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Semi-biological photosynthesis combines synthetic photosensitizers with microbial catalysts to produce sustainable fuels and chemicals from CO 2 . However, the inefficient transfer of photoexcited electrons to microbes leads to limited CO 2 utilization, restricting the catalytic performance of such biohybrid assemblies. Here, we introduce a biological engineering solution to address the inherently sluggish electron uptake mechanism of a methanogen, Methanosarcina barkeri (M. barkeri), by coculturing it with an electron transport specialist, Geobacter sulfurreducens KN400 (KN400), an adapted strain rich with multiheme c-type cytochromes (c-Cyts) and electrically conductive protein filaments (e-PFs) made of polymerized c-Cyts with enhanced capacity for extracellular electron transfer (EET). Integration of this M. barkeri-KN400 co-culture with a synthetic photosensitizer, carbon nitride, demonstrates that c-Cyts and e-PFs, emanating from live KN400, transport photoexcited electrons efficiently from the carbon nitride to M. barkeri for methanogenesis with remarkable long-term stability and selectivity. The demonstrated cooperative interaction between two microbes via direct interspecies electron transfer (DIET) and the photosensitizer to assemble a semi-biological photocatalyst introduces an ecosystem engineering strategy in solar chemistry to drive sustainable chemical reactions., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Interfacial charge-transfer between perovskite and charge-transport layers plays a key role in determining performance of perovskite solar cells. The conventional viewpoint emphases the necessity of favorable energy-level alignment of the two components. In recent reports, efficient electron-transfer is observed from perovskite to fullerene-based electron-transport layers even when there are unfavorable energy-level alignments, but the mechanism is still unclear. Here, using an ultrafast in situ two-photon photoelectron spectroscopy, real-time observations of electron-transfer processes at CsPbI 3 /C 60 interface in both temporal and energetic dimensions are reported. Due to strong electronic coupling, a large amount of interfacial hybrid states is generated at the interfaces, aiding fast photoinduced electron-transfer in ≈124 fs. This process is further verified by nonadiabatic molecular dynamics simulations and transient absorption experiments. The short timescale explains why electron-transfer can overcome unfavorable energy-level alignments, providing a guideline for device design., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Precious metal complexes remain ubiquitous in photoredox catalysis (PRC) despite concerted efforts to find more earth-abundant catalysts and replacements based on 3d metals in particular. Most otherwise plausible 3d metal complexes are assumed to be unsuitable due to short-lived excited states, which has led researchers to prioritize the pursuit of longer excited-state lifetimes through careful molecular design. However, we report herein that the C-H arylation of pyrroles and related substrates (which are benchmark reactions for assessing the efficacy of photoredox catalysts) can be achieved using a simple and readily accessible octahedral bis(diiminopyridine) cobalt complex, [1-Co](PF 6 ) 2 . Notably, [1-Co] 2+ efficiently functionalizes both chloro- and bromoarene substrates despite the short excited-state lifetime of the key photoexcited intermediate *[1-Co] 2+ (8 ps). We present herein the scope of this C-H arylation protocol and provide mechanistic insights derived from detailed spectroscopic and computational studies. These indicate that, despite its transient existence, reduction of *[1-Co] 2+ is facilitated via pre-assembly with the NEt 3 reductant, highlighting an alternative strategy for the future development of 3d metal-catalyzed PRC., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Constructing green and sustainable advanced oxidation processes (AOPs) for the degradation of organic contaminants is of great importance but still remains big challenge. In this work, an effective AOP (MnFe 2 O 4 -activated periodate, MnFe 2 O 4 /PI) was established and investigated for the oxidation of organic contaminants. To avoid the severe aggregation of MnFe 2 O 4 nanoparticles, a hybrid MnFe 2 O 4 -biochar catalyst (MnFe 2 O 4 -BC) was further synthesized by anchoring MnFe 2 O 4 nanoparticles on chemically inert biochar substrate. Intriguingly, MnFe 2 O 4 -BC/PI exhibited different selectivity towards organic contaminants compared with MnFe 2 O 4 /PI, revealing that biochar not only served as the substrate, but also directly participated into the oxidation process. Electron-transfer mechanism was comprehensively elucidated to be responsible for