A family of well-defined poly(3-hexylthiophene)-b-poly(5,8-di-p-tolylquinoxaline-2,3-diyl) rod–rod block copolymers was designed and synthesized in one pot via mechanistically distinct, sequential living polymerization using Ni(dppp)Cl2 as a single catalyst. The block copolymerization was demonstrated to proceed in a living/controlled chain-growth manner, affording the desired block copolymers in high yields with tunable compositions, controlled molecular weight, and narrow molecular weight distributions. The resulting block copolymer was revealed to self-assemble into various well-defined supramolecular structures depending on the solvents used such as nano-fibril and spherical nanoparticles. Very interestingly, such a block copolymer displayed highly selective visual detection for cobalt over most other competing metal ions by changing its orange color to light green and bright orange emission to deep green. The detection limit was estimated to be down to 1.0 × 10−7 M and the interference of the other competing metal ions is negligible. Furthermore, such a block copolymer can be applied using test strips, making it a practical, sensitive, and selective probe for cobalt ions.
Poly(5-hydroxytryptamine) (poly(5-HT)) is exploited as a new and efficient enzyme-immobilization matrix for amperometric and biofuel cell (BFC)-based biosensing. A GOx-poly(5-HT)-Pd nanoparticles (PdNPs) bionanocomposite is prepared by Na 2 PdCl 4 -initiated oxidized polymerization of 5-hydroxytryptamine (5-HT) in a neutral aqueous solution containing glucose oxidase (GOx), and this bionanocomposite and then chitosan (CS) are cast-coated on a Pd-plated Au electrode to yield a CS/GOx-poly(5-HT)-PdNPs/Pd plate /Au enzyme electrode. Scanning/transmission electron microscopy, UV–vis spectrophotometry and electrochemical quartz crystal microbalance are employed for material characterization and/or process monitoring. Under optimized conditions, the amperometric response of the enzyme electrode is linear with glucose concentration from 2.0 μM to 6.66 mM with a sensitivity of 110 μA mM −1 cm −2 , a limit of detection of 0.2 μM, and excellent operation/storage stability in the first-generation biosensing mode. The sensitivity is larger than those of some conventional electrodes under identical conditions. The enzyme electrode also works well in the second-generation biosensing mode. By using the enzyme electrode as the anode for glucose oxidation and a Pd plate /Au electrode as the cathode for KMnO 4 reduction, a monopolar BFC is constructed as a self-powered biosensor , the current response of which is linear with glucose concentration from 50 μM to 34.5 mM. Experiments also show that poly(5-HT) is a physical and chemical dual-immobilization matrix of enzyme, since the abundant amino groups in poly(5-HT) can be used for chemical bonding of GOx.
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