Project of the month, June 2008
Synthesis of colloidal QDs |  |
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It has become a rather common practice to prepare QDs with the size so small that quantum confinement effects are manifested. However, in practical applications of such QDs, particularly in biological applications, the mere small size is often not sufficient. Many other factors need to be considered in the material selection, such as the toxicity, functionality, stability and signal detectability (penetration depth and resolution of signal). These factors in turn pose limitations on the available synthesis methods. We use two categories of materials: 1) ZnO and related materials, 2) CdS, ZnSe and related materials, as the basic components for QDs. They have been tailored with respect of their chemical components, geometric dimensions, and surface modifications using solution processes, in order to cover the relevant wavelengths. Tailor-made semiconductor/semiconductor core-shell structures and/or semiconductor/metal core-shell structures by chemical deposition and buffer layers (PEG or silica) are produced in order to create special excitation-emission conditions, to utilize the beneficial effects of surface plasmon polaritons, and to attach targeting elements. The synthesis methods are solution-based sol-gel processes. The prepared QDs are stored in suspension liquids preventing for agglomeration.
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