Terbium doped SnO2 nanoparticles as white emitters and SnO2:5Tb/Fe3O4 magnetic luminescent nanohybrids for hyperthermia application and biocompatibility with HeLa cancer cells

Abstract

SnO₂:5Tb (SnO₂ doped with 5 at% Tb³⁺) nanoparticles were synthesised by a polyol method and their luminescence properties at different annealing temperatures were studied. Characterization of nanomaterials was done by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). XRD studies indicate that the prepared nanoparticles were of tetragonal structures. Upon Tb³⁺ ion incorporation into SnO₂, Sn⁴⁺ changes to Sn²⁺ and, on annealing again at higher temperature, Sn²⁺ changes to Sn⁴⁺. The prepared nanoparticles were spherical in shape. Sn–O vibrations were found from the FTIR studies. In photoluminescence studies, the intensity of the emission peaks of Tb³⁺ ions increases with the increase of annealing temperature, and emission spectra lie in the region of white emission in the CIE diagram. CCT calculations show that the SnO₂:5Tb emission lies in cold white emission. Quantum yields up to 38% can be obtained for 900 °C annealed samples. SnO₂:5Tb nanoparticles were well incorporated into the PVA polymer and such a material incorporated into the polymer can be used for display devices. The SnO₂:5Tb/Fe₃O₄ nanohybrid was prepared and investigated for hyperthermia applications at different concentrations of the nanohybrid. This achieves a hyperthermia temperature (42 °C) under an AC magnetic field. The hybrid nanomaterial SnO₂:5Tb/Fe₃O₄ was found to exhibit biocompatibility with HeLa cells (human cervical cancer cells) at concentrations up to 74% for 100 μg L⁻¹. Also, this nanohybrid shows green emission and thus it will be helpful in tracing magnetic nanoparticles through optical imaging in vivo and in vitro application.