A New Spiropyran Hydrazone as an Unusual Colorimetric Sensor for Detection of Cu2+ and Cr3+ Based on Aggregation‐Induced Enhancement Effects in Aqueous Solvent Mixtures

Abstract

AbstractThough many improvements have been made on fluorescence probes for respective detection of Cu2+ and Cr3+, multiply detect of the ions by a simple colorimetric way in high water content solution sensors remains scarce. In this work, a novel spiropyran hydrazone, [(E)‐(2‐hydroxy‐1‐naphthyl)methylidene][(E)‐[1′,3′,3′‐trimethyl‐6‐(2‐methylprop −2‐yl)‐1′,3′‐dihydrospiro[chromene‐2,2′‐indole]‐8‐yl]methylidene]hydrazine (NA‐SP), which shows aggregation‐induced enhancement effects (AIEE) phenomena in EtOH (ethanol)/H2O and THF (tetrahydrofuran)/H2O media, has been developed. It can detect Cu2+ colorimetrically having a sensitivity of 105 nM in EtOH/H2O (40/60, v/v) with an unusual specific tandem‐response to Cr3+ at a detection limit of 151 nM in addition with a wide pH range of 4–10. Mechanism investigations by HRMS, 1H NMR and UV‐Vis spectroscopy have verified that the response to Cr3+ is based on the cooperative effect between NA‐SP and Cu2+, instead of the replacement of Cu2+ by Cr3+. Moreover, NA‐SP shows a robust AIEE‐caused recognition for Cu2+ in THF/H2O (20/80, v/v) with a detection limit of 16.5 nM. Real water tests indicate that the probe has potential detection application for Cu2+ in environmental situations. This contribution presents a new spiropyran sensor for the detection of Cu2+ and Cr3+ in aqueous solutions through an uncommonly colorimetric way.