This study presents a sensitive calorimetric probe for sensing Co2+ ions based on surface amine-modified iron oxide-silica core-shell nanoparticles (APTES-Fe@SiO2 NPs) and the appearance of an additional plasmonic peak in the UV-vis spectra due to NP aggregation. This calorimetric strategy based on the component dependence of core-shell NPs offered a highly sensitive and selective detection method for Co2+ ions. This cost-effective colorimetric probe afforded rapid, naked-eye detection of trace Co2+ ions at concentrations as low as 0.08 mM. The amine moiety of APTES-Fe@SiO2 NPs readily formed the metal-amine configuration complex (lambda(980) peak) and induced the formation of Co NPs by self-seed generation (lambda(520), lambda(590), and lambda(630) peaks). Preliminary study data supported the promising practical applicability of the current method for the calorimetric detection of Co2+ ions in aqueous phase. (C) 2015 Elsevier B.V. All rights reserved.