the abatement of pollutants in both MnFe 2 O 4 /PI and MnFe 2 O 4 -BC/PI. The surface oxygen vacancies (OVs) of MnFe 2 O 4 were identified as the active sites for the formation of high potential complexes MnFe 2 O 4 -PI*, which could directly and indirectly degrade the organic pollutants. For the hybrid MnFe 2 O 4 -BC catalyst, biochar played multiple roles: (i) substrate, (ii) provided massive adsorption sites, (iii) electron-transfer mediator. The differences in selectivity of MnFe 2 O 4 /PI and MnFe 2 O 4 -BC/PI were determined by the adsorption affinity between biochar substrate and organics. Overall, the findings of this study expand the knowledge on the selectivity of PI-triggered AOPs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Covalent organic frameworks (COFs) are an ideal template to construct high-efficiency catalysts for oxygen reduction reaction (ORR) due to their predictable properties. However, the closely parallel-stacking manner and lacking intramolecular electron transfer ability of COFs limit atomic utilization efficiency and intrinsic activity. Herein, COFs are constructed with large interlayer distances and enhanced electronic transfer ability by side-chain functionalization. Long chains with electron-donating features not only enlarge interlayer distance, but also narrow the bandgap. The resulting DPPS-COF displays higher electrochemical surface areas to provide more exposed active sites, despite <1/10 surface areas. DPPS-COF exhibits excellent electrocatalytic ORR activity with half-wave potential of 0.85 V, which is 30 and 60 mV positive than those of Pt/C and DPP-COF, and is the record among the reported COFs. DPPS-COF is employed as cathode electrocatalyst for zinc-air battery with a maximum power density of 185.2 mW cm -2 , which is superior to Pt/C. Theoretical calculation further reveals that longer electronic-donating chains not only facilitate the formation of intermediate OOH* from O 2 , but also promote intermediates desorption , and thus leading to higher activity., (© 2024 Wiley‐VCH GmbH.)

Resveratrol (3,5,4'-trihydroxystilbene, RSV) is a natural stilbene synthetized as trans-isomer in plants exposed to oxidative stress. In order to understand the mechanism involved during photosensitized degradation of trans-resveratrol, steady-state and time-resolved experiments were performed and compared with quantum-chemical calculations using density functional theory (DFT). Pterin (Ptr), a well-known photosensitizer, under UV-A radiation induces the oxidation of several biomolecules mainly through electron-transfer mechanisms. On the one hand, it was observed that trans-RSV participates in an energy-transfer pathway with Ptr triplet excited state ( 3 Ptr*) forming 3 trans-RSV*, which dissipates the energy by isomerization to cis-RSV. On the other hand, RSV neutral radical (trans-RSV(-H) • ) was detected in laser flash photolysis experiments, evidencing an electron-transfer mechanism. The electron-transfer from 3 Ptr* to trans-RSV is a barely feasible reaction, however, more favorable is the formation of trans-RSV(-H) • in a reaction between trans-RSV and Ptr radical cation (Ptr •+ ), which is produced during irradiation. The combination of experimental and theoretical approaches evidences the capability of trans-RSV to undergo energy-transfer (feasible by DFT calculations) and/or one-electron transfer pathways with 3 Ptr*. These findings reveal the mechanisms involved in the interaction of trans-RSV and pterin excited states and provide information on the antioxidant action of resveratrol during photosensitized oxidation of biomolecules., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The oxo-acid:ferredoxin oxidoreductase (OFOR) superfamily of enzymes are responsible for the reversible interconversion of CO 2 and oxo-acids, using CoA-derivatives as co-substrates, and requiring redox equivalents in the form of a soluble redox-carrier protein ferredoxin (Fd). Ultimately, these enzymes are responsible for the reduction of CO 2 to form pyruvate (in the case of PFOR) and oxo-glutarate (in the case of OGOR), by the reductive carboxylation reaction of acetyl-CoA and succinyl-CoA, respectively. The nature and kind of Fd that is the best redox-carrier to support the reductive reaction has been poorly studied to date. Most organisms that possess an OFOR contain multiple Fd redox-carriers (in addition to flavin-based flavodoxins). Here, we provide a guide for the comparison of various, similar, but non-identical Fd proteins that can interact with the PFOR from Chlorobaculum tepidum, as a model system. The conventional assay is presented, alongside an electrochemically detected assay, which demonstrates the inequivalence of Fd proteins in supporting either component of catalysis., (Copyright © 2024. Published by Elsevier Inc.)

