上转换荧光响应性复合纳米凝胶的制备及荧光能量传递行为

采用水热法合成NaYF₄∶Yb³⁺,Er³⁺稀土纳米晶, 再经3-苄基三硫代碳酸酯基丙酸(BSPA)修饰, 制得功能化纳米晶体; 以罗丹明6G(R6G)为母体荧光染料, 经一系列反应合成了乙烯基功能化单体罗丹明6G酰基邻羧基苯甲肼腙(R6GHA); 将功能化纳米晶体与R6GHA构成荧光共振能量传递(FRET)的“给体/受体”对, 通过可逆加成断裂链转移(RAFT)聚合和“点击化学”反应, 合成具有多重响应性复合荧光纳米凝胶NaYF₄∶Yb³⁺,Er³⁺/PNIPAm-co-R6GHA. 采用TEM, XRD, FTIR和DSC对产物的微观结构进行了表征; 采用上转换荧光光谱(PL)研究了该复合纳米凝胶对pH值、 环境温度和不同金属离子的荧光响应行为, 并对相关机理进行了探讨. 结果表明, 环境温度变化对复合纳米凝胶的荧光发射具有显著影响, 且该复合纳米凝胶对Hg²⁺具有选择性荧光响应; 在H⁺或Hg²⁺作用下, 复合纳米凝胶中纳米晶和R6GHA之间会发生荧光共振能量传递; 通过纳米凝胶中纳米晶与R6GHA特征荧光发射峰比率的变化, 实现对Hg²⁺的检测.

Preparation of Complex Nanogel with Up-conversion Fluorescence-responsive Performance and Its Fluorescence Energy Transfer Behavior†

A functionalized NaYF₄∶Yb³⁺,Er³⁺ nanocrystal was prepared by hydrothermal method and decorated with 3-benzylsulfanylthio-carbonylsufanylpropionic acid(BSPA). Moreover, vinyl functional Rhodamine 6G monomer(R6GHA) was synthesized from rhodamine 6G(R6G) by a series of chemical reactions. Then, a novel complex fluorescent nanogel of NaYF₄∶Yb³⁺,Er³⁺/PNIPAm-co-R6GHA, which possesses multiple response, was prepared by reversible addition-fragmentation chain transfer(RAFT) polymerization and click reaction. In the as-prepared complex fluorescent nanogels, the functionalized nanocrystal and R6GHA form donor/receptor pairs of fluorescence resonance energy transfer(FRET). The microstructure of the nanogels was characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR) and differential scanning calorimeter(DSC). The fluorescence response of the nanogel to pH value, ambient temperature and different metal ions were investigated by photoluminescence(PL) and the mechanism was discussed in detail. The results show that fluorescence emission of the nanogels is influenced greatly by environmental temperature, and the composite nanogels have selective fluorescence response to Hg²⁺. In the presence of H⁺ or Hg²⁺, energy can transfer from the nanocrystals to R6GHA moieties under 980 nm excitation. The detection of the concentration of Hg²⁺ can be achieved by the change of intensity ratio of characteristic fluorescence emission peaks of nanocrystals and R6GHA moieties.