Design, Synthesis, and Theoretical Studies on the Benzoxadiazole and Thienopyrrole Containing Conjugated Random Copolymers for Organic Solar Cell Applications.

In this study, six different donor-π-acceptor1-π-donor-acceptor2 type random co-polymers containing benzodithiophene as a donor, benzooxadiazole (BO), and thieno[3,4-c]pyrrole-4,6-dione (TPD) as acceptor, have been synthesized and characterized. In addition to the acceptor core ratio at different values, the effect of aromatic bridge structures on the optical, electronic, and photovoltaic properties of six different random co-polymers is investigated by using thiophene and selenophene structures as aromatic bridge units. To investigate how the acceptor unit ratio and replacement of aromatic bridge units impact the structural, electronic, and optical properties of the polymers, density functional theory (DFT) calculations are carried out for the tetramer models. The open-circuit voltage (VOC), which is strongly correlated with the HOMO levels of the donor material, is enhanced with the increasing ratio of the TPD moiety. On the other hand, the short-circuit current (JSC), which is associated with the absorption ability of the donor material, is improved by the increasing ratio of BO moiety with the π-bridges. BO moiety dominant selenophene π-bridged co-polymer (P4) showed the best performance with a power conversion efficiency (PCE) of 6.26%, a JSC of 11.44 mA cm2, a VOC of 0.80 V, and a fill factor (FF) of 68.81%.

Innovative polymer engineering for the investigation of electrochemical properties and biosensing ability.

Subtle engineering for the generation of a biosensor from a conjugated polymer with the inclusion of fluorine-substituted benzothiadiazole and indole moieties is reported. The engineering includes the electrochemical copolymerization of the indole-6-carboxylic acid (M1) and 5-fluoro-4,7-bis(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (M2) on the indium tin oxide and graphite electrode surfaces for the investigation of both their electrochemical properties and biosensing abilities with their copolymer counterparts. The intermediates and final conjugated polymers, Poly(M1) [P-In6C], Poly(M2) [P-FBTz], and copoly(M1 and M2) [P-In6CFBTz], were entirely characterized by 1H NMR, 13C NMR, CV, UV-Vis-NIR spectrophotometry, and SEM techniques. HOMO energy levels of electrochemically obtained polymers were calculated from the oxidation onsets in anodic scans as -4.78 eV, -5.23 eV, and -4.89 eV, and optical bandgap (Egop) values were calculated from the onset of the lowest-energy π-π* transitions as 2.26 eV, 1.43 eV, and 1.59 eV for P-In6C, P-FBTz, and P-In6CFBTz, respectively. By incorporation of fluorine-substituted benzothiadiazole (M2) into the polymer backbone by electrochemical copolymerization, the poor electrochemical properties of P-In6C were remarkably improved. The polymer P-In6CFBTz demonstrated striking electrochemical properties such as a lower optical band gap, red-shifted absorption, multielectrochromic behavior, a lower switching time, and higher optical contrast. Overall, the newly developed copolymer, which combined the features of each monomer, showed superior electrochemical properties and was tested as a glucose-sensing framework, offering a low detection limit (0.011 mM) and a wide linear range (0.05-0.75 mM) with high sensitivity (44.056 µA mM-1 cm-2).

Electrochemical biosensor based on three components random conjugated polymer with fullerene (C60).

Herein, a conjugated polymer and fullerene bearing architecture-based electrochemical Tyrosinase (Tyr) enzyme inhibition biosensor for indomethacin (INDO) drug active compound has been developed. For this purpose, three moieties of benzoxadiazole, thienopyrroledione, and benzodithiophene containing conjugated polymer; poly[BDT-alt-(TP;BO)] was used as a transducer modifier together with fullerene for catechol detection. The specific combination of these materials is considered an effective way to fabricate highly sensitive and fast response catechol biosensors for the first time. Electrochemical and surface characteristics of the modified electrodes were obtained by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, and atomic force microscopy. The effect of the parameters during chronoamperometric measurements on the biosensor response was also studied. Using optimized conditions, biosensing of catechol was achieved between 0.5 and 62.5 µM with a limit of the detection 0.11 µM. Tyr inhibition was followed with INDO drug active compound and it was found that INDO has a mixed type characteristic of enzyme kinetics with an I50 value of 15.11 µM.

