One-pot synthesis of thermal responsive QDs-PNIPAM hybrid fluorescent microspheres by controlling the polymerization temperature at two different polymerization stages
One-pot synthesis of thermal responsive QDs-PNIPAM hybrid fluorescent microspheres by controlling the polymerization temperature at two different polymerization stages
复制标题
通过控制两个不同聚合阶段的聚合温度一锅法合成热响应QDs-PNIPAM杂化荧光微球
DOI：
10.1039/c1jm10104h
复制
发表时间：
2011-01-01
影响因子：
--
通讯作者：
Li, Wen-You
中科院分区：
文献类型：
--
作者：
Wang, Yan-Qin;Zhang, Ye-Yun;Li, Wen-You
在本研究中，首次在没有任何两亲性聚合物或可聚合表面活性剂的情况下，只需在两个不同的聚合阶段控制合成温度，就可以在单体聚合过程中将3-巯基丙酸(MPA)包覆的CdTe量子点(QDS)一锅共聚合成聚N-异丙基丙烯酰胺(PNIPAM)微球。在第一阶段，NIPAM单体在低于临界溶液温度(LCST)的条件下被过硫酸钾(KPS)引发形成PNIPAM网络，其中的CdTe量子点分布广泛。在第二阶段，当聚合温度高于LcST时，PNIPAM网络崩塌形成球体，并将CdTe量子点包裹到PNIPAM微球(记为CdTe-PNIPAM微球)中。透射电子显微镜(TEM)图像显示，CdTe量子点已经成功地包裹在PNIPAM基质中。动态光散射(DLS)结果表明，所制备的CdTe-PNIPAM杂化微球的粒径分布较窄，平均流体力学直径约为267 nm。与原有的CdTe量子点相比，所制备的CdTe-PNIPAM微球不仅具有显著的发射波长红移(达36 nm)，而且具有温度依赖性的开关荧光特性。在LCST附近，随着温度的升高，荧光强度急剧下降；当溶液冷却时，荧光强度将恢复。此外，经过反复的加热和冷却循环，在LCST区域周围的光致发光(PL)猝灭和增强过程是完全可逆的。
In the present study, for the first time, without the help of any amphiphilic polymers or polymerizable surfactants, 3-mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) could be one-pot copolymerized into poly(N-isopropylacrylamide) (PNIPAM) microspheres during the monomer polymerization process just by controlling the synthesis temperature at two different polymerization stages. In the first stage, NIPAM monomers were initiated by potassium persulfate (KPS) below the lower critical solution temperature (LCST) to form PNIPAM networks with CdTe QDs distributed throughout. In the second stage, when the polymerize temperature was raised above the LCST, the PNIPAM networks collapsed to form spheres and the CdTe QDs were entrapped into the PNIPAM microspheres (denoted as CdTe-PNIPAM microspheres). Transmission electron microscopy (TEM) images showed that CdTe QDs have been successfully entrapped within the PNIPAM matrix. According to the dynamic light scattering (DLS) results, the CdTe-PNIPAM hybrid microspheres had a significantly narrow size distribution and their mean hydrodynamic diameter was about 267 nm. Compared with the original CdTe QDs, the CdTe-PNIPAM microspheres exhibited not only a prominent red-shift of their emission wavelength (as much as 36 nm), but also temperature dependent on-off fluorescence properties. Around the LCST, when the temperature was increasing, the fluorescence intensity decreased sharply; when cooling the solution, the fluorescence intensity would restore. Moreover, after repeated heating and cooling cycles, the photoluminescence (PL) quenching and enhancement processes were fully reversible around the LCST region.