Rhodamine-based "turn-on" fluorescent chemodosimeter for Cu(II) on ultrathin platinum films as molecular switches

A novel self-assembled monolayer (SAM) of rhodamine derivative as turn-on and intrinsic fluorescent switches on ultrathin, optically transparent platinum films, was reported. A rhodamine-based chemodosimeter was designed and its platinum-film-immobalized rhodamine (PFIR), responsible for a Cu ²⁺-induced ring-opening process, to provide fluorescence changes in aqueous media. SAMs covalently bound to glass can be hampered by hydrolysis of the Si-O bonds in basic media, while ring-opening reaction in methanol could occur in the presence of large excess of Cu²⁺ ions. It is also found that at a high concentration of Cu²⁺, the colorimetric response of PFIR could be detected by the naked eye, as platinum films display optical transparency in the visible spectral region.