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[Display omitted] • A simple and novel Schiff base that is selective for cupric ions. • NMR, FTIR, and ESI-MS spectroscopy methods were used to confirm the interaction of the probe with the analytes. • Probe R1 effective sense at colorimetric method was observed to be 2.74 × 10-7 M detection limits. • The analysis kit was created to track the use of cupric ions in real-time. A novel sulfonohydrazide Schiff base colorimetric probe 4-methylbenzenesulfonohydrazide (R1) has been designed and synthesized which shows sensing recognition of Cu2+ in CH 3 CN:H 2 O (7:3, v/v) semi-aqueous medium. The prepared probe R1 was characterized using spectroscopic methods, including FT-IR, 1H NMR, and HRMS spectrometry. R1 exhibits an excellent selectivity to Cu2+ over other examined metal ions with a prominent colorimetric performance from colorless (345 nm) to crimson yellow (420 nm) under daylight. UV–vis titration experiment in the presence of different molar fractions of Cu2+ was used to perform a Job's plot analysis. The results showed that the stoichiometric ratio of the complex formed by R1 and Cu2+ was 2:1. A paper strip pre-stained with R1 solution was further fabricated and it also showed excellent sensing ability toward Cu2+ with a detection limit as low as 2.74 × 10-7 M with the naked eye, which represents better portability and operation simplicity that is favourable for on-site analysis of Cu2+ in water. The sensing mechanism was further verified with HOMO–LUMO energy levels were calculated using experimental and theoretical studies (DFT/TD-DFT), which correlated with good agreement. [ABSTRACT FROM AUTHOR]

[Display omitted] • An easily designed R1 probe has been developed that demonstrates a rapid response to Cu2+ ions and possesses outstanding absorption and emission properties. • The ability to detect low levels of analytes with the lowest limit of detection (LOD) 3.23 × 10−9 M and quantification (LOQ) 10.79 × 10−9 M. • The R1 probe is capable of monitoring Cu2+ ions under physiological pH (2–10) conditions and exhibits specific selectivity towards cupric ion even in the presence of other competing ions. • The R1 probe was employed for the purpose of identifying the presence of Cu2+ ions in both the water and vegetable samples. In this work, we describe the synthesis of a Schiff base (R1) derived from furfural and 2-hydrazinobenzothiazole which displayed turn-off selective fluorescent chemo-sensing properties for Cu2+ ions in THF: HEPES buffer (9:1, v/v) solution. The molecular structure of the Schiff base (R1) was characterized by various spectroscopic techniques such as FTIR, 1H NMR, 13C NMR, and HRMS. Interestingly, R1 upon interaction with various metal cations displays highly selective colorimetric and fluorescent turn-off response to Cu2+ ions. The UV–Vis absorption study of the R1 with Cu2+ ions exhibits a noticeable color change from yellow to brown color with a redshift (∼60 nm). Upon the addition of Cu2+ ions emission quenching at 529 nm was observed in R1, and the limit of detection (LOD) and limit of quantification (LOQ) were found to be 3.23 × 10−9 M and 10.79 × 10−9 M. The mechanisms of probe R1 for sensing Cu2+ ions have been well demonstrated by Job's plot, Benesi-Hildebrand studies, and Density functional theory calculations (DFT). Owing to practical application, the Cu2+ ions were efficiently determined using a spike and recovery approach from real water and vegetable extract samples. Further, the developed R1 sensors were used for test strips application to detect the Cu2+ ions and achieved naked-eye detection. Therefore, these investigated results demonstrate that sensor R1 has great potential to detect Cu2+ ions in environmental analysis systems. [ABSTRACT FROM AUTHOR]