Silica/chitosan hybrid particles for smart release of the corrosion inhibitor benzotriazole

Chitosan-based organic-inorganic bio-hybrid nanocapsules, containing benzotriazole, a corrosion inhibitor, were prepared. In view of the versatile chemistry of silicon and the pH sensitivity of chitosan and benzotriazole, two synthesis approaches are presented. In both methods, tetraethoxysilane (TEOS) was used as the silicon source. Particles with different architectures, structural features and pH-dependent release behavior were obtained. The capsules prepared by the sol-emulsion-gel method demonstrated the highest release efficiency at pH 7.0 (∼90%) and pH 9.0 (∼65%) whilst the capsules prepared through layer-by-layer deposition technique showed the best efficiency at pH 3.0 (∼90%). Therefore, in combination, the particles delivered benzotriazole in a wide range of pH (from 3 to 9). The materials were fully characterized at the molecular, mesoscopic and nanometric length scales and the results suggest that they can successfully be applied in pH-sensitive smart coatings for corrosion inhibition.