Photoluminescence emission from nanostructured porous preparations of CdS-ZnTiO3 assembled nanoparticles.

This study reports the structural and optical properties of CdS/ZnTiO3 nanocomposites prepared using a chemical bath and different titanate concentrations. Commercial ZnTiO3 nanoparticles were introduced into a chemical bath that had been used to produce CdS semiconductor nanoparticles (NPs). Here, the growing CdS crystallites precipitated onto the suspended zinc titanate NPs. X-ray diffraction patterns revealed that samples of CdS/ZnTiO3 nanopowders were made of cubic ZnTiO3 and hexagonal CdS wurtzite. The morphology of the particles was studied using transmission electron microscopy and scanning electron microscopy images. These images demonstrated the different characteristics of the CdS/ZnTiO3 nanocomposites and their dependence on titanate concentration when placed into the CdS-growing solution. Photoluminescence spectra showed three main emission bands for the electron transitions in the CdS/ZnTiO3 composite. This composite produced three photoluminescence bands, the intensities of which depended on composite shape, which in turn depended on the relative concentrations of CdS and ZnTiO3 .

Chemical acetylation of nixtamalized maize flour and structural, rheological and physicochemical properties of flour, dough and tortillas.

Nixtamalized maize tortilla is a basic food for the Mexican population. It has high energy due to high starch, which may be modified to decrease its bioavailability and to produce changes in the characteristics of flours. For this research, nixtamalized maize flour was prepared and subjected to an acetylation chemical process, with and without prior hydrolysis. Raw maize flour, traditionally nixtamalized maize flour, acetylated-nixtamalized maize flour (AF) and acetylated-hydrolyzed nixtamalized maize flour (AHF) were prepared and evaluated. These flours were used for dough and tortilla preparation and analyzed for degree of substitution (DS), physicochemical properties, structure, thermal, rheological, morphological and texture properties. FTIR spectra and DS showed the presence of acetyl groups. AHF showed the highest value for water absorption index. The resistant starch increased 0.27 and 0.42% for AF and AHF samples. The gelatinization enthalpy (∆Hg) for AF was greater than other flours. AF tortillas showed better characteristics than the traditional ones and their consumption was recommended since showed better RS.

Gaseous benzene degradation by photocatalysis using ZnO + Zn2TiO4 thin films obtained by sol-gel process.

The benzene pollutant in gaseous phase was successfully degraded by using ZnO + Zn2TiO4 multicomponent oxide thin films as photocatalysts. The films were obtained with different Ti/Zn ratios (0, 0.20, 0.40, 0.45, 0.50, 0.67, 0.84, and 1) by the sol-gel route. The initial level of benzene concentration was 110 ± 10 ppm. The process was carried out under different conditions of relative humidity (RH): 25, 50, and 80 % in a batch-type reactor, at room temperature. The results show benzene degradation near to 95 % at t = 240 min, where the multicomponent oxide semiconductor has a Ti/Zn ratio of 0.67. Meanwhile, with the TiO2 thin films, only a degradation of 70 % was reached at the same measurement conditions. This synergistic effect on the photocatalytic activity is a result of the coupling of both semiconductor oxides. An adverse effect on the photocatalytic activity was observed as the relative humidity increases.