Synthesis and In Situ Application of a New Fluorescent Probe for Visual Detection of Copper(II) in Plant Roots

Abstract

A new rhodamine-based fluorescent probe (RDC, rhodamine-based derivative) was rationally designed and synthesized for the highly selective, sensitive, and quantitative detection of Cu2+. The probe demonstrated outstanding specificity toward Cu2+, even in the presence of competing metal ions (e.g., Al3+, Fe3+, Cr3+, Na+, and K+), exhibiting negligible interference and confirming its robust anti-interference capability. A spectroscopic analysis revealed that Cu2+ induced spirocyclic ring cleavage, resulting in a colorless-to-pink colorimetric transition and enhancement of the yellow–green fluorescence at 590 nm. Upon addition of Cu2+, the fluorescence spectrum showed a linear response in the concentration range of 0.4–20 μM, with a correlation coefficient (R2) of 0.9907 and the limit of detection (LOD) calculated to be 0.12 μM. Meanwhile, Job’s plot analysis verified that the binding stoichiometry between RDC and Cu2+ was 1:1. The probe exhibits rapid response kinetics ( maturation zone epidermis > xylem vessels > cortical cell walls. In conclusion, RDC is a well-characterized, high-performance tool with high accuracy, excellent selectivity, and superior sensitivity for plant Cu2+ studies, and this work opens new technical avenues for rhodamine-based probes in plant physiology, environmental toxicity monitoring, and rational design of phytoremediation strategies.

Code and data availability

This is a fluorescent probe chemistry paper; the only public supplement (MDPI S1) contains supplementary spectra figures (S1–S6), not plant-phenotyping datasets, root images, analysis code, or models. No qualifying paper-specific asset is available.

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