The synthesis and characterization of a platinum(II) terpyridine system tethered with a latent organic dye of rhodamine derivative as colorimetric and luminescent sensory moiety is reported to show selective Hg2+ ion sensing behavior. The interplay of aggregation/deaggregation behavior of the alkynylplatinum(II) terpyridine complex and the ring opening process of rhodamine derivative was investigated. The spectral change of aggregation near-infrared emission at 800 nm and rhodamine fluorescence at 585 nm provides a possible ratiometric luminescence measurement. Morphological studies from transmission electron microscopy and scanning electron microscopy images showing nanospherical structures confirmed the aggregation in the absence of He+ ion.