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When studying electrochemical oxygen reduction reactions in homogeneous media, special attention must be given to the significant background activity present with conventional electrode materials. The intrinsic electrocatalytic activity of different materials can be investigated using complementary methods, such as the rotating ring-disc electrode (RRDE) technique and chronoamperometric electrolysis with product quantification. This report presents a detailed investigation of the electrocatalytic ability of hydroxy anthraquinone derivatives and riboflavin towards hydrogen peroxide (H2O2) production viaa novel RRDE subtraction method together with chronoamperometric electrolysis. Qualitative trends linking the two methods were obtained, such as a higher excess current correlating with both higher productivity and selectivity. As such, a valuable tool is provided to increase the understanding of the electrocatalytic ability of homogeneous solutions toward improving the oxygen reduction reaction.

In this work we introduce in situ UV–Vis–NIR transmission spectroscopic ellipsometry as an alternative spectroelectrochemical method to examine the π-electron orbital structure as well as intra- and interchain order in regioregular poly(3-hexylthiophene) (rr-P3HT) during electrochemical doping. With the suggested technique, we measure the dielectric tensor of the P3HT film through a typical electrochemical cell consisting of a glass cuvette. The method provides a stable controlled electrochemical environment with full control on the applied potential during the ellipsometric measurement. P3HT, which is a model semitransparent conducting polymer, undergoes a sequence of oxidation steps with increasing electrochemical potential. In the presented work, the doping is monitored up to a level where finally almost every second thiophene ring is positively charged. The reference free determination of the real and imaginary parts of the dielectric tensor components allows a quantitative analysis of resonance energies as well as the orientation dependent oscillator strength of interchain exciton and polaron resonances. This parameters are directly linked with (i) the intrachain structure, (ii) the degree of electron localization, (iii) the π–π stacking order, (iv) the average polymer orientation, and (v) the doping level. Additionally we could observe aggregation dependent doping efficiency. The film optical properties appear fully reversible upon the cyclic electrochemical doping which proves the stability of inter- as well as intramolecular structure while going through very high doping levels.

In the recent decade, CO2has increasingly been regarded not only as a greenhouse gas but even more as a chemical feedstock for carbon‐based materials. Different strategies have evolved to realize CO2utilization and conversion into fuels and chemicals. In particular, biological approaches have drawn attention, as natural CO2conversion serves as a model for many processes. Microorganisms and enzymes have been studied extensively for redox reactions involving CO2. In this review, we focus on monitoring nonliving biocatalyzed reactions for the reduction of CO2by using enzymes. We depict the opportunities but also challenges associated with utilizing such biocatalysts. Besides the application of enzymes with co‐factors, resembling natural processes, and co‐factor recovery, we also discuss implementation into photochemical and electrochemical techniques. In a fix: CO2has increasingly been regarded not only as a greenhouse gas but even more as a chemical feedstock. In particular, biological approaches for CO2conversion have drawn attention. Microorganisms and enzymes have been studied extensively for redox reactions involving CO2. In this review, we focus on monitoring nonliving biocatalyzed reactions for the reduction of CO2by using enzymes.

Developing efficient methods for capture and controlled release of carbon dioxide is crucial to any carbon capture and utilization technology. Herein we present an approach using an organic semiconductor electrode to electrochemically capture dissolved CO2in aqueous electrolytes. The process relies on electrochemical reduction of a thin film of a naphthalene bisimide derivative, 2,7-bis(4-(2-(2-ethylhexyl)thiazol-4-yl)phenyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NBIT). This molecule is specifically tailored to afford one-electron reversible and one-electron quasi-reversible reduction in aqueous conditions while not dissolving or degrading. The reduced NBIT reacts with CO2to form a stable semicarbonate salt, which can be subsequently oxidized electrochemically to release CO2. The semicarbonate structure is confirmed by in situ IR spectroelectrochemistry. This process of capturing and releasing carbon dioxide can be realized in an oxygen-free environment under ambient pressure and temperature, with uptake efficiency for CO2capture of ∼2.3 mmol g–1. This is on par with the best solution-phase amine chemical capture technologies available today.

Ellipsometric measurements in a wide spectral range (from 0.05 to 6.5 eV) have been carried out on the organic semiconducting polymer, poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene-vinylene] (MDMO-PPV), in both undoped and doped states. The real and imaginary parts of the dielectric function and the refractive index are determined accurately, provided that the layer thickness is measured independently. After doping, the optical properties show the presence of new peaks, which could be well-resolved by spectroscopic ellipsometry. Also for the doped material, the complex refractive index, with respect to the dielectric function, has been determined. The broadening of the optical transitions is due to the delocalization of polarons at higher doping level. The detailed information about the dielectric function as well as refractive index function obtained by spectroscopic ellipsometry allows not only qualitative but also quantitative description of the optical properties of the undoped/doped polymer. For the direct characterization of the optical properties of MDMO-PPV, ellipsometry turns out to be advantageous compared to conventional reflection and transmission measurements.

Herein, we report the effect of protonation on the electronic properties and the conductivity of a soluble derivative of polyazomethine, poly(1,4-(2,5-bisoctyloxy phenylenemethylidynenitrilo)-1,4-phenylenenitrilomethylidyne), BOO-PPI. Following protonation, a marked change in electronic structure occurs, as evidenced by a bathochromic shift in visible absorption and the appearance of a broad absorption in the infrared coupled with new infrared active vibrational modes, signaling the appearance of a new electronic state. In other conjugated polymers, such features usually evidence the formation of mobile polarons on the polymer chain, leading to an increase in electrical conductivity. Surprisingly, BOO-PPI protonation does not lead to such an increase. Protonation also does not result in an electron spin resonance signal. We propose a model for protonation inducing a charged state on the polymer chain with strongly limited delocalization accounting for the lack of the electron spin resonance signal and the missing conductivity. To our knowledge, this is the first time that spectral features usually corresponding to mobile charges in organic materials do not correspond to an actual change in conductivity.

Positively and negatively charged states in cPBEBT, which consists of EDOT/benzotriazole/EDOT as the building block, are studied using CV, in situ UV‐Vis, and FTIR‐ATR spectroscopy. The results show that cPBEBT is an ambipolar D‐A‐type polymer capable of conducting both holes and electrons. The injected positive and negative charges are distributed over the whole polymer backbone, which is proven by in situ FTIR‐ATR where spectral signatures associated with the benzotriazole unit are observed in both p‐ and n‐doped cPBEBT. HOMO and LUMO values obtained from CV and FTIR‐ATR experiments during oxidation and reduction are compared. cPBEBT is an example of the D‐A approach towards the improvement of the electronic properties of the resultant polymer.

D‐A‐D‐type polymers are of high interest in the field of photovoltaics and electrochromism. In this study we report the synthesis and electrochemical properties of PPyBT along with its photophysical properties and photovoltaic performance. PPyBT is soluble in common organic solvents and both n‐ and p‐type dopable, which is a desired property for conjugated polymers. During electrochemistry studies, the onset potentials of the polymer were determined as +0.2 V for oxidation and −1.4 V for reduction. Using these values, HOMO and LUMO energy levels were calculated. The photovoltaic properties of PPyBT were also studied. PL studies showed that there is a charge transfer between PPyBT (donor) and PCBM (acceptor).

