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This article explores the use of semiconductor photocatalysts (SPs) for organic synthesis, specifically focusing on the transformation of alcohols. The authors conducted experiments using different photocatalysts and found that a combination of Au/TiO2 and Cu/TiO2 was the most efficient for N-alkylation reactions. They also demonstrated the successful synthesis of various pharmaceutical compounds using this method. The authors highlight the mild reaction conditions and high atom-economy of their methods, making them useful for the synthesis of complex organic molecules. They believe that this research has the potential to contribute to the development of new organic transformations and provide insights into the stability and reactivity of carbon-centered radicals on the photocatalytic surface. [Extracted from the article]

The redox-neutral addition of α-C–H bonds of acetonitrile and acetone to styrenes was enabled via the hydrogen-atom transfer from relatively acidic and water-miscible C(sp3)–H bonds to an aqueous hydroxyl radical generated cleanly and iteratively by the oxidation of water under silver-nanoparticle-loaded titania photocatalysis without using stoichiometric oxidation agents. [ABSTRACT FROM AUTHOR]

Nonribosomal peptides (NRPs) are natural products that are biosynthesized by large multi-enzyme assembly lines called nonribosomal peptide synthetases (NRPSs). We have previously discovered that backbone or side chain methylation of NRP residues is carried out by an interrupted adenylation (A) domain that contains an internal methyltransferase (M) domain, while maintaining a monolithic AMA fold of the bifunctional enzyme. A key question that has remained unanswered is at which step of the assembly line mechanism the methylation by these embedded M domains takes place. Does the M domain methylate an amino acid residue tethered to a thiolation (T) domain on same NRPS module (in cis), or does it methylate this residue on a nascent peptide tethered to a T domain on another module (in trans)? In this study, we investigated the kinetics of methylation by wild-type AMAT tridomains from two NRPSs involved in biosynthesis of anticancer depsipeptides thiocoraline and echinomycin, and by mutants of these domains, for which methylation can occur only in trans. The analysis of the methylation kinetics unequivocally demonstrated that the wild-type AMATs methylate overwhelmingly in cis , strongly suggesting that this is also the case in the context of the entire NRPS assembly line process. The mechanistic insight gained in this study will facilitate rational genetic engineering of NRPS to generate unnaturally methylated NRPs. Unlabelled Image • Methylation mechanism in nonribosomal peptide synthetases remains to be determined. • Kinetic studies unequivocally established methylation occurs within one module. • This mechanistic logic will aid in engineering unnaturally methylated peptides. [ABSTRACT FROM AUTHOR]

A novel Zn phthalocyanine-Zn porphyrin (ZnPc-ZnPor) dyad ( 1), in which a zinc porphyrin moiety is linked covalently with an ABAB-type zinc phthalocyanine moiety, has been designed and synthesized. The ZnPc-ZnPor dyad 1 can absorb over a wide spectral range of visible light. The fluorescence spectrum of dyad 1 revealed an intramolecular efficient energy transfer from Zn porphyrin to Zn phthalocyanine. When dyad 1 was used as a light-harvesting sensitizer for dye-sensitized solar cells, the cell sensitized by dyad 1 provided a power conversion efficiency of 2.7 % under simulated air mass 1.5 global sunlight. The incident photon-to-current efficiency spectrum of the dyad 1 cell suggested the contribution of both components in dyad 1 for the current generation. [ABSTRACT FROM AUTHOR]

The azinomycins are a family of potent antitumor agents with the ability to form interstrand cross-links with DNA. This study reports on the unusual biosynthetic formation of the 5-methyl naphthoate moiety, which is essential for effective DNA association. While sequence analysis predicts that the polyketide synthase (AziB) catalyzes the formation of this naphthoate, 2-methylbenzoic acid, a truncated single-ring product, is formed instead. We demonstrate that the thioesterase (AziG) acts as a chain elongation and cyclization (CEC) domain and is required for the additional two rounds of chain extension to form the expected product. [ABSTRACT FROM AUTHOR]

Abstract: We prepared nanoporous NiO films from NiCl2 in water/ethanol mixed solution, using a series of polyethyleneoxide–polypropyleneoxide–polyethyleneoxide (PEO–PPO–PEO) triblock co-polymers as template, and examined them as p-type NiO electrodes sensitized with a merocyanine dye. Triblock co-polymers with high PEO/PPO ratio leaded to three-fold higher photocurrent in comparison with low PEO/PPO polymers. Use of high PEO/PPO templates resulted in NiO membrane structure formed by uniformly distributed NiO nano particles with small interparticle voids, giving large surface area for dye adsorption, while low PEO/PPO templates resulted in larger void volume and less surface area. Photocurrent under simulated solar light was sum of the currents generated by NiO direct excitation and by dye-sensitization at spectra below 450nm and from 450 to 590nm, respectively. [Copyright &y& Elsevier]

