Propargylic-linked [5]helicene derivative for selective Au³⁺ detection in near-perfect aqueous media with applications in diverse real samples, paper test strips, and human cells

Abstract

Gold is classified as a heavy metal, and its ion (Au3+) can manifest adverse impacts on ecological and human health. Thus, an effective method for Au3+ detection is highly required. In this work, a new [5]helicene-based fluorescence sensor (M202P) was synthesized and applied for Au3+ monitoring in near-perfect aqueous media. M202P rapidly detected Au3+ through a fluorescence quenching response and furnished a large Stokes shift of 157 nm. The Au3+ sensing ability of M202P allowed it to withstand interference from other metal ions, with a detection limit for Au3+ of 8.0 ppb. The mechanism underlying its Au3+ detection was the coordination of Au3+ with the alkyne and carbonyl oxygen, leading to the later hydration of alkynyl moiety, as thoroughly proven by FTIR, 1H NMR, 13C NMR, and HRMS, with the stoichiometric ratio of 1:1 according to Job's plot. In addition, M202P can be used for the quantitative analysis and qualitative fluorescence assay of Au3+ levels in environmental waters and fertilizer solutions. This sensor also demonstrated high potential as a fluorescence tracking agent in human cells and was utilized in fabricating a paper test strip.