Synthesis and photophysical characterization of the free-radical copolymerization of metaloquinolate-pendant monomers with methyl methacrylate

A Facile Fabrication of CdSe/ZnS QDs-Block Copolymer Brushes-Modified Graphene Oxide Nanohybrid with Temperature-Responsive Behavior

In this paper, we described a straightforward one-step chemical method for the synthesis of semiconductor quantum dots(QDs)-block copolymer brushes functionalized graphene oxide(GO) fluorescence nanohybrids. The azobenzene-terminated block copolymer poly(N-isopropylacrylamid)-b-poly(styrene-co-5-(2-methacryoylethyloxymethyl)-8-quinolinol)(PNIPAM-b-P(St-co-MQ)) was modified on the surface of GO sheets via host-guest interactions between β-cyclodextrin-modified GO and azobenzene moieties, and simultaneously CdSe/ZnS QDs were integrated on the block copolymer brushes through the coordination between 8-hydroxyquinoline units in the polymer brushes and CdSe/ZnS QDs. The resulting fluorescence nanohybrid exhibited dual photoluminescence at 620 nm and 526 nm, respectively, upon excitation at 380 nm and LCST-type thermo-responsive behavior which originated from the change in the PNIPAM conformation in the block copolymer brushes of GO sheets.

A facile synthesis of multifunctional carbon dots as fluorescence 'turn on' and 'turn off' probes for selective detection of Al3+ and 2,4,6-trinitrophenol

Carbon dots (CDs) have drawn increasing interests due to their unique optical properties and promising application in various fields. In this study, citric acid (CA) and 5-chloromethyl-8-hydroxyquinoline (LQ) were used to synthesize nitrogen-doped CDs as novel fluorescent probes using a one-step solvothermal route. The as-prepared CDs had strong blue-white fluorescence emission when excited at 405 nm wavelength with a quantum yield (QY) of 25%, behaving with high ion concentration stability. Water-soluble CDs with a 8-hydroxyquinoline structure on their surface could be used to detect Al³⁺ using a 'turn on' mechanism and trinitrophenol (TNP) using a 'turn off' mechanism with detection limits of 229 nM and 44.4 nM, respectively. Al³⁺ enhances the fluorescence of CDs by forming a coordination complex to generate a fluorescence synergistic role and limit CD nonradiative transition. TNP quenched the fluorescence with high selectivity and sensitivity, which was attributed to the inner filter effect and static quenching. These results indicated that these CDs with their unique 'turn on' and 'turn off' nature have potential application in the environmental protection field and in prevention of terrorist threats.

Size-controllable preparation and antibacterial mechanism of thermo-responsive copolymer-stabilized silver nanoparticles with high antimicrobial activity

The emergence of bacterial resistance has become one of the top global concern, and silver nanoparticles (AgNPs) provide alternative strategies for the development of new antimicrobial agent. Herein, three small sizes (1.5-4.0 nm) of well-dispersed AgNPs were successfully synthesized using a thermo-sensitive P(NIPAM-co-MQ) copolymer with coordination ability as a stabilizer. The copolymer stabilized silver nanoparticles (AgNPs@P) displayed good thermo-sensitive characteristics and solution stability at pH = 6.5-8.0. AgNPs@P had high-efficiency and long-term antimicrobial properties for Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli). In particular, AgNPs@P₃ with ultrasmall size (1.59 nm) exhibited better antimicrobial activity against both normal bacteria and antibiotic-resistant bacteria with a very low MIC value of 4.05 μg/mL. Moreover, AgNPs@P also showed an interesting temperature-dependent antibacterial activity mainly owing to the effect of thermo-sensitive copolymer on AgNPs. It was found that the antibacterial activity of the AgNPs@P also was affected by the proportion of copolymer, sizes of AgNPs, and experimental temperature. The antibacterial mechanism of AgNPs@P involved a variety of ways including destroying cell membranes, internalization of AgNPs and generation of ROS. Our research provides a new perspective for the preparation of effective nanosilver antimicrobial agents.

Preparation of a temperature-responsive block copolymer-anchored graphene oxide@ZnS NPs luminescent nanocomposite for selective detection of 2,4,6-trinitrotoluene

Thermo-sensitive block copolymer decorated GO@ZnS NPs nanocomposite was constructed via π–π stacking interaction as a robust fluorescent sensing platform for the selective detection of TNT.

Temperature-dependent catalytic reduction of 4-nitrophenol based on silver nanoclusters protected by a thermo-responsive copolymer ligand

A facile strategy is developed for fabricating novel nanocatalysts of Ag NCs protected with a temperature-responsive copolymer ligand containing 8-hydroxyquinoline and isopropylacrylamide segments.

A facile construction of Au nanoparticles on a copolymer ligand brushes modified graphene oxide nanoplatform with excellent catalytic properties

Au NPs were generated via in situ reduction on copolymer brush P(OEGMA-co-MQ) functionalized GO. MQ units in the brushes as capping agents could stabilize the Au NPs. The Au NPs–GO hybrid exhibited high catalytic activity for the reduction of 4-NP.

Electronic tuning of ruthenium complexes by 8-quinolate ligands

A series of Ru(II) complexes were synthesized with the deprotonated forms of the ligands 8-hydroxyquinoline (quo(-)) and 5-NO(2)-8-hydroxyquinoline (5-NO(2)-quo(-)) as analogs to the prototypical complex [Ru(bpy)(3)](2+) (bpy = 2,2'-bipyridine). Electrochemistry, spectroscopy and density functional theory calculations were utilized to investigate the electronic tuning of the occupied t(2g)-type orbitals of the metal center with variation in the ligation sphere. The maximum of the lowest energy absorption of complexes containing one, two and three 8-quinolate ligands progressively redshifts from 452 nm in [Ru(bpy)(3)](2+) to 510 nm in [Ru(bpy)(2)(quo)](+), 515 nm in [Ru(bpy)(quo)(2)] and 540 nm in [Ru(quo)(3)](-) in water. This bathochromic shift results from the increase in energy of the occupied t(2g)-type orbital across the series afforded by coordination of each subsequent quo(-) ligand to the Ru(II) center. Time-dependent density functional theory calculations along with electrochemical analysis reveals that the lowest energy transition has contributions in the highest occupied molecular orbital from both the quo(-) ligand and the metal, such that the lowest energy transition is not from an orbital that is purely metal-centered in character as in [Ru(bpy)(3)](2+).