Kinetic and structural investigations of the flavohemoglobin-type NO dioxygenase have suggested critical roles for transient Fe(III)O 2 complex formation and O 2 -forced movements affecting hydride transfer to the FAD cofactor and electron-transfer to the Fe(III)O 2 complex. Stark-effect theory together with structural models and dipole and internal electrostatic field determinations provided a semi-quantitative spectroscopic method for investigating the proposed Fe(III)O 2 complex and O 2 -forced movements. Deoxygenation of the enzyme causes Stark effects on the ferric heme Soret and charge-transfer bands revealing the Fe(III)O 2 complex. Deoxygenation also elicits Stark effects on the FAD that expose forces and motions that create a more restricted NADH access to FAD for hydride transfer and switch electron-transfer off. Glucose also forces the enzyme toward an off state. Amino acid substitutions at the B10, E7, E11, G8, D5, and F7 positions influence the Stark effects of O 2 on resting heme spin states and FAD consistent with the proposed roles of the side chains in the enzyme mechanism. Deoxygenation of ferric myoglobin and hemoglobin A also induces Stark effects on the hemes suggesting a common 'oxy-met' state. The ferric myoglobin and hemoglobin heme spectra are also glucose-responsive. A conserved glucose or glucose-6-phosphate binding site is found bridging the BC-corner and G-helix in flavohemoglobin and myoglobin suggesting novel allosteric effector roles for glucose or glucose-6-phosphate in the NO dioxygenase and O 2 storage functions. The results support the proposed roles of a ferric O 2 intermediate and protein motions in regulating electron-transfer during NO dioxygenase turnover., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest with the contents of this article., (Copyright © 2023 Elsevier Inc. All rights reserved.)

A one-step hydrothermal method for preparation of copper oxides with different valences using ascorbic acid as a reducing reagent was developed for environmental remediation. The results suggested that the notable degradation performance of CuO 0 may be attributable to the abundant active sites, such as Cu or Cu-O, and was not significantly related to the Cu valence state. In contrast to direct degradation of pollutants by traditional superoxide radicals (O 2 •- ), O 2 •- played an important role in the reduction of high-valence Cu ions (Cu(III)). In addition, a series of radical quenching, electron paramagnetic resonance (EPR), and electrochemical experiments validated the existence of direct electron transfer between methylene blue (MB) and PMS mediated by CuO 0 and surface-bound radicals. The results suggested that the CuO 0 /PMS system may be less susceptible to diverse ions and natural organic matter other than dihydrogen phosphate anions. The mechanism of MB degradation under alkaline conditions was different from that under acidic conditions in that it was not reliant on radicals or charge transfer but direct oxidation by PMS. This study provides new insights into the heterogeneous processes involved in PMS activation by the copper oxides. Furthermore, this paper devotes to providing theoretical basis on pollutant removal via PMS activated by copper oxides and developing low-cost and high-efficiency catalysts., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Biochar (BC) has been demonstrated the potential to activate persulfate (PS), but the limited catalytic efficiencies hindered their further application. Herein, an innovative magnetic MgFe 2 O 4 /BC (MMB) derived from pomelo peel was prepared for persulfate-based advanced oxidation process (PS-AOPs). Benefitting from the extraordinary properties, levofloxacin (LFX) was efficiently removed in the MMB/PS system. MMB700 exhibited the best catalytic activity, 87.87% of LFX was removed in the MMB700/PS system. In addition, it could maintain 67.90% of LFX degradation efficiency after 3 times of reuse. Quenching experiments, electron spin resonance (ESR) detection, and electrochemical test results indicated that both non-radical pathway and direct electron-transfer pathway advanced LFX degradation. LFX was oxidized by O 2 ·- and 1 O 2 , O 2 ·- acted as the dominant active species. PS activation was induced by the active sites of MMB700. This work not only developed a promising magnetic biochar PS catalyst for antibiotics elimination, but also facilitated insights PS activation mechanisms., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Nickel iron hydroxides (NiFeOH) have been drawing enormous attention as effective catalysts for oxygen evolution reaction (OER), a key process in water splitting. Herein, we report that negatively charged iron(III) hydroxide colloidal particles, can significantly enhance the OER activity of NiFeOH in alkaline media. NiFeOH is grown on nickel foam in a supersaturated iron(III) salt