تهيه‌ي درجاي نانوذره‌هاي تيتانيوم دي‌اكسيد رنگي‌شده با پيگمنت كوئين آكريدون و بررسي فعاليت فوتوكاتاليتيكي آن‌ها براي واكنش اكسايش سيترال تحت تابش نور مرئي با استفاده از گونه‌هاي فعال اكسيژن

The use of light to selec‎tively promote chemical reactions is an important approach in photochemical an‎d photocatalytic processes. In this study, a TiO2–quinacridone (QA) system was prepared to extend the photoresponse of TiO2 into the visible-light region, an‎d the effect of calcination temperature on its properties was investigated. TiCl4 was hydrolyzed in the presence of QA, an‎d the resulting material was dried an‎d subsequently calcined at 200, 300, an‎d 400 °C. The samples were characterized by X-ray diffraction (XRD), ATR-FTIR spectroscopy, diffuse reflectance spectroscopy, an‎d thermogravimetric analysis (TGA). The photocatalytic performance of TiO2–QA-200 in the oxidation of citral under visible-light irradiation was also eva‎luated by GC–MS. XRD analysis showed that anatase was the predominant TiO2 phase in the prepared samples, whereas rutile was also detected in the sample calcined at 400 °C. Increasing the calcination temperature resulted in crystallite growth an‎d a gradual decrease in the spectral features associated with QA. The ban‎d-gap energies of TiO2–QA-200 an‎d TiO2–QA-300 were approximately 2.37 an‎d 2.42 eV, respectively, while that of TiO2–QA-400 increased to approximately 2.92 eV. These results indicate that samples calcined at lower temperatures retained a greater degree of visible-light absorption. The potassium iodide–starch test further showed that TiO2–QA-200 induced iodide oxidation after 20 min of irradiation, indicating the generation of reactive oxygen species. During the photocatalytic oxidation of citral, the relative abundances of neral an‎d geranial gradually decreased with increasing irradiation time, accompanied by the formation of new oxygenated products. Geraniol was detected as a minor product at the early stages of the reaction, while 6,7-epoxyneral an‎d 6,7-epoxygeranial were identified after 360 min of irradiation. Species corresponding to geranic/neric acid were also observed, together with additional products at longer irradiation times, suggesting the occurrence of parallel an‎d/or consecutive reaction pathways. After 960 min of irradiation, the combined relative chromatographic abundance of neral an‎d geranial decreased from 95.84% at 30 min to 53.95%. Overall, the results demonstrate that calcination temperature significantly affects the crystalline structure, retention of the organic component, visible-light absorption, an‎d photocatalytic behavior of the TiO2–QA system.

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غلامحسين محمدنژاد شيرازي , معصومه جديدي نژاد