基于温敏性有机/无机杂化纳米粒子的比率型Hg^(2+)荧光探针

Ratiometric Sensor for Hg^(2+) Ions Based on Thermo-responsive Organic/Inorganic Hybrid Nanoparticles

基于有机/无机杂化纳米粒子制备了能够对汞离子(Hg^(2+))进行比率型检测的荧光探针.首先通过连续的可逆加成-断裂链转移(RAFT)聚合合成了两亲性嵌段聚合物,P(MPS-co-NBDAE)-b-P(NIPAM-co-Rh BHA).其疏水嵌段为带有三甲基硅氧烷侧基,并标记有荧光能量给体N-(7-硝基-2,1,3-苯并噁二唑)(NBD)基元的聚丙烯酸酯,P(MPS-co-NBDAE);亲水嵌段为共聚有潜在荧光能量受体罗丹明脲衍生物单体(Rh BHA)的温敏性聚(N-异丙基丙烯酰胺),P(NIPAM-co-Rh BHA).由该嵌段聚合物自组装形成的胶束在三乙胺催化作用下水解发生溶胶-凝胶化过程后,得到核交联的有机/无机杂化纳米粒子.在没有Hg^(2+)离子存在时,该杂化纳米粒子溶液只显示出NBD基元发射的绿光;而在有Hg^(2+)离子存在条件下,Hg^(2+)离子可诱导Rh BHA开环为具有荧光发射性能的Rh B基元.由于NBD与Rh B之间的荧光共振能量转移(FRET)效应,杂化纳米粒子溶液的颜色和荧光发射性能均会发生明显的变化,从而实现对水溶液中Hg^(2+)离子的高效选择性检测.而且,升高温度会导致纳米粒子壳层PNIPAM嵌段的塌缩,使NBD和Rh B基元间的空间距离缩短,可进一步提高检测效果.因此,基于该有机/无机杂化纳米粒子的检测体系可用来对Hg^(2+)离子进行高效选择性检测.

A ratiometric fluorescent probe for Hg^2＋ions in aqueous media based on organic/inorganic hybrid nanoparticles was prepared. Amphiphilic diblock copolymer,poly（3-（trimethoxysilyl） propyl methacrylate-coNBDAE）-b-poly（N-isopropylacrylamide-co-Rh BHA）,abbreviated as P（MPS-co-NBDAE）-b-P（NIPAM-coRh BHA）,was firstly synthesized via consecutive reversible addition-fragmentation chain transfer（RAFT）polymerization of MPS and NIPAM monomer together with NBDAE and Rh BHA respectively,where NBDAE and Rh BHA were 7-nitro-2,1,3-benzoxadiazole（NBDAE）-based acrylic derivative monomer and Hg^2＋-reactive rhodamine B（Rh B）-based acrylamide derivative monomer,respectively. Upon exposure to aqueous media,the amphiphilic diblock copolymer of P（MPS-co-NBDAE）-b-P（NIPAM-co-Rh BHA） underwent selfassembly to form spherical nanoparticles with NBD-labeled PMPS cores and thermos-responsive PNIPAM coronas co-labeled with Rh BHA moieties. Then a sol-to-gel process was conducted via addition of trimethylamine（TEA） into the micellar solution as the catalyst,resulting in core-crosslinked organic/inorganic hybrid nanoparticels. In the absence of Hg^2＋ ions,the micellar solution of the hybrid nanoparticles was solely green emissive under UV irradiation,which was originated from the NBD moieties trapped in the crosslinked PMPS micellar cores. However,upon addition of Hg^2＋ions into the aqueous solution,Hg^2＋ induced ringopening of the lactam ring in Rh BHA moieties and thus generated Rh B residues capable of fluorescence emission. Due to the fluorescence resonance energy transfer（FRET） between NBD and Rh B moieties that were located in the micellar cores and coronas and acted as FRET donors and acceptors respectively,when the aqueous micellar solution was exposed to UV irradiation,a drastically green-to-orange emission transition was facilely discerned by both naked eye and fluorescence spectrometry,thus allowing for probing Hg^2＋ ions in a ratiometric manner. Moreover,because of the thermos-responsiveness of PNIPAM blocks,the collapse of PNIPAM coronas was induced by increasing the solution temperature,and the spatial distance between NBD and Rh B moieties was therefore shortened,leading to an enhanced probing sensitivity. As a result,the organic/inorganic nanoparticle-based fluorescent probe could be employed as a highly selective ratiometric fluorescent sensor for Hg^2＋in aqueous solution.