Agata Zdyb

Characterization of adsorption and electronic excited states of quercetin on titanium dioxide nanoparticles.

Adsorption of quercetin on colloidal titanium dioxide nanoparticles in ethanol and its excited-state electronic structure were investigated by means of electronic and vibrational spectroscopies. The changes in electronic charge redistribution as reflected by the dipole moment difference, ∆μ, between the ground and excited electronic states were measured with electroabsorption spectroscopy and analyzed using results of TD DFT computations. Adsorption of quercetin causes a red shift of its absorption spectrum. Raman spectra of quercetin analyzed with reference to analogous data for morin indicate binding of quercetin through the hydroxy groups of the catechol moiety. The difference dipole moment, which is 5.5D in free quercetin, increases to 11.8D in opposite direction in adsorbed quercetin, and is associated with charge-transfer to the Ti atom. The computed transition energy, intensity, vector Δμ and molecular orbitals involved in the electronic transition at different molecular configurations indicate a bidentate chelating mode of binding of quercetin.

Reduction of Pollution Emission by Using Solar Energy in Eastern Poland

The present work is devoted to the analysis of electric energy production in photovoltaic power plant located in eastern part of Poland and to the estimation of pollution avoided due to the use of solar radiation energy. Photovoltaic power plant consists mainly of silicon polycrystalline modules but in its experimental part thin film modules of three different technologies are also installed giving the total power of 1.4 MWp. In 2015 the PV plant produced above 1.5 MWh of electric energy. Benefits of renewable energy use result in a significant reduction of emissions that are harmful to people and other living species too.

Charge-transfer excited state in pyrene-1-carboxylic acids adsorbed on titanium dioxide nanoparticles

The electronic structure of excited photosensitizer adsorbed at the surface of a solid is the key factor in the electron transfer processes that underlie the efficiency of dye-sensitized solar cells and photocatalysts. In this work, Stark effect (electroabsorption) spectroscopy has been used to measure the polarizability and dipole moment changes in electronic transitions of pyrene-1-carboxylic (PCA), -acetic (PAA) and -butyric (PBA) acids in ethanol, both free and adsorbed on colloidal TiO2, in glassy ethanol at low temperature. The lack of appreciable increase of dipole moment in the excited state of free and adsorbed PAA and PBA points that two or more single bonds completely prevent the expansion of π-electrons from the aromatic ring towards the carboxylic group, thus excluding the possibility of direct electron injection into TiO2. In free PCA, the pyrenes forbidden S0→S1 transition has increased intensity, exhibits a long progression in 1400cm-1 Ag mode and is associated with |∆μ| of 2 D. Adsorption of PCA on TiO2 causes a broadening and red shift of the S0→S1 absorption band and an increase in dipole moment change on electronic excitation to |∆μ|=6.5 D. This value increased further to about 15 D when the content of acetic acid in the colloid was changed from 0.2% to 2%, and this effect is ascribed to the surface electric field. The large increase of |∆μ| points that the electric field effect can not only change the energetics of electron transfer from the excited sensitizer into the solid, but can also shift the molecular electronic density, thus directly influencing the electronic coupling factor relevant for electron transfer at the molecule-solid interface.