The TiO(2).[Y(2)O(3)](x) (x = 0.1-0.4) nanocomposites (NCs) with an average particle size of 74 nm were prepared by the method of chemical co-precipitation followed by hydrolysis (CPH). Their visible light photocatalytic activity was investigated for the degradation of congo red (CR) dye. All NCs showed improved degradation as compared to the polycrystalline samples of similar compositions prepared by the solid-state reaction (SSR) route (average particle size of a few micrometers), as well as to the pure TiO(2). The better photocatalytic activity of the NCs was attributed to their smaller particle size. Another comparison of the results with those obtained with Zn(2+)/Fe(3+) ions co-doped TiO(2) NCs, under similar experimental conditions, revealed that in the Y(3+)-doped NCs, particle size might not be the only factor responsible for the improved photocatalytic properties. It was concluded that the Y(3+) ion-mediated suppression of the unwanted e(-)/h(+) recombination could be the possible factor leading to additional enhancement.

x (x = 0⋅0-0⋅5) nanocomposites (NCs) with an average particle size of 72⋅4 nm were synthesized by the method of co-precipitation/hydrolysis (CPH). For the comparison of particle-size dependent effects, a set of polycrystalline samples with similar compositions was also prepared by solid state reaction (SSR) route. Average particle size for SSR prepared samples was about 3⋅0 μm. All the samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer, Raman spectroscopy and Fourier transform infra-red (FTIR) spectroscopy. Their visible light photocatalytic activity was tested for the degradation of Congo Red dye. Maximum photodegradation was observed for the NC with x = 0⋅1 synthesized by CPH (particle size, 71 nm). Similar composition prepared by SSR method (particle size, 6⋅19 μm) showed lower photoactivity in comparison even with that observed for pure TiO 2 (particle size, 4⋅03 μm). It was, therefore, concluded that enhanced photodegradation is directly related to the reduced particle size of the composites, which implies that photosensitization is the process primarily involved. Although, doping of TiO 2 with ZnFe 2 O 4 does extend the cut-off wavelength towards visible parts of the spectrum, its contribution in the enhancement is not as significant as that due to the photosensitization.

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