单分散CdS纳米晶/PNIPAM复合水凝胶的制备及其温敏荧光特性

采用液体-固体-溶液法(LSS)制备单分散CdS纳米晶;通过自由基聚合制备单分散CdS纳米晶/聚N-异丙基丙烯酰胺(CdS/PNIPAM)复合温敏水凝胶.采用HRTEM、XRD、FTIR、DSC、PL等对CdS纳米晶、CdS/PNIPAM温敏复合凝胶的微观结构与性能进行了表征,变温荧光光谱研究了温度对凝胶荧光性能的影响.结果表明,CdS纳米晶粒径约为2.8 nm,单分散性良好;复合凝胶的荧光发射强度与环境温度存在一定的关联性,且呈可逆性.

PREPARATION OF MONODISPERSE CdS NANOCRYSTALS/PNIPAM HYDROGEL AND ITS THERMOSENSITIVE FLUORESCENCE

In order to investigate the influence of polymer aggregate state and chemical environment on the fluorescent performance of nanocrystal,monodisperse CdS nanocrystal is prepared via liquid-solid-solution synthesis(LSS) strategy,and monodisperse CdS nanocrystals/poly(N-isopropylacrylamide)(PNIPAM) complex hydrogel are prepared by radical polymerization.The microstructure and performance of the monodisperse CdS nanocrystal and the complexes hydrogel are characterized by high resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),Fourier transformed infrared spectroscopy(FTIR),differential scanning calorimetry(DSC) and photoluminescence(PL).As evidenced from the HRTEM photos and XRD patterns,CdS nanocrystals show well monodispersity,and their size is about 2.8 nm.PL spectrum shows that CdS nanocrystal has a strong emitting peak around 533 nm and a weak emitting peak around 469 nm.DSC curves suggest that the complex hydrogel is thermosensitive,and LCST of which is higher than that of PNIPAM hydrogel.The results of PL spectra and DSC curves indicate that the complex hydrogel shows well thermosensitive-fluorescent performance,the variation of the fluorescent intensity of the complex hydrogel is in good agreement with its phase transformation.With variation of environmental temperature from 20℃ to 45℃,the complex hydrogel changes from swollen state to collapse state,and the chemical environment around CdS nanocrystal changes from hydrophilic to hydrophobic,quantum yield of CdS nanocrystal changes respectively.The lower the environmental temperature is kept,the lower fluorescent intensity of the complex hydrogel is observed,and the fluorescent intensity changes sharply around its LCST.Testing on PL intensity change of CdS/PNIPAM hydrogel as a function of cooling-heating cycles between 20℃ and 40℃ demonstrates that the thermosensitive-fluorescent performance of the CdS/PNIPAM hydrogel is reversible.