We report the optimization and usage of surfactantless, water dispersible Ag and Au-coated γ -Fe 2 O 3 nanoparticles for applications in surface-enhanced Raman scattering (SERS). These nanoparticles, with plasmonic as well as super paramagnetic properties exhibit Raman enhancement factors of the order of 10 6 (10 5 ) for Ag (Au) coating, which are on par with the conventional Ag and Au nanoparticles. Raman markers like 2-naphthalenethiol, rhodamine-B and rhodamine-6G have been adsorbed to these nanoparticles and tested for nonresonant SERS at low concentrations. Further, to confirm the robustness of Ag-coated nanoparticles, we have performed temperaturedependent SERS in the temperature range of 77-473 K. The adsorbed molecules exhibit stable SERS spectra except at temperatures >323 K, where the thermal desorption of test molecule (naphthalenethiol) were evident. The magnetic properties of these nanoparticles combined with SERS provide a wide range of applications.
A series of polycrystalline spinel type ferrites with composition LixMg0.5 Ni0.5−2xFe2+xO4, where x=0.00 to 0.25 in steps of 0.05, have been prepared by the conventional solid state reaction route. In this research, investigations have been carried out by the measurements of X-ray diffraction (XRD), Curie temperature, permeability, loss tangent, Q-factor, dielectric constant and ac electrical resistivity of the samples. Some measurements have been done at room temperature while other measurements have been done as a function of temperature and as a function of frequency in the range from 1 kHz to 500 kHz. Curie temperature, the real part of initial permeability (µi´), the loss tangent (tanδ), and the Q-factor have been found to be increase with the increase of Li-content of LixMg0.5 Ni0.5−2xFe2+xO4 ferrites. The frequency characteristic of dielectric constant and AC resistivity decreases with the increase in frequency and Li-content.
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