Preparation of ultra long α-MnO2 and Ag@MnO2 nanoparticles by seedless approach and their photocatalytic performance

The reaction between aqueous MnO4−, cysteine, and Ag + ions constitutes a new seedless arrangement for the production of α-MnO2 and Ag@MnO2 bimetallic nanocomposites at room temperature. UV-visible absorption spectroscopy measurement reveals that presence of Ag+ ions in an aqueous solution of MnO4− and cysteine changes the entire shape of the α-MnO2 visible spectrum, and leads to a formation of broad band at ca. 425 nm. Thus-prepared nanomaterials were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDX), Raman spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. For the degradation of methyl orange and congo red, nanomaterials were used as the photocatalyst. The results show almost complete degradation (ca. 99%) of congo red in ca. 25 min. The α-MnO2 nanorods possess high photo degradation efficiency toward congo red in comparison to methyl orange.