Synthesis of extremely stable and water soluble quantum dots (QDs) would be smart if the method is rapid and eco-friendly. Herein, we have employed a simple strategy for the preparation of well dispersed, luminescent ZnO quantum dots by using pomegranate peel extract at room temperature. This method excludes the use of strong commercial stabilizing agents, different pH conditions, higher temperature and inert atmosphere during the synthesis. The microscopic study has revealed the ZnO QDs to be of a narrow size with an average size distribution of about 4 nm. The water soluble QDs exhibited a strong emission peak at 490 nm and were stable for twelve months. The emission from ZnO QDs are selectively quenched upon addition of Cr3+ ions. The interaction between the Cr3+ and the biomolecules on the exterior of ZnO QDs, enables the system to detect up to 2 nM Cr3+ ions in aqueous solution. (C) 2017 Elsevier Ltd. All rights reserved.