A reversible indole-based colorimetric chemosensor for Cu²⁺: implications for smartphone-integrated sensing, logic gate experiments, environmental and biological applications.
6 affiliations
- 1Department of Chemistry, Jashore University of Science and Technology Jashore 7408 Bangladesh [email protected] [email protected] [email protected] [email protected] [email protected] [email protected].
- 2Department of Chemical Engineering, Jashore University of Science and Technology Jashore 7408 Bangladesh [email protected].
- 3Department of Pharmacy, Jashore University of Science and Technology Jashore 7408 Bangladesh [email protected] [email protected].
- 4Faculty of Science, Agriculture & Engineering, Newcastle University Newcastle upon Tyne NE1 7RU UK [email protected].
- 5Department of Environmental Science and Technology, Jashore University of Science and Technology Jashore 7408 Bangladesh [email protected].
- 6Department of Applied Chemistry, Faculty of Science and Engineering, Saga University Honjo-machi 1 Saga 840-8502 Japan [email protected].
Abstract
The development of portable, cost-effective, and practical analytical platforms for rapid on-site detection of Cu²⁺ remains challenging. Herein, we have reported the novel one-pot synthesis of an indole-based sensor for Cu²⁺, namely (E)-N'-((1H-indol-3-yl)methylene)picolinohydrazide (MPH), which was characterized by FT-IR, ¹H-NMR, ¹³C-NMR, elemental analysis, HRMS, and single-crystal X-ray diffraction. The sensing performance of MPH toward various metal ions was evaluated using colorimetric analysis, UV-vis spectroscopy, cyclic voltammetry, and a smartphone-assisted RGB platform in MeOH/H₂O. MPH exhibited high selectivity for Cu²⁺ ions, producing a distinct color change from colorless to intense yellow (≤1 second). Job's plot analysis revealed the formation of a 2 : 1 (MPH : Cu²⁺) complex. The titration studies revealed a distinct isosbestic point at 308 nm, indicating a clean and well-defined interconversion between the free and complexed species. The binding mechanism was investigated using FT-IR, ¹H NMR, ESI-MS, FESEM, and was supported by DFT calculations. The UV-vis method achieved a Cu²⁺ detection limit of 4.48 × 10⁻⁶ M, surpassing EPA drinking water standards. The sensor also demonstrated excellent reversibility and recyclability with EDTA, while the RGB platform enabled real-time Cu²⁺ quantification with a detection limit of 5.5 × 10⁻⁶ M. Practical applicability was confirmed through logic-gate operations, paper strip method, antimicrobial studies, and Cu²⁺ determination in real environmental samples. These ultrafast responses, high sensitivity, multifunctional capabilities, reusability, and real-world applicability suggest MPH as a highly effective, economical, and field-ready sensor for practical Cu²⁺ monitoring in environmental and analytical conditions.
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BibTeX
@article{gim2026reversible,
title = {{A reversible indole-based colorimetric chemosensor for Cu²⁺: implications for smartphone-integrated sensing, logic gate experiments, environmental and biological applications.}},
author = {Joardar Gim and Dipa Debnath and Redika Sarmin Prieety and Miss Tasnim Jahan and Md Ruhul Amin and Md Sadman Hossain and Paul G Waddell and Kishor Mazumder and Md Sabbir Hossain and M Azizur R Khan and Takehiko Yamato and Zannatul Kowser},
journal = {RSC advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra07863j},
url = {https://europepmc.org/article/MED/42948676},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - A reversible indole-based colorimetric chemosensor for Cu²⁺: implications for smartphone-integrated sensing, logic gate experiments, environmental and biological applications.
AU - Joardar Gim
AU - Dipa Debnath
AU - Redika Sarmin Prieety
AU - Miss Tasnim Jahan
AU - Md Ruhul Amin
AU - Md Sadman Hossain
AU - Paul G Waddell
AU - Kishor Mazumder
AU - Md Sabbir Hossain
AU - M Azizur R Khan
AU - Takehiko Yamato
AU - Zannatul Kowser
PY - 2026
DA - 2026/10/27
JO - RSC advances
DO - 10.1039/d6ra07863j
UR - https://europepmc.org/article/MED/42948676
AB - The development of portable, cost-effective, and practical analytical platforms for rapid on-site detection of Cu²⁺ remains challenging. Herein, we have reported the novel one-pot synthesis of an indole-based sensor for Cu²⁺, namely (E)-N'-((1H-indol-3-yl)methylene)picolinohydrazide (MPH), which was characterized by FT-IR, ¹H-NMR, ¹³C-NMR, elemental analysis, HRMS, and single-crystal X-ray diffraction. The sensing performance of MPH toward various metal ions was evaluated using colorimetric analysis, UV-vis spectroscopy, cyclic voltammetry, and a smartphone-assisted RGB platform in MeOH/H₂O. MPH exhibited high selectivity for Cu²⁺ ions, producing a distinct color change from colorless to intense yellow (≤1 second). Job's plot analysis revealed the formation of a 2 : 1 (MPH : Cu²⁺) complex. The titration studies revealed a distinct isosbestic point at 308 nm, indicating a clean and well-defined interconversion between the free and complexed species. The binding mechanism was investigated using FT-IR, ¹H NMR, ESI-MS, FESEM, and was supported by DFT calculations. The UV-vis method achieved a Cu²⁺ detection limit of 4.48 × 10⁻⁶ M, surpassing EPA drinking water standards. The sensor also demonstrated excellent reversibility and recyclability with EDTA, while the RGB platform enabled real-time Cu²⁺ quantification with a detection limit of 5.5 × 10⁻⁶ M. Practical applicability was confirmed through logic-gate operations, paper strip method, antimicrobial studies, and Cu²⁺ determination in real environmental samples. These ultrafast responses, high sensitivity, multifunctional capabilities, reusability, and real-world applicability suggest MPH as a highly effective, economical, and field-ready sensor for practical Cu²⁺ monitoring in environmental and analytical conditions.
SN - 2046-2069
ER -