Bismuth molybdates model catalysts with controlled crystallinities spin-coated on Si (1 0 0)

The possibility of spin-coating crystalline multi-element oxide model catalysts using citrate complexes of Bi3+ and Mo6+ solutions was studied. The characterization of obtained thin films was performed by XRD, Raman spectroscopy, SEM and XPS. XRD and confocal Raman data indicated that Bi2O3–MoO3 mixed systems behaved as dictated by the composition of the starting solutions, and pure α-Bi2Mo3O12, β-Bi2Mo2O9, and γ-Bi2MoO6 phases were obtained without any heterogeneity. XPS confirmed that Bi:Mo ratios at the surface of the films never differed from those in the bulk, namely that of the starting co-solutions. SEM revealed that the thickness of the films could be tuned in the range 40–140 nm via adjustment of the spin-rate (2, 3, or 5 krpm) and the concentration of the precursors solution (0.24 or 0.48 M in Mo), without any disturbance of crystallinity, the Bi:Mo ratio or the homogeneity of the films. Performed studies suggested that spin-coating of mixed citrate complexes appears as a versatile and easy route to prepare homogenous films of multi-element transition metal oxides with controlled formulation and crystalline structure.