Orange 2

Photodegradation of AO7 was used as a probe to assess the photoactivity of the TiO₂ layers. Photocatalytic experiments were conducted using an aqueous solution of AO7 (also known as Orange II; Acros Organics, Geel, Belgium) at a concentration of 5.0×10⁻⁵ mol/L, placed in a cylindrical glass reactor equipped with a magnetic stirrer. The glass reactor was irradiated with a polychromatic fluorescent ultraviolet lamp (Philips TDL 8 W; total optical power, 1.3 W), in a configuration providing about 0.35 mW/cm² at the sample surface. The photodegradation kinetics were recorded (in triplicate) by assaying the AO7 solution exposed to different ultraviolet irradiation times using a PerkinElmer Lambda 35 ultraviolet spectrophotometer. Quartz glass cells with an optical pathway of 1 cm were used. Deionized water was taken as the reference. After photodegradation of the dye, we monitored the decrease in absorbance of the solution at 483 nm (strong absorption band of AO7).

Ferric chloride (FeCl₃·6H₂O 99%) and polyEthylene glycol 4000 (PEG-4000) were purchased from Shanghai Chemical Reagents Company (Shanghai, China). Urea (99%) was purchased from Kermel (Tianjin, China) and NaBH₄ (AR) was purchased from Da mao (Tianjin, China). TCNE (98%), Orange II (99.9%, C₁₆H₁₁N₂NaO₄S) and sodium acetate (NaAc 99%) were provided by Acros Organics (New Jersey, USA). Ethylene glycol (EG ≥ 99%) was purchased from Sigma-Aldrich. Coumarin (COU 99%) was purchased from J&K Scientific Ltd. (Beijing China). All chemicals were analytical grade and used as received without further purification.