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Food poisoning is still the first cause of hospitalization worldwide and the most common microbial agent, Campylobacter jejuni , is the most commonly reported gastrointestinal disease in humans in the EU (European Union) as is reported by the European Union One Health 2018 Zoonoses Report styled by the EFSA (European Food Safety Authority) and ECDC (European Center for Disease Prevention and Control). One of the vehicles of transmission of this disease is milk. Nanostructured MOS (Metal Oxide Semiconductor) sensors have extensively demonstrated their ability to reveal the presence and follow the development of microbial species. The main objective of this work was to find a set up for the detection and development follow up of C. jejuni in milk samples. The work was structured in two different studies, the first one was a feasibility survey and the second one was to follow up the development of the bacteria inside milk samples. The obtained results of the first study demonstrate the ability of the sensor array to differentiate the contaminated samples from the control ones. Thanks to the second study, it has been possible to find the limit of microbial safety of the contaminated milk samples.

In this work we report on metal oxide (MOX) based gas sensors, presenting the work done at the SENSOR laboratory of the CNR-IDASC and University of Brescia, Italy since the 80s up to the latest results achieved in recent times. In particular we report the strategies followed at SENSOR during these 30 years to increase the performance of MOX sensors through the development of different preparation techniques, from Rheotaxial Growth Thermal Oxidation (RGTO) to nanowire technology to address sensitivity and stability, and the development of electronic nose systems and pattern recognition techniques to address selectivity. We will show the obtained achievement in the context of selected applications such as safety and security and food quality control.

Synthesis of Nb-containing titania nanotubular arrays at room temperature by electrochemical anodization is reported. Crystallization of pure and Nb-doped TiO(2) nanotubes was carried out by post-growth annealing at 400°C. The morphology of the tubes obtained was characterized by scanning electron microscopy (SEM). Crystal structure and composition of tubes were investigated by glancing incidence x-ray diffraction (GIXRD) and total reflection x-ray fluorescence (TXRF). For the first time gas sensing characteristics of Nb-doped TiO(2) nanotubes were investigated and compared to those of undoped nanotubes. The functional properties of nanotubular arrays towards CO, H(2), NO(2), ethanol and acetone were tested in a wide range of operating temperature. The introduction of Nb largely improves conductivity and enhances gas sensing performances of TiO(2) nanotubes.

Self-assembled molecular thin films of melamine-bridged bis-porphyrin dyad, both in free form, P(H2)P(H2), or as Zn(II) metallated complex, P(Zn)P(Zn), were deposited on crystalline Si(100) by soaking or drop-casting techniques. The influence of the adopted preparation methodology, the substrate surface pre-activation procedure and the used solvent (THF or CHCl3) on the morphology and surface coverage of the resulting films was investigated by FE-SEM (Field Emission-Scanning Electron Microscopy) and AFM (Atomic Force Microscopy). The chemical composition and electronic structure of the most promising systems were also addressed by XPS (X-ray Photoelectron Spectroscopy). The results pointed out that an accurate tuning of porphyrin-porphyrin, porphyrin-substrate and porphyrin-solvent molecular interactions allow to tailor the morphogenesis and chemico-physical properties of the final self-assembled films. In addition, preliminary gas sensing tests evidenced the potential of the present porphyrin-based films for the development of new molecular sensing devices.

Titanium dioxide (TiO 2 ) nanostructures were grown directly on the sensitive area of the transducer. A titanium thin film was deposited on 2 · 2 mm 2 alumina substrates by RF magnetron sputtering and hydrothermal method was used to achieve TiO 2 . This method is characterized by the use of different solutions (KOH, NaOH), a not stirred pressure reactor and a heating system. As-prepared samples require an acid treatment followed by a calcination step to obtain pure TiO 2 nanostructures. The nanostructured morphology was confirmed by a scanning electron microscope (SEM) and their structural properties were investigated by RAMAN spectroscopy. Obtained samples were used as gas sensors, and their behaviour towards several gaseous species was analysed in a wide range of working temperatures. Measurements were carried out in a test chamber, investigating the change in the electrical conductance due to the surrounding atmosphere. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) mat-based conductometric devices were fabricated using a thermal oxidation technique. A metallic zinc layer was deposited on the alumina transducer and then oxidized in a controlled atmosphere, in order to obtain ZnO nanostructures. Two different batches of sensors have been prepared, and their sensing performances have been evaluated towards oxidizing and reducing gases. Functional measurements showed very good sensing performances towards ethanol and acetone at 500 ° C, and NO2 at 200 ° C, indirectly confirming the n-type behaviour of the material. The influence of the humidity on the response has been explored. In practical conditions the interference of humidity is very small, and could be neglected in many applications. Simultaneous measurements on different devices from the same batch confirm the high reproducibility of the response within the batch. [ABSTRACT FROM AUTHOR]

Quasi-one-dimensional nanostructures of tin oxide were produced in controlled conditions through condensation from the vapor phase. The preparation was assisted by noble metal catalysts and uniform single-crystalline nanowires were produced. The nucleation of nanowires was achieved at 470 °C, owing to the vapor–liquid–solid growth mechanism activated by the catalytic Pt clusters. The peculiar microstructural properties of these semiconducting metal oxide nanostructures will be summarized. The high aspect ratio and the high degree of crystallinity achieved for the nanowires foresee their functional exploitation. [ABSTRACT FROM AUTHOR]

Progress has been achieved in the synthesis, structural characterization and physical properties investigation of nanostructures. We have focused our attention on zinc oxide nanostructures. We report on the growth of ZnO nanostructures using vapour phase technique. We have synthesized, depending on the growth conditions, different nanostructures such as wires and combs of zinc oxide. ZnO nanowires electrical properties have been characterised in presence of different gases, the results highlight remarkable response to acetone and ethanol with detection limits lower than 1 ppm. [ABSTRACT FROM AUTHOR]

Abstract: CuO nanowires (NWs) were grown by thermal oxidation of metallic Cu thin layer deposited by sputtering on different substrates. Optimal growth parameters were found, studying the influence of the oxidizing temperature and the atmosphere during the oxidation process. A strong relation between oxidation parameters and morphology has been detected. The preliminary response of this sensing material, using nanowire's mat-based device, to various oxidizing and reducing target gases has been evaluated, in order to corroborate the functional properties of the CuO NWs as potential sensing material under certain conditions and to confirm the p-type conductometric response of the material. [Copyright &y& Elsevier]

Abstract: Different ZnO nanostructures were synthesized by physical vapor deposition on glass-ITO substrates. Nanowires and nanosheets were obtained by a single step process using gold nanoparticles and gold thin films as catalyst. 3D nanoarchitectures were obtained by a two-step modified process; the morphology of these structures depends on the catalyst used for the second deposition: gold nanoparticles or zinc acetate seeds. All the nanostructures were characterized by SEM and TEM analyses, which showed the different morphology under same conditions of temperature, pressure, oxide precursor and deposition time. Dye-sensitized solar cells based on these ZnO structures were successfully assembled, using N179 as sensitizer with efficiencies between 0.1% and 0.5%. In spite of the low efficiency of the cells, a novel double PVD process is presented and its integration capability into solar cell devices has been proven. [Copyright &y& Elsevier]

Abstract: Supported copper oxide nanosystems were synthesized by chemical vapor deposition (CVD) on Al2O3 substrates and characterized by means of glancing incidence X-ray diffraction (GIXRD), secondary ion mass spectrometry (SIMS) and field emission scanning electron microscopy (FESEM). The analyses showed an evolution from polycrystalline Cu2O nanodeposits to CuO samples with an entangled quasi-1D morphology upon increasing the growth temperature from 350 to 550°C. For the first time, the sensing properties of CVD copper oxide nanosystems were probed in the detection of volatile organic compounds (VOCs; e.g. CH3COCH3, CH3CH2OH). The obtained results revealed good responses even at moderate operating temperatures, with characteristics directly dependent on the system composition and nano-organization. [Copyright &y& Elsevier]

Abstract: Tin oxide nanostructures are currently considered as promising materials for gas sensing. Some of their physical properties, such as visible light photoluminescence, are still not fully understood and require further investigations. In this work we report on the quenching of tin oxide nanowires photoluminescence induced by nitrogen dioxide adsorption at the ppm and sub-ppm level. The recombination dynamics was investigated by means of time-resolved photoluminescence, finding non-exponential decay profiles. Neither the photoluminescence spectral shape nor the decay rates are found to depend significantly on the nitrogen dioxide concentration, suggesting that the gas-nanostructure interaction resides in a net reduction of the density of states which are responsible for the radiative transitions. [Copyright &y& Elsevier]

Abstract: We have investigated the sensing properties of indium oxide nanostructures and tailored the deposition conditions in order to obtain nano-wires of indium oxide. We have comparatively tested the gas sensing properties of nano-wires with micrometric or even nanometric size. The micro-wires feature interesting gas sensitivity at room temperature, particularly in the case of nitrogen dioxide detection. The sensing performance is improved as the lateral dimension of the wire decreases. [Copyright &y& Elsevier]

Abstract: Semiconducting oxides in nanowire-shape have stimulated a great interest for applications in optics and sensor fields. Recently, it has been reported that tin oxide (SnO2) nanowires can be grown by vapor transport techniques through a vapor–liquid–solid (VLS) mechanism. In this work, we present the results of a study on the mechanism involved in the crystallization process of SnO2 nanowires, pointing out that the presence of a liquid phase is necessary to grow these nanocrystals in the 800–1000°C temperature range. Characterization of the obtained samples has been performed by XRD, TEM and SEM analysis. [Copyright &y& Elsevier]