Tamás Gyulavári

Visible light driven photocatalytic elimination of organic- and microbial pollution by rutile-phase titanium dioxides: new insights on the dynamic relationship between morpho-structural parameters and photocatalytic performance

The characteristic properties and the resulted photocatalytic efficiencies of rutile-phase titanium dioxides were investigated in the present study. A series of rutile with different primary particle sizes (5.2–290 nm) were produced by a sol–gel method followed by calcination and were characterized by XRD, DRS, TEM, XPS, EPR, IR and N2 adsorption. Their photocatalytic efficiencies were determined in the decomposition of phenol, and in the inactivation of E. coli bacteria under visible light irradiation. The results were compared with the photocatalytic performance of commercial Aldrich rutile and Aeroxide P25 powders. Of the non-commercial products, the TiO2 with the smallest particle size displayed the highest efficiency, while the surface-normalized photocatalytic performance was significantly higher for the larger rutile particles. This can be explained by the red shift of light absorption at higher calcination temperatures. Although Aldrich rutile and the corresponding laboratory-made photocatalyst exhibited similar structural features (e.g. particle size, specific surface area, morphology and light absorption), the latter proved to be less efficient despite its Ti3+ content (while Aldrich rutile contains only Ti4+). The main reason for the much higher photocatalytic performance was the presence of Ti–O–O– entities on the surface of Aldrich rutile. On the basis of these results, in the case of rutile-phase titanium dioxide, the presence of Ti–O–O– entities was more beneficial, than the presence of Ti3+ and low-binding-energy oxygen (which indicates defects) in relation with the photocatalytic performance under visible light irradiation.

Influence of synthesis parameters on CCVD growth of vertically aligned carbon nanotubes over aluminum substrate

In the past two decades, important results have been achieved in the field of carbon nanotube (CNT) research, which revealed that carbon nanotubes have extremely good electrical and mechanical properties The range of applications widens more, if CNTs form a forest-like, vertically aligned structure (VACNT) Although, VACNT-conductive substrate structure could be very advantageous for various applications, to produce proper system without barrier films i.e. with good electrical contact is still a challenge. The aim of the current work is to develop a cheap and easy method for growing carbon nanotubes forests on conductive substrate with the CCVD (Catalytic Chemical Vapor Deposition) technique at 640 °C. The applied catalyst contained Fe and Co and was deposited via dip coating onto an aluminum substrate. In order to control the height of CNT forest several parameters were varied during the both catalyst layer fabrication (e.g. ink concentration, ink composition, dipping speed) and the CCVD synthesis (e.g. gas feeds, reaction time). As-prepared CNT forests were investigated with various methods such as scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. With such an easy process it was possible to tune both the height and the quality of carbon nanotube forests.

Novel Applications and Future Perspectives of Nanocomposites

As the present chapter of the book is located in the concluding section, it was important to highlight the main applications of composite materials focusing especially on applications, which exploit other peculiarities of the materials besides photocatalysis. This will be done, by introducing those materials and their composites that are most studied, or were found to exhibit interesting behavior. In many of the presented cases, the main structural, morphological, or optical property of the given composite will be discussed to understand its functioning mechanism, and its role in the current scientific approaches. Additionally, this chapter aims to give a perspective regarding the composite-based nanoscience, and points out important research directions for the further developments of composite materials.