Tunable Band-Edge Magneto-Optical Response of Plasmonic Sn-Doped CdO Nanoparticles for Magnetoplasmonic Sensing

We report the successful synthesis of tin-doped cadmium oxide (CdO) nanoparticles via solution-phase thermal decomposition of Cd(acac) 2 in the presence of a Sn(IV) compound at elevated temperatures. The obtained Sn-doped CdO nanoparticles have tunable plasmonic features with the peak position in the near-IR/mid-IR region, which is dependent on the nominal Sn doping level, ranging between 2.5 and 10%. Interestingly, in addition to the near-IR plasmon-based magnetic circular dichroism (MCD) signals, rather strong excitonic MCD responses are found in the visible band-edge region, displaying a clear Burstein–Moss shift as a function of the Sn-doping level. Correlating the optical absorption spectra with the excitonic MCD leads to the effective mass of electron ( m *) of 0.45–0.5 m 0 . The m * value can independently be estimated by the cyclotron shift energy of the near-IR magnetoplasmonic MCD responses, providing also the m * value of 0.45 m 0 . The agreement of these m * values determined by two different analytical procedures proves that the band-edge MCD responses are brought about by nonresonant cyclotron-carrier-induced exciton polarization in plasmonic Sn-doped CdO nanoparticles.