In this work, the hybrids based on nanocrystalline SnO₂ or In₂O₃ semiconductor matrixes and heterocyclic Ru(II) complex are studied as materials for gas sensors operating at room temperature under photoactivation with visible light. Nanocrystalline semiconductor oxides are obtained by chemical precipitation with subsequent thermal annealing and characterized by XRD, SEM and single-point BET methods. The heterocyclic Ru(II) complex is synthesized for the first time and investigated by ¹H NMR, 13C NMR APT, MALDI-MS analysis, and UV-Vis spectroscopy. The HOMO and LUMO energies of the Ru(II) complex are calculated from cyclic voltammetry data. The hybrid materials are characterized by TGA-MS analysis and EDX mapping. The optical properties of hybrids are studied by UV-Vis spectroscopy in the diffuse reflection mode. The investigation of spectral dependencies of photoconductivity of hybrid samples demonstrates that the role of organic dye consists in shifting the photosensitivity range towards longer wavelengths. Sensor measurements demonstrate that hybrid materials are able to detect NO₂ in the concentration range of 0.25⁻2 ppm without the use of thermal heating under periodic illumination with even low-energy long-wavelength (red) light.
Keywords: NO2; Ru(II) complex; indium oxide; organic–inorganic hybrid materials; semiconductor gas sensor; tin dioxide; visible light activation.