solution, which also contains a high content of Fe(OH) 3 colloidal nanoparticles, forming free-standing NiFeOH@C x electrodes (with x being the Fe(OH) 3 concentration). The interface between NiFeOH and Fe(OH) 3 colloidal particles, as manifested by the unique volcano-like holes on the NiFeOH@C x surface, is likely the OER active sites. In comparison to Fe(OH) 3 -free NiFeOH, NiFeOH@C 1000 exhibits a 40-fold enhancement of the OER activity, confirming the significant effect of Fe(OH) 3 colloidal nanoparticles in boosting the OER activity, likely as a result of enhanced charge transfer from Ni 2+ to Fe 3+ that facilitates the adsorption of key reaction intermediates. Furthermore, by coupling the free-standing NiFeOH@C 1000 electrode with commercial Pt/C, full water splitting can occur and reach a current density of 10 mA cm -2 under a cell voltage of 1.51 V, which is lower than that (1.59 V) based on noble metal catalysts of RuO 2  + Pt/C., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The design and construction of highly efficient and durable non-noble metal bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media is essential for developing the hydrogen economy. To achieve this goal, we have developed a bifunctional nanowire-structured FeP-CoP array catalyst on carbon cloth with uniform distribution through in-situ hydrothermal growth and phosphating treatment. The unique nanowire array structure and the strong electronic interaction between FeP and CoP species have been confirmed. Electrochemical studies have found that the designed Fe 0.14 Co 0.86 -P/CC catalyst appears excellent HER (130 mV@10 mA cm -2 )/OER (270 mV@10 mA cm -2 ) activity and stability. Moreover, the bifunctional Fe 0.14 Co 0.86 -P/CC (+/-) catalyst is also used in simulated industrial water splitting system, where the pair catalyst requires about 1.95 and 2.14 V to reach 500 and 1000 mA cm -2 , even superior to the control RuO 2 (+) ||Pt/C (-) catalyst, showing good industrial application prospects. These excellent electrocatalytic properties are attributed to the synergy between FeP and CoP species as well as the unique microstructure, which can accelerate charge transfer, expose more active sites and enhance electrolyte diffusion and gas emissions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Pterin (Ptr) is a model photosensitizer that acts mainly through type I mechanism and is able to photoinduce the one-electron oxidation of purine and pyrimidine nucleobases. However, under anaerobic conditions Ptr reacts with thymine (T) to form photoadducts (Ptr-T) but does not lead to the photodegradation of guanine (G), which is the nucleobase with the lowest ionization potential. Accordingly, G is thermodynamically able to reduce the radicals of the other nucleobases and has been described in this sense as the "hole sink" of the DNA double helix. Here we analyze by steady-state and time-resolved studies the effect of G in the anaerobic photosensitization of T by Ptr, using nucleotides and oligonucleotides of different sequences. We demonstrated that G is able to reduce T radicals but does not prevent the formation of Ptr-T adducts. Our results suggest that after the encounter between the excited Ptr and T, and completion of the electron transfer step, part of the radicals escape from the solvent cage, to further react with other species. However, a proportion of radicals do not escape and evolve to photoadducts before separation. We provide new evidence that contributes to understand the photosensitizing properties of Ptr in the absence of O 2 , the mechanism of formation of photoadducts in the DNA and the protective role of G towards the photodamage in other nucleobases., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Tyrosine is an amino acid related to crucial physiological events and its oxidation, that produce beneficial or detrimental effects on biological systems, has been extensively studied. Degradation of tyrosine often begins with the loss of an electron in an electron transfer reaction in the presence of a suitable electron acceptor. The reaction is facilitated by excited states of the acceptor in photosensitized processes. Several products of tyrosine oxidation have been described, the main ones being 3,4-dihydroxy-l-phenylalanine (commonly known as DOPA) and tyrosine dimers. Here, we report tyrosine recovery from tyrosyl radical, after one-electron oxidation, in the presence of DOPA. We propose that under high oxidative stress the oxidation of tyrosine may be controlled, in part, by one of its oxidation products. Also, we present strong evidence of antioxidant action of DOPA by preventing tyrosine dimerization, one of the most serious oxidative protein modifications, and the origin of structural modifications leading to the loss of protein functionality., (Copyright © 2021 Elsevier Inc. All rights reserved.)