Associative behaviour and effect of functional groups on the fluorescence of graphene oxide.

We have juxtaposed the structural, vibrational and emission properties of graphene oxide (GO) with various degrees of reduction with and without a model dispersant, unveiling a strong associative behavior between GO sheets and the influence of H-bonds. The interlayer spacings are ∼0.84 and 0.78 nm for the as prepared and reduced samples. -OH groups are predominantly effected by the photo-thermal reduction. Also we note some regeneration of [double bond splayed left]C[double bond, length as m-dash]O and -COOH groups in reduced samples. Clear changes to the phonon density of states indicated the doping effects due to H-bonds via the oxygeneous groups. Importantly, the defect related Raman bands are rather prone to the effect of dispersant, unveiling their intrinsic nature. In the context of fluorescence, internal vibration relaxation mediated by CC stretch vibrations emphasized the localized nature of sp2 domains of relatively smaller size. Fluorescence consists of 6 components, where the higher energy components are more influenced due to H-bonds than those of the lower energy regime, attributed to their associative behavior and chemical functionality, respectively. Excitation dependent fluorescence measurements indicated a range of optical gaps from ∼3.5 to 2 eV. The associative behavior of GO and rGO with and without a dispersant provides crucial insights into the fundamental understanding of various molecular processes.

A novel and effective surface design: conducting polymer/ß-cyclodextrin host-guest system for cholesterol biosensor.

The combination of supramolecules and conducting polymers (CPs) has gained much attention for the development of new immobilization matrices for biomolecules. Herein, an amperometric biosensor based on a novel conducting polymer, poly(2-(2-octyldodecyl)-4,7-di(selenoph-2-yl)-2H-benzo[d][1,2,3]triazole)) (PSBTz) and ß-cyclodextrin (ß-CD) for the detection of cholesterol, was constructed. The PSBTz film with ß-CD was deposited on a graphite electrode by electropolymerization technique to achieve a suitable matrix for enzyme immobilization. Moreover, to justify the immobilization, alkyl chain containing conducting polymer (PSBTz) was designed, synthesized and electrochemically polymerized on the transducer surface. Alkyl chains in the structure of SBTz and hydroxyl groups of ß-CD contributed to effective immobilization while protecting the suitable orientation of the biomolecule. Cholesterol oxidase (ChOx) was covalently immobilized onto the modified surface using N,N'-carbonyldiimidazole (CDI) as the cross-linking agent. After successful immobilization, amperometric biosensor responses were recorded at −0.7 V vs Ag/AgCl in phosphate buffer (pH 7.0). The apparent Michaelis-Menten constant (KM(app)), maximum current (Imax), limit of detection (LOD), and sensitivity values were determined: 28.9 µM, 12.1 µA, 0.005 µM, and 5.77 µA/µM cm(2), respectively. The fabricated biosensor was characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. Finally, the prepared biosensor was successfully applied for the determination of cholesterol in blood samples.

Transparent and flexible supercapacitors with single walled carbon nanotube thin film electrodes.

We describe a simple process for the fabrication of transparent and flexible, solid-state supercapacitors. Symmetric electrodes made up of binder-free single walled carbon nanotube (SWCNT) thin films were deposited onto polydimethylsiloxane substrates by vacuum filtration followed by a stamping method, and solid-state supercapacitor devices were assembled using a gel electrolyte. An optical transmittance of 82% was found for 0.02 mg of SWCNTs, and a specific capacitance of 22.2 F/g was obtained. The power density can reach to 41.5 kW · kg(-1) and shows good capacity retention (94%) upon cycling over 500 times. Fabricated supercapacitors will be relevant for the realization of transparent and flexible devices with energy storage capabilities, displays and touch screens in particular.

Preparation of metallic line patterns from functional block copolymers.

A simple route for the preparation of nanoscopic metallic line patterns from functional block copolymers (BCPs) containing poly(2-vinylpyridine) or poly(methyl methacrylate) blocks is demonstrated. The time evolution of the surface morphologies of BCP thin films exposed to solvent vapors is studied to optimize the conditions for generating BCP microdomains oriented parallel or normal to the substrate. BCP templates are prepared by film reconstruction or by removal of one of the copolymer microdomains, depending on the properties of the functional BCPs. Finally, metallic line patterns are prepared by either electrochemical etching or direct metal deposition and lift-off processes using the BCP templates.