| Quantum dots (QDs) have become one of the most attractive fields of current research because of their unique optical properties and potential application in the bioimaging and labeling. In this paper, we systematically studied the synthesis of CdSe, CdTe, CdSe1-xTex and core-shell QDs in the"cheaper"and"greener"paraffin liquid/oleic acid synthetic system compared with the traditional trioctylphosphine oxide (TOPO) synthetic system, and their potential application in the multiplexed bioassays. The main contributions were as follows:(1)The synthesis of CdSe QDs in paraffin liquid/oleic acid was systematically studied. The results demonstrated that the growth of the CdSe QDs became more controllable than in the traditional TOPO synthetic system, and the"bright point"of the photoluminescence quantum yield (PLQY) tended to appear in the initial growth period of the CdSe QDs in our system, which enabled the as-prepared small size CdSe QDs own high PLQY of 30-50% in the emission wavelength ranged from 470 to 530 nm, and the result was superior to those prepared in TOPO. The as-prepared CdSe QDs also had good thermal stability, which was very important for their bio-applications. Moreover, we successfully extent this route to the synthesis of 570-720 nm emitting CdTe QDs with high PLQY up to 65% and good thermal stability.(2)In order to obtain the red to near-infrared emitting QDs, highly-fluorescent CdSe1-xTex alloyed QDs with PLQY up to 70% were successfully prepared through our route. The results demonstrated the as-prepared CdSe1-xTex alloyed QDs had a Te-rich core/ Se-rich shell gradient alloyed structure, and possessed stronger photoluminescent properties than those prepared in TOPO. The optical stability of the CdSe1-xTex QDs was also systematically investigated in detail under the variable temperatures ranging from 1 to 60 oC and UV irradiation at a wavelength of 365nm, respectively, and the results demonstrated the alloyed CdSe1-xTex QDs had good optical stabilities against the temperature change and photobleaching.(3) An one-pot route to synthesize the high-quality CdSeTe/CdS/ZnS core/multi-shell QDs was developed. The as-prepared core/multi-shell CdSeTe/CdSe/ZnS QDs possessed not only enhanced optical properties but also better optical stabilities compared with the CdSeTe core QDs. The mechanism of shell growth was also studied by using different S shell precursors, and the results demonstrated trioctylphosphine sulfide (TOPS) facilitated a slower release of the S monomers in the reaction solution compared with unbound S, which resulted in a thinner but more uniform shell distribution around the core and the as-prepared multi-shell QDs with higher PL QY. While unbounded S resulted in a thicker shell with more defects around the core for its fast growth rate, and consequently the as-prepared multi-shell QDs had a better stability but lower optical property(4)The as-prepared CdSe and CdSe1-xTex QDs were successfully incorporated into the carboxyl capped porous polystyrene (PS) microbeads to fabricate optical encoded microbeads and the biotinlated goat anti-mouse IgG could be specifically coupled to the CdSe1-xTex QDs encoded beads via mouse anti-human chorionic gonadotrophin connected to the carboxyl groups on the encoded microbeads, which suggested their potential application in multiplexed bioassays.
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