Rafał Wróbel

Antibacterial properties of TiO2 modified with reduced graphene oxide

In this paper, the antibacterial activity of titanium dioxide modified with reduced graphene oxide (rGO) was presented. TiO2/rGO photocatalysts were prepared by the hydrothermal method under elevated pressure at 180°C and heated at 100°C in Ar flow. The obtained photocatalysts were characterized by means of XRD, FTIR/DRS, UV-vis/DR, Raman spectroscopy and scanning electron microscopy (SEM). The carbon content was also examined. FTIR/DRS and Raman analysis confirmed the presence of rGO in the TiO2 structure, suggesting a successful modification. The antimicrobial photoactivity of photocatalysts was conducted against E. coli under an artificial solar light. The results show that all TiO2/rGO photocatalysts exhibited an antibacterial activity higher than unmodified TiO2. The best result was found for sample with 1.5wt% additive of reduced graphene oxide. In this case, total inactivation of E. coli was noticed after 75min of irradiation. It was found that the presence of rGO in sample improves the antimicrobial activity.

Titanium dioxide modified with various amines used as sorbents of carbon dioxide

In this study, titanium dioxide was modified with various amines through hydrothermal treatment for adsorption of CO2. The carbon dioxide adsorption performance of the prepared samples was measured using an STA 449 C thermobalance (Netzsch Company, Germany). The morphological structures, functional groups and elemental compositions of the unmodified and amine-modified titanium dioxide sorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR/DR) and scanning electron microscopy (SEM), respectively. The results showed that modification of TiO2 with amines through hydrothermal treatment is a simple method to prepare CO2 sorbents with high adsorption capacities. Moreover, the results revealed that TEPA-modified titanium dioxide shoved the highest adsorption capacity, enabling an increase in CO2 uptake from 0.45 mmol CO2 g−1 in the case of raw TiO2 to 1.63 mmol CO2 g−1. This result could be indirectly related to the fact that TEPA has the highest amino group content among the three amines used in our research. Additionally, durability tests performed by cyclic adsorption–desorption revealed that TEPA modified titanium dioxide also possesses excellent stability, despite a slight decrease in adsorption capacity over time.

TiO2 Supported on Quartz Wool for Photocatalytic Oxidation of Hydrogen Sulphide

A spacial system consisting of TiO2 on a fibrous support was prepared by hydrolysis of titanium isopropoxide in the presence of quartz wool, followed by calcination. The material was characterized by X-ray diffraction, nitrogen adsorption–desorption at 77 K, X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The TiO2/support system was examined as a photocatalyst for UV-assisted oxidation of H2S in air. The results obtained confirmed a superior performance of the TiO2/support system over TiO2 powder. H2S underwent oxidation to elemental sulphur and/or S6+. The relative amounts of these species were influenced by humidity.

Adsorption of carbon dioxide on TEPA-modified TiO2/titanate composite nanorods

A titanate–TiO2 composite was obtained through hydrothermal treatment of TiO2 in KOH solution. The presence of a titanate phase was confirmed by X-ray diffraction (XRD), whereas scanning electron microscopy (SEM) measurements showed the porous nanorod structure of the material. The obtained nanorods were treated with tetraethylenepentamine (TEPA). Such synthesized sorbents were applied for CO2 removal. The CO2 capacity under a pressure of 1 bar and at 80 °C was 0.47, 0.34, and 3.11 mmol g−1 for the starting TiO2, the titanate–TiO2 composite and the TEPA–titanate–TiO2 composite (27.4 wt% of TEPA), respectively. The experimental isotherms of CO2 were analysed using the Langmuir, Freundlich, Sips, Toth, Unilan, Redlich–Peterson, Radke–Prausnitz, Dubinin–Radushkevich, Temkin and Pyzhev, and Jovanovich models. The error sums of squares (SSR) function was used to test the fit of the models. The analysis revealed that the Sips isotherm is the best-fitting model for the CO2 adsorption on the starting TiO2, whereas the Freundlich equation should be used to describe the CO2 adsorption isotherm on the titanate–TiO2 composite. The CO2 adsorption on the TEPA-modified sorbents was proposed to be described using the Sips isotherm for physical sorption and the modified Sips model for chemical sorption. The calculated isosteric heat of adsorption was found to be ≈46 kJ mol−1, which is about two times higher than the heat of CO2 absorption in liquid TEPA reported in the literature (i.e. ≈85 kJ mol−1). Therefore, it was concluded that the TEPA–titanate–TiO2 composite is an attractive alternative for liquid amines due to the lower energy of regeneration in the sorption–desorption process. The material was proved to be stable during multiple sorption–desorption cycles. Moreover, its thermal stability up to 150 °C was confirmed by thermogravimetric analysis (TGA). All these features make it a promising alternative for sorbents based on liquid amines.

Increase the Microporosity and CO2 Adsorption of a Commercial Activated Carbon

Microporous carbons prepared from commercial activated carbon WG12 by KOH and/or ZnCl2 treatment were examined as adsorbents for CO2 capture. The micropore volume and specific surface area of the resulting carbons varied from 0.52 cm3/g (1374 m2/g) to 0.70 cm3/g (1800 m2/g), respectively. The obtained microporous carbon materials showed high CO2 adsorption capacities at 40 bar pressure reaching 16.4 mmol/g.

