Biomimetic syntheses of pure or doped metal hydroxide nitrate thin films by a dual-template approach

Compact large area Zn5(OH)8(NO3)2$2H2O, Co5(OH)8(NO3)2$2H2O and Co-doped Zn5(OH)8(NO3)2$2H2O thin films with uniform surface morphology and good orientation were synthesized by an unusual dual-template biomimetic approach. In such a biomimetic system, a bovine serum albumin Langmuir monolayer was used as one organic matrix template, whereas the vapor– liquid interface generated by the vapor diffusion of catalyst (ammonia) served as the other nucleation template providing kinetic control. The crystallinity, morphology and overall chemical composition of thin films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The formation process of the Zn5(OH)8(NO3)2$2H2O films was discussed in detail. Compared with the method with only organic template, the synergetic effect of the dual template plays an important role in the formation of thin films. The method developed here provides a novel route for growing large area and well-oriented thin films at room temperature.