Heterobimetallic Ru(II)/M (M = Ag+, Cu2+, Pb2+) Complexes as Photosensitizers for Room-Temperature Gas Sensing

Abstract

This work is devoted to the investigation of heterobimetallic Ru(II) complexes as photosensitizers for room-temperature photoactivated In2O3-based gas sensors. Nanocrystalline In2O3 was synthesized by the chemical precipitation method. The obtained In2O3 matrix has a single-phase bixbyite structure with an average grain size of 13–14 nm and a specific surface area of 72 ± 3 m2/g. The synthesis of new ditope ligands with different coordination centers, their ruthenium complexes, and the preparation of heterobimetallic complexes with various cations of heavy and transition metals (Ag+, Pb2+, or Cu2+) is reported. The heterobimetallic Ru(II) complexes were deposited onto the surface of the In2O3 matrix by impregnation. The obtained hybrid materials were characterized by X-ray fluorescent analysis, FTIR spectroscopy, and optical absorption spectroscopy. The elemental distribution on the hybrids was characterized by energy-dispersive X-ray spectroscopy (EDS) mapping. The gas sensor properties were investigated toward NO2, NO, and NH3 at room temperature under periodic blue LED irradiation. It was identified that the nature of the second binding cation in Ru(II) heterobimetallic complexes can influence the selectivity toward different gases. Thus, the maximum sensor signal for oxidizing gases (NO2, NO) was obtained for hybrids containing Ag+ or Pb2+ cations while the presence of Cu2+ cation results in the highest and reversible sensor response toward ammonia. This may be due to the specific adsorption of NH3 molecules on Cu2+ cations. On the other hand, Cu2+ ions are proposed to be active sites for the reduction of nitrogen oxides to N2. This fact leads to a significant decrease in the sensor response toward NO2 and NO gases.

NO2 Sensing Capability of Pt–Au–SnO2 Composite Nanoceramics at Room Temperature

“…There have been extensive investigations devoted to developing NO 2 gas sensors based on metal oxides [ 9 , 10 , 11 , 12 , 13 , 14 ], and many of them have been focused on developing room-temperature metal oxide NO 2 gas sensors. Room temperature operation is not only important for low power consumption, but also for miniaturization.…”

Sensitization of ZnO Photoconductivity in the Visible Range by Colloidal Cesium Lead Halide Nanocrystals

“…It was shown that, for example, when ZnO is sensitized with eosin, methylene blue and crystal violet, the photoconductivity of the resulting structures upon irradiation with visible light increases up to times compared with the unsensitized sample [ 16 , 17 , 18 ]. Some modern studies also consider dye-sensitized metal oxides as promising functional materials [ 19 , 20 , 21 , 22 ]. However, when using dyes, a number of disadvantages are found, for example, low stability to heating and oxidation of dye molecules, which makes it difficult to manufacture structures with long-term stability.…”