A photochemical route in the synthesis and characterization of La2Ti2O7 and La2Ti2O7/AgO films and its evaluation in Congo red degradation and as antibacterial control to Staphylococcus aureus.

In this article, we propose a simple photochemical method to synthesize pure La2Ti2O7 films and La2Ti2O7 films doped with silver at 1.0, 3.0, and 5.0 mol%. After annealing the photo-deposited films at 900 °C, XRD, SEM, and XPS analyses showed the formation of a monoclinic La2Ti2O7 phase and the presence of Ag and AgO in doped samples. Photocatalytic tests for Congo red degradation demonstrated that pure La2Ti2O7 achieved 25.4% degradation, while doped samples reached a maximum of 92.7% degradation. Moreover, increasing silver doping on La2Ti2O7 films significantly reduced the growth of Staphylococcus aureus, indicating potential antibacterial properties. The enhanced photoactivity was attributed to the formation of a type I heterojunction between La2Ti2O7 and AgO, and a degradation mechanism was proposed based on Congo red degradation.

Shape, Microstructure, and Chemical Composition of Pearls from the Freshwater Clam Diplodon chilensis Native to South America.

The capability to produce pearls is widespread in the phylum Mollusca, including bivalves of the superfamily Unionoidea. Here, we identified and characterized natural pearls formed by Diplodon chilensis, a freshwater clam native to southern South America, using samples obtained from two lakes located in the Chilean Patagonia. Pearls were studied using light and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Naturally formed pearls were found in both male and female D. chilensis specimens. Pearls are produced in different shapes, including spherical, ellipsoidal, buttoned, and bumpy, ranging in size from 200 µm to 1.9 mm. The internal microstructure is composed of irregular polygonal tablets, about 0.40 to 0.55 µm in thickness. EDX analysis showed that pearls are composed of calcium carbonate. FTIR and Raman spectra recorded several peaks attributable to the aragonite in pearls of this species, as has been shown in other mollusks. In addition to these results, pearls of different colors are illustrated.

Preliminary study of the photodegradation of dyes using amorphous films of ZnO-CuO obtained by photochemical deposition in solid phase.

Here, we propose an original method of photochemical deposition for the synthesis of metal oxides from coordination complexes sensitive to UV light. The method consists of the synthesis of zinc oxide amorphous films doped with different concentrations of copper oxide followed by annealing at 600 °C. The photo-reactivity of the samples was evaluated by the decrease of the FT-IR spectroscopy bands. The films were analyzed by scanning electron microscopy (SEM-EDX) and X-ray diffraction (XRD) to study their morphology and structures, respectively. The results show an amorphous characteristic in the photo-deposits. The optical properties show a gradual decrease of both the optical band gap and the luminescent emissions of the ZnO photo-deposits when CuO doping increases. Both properties allow a shift in absorption towards the visible and a decrease in the rate of recombination of charge carriers. The photocatalytic activity was analyzed using methyl orange and methylene blue as pollutants under a lamp that emulates solar energy. The results show that the photocatalytic activity is favored by the insertion of CuO; 46.6 and 93.0% efficiency in the photodegradation of methyl orange and methylene blue, respectively, were reached at 1.0 mol % of CuO with respect to pure ZnO. These differences in degradation efficiency respond to the chemical stability of the dyes. Finally, the use of appropriate scavengers suggests an oxidative route in the dye degradation mechanism.