Novel nitrogen plasma doping on CdS/GO compounds and their photocatalytic assessment.

Nitrogen-doping of cadmium sulfide nanostructured compounds was carried out under a nitrogen plasma source to produce CdS-N compounds. Once prepared, it was supported on graphene oxide sheets for producing CdS-N/GO photocatalysts, which were tested in the degradation of lignin and methylene blue (MB) molecules. Photocatalytic reactions were carried out under UV and visible (vis) energy irradiation. To provide insight on the catalytic behavior the CdS, CdS-N, GO, and CdS-N/GO compounds were characterized using different techniques including x-ray diffraction, scanning electron microscopy, Raman, and UV-vis diffuse reflectance spectroscopy. X-ray photoelectron spectroscopy allowed determining the chemical composition in samples. It was observed an outstanding performance in photocatalytic activity tests, attributed to the extended response towards the visible light regime, and the synergistic effect between CdS-N and GO particles. The catalytic activity tests, reveal that the CdS-N/GO compound achieved over 90% lignin degradation and 100% of MB degradation. In addition, a remarkable performance is observed in the CdS-N/GO compound which exhibited stability after performing several reaction cycles.

Controlled Phase Changes of Titania Using Nitrogen Plasma.

In this work, the development of a new crystallization technique is reported, using nitrogen plasma (AC) to obtain nanostructured anatase and rutile from amorphous titanium oxide (TiO2). This methodology increases throughput and minimizes thermal effects. Nanostructured amorphous TiO2 was obtained by the sol-gel method and subsequently subjected to AC treatment, at a controlled pressure, applying different powers and treatment times in order to obtain phase changes. The obtained samples were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The results show the crystallization in parallel with anatase and rutile phases with a proportion that is directly related to the applied power in the plasma and the treatment time. This technique allows us to obtain smaller crystals in comparison with those of classic thermal methodologies. It is also demonstrated that the application of plasma represents a novel and innovative method to obtain phase polymorphic changes in titanium oxide without needing to apply prolonged heat treatments at high temperatures and can therefore be taken into consideration as a technique with low energy costs, in comparison with conventional heat treatments.