Selective Modification of Halloysite Nanotubes with 1-Pyrenylboronic Acid: A Novel Fluorescence Probe with Highly Selective and Sensitive Response to Hyperoxide

A novel fluorescence probe based on modified halloysite nanotubes (HNTs) by using 1-pyrenylboronic acid selectively grafted onto the inner surface of lumen was successfully achieved. The solid-state nuclear magnetic resonance (C-13 and B-11), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) confirmed that the boronic acid group only binds to alumina at the tube lumen and does not bind the tube's outer siloxane surface. The modified HNTs (HNTs-PY) inherit the spectroscopic properties relating to the pyrene units. Interestingly, the established Al-O-B linkage gives the H2O2-sensitivity to pyrene grafted tubes. HNTs-PY exhibits a highly specific "turn-off' response for hyperoxide over other reactive oxygen species (ROS) and oxidative ions owing to their chemoselective boronate-to-phenol switch. The "turn-off' response can even be tracked when the additional amount of H2O2 was limited to 1 x 10(-6) mol. Thus, the selective modification method under mild conditions for the design of novel organic inorganic hybrid fluorescence probe may open up a broader application as well as for identification and diagnosis.