Correction: One-Step Synthesis, Structure, and Band Gap Properties of SnO2 Nanoparticles Made by a Low Temperature Nonaqueous Sol–Gel Technique

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One-Step Synthesis, Structure, and Band Gap Properties of SnO2 Nanoparticles Made by a Low Temperature Nonaqueous Sol–Gel Technique

American Chemical Society. Because of its electrically conducting properties combined with excellent thermal stability and transparency throughout the visible spectrum, tin oxide (SnO2) is extremely attractive as a transparent conducting material for applications in low-emission window coatings and solar cells, as well as in lithium-ion batteries and gas sensors. It is also an important catalyst and catalyst support for oxidation reactions. Here, we describe a novel nonaqueous sol-gel synthesis approach to produce tin oxide nanoparticles (NPs) with a low NP size dispersion. The success of this method lies in the nonhydrolytic pathway that involves the reaction between tin chloride and an oxygen donor, 1-hexanol, without the need for a surfactant or subsequent thermal treatment. This one-pot procedure is carried out at relatively low temperatures in the 160-260 °C range, compatible with coating processes on flexible plastic supports. The NP size distribution, shape, and dislocation density were studied by powder X-ray powder diffraction analyzed using the method of whole powder pattern modeling, as well as high-resolution transmission electron microscopy. The SnO2NPs were determined to have particle sizes between 3.4 and 7.7 nm. The reaction products were characterized using liquid-state13C and1H nuclear magnetic resonance (NMR) that confirmed the formation of dihexyl ether and 1-chlorohexane. The NPs were studied by a combination of13C,1H, and119Sn solid-state NMR as well as Fourier transform infrared (FTIR) and Raman spectroscopy. The13C SSNMR, FTIR, and Raman data showed the presence of organic species derived from the 1-hexanol reactant remaining within the samples. The optical absorption, studied using UV-visible spectroscopy, indicated that the band gap (Eg) shifted systematically to lower energy with decreasing NP sizes. This unusual result could be due to mechanical strains present within the smallest NPs perhaps associated with the organic ligands decorating the NP surface. As the size increased, we observed a correlation with an increased density of screw dislocations present within the NPs that could indicate relaxation of the stress. We suggest that this could provide a useful method for band gap control within SnO2NPs in the absence of chemical dopants

Processing clinker from wastes: A new raw material source for a global change

The final destination of the wastes generated in the manufacture of pulp paper is one of the growing concerns in this sector since the European regulations are becoming stricter in regard to their landfill. So it is urgent to seek ways for their valorization through incorporation in other product as, although not usually dangerous, the quantities generated are substantial. In this work the residues used were: (i) a calcareous sludge generated in the chemical recovery circuit of the production process; (ii) a biological sludge generated in the secondary wastewater treatment step and (iii) a fly ash from the combustion of biomass in the cogeneration operation. The first stage of was the waste characterization and then different blends were prepared and submitted to distinct firing cycles to obtain Portland clinker, the main component of the ordinary cement. Using only wastes in adjusted proportions and a tuned firing cycle, it was possible to obtain ecological Portland clinker. Moreover, it was possible to reduce, by about 50 C, the firing temperature in relation to the value used in cement industry, which results in economical and procedural benefits. © (2016) Trans Tech Publications

Unexplored alternative use of calcareous sludge from the paper-pulp industry in green geopolymer construction materials

Calcareous sludge is an alkaline waste produced by the paper pulp industry that is commonly disposed of in land-fill. However, recent studies and the European regulations discourage such practice. This work investigates an alternative and innovative way to recycle and reuse this waste, as filler, in the production of green geopolymeric mortars intended for applications in construction. This is the first time that this calcareous sludge is used to produce novel waste-based materials, in both construction and geopolymer technology. The novel alkali-activated mortar also uses biomass fly ash \u2013 another slightly investigated waste stream \u2013 to substitute the metakaolin (70 wt% substitution) and the manufacture process is performed at ambient conditions. All of that reduces the overall process footprint. The implemented mix design is aimed at maximising the waste incorporation and improving the material properties, such as workability and mechanical performance. The main results demonstrate that 10 wt% of calcareous sludge can be efficaciously used as filler in the geopolymeric mortars, generating up to 30% improvement in the mechanical resistance. This alternative use of such wastes will contribute to increase the sustainability of the novel construction materials also granting environmental advantages and a financial surplus for the industry