Dario Narducci

Thick Film ZnO Resistive Gas Sensors Analysis of Their Kinetic Behavior

Thick film polycristalline ZnO gas sensors for hydrogen partial pressure determination in hydrogen-air mixtures present at very complex kinetic behavior that demands to be thoroughly clarified in order for them to be used in practical applications. For this reason a systematic investigation has been carried out on the time and temperature dependence of the electrical conductivity of ZnO films deposited via spray pyrolysis on ceramic substrates in the temperature range 498-573 K in the presence of dispersed Pt as the catalyst

Do we really need high thermoelectric figures of merit? A critical appraisal to the power conversion efficiency of thermoelectric materials

This paper will show that, while ZT is an appropriate performance index when optimizing the heat conversion rate, it may mislead research in view of applications aiming at large electric power production. This is of special relevance when related to the surge of research in the area of low-dimensionality semiconductors where ZT is increased by lowering the thermal conductivity κ. It will be shown that, when operating between sources at fixed temperature, the highest power output can be obtained by increasing κ, not decreasing it, the larger electric power output economically enabling thermoelectric generators for massive electric power production.

Preferential formation of Si-O-C over Si-C linkage upon thermal grafting on hydrogen-terminated silicon (111).

In a stringent and near oxygen-free environment, Si-H surfaces were introduced to a trifluoroalkyne, an alcohol-derivatized alkyne, as well as an equal mixture of both alkynes at a temperature of 130 °C. Contact angle measurements, high-resolution X-ray photoelectron spectroscopy (XPS), and angle-resolved XPS were performed to examine the system. Si-H surfaces were found to have a strong preference towards the formation of Si-O-C rather than Si-C bonds when the alcohol and alkyne reactivities were compared.

Short-range order of Zn and Cu in metaphosphate glasses by X-ray diffraction

The coordination of Zn2+ and Cu2+ ions in two metaphosphate glasses was investigated by X-ray diffraction. An average coordination number of five oxygen atoms was obtained for both cations through the analysis of the short-range features of the radial functions. Furthermore, the consistency of diffraction data with the metaphosphate chain model was demonstrated. Structural implications of these results are discussed.

Electron paramagnetic resonance study of the interaction of the ZnO surface with air and air–reducing gas mixtures

The variation of the defect number that results from the interaction of ZnO with air–reducing gas mixtures (H2–air and CO–air) has been investigated by EPR spectroscopy. It appears that up to 573 K the surface interaction with CO or H2 and air is dominated by the reaction of CO or H2 with the chemisorbed oxygen species (O–2 and O–); at higher temperature the main process is the formation of new oxygen vacancies. The CO effect is stronger than that of H2 up to 573 K; after this temperature the relative importance reverses and H2 is more efficient than CO in producing new oxygen vacancies.

Coordination of zinc and copper in phosphate glasses by EXAFS

Abstract The coordination of Zn2+ and Cu2+ ions in semiconducting phosphate glasses was investigated by EXAFS spectroscopy. A change in Zn coordination occurs when the glass composition deviates from metaphosphate. The results are consistent with the hypothesis that Cu(II) and Cu(I) occupy sites with different coordination geometries, but with entire coordination polyhedra similar for all copper atoms. The consistency of the structural model with the semiconducting properties of the glasses is examined.

An introduction to nanotechnologies: what's in it for us?

Narducci, D., 2007. An introduction to nanotechnologies: what’s in it for us? Veterinary Research Communications, 31(Suppl. 1), 131–137ABSTRACTNanotechnologies are one of the two most prominent actors of the scientific revolution marking the beginning of the new Millennium. As for biotechnology, nanotechnologies are the outcome of an interdisciplinary, new approach to old technological issues ranging from device manufacturing to energy conversion, from sensing to signal amplification and transmission. The discovery of unexpected physical and chemical behavior of matter at the nanometer scale has paved the way to a number of exploitations (some current, most real but prospective). In this paper I will briefly review the nanotechnologies, showing most promise for Medicine and Veterinary Medicine. In this specific area, I will discuss current techniques and soon-to-come applications in nano-pharmaceuticals (i.e. pharmaceuticals based on the specific chemistry of nanoparticles), in vivo targeted nanodispensers, and nanoactuators. Some closing remarks will be made on how this will affect animal health control and healing in the near future.

Transmission electron microscopy investigation of tin sub‐oxide nucleation upon SnO2 deposition on silicon

Transmission electron microscopy analysis of tin dioxide films grown by aerosol‐assisted chemical vapor deposition onto oxidized or etched silicon displayed the formation of a sub‐oxide phase that was identified as Sn2O3. Such a phase is observed to disappear upon heat treatment, and is believed to be one of the factors responsible for the instability of tin dioxide films used as gas sensing layers.

Formation of stable Si–O–C submonolayers on hydrogen-terminated silicon(111) under low-temperature conditions

Summary In this letter, we report results of a hydrosilylation carried out on bifunctional molecules by using two different approaches, namely through thermal treatment and photochemical treatment through UV irradiation. Previously, our group also demonstrated that in a mixed alkyne/alcohol solution, surface coupling is biased towards the formation of Si–O–C linkages instead of Si–C linkages, thus indirectly supporting the kinetic model of hydrogen abstraction from the Si–H surface (Khung, Y. L. et al. Chem. – Eur. J. 2014, 20, 15151–15158). To further examine the probability of this kinetic model we compare the results from reactions with bifunctional alkynes carried out under thermal treatment (<130 °C) and under UV irradiation, respectively. X-ray photoelectron spectroscopy and contact angle measurements showed that under thermal conditions, the Si–H surface predominately reacts to form Si–O–C bonds from ethynylbenzyl alcohol solution while the UV photochemical route ensures that the alcohol-based alkyne may also form Si–C bonds, thus producing a monolayer of mixed linkages. The results suggested the importance of surface radicals as well as the type of terminal group as being essential towards directing the nature of surface linkage.

Surface modification strategies on mesoporous silica nanoparticles for anti-biofouling zwitterionic film grafting

In the past decade, zwitterionic-based anti-biofouling layers had gained much focus as a serious alternative to traditional polyhydrophilic films such as PEG. In the area of assembling silica nanoparticles with stealth properties, the incorporation of zwitterionic surface film remains fairly new but considering that silica nanoparticles had been widely demonstrated as useful biointerfacing nanodevice, zwitterionic film grafting on silica nanoparticle holds much potential in the future. This review will discuss on the conceivable functional chemistry approaches, some of which are potentially suitable for the assembly of such stealth systems.