Preparation and characterization of titania powders obtained via hydrolysis of titanium tetraisopropoxide

TiO2 powders were prepared through the hydrolysis of titanium isopropoxide followed by calcination at temperatures of 200 °C to 600 °C. The obtained powders were characterized by N2 adsorption-desorption and X-ray powder diffraction. The results confirmed strong dependence between specific surface area of the TiO2 powders and both the conditions of the hydrolysis process and the calcination temperature. While calcination temperature strongly affected crystallinity of the product, no significant influence of the hydrolysis conditions on this parameter was observed. TiO2 powders prepared at various conditions were examined as catalysts for photodegradation of Acid Red 18 in water. Photoactivities of the prepared powders were influenced by both the amount of water used to hydrolyze the TiO2 precursor and the temperature of calcination process. TiO2 samples calcined at 500 °C appeared to be the most active and the photocatalytic activities of the prepared materials increased along with the amount of water used for the hydrolysis process.

Thermal stability of nanocrystalline iron

Nanocrystalline iron was obtained by reduction of magnetite doped with structural promoters at 773 K and characterized by various methods i.e. thermal desorption of gases (BET), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Crystallite size distribution was determined using a novel method based on a phenomenon unique to nanomaterials, i.e. the dependence of the crystallite phase transition on the size of the crystallites. Thermal treatment of the nanocrystalline iron in a hydrogen atmosphere at 1073 K revealed that it is thermally unstable. The parameters of the log-normal crystallite size distribution were d0 = 15.3 nm, σ = 0.35 and d0 = 23.5 nm, σ = 0.17 for iron treated at 773 K and 1073 K, respectively. The corresponding average crystallite sizes determined from the Scherrer formula were 18 nm and 24 nm, respectively. The size distribution of the sintered materials clearly shows that the thermal stability is a function of the size of the crystallites, i.e. the smallest crystals are the least thermally stable. However, no increase in the contribution of crystallites above 35 nm has been observed. Application of this phenomenon combined with the determination of crystallite size distribution enables fine-tuning of the crystallite size distribution.

Electrically conductive acrylic pressure-sensitive adhesives containing carbon black

Electrically conductive acrylic pressure-sensitive adhesives containing carbon black Acrylic pressure-sensitive adhesives (PSA) are non electrical conductive materials. The electrical conductivity is incorporated into acrylic self-adhesive polymer after adding electrically conductive additives like carbon black, especially nano carbon black. After an addition of electrical conductive carbon black, the main and typical properties of pressure-sensitive adhesives such as tack, peel adhesion and shear strength, are deteriorated. The investigations reveals that the acrylic pressure-sensitive adhesives basis must be synthesised with ameliorated initial performances, like high tack, excellent adhesion and very good cohesion. Currently, the electrical conductive solvent-borne acrylic PSA containing carbon black are not commercially available on the market. They are promising materials which can be applied for the manufacturing of diverse technical high performance self-adhesive products, such as broadest line of special electrically conductive sensitive tapes.

Surface characteristics of KOH-treated commercial carbons applied for CO2 adsorption:

The effect of an alkali treatment (potassium hydroxide) on the properties of a commercial activated carbon has been studied. The aim of the treatment was to improve the adsorption properties of the material toward carbon dioxide. In the result of the treatment, silica contained in the raw carbon was removed and the density of the material increased. The changes in the surface chemistry were observed as well. The treatment of the activated carbon with KOH resulted in a complete removal of carboxy and lactone groups and a decrease of the general content of the acidic groups (more significant than that of basic groups). Simultaneously, the surface concentration of hydroxyl groups increased. The alkali treatment of activated carbon resulted in an increase of carbon dioxide uptake of 14% (measured using a volumetric method at 0℃). The adsorption of carbon dioxide on activated carbon has a mixed (physicochemical) character and that two types of adsorption sites are present at the surface. The adsorption energy varies roughly from 25 to 60 kJ/mol.

Supramolecular synthons and pattern recognition in adenine amides - synthesis, structures and thermal properties

An effective method for the synthesis of novel adenine amides was developed and successfully implemented, leading to 4-propyloxy-N-(9H-purin-6-yl)benzamide (1) and 4-dodecyloxy-N-(9H-purin-6-yl)benzamide (2). The compounds were fully characterised by means of spectroscopic (1H NMR, 13C NMR, FT-IR) and thermal (TG, DSC) analysis. The crystallographic analysis revealed that the formation of supramolecular chains relies on hydrogen bonding between amide functionalities. All supramolecular synthons found in the crystal structure of 1 were confirmed with the temperature-dependent IR method. The temperature-dependent IR method is useful in determining supramolecular interactions for compound 2, for which the crystal structure could not be obtained. A detailed analysis of temperature-dependent FT-IR spectra was used for the first time to identify the hydrogen bonds that exist in the solid state of our compounds; it can therefore be considered a promising method for the pattern recognition of hydrogen bonding in supramolecular chemistry.