Atmosphere-controlled high-voltage electrospray for improving conductivity, flexibility, and antibacterial properties of chitosan films

Atmosphere-controlled high-voltage electrospray (AHES) was utilised to modify the structure of chitosan (CS) films. The applied voltage in the AHES process ranged from 60 to 100 kV, with variations in the O₂ content of the propellant gas from 0 to 100 %. The number density of cations in the charging environment reached 600 × 10⁵ cations/cm³. Under these specific conditions, the one-step AHES procedure facilitated the protonation of the amine groups in the CS molecular chains, resulting in a notable increase in electrical conductivity by over 95 % and tensile elongation by over 100 %. The generation of reactive oxygen species during the AHES process also improved the antibacterial properties of the charged CS films, as evidenced by a more than 36 % increase in the inhibition zone diameter. The treated (AHES) films were employed for preserving fresh-cut muskmelon slices. These films maintained satisfactory sensory quality and effectively controlled water evaporation for up to 3 days when utilised as the inner layer of the packaging. These enhancements were achieved through a single-step AHES treatment, without the addition of chemicals or the need to alter the ambient temperature (25 °C ± 5°C). Consequently, AHES presents itself as a viable method for modifying the electrostatic characteristics of CS films and can be extended to various other materials.