Rafal J. Wrobel

Evaluation and X-Ray Induced Modification of the Cerium Oxidation State in Cerium Calixarene Complexes

The cerium oxidation state in novel calixarene-supported cerium(IV) β-diketonate complexes [p-tBu-calix[4](OMe)2(O)2]Ce(acac)2 (1) and [p-tBu-calix[4](OMe)2(O)2]Ce(hfac)2 (2), which are a new class of potential precursors for homogeneous oxidative transformations, has been determined using X-ray photoelectron spectroscopy (XPS). Cerium oxidation states between 3.6 and 3.65 were detected, distinctly different from their nominal value of +4. An X-ray induced photoreduction of these compounds was detected. Because of the observed stability of the X-ray modified oxidation state under ambient conditions this effect might be used for a long-standing fine tuning of the Ce oxidation state in cerium calixarenes.

Synthesis and antibacterial properties of Fe3O4-Ag nanostructures

Abstract Superparamagnetic iron oxide nanoparticles were obtained in the polyethylene glycol environment. An effect of precipitation and drying temperatures on the size of the prepared nanoparticles was observed. Superparamagnetic iron oxide Fe3O4, around of 15 nm, was obtained at a precipitation temperature of 80°C and a drying temperature of 60°C. The presence of functional groups characteristic for a polyethylene glycol surfactant on the surface of nanoparticles was confirmed by FTIR and XPS measurements. Silver nanoparticles were introduced by the impregnation. Fe3O4-Ag nanostructure with bactericidal properties against Escherichia coli species was produced. Interesting magnetic properties of these materials may be helpful to separate the bactericidal agent from the solution.

Impact on CO2 Uptake of MWCNT after Acid Treatment Study

Greenhouse effect is responsible for keeping average temperature of Earth’s atmosphere at level of about 288u2009K. Its intensification leads to warming of our planet and may contribute to adverse changes in the environment. The most important pollution intensifying greenhouse effect is anthropogenic carbon dioxide. This particular gas absorbs secondary infrared radiation, which in the end leads to an increase of average temperature of Earth’s atmosphere. Main source of CO2 is burning of fossil fuels, like oil, natural gas, and coal. Therefore, to reduce its emission, a special CO2 capture and storage technology is required. Carbonaceous materials are promising materials for CO2 sorbents. Thus multiwalled carbon nanotubes, due to the lack of impurities like ash in activated carbons, were chosen as a model material for investigation of acid treatment impact on CO2 uptake. Remarkable 43% enhancement of CO2 sorption capacity was achieved at 273u2009K and relative pressure of 0.95. Samples were also thoroughly characterized in terms of texture (specific surface area measurement, transmission electron microscope) and chemical composition (X-ray photoelectron spectroscopy).

Improving the Carbon Dioxide Uptake Efficiency of activated Carbons Using a Secondary Activation With Potassium Hydroxide

Abstract Secondary activation of commercial activated carbon (AC) ORGANOSORB 10-CO was carried out at 600, 700 and 800oC with mass ratios of potassium to AC (K/AC) in range 1-3. Crucial samples have shown following CO2 uptakes and SSA - 3.90 mmol/g and 1225 m2/g, 4.54 mmol/g and 1546 m2/g, 4.28 and 1717 m2/g for pristine material and samples obtained at 700oC with K/AC = 2 and at 800oC with K/AC = 3 respectively. Last sample also indicated signifi cant mesopore volume increase in diameter range 2-5 nm, from 0.11 to 0.24 cm3/g. CO2 uptake increase was explained by formation of micropores up to diameter of 0.8 nm, which distribution was established from CO2 sorption using DFT. Surface chemistry of all samples has not changed during modifi cation, what was proven by XPS. Moreover, deeper incorporation of potassium ions into graphite at higher temperatures was observed as confi rmed with EDS, XPS and XRD.