Green and NIR sensitized luminescent nanophosphor: Preparation, characterization and application

Luminescent nanophosphor of Er, Yb: Gd2O3 has been synthesized by well known combustion synthesis. Along with strong UV–Vis upconversion emission, sensor for temperature and magnetic field, nano-heater etc., it can also be used as luminescent ink by dispersing the nanophosphor in aqueous polyvinyl alcohol solution. The stability of the ink has been found to depend strongly on the mixing process of the phosphor powder in the polymer solution. The X-ray diffraction results and TEM images with diffraction pattern show that the particles are in cubic phase of Gd2O3 with particles of average size <40 nm. SEM images show flaky structure which makes it suitable for dispersing in PVA and useful for luminescent ink purposes on NIR excitation. The FT-IR and the thermal analysis support the presence of PVA. Upconversion and downconversion luminescence has also been observed with 532 nm excitation and energy transfer mechanism has been explained. The NIR pumping gives strong UC emission bands in red and green regions extending up to extreme UV (240 nm) in this host.

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► Multicolor Er, Yb: Gd2O3 phosphor is synthesized and dispersed in PVA matrix.
► TEM and XRD shows particle size ranging between 30 and 40 nm and cubic phase of Gd2O3.
► UC and DC luminescence has also been observed with 532 nm excitation.
► UC bands of Er up to 240 nm region are reported in this host via four photon absorption.
► It can be used as luminescent marker and invisible security ink.