Novel composite unit with one pyridinium and three N-halamine structures for enhanced synergism and superior biocidability on magnetic nanoparticles

Abstract

A novel composite unit of enhanced synergism that rises from the use of a cationic pyridinium structure to attract anionic bacteria to three N-halamine structures was designed for superior biocidability on recyclable magnetic nanoparticles. Briefly, 5-(4-hydroxybenzylidene)hydantoin (HBH), containing one imide and amide NH bonds, was synthesized by Knoevenagel condensation ofp-hydroxybenzaldehyde with hydantoin. 3-Triethoxysilylpropyl succinic anhydride was ammonolyzed with 4-aminopyridine to introduce a pyridine structure and form an amide NH and a carboxylic acid group that was esterified with HBH to introduce its two NH bonds. The triethoxysilyl groups of the esterification product were hydrolyzed into silanols to condense with the counterparts of different hydrolysates and on silica modified Fe3O4nanoparticles to provide a layer of polymeric modifier. After quaternization of the pyridine and chlorination of NH bonds from each esterification product, the resultant layer is composed of units each of which contains one pyridinium and threeN-halamine sites and exerted higher biocidability against Escherichia coli and Staphylococcus aureus than comparable systems including synergistic ones with one cationic center and one N-halamine, demonstrating an enhanced synergism. The biocidal layer had promising stability under quenching-chlorinating cycles and long-term storage. The study affords a strategy for syntheses of more powerful biocidal surfaces.