Contents I. Introduction
Quantum dots (QDs) or semiconductor nanocrystals have been widely studied these years for their unique optical and electronic properties: high fluorescent yields and extinction coefficient, low photobleaching, wide excitation band but most importantly narrow, symmetric emission peaks. Due to these marvelous properties, they become attractive fluorescent probes for biosensing and imaging applications such as tumor detection of pre-cancers, which are not available with traditional organic dyes and fluorescent proteins.[1] For many applications, these quantum dots would benefit from having a silica shell to impart wettability and biocompatibility. Silica can also be easily surface modified to link bioconjugators, such as avidin, with interesting biofunctionalities. Many work have been reported on synthesis of II-VI QDs, especially CdSe QDs fabricated by organometallic precursor route, which was developed by Murray et al in 1993.[2] These QDs have a wide fluorescent emission spectra ranging from blue to red. [3] Simultaneous, coating QDs with silica also widely investigated because silica chemistry is a mature field, resulting in a water-soluble and less toxic core/shell structure. The QDs-core with silica - shell offers the use of various methods for labeling biomolecules with silica -coated fluorescent QDs.[4] [6], [7]
