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Article

Harnessing Excited-State Iminium Form in 1,5-Diaminonaphthalene for Rapid Water Detection in Organic Solvents

Institute of Chemistry, University of Miskolc, Miskolc-Egyetemváros, 3515 Miskolc, Hungary
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Author to whom correspondence should be addressed.
Photochem 2025, 5(3), 22; https://doi.org/10.3390/photochem5030022
Submission received: 14 July 2025 / Revised: 2 August 2025 / Accepted: 11 August 2025 / Published: 15 August 2025

Abstract

Accurate detection of water in organic solvents is essential for various industrial and analytical applications. In this study, we present a simple, rapid, and sensitive fluorescence-based method for water quantification using 1,5-diaminonaphthalene (1,5-DAN) as a solvatochromic probe. This method exploits the excited-state intramolecular charge transfer (ICT) behavior of 1,5-DAN, which undergoes a symmetry-breaking transition in the presence of protic solvents such as water, leading to a distinct redshift in its emission spectrum and a change from a structured double-band to a single ICT band. We demonstrate that, in solvents like acetonitrile and tetrahydrofuran, the emission maxima of 1,5-DAN correlate linearly with water content up to 100%, while ratiometric analysis of peak intensities allows for sensitive detection in low concentration ranges. This method achieved limits of detection as low as 0.08% (v/v) in MeCN, with high reproducibility and minimal sample preparation. Application to a real MeCN–water azeotrope confirms the method’s accuracy, matching classical refractometric measurements. Our findings highlight the potential of 1,5-DAN as a low-cost, efficient, and non-destructive fluorescent sensor for monitoring moisture in organic solvents, offering a practical alternative to conventional methods such as Karl Fischer titration for both bulk and trace water analysis.
Keywords: water detection; solvent; diaminonaphthalene; ratiometric; fluorescence water detection; solvent; diaminonaphthalene; ratiometric; fluorescence

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MDPI and ACS Style

Kopcsik, E.; Kun, P.; Nagy, M. Harnessing Excited-State Iminium Form in 1,5-Diaminonaphthalene for Rapid Water Detection in Organic Solvents. Photochem 2025, 5, 22. https://doi.org/10.3390/photochem5030022

AMA Style

Kopcsik E, Kun P, Nagy M. Harnessing Excited-State Iminium Form in 1,5-Diaminonaphthalene for Rapid Water Detection in Organic Solvents. Photochem. 2025; 5(3):22. https://doi.org/10.3390/photochem5030022

Chicago/Turabian Style

Kopcsik, Erika, Péter Kun, and Miklós Nagy. 2025. "Harnessing Excited-State Iminium Form in 1,5-Diaminonaphthalene for Rapid Water Detection in Organic Solvents" Photochem 5, no. 3: 22. https://doi.org/10.3390/photochem5030022

APA Style

Kopcsik, E., Kun, P., & Nagy, M. (2025). Harnessing Excited-State Iminium Form in 1,5-Diaminonaphthalene for Rapid Water Detection in Organic Solvents. Photochem, 5(3), 22. https://doi.org/10.3390/photochem5030022

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