1,721,074 research outputs found
Metal Oxide Semiconductors for Dye- and Quantum-Dot-Sensitized Solar Cells
No full textThis Review provides a brief summary of the most recent research developments in the synthesis and application of nanostructured metal oxide semiconductors for dye sensitized and quantum dot sensitized solar cells. In these devices, the wide bandgap semiconducting oxide acts as the photoanode, which provides the scaffold for light harvesters (either dye molecules
or quantum dots) and electron collection. For this reason,
proper tailoring of the optical and electronic properties of the photoanode can significantly boost the functionalities of the operating device. Optimization of the functional properties relies with modulation of the shape and structure of the photoanode, as well as on application of different materials (TiO2, ZnO, SnO2) and/or composite systems, which allow fine tuning of electronic band structure. This aspect is critical because it determines exciton and charge dynamics in the photoelectrochemical system and is strictly connected to the photoconversion efficiency of the solar cell. The different strategies for increasing light harvesting and charge collection, inhibiting charge losses due to recombination phenomena, are reviewed thoroughly, highlighting the benefits
of proper photoanode preparation, and its crucial role in the development of high efficiency dye sensitized and quantum dot sensitized solar cells
Single-Step Microwave-Assisted Synthesis of La0��6Sr0��4Co0��2Fe0��8O3−�� Perovskite
No full textLa06 Sr04 Co02 Fe08 O3− perovskite powder was prepared by a single-step process based on a
microwave-assisted citrate gel route. The structure, morphology, as well as surface properties and
thermal stability of the resulting material were deeply investigated by different techniques (XRD,
Delivered by Ingenta to:
SEM, XPS, BET and TGA). The powder resulted homogeneous with an excellent thermal stability.
Universita degli Studi di Padova
Preliminary catalytic tests revealed a promising activity in alcohol steam reforming. This simple,
fast and general synthetic approach is expected to be valuable in order to open the path towards a
scale up in the production of these materials
Stabilisation of monometallic nanoparticles by polyamide 6
No full textMonometallic metal nanoparticles (Pd, Pt, Ag and Ru) stabilised by polyamide 6 (PA6) have been prepared via a polyol process sustained by microwave irradiation. PA6 proved to be a good stabiliser, being spherical particles with little dimensional dispersion identified by transmission electron microscopy. Due to the inclusion of the metals in small amount (up to 3% w/w) into the macromolecular lattice, the polymer underwent changes in thermal behaviour, which, however, do not impair the possibility to process the material. The observed changes in differential scanning calorimetry curves indicated that metal containing PA6 materials are less crystalline and ordered than pure PA6. This was confirmed by diffuse reflectance infrared Fourier transform analysis, which indicated that the introduction of the metal nanoparticles lowered the conformational order of the polymer matrix and partly disrupted the hydrogen bond network of the polyamide
Quantum dots as mediators in gas sensing: A case study of CdS sensitized WO3 sensing composites
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Growth kinetics of CdSe quantum dots generated in polar polymers
No full textGrowth kinetics of CdSe nanocrystals generated inside three selected polymers (polyvinylpyrrolidone - PVP, polyethyleneglycol - PEG and polyvinylalcohol - PVA) are demonstrated to follow a self-catalytic path, with growth rates depending on the nature of the polymer, i.e. on the capability to activate the cadmium species present in the solution of a metal precursor. A two-step process drives the size evolution of nanocrystals and a critical diameter value can be identified at which the growth regime changes. The medium-term stability evaluation of nanocomposites indicates that, after an initial rearrangement, polymers keep stable the embedded CdSe nanocrystals
Deposition of Nanostructured CdS Thin Films by Thermal Evaporation Method: Effect of Substrate Temperature
No full textNanocrystalline CdS thin films were grown on glass substrates by a thermal evaporation method in a vacuum of about 2 × 10-5Torr at substrate temperatures ranging between 25 °C and 250 °C. The physical properties of the layers were analyzed by transmittance spectra, XRD, SEM, and four-point probe measurements, and exhibited strong dependence on substrate temperature. The XRD patterns of the films indicated the presence of single-phase hexagonal CdS with (002) orientation. The structural parameters of CdS thin films (namely crystallite size, number of grains per unit area, dislocation density and the strain of the deposited films) were also calculated. The resistivity of the as-deposited films were found to vary in the range 3.11-2.2 × 104Ω·cm, depending on the substrate temperature. The low resistivity with reasonable transmittance suggest that this is a reliable way to fine-tune the functional properties of CdS films according to the specific application
Electronic Noses as Flexible Tools to Assess Food Quality and Safety: Should we Trust Them?
No full textThis paper presents three different applications of an electronic nose (EN) based on a metal oxide sensor array, in order to illustrate the broad spectrum of potential uses of the technique in food quality control. The following scenarios are considered: 1) the screening of a typical error that may occur during the processing of tomato pulp, which leads to sensory damage of the product; 2) the detection of microbial contamination by Alicyclobacillus spp. (ACB) affecting soft drinks; and 3) the proof of evidence of extra virgin olive oil fraudulently adulterated with hazelnut oil. In each case, the EN is able to identify the spoiled product by means of the alterations in the pattern of volatile compounds, reconstructed by principal component analysis of the sensor responses
One-dimensional nanostructured oxides for thermoelectric applications and excitonic solar cells
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