Single system bi-functional inorganic-organic hybrid nanocomposites, PB@SiO2@BTC@Ln (PB = Prussian blue, BTC = benzene tricarboxylate; Ln = Tb(III)/Sm(III)) having a PB magnetic core and a luminescent lanthanide probe, show superparamagnetic behavior and significant enhancement in luminescence intensities. © 2008 The Royal Society of Chemistry.