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Photocatalytic performance of titania nanospheres deposited on graphene in coumarin oxidation reaction

Wojtoniszak M., Zielinska B., Kalenczuk R. J., Mijowska E.

Materials Science Poland

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2012

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Vol. 30, No. 1

32--38

EN

In this paper, we present a study on enhanced photocatalytic performance of TiO2 nanospheres deposited on graphene (n-TiO2-G) in a process of coumarin oxidation. The enhancement of the photoactivity has been observed in respect to commercial TiO2 P25. The presented material was prepared in two steps: (i) hydrolysis of titanium (IV) butoxide (TBT) in ethanol solution with simultaneous deposition on graphene oxide (GO) and (ii) calcination of TiO2-GO to form anatase-TiO2 and reduce GO to graphene. The nanomaterial was characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), Fourier-Transformed Infrared spectroscopy and Raman spectroscopy. In the presented photocatalytic process the fluorescence was used to detect-OH formed on a photo-illuminated n-TiO2-G surface using coumarin which readily reacted with -OH to produce highly fluorescent 7-hydroxycoumarin.

2

Single-walled carbon nanotubes fractionation via electrophoresis

Scheibe B., Lukaszczuk P., Rümmeli M. H., Kalenczuk R. J., Borowiak-Palen E.

Polish Journal of Chemical Technology

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2011

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Vol. 13, nr 3

1-4

EN

This work presents the influence of the sonication time on the efficiency of the metallic/semiconducting (M/S) fractionation of diazonium salt functionalized single-walled carbon nanotubes (SWCNTs) via free solution electrophoresis (FSE) method. The SWCNTs synthesized via laser ablation were purified from amorphous carbon and catalyst particles through high vacuum annealing and subsequent refluxing processes in aqua regia solutions, respectively. The purified material was divided into two batches. The SWCNTs samples were dispersed in 1% SDS solution in ultrasound bath for 2 and 12 hours. Both dispersed SWCNTs samples were functionalized with p-aminobenzoic acid diazonium salt and fractionated via free solution electrophoresis method. Afterwards, the fractionated samples were recovered, purified from surfactant/functionalities by annealing and investigated via UV-Vis-NIR optical absorption spectroscopy (OAS). The efficiency of the fractionation process was estimated through the comparison of the van Hove singularities (vHS) presented in the obtained fractions to the starting SWCNTs.

3

Systematic study on synthesis and purification of double-walled carbon nanotubes synthesized via CVD

Jedrzejewska A., Kalenczuk R. J., Mijowska E.

Materials Science Poland

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2011

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Vol. 29, No. 4

292--298

EN

Carbon nanotubes have unique properties, such as thermal and electrical conductance, which could be useful in the fields of aerospace, microelectronics and biotechnology. However, these properties may vary widely depending on the dimensions, uniformity and purity of the nanotube. Nanotube samples typically contain a significant percentage of more allotropes forms of carbon as well as metal particles left over from catalysts used in manufacturing. Purity characterization of double-walled carbon nanotubes (DWCNTs) is an increasingly popular topic in the field of carbon nanotechnology. In this study, DWCNTs were synthesized in a catalytic reaction, using Fe:MgO as catalyst and methane or methane/ethanol as carbon feedstock for chemical vapor deposition (CVD). The addition of ethanol as carbon feedstock allowed to investigate the influence of oxygen on the sample quality. The purification of the as-produced material from the metallic particles and the catalyst support was performed by sonication in an acid solution. The influence of the duration of the acid treatment using ultrasound on the sample purity was investigated, and the optimal value of this parameter was found. Transmission electron microscopy (TEM) images confirmed the removal of impurities and served to elucidate the morphology of the samples. The purity of carbon nanotubes was analyzed using thermal gravimetric analysis (TGA). The Raman spectra of the samples, as a measure of the concentration of defects, were also reported.

4

Synthesis and characterization of iron-filled multi-walled nanotubes

Jedrzejewska A., Costa S., Cendrowski K., Kalenczuk R. J., Mijowska E.

Materials Science Poland

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2011

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Vol. 29, No. 4

299--304

EN

The growth of iron filled multiwalled carbon nanotubes (Fe-MWCNT) using chemical vapour deposition (CVD) has been widely studied. Considering the remarkable magnetic and structural properties of Fe-MWCNT, these materials have been applied in numerous areas. In particular their biomedical application has been explored, where Fe-MWCNT can be used in hyperthermia, acting as a local nano-heater at cellular level. Regarding this aim, the reproducible and highly purified ferromagnetically filled samples of carbon nanotubes are still required. There are several parameters during the synthesis process that influence the properties of the nanotubes. The most favourable temperature of the CNT growth is probably one of the most important issues and its optimisation is crucial. In the current study, the Fe-MWCNT were grown at different temperatures ranging from 650 to 1050 C. Additionally, a comparison between two different CVD systems and two carbon sources are also here presented. The Fe-MWCNT were characterised using diverse techniques regarding the evaluation of their morphology, filling ratio, and purity. Observations showed a strong influence of the growth temperature on the morphology and properties of the Fe-MWCNT. The samples characterisation was performed using Raman spectroscopy, thermogravimetric analysis (TGA), X ray diffraction (XRD), and transmission electron microscopy analysis (TEM).

5

A study on the synthesis, characterization and photocatalytic activity of TiO2 derived nanostructures

Zielińska B., Borowiak-Palen E., Kalenczuk R. J.

Materials Science Poland

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2010

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Vol. 28, No. 3

625--637

EN

Syntheses of TiO2 derived nanostructures have been conducted at 210 °C by hydrothermal reaction of commercial TiO2-P25 (Degussa, Germany) in 10 M NaOH aqueous solution. High purity of the asproduced material was confirmed by scanning and transmission electron microscope analyses. The crystallographic structure, as well as the optical and vibronic properties of this material were examined by X-ray diffraction, diffuse reflectance (DR) UV-Vis, resonance Raman spectroscopic methods, respectively. Detailed analysis of the phase composition revealed that the rod-like structures are made up of sodium tetratitanate (Na2Ti4O9). It was also observed that acid treatment of the material (hydrothermal reaction) led to a decrease in the diameters of the nanorods. Finally, the photocatalytic activity of the investigated nanostructures was examined, by observing the reaction photocatalytic decolourisation of two organic dyes (Reactive Red 198 and Reactive Black 5) under UV-light irradiation.