A Green Chemistry Approach for the Synthesis of Flower-like Ag-Doped MnO2 Nanostructures Probed by Surface-Enhanced Raman Spectroscopy

Novel hierarchical flower-like nanostructures of Ag-doped MnO2 have been obtained by facile wet chemical and photochemical routes. UV-visible absorption spectroscopy measurement reveals that doping of Ag nanoparticles in MnO2 nanostructures leads to a red shift of the absorption edge and reduces the optical band gap energy from 2.68 to 2.51 eV while compared with undoped MnO2. Raman study reveals that the band broadens and shifts toward higher wavenumbers as the MnO6 octahedron is contorted by Ag doping and thus the loss of translational symmetry activates otherwise Raman-forbidden oxygen vibrations. Finally, SERS activity upsurges from Ag-doped MnO2 with Rhodamine 6G and 2-aminothiophenol as probe molecules.