The impact of nanocrystals size on luminescent properties and thermometry capabilities of Cr, Nd doped nanophosphors

Transition metal d-f emission based thermometry has recently proven to be an order of magnitude more sensitive than thermometers based on conventional f-f transitions in rare-earth ions. Little is known however about the susceptibility of these materials to nanoscale parameters, such as size or surface-to-volume ratio. Here we study the impact of nanocrystallite size on luminescent properties as well thermometry capabilities of CrNd co-doped LiLaP4O12 phosphors. In particular, we show that absolute emission intensity decreases (similar to 0.81%/nm), emission band position blue shifts (Delta l similar to -0.066 nm(wave length)/nm(grain size)), temperature sensing range narrows (from 300 to 600K at 240 nm down to 300-420K at 20 nm), temperature sensitivity rises up (from 1%/K to similar to 5%/K) and temperature resolution drops (from similar to 0.3 degrees C down to 0.05 degrees C) gradually, when the size of NCs decreases from 240 down to 20 nm, respectively. As a consequence, proper design of host and dopants, enables finding optimal materials for many thermometry applications. (C) 2016 Elsevier B.V. All rights reserved.