Porphyrins coated ZnO nanostructure

The properties of dye-sensitized solar cells prompted the investigation of hybrid materials formed by a layer of dye molecules attached to a wide-band gap semiconductor. Besides to convert visible photons into an excess of carriers, the combination of these two materials can offer other additional properties, such as for example gas sensing. Indeed, metal oxide semiconductors are among the most diffused materials for gas sensing and several dye molecules have brilliant capabilities to bind airborne compounds.

The cooperation of porphyrins and ZnO gives rise to hybrid structures whose properties may exceed those of the individual constituents.  In these materials light interferes with the binding of guest molecules onto the porphyrin-ZnO complex. We demonstrated this conjecture measuring the conductivity and the surface potential (with a Kelvin Probe) in a device formed by an array of ZnO nanorods coated with a layer of a tetraphenylporphyrins. The device demonstrates that the contemporaneous sensitivity to light and gas gives place to a photoconductive gas sensor.

This opens the way to the development of innovative gas sensors where selectivity and sensitivity is based on the interplay between the response to light and to gas.