Novel nano silica assisted synthesis of azo pyrazole for the sustainable dyeing and antimicrobial finishing of cotton fabrics in supercritical carbon dioxide

A new protocol was developed for the synthesis of azo pyrazole derivatives via one-pot reaction of β-ketonitriles and phenyl hydrazines in the presence of nano SiO₂ as a mild catalyst. The synthesized dyes were elucidated using spectrophotometry, mainly NMR; FTIR; UV as well as elemental analysis. The dyeing was carried out utilizing supercritical carbon dioxide as a green medium. Outstanding deep color shades and excellent dye fixation were exhibited by all new dyes. Furthermore, the dyed samples revealed superlative color fastness. The biological evaluation of both the dyestuffs and the dyed samples showed overgrowing antimicrobial activity against the tested microorganisms. Therefore, our findings assured that disperse reactive dyes are the most commercially appropriate materials for dyeing cotton in supercritical carbon dioxide