Natural Halloysite Nanotube as a Spatially Confined Nanoreactor for Improving Photocatalytic Performance

Synthetic confined systems with inner cavity have attracted extensive research interest in many fields, but how to engineer an effective and inexpensive confined microsystem remains a great challenge owing to normally the same physicochemical properties of cavity's inner and outer surfaces and its sophisticated synthetic strategies. Herein, we demonstrate that a natural and low-cost halloysite nanotube (HNT) with an asymmetric layered structure is a spatially confined nanoreactor for enhancing the photochemical reaction. The higher Fe doping content of the Al-OH inner surface results in the obvious better photochemical activity and stronger adsorption ability of the inner surface of HNT compared with the outer surface. The unique asymmetric inner and outer properties induce the obvious spatial confinement effects of the lumen of HNT for improving the photocatalytic reaction. Compared with Kaolinte nanosheets (Kaol NSs), the normalized photocatalytic reaction rates of HNT were 1.3, 1.8, and 5.1 times that of Kaol NSs for the photodegradation of rhodamine, malachite green, and ciprofloxacin, respectively. The present work not only provides some new insights into the structure of HNT but also demonstrates a low-cost and eco-friendly spatially confined nanoreactor for biomedical and catalytic applications.

Automated summary

The use of halloysite nanotubes as spatially confined nanoreactors can significantly enhance the efficiency of photochemical reactions, outperforming other materials. The asymmetric inner and outer properties of halloysite nanotubes induce a significant spatial confinement effect, leading to improved photocatalytic reaction rates.