19 research outputs found
Interplay between Fe-Titanate Nanotube Fragmentation and Catalytic Decomposition of C2H4: Formation of C/TiO2 Hybrid Interfaces
This paper reports the synthesis of Fe-titanate nanotubes by means of the conventional ion-exchange method with iron nitrate solutions. As the iron-rich nanotubes were found to contain the catalyst precursor intrinsically dispersed in their structures, the unprecedented possibility of using this kind of materials for building carbon nanostructures, firmly attached at the surface of the forming TiO2 nanoparticles, was verified. The catalytic decomposition of ethylene, used as a carbon source, was performed at a relatively high temperature (750 °C) when the nanotubes undergo an irreversible phase transformation to form anatase and rutile nanoparticles. Due to the different amounts of Fe ions in the nanotubes, distinct types of carbon/TiO2 hybrid interfaces were formed, ranging from amorphous (lower Fe3+ concentration) to the more crystalline graphitic domains (higher Fe3+ concentrations), as documented by the microstructure of the treated samples. The present approach is of potential interest for (photo)catalytic and energy conversion/transport applications
Sulfur-doped TiO2: Structure and surface properties
A comprehensive study on the sulfur doping of TiO2, by means of H2S treatment at 673 K, has been performed in order to highlight the role of sulfur in affecting the properties of the system, as compared to the native TiO2. The focus of this study is to find a relationship among the surface, structure, and morphology properties, by means of a detailed chemical and physical characterization of the samples. In particular, transmission electron microscopy images provide a simple tool to have a direct and immediate evidence of the effects of H2S action on the TiO2 particles structure and surface defects. Furthermore, from spectroscopy analyses, the peculiar surface, optical properties, and methylene blue photodegradation test of S-doped TiO2 samples, as compared to pure TiO2, have been investigated and explained by the effects caused by the exchange of S species with O species and by the surface defects induced by the strong H2S treatment
Relationship between morphology and electrical properties in PP/MWCNT composites: Processing-induced anisotropic percolation threshold
Few-Layer MoS₂ Nanodomains Decorating TiO₂ Nanoparticles: A Case Study for the Photodegradation of Carbamazepine
S-doped TiO2 and hybrid MoS2/TiO2 systems have been synthesized, via the sulfidation with H2S of the bare TiO2 and of MoOx supported on TiO2 systems, with the aim of enhancing the photocatalytic properties of TiO2 for the degradation of carbamazepine, an anticonvulsant drug, whose residues and metabolites are usually inefficiently removed in wastewater treatment plants. The focus of this study is to find a relationship between the morphology/structure/surface properties and photoactivity. The full characterization of samples reveals the strong effects of the H2S action on the properties of TiO2, with the formation of defects at the surface, as shown by transmission electron microscopy (TEM) and infrared spectroscopy (IR), while also the optical properties are strongly affected by the sulfidation treatment, with changes in the electronic states of TiO2. Meanwhile, the formation of small and thin few-layer MoS2 domains, decorating the TiO2 surface, is evidenced by both high-resolution transmission electron microscopy (HRTEM) and UV-Vis/Raman spectroscopies, while Fourier-transform infrared (FTIR) spectra give insights into the nature of Ti and Mo surface sites. The most interesting findings of our research are the enhanced photoactivity of the MoS2/TiO2 hybrid photocatalyst toward the carbamazepine mineralization. Surprisingly, the formation of hazardous compounds (i.e., acridine derivatives), usually obtained from carbamazepine, is precluded when treated with MoS2/TiO2 systems
Graphite nanoplatelets and carbon nanotubes based polyethylene composites: Electrical conductivity and morphology
From Polymer to Magnetic Porous Carbon Spheres: Combined Microscopy, Spectroscopy, and Porosity Studies
The facile preparation of polymer waste-derived microporous carbon microspheres (SBET ~800 m2/g) 100–300 μm in size, is reported at first. We have taken advantage of both, the crosslinked nature and the porous texture of the poly(4-ethylstyrene-co-divinylbenzene) microspheres, which allow the incoming anions and cations present in liquid media to enter and to remain segregated into the pores of the polymer microspheres as soon as the solvent is removed. Interestingly, the ZnCl2 phase, when incorporated in the microporous molecular architecture of the polymer, prevents the collapsing of the pore structure of thermosetting polymer spheres during the pyrolysis occurring at 800°C and acts as an activating agent of the carbon phase under formation, being responsible for the formation of an extended meso- and macroporosity (30–200 and 300–1,000 Å ranges). More interestingly, porous carbon microspheres with magnetic properties have been prepared from the ZnCl2-activated porous carbon spheres after impregnation with Fe nitrate solution and thermal treatment at 800°C. A multi-technique methodology to characterize more extensively carbons at the micro/nanoscale is reported in the paper. More in detail, the morphology, structure, porous texture, and the surface properties of the carbon and of the magnetic carbon microspheres have been investigated by scanning and transmission electron microscopy, atomic force microscopy, X-ray diffraction, N2 physisorption, diffuse reflectance UV-Vis, Raman and infrared spectroscopies. Furthermore, magnetic properties have been revealed at the nano- and at the macroscale by magnetic force microscopy and simple magnetically guided experiments by permanent magnets. The multi-technique methodology presented in the paper allows in elucidating more extensively about the different characteristics of activated carbons. Notwithstanding the huge amount of literature on activated carbons, the precise control of both the structure and the surface has, for the most part, hidden the relevance of other properties at the molecular scale of the assembled architectures. On the other hand, recent studies indicate that by molecular design, nanostructured, and porous carbonaceous materials could also be rationally proposed
Postactivation potentiation effects on squat performance and muscle synergies in resistance trained men
Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties
Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25) system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method). Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications