Influence of particle size on the phase behavior associated with the thermal spin transition of the Prussian blue analogue K0.4Co1.3[Fe(CN)6]•4.4H2O

The Prussian blue analogue K0.4Co1.3[Fe(CN)(6)]center dot nH(2)O has previously been shown to exhibit three distinct phases at low temperature. In addition to the well-studied high-temperature 'high spin' and low-temperature low spin' phases, with unit cells of similar to 10.3 and similar to 9.95 angstrom, respectively, an intermediate phase with unit cell a = 10.09 angstrom was recently reported, although it existed as a minority constituent in a mixed-phase material. Herein we report the synthesis of 130 nm K0.4Co1.3[Fe(CH)(6)]center dot 4.4H(2)O particles that form solely the intermediate phase at temperatures below the normal charge transfer induced spin transition. Compared with those formed from a bulk synthesis, the nanosized particles are shown to have the same chemical composition at high temperature, but they undergo different structural transitions with thermal cycling. (C) 2013 Elsevier Ltd. All rights reserved.