧时, 激发态 AA 取代 O2 作为氢醌的电子受体促进氢 醌的氧化转化 [65] . 上述结果说明 AA 是比醌更强的光 致电子穿梭体 [65] .…”

“…在光化学体系中, 当溶液中 O2 充足时, 激发态 AA 和氢醌都是 O2 的电子供体; 缺 氧时, 激发态 AA 取代 O2 作为氢醌的电子受体促进氢 醌的氧化转化 [65] . 上述结果说明 AA 是比醌更强的光 致电子穿梭体 [65] . 在 UV/AA 体系中, As(III)被氧化为 As(V), 与此同时, 溶解氧浓度下降、H2O2 生成, 充分 说明 3 (AA) * 作为 As(III)与 O2 的电子穿梭体在发挥作 用(图 8a 和 8b) [25] .…”

“…原因在于烯醇式结构能与金属生成电荷转移复合 物, 从而促进其氧化还原转化. [65] ; (c) AAs 光还原 Cr(VI)的假一级速率常数, [AAs] = 0.5 mmol/L; [Cr(VI)] = 0.1 mmol/L; 光强: 1.25 mW/cm 2 (254 nm) [83] (网络版彩图) Figure 11 (a) Schematic diagram of the ketone-enol tautomerization for the AA derivatives (AAs) [65] ; (b) UV absorption spectra of individual BQ and BQ-AAs mixtures after 36 h incubated. The dotted horizontal line shows the initial absorbance of BQ or BQ-AAs mixtures at 246 nm.…”

“…[BQ] = [AAs] = 0.5 mmol/L. All the solutions were diluted 10 times for UV detection [65] ; (c) The pseudo-first-order reaction rate constants k1 (min −1 ) of Cr(VI)reduction by UV/AAs. [AAs] = 0.5 mmol/L; [Cr(VI)] = 0.1 mmol/L; light intensity: 1.25 mW/cm 2 at 254 nm [83] (Reproduced with permission.…”