2-oxoglutarate:ferredoxin oxidoreductase (OGOR) is a thiamine pyrophosphate (TPP) and [4Fe-4S] cluster-dependent enzyme from the reductive tricarboxylic acid (rTCA) cycle that fixes CO 2 to succinyl-CoA, forming 2-oxoglutarate and CoA. Here we report an OGOR from the rTCA cycle of Magnetococcus marinus MC-1, along with all three potential ferredoxin (Fd) redox partners. We demonstrate Mm OGOR operates bidirectionally (both CO 2 -fixing and 2-oxoglutarate oxidizing), and that only one Fd ( Mm Fd1) supports efficient catalysis. Our 1.94-Å and 2.80-Å resolution crystal structures of native and substrate-bound forms of Mm OGOR reveal the determinants of substrate specificity and CoA-binding in an OGOR, and illuminate the [4Fe-4S] cluster environment, portraying the electronic conduit allowing Mm Fd1 to be wired to the bound-TPP. Structural and biochemical data further identify Glu45α as a mobile residue that impacts catalytic bias toward CO 2 -fixation although it makes no direct contact with TPP-bound intermediates, indicating that reaction directionality can be tuned by second layer interactions. (149 of 150 words limit)., Competing Interests: Declaration of Interests The authors declare no conflict of interest.

A convenient heterogeneous continuous-flow procedure for the polarity reversal of aromatic α-diketones is presented. Propaedeutic batch experiments have been initially performed to select the optimal supported base capable to initiate the two electron-transfer process from the carbamoyl anion of the N , N -dimethylformamide (DMF) solvent to the α-diketone and generate the corresponding enediolate active species. After having identified the 2- tert -butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine on polystyrene (PS-BEMP) as the suitable base, packed-bed microreactors (pressure-resistant stainless-steel columns) have been fabricated and operated to accomplish the chemoselective synthesis of aroylated α-hydroxy ketones and 2-benzoyl-1,4-diones (benzoin- and Stetter-like products, respectively) with a good level of efficiency and with a long-term stability of the packing material (up to five days).

Two boron-dipyrrin (BODIPY) based dyes with dimethylaminophenyl and carboxyphenyl substituents in 8-position of dipyrrin ligand have been synthesized and characterized. Photophysical and spectral properties of the obtained compounds have been investigated in water-ethanol mixture and water-cyclohexane system with variation of pH values. The equilibria constants of the compounds were identified by classical methods of acid-base titration. BODIPY bearing dimethylaminophenyl and carboxyphenyl subunits show deprotonation/protonation dependent fluorescence off/on-switching. The change of the emission could be mechanistically explained by a PET (photoinduced electron transfer) from the 8-substituent to the fluorophore. The present study demonstrates that BODIPY-based fluorescent sensors can be used to measure the pH in the range of 2-13 extending the scope of BODIPY dyes available as pH-indicators. Investigated compounds demonstrate weak dye-dye interaction allowing their cooperative usage as indicators.

