Functionalization of carbon fiber tows with ZnO nanorods for stress sensor integration in smart composite materials.

The physical and operating principle of a stress sensor, based on two crossing carbon fibers functionalized with ZnO nanorod-shaped nanostructures, was recently demonstrated. The functionalization process has been here extended to tows made of one thousand fibers, like those commonly used in industrial processing, to prove the idea that the same working principle can be exploited in the creation of smart sensing carbon fiber composites. A stress-sensing device made of two functionalized tows, fixed with epoxy resin and crossing like in a typical carbon fiber texture, was successfully tested. Piezoelectric properties of single nanorods, as well as those of the test device, were measured and discussed.

Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM.

Hole collection and transport are crucial physical processes in bulk-heterojunction (BHJ) solar cells, which represent major bottlenecks due to their limitations in power conversion efficiency (PCE). Hence, a more efficient alternative is needed to accept and transport holes to the collection electrode in BHJ solar cells. Here, we bring both electron and hole collection centres close to the point of exciton generation by infiltrating P3HT poly(3-hexylthiophene):PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend into a highly porous interconnected p-type NiO-nanoparticle (NiO-np) network, through solvent-assisted grafting. In this study, a hybrid polymer solar cell is demonstrated with a P3HT:PCBM:NiO-np triple-heterojunction active layer which showed greatly improved rectification behaviour, long electron lifetime and generated higher PCE of 4% under AM 1.5 solar illumination with a 75% increase in PCE with respect to the P3HT:PCBM device. The optimum NiO-np amount and active-layer thickness were found to be 2% and 250 nm, respectively.

A new method to integrate ZnO nano-tetrapods on MEMS micro-hotplates for large scale gas sensor production.

A new method, which is easily scalable to large scale production, has been developed to obtain gas sensor devices based on zinc oxide (ZnO) nanostructures with a 'tetrapod' shape. The method can be easily extended to other kinds of nanostructures and is based on the deposition of ZnO nanostructures through polymeric masks by centrifugation, directly onto properly designed MEMS micro-hotplates. The micromachined devices, after the mask is peeled off, are ready for electrical bonding and sensing test. Sensor response has been successfully measured for some gases and volatile organic compounds with different chemical properties (ethanol, methane, nitrogen dioxide, hydrogen sulfide).

Selective response inversion to NO2 and acetic acid in ZnO and CdS nanocomposite gas sensor.

High sensitivity zinc oxide (ZnO) tetrapods (TPs) have been functionalized by nucleating cadmium sulphide (CdS) nanoparticles (NPs) directly on their surface with a spotted coverage thanks to an optimized synthesis in dimethylformamide (DMF). The obtained hybrid coupled material has been used to realize a gas sensing device with a highly porous nanostructured network, in which the proper alternation of ZnO-TPs and CdS-NPs gives rise to unconventional chemoresistive behaviours. Among the different tested gases and vapours, the sensor showed a unique fingerprint response-inversion between 300 °C and 400 °C only for nitrogen dioxide (NO2) and acetic acid (CH3COOH).

Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles.

A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with 'tetrapod' morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m(2) kg(-1)), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis.

Solution-free and catalyst-free synthesis of ZnO-based nanostructured TCOs by PED and vapor phase growth techniques.

Zinc oxide (ZnO) is one of the most promising materials for realizing three-dimensional (3D) nanostructured transparent conducting oxides (TCOs) on large scale, because it is cheap, it can be modified with large concentrations of trivalent elements (such Al, Ga or In) and it is characterized by good electron mobility, wide bandgap and visible-range transparency. But, above all, it can be easily obtained in the form of different nanostructures with a large number of growth techniques. A solution-free and catalyst-free approach has been explored here by the vapor phase synthesis of vertically aligned ZnO nanorods on ZnO:Al (AZO) films grown by pulsed electron deposition (PED). The obtained nanostructured TCOs resulted to be homogeneous on large areas and easily patternable by means of mechanical masks. The morphology, crystalline structure, electrical and optical properties of the obtained samples have been characterized in depth. The possible use of such a nanostructured TCO in excitonic (e.g. DSSC) or low-reflectivity traditional solar cells is discussed.

Development of a combined SEM and ICP-MS approach for the qualitative and quantitative analyses of metal nano and microparticles in food products [corrected].

An integrated approach based on the use of inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM) for the qualitative and quantitative analyses of metal particles in foods was devised and validated. Different raw materials and food products, like wheat, durum wheat, wheat flour, semolina, cookies, and pasta were considered. Attention was paid to the development of sample treatment protocols for each type of sample to avoid potential artifacts such as aggregation or agglomeration. The analytical protocols developed followed by ICP-MS and SEM investigations allowed us the quantitative determination and the morphological and dimensional characterization of metal nano- and microparticles isolated from the raw materials and finished food products considered. The ICP-MS method was validated in terms of linearity (0.8-80 µg/g and 0.09-9 µg/g for Fe and Ti, respectively), quantification limits (0.73 µg/g for Fe and 0.09 µg/g for Ti), repeatability (relative standard deviation (RSD) % equal to 10% for Fe and 20% in a wheat matrix as an example), and extraction recoveries (93 ± 2-101 ± 2%). Validation of the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) measurements was performed working in a dimensional range from 1 to 100 µm with an estimated error in the size determination equal to 0.5 µm. ICP-MS data as well as SEM measurements showed a decrease in the concentration of metal particles from wheat to flour and from durum wheat to semolina samples, thus indicating an external contamination of grains by metal particles. These findings were confirmed by environmental SEM analysis, which allowed investigation of particles of lower dimensions. Generally, the largest number of particles was found in the case of iron and titanium, whereas particles of copper and zinc were only occasionally found without any possibility of quantifying their number.

Silica diatom shells tailored with Au nanoparticles enable sensitive analysis of molecules for biological, safety and environment applications.

Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin-BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring.

Zn vacancy induced green luminescence on non-polar surfaces in ZnO nanostructures.

Although generally ascribed to the presence of defects, an ultimate assignment of the different contributions to the emission spectrum in terms of surface states and deep levels in ZnO nanostructures is still lacking. In this work we unambiguously give first evidence that zinc vacancies at the (1010) nonpolar surfaces are responsible for the green luminescence of ZnO nanostructures. The result is obtained by performing an exhaustive comparison between spatially resolved cathodoluminescence spectroscopy and imaging and ab initio simulations. Our findings are crucial to control undesired recombinations in nanostructured devices.