Two-photon absorption in ZnO/ZnS and ZnO/ZnS/Ag core-shell quantum dots，LIU Shuyu，ZHONG Mianzeng，We report on large two-photon absorption (TPA) in ZnO/ZnS and ZnO/ZnS/Ag core/shell quantum dots (QDs), determined by both Z-scan and pump-probe techniqu