title: Stimuli-Responsive Polyoxometalate/Ionic Liquid Supramolecular Spheres: Fabrication, Characterization, and Biological Applications.
abstract: We report fabrication, characterization, and potential applications of polyoxometalate (POM)/ionic liquid (IL) supramolecular spheres in water for the first time. These supramolecular spheres have highly ordered structures and show excellent reversible self-assembly and tunable photoluminescence properties, which can be manipulated by adjusting pH of the aqueous solution. Specifically, the formation of POM/IL supramolecular spheres results in quenching of fluorescence emitted by Eu-POM because hopping of the d1 electron in the POM molecule is blocked by hydrogen bond existing between the oxygen atom of POM and the carboxylic acid group of IL. However, the fluorescence can be completely recovered by gradually increasing pH of the aqueous solution due to the pH-induced deprotonation of the carboxylic acid group of IL, which results in disassembly of the fabricated supramolecular spheres. Applications of these stimuli-responsive photoluminescent POM-based supramolecular materials are demonstrated in biological media. Dual signaling responses of turbidity and fluorescence are observed simultaneously in the detection of urease and heavy metals based on pH-induced disassembly of the supramolecular spheres during the biochemical events in aqueous solution. In addition, guest molecules are encapsulated into the supramolecular spheres, and controlled release of these entrapped molecules is demonstrated in the presence of external stimuli. This study shows potential of stimuli-responsive POM/IL supramolecular materials in biological applications.
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan 250100, P. R. China.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Chemistry, University of Houston , Houston, Texas 77204, United States.
authors.forename: Qiongzheng
authors.initials: Q
authors.lastname: Hu
authors.affiliation: Nano Institute of Utah and Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.affiliation: Nano Institute of Utah and Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Ling
authors.initials: L
authors.lastname: Zang
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan 250100, P. R. China.
authors.forename: Li
authors.initials: L
authors.lastname: Yu
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D003692:Delayed-Action Preparations / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D049449:Luminescence; D008163:Luminescent Measurements; D019216:Metals, Heavy / Q000032:analysis; D015394:Molecular Structure; D055668:Photochemical Processes; D012996:Solutions; D055672:Static Electricity; D017973:Tungsten Compounds / Q000737:chemistry*; D014510:Urease / Q000032:analysis; D014867:Water / Q000737:chemistry; D000099294:Polyoxometalates
chemical_list: D002264:Carboxylic Acids; D003692:Delayed-Action Preparations; D052578:Ionic Liquids; D019216:Metals, Heavy; D012996:Solutions; D017973:Tungsten Compounds; D014510:Urease; D014867:Water; C102296:polyoxometalate I; D000099294:Polyoxometalates