Synthesis, characterization and photocatalytic applications of novel phthalocyanine-TiO2 nanocomposites

TiO2 is photocatalyst widely used in the photocatalytic degradation of organic pollutants. However, TiO2 does not exhibit photocatalytic activity for decomposition of organic compounds in the visible region, due to the large band gap of TiO2. For this reason, recent studies have focused on the sensitization of TiO2 surface. By sensitizing the surface of TiO2, its properties can be influenced in two different ways so that it demonstrates photocatalytic activity in the visible region. First of these can be done by preventing the recombination of band gap energy, and the second by shifting the used wavelength range to the visible region. Phthalocyanines are interesting sensitizers because they exhibit visible absorption bands around 650-700 nm, have high chemical and thermal stability, and also exhibit catalytic properties. The production of photocatalysts, which can be sensitized by longer wavelengths, through preparation of Pc-TiO2 nanocomposites by loading phthalocyanine compounds (Pc) on TiO2 has recently attracted attention. In this thesis, the photocatalytic degradation of Methylene Blue (MB) organic dye material under visible light using phthalocyanine (Pc)-TiO2 nanocomposites was investigated. The thesis consists of three parts. In the first part of the thesis, a compound, which was a phthalonitrile derivative, was synthesized using 2-hydroxymethyl-1,4-benzodioxane and 4-nitrophthalonitrile compounds, and using this compound, peripheral tetra-substituted metal-free (1), Zinc(II) (2), Cobalt(II) (3), Nickel(II) (4), and Copper(II) (5) phthalocyanine compounds were synthesized. At the same time, compound b, which was a phthalonitrile derivative, was synthesized using 2-hydroxymethyl-1,4-benzodioxane and 3-nitrophthalonitrile compounds, and using this compound, non-peripheral tetra-substituted metal-free (6), Zinc(II) (7), Cobalt(II) (8), Nickel(II) (9), and Copper(II) (10) phthalocyanine compounds were synthesized. The structures of the synthesized compounds were characterized using elemental analysis, FT-IR, UV-vis, 1H-NMR, 13C-NMR, GC-MS, and MALDI-TOF MS techniques. In the second part of the thesis, nanocomposites of all synthesized phthalocyanine compounds were formed with TiO2. A total of 10 different Pc-TiO2 nanocomposites were successfully obtained by the hydrothermal method, which is a highly effective method for TiO2 synthesis at the nanoscale, using the corresponding phthalocyanine derivatives and titanium(IV) isopropoxide. The structures and properties of all synthesized nanocomposites were investigated using XRD, FT-IR, FEG-SEM, EDX, UV-DRS, BET, and zeta sizer techniques. In the third and final part of the thesis, all synthesized Pc-TiO2 nanocomposites were tested for their photocatalytic activity to be used as photocatalysts. For this purpose, photocatalytic activities of all Pc-TiO2 nanocomposites were investigated via the degradation of MB stain, which is a model contaminant under visible light. Based on the conducted studies, it was observed that the phthalocyanine-free TiO2 photocatalyst showed no activity in the degradation of MB under visible region rays, while the Pc-TiO2 photocatalysts performed very well in the degradation of MB, resulting in complete degradation of MB in 100-140 minutes.