A novel rhodamine-based colorimetric and fluorometric probe for simultaneous detection of multi-metal ions

Effective and simultaneous detection of multi-metal ions has been achieved by a colorimetric and fluorometric probe (REHBA) synthesized from rhodamine hydrazide and polyhydroxyl aromatic aldehyde. REHBA can serve as a colorimetric detector for Cu²⁺ and Co²⁺, and a fluorometric probe for Pb²⁺. The colorless solution of REHBA changes to pink for Cu²⁺/Co²⁺ and shows a remarkable fluorescence for Pb²⁺. The further differentiation of Cu²⁺ and Co²⁺ depends on whether the colorimetric response of REHBA is reversible upon addition of ethylene diamine tetraacetic acid. The response is reversible for Cu²⁺, while it is not for Co²⁺. The spirolactam ring-opening in REHBA and the formation of REHBA-metal complexes with binding stoichiometric ratio of 1:1 are responsible for the UV-visible and fluorescence behaviors. REHBA shows excellent selectivity, anti-interference and good sensitivity. The limit of detection of Cu²⁺, Co²⁺ and Pb²⁺ is 0.11 μM, 0.88 μM and 0.73 μM, respectively. In addition, REHBA has been applied to recognize Pb²⁺ in living cells by fluorescence image and Cu²⁺, Co²⁺ and Pb²⁺ in real water samples, indicating that REHBA is a potential candidate for multi-metal-ions detection.