Colorimetric sensing of Au3+ ions in aqueous media: A xanthene-based probe for rapid and visual detection

Ionic gold species play a pivotal role in various chemical and biological systems due to their unique properties. However, even trace amounts of Au³⁺ ions (as low as 200 μM) can pose significant toxicity risks to living organisms, underscoring the need for accurate and rapid detection methods. In this study, we present the design and characterization of a novel colorimetric sensor, TS-Xan, specifically developed for Au³⁺ ion detection. TS-Xan, a xanthene-derived probe, functions as a reversible sensor. Its molecular structure was characterized using nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS). The sensor exhibited excellent sensitivity toward Au³⁺ ions, inducing a distinct colorimetric shift from yellow to violet, visible to the naked eye in aqueous media. UV–vis absorption studies revealed the formation of a new absorption band at 570 nm, corresponding to the TS-Xan-Au³⁺ complex. HRMS analysis further elucidated the binding stoichiometry, confirming a 2:1 (TS-Xan:Au³⁺) complex formation. To enhance its practical applicability, TS-Xan-coated test strips were fabricated, demonstrating exceptional sensitivity and reliability for on-site Au³⁺ detection. This work introduces a promising and user-friendly approach for gold ion sensing, with potential applications in environmental monitoring, industrial waste analysis and bioanalytical fields.