Effect of Sodium Carboxymethyl Cellulose Concentration on the Photophysical Properties of Zinc Sulfide Nanoparticles

The effect of sodium carboxymethyl cellulose (CMC) as capping agent on the optical (photo) and structural (physical) properties of zinc sulfide (ZnS) nanoparticles was studied. The capped nanoparticles were grown by the precipitation technique. The capping ratio of precursor (ZnS) to surfactant (CMC) (vol/vol) considered were 1:1 (sample S1), 1:2 (S2 sample) and 1:3 (sample S3 sample). Analyses carried out include; X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and photoluminescence studies. SEM analysis revealed particles as agglomerates. The obtained band gap energies of 4.13, 4.20 and 4.27 eV for samples S1, S3 and S2, respectively are blue shifted when compared to the band gap energy of bulk ZnS semiconductor indicating quantum effect. The calculated particle sizes from XRD ( 3.14, 3.73 and 15.7 nm for samples S3, S2 and S1, respectively) and effective mass approximation (3.59, 3.77 and 3.98 nm for samples S2, S3 and S1, respectively) were found to vary with the capping amount, though not monotonically. Capping ZnS with higher amount of CMC provided more stable nanoparticles, although with lower luminescence. The emission peaks of samples S3and S2 were red-shifted when compared to that of sample S1. At low CMC capping amount, the luminescence was found to be very high and blue shifted due to a greater participation of surface trap states.