A simple, sensitive, and selective colorimetric chemosensor for sequential determination of dual analytes, Ce³⁺, H₂PO₄⁻, and its applications in the logic gate construction and the system of keypad lock

Abstract

Sodium (E)‐3‐hydroxy‐4‐((2‐hydroxynaphthalen‐1‐yl)diazenyl)naphthalene‐1‐sulfonate (Calcon, CAL), is employed for the first time as a reversible colorimetric chemosensor to detect and measure Ce3+ and H2PO4− sequentially in the aqueous medium. The detection process has two steps. The interaction of CAL and Ce3+ in the first step with a noticeable color shift from purple to blue. Further, the reaction between CAL‐Ce3+ and H2PO4− shows a clear color return from blue back to initial purple similar to that for CAL. The UV–visible examination of this color return reveals that H2PO4− removes Ce3+ and restores CAL content. The results showed that CAL and CAL‐Ce3+ had a strong binding affinity and adequate detection limits for the Ce3+ and H2PO4−, respectively. For Ce3+, the linear range and detection limit are 1.20 × 10−6‐1.02 × 10−4 and 2.0 × 10−7molL−1, while for H2PO4−, they are 2.0 × 10−7‐8.7 × 10−6 and 3.0 × 10−8 molL−1. Finally, we measured these two ions in real samples using this methodology. Furthermore, the examination of the suggested receptor's logical behavior revealed that it can operate as a colorimetric chemosensor of the INHIBIT type, receiving chemical inputs and producing a UV–visible absorbance signal as the output. If Ce3+ and H2PO4− inputs are added in proper order, the receptor may also function as a molecular “keypad lock.”