M Naghib - Department of chemistry, Science and Research Branch, Islamic Azad University, Tehran,Iran
M Yousefi - Department of chemistry, Science and Research Branch, Islamic Azad University, Tehran,Iran

In this research, core shell QDs have been synthesized through 2 different ways. ZnO quantum dots (QDs) were synthesized by a modified sol–gel method and in situ coated with the amino acid cysteine and cystine to modify their surface chemistry and govern the crystal growth process. Surface chelation by a hydrophilic thiol such as cysteine offered a fine control over the particle size and modulated the optical emission and its stability by reducing the density of surfacial oxygen deficiencies and also induced the formation of hierarchical nanostructures in the solution. At The first method, core shell QDs have been synthesized by cystine modified ZnO, which used as core and nanosulfur used as shell. ZnO have been synthesized by sol gel and nanosulfur prepared by sonochemistry method. The XRD pattern at 2θ : 31.800,34.449,36.299,47.563,56.614,62.893 attributed to hexagonal phase of ZnO and the peaks at 2θ : 15.350,23.067,25.853,26.724,27.705,28.689 , attributed to sufur with the Orthorhombic phase . Nanopowder characterized by SEM, IR analysis.SEM showed a Proportional distribution and the average particles size is indicated as 77.50 nm. In addition, IR results showed compound formation. At the second method, cysteine modified ZnO used as core and cysteine modified nanosulfur used as shell. SEM showed the spherical nanoparticles and The XRD pattern at 2θ: 25.920, 26.853, 28.522 confirmed with standard 2θ of sufur with the orthorhombic phase, but the nanopowder synthesized was amorphous. SEM results confirmed the formation of mono-dispersed and spherical ZnO QDs in the size range 60 nm. Totally first method found better than second one and both of them are a good candidate for using as sunscreen.

Core/Shell, Quantum Dot, Cystine, Sonochemistry, Sunscreen