Optical properties of hydroxyethyl cellulose film treated with nitrogen plasma

• Hydroxyethyl cellulose film is prepared by casting technique.
• Prepared film is exposed to nitrogen plasma at different times.
• Refractive index of film is modulated via treatment of plasma.
• Optical band gap of film is changed effectively with plasma treatment.

Hydroxyethyl cellulose (HEC) film has been prepared by casting technique. The prepared sample has been treated with nitrogen plasma at different exposure times. The optical absorption was recorded at room temperature in the wavelength range of 200–800 nm. Absorbance fitting procedure curves revealed a direct allowed transition with optical band gap, Eopt, of 4.9 eV for pristine film, and this value decreases to 4.30 eV for 20 min plasma treatment time. The band tail values (Ee) were found to be increased under plasma time treatment from 1.74 eV in case of the pristine film to 2.20 eV for 20 min. The dispersion of refractive index and complex dielectric constants under plasma treatment was also studied. Variation of color parameters under effect of the plasma treatment is analyzed in the framework of CIE L*U*V* color space.

Absorbance spectra of hydroxyethyl cellulose film under different plasma treatment times.Figure optionsDownload as PowerPoint slide