Effect of porphyrin on photocatalytic activity of TiO 2 nanoparticles toward Rhodamine B photodegradation

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2017-11, Vol.176, p.25-35
• Main Authors: Ahmed, M A, Abou-Gamra, Z M, Medien, H A A, Hamza, M A
• Format: Article
• Language: English
• Subjects: Catalysis; Free Radical Scavengers - chemistry; Hydrogen-Ion Concentration; Metal Nanoparticles - chemistry; Microscopy, Electron, Transmission; Oxygen - chemistry; Photolysis - radiation effects; Porphyrins - chemistry; Quantum Theory; Rhodamines - chemistry; Spectrophotometry, Ultraviolet; Titanium - chemistry; Ultraviolet Rays; Water Pollutants, Chemical - chemistry
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2017.09.016

As known, porphyrins have central role in photosynthesis, biological oxidation and reduction and oxygen transport beside to their intensive color which qualify them to be good photosensitizers. Herein, tetra (4-carboxyphenyl) porphyrin (TCPP) was prepared by a simple one-pot synthesis to use as a visible antenna for TiO nanoparticles that were prepared via a simple template-free sol-gel method. Various loading percentages of TCPP (0.05-1%) were incorporated on the surface of TiO as photosensitizer for photocatalytic degradation of Rhodamine B (Rh B) dye as a primary cationic pollutant model. Among them, 0.1% TCPP-TiO was the most reactive sample. It was found that the photoactivity of 0.1% TCPP-TiO sample (0.5g/L) was approximately 1.5 times greater than that of pure TiO (0.5g/L) toward the degradation of Rh B (1×10 M) under UV-A irradiation. Transient fluorescence decay measurements showed that the life time of TiO excited state has doubled after anchoring TCPP, thus the probability of electron-hole recombination has decreased. The samples were characterized by XRD, HR-TEM, DRS and N adsorption-desorption isotherms. The XRD patterns confirmed the successful preparation of TiO nanoparticles with average crystalline size of 25.7nm. Also, XRD patterns suggested the presence of mixed phase TiO nanoparticles of 77% anatase and 23% rutile. DRS showed that the characteristic peaks of TCPP covered the whole visible range 400-700nm. HR-TEM images showed the spheroids shape of TiO nanoparticles and confirmed the presence of anatase and rutile phases as suggested from XRD data. The different parameters affecting the photodegradation of Rh B dye such as catalyst dose, dye concentration and pH were studied to obtain the optimum conditions. Almost complete degradation of Rh B was obtained which confirmed by HPLC and TOC measurements. The effect of scavengers was studied to indicate the most active species. TCPP-TiO gave a good response toward the photodegradation of Rh B under visible irradiation. Finally, the mechanism of photocatalytic degradation process was suggested.