Characterization of TiO2-coated carbon nanotube photocatalysts.

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Photocatalytic activity of TiO2/SWCNT and TiO2/MWCNT nanocomposites with different carbon nanotube content

With different mass ratios, titanium dioxide/carbon nanotube (0.1-10 wt% CNTcontent) nanocomposites were prepared with the aid of ultrasonication method. The structures of the various TiO2/CNT nanocomposites were characterized by electron microscopy (scanning electron microscopy, transmission electron microscopy). Their photocatalytic activity was tested by the degradation of phenol in aqueous solution under near-UV irradiation. In parallel experiments, both (SW and MW) CNT samples were treated in a reflux system with nitric acid to functionalize the nanotubes, subsequently preparing the nanocomposites in the same method. At higher CNT concentration (5, 10 wt%) the nanocomposites exhibited lower photocatalytic activity compared to the samples with lower CNT concentration, probably because the higher CNT concentration reduces the light intensity on the surfaces of TiO2 particles. Our aim was to find the best synthesis method and the optimal composition of the TiO2/CNT nanocomposites for the degradation of phenol under UV irradiation. The highest degradation rate was achieved with Aldrich anatase/functionalized single wall carbon nanotube nanocomposite (AA+f-SW1 wt%). The photocatalytic activity of this sample was significantly higher compared to the bare Aldrich anatase and Aeroxide P25 titanium dioxide reference samples which were the best photocatalysts among the investigated bare titanias. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Influence of TiO2 phase composition on the photocatalytic activity of TiO2/MWCNT composites prepared by combined sol-gel/hydrothermal method

Titanium dioxide/multiwall carbon nanotube (TiO2/MWCNT) composites were prepared by sol-gel method with hydrolysis of titanium alkoxide precursor followed by crystallization via hydrothermal treatment at different acid concentrations. Transmission electron microscopy (TEM) measurements revealed that the acid concentration has serious control over the morphology which is in good agreement with the change of specific surface area. According to the X-ray diffraction analysis of the samples the anatase/rutile ratio of the TiO2 in the composite can be tuned by the manipulation of acid concentration used for the hydrothermal crystallization. Samples were tested in aqueous-phase photocatalytic degradation reaction of salicylic acid in a batch-type foam reactor using relatively low power UV-A irradiation. The change in salicylic acid concentration was monitored by UV-vis spectroscopy technique. Anatase/rutile ratio decreased with increasing acid concentration and photocatalytic performance was decreased with increasing rutile content, however low rutile content (11 wt%) enhanced the photocatalytic efficiency above all prepared samples. (C) 2016 Elsevier B.V. All rights reserved

Long term stabilization of reaction center protein photochemistry by carbon nanotubes

The long term stability and the redox interaction between single walled carbon nanotubes (SWNTs) and photosynthetic reaction center proteins (RCs) purified from purple bacterium Rhodobacter sphaeroides R-26 in the SWNT/RC complex has been investigated. The binding of SWNT to RC results in an accumulation of positive (the oxidized primary electron donor, P+) and negative (semiquinone forms, Q(A)(-) and Q(B)(-), the reduced primary and secondary quinones, respectively) charges followed by slow reorganization of the protein structure after excitation. The photochemical activity of the SWNT/RC complexes remains stable for several weeks even in dried form. In the absence of SWNT the secondary quinone activity decays quickly as a function of time after drying the RC onto a glass surface. Polarography measurements substantiate the idea that there is an electronic interaction between the RCs and SWNTs after light excitation, which was suggested earlier by optical measurements. The special electronic properties of the SWNT/protein complexes open the possibility for several applications, e. g., in microelectronics, analytics, or energy conversion and storage. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei