Giorgio Sberveglieri

Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts

Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO2, as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and −1550% for 0.5 ppm NO2 at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb.

Ultrasensitive and highly selective gas sensors using three-dimensional tungsten oxide nanowire networks

The performance of a solid-state gas sensor is characterized by its sensitivity, stability, and selectivity. The working principle relies on modulation of electrical conductivity due to surface oxidation reduction caused by gas exposure. Because only the surface layer is affected by such reactions, the sensitivity is strongly dependent on the surface-to-volume ratio of the material used. This purpose has been pursued by synthesizing layers with a porous morphology to enhance the material surface area. Porosity is enhanced by means of the thick film synthesis approach typically adopted in the gas sensing field. Such high porosity is not easy to achieve by thin film approach. Another approach largely used in the field is the rheotaxial growth and its thermal oxidation RGTO method, which allows synthesizing a porous thin film mono

Hierarchically Assembled ZnO Nanocrystallites for High‐Efficiency Dye‐Sensitized Solar Cells

exhibit the highest performance interms of energy conversion efficiency and long term stability,despite the fact that the efficiency remains below 13%because of the intrinsic limitation in charge transport. Thestructure of the photoelectrodes is crucial in determining thefunctional properties of the photoelectrochemical system. Inparticular, the photoanode consists of a mesoporous wide-band-gap oxide semiconductor film with a high specificsurface (typically a thousand times larger than the bulkcounterpart).

Solid state gas sensing

Micro-Fabrication of Gas Sensors.- Electrical-Based Gas Sensing.- Capacitive-Type Relative Humidity Sensor with Hydrophobic Polymer Films.- FET Gas-Sensing Mechanism, Experimental and Theoretical Studies.- Solid-State Electrochemical Gas Sensing.- Optical Gas Sensing.- Thermometric Gas Sensing.- Acoustic Wave Gas and Vapor Sensors.- Cantilever-Based Gas Sensing.

Adsorption effects of NO2 at ppm level on visible photoluminescence response of SnO2 nanobelts

The visible photoluminescence (PL) of tin oxide nanobelts is quenched by nitrogen dioxide at ppm level in a fast (time scale order of seconds) and reversible way. Besides, the response seems highly selective toward humidity and other polluting species, such as CO and NH3. We believe that adsorbed gaseous species that create surface states can quench PL by creating competitive nonradiative paths. A comparison between conductometric and PL response suggests that the two responses are ascribable to different adsorption processes.

Metal oxide nanowires as chemical sensors

It is almost a decade since the first presentation of metal oxide nanowires as chemical sensors. Significant advances have been made both in terms of preparation procedures and their integration into functional sensing devices, whilst the progress in their fundamental understanding of functional properties has been slow. In fact, the full integration still remains a challenge that has been wisely approached in different ways. In this article we review the most recent developments in bottom up and top down approaches for applications of chemical sensors.

Co3O4/ZnO nanocomposites: from plasma synthesis to gas sensing applications.

Herein, we describe the design, fabrication and gas sensing tests of p-Co(3)O(4)/n-ZnO nanocomposites. Specifically, arrays of (001) oriented ZnO nanoparticles were grown on alumina substrates by plasma enhanced-chemical vapor deposition (PECVD) and used as templates for the subsequent PECVD of Co(3)O(4) nanograins. Structural, morphological and compositional analyses evidenced the successful formation of pure and high-area nanocomposites with a tailored overdispersion of Co(3)O(4) particles on ZnO and an intimate contact between the two oxides. Preliminary functional tests for the detection of flammable/toxic analytes (CH(3)COCH(3), CH(3)CH(2)OH, NO(2)) indicated promising sensing responses and the possibility of discriminating between reducing and oxidizing species as a function of the operating temperature.

Columnar CeO2 nanostructures for sensor application

CeO2 columnar nanostructures with tailored properties were synthesized by chemical vapour deposition on Si(100) and Al2O3 substrates between 350 and 450 °C and characterized in their structure, composition and morphology by means of a multi-technique approach. Their higher sensitivity in the detection of gaseous ethanol and nitrogen dioxide with respect to continuous CeO2 thin films opens interesting perspectives for the development of nanosized sensor devices.

Bovine Serum Albumin protofibril-like aggregates formation: Solo but not simple mechanism

We report an experimental study on the model protein Bovine Serum Albumin (BSA), with the aim of elucidating the mechanisms by which a fully folded globular protein undergoes different aggregation pathways leading to the formation of amyloid fibrils or amorphous aggregates. We observe thermally induced formation of fibrillar structures at pH far from the protein isoelectric point. The increase of electrostatic repulsion results in protein destabilization and in modifications of inter and intra-molecular interactions leading to the growth of fibril-like aggregates stabilized by inter-molecular-β sheets. The aggregation kinetics is studied by means of fluorescence techniques, light scattering, Circular Dichroism (CD), infrared spectroscopy (FTIR) and Atomic Force Microscopy (AFM). Changes in protein secondary structures turn out to be the driving mechanism of the observed aggregation and they progress in parallel with the growth of Thioflavin T emission intensity and scattering signal. This concurrent behavior suggests a mutual stabilization of elongated protofibril-like structures and of protein conformational and structural changes, which lead to a more rigid and ordered structures. Our results give new insights on BSA self-assembly process in alkaline conditions clearly providing new pieces of evidences of the interplay of several and interconnected mechanisms occurring on different time and length scales.

Electronic Nose for Microbiological Quality Control of Food Products

Electronic noses (ENs) have recently emerged as valuable candidates in various areas of food quality control and traceability, including microbial contamination diagnosis. In this paper, the EN technology for microbiological screening of food products is reviewed. Four paradigmatic and diverse case studies are presented: (a) Alicyclobacillus spp. spoilage of fruit juices, (b) early detection of microbial contamination in processed tomatoes, (c) screening of fungal and fumonisin contamination of maize grains, and (d) fungal contamination on green coffee beans. Despite many successful results, the high intrinsic variability of food samples together with persisting limits of the sensor technology still impairs ENs trustful applications at the industrial scale. Both advantages and drawbacks of sensor technology in food quality control are discussed. Finally, recent trends and future directions are illustrated.