A rhodamine B-based colorimetric chemosensor for sensitive and selective detection of Cu²⁺: Test strip analysis and density functional theory

We designed a rhodamine B-based colorimetric chemosensor BHSO ((Z)-3′,6′-bis(diethylamino)-2-(2-(((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)methylene)amino)ethyl)spiro[isoindoline-1,9′-xanthen]-3-one) for detecting Cu²⁺. In the presence of Cu²⁺, BHSO caused a colour variation from colourless to bright orange. The limit of detection for Cu²⁺ towards BHSO was 0.73 μM. The binding of BHSO to Cu²⁺ was analysed as a 1:1 ratio through a Job plot and electrospray ionisation mass spectrometry. BHSO can detect readily Cu²⁺ with a test strip by colorimetric variation. The detecting process of Cu²⁺ by BHSO was represented by ultraviolet-visible titration, electrospray ionisation mass spectrometry, proton nuclear magnetic resonance titration, Job plot and density functional theory calculations.