Synthesis and optical characterization of ZnS-sodium carboxymethyl cellulose nanocomposite films

In this work, the synthesis and characterization of ZnS-sodium carboxymethyl cellulose nanocomposite films were studied. The film was prepared by casting after the in situ precipitation of ZnS in sodium carboxymethyl cellulose (NaCMC) aqueous solution. The in situ method avoids nanoparticles aggregation and improves its dispersion. The resulting nanocomposite was characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The results showed that ZnS nanoparticles with a blende structure and a particle size in the range of few nanometers are well dispersed in the sodium carboxymethyl cellulose films. Optical properties were analyzed by using UV-vis spectroscopy and photoluminescence spectroscopy (PL). The resulting nanocomposite films showed optical transmission between 50% and 90% influenced by the amount of ZnS nanocrystals into the nanocomposite films. The PL spectra of the nanocomposite films exhibits a broad visible emission band centered at 445 nm under UV light excitation (λ = 320 nm). These luminescent films might have a potential application in security paper by using an optical signature.