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In this research we report the gas-sensing properties of TiO2-x/TiO2-based hetero-structure, which was ‘self-heated’ by current that at constant potential passed through the structure. Amperometric measurements were applied for the evaluation of sensor response towards ethanol, methanol, n-propanol and acetone gases/vapours. The sensitivity towards these gases was based on electrical resistance changes, which were determined by amperometric measurements of current at fixed voltage applied between Pt-based contacts/electrodes deposited on the TiO2-x/TiO2-based layer. X-ray diffraction (XRD) analysis revealed the formation of TiO2-x/TiO2-based hetero-structure, which is mainly based on Ti3O5/TiO2 formed during the hydro-thermal oxidation-based sensing-layer preparation process. Additionally, photoluminescence and time-resolved photoluminescence decay kinetics-based signals of this sensing structure revealed the presence of TiO2 mainly in the anatase phase in the TiO2-x/TiO2-based hetero-structure, which was formed at 400 °C annealing temperature. The evaluation of TiO2-x/TiO2-based gas-sensing layer was performed at several different temperatures (25 °C, 72 °C, 150 °C, 180 °C) and at these temperatures different sensitivity to the aforementioned gaseous materials was determined.

Quality control of food and agriculture production is an inseparable part of human safety and well-being. Salmonella infections belong to one of the most monitored pathogens in the world, therefore advanced determination of this pathogen can decrease the risks of human diseases caused by this microorganism. In this research we introduce a novel optical immunosensor for determination of Salmonella typhimurium. The immunosensor is based on Titanium dioxide (TiO2) nanoparticles deposited on glass substrates (glass/TiO2). TiO2 nanoparticles exhibit an intense photoluminescence (PL) in the visible range of spectrum at room temperature. The direct immobilization of antibodies (anti-S-Ab) against Salmonella antigens on the surface of glass/TiO2 has resulted in the formation of glass/TiO2/anti-S-Ab-based structure, which was characterized by increased PL intensity and IR-shifted position of the PL peak in comparison to the same characteristics of glass/TiO2-based structure. The changes of the PL intensity and peak positions after interaction of the immobilized anti-S-Ab with Salmonella antigens (Salmonella-Ag) were used as immunosensor signal, allowing sensitive and selective detection of Salmonella-Ag in a label-free configuration. The sensitivity of the reported optical immunosensor towards Salmonella-Ag is in the range from 10 3 to 10 5 cell/ml. Some aspects of the interaction between TiO2 and biological compounds have been discussed. This work opens up new possibilities for 1 the development of optical label-free immunosensors suitable for fast, simple and efficient analysis of Salmonella infections.

Novel sensitive optical biosensor for determination of Grapevine virus A-type (GVA) proteins (GVA-antigens) has been designed. This biosensor was based on thin films of Zinc Oxide (ZnO) deposited by atomic layer deposition (ALD). The ZnO-based films have demonstrated favorable surface-structural properties for the direct immobilization of antibodies against GVA-antigens in order to form a biosensitive layer sensitive to GVA-antigens. The immobilization was confirmed by intensity changes in the main near band emission (NBE) peak of ZnO and by the formation of intense photoluminescence band, discovered in the visible range around 425nm, caused by the immobilized proteins. The GVA-antigen detection was performed by the evaluation of changes and behavior of a corresponding luminescence band. The sensitivity of as-formed label-free biosensor towards the GVA-antigens was determined in the range from 1pg/ml to 10ng/ml; in addition, the selectivity of biosensor was evaluated.