Growing Crystalline Chalcogenidoarsenates in Surfactants: From Zero-Dimensional Cluster to Three-Dimensional Framework

Although surfactants have been widely used to tailor
the size,
shape, and surface properties of nanocrystals and control the pore
size and phases of mesoporous frameworks, the use of surfactants as
reaction media to grow chalcogenide crystals is unprecedented. In
addition, compared with ionic liquids, surfactants are much cheaper
and can have multifunctional properties such as acidic, basic, neutral,
cationic, anionic, or even block. These features suggest that surfactants
could be promising reaction platforms for the development of novel
chalcogenide crystals. In this work, we used chalcogenidoarsenates
as a model system to demonstrate our strategy. By using three different
surfactants as reaction media, we obtained a series of novel thioarsenates
ranging from a zero-dimensional (0D) cluster to a three-dimensional
(3D) framework, namely, [NH4]8[Mn2As4S16] (1), [Mn­(NH3)6]­[Mn2As2S8(N2H4)2] (2), [enH]­[Cu3As2S5] (3), and [NH4]­[MnAs3S6] (4). The band gaps
(estimated from the steep absorption edges) were found to be 2.31
eV for 1 (0D), 2.46 eV for 2 (1D), 1.91
eV for 3 (2D), and 2.08 eV for 4 (3D). The
magnetic study of 4 indicated weak antiferromagnetic
behavior. Our strategy of growing crystalline materials in surfactants
could offer exciting opportunities for preparing novel crystalline
materials with diverse structures and interesting properties.