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 MnO 2 have been obtained by facile wet chemical and photochemical routes. UV−visible absorption spectroscopy measurement reveals that doping of Ag nanoparticles in MnO 2 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 MnO 2 . Raman study reveals that the band broadens and shifts toward higher wavenumbers as the MnO 6 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 MnO 2 with Rhodamine 6G and 2-aminothiophenol as probe molecules.