Effect of the type of acid used in the synthesis of titania–silica mixed oxides on their photocatalytic properties

Laser oxidative pyrolysis synthesis and annealing of TiO2 nanoparticles embedded in carbon–silica shells/matrix

“…The intense peak centered at 1095 cm −1 with his shoulder at 1227 cm −1 , found only for silica-containing powders was also reported at 1065 and 1200 cm −1 in [1] and attributed to Si O Si vibrations. The small peak visible in the same powders spectra centered around 940 cm −1 was considered an indication of the chemical connection between titania and silica, being reported and ascribed to Ti O Si vibrations [2,4,38]. Also, at 955 cm −1 the presence of Si OH stretching vibrations corresponding band was also reported in [1], whereas the same Si OH attributed peak was found at 921 cm −1 from SiO x films prepared by plasma CVD [40].…”

“…There are also many peaks that are common to all samples. The large peak at 3390-3420 cm −1 and the small peak at 1632 cm −1 can be also found in [4,38,39]. They were attributed to the stretching modes of O H bonds from the surface adsorbed water and to the bending vibrations of physisorbed and/or chemosorbed water, respectively.…”

“…8b. Due to the fact that pure SiO 2 phases do not exhibit absorption in the 200-500 nm domain [38], the absorption properties observed for our annealed powders are only due to titania phases and carbon. Yet, the amorphous silica on/near the titania surface interacting with carbonaceous layer can influence the photocatalytic properties for example by enhancing the hydrophylicity and the organic species adsorption.…”

Study of the characteristics and properties of the SiO2/TiO2/Nb2O5 material obtained by the sol–gel process

“…3 A), in the temperature variation to approximately 383 K, an endothermic event (exo down) is observed with a mass loss of 21%, related to water desorption. From 383 to 528 K (exothermic event, exo up), it was found a mass loss of approximately 8%, due to the dehydroxylation of the groups –SiOH, –TiOH or –NbOH in virtue of structural water loss 37 , 38 . Above the temperature of 528 K, there was a change in the line referring to DTA, which may indicate an event where there is a change in energy generating a mass loss of approximately 4% (endothermic event, exo down).…”

“…3 B), the mass losses are similar, totaling 29.7%. Up to 408 K a mass loss of 15.4% is observed (endothermic event, exo down), related to water desorption 37 , 38 . Between 408 and 523 K the mass loss is approximately 5% (exothermic event, exo up) and in the range of 523 K to 698 K the mass loss also corresponds to 5% (endothermic event, exo down) 38 , 39 .…”