Semiconductor Nanocrystals and Graphene Oxide as Visible-Light-Sensitive Photoinitiators of Acrylamide Polymerization in Water

Abstract

Photopolymerization of acrylamide in aqueous solutions induced by visible light (>400 nm) absorbed by colloidal particles of Cd x Zn 1-x S, Fe 2 O 3 and graphene oxide is reported. Depending on the photoinitiator nature, primary radicals are generated by monomer reduction with conduction band electrons (Cd x Zn 1-x S), monomer oxidation by the valence band holes (Fe 2 O 3) or by interaction between monomer and free radicals photoeliminated from graphene oxide. The photopolymerization rate increases proportionally to the conduction band potential of Cd x Zn 1-x S nanoparticles that depends on their composition. The Fe 2 O 3-initiated acrylamide photopolymerization proceeds with comparable effectiveness in both deaerated and air-exposed aqueous solutions, the feature differing drastically from typical organic photoinitiators. On the basis of kinetic parameters the photopolymerization process was found to be of the chain free radical character with a principal chain termination route being macro-radicals recombination. The kinetic data also indicate a possibility of participation of the Cd x Zn 1-x S nanoparticles and graphene oxide in the chain termination.

Rapid Three-Dimensional Printing in Water Using Semiconductor–Metal Hybrid Nanoparticles as Photoinitiators

“…Our hypothesis was that the photogenerated ROS could initiate rapid polymerization of water-soluble monomers under low light intensity. Although semiconductor nanocrystals were reported to generate ROS in the presence of water and molecular oxygen, ,− their utility in photopolymerization required high intensity UV lamps and irradiation for prolonged duration, unsuitable for 3D printing. − …”