Electrochemical capture of carbon dioxide (CO2) using organic quinones is a promising and intensively studied alternative to the industrially established scrubbing processes. While recent studies focused only on the influence of substituents having a simple mesomeric or nucleophilicity effect, we have systematically selected six anthraquinone (AQ) derivatives (X-AQ) with amino and hydroxy substituents in order to thoroughly study the influence thereof on the properties of electrochemical CO2capture. Experimental data from cyclic voltammetry (CV) and UV–Vis spectroelectrochemistry of solutions in acetonitrile were analyzed and compared with innovative density functional tight binding computational results. Our experimental and theoretical results provide a coherent explanation of the influence of CO2on the CV data in terms of weak and strong binding nomenclature of the dianions. In addition to this terminology, we have identified the dihydroxy substituted AQ as a new class of molecules forming rather unstable [X-AQ-(CO2)n]2–adducts. In contrast to the commonly used dianion consideration, the results presented herein reveal opposite trends in stability for the X-AQ-CO2•–radical species for the first time. To the best of our knowledge, this study presents theoretically calculated UV–Vis spectra for the various CO2-AQ reduction products for the first time, enabling a detailed decomposition of the spectroelectrochemical data. Thus, this work provides an extension of the existing classification with proof of the existence of X-AQ-CO2species, which will be the basis of future studies focusing on improved materials for electrochemical CO2capture.

Solid state dye sensitized solar cells have been fabricated using a ruthenium dye complex, RuL2(NCS)/TBA(2:2) (where L= 2,2'-bipyridyl-4,4'-dicarboxylic acid; TBA= tetrabutylammonium), as a sensitizer and poly(3- hexylthiophene) (P3HT) as a hole transporting layer with TiO2 electrodes as electron transporting layers. We have studied the photovoltaic properties of P3HT/dye coated TiO2 electrodes and P3HT coated TiO2 electrodes with and without using compact TiO2 layers. The compact TiO2 layer improved the photovoltaic performance of the devices.

New donor–acceptor materials based on a polynorbornene framework to which both phthalocyanine and C60electroactive pendant units are randomly attached have been prepared in good yield by ring‐opening‐metathesis polymerization (ROMP) in the presence of a Grubbs catalyst. A structurally related phthalocyanine homopolymer was also synthesized for comparison. A remarkable fluorescence quenching was observed in the homopolymer and accounts for Pc⋅⋅⋅Pc interactions along the polymeric framework. As expected, the fluorescence quenching increases in the case of the polynorbornenes containing both Pc and C60units owing to photoinduced electron transfer, which was further confirmed by transient absorption spectroscopy. Finally, preliminary solar cell devices made of one of the copolymers were constructed.

The morphological stabilization of donor–acceptor blends for bulk heterojunction solar cells can be achieved by cross-linking of the small molecular phase in the polymer matrix using a polymerizable fullerene derivative. In a comparative study the morphology of polymer–fullerene blend films was investigated using poly3-hexylthiophene P3HT as the polymer and C61-butyric acid methyl ester PCBM or the newly synthesized polymerizable fullerene derivative, C61-butyric acid glycidol ester, PCBG, as the acceptor molecule, respectively. Changes in the nanomorphology due to heat treatment of the films were studied by means of atomic force microscopy AFM, transmission electron microscopy TEM and photoluminescence PL studies. The polymerization process was monitored with infrared absorption studies. As demonstrated by these comparative studies this newly synthesized fullerene gives considerable stabilization of the solid state morphology in these blends. Such prevention of the long term, high temperature instability of bulk heterojunction morphology displays an important route to increase the operational stability of plastic solar cells in future applications.

The photophysical properties of a new dyad molecule composed of a covalently linked Zn-phthalocyanine (antenna/donor) and a C₆₀ derivative (acceptor) have been investigated. We report experimental evidence of long-lived charge separation in the solid state with a lifetime several orders of magnitude higher than in solution. Such a long lifetime, unusual for phthalocyanine–fullerene dyads, is the basis for possible photovoltaic applications. A first demonstration of a working solar cell using phthalocyanine–fullerene dyads as the active material is presented. Though the power conversion efficiency under simulated solar illumination of 80 mW cm−2 is found to be moderate (0.02%), it is an encouraging result for application of C₆₀ dyad molecules to photovoltaics.