The dissimilatory adenosine 5'-phosphosulfate reductase (AprAB) is a key enzyme in the sulfate reduction pathway that catalyzes the reversible two electron reduction of adenosine 5'-phosphosulfate (APS) to sulfite and adenosine monophosphate (AMP). The physiological electron donor for AprAB is proposed to be the QmoABC membrane complex, coupling the quinone-pool to sulfate reduction. However, direct electron transfer between these two proteins has never been observed. In this work we demonstrate for the first time direct electron transfer between the Desulfovibrio desulfuricans ATCC 27774 QmoABC complex and AprAB. Cyclic voltammetry conducted with the modified Qmo electrode and AprAB in the electrolyte solution presented the Qmo electrochemical signature with two additional well-defined one electron redox processes, attributed to the AprAB FAD redox behavior. Moreover, experiments performed under catalytic conditions using the QmoABC modified electrode, with AprAB and APS in solution, show a catalytic current peak develop in the cathodic wave, attributed to substrate reduction, and which is not observed in the absence of QmoABC. Substrate dependence conducted with different electrode preparations (with and without immobilized Qmo) demonstrated that the QmoABC complex is essential for efficient electron delivery to AprAB, in order to sustain catalysis. These results confirm the role of Qmo in electron transfer to AprAB., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A general synthetic sequence involving simply prepared starting materials provides rapid access to diverse, novel tricyclic architectures inspired by pleuromutilin. Sm(II) -mediated radical cyclization cascades of dialdehydes, prepared using a new, one-pot, copper-catalyzed double organomagnesium addition to β-chlorocyclohexenone, proceed with complete sequence selectivity and typically with high diastereocontrol to give analogues of the target core. Our expedient approach (ca. 7 steps) allows non-traditional, de novo synthetic access to analogues of the important antibacterial that can't be prepared from the natural product by semisynthesis., (© 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)

A methemoglobin (metHb) reduction system is required for aerobic respiration. In humans, Fe(III)-heme-bearing metHb (the oxidized form of hemoglobin), which cannot bind oxygen, is converted to Fe(II)-heme-bearing oxyhemoglobin (oxyHb, the reduced form), which can bind oxygen, in a system comprising NADH, NADH-cytochrome b5 reductase, and cytochrome b5. However, the mechanism of metHb reduction in organisms that inhabit oxygen-deficient environments is unknown. In the coelomic fluid of the larvae of Propsilocerus akamusi, which inhabit a microaerobic environment, we found that metHb was reduced by D-alanine. We purified an FAD-containing enzyme, D-amino acid dehydrogenase (DAD), and component V hemoglobin from the larvae. Using the purified components and spectrophotometric analyses, we showed a novel function of DAD: DAD-mediation of P. akamusi component V metHb reduction with using D-alanine as an electron donor. P. akamusi larvae possess this D-alanine-DAD metHb reduction system in addition to a previously discovered NADH-NADH-cytochrome b5 reductase system. This is the first report of the presence of DAD in a multicellular organism. The molecular mass of DAD was estimated to be 45 kDa. The optimal pH and temperature of the enzyme were 7.4 and 20 °C, respectively, and the optimal substrate was D-alanine. The enzyme activity was inhibited by benzoate and sulfhydryl-binding reagents., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Aqueous solutions of the four highest vanadium oxidation states exhibit four diverse colors, which only hint at the diverse reactions that these ions can undergo. Cationic vanadium ions form complexes with ligands; anionic vanadium ions form complexes with ligands and self-react to form isopolyanions. All vanadium species undergo oxidation-reduction reactions. With a few exceptions, elucidation of the dynamics of these reactions awaited the development of fast reaction techniques before the kinetics of elementary ligation, condensation, reduction, and oxidation of the aqueous vanadium ions could be investigated. As the biological roles played by endogenous and therapeutic vanadium expand, it is appropriate to bring the results of the diverse kinetics studies under one umbrella. To achieve this goal this review presents a systematic examination of elementary aqueous vanadium ion dynamics., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Photoactive reaction centers (RCs) are protein complexes in bacteria able to convert sunlight into other forms of energy with a high quantum yield. The photostimulation of immobilized RCs on inorganic electrodes result in the generation of photocurrent that is of interest for biosolar cell applications. This paper reports on the use of novel electrodes based on functional conductive nanocrystalline diamond onto which bacterial RCs are immobilized. A three-dimensional conductive polymer scaffold grafted to the diamond electrodes enables efficient entrapment of photoreactive proteins. The electron transfer in these functional diamond electrodes is optimized through the use of a ferrocene-based electron mediator, which provides significant advantages such as a rapid electron transfer as well as high generated photocurrent. A detailed discussion of the generated photocurrent as a function of time, bias voltage, and mediators in solution unveils the mechanisms limiting the electron transfer in these functional electrodes. This work featuring diamond-based electrodes in biophotovoltaics offers general guidelines that can serve to improve the performance of similar devices based on different materials and geometries.

