Preparations And Properties Of Rhodamine-based Fluorescence Probes

With the rapid development of modern industry, more attentions about heavy metal pollution problems have been concerned. Especially, mercury pollution pervades the globe and remains a danger to human health and the environment. Moreover, ionic mercury can be converted into methyl mercury by bacteria in the environment, which subsequently bioaccumulates through the food chain. Most importantly, Hg²⁺ has a high a nity for thiol groups of proteins and enzymes and causes the dysfunction of the cell, brain, kidney, and central nervous system. Therefore, a convenient and rapid method for the determination, especially on-site or in real-time analysis, of mercury in biological and environmental samples is urgent.Fluorescence sensors were used to detect mercuric ions due to their good selectivity, high sensitivity, and instantaneous response. The spirocyclic forms of rhodamine derivatives are non-fluorescent and colorless, whereas the ring-opening of these derivatives induced by metal ions gives rise to strong fluorescence. So, it can be used to detect the heavy metal ions.But rhodamine derivativespossessbad water soluble. In order to improve their water soluble, we added poly?N-isopropylacrylamide??PNIPAM? to rhodamine derivatives. Herein, we synthesizedtwo types of water soluble fluorescence probesRh6g-S-Br-PNIPAM and Rh6g-S-PNIPAMvia the ways of Atom Transfer Radical Polymerization?ATRP? and Reversible Addition-Fragmentation Chain Transfer Polymerization?RAFT?, respectively. The structures of products were characterized by FT-IR, 1HNMR and gel permeation chromatography?GPC?. And the UV-visible spectroscopy and fluorescence spectroscopy were used to study the properties of water soluble fluorescence probes in detectingHg²⁺.The results indicated that the two fluorescence probes had a significant absorption and fluorescence enhancement when wehad only added mercury ions to the fluorescent probe solutions, which indicated that they hadgood specificity for mercury ions among many metal ions. As we all know, PNIPAM is a macromolecule with water-soluble and thermosensitivity, so the fluorescence probes with PNIPAM can detect Hg²⁺ in a fully aqueous environment and we can recycle and reuse them due to the temperature-sensitive of PNIPAM. In addition,polymer Rh6g-S-PNIPAM had low detection limit for detecting Hg²⁺.Therefore,fluorescent probe Rh6g-S-PNIPAMhad agreat application in theenvironment in terms of detecting Hg²⁺.