In situ synthesis of Fe3O4/ carboxylated multi-walled carbon nanotubes nanostructures on nylon fabric with efficient flame retardant and antibacterial properties

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Knitted fabrics are ideal for flexible, conductive, and magnetic smart textiles but have low adhesion for materials, especially inorganic ones. In this study, carboxylated multi-walled carbon nanotubes (MWCNT-COOH) and magnetite (Fe3O4) magnetic nanoparticles were synthesized in situ and then coated onto nylon knitted fabric. Using nylon and in situ coating of these nanostructures enhances nanotube absorption via hydrogen bonding and provides magnetite growth sites on both the coated nanotubes and the fabric surface, due to the direct attraction of positively charged iron salts to the polar bonds of nylon. The effect of the weight ratio on the characteristics was evaluated through the coatings with Fe3O4 to MWCNT-COOH at different ratios. Surface structure, chemical analysis, microstructure, electrical conductivity, magnetic properties, antibacterial properties, zeta potential, and thermal properties were studied. FESEM results and surface structure evaluation indicated that increasing the quantity of iron salts influenced the morphology: a single layer was observed at a 2:1 ratio and the combination of layers and particles at 4:1 and 6:1 ratios. At 8:1, there was a recurrence of a layered structure. Magnetite nanoparticles led to the fusion of carbon nanotubes and this was evident from the magnetic characteristic of the fabric. Magnetic properties showed an increasing trend up to the 6:1 ratio (from 0.06 emu/g to 1.00 emu/g) and then decreased at the 8:1 ratio (0.71 emu/g) due to an increase in the number of agglomerations in the solution. These observations were further supported by crystallography analysis of the synthesized magnetite nanoparticles which showed variations in the crystal size. The fabric had better adhesion of carbon nanotubes with increased iron salt content which helped in coating and conductivity. The introduction of these nanostructures also greatly enhanced the heat-resistant properties of the fabrics with the burning length reduced by about 70 % while the photothermal properties of the fabrics reached 81°C. In addition, a significant antibacterial effect was observed in the present study with a minimum of 64 % efficiency under non-irradiated conditions and up to 99 % bacterial killing under irradiated conditions.