Naime Akbasoglu Unlu

A novel promising biomolecule immobilization matrix: Synthesis of functional benzimidazole containing conducting polymer and its biosensor applications

In order to construct a robust covalent binding between biomolecule and immobilization platform in biosensor preparation, a novel functional monomer 4-(4,7-di(thiophen-2-yl)-1H-benzo[d]imidazol-2-yl)benzaldehyde (BIBA) was designed and successfully synthesized. After electropolymerization of this monomer, electrochemical and spectroelectrochemical properties were investigated in detail. To fabricate the desired biosensor, glucose oxidase (GOx) was immobilized as a model enzyme on the polymer coated graphite electrode with the help of glutaraldehyde (GA). During the immobilization step, an imine bond was formed between the free amino groups of enzyme and aldehyde group of polymer. The surface characterization and morphology were investigated to confirm bioconjugation by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) at each step of biosensor fabrication. The optimized biosensor shows good linearity between 0.02mM and 1.20mM and a low limit of detection (LOD) of 2.29μM. Kinetic parameters Km(app) and Imax were determined as 0.94mM and 10.91μA, respectively. The biosensor was tested for human blood serum samples.

Electrochemical Properties of Perylene Diimide (PDI) and Benzotriazole (Btz) Bearing Conjugated Polymers to Investigate the Effect of π-Bridge on Electrochemical Properties

In this study, a series of benzotriazole (BTZ) and perylene diimide (PDI) based copolymers; CoP1 and CoP2 were synthesized via Stille coupling. The effect of perylene diimide (PDI) unit on electrochemical properties of BTZ bearing polymers was investigated. In addition, two different π-bridges: thiophene and dithienopyrrole (DTP) were incorporated into polymer backbone to explore their effects on electrochemical and spectroelectrochemical properties of corresponding polymers; CoP1 and CoP2. Electrochemical and spectral results showed that while CoP1 has only n-type doping property CoP2 has an ambipolar character although p-type doping property is rare for PDI based polymers. Owing to the DTP group, CoP2 showed the lowest band gap reported up to now between perylene diimide derivatives. The effect of different π–bridges and perylene diimide (PDI) unit on the HOMO and LUMO energy levels, optical band gaps, switching time, and optical contrast were presented.

Selenophene as a Bridge in Molecular Architecture of Benzotriazole Containing Conjugated Copolymers to Gain Insight on Optical and Electrochemical Properties of Polymers

GRAPHICAL ABSTRACT Abstract Polymers containing selenophene as a π bridge; poly(2-(2-octyldodecyl)-4-(selenophen-2-yl)-7-(5-(thiophen-2-yl)selenophen-2-yl)-2H-benzo[d][1,2,3]triazole) (P1) and poly(2-(2-octyldodecyl)-4-(5-phenylselenophen-2-yl)-7-(selenophen-2-yl)-2H-benzo[d][1,2,3]triazole (P2) were synthesized via Stille and Suzuki coupling reactions, respectively. Optical and electrochemical properties were investigated and comparisons with their thiophene analogs were done. Selenophene substitution resulted in low band gap and red shifted absorption, fast switching times (less than 1 s) with reasonable optical contrast. Switching time of P2 was 0.2 second which is the fastest switching time regarding benzotriazole-based polymers. Photovoltaic properties of P1 and P2 were investigated. The optimized devices showed 0.45% and 0.75% power conversion efficiency, respectively.

Structure–property relations in donor–acceptor–donor type benzimidazole containing conjugated polymers

In order to gain deeper insight about structure–property relations properties, two novel donor–acceptor–donor type monomers were studied. 4′-Tert-butyl-4,7-di(thiophen-2-yl)spiro[benzo[d]imidazole-2,1′-cyclohexane] and 4,7-di(2,2′-bithiophen-5-yl)-4′-tert-butylspiro[benzo[d]imidazole-2,1′-cyclohexane] were synthesized and electrochemically polymerized. Electrochemical and optical properties of the polymers were investigated via cyclic voltammetry and UV–Vis–NIR spectroscopy techniques. It was found that changing donor unit from thiophene to bithiophene results in a drastic change in optical and electrochemical properties, especially in optical contrast.Graphical AbstractIn this study, we investigate the effect of conjugation on the properties of electrochemically synthesized polymers. For this purpose, 4,7-dibromo-4′-(tert-butyl)spiro[benzo[d]imidazole-2′-cyclohexane] was synthesized as an acceptor unit and coupled with two different donor units, namely thiophene and bitihophene. Their optical and electronic properties were compared and spectroelectrochemical studies showed that with increasing conjugation, absorption maxima is red shifted together with a decrease in the optical band gap.