Selective detection of toxic Au3+ using novel dicyano-[5]helicene-based fluorescence sensor: Applications in real samples and human neuroblastoma cells

Gold is a valuable noble metal having widespread applications across various fields. However, Au 3+ accumulation in the human body and the environment can pose serious health and ecological risks. Therefore, effective methods for Au 3+ detection must be developed. Herein, a fluorescence sensor was successfully synthesized, to the best of our knowledge, as the first dicyano-[5]helicene-based sensor ( MP ) for Au 3+ detection. Spectroscopic techniques and single-crystal X-ray analysis were used to confirm the molecular structure and photophysical properties of MP . The sensor exhibited a large Stokes shift of 111 nm and a high fluorescence quantum yield. Upon exposure to Au 3+ MP displayed a “turn-off” fluorescence response, which indicates its high selectivity toward Au 3+ over other competing metal ions along with excellent sensitivity. The detection limit of MP reached 4.2 ppb, which is lower than the guideline value for Au 3+ toxicity in freshwater environments. The sensing mechanism for Au 3+ detection was proposed to rely on the alkynophilicity of Au 3+ , activating the triple bond and inducing hydration of the alkyne moiety. This mechanism was supported by Fourier transform infrared spectroscopy, 1 H nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, and molecular modeling. This sensor demonstrated high potential for qualitative fluorometric assays of Au 3+ levels in diverse real samples, such as environmental water, drinking water, tap water, fertilizer solutions, cosmetic products, and human neuroblastoma cells. In addition, it could be applied for the quantitative detection of gold nanorods and further developed into a paper-based test strip for onsite Au 3+ screening. • •The sensor shows high sensitivity toward Au 3+ with low detection limit. • •The sensor can tolerate interferences from other competing ions. • •The sensing mechanism was thoroughly investigated using FTIR, 1 H NMR and HRMS. • •Applications in real samples and human neuroblastoma cells were accomplished. • •The sensor can be used for quantitatively detection of gold nanorod.