Investigation of photocatalytic behavior of l-aspartic acid stabilized Zn(1−x)MnxS solid solutions on methylene blue

• Synthesis of l-aspartic acid passivated Zn(1−x)MnxS solid solutions is reported for the first time.
• Presence of hydrophilic surface on catalyst enhances the possibility of dye adsorption and photocatalytic activity of catalyst.
• Study of dopant concentration on photocatalytic activity of Zn(1−x)MnxS solid solutions.

Water dispersible Zn(1−x)MnxS solid solution photocatalysts stabilized with l-aspartic acid were synthesized by coprecipitation. Their photocatalytic activity was evaluated using methylene blue as a model pollutant. X-ray diffraction and Raman spectroscopy indicated the catalysts had a cubic crystal structure. The gradual increase in zinc sulphide (ZnS) lattice constant with increasing Mn2+ dopant concentration was due to the high ionic radius of Mn2+. Raman spectra exhibited two peaks at 260 and 345 cm−1. Ultraviolet–visible absorption spectra of the catalysts exhibited a strong excitonic peak at 270 nm, which was blue shifted compared with that of bulk ZnS (340 nm). This was attributed to quantum confinement and coupling effects. The hydrophilic l-aspartic acid on the photocatalyst surface had a positive effect on photocatalytic activity. The effects of dye and dopant concentrations on photocatalytic activity were investigated.

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