Bioinspired Bi2S3 thin films on 4-mercaptobenzoic acid functionalized self-assembled monolayers

Self-assembled monolayers (SAMs) of 4-mercaptobenzoic acid (4-MBA) were used to induce the nucleation and growth of bismuth sulfide thin films from aqueous solution at low temperature. The effects of 4-MBA SAMs on the shape, structure, and crystallographic orientation of Bi2S3 crystals were investigated using scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, high-resolution transmission microscopy, and selected area electron diffraction. It was found that Bi2S3 crystals on the 4-MBA SAMs showed a rectangular parallelepiped shape and exhibited completely oriented crystalline domains with [001] directional preferred growth. However, the precipitated Bi2S3 films on the unfunctionalized surface consisted of quasispherical Bi2S3 polycrystalline particles. The mechanism of differences in the crystal properties can be explained by taking into account the liquid growth medium and the effect of 4-MBA SAMs.