Quantum dots (QDs) attract extensive research interest as optical labels for sensing events owing to their outstanding photophysical features. Molecular and ion recognition has been combined very recently with the unique optical properties of QDs to begin building a new generation of QD-based sensors, that is, functional modification of QDs. Surface functional modification for QDs will improve their water solubility and recognizing selectivity. This review, which follows the classification of linked atom between QDs and functional ligands such as QDs linked with sulfur atom (including modification QDs with simple mercapto compound, modification QDs using simple mercapto compound as precursor, modification QDs with other mercapto compound and modification QDs using carbon disulfide as linker), QDs linked with oxygen atom and QDs linked with nitrogen atom, summarizes the research for recognizing of inorganic ion and small molecule based on above functional modification QDs from 2005 to update.

Contents
1 Introduction
2 Functional modification QDs linked with sulfur atom
2.1 Modification QDs with simple mercapto compound
2.2 Modification QDs using simple mercapto compound as precursor
2.3 Modification QDs with other mercapto compound
2.4 Modification QDs using carbon disulfide as linker
3 Functional modification QDs linked with oxygen atom
4 Functional modification QDs linked with nitrogen atom
5 QDs modified by other manners
6 Conclusion