Green route synthesized upconverting (NaYF4: Yb3+, Tm3+)nanophosphors and its photophysical and magnetic Properties

Abstract

Here we describe a green synthetic route for the development of paramagnetic, upconverting nanophosphors (UPCN_M) with enhanced luminescence using M.oleifera leaf extract. The current work demonstrates the influence of leaf extracton α→β phase transformation, size, morphology, magnetic behavior, and photothermal heat generation by upconverting nanophosphor under NIR illumination (wavelength~975 nm). The green route assisted upconverting nanophosphors synthesized in 2h, displayed better emission intensity as compared to nanophosphors prepared in15h, chemically, using EDTA (UPCN_EDTA).Further its (UCPN_M) suspension in DI water displayed photothermal heating rate, as high as 1.15 °C/min (ΔT= 11.5°C,Tmax= 40 °C) without incorporation of external NIR absorbing entity, physiologically relevant enough to carry out photothermal studies on biological subjects. At 2K and higher applied magentic field, the UPCN_M displayed super-paramagnetic behaviour with saturation magnetic moment as high as ~10.5 emu/g, although at room temprature (27 °C) intrinsically behaved as a paramagnetic magnet.