Novel soluble conjugated random copolymers are synthesized by palladium-catalyzed Suzuki coupling reaction from 9,9-dioctylfluorene (DOF) and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (DHTBT) with DHTBT composition varying from 1 to 50 mol % in the copolymer. All of the polymers are soluble in common organic solvents and are highly photoluminescent. Polyfluorene fluorescence is quenched completely at a DHTBT concentration as low as 1% in the solid film. The copolymer films are highly fluorescent under UV irradiation in contrast to its parent analogue, 4,7-di(thien-2-yl)-2,1,3-benzothiadiazole (PFO−DBT), without alkyl substitution on thiophene rings. Devices made up of these copolymers emit saturated red light. The emission peaks are shifted from 613 to 672 nm when the DHTBT content increases from 1 to 50%. The highest external quantum efficiency achieved in the device configuration ITO/PEDT/PVK/PFO−DHTBT/Ba/Al is 2.54% with luminous efficiency 1.45 cd/A for the copolymer with emission peak at 638 nm for 10% DHTBT content, among the highest values so far reported for saturated red polymer emitters.

Low band-gap, soluble conjugated copolymers were synthesized from 9,9-dioctylfluorene and 4,7-di-2-thienyl-2,1,3-benzothiadiazole (PFO-DBT) and different composition ratios were used for the donor material in bulk heterojunction polymer photovoltaic cells (PVCs). In PVCs made with PFO-DBT:PCBM (methano-fullerene [6,6]-phenyl C61-butyric acid methyl ester) blends, the spectral response is extended up to 650 nm and the open-circuit voltage (Voc) is improved to 0.95 V. The energy conversion efficiency (ηe) in devices with optimized composition reaches 2.24% under an AM1.5 solar simulator (78.2 mW/cm2). In contrast to organic PVCs previously published, these PVCs retain high energy conversion efficiency at illumination up to 5 suns of AM1.5 spectral illumination. This feature allows high efficiency polymer PVC modules made in combination with a light concentrator.

A series of [6,6]-phenyl C61-butyric acid esters, including methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) with different alkyl chain lengths (C1−C16) was synthesized from the reaction of C60 and alkyl 4-benzoylbutyrate p-tosylhydrazone in the presence of sodium methylate. The solubility of C60 derivatives in organic solvents increased with the increase in the length of alkyl substitutions. Photovoltaic cells with these derivatives were fabricated with the structure of ITO/PEDT/MEH−PPV + C60 derivatives/Ba/Al. Device performances with such PCBM analogues were investigated and discussed in terms of Donor/Acceptor (D/A) phase separation and mobility of acceptor phase. The results clearly indicate that both interfacial properties of the two phases (donor and acceptor) and mobility of electrons and holes within corresponding phases play an important role in the efficiencies of PV cells. This study revealed that methanofullerenes [6,6]-phenyl C61-butyric acid butyl ester, PCBB, possesses better photosensitivity than the PCBM, a widely investigated and well-recognized C60 derivative for polymer PV cells The energy conversion efficiency reaches 2.84% for PCBB under AM1.5 illumination (78.2 mW/cm2), but 2.0% for PCBM fabricated in the same conditions.

We report here on the electroreduction of p-benzoquinone (BQ) or H2O2 as a new trigger for simple, fast, uniform, and controllable electrodeposition of chitosan (CS) hydrogels and biosensing nanocomposite films of CS, multiwalled carbon nanotubes (MWCNTs), and glucose oxidase (GOD). The multiparameter electrochemical quartz crystal microbalance (EQCM) based on crystal electroacoustic impedance analysis was used to dynamically monitor the deposition processes. When the EQCM Au electrode was immersed in a weakly acidic solution (here pH 5.1 acetic buffer) containing BQ (or H2O2) and CS, the proton consumption during BQ (or H2O2) electroreduction increased the local solution pH near the electrode surface and led to the deposition of CS hydrogel on the electrode surface at local pH near and above the pKa value of CS. The concentration of BQ (or H2O2) required for CS electrodeposition was theoretically evaluated based on an electrogenerated base-to-acid titration model and supported by experiments. Co-deposition of GOD and MWCNTs with the CS hydrogel was achieved, and the resulting MWCNTs-CS-GOD nanocomposite films were demonstrated for glucose biosensing. The MWCNTs-CS-GOD enzyme electrode prepared by BQ reduction exhibited a current sensitivity of 6.7 microA mM-1 cm-2 to glucose, and the linear range for glucose detection at 0.7 V vs SCE was from 5 microM to 8 mM, with a detection limit of 2 microM and a Michaelis-Menten constant of 6.8 mM. The BQ-electroreduction protocol exhibited the best sensor performance, as compared with H2O2-reduction and previously reported water-reduction values. The present protocol via electroreduction of a deliberately added oxidant that is accompanied by a local pH change is highly recommended for wider applications in pH-dependent deposition of other films.

A protocol of one-pot chemical preoxidation and electropolymerization of monomers (CPEM) in enzyme-containing aqueous suspensions (or solutions) was proposed as a universal strategy for high-activity and high-load immobilization of enzymes to construct amperometric biosensors, which was proven to be effective for the monomer of 1,4-benzenedithiol (BDT), 1,6-hexanedithiol, o-phenylenediamine, o-aminophenol or pyrrole, the preoxidant of K3Fe(CN)6 or p-benzoquinone, and the enzyme of glucose oxidase (GOx) or alkaline phosphatase (AP) to develop GOx-based glucose biosensors or AP-based disodium phenyl phosphate biosensors. As a case examined in detail, a well-dispersed aqueous suspension of the poorly soluble BDT was obtained through its dispersion assisted by ultrasonication and coexisting GOx, which was then subject to chemical preoxidation through adding K3Fe(CN)6, yielding many composites of insoluble BDT oligomers with lots of high-activity enzyme molecules entrapped. Some insoluble composites were then electrochemically codeposited with poly(1,4-benzenedithiol) on an Au electrode, yielding an enzyme film with high-load and high-activity enzyme immobilized. The glucose biosensor prepared here from the CPEM protocol showed much better performance than that from the preoxidant-free conventional electropolymerization (CEP) protocol, with a detection sensitivity increase by a factor of 32 in this case. The GOx-based and AP-based first-generation biosensors developed from the present CPEM protocol all exhibited notably improved performance compared with the analogues from the preoxidant-free CEP protocol. The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate various electrode modification processes. The values of quantity and enzymatic specific activity (ESA) of the immobilized enzymes were evaluated through the EQCM and the conventional UV-vis spectrophotometric method, given that the CPEM protocol notably improved the quantity and the ESA of immobilized enzymes as compared with the preoxidant-free CEP protocol. The proposed CPEM protocol may be interesting in a number of fields, including biosensing, biocatalysis, biofuel cells, bioaffinity chromatography, and biomaterials, and the successful electropolymerization of dithiols in aqueous suspensions (two-phase electropolymerization) may open a new avenue for many monomers that are poorly soluble in neutral aqueous solutions to in situ immobilize biomolecules for bioapplications.