Nanocomposites and nanomaterials

Photochemical interactions between the polymethine dye consisting of three conjugated chromophores and TiO2 
Kobasa I.M.1, Sema O.V.1, Kropelnytska Yu.V.2
1 Yu. Fedkovych National University of Chernivtsi.
2 Kotsyubynsky St., Chernivtsi, 58012, Ukraine.
E-mail: I.Kobasa@chnu.edu.ua
2 Bucovina State Medical University,
2 Theatralna Sq., Chernivtsi, 58002, Ukraine.

It seems important to develop new photocatalytic systems, which are active within the visible and near IR spectral zones and can be used in the light conversion and accumulation solutions and applications. That is why a problem of sensitization of the wide-zone semiconductors, like titanium dioxide, keeps high topicality and attracts many efforts to the field of search for new effective sensitizing agents. 
This work reports results of introduction of the polymethine dye 9-ezenyl-2,4,5,7-tetranitro-[2-(2,4,5,7-tetranitro-9H-fluorene-9-ezenyl)propyleden] triethyl ammonium 9-H-fluorene consisting of three conjugated chromophores as a sensitizer. 
The changes in the dye’s spectrum occurring at synthesis of the heterostructures based on TiO2 have been investigated while photocatalytic activity of these materials was measured in the test reaction of reduction of methylene blue. A character of influence of the semiconductor on the dye-sensitizer was determined and analyzed. As a result, it was found that the photocatalytic activity is decreasing with increase in the dye content because of weakening of its interaction with the semiconductor. A mechanism of photocatalytic activity was proposed and proved by experimental results obtained in the reactions of methylene blue reduction involving the heterostructures with different quantitative and qualitative composition.