Tyrosinase is an important marker of human diseases such as the neurodegeneration associated with Parkinson's disease and melanoma. Sensitive detection of tyrosinase activity in vitro and inside cells is of great significance to medical diagnostics and skin disorder treatments. With unique photophysical properties, semiconductor quantum dots (QDs) are employed as photoluminescent platforms for various biosensing, in particular for the detection of enzyme activities. In this work, QDs are functionalized with tyrosine and zwitterionic molecules to construct a nanometer-scale scaffold (QD-Tyr conjugate), and this is used to test tyrosinase activity in vitro and inside cells. Tyrosinase oxidizes tyrosine to dopachrome and switches on the electron-transfer access, which relates to fluorescence quenching. High quenching efficiency is achieved by shortening the distance between the electron donors and acceptors, which is attributed to the small size of the conjugated tyrosine. Enzymatic process curves reveal the enhanced enzymatic activity on the conjugated nanoparticle substrate, which leads to highly sensitive detection of tyrosinase (as low as 1 nM). It is also demonstrated that QD-Tyr conjugates can sensitively probe intracellular tyrosinase in melanoma cells, which promises great potential in disease monitoring and medical diagnostics., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the first study of the electrochemical reactivity of a graphenated carbon nanotube (g-CNT) film. The electron transfer kinetics of the ferri-ferrocyanide couple were examined for a g-CNT film and compared to the kinetics to standard carbon nanotubes (CNTs). The g-CNT film exhibited much higher catalytic activity, with a heterogeneous electron-transfer rate constant, k 0 , approximately two orders of magnitude higher than for standard CNTs. Scanning electron microscopy and Raman spectroscopy were used to correlate the higher electron transfer kinetics with the higher edge-density of the g-CNT film.

Graphene research and in particular the topic of chemical functionalization of graphene has exploded in the last decade. The main aim is to increase the solubility and thereby enhance the processability of the material, which is otherwise insoluble and inapplicable for technological applications when stacked in the form of graphite. To this end, initially, graphite was oxidized under harsh conditions to yield exfoliated graphene oxide sheets that are soluble in aqueous media and amenable to chemical modifications due to the presence of carboxylic acid groups at the edges of the lattice. However, it was obvious that the high-defect framework of graphene oxide cannot be readily utilized in applications that are governed by charge-transfer processes, for example, in solar cells. Alternatively, exfoliated graphene has been applied toward the realization of some donor-acceptor hybrid materials with photo- and/or electro-active components. The main body of research regarding obtaining donor-acceptor hybrid materials based on graphene to facilitate charge-transfer phenomena, which is reviewed here, concerns the incorporation of porphyrins and phthalocyanines onto graphene sheets. Through illustrative schemes, the preparation and most importantly the photophysical properties of such graphene-based ensembles will be described. Important parameters, such as the generation of the charge-separated state upon photoexcitation of the organic electron donor, the lifetimes of the charge-separation and charge-recombination as well as the incident-photon-to-current efficiency value for some donor-acceptor graphene-based hybrids, will be discussed.

The direct conversion of sunlight into biofuels is an intriguing alternative to a continued reliance on fossil fuels. Natural photosynthesis has long been investigated both as a potential solution, and as a model for utilizing solar energy to drive a water-to-fuel cycle. The molecules and organizational structure provide a template to inspire the design of efficient molecular systems for photocatalysis. A clear design strategy is the coordination of molecular interactions that match kinetic rates and energetic levels to control the direction and flow of energy from light harvesting to catalysis. Energy transduction and electron-transfer reactions occur through interfaces formed between complexes of donor-acceptor molecules. Although the structures of several of the key biological complexes have been solved, detailed descriptions of many electron-transfer complexes are lacking, which presents a challenge to designing and engineering biomolecular systems for solar conversion. Alternatively, it is possible to couple the catalytic power of biological enzymes to light harvesting by semiconductor nanomaterials. In these molecules, surface chemistry and structure can be designed using ligands. The passivation effect of the ligand can also dramatically affect the photophysical properties of the semiconductor, and energetics of external charge-transfer. The length, degree of bond saturation (aromaticity), and solvent exposed functional groups of ligands can be manipulated to further tune the interface to control molecular assembly, and complex stability in photocatalytic hybrids. The results of this research show how ligand selection is critical to designing molecular interfaces that promote efficient self-assembly, charge-transfer and photocatalysis. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems., (Copyright © 2013 Elsevier B.V. All rights reserved.)