pH-responsive nanovalves based on hollow mesoporous silica spheres for controlled release of corrosion inhibitor

In the present study, a new encapsulation technique for corrosion inhibitor is proposed. The hollow mesoporous silica spheres (HMSs) were synthesized by the co-templates method as nanocontainers for corrosion inhibitor, benzotriazole (BTA) and the supramolecular nanovalves, consisting of cucurbit[6]uril (CB[6]) rings and the functional stalks attached to the surface of HMSs achieved on-demand release. The synthesis process of HMSs and the assembly process of the nanovalves were confirmed by SEM, TEM, N-2 adsorption/desorption, FTIR, TGA and solid-state C-13 CP/MAS NMR. The encapsulation capacity and release characteristics of BTA-loaded, assembled HMSs were investigated. The HMSs assembled with the nanovalves possessed a higher encapsulation capacity for BTA than MCM-41 assembled under the same procedure due to its huge hollow internal structure. The pH-controlled release properties of BTA from the assembled HMSs under different pH environments were monitored by ultraviolet absorption spectra. The release profiles showed that there was almost no leakage of BTA from the assembled HMSs in neutral solution, while in alkaline solution BTA released very quickly, and the release rate increased with increasing pH values. Such a property makes the HMSs assembled with the pH-responsive nanovalves have great potential applications in smart anticorrosion coatings.