A three-photon probe for highly selective and sensitive detection of Ag+ bearing an AIE fluorophore

It is well known that the silver ions (Ag+) are important in the human body, however, novel probes were lacked with good water solubility, biocompatibility and deep penetration to detect Ag+ in the organism. In this work, we report two new three-photon absorption AIE luminogens (AIEgen), abbreviated as Tpy and Tpy-Hex, whereby Tpy-Hex could detect intracellular and environmental Ag+ quantitatively at a micromolar level. Tpy-Hex binding with Ag+ possesses enhanced three-photon absorption cross-section under1550 nm excitation (NIR II window), which is indeed beneficial for deep penetration in vitro and in vivo. The mechanism underlying the changes in three photon absorption spectra caused by bromohexyl chain substitution was further explored. The fluorescence bioimaging results reveal that the proposed probe Tpy-Hex could be ultra-sensitive for detection of Ag+ in HeLa cells and poisoned mice.