Structural characterization and plasmonic properties of manganese oxide-coated gold nanorods

•Au nanorods coverage by manganese oxide ultrathin films resulted in blue-shift of the plasmonic band for thin layers, tendency reversed for thicker layers.•The unexpected behavior was explained by the decrease in local refractive index by removal of CTAB from the nanorods by the ultrathin oxide layer.•Cyclic voltammetry of the AuNR@MnO2 material showed no detectable pinholes.•The hybrid material presents presented SEF enhancement factors for the dye IR-820 excited at 785 nm, peaking at oxide thickness around 5 nm.•The SERS performance of the same IR-820 dye excited at 633 nm decreased as the MnO2 oxide layer thickened but was observable even at thickness around 10 nm.