Chitosan-modified halloysite nanotubes as a controlled-release nanocarrier for nitrogen delivery

Halloysite nanotubes (Hal) are naturally occurring tubular clay nanomaterials that have a unique tubular structure and surface modifiability. In order to increase the stability and to achieve controlled release of fertilizers, chitosan (CS) was assembled on the surface of Hal as a valve for preparing Hal@CS and to control the mesoporous surface and lumen ports. Transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared, thermogravimetric analysis and nitrogen adsorption isotherm analysis were conducted to confirm the successful grafting of CS onto the surface of the Hal. The cumulative release ratio of urea from the Hal@CS in vitro after 96 h was 34.37% without glutathione (GSH). After introducing GSH the rate of release of urea from the Hal@CS increased. The uptake, translocation, and distribution of the Hal@CS in the epidermal layer and endodermis of root tissue were detected by fluorescence labeling and TEM. We conclude that Hal@CS are a potential controlled-release carrier and delivery system for agricultural fertilizers.