title: Metal-chelating and dansyl-labeled poly(N-isopropylacrylamide) microgels as fluorescent Cu2+ sensors with thermo-enhanced detection sensitivity.
abstract: We report on the fabrication of Cu2+-sensing thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) microgels labeled with metal-chelating acceptor and fluorescent reporter moieties. Cu2+ detection sensitivity can be considerably enhanced via thermo-induced collapse of the sensing matrix, which can easily optimize the relative spatial distribution of Cu2+-binding sites and fluorescence readout functionalities. A novel picolinamine-containing monomer with Cu2+-binding capability, N-(2-(2-oxo-2-(pyridine 2-yl-methylamino)ethylamino)ethyl)acrylamide (PyAM, 3), was synthesized at first. Nearly monodisperse Cu2+-sensing microgels were prepared via emulsion polymerization of N-isopropylacrylamide (NIPAM) in the presence of a nonionic surfactant, N,N'-Methylene-bis(acrylamide) (BIS), PyAM (3), and fluorescent dansylaminoethyl- acrylamide (DAEAM, 5) monomers at around neutral pH and 70 degrees C. At 20 degrees C, as-synthesized microgels in their swollen state can selectively bind Cu2+ over other metal ions (Hg2+, Mg2+, Zn2+, Pb2+, Ag+, and Al3+), leading to prominent quenching of fluorescence emission intensity. Above the volume phase transition temperature, P(NIPAM-co-PyAM-co-DAEAM) microgels exhibit increased fluorescence intensity. It was observed that Cu2+ detection sensitivity can be dramatically enhanced via thermo-induced microgel collapse at elevated temperatures. At a microgel concentration of 3.0x10(-6) g/mL, the detection limit drastically improved from approximately 46 nM at 20 degrees C to approximately 8 nM at 45 degrees C. The underlying mechanism for this novel type of sensor with thermotunable detection sensitivity was tentatively proposed.
authors.affiliation: CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yin
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Guan
authors.forename: Di
authors.initials: D
authors.lastname: Wang
authors.forename: Shiyong
authors.initials: S
authors.lastname: Liu
mesh_terms: D000180:Acrylic Resins / Q000138:chemical synthesis / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D056246:Chemistry, Analytic / Q000295:instrumentation*; D003300:Copper / Q000032:analysis* / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D005782:Gels; D010713:Phosphatidylcholines / Q000737:chemistry*; D013696:Temperature
chemical_list: C496906:1-myristoyl-2-(12-((5-dimethylamino-1-naphthalenesulfonyl)amino)dodecanoyl)-sn-glycero-3-phosphocholine; D000180:Acrylic Resins; D002614:Chelating Agents; D005456:Fluorescent Dyes; D005782:Gels; D010713:Phosphatidylcholines; C052970:poly-N-isopropylacrylamide; D003300:Copper