Enhanced Photoluminescence for ZnS Nanocrystals Doped with Mn2+ Close to Carboxyl Groups and/or S2− Vacancies

Abstract

AbstractZnS nanocrystals doped with Mn2+ ions are prepared by a solution process and subsequent UV irradiation to produce the samples with different S/(Zn+Mn) ratios and/or surface modification by acrylic acids. Coordination states around Mn2+, ions were examined at 9 and 35 GHz by electron paramagnetic resonance spectroscopy. The Mn2+ sites in the vicinity of 2- vacancies or carboxyl groups are observed at the frequencies more than 9 or 35 GHz, respectively, for nanocrystals, but are not for the bulk sample of 250 nm diameter. Such Mn2+ sites enhance the photoluminescence due to d-d transition of Mn2+ ions through energy transfer from S2- vacancies or carboxyl groups, excited simultaneously by a light of 350 nm for exciting ZnS.