The PL spectrum of the ZnS nanoparticles was carried out by fluorescence spectrophotometer with Xenon lamp as the source of excitation, at 300 nm. An overall red shift was observed for the PL spectrums obtained by Bugil, with Mn    shifting more than Al  .

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It is also likely that the 600 nm peak was due to aggregation of nanoparticles that led to a larger particle size and hence longer wavelength that exceeded the usual nanoparticle dimensions. This is exemplified when the particle size obtained from SEM differs from XRD. While SEM shows the actual particle size, the XRD shows the particle size based on how it behaves.