1,721,017 research outputs found
Live-monitoring of Te inclusions laser-induced thermo-diffusion and annealing in CdZnTe crystals
No full textThe presence of Te inclusions is one of the main factors limiting performances of CdZnTe crystals as X-ray detectors. We show that by means of infrared laser radiation it is possible to move and anneal tellurium inclusions exploiting a thermo-diffusion mechanism. The process is studied live during irradiation by means of an optical microscope equipment. Experimental conditions, and, in particular, energy laser fluence, for annealing inclusions of different dimensions are determined
Analytical approaches for the characterization and quantification of nanoparticles in food and beverages
Full text link<p>Estimating consumer exposure to nanomaterials (NMs) in food products and predicting their toxicological properties are necessary steps in the assessment of the risks of this technology. To this end, analytical methods have to be available to detect, characterize and quantify NMs in food and materials related to food, e.g. food packaging and biological samples following metabolization of food. The challenge for the analytical sciences is that the characterization of NMs requires chemical as well as physical information. This article offers a comprehensive analysis of methods available for the detection and characterization of NMs in food and related products. Special attention was paid to the crucial role of sample preparation methods since these have been partially neglected in the scientific literature so far. The currently available instrumental methods are grouped as fractionation, counting and ensemble methods, and their advantages and limitations are discussed. We conclude that much progress has been made over the last 5 years but that many challenges still exist. Future perspectives and priority research needs are pointed out. [Figure not available: see fulltext.]</p
Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM
No full textHole 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
Two-step thermal process in tellurium vapor for tellurium inclusion annealing in high resistivity CdZnTe crystals
No full textExploitation of CdZnTe crystals for X-ray imaging detectors is limited by the incorporation of tellurium inclusions during growth. Over the years, several post-growth thermal treatments have been proposed for the removal of tellurium inclusions, often compromising the high electrical resistivity of the material. Moreover, main attention is usually paid to large inclusions, whose direct connection with the deterioration of detector properties has been demonstrated, while the effect of thermal annealing on small inclusions is usually neglected. In this article, the effect of different thermal annealing process on the concentration of inclusions down to 1 μm size is studied. A two-step process in tellurium vapors has been shown to be effective to anneal large tellurium inclusions and to preserve the high resistivity of the samples as well
UN SISTEMA E RELATIVO METODO PER LA RILEVAZIONE DI SOSTANZE INQUINANTI MEDIANTE UN VEICOLO PILOTATO DA REMOTO DA UN DISPOSITIVO APTICO DI COMANDO
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Oriented orthorhombic Lead Oxide film grown by vapour phase for X-ray detector applications
No full textSeveral materials are under investigations for flat panel x-ray detector applications. Among them, PbO shows
interesting properties, i.e. high sensitivity, large stopping power and high resistivity at room temperature.
However, the exploitation of PbO is limited by the difficulty to obtain good quality films constituted by a
single phase. In this paper, we describe a new approach for the vapour phase growth of orthorhombic PbO
films. The grown layers show a single phase, good crystallinity, and preferential orientation along the c axis.
Optical characterization evidenced the presence of a broad defect band. Gold contacted films showed very high
electrical resistivity and appreciable response to X-ray radiation
NO2 Gas Sensing Mechanism of ZnO Thin-Film Transducers: Physical Experiment and Theoretical Correlation Study
No full textIn this work, ZnO thin films were investigated to sense NO2, a gas exhausted by the most common combustion systems polluting the environment. To this end, ZnO thin films were grown by RF sputtering on properly designed and patterned substrates to allow the measurement of the electrical response of the material when exposed to different concentrations of the gas. X-ray diffraction was carried out to correlate the material's electrical response to the morphological and microstructural features of the sensing materials. Electrical conductivity measurements showed that the transducer fabricated in this work exhibits the optimal performance when heated at 200 °C, and the detection of 0.1 ppm concentration of NO2 was possible. Ab initio modeling allowed the understanding of the sensing mechanism driven by the competitive adsorption of NO2 and atmospheric oxygen mediated by heat. The combined theoretical and experimental study here reported provides insights into the sensing mechanism which will aid the optimization of ZnO transducer design for the quantitative measurement of NO2 exhausted by combustion systems which will be used, ultimately, for the optimized adjustment of combustion resulting into a reduced pollutants and greenhouse gases emission
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