Preparation and optimization photocatalytic activity of polymer-grafted Ag@AgO core-shell quantum dots.

A linear-dendric copolymer containing polyethylene glycol-polycitric acid used as a capping agent to the green inter-matrix synthesis of silver/silver oxide core-shell quantum dots (Ag@AgO QDs). Water-soluble Ag@AgO QDs were synthesized with high yield and narrow size distribution. Here, Ag ions were trapped in the polymer branches and covalently bonded to it. Another sample of Ag@AgO QDs was synthesized through the same method and conditions without any capping agent (raw nanoparticles). Structure, size distribution, and morphology of raw and copolymer-grafted nanoparticles were identified using X-Ray diffraction, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The results from XRD pattern and UV spectra confirmed the Ag@AgO structure of both nanoparticles. From the FESEM image, the size of Ag nanoparticles obtained at the range of 1-20 nm. HRTEM image of grafted nanoparticles directly showed that these nanoparticles have very tiny size in the range of 1-2 nm and presented in the form of core-shell Ag@AgO. Thus, both raw and polymer-grafted samples are in the range of quantum dots (QDs). Raw and polymer-grafted Ag@AgO QDs which take the advantage of water solubility and biosafety, were used as photocatalyst for degradation of cationic methylene blue (MB) and anionic methyl orange (MO) dyes at low and high concentrations of each dye. Results shows using polymer-grafted QDs leads to a significant enhancement both in the efficiency and rate of dye degradation, compared to the case of using raw nanoparticles.