5-Hydroxymethylfurfural modified rhodamine B dual-function derivative: Highly sensitive and selective optical detection of pH and Cu2+

• We developed an “off–on” bifunctional optical chemosensors for pH and Cu2+.
• The sensor showed highly sensitive fluorescent detection of pH in living cells.
• It also showed selective colorimetric recognition of Cu2+ in aqueous solution.
• The sensor was successfully applied to the detection of Cu2+ in real water samples.

A dual-function optical chemosensor (RBF) was designed and easily synthesized by condensation reaction of 5-Hydroxymethylfurfural and rhodamine B hydrazide. RBF exhibited highly sensitive, highly selective and quick response to acidic pH. The fluorescence intensity of RBF exhibited a more than 41-fold increase within the pH range from 7.50 to 3.73 with a pKa value of 5.02, which could be successfully applied to monitor intracellular pH in living PC12 cells and HeLa cells. Additionally, the spectroscopy of UV–Vis and EDTA-adding experiments indicated that RBF was a highly selective and reversible colorimetric chemosensor for Cu2+ in Tris–HCl (10 mM, pH = 7.2) aqueous buffer solution as well as other metal ions had no obvious interference. Moreover, RBF has been successfully applied to detect Cu2+ in real water samples.

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