Size-modulation of functionalized Fe3O4: Nanoscopic customization to devise resolute piezoelectric nanocomposites
Magnetite (Fe3O4), an archetypical relaxor multiferroic material, transpires to possess fundamentally appealing multifaceted size-dependent properties. To appraise such a prototype spinel transition metal oxide (STMO); monodispersed and highly water-dispersible spherical magnetite nanoparticles (MNPs) with enormous variation in size (3.7 – 242.8 nm) are synthesized by a persuadable microwave-assisted and polyol-mediated solvothermal approach at controlled temperature and pressure, using idiosyncratic crystallite growth inhibitors. An exalted long-term colloidal stability in polar environment and Zeta potential insurgence conform the coordinative effect of carboxylate groups contriving the covalent surface functionalization; duly validated from FTIR spectra, TGA and XPS analysis. The optical band-gap (Eg) between crystal-field split-off bands, calculated from absorption spectra, increases gradually against size-contraction enfolding a broad UV-Vis range (1.59-4.92 eV). Red-shifting of asymmetric Raman peaks with smaller size and short-range electron-phonon coupling are explained from the modified phonon confinement model (MPCM); whereas ferrimagnetic nature rejigged by superparamagnetism is verified from Mössbauer analysis. These stoichiometric, non-toxic, polar and magnetic nanocrystals are not only ideal for biomedical applications, but also compliant with electroactive porous host-networks. Size-modulated MNPs are finally incorporated in poly(vinylidene floride) [PVDF] based polytype nanogenerators as an electret filler to reinforce piezoelectric performance (VOC~115.95 V, ISC~1.04 μA), accompanied by substantial electromagnetic interference shielding.