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Electrospun titania nanofibres combine large surface area with intrinsic semiconducting properties, thus providing great potential to such material for various applications. Anatase is the most photoactive phase of titania, and is then eligible for sensor, optoelectronic and catalytic devices, playing also a crucial role in disinfection applications and environmental remediation processes. As n-type semiconductor, titania nanofibres have been widely investigated and used for detecting several atmospheric pollutants at both high and room temperature, after the addition of organic and inorganic dopants [1]. Recently, Au/TiO2 nanocomposite layers have been investigated by the authors as potential conductive sensors to detect elemental mercury at room temperature in the atmosphere [2]. Because of their high sensitivity combined with low maintenance, easy of handling and low fabrication costs, such sensors resulted as promising candidates to detect mercury in proximity of polluted areas. In that study, the photocatalytic properties of titania allowed gold nanoparticles to selectively grow on the nanofibrous scaffold from HAuCl4 (tetrachloroauric acid) as a precursor, under UV-light irradiation. The results obtained in that study, however, were far enough from commercial analytical devices, which detect traces of mercury (< 0.1 ng/m3) in a few minutes (~5min). A great exposure time was necessary, indeed, to trap enough mercury in order to get observable electrical signals. In the present study, the amazing properties of titania were further employed in distinct strategies to improve the sensing features of the material and the resulting sensors. In the former strategy, rougher nanofibrous layers of titania were created, in order to greatly increase the number of gold nucleation sites. This finding was achieved by adding an aliquot of a non-ionic surfactant (Triton X) in the freshly prepared electrospun solution. SEM, AFM, TEM and HR-TEM analyses were carried out to characterise the morphology and the nano-sized structures of such composite nanofibres. It is known that the sensor response depends on the number of mercury atoms adsorbed on its sensitive surface. The increase in the global number of binding sites on the electrospun fabric was, then, expected to be successful in improving the sensor performances. In the latter strategy, UV-light (365 nm) was applied on the nanocomposite material in order to enable titania to cooperate with gold in mercury entrapment [3] and then enlarge the properties of the sensing layer. Optical and electrical features of both rough and UV-treated Au/TiO2 layers are here reported and discussed.

The use of nanostructured materials, such as those based on metal or metal oxides, has opened a new way to enhance the performances of chemical sensors making them able to detect gases at ppb level. In this type of sensors, the conductance is modulated by the presence of analytes that interact through physical-chemical processes of absorption and desorption, inducing changes in mobility or carriers density. The nano-scale dimensions of these materials enhance the interaction phenomena in terms of time and responses. In order to activate the physical/chemical interaction processes of the sensors based on oxide materials, an high operating temperature (200-400 °C) is required, resulting in significant power consumption. In this chapter, we report our recent studies on the possibility to exploit the titania photoconduction to develop gas sensor devices working at room temperature. We present the characterization of two different photoconductive Electrospun sensing layers: the first one is composed of titania nanofibres (TiO2 NFs) and the second of TiO2 NFs decorated with Pt nanoparticles (PtNPs) ranging from 5 to 10 nm.

Among various attempts of mimicking olfactory system the present work focuses on the sensorial surface of mammalian olfactory cells. The aim of this research is to develop, in a single step, synthetic fibres mimicking the long, no motile cilia of the olfactory cells. Electrospun conductive nanofibrous layers of doped polyaniline, suitably blended to a group of polymers capable to carry the jet, have been easily assembled on chemoresistors (interdigital microelectrodes, IDEs). Such highly sensitive sensors have been able to detect gases in traces of relevant medical significance, mainly because of high density of sorption sites of the sensor. Changing the carriers, the range of sensitivity to gases could be tuned. The key role of the selected carrier polymers (polyethylenoxide of different molecular weights, PEO, polyvinilpyrrolidone, PVP, and polystyrene, PS) to the final sensor features has been highlighted by morphology analysis (texture analysis) and electrical measurements before and after gas interaction.