Influence of nickel hydroxide nanoparticles on the structural self-organization of fibroin microparticles
Silk fibroin is a protein that has easy processing and excellent biocompatibility. Its properties are directly related to its hierarchical structures, especially the formation of β-sheet crystallites. Studies have shown that silk fibroin properties can be modulated according to the manipulation of these structures by the introduction of external materials acting as nucleating agents for β-sheet crystals growth. Nickel-cobalt hydroxide is a material well known for its electrocatalytic properties, but recently new routes for the synthesis of nanostructures of this material have been developed, broadening its applications. In this way, the present work aims to study the influence that the introduction of nickel-cobalt hydroxide nanoparticles can have on the formation of the hierarchical structures of fibroin, as well as the stabilization capacity of nickel-cobalt hydroxide nanoparticles and finally explore the synergy between these materials in the field of electrochemistry. The results showed an increase in the percentage of crystallinity of fibroin with the introduction of nickel-cobalt hydroxide nanoparticles, from 36% for pure fibroin up to 50% with the introduction of 20% by mass of nickel cobalt hydroxide, corroborating, therefore, the nucleating effect of nanoparticles. Images obtained from transmission electron microscopy showed nanoparticles with an average size of 6 nm for the samples with fibroin, while the samples of pure nickel-cobalt hydroxide showed structures with an average size of 80 nm, suggesting that the fibroin was capable to stabilize the nanoparticles. Both effects appeared to be related to the improvement observed in the electrochemical properties of the composite, which were superior to the properties of pure nickel hydroxide. Finally, the results of hydrogen peroxide electrogeneration using fibroin and nickel hydroxide proved to be promising, with high production and low energy consumption when compared with the standard material and with results from the literature.