Franci Kovač

A study of dye–surfactant interactions. Part 2. The effect of purity of a commercial cationic azo dye on dye–surfactant complex formation.

Abstract The interactions between the cationic azo dye C.I. Basic Yellow 25 and the cationic surfactant cetylpyridinium chloride have been studied by potentiometry, UV/VIS spectrophotometry and 1 H NMR. The effect of the purity of the commercial sample of the dye on the dye–surfactant interactions has been investigated. The results show that the cetylpyridinium chloride forms a complex with one of the components of the commercial sample of the dye in aqueous solution. The concentration of this component is decreased by purification of the commercial dye sample. The results also indicate that there are no dye–surfactant interactions in solutions of the cationic and nonionic components of the dye. According to this observation, we conclude that the surfactant cetylpyridinium chloride does not form a complex with the dye component in the commercial sample of C.I. Basic Yellow 25, and that the reduction of the free surfactant cation concentration in the solution causes reduction of the levelling action of the surfactant in the system involving the same charged dye and surfactant.

The influence of vat dyeing on the adsorption of synthesized colloidal silver onto cotton fabrics

Bleached, mercerized cotton fabrics were used in this research. In the first phase, the dyeing of cotton fabrics with a blue vat dye Bezathren Blau BCE was performed, and in the second phase, the dyed fabrics were immersed into a colloidal silver solution. The colloidal silver solution was prepared via synthesis from AgNO3 and reduced with NaBH4. Parent cotton fabrics were also immersed into the colloidal silver solution. A comparison of the quantity of silver on the parent and vat-dyed cotton fabrics was performed. Inductively coupled plasma mass spectrometry revealed a silver content that was almost two times higher on the dyed and silver-treated cotton fabrics. All samples (parent and dyed) treated in the colloidal silver solution showed excellent antimicrobial activity. The fiber surfaces were imaged using a scanning electron microscope. The mechanical properties of vat-dyed and vat-dyed silver-treated fabrics and the wash fastness of silver-treated samples were determined.

Antimicrobial wool, polyester and a wool/polyester blend created by silver particles embedded in a silica matrix

A two-step antimicrobial finishing procedure was applied to wool (WO) and polyester (PES) fabrics and a WO/PES fabric blend, in which the pad-dry-cure method was performed to create a functional silica matrix through the application of an inorganic-organic hybrid sol-gel precursor (RB) followed by the in situ synthesis of AgCl particles on the RB-treated fibres using 0.10 and 0.50mM AgNO3 and NaCl. The bulk concentration of Ag on the cotton fibres was determined by inductively coupled plasma mass spectroscopy. The antimicrobial activity was determined for the bacteria Escherichia coli and Staphylococcus aureus, and the fungus Aspergillus niger. The results showed that the highest concentration of the adsorbed Ag compound particles was on the WO samples followed by the WO/PES and PES samples. The antimicrobial activity of the finished fabric samples strongly depended not only on the amount of adsorbed Ag but also on the properties of the fabric samples. Whereas Ag biocidal activity was generated for the finished PES samples at Ag particle concentrations of less than 10mg/kg, the 34-times higher Ag particle concentration on the WO samples was insufficient to impart satisfactory antimicrobial activity because Ag chemically binds to the thiol groups on wool. The presence of wool fibres in WO/PES samples decreased the antimicrobial protection of the fabric blend compared with that of the PES fabric. A lethal concentration of adsorbed Ag compound particles for bacteria and fungi was produced only through the treatment of the WO and WO/PES samples with 0.5mM AgNO3.