Summary.:  We report the synthesis and the spectroscopic properties of a novel soluble thiophene-based copolymer carrying pendant fullerene moieties (donor–acceptor double-cable polymer). Photoinduced absorption (PIA) experiments on spin cast films reveal a photoinduced electron transfer from the polythiophene chain onto the fullerene moieties. The performance of photovoltaic devices produced with this copolymer is also discussed.

A new series of regioregular poly(terthiophenes), bearing bis(thioether) side groups, has been prepared by electrochemical oxidation. Cyclic voltammetry of the parent trimers reveals an increase in electron donating ability in cyclic thioether derivatives. For example, one compound containing a central ethylenedithiothiophene (EDTT) unit gives two irreversible oxidation peaks which are significantly lower than the corresponding values for the structurally analogous bis(methylthio) derivative (ΔE_1ox = 170 mV, ΔE_2ox = 30 mV). The difference in oxidation potentials of each terthiophene in acetonitrile solution can be explained by examining the highest occupied molecular orbital (HOMO) energies. The electrochemical behaviour of the polymers illustrates the increase in p-doping ability of the EDTT-containing polymer. The cyclic voltammograms and electronic absorption spectra of the polymers show that the polymers containing cyclic thioether units have the lowest bandgap in the series (ca. 1.4 V and 1.5 eV, respectively). Photoinduced IR spectroscopy of poly(dithienyl-3,4-ethylenedithiothiophene) provides evidence of a long-living photoexcited charged state in the polymer.

Conjugated Polymers with a HOMO-LUMO transition <2 eV, i.e. a low bandgap, respectively, have interesting and desired properties for some thin film optoelectronic devices like light emitting diodes and solar cells. In this contribution we present the implementation of the novel copolymer PTPTB, consisting of alternating electron-rich N -dodecyl-2,5-bis(2′thienyl)pyrrole (TPT and electron-deficient 2,1,3-benzothiadiazole (B) units, in light emitting diodes (LEDs ) and photovoltaic devices. The LEDs show emission in the near infrared region, peaking at 800 nm. The electroluminescence yield can be significantly enhanced by blending with the wide bandgap polymer poly (para-phenylene-vinylene) derivative MDMO-PPV. Bulk heterojunction devices of PTPTB blended with the C 60 derivative PCBM shows AM 1.5 efficiencies around 1%. The low bandgap of PTPTB allows collecting photons up to 750 nm.

The reactions of an iron electrode in alkaline electrolytes of different concentrations are studiedin-situ using internal reflection and external reflection FTIR spectroscopy. Fe(OH)2 is formed during the reaction Fe(O) ? Fe(II) at all investigated concentrations. The product of the reaction Fe(II) ? Fe(III) isd-FeOOH in concentrated anda-FeOOH in diluted alkaline solutions.

The structure and the electrochemical oxidation reactions of polyaniline in an organic electrolyte are studied usingin-situ FTIR spectroscopy. In the first oxidation process a decrease of the N-H absorption band is observed, indicating a loss of hydrogen atoms. In the second oxidation step anion intercalation occurs. A broad absorption band at 4000 cm-1 is assigned to free carrier transitions in the conducting form of polyaniline.

The synthesis of a novel bithiophene with a pendant fullerene substituent and its electrochemical polymerisation are reported; light induced ESR measurements on the electrodeposited films reveal a photoinduced electron transfer from the donor cable (polythiophene) to the pendant acceptor cable (fullerene moieties).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Solid state dye sensitized solar cells have been fabricated using a ruthenium dye complex, RuL2(NCS)/TBA(2:2) (where L= 2,2′-bipyridyl-4,4′-dicarboxylic acid; TBA= tetrabutylammonium), as a sensitizer and poly(3- hexylthiophene) (P3HT) as a hole transporting layer with TiO2 electrodes as electron transporting layers. We have studied the photovoltaic properties of P3HT/dye coated TiO2 electrodes and P3HT coated TiO2 electrodes with and without using compact TiO2 layers. The compact TiO2 layer improved the photovoltaic performance of the devices.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.