News

Cooperation

Scientific cooperation

The cooperation with Prof. Bunsho Ohtani and Prof. Ewa Kowalska reaches new levels – Wojciech Macyk spends one month as a visiting professor in Catalysis Research Center, Hokkaido University in Sapporo.

Publication

New publication

Our new paper submitted to Dalton Transactions has been selected by the Editors to be announced at the first cover page. The paper entitled “UV and visible light active aqueous titanium dioxide colloids stabilized by surfactants” (Michał Pacia, Piotr Warszyński, Wojciech Macyk; Dalton Trans. 2014, 43, 12480-12485) describes the synthesis and activity of photosensitized titanium dioxides nanoparticles stabilized by micelles formed in the presence of TWEEN® 80 surfactant. The micelles are stable in water at pH = 7, while their structure and size depend on the surface modification of TiO2. The activity towards reactive oxygen species generation induced by visible light, stability at neutral pH in the form of transparent colloids and simple preparation are very promising features of the developed systems.

Group members

Thesis defended

Elżbieta Świętek has got her PhD degree. Congratulation!

Redox Characteristics of Semiconducting Photocatalytic Materials

The aim of the studies was to develop the method based on spectroelectrochemical measurements, which allows for the characterization of redox properties of various types of semiconducting materials, including determination of the impact of structural modification and surface as well as the influence of the experimental conditions on the redox properties of the semiconductors. As a part of this work a concise description of the methods used for characterization of redox properties of semiconducting photocatalytic materials was carried out and a novel model of photoinduced electron transfer in nanocrystalline semiconductor electrodes was proposed. An important part of the dissertation was the elaboration of the spectroelectrochemical method. The extension of the method is based on the application of the reflectance spectroscopy and analysis of the experimental conditions influence on VON values. The determined potentials correspond to the process of electron trapping on the available energy states close to the edge of the conduction band. The influence of several parameters like oxygen concentration, potential sweep rate, pH and the type of electrolyte, were discussed. The developed spectroelectrochemical method was also used for characterisation of the energy states lying close to the edge of the conduction band. Additional energy states of TiO2.(P25), localized within the bandgap, were qualitatively characterized. The applicability of the method to determine deep and shallow electron traps was confirmed. A quantitative analysis of shallow electron traps was also conducted using a modification of the spectroelectrochemical method by designating the distribution of electron density of states for selected samples. A wide range of applications of the new measurement method was discussed on the basis of measurements carried out for different semiconductors.

Publication

New publication

Our newest paper, entitled “Photocatalytic carboxylation of organic substrates with carbon dioxide at zinc sulfide with deposited ruthenium nanoparticles, has been published in ChemPlusChem(Tomasz Baran, Angela Dibenedetto, Michele Aresta, Krzysztof Kruczała, Wojciech Macyk,ChemPlusChem 2014, 79, 708-715). It describes a photocatalytic synthesis of carboxylic acids using CO2 and acetylacetone as substrates in the presence of ZnS-based photocatalysts with deposited ruthenium(0) nanoparticles. The paper has been published in the Early Career Series, the program of ChemPlusChem journal presenting original papers of young scientists nominated by the Editorial Board. Presented studies have been done in cooperation with the group from Bari.

Group meeting

Group trip

To activate not only small molecules, but also minds and bodies, on April 11-12th we enjoyed a trip to Pieniny mountains. We spent two nice days hiking in this beautiful area. (Everybody reached Trzy Korony.)

Equipment

New equipement!

Our group has got a new equipment for advanced photoelectrochemical measurements. The specially designed set-up enables measurements of photocurrents as a function of the electrode potential and wavelength of incident light. In addition, the Kelvin probe can be used to characterize redox properties of studied semiconductors in the dark and upon irradiation with monochromatic light.

Equipment

SEM purchase

Our group has received a scanning electron microscope TESCAN VEGA3 LMU. The microscope is equipped with LaB6 cathode, SE, BSE and EDX detectors and enables measurements in a low vacuum mode (up to 500 Pa). The analyzed samples can be gold-coated in a high quality desk-top coater.