Preparation, characterization and application of soluble TiO2@SiO2 nanospheres by a simple modified sol–gel procedure

Suppression of TiO2 Photocatalytic Activity by Low-Temperature Pulsed CVD-Grown SnO2 Protective Layer

“…TiO 2 white pigments are widely used in many industrial fields, such as paints, pharmaceuticals, plastics, cosmetics, synthetic fibers, and papermaking, due to their attractive physicochemical properties. − However, the strong photocatalytic activity of TiO 2 particles can cause degradation of the surrounding polymer molecules in paint films, especially when they are exposed to sunlight or ultraviolet radiation, resulting in discoloration and easy removal of the paint . In order to suppress the photocatalytic activity of TiO 2 , commercial TiO 2 pigments are usually coated with an inert material (Table S1), such as SiO 2 , − Al 2 O 3 , − ZrO 2 , , NiO, CoO, CeO 2, , and a SiO 2 –Al 2 O 3 double layer. − However, commercial coating operations are normally conducted by the wet chemical deposition technique; − , the uniformity and thickness of the coatings are highly dependent on the operating conditions, such as temperature, pH, and deposition rate, which make it difficult to obtain a uniform ultrathin film …”

“…5 In order to suppress the photocatalytic activity of TiO 2 , commercial TiO 2 pigments are usually coated with an inert material (Table S1), such as SiO 2 , 6−17 Al 2 O 3 , 18−23 ZrO 2 , 24,25 NiO, CoO, CeO 2, 26,27 and a SiO 2 −Al 2 O 3 double layer. 28−30 However, commercial coating operations are normally conducted by the wet chemical deposition technique; [6][7][8][9][10]20 the uniformity and thickness of the coatings are highly dependent on the operating conditions, such as temperature, pH, and deposition rate, which make it difficult to obtain a uniform ultrathin film. 31 To overcome these limitations, chemical vapor deposition (CVD), [12][13][14]16 atomic layer deposition (ALD), 11,21,22,31 and molecular layer deposition (MLD) 32 methods are attractive alternatives.…”

Suppressing the Photocatalytic Activity of Titania by Precisely Controlled Silica Coating

“…The surface modification of semiconductor photocatalysts has been done to modify the activity of the photocatalysts, to accelerate the reaction by the modification of the affinity to reactants, to enhance the photon absorption ability and prevent the fouling, to impart molecular recognition by molecular sieving effects of porous silica, and to suppress the reactivity by covering the surface to block the reactant access. − When TiO 2 is used as UV absorbing pigment in paints, chalking and color fading of paints are caused by the photocatalytic activity of TiO 2 even by the sunlight. , The formation of reactive oxygen species, which is harmful to human skin, by a UV absorber (TiO 2 ) is pointed out for the sunscreen application. − Thus, the photocatalytic activity of TiO 2 is required to be suppressed for such applications as paints and cosmetics. Heteroelement doping − and coating of TiO 2 particles with aluminum oxide, tin oxide, and silicon dioxide have been reported for suppressing the photocatalytic activity of TiO 2 particles. − To suppress the photocatalytic activity more precisely, it is important to develop efficient coating protocols for uniform and perfect coverage to completely block the particle surface from accessing of the reactants. In this study, coating of a commercially available TiO 2 particle (with the particle size of 22 nm) with silica was examined to obtain TiO 2 /silica core/shell particles with varied nanostructures and the thickness of the shell as a possible UV-shielding white pigment.…”