Abstract
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.
Highlights
The World Health Organization (WHO) has included inorganic gases, i.e., carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2), and ozone (O3), in the list of gases that have indoor sources, which are known in respect of their hazardousness to health and are often found indoors in concentrations of health concern [1]
The particle size distributions for SnO2 and In2O3 samples obtained under similar conditions were investigated by transmission electron microscopy (TEM) in our previous work [28]
It was demonstrated that the use of the heterocyclic Ru(II) complex (Ru-TT) as a photosensitizer results in a shift of the photosensitivity of the wide-gap nanocrystalline metal oxides SnO2 and In2O3 toward longer wavelengths
Summary
The World Health Organization (WHO) has included inorganic gases, i.e., carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2), and ozone (O3), in the list of gases that have indoor sources, which are known in respect of their hazardousness to health and are often found indoors in concentrations of health concern [1]. Semiconductor gas sensors are promising for indoor and outdoor air monitoring because of their extremely high sensitivity, stability and miniaturization capability. The combination of gas sensors with information networks (including portable devices and mobile phones [2]) allows reporting a leakage and/or exceeding the maximum allowable concentration of hazardous gases upon short- or long-term exposures. The need for heating significantly increases power consumption, which is the main restriction for coupling gas sensors with portable and mobile devices. The design of new materials that show gas sensitivity under conditions of minimal thermal heating is one of the key directions in developing the technology of gas sensors and multisensor systems
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