Utilizing cellulase as dispersant to prepare stable nano-pigment suspension and investigating its coloring performance on cotton fabrics

• A nano-pigment suspension was prepared using crude cellulase as dispersant.
• This nano-pigment suspension exhibits good stability.
• The nano-pigment particles show a charge-adjustable property.
• Higher color depth on cotton can be achieved at low pH due to strong charge attractions.

In this research, a novel nano-pigment suspension was successfully prepared in an ultrasonic disruptor using crude cellulase as dispersant. The colloidal and rheological properties of this cellulase-based suspension such as zeta potentials, particle distribution and apparent viscosity were analyzed. The measurement of zeta potentials showed that the surface charges of pigment were adjustable along with the acid–base properties of external environment due to the amphoteric character of cellulase proteins. Subsequently, its stability to high-speed centrifuge, freeze–thaw treatment and ion intensity was carefully investigated. Thermo-gravimetric analysis (TGA) was conducted to demonstrate the coverage of pigment particles by cellulase proteins. Furthermore, X-ray diffraction (XRD) characterization was utilized to disclose the combined impacts of cellulase and ultrasonic power on the crystal structures of pigment. At last, the coloring performance of this charge-adjustable nano-pigment suspension on cotton substrates was evaluated by measuring their K/S values and color fastness. Scanning Electron Microscope (SEM) was carried out to give a direct observation of the nano-pigment distributed on cotton surfaces.

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