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TiO 2 hollow structures (HS) were synthesized by carbon sphere template removal method. Nanometer sized carbon spheres (CS) were prepared by mild hydrothermal treatment of ordinary table sugar (sucrose). The size of these spheres can be controlled by the parameters of the hydrothermal treatment (e.g. time and pH). The obtained CSs were characterized by scanning electron microscopy (SEM), Raman spectroscopy, infrared spectroscopy (IR), X-ray diffraction (XRD) and thermogravimetry (TG). CSs were successfully coated with TiO 2 via sol-gel method. The phase composition of the TiO 2 hollow spheres were controlled by the annealing temperature during crystallization and CSs template removal. TiO 2 hollow structures (HSs) were characterized by SEM, XRD, Raman spectroscopy, TG and energy-dispersive X-ray spectroscopy (EDX). Photocatalytic performance of the TiO 2 HSs was evaluated by phenol degradation in a batch-type foam reactor under low powered UV-A irradiation. The degradation reaction was followed by high-performance liquid chromatography (HPLC) and total organic carbon (TOC) measurement techniques. Photocatalytic activity test results pointed out that increased rutile content up to a certain extent (resulting mixed phase anatase-rutile TiO 2) effects advantageously the photocatalytic performance of TiO 2 HSs and the unique morphology proved to enhance the photocatalytic activity (six times) as well as TOC removal efficiency (twelve times) compared to the sample which was prepared by the same method without the CSs.

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Carbon nanospheres (CNSs) were prepared by hydrothermal synthesis, and coated with TiO2 and ZnO nanofilms by atomic layer deposition. Subsequently, through burning out the carbon core templates hollow metal oxide nanospheres were obtained. The substrates, the carbon-metal oxide composites and the hollow nanospheres were characterized with TG/DTA-MS, FTIR, Raman, XRD, SEM-EDX, TEM-SAED and their photocatalytic activity was also investigated. The results indicate that CNSs are not beneficial for photocatalysis, but the crystalline hollow metal oxide nanospheres have considerable photocatalytic activity.

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Titanium dioxide–carbon sphere (TiO2–CS) composites were constructed via using prefabricated carbon spheres as templates. By the removal of template from the TiO2–CS, TiO2 hollow structures (HS) were synthesized. The CS templates were prepared by the hydrothermal treatment of ordinary table sugar (sucrose). TiO2–HSs were obtained by removing CSs with calcination. Our own sensitized TiO2 was used for coating the CSs. The structure of the CSs, TiO2–CS composites, and TiO2–HSs were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). The effect of various synthesis parameters (purification method of CSs, precursor quantity, and applied furnace) on the morphology was investigated. The photocatalytic activity was investigated by phenol model pollutant degradation under visible light irradiation (λ > 400 nm). It was established that the composite samples possess lower crystallinity and photocatalytic activity compared to TiO2 hollow structures. Based on XPS measurements, the carbon content on the surface of the TiO2–HS exerts an adverse effect on the photocatalytic performance. The synthesis parameters were optimized and the TiO2–HS specimen having the best absolute and surface normalized photocatalytic efficiency was identified. The superior properties were explained in terms of its unique morphology and surface properties. The stability of this TiO2–HS was investigated via XRD and SEM measurements after three consecutive phenol degradation tests, and it was found to be highly stable as it entirely retained its crystal phase composition, morphology and photocatalytic activity.

In the present publication, multiwalled carbon nanotubes (MWCNT) coated with SiO2–MgO nanoparticles were successfully fabricated via sol–gel method to facilitate their incorporation into polymer matrices. Magnesium acetate tetrahydrate and tetraethyl orthosilicate were used as precursors. The coated MWCNTs were characterized by transmission electron microscopy (TEM), X–ray diffraction (XRD) and Raman spectroscopy methods. These investigation techniques verified the presence of the inorganic nanoparticles on the surface of MWCNTs. Surface coated MWCNTs were incorporated into polyamide (PA), polyethylene (PE) and polypropylene (PP) matrices via melt blending. Tensile test and differential scanning calorimetry (DSC) investigations were performed on SiO2–MgO/MWCNT polymer composites to study the reinforcement effect on the mechanical and thermal properties of the products. The obtained results indicate that depending on the type of polymer, the nanoparticles differently influenced the Young’s modulus of polymers. Generally, the results demonstrated that polymers treated with SiO2-MgO/MWCNT nanoparticles have higher modulus than neat polymers. DSC results showed that nanoparticles do not change the melting and crystallization behavior of PP significantly. According to the obtained results, coated MWCNTs are promising fillers to enhance mechanical properties of polymers.