Synthesis, Physicochemical and Microbial Evaluation of Phenylazo-1Naphtholazobenzene (A Novel Disazo Dye)

Abstract

Azo dyes are the most important synthetic colourants which have been widely used in textile, paper 
manufacturing and printing. A novel disazo dye, Phenylazo-1-naphtholazobenzene was synthesized and 
characterized using UV-Visible, FTIR spectrophotometric and elemental analytical tools. The result of the 
elemental analysis was found to be in conformity with the molecular formular of the dye. The UV-Visible 
spectra indicated that the dye absorbed at visible region of 499.0 nm, characteristics of intensely coloured 
dyes. The FTIR spectral study showed absorption bands conforming to the various functional groups: - OH 
stretch of non-bounded hydrogen at 3169.38cm-1, CH stretch of alkenes and aromatics at 3015.26 cm-1. 
C=C stretch of a conjugated aromatic compounds at 1654.15 cm-1, -N+=N of stretch of diazonium salt at 
2277.13cm-1, - N=N- group stretching at 1452.02 cm-1, C-OH out of plane deformation at 6070.60cm-1 and 
NH deformation at 721.62 cm-1 in the dye. The colour imparted by the dye on the tested fabrics using Gray 
Scale for colour change, indicated very good to excellent lightfastness, and heatfastness, and very fair to 
good washfastness, except polyester and fine worsted wool which showed fair washfastness. The 
toxicological testing indicated that the dye has no effect on the Deoxyribonucleic Acid (DNA) of 
Escheriachia coli and Aspergillus niger but at high concentration, it denatured human DNA. The dye did 
not have adverse effect on the growth of Zea mays used for growth profile evaluation. Microbial toxicity 
of the synthesized dye on E. coli, A. niger and Bacillus cereus showed that all the strains are moderately 
resistant to the dye.  The synthesized dye showed very good to excellent colourfastness, and fibres, not safe 
for human consumption, however, they are not toxic to the environment.