Synthesis, characterization and applications of high potency antimicrobial colorants.

In this study, two series of antimicrobial colorants with outstanding antimicrobial properties were synthesized by incorporating quaternary ammonium salts (QAS) structures into anthraquinone chromophores with stable alkyl amino linkage. The structures of the colorants were characterized by Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (NMR) and UV-vis spectrometry. These dyes demonstrated excellent antimicrobial functions against both Gram-negative and Gram-positive bacteria in aqueous solutions, indicated by low minimum inhibitory concentrations (MIC). The colorants also showed good stability toward light, heat and high/low pH in water. Next, the structure-antimicrobial property relationship and the other environmental factors such as time, temperature, pH, anionic surfactants and divalent cations on the antimicrobial activity of the colorants were studied. The results showed that the antimicrobial activities of the colorants were promoted by higher temperature and lower pH, and the colorants could be inactivated by anionic surfactants and addition of divalent cations Mg2+ or Ca2+. Last, the colorants demonstrated strong synergistic effect when mixed with ethyl alcohol at 10 V%. Adsorption of the colorants on acrylic fabrics as adsorbents was also performed in batches in a shake bath. The regular structures of the colorants make it possible to systematically evaluate the influences of dye size, configuration on the adsorption rate. Other experimental parameters such as temperature and bath ratio were also investigated. Most colorants fit the pseudo-first-order kinetic model. Langmuir isotherm was utilized to further analyze the intrinsic influence of the structures of the colorants on their adsorption behavior. Thermal dynamics study showed that the adsorption of the colorants is endothermic and spontaneous at 95°C.