title: Highly Photoluminescent and Stable Aqueous ZnS Quantum Dots.
abstract: We report an all-aqueous synthesis of highly photoluminescent and stable ZnS quantum dots (QDs) with water as the medium, i.e. first synthesizing ZnS QDs with 3-mercaptopropionic acid (MPA) as the capping molecule, followed by replacing some of MPA with (3-mercaptopropyl) trimethoxysilane (MPS). The resultant MPS-replaced ZnS QDs were about 5 nm in size with a cubic zinc blende crystalline structure, and had both MPA and MPS on the surface as confirmed by the Fourier Transform Infrared (FTIR) spectroscopy. They exhibited blue trap-state emissions around 415 nm and a quantum yield (QY) of 75% with Rhodamine 101 as the reference, and remained stable for more than 60 days under the ambient conditions. Through the capping molecule replacement procedure, the MPS-replaced ZnS QDs avoided the shortcomings of both the MPA-ZnS QDs and the MPS-ZnS QDs, and acquired the advantages of strong photoluminescence and good stability, which are important to the QDs' applications especially for bioimaging.
authors.affiliation: Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Wan Y
authors.initials: WY
authors.lastname: Shih
authors.forename: Wei-Heng
authors.initials: WH
authors.lastname: Shih