Abstract: We prepared nanoporous p-type CuO semiconductor electrodes adsorbing various dyes with different HOMO levels and anchoring groups. Solar cells were fabricated by coupling each of the dyed electrodes with a platinum counter electrode and filled with electrolytes containing I−/I3 − redox couple. Cathodic photocurrent due to hole injection from the adsorbed dye to the semiconductor was observed. Only the dyes with HOMO and LUMO potentials more positive than valence and conduction band edges, respectively, functioned as sensitizers for p-type dye-sensitized solar cells. Effects of annealing temperature and thickness of the CuO nanoporous membrane on cell performance were investigated as well. [Copyright &y& Elsevier]

The Japanese rhinoceros beetle Trypoxylus dichotomus is a giant beetle with distinctive exaggerated horns present on the head and prothoracic regions of the male. T. dichotomus has been used as a research model in various fields such as evolutionary developmental biology, ecology, ethology, biomimetics, and drug discovery. In this study, de novo assembly of 615 Mb, representing 80% of the genome estimated by flow cytometry, was obtained using the 10 × Chromium platform. The scaffold N50 length of the genome assembly was 8.02 Mb, with repetitive elements predicted to comprise 49.5% of the assembly. In total, 23,987 protein-coding genes were predicted in the genome. In addition, de novo assembly of the mitochondrial genome yielded a contig of 20,217 bp. We also analyzed the transcriptome by generating 16 RNA-seq libraries from a variety of tissues of both sexes and developmental stages, which allowed us to identify 13 co-expressed gene modules. We focused on the genes related to horn formation and obtained new insights into the evolution of the gene repertoire and sexual dimorphism as exemplified by the sex-specific splicing pattern of the doublesex gene. This genomic information will be an excellent resource for further functional and evolutionary analyses, including the evolutionary origin and genetic regulation of beetle horns and the molecular mechanisms underlying sexual dimorphism. [ABSTRACT FROM AUTHOR]

Abstract: Dye-sensitized solar cells (DSCs) were fabricated from mesoporous SnO2 electrodes, which were prepared from nano-sized SnO2 particles. Current–voltage characteristics of the DSCs were compared with DSCs prepared from conventional TiO2 electrodes, which have similar amount of adsorbed dye with the SnO2. As a result, short-circuit current of the SnO2DSC were comparable with that of the TiO2DSCs, and more than 15mA/cm2 was obtained with the SnO2 at the thickness of 10μm under one sun conditions. Electron diffusion coefficients and lifetimes in the SnO2 and TiO2 electrodes were measured, showing slower diffusion and longer lifetime in the SnO2DSC than in the TiO2. The results imply that the electron transport and transfer dynamics in such electrodes is dominated by the influence of intra-band charge traps, and the control of the trap conditions would be the key strategy to employ various metal oxides for such solar cells. [Copyright &y& Elsevier]

Abstract: The lifetime of electrons in the semiconductor electrode of dye-sensitized solar cells (DSSCs) is an important parameter determining the energy conversion efficiency. We propose a method to determine the electron lifetime by stepped current induced measurement of cell voltage in the dark (darkSCIM). Since this technique does not require the creation of photoinduced charges, the lifetime of devices with poorly injecting dyes, or indeed values for devices, which employ no sensitizer, can be determined. [Copyright &y& Elsevier]

In order to explain the higher short-circuit current (Jsc) with comparable open-circuit voltage (Voc) from dye-sensitized solar cells (DSCs) based on gallium-modified ZnO (ZnO:Ga) porous electrodes, the diffusion coefficient (D) and electron lifetime (τ) in DSCs with and without Ga-modified ZnO were studied by stepped light-induced transient measurements of photocurrent and voltage. In comparison to DSCs based on ZnO electrodes, the ZnO:Ga-based solar cells provided lower D and higher τ values. The results were interpreted according to the transport-limited recombination model, where the Ga modification induced a higher density of intraband charge traps. At matched electron densities, a decrease in Voc from DSCs based on ZnO:Ga was observed, suggesting a positive shift of the ZnO:Ga conduction band edge. The higher Jsc can be explained by the positive shift of the ZnO:Ga conduction band edge in addition to the increased roughness factor of the electrode due to the Ga modification. [ABSTRACT FROM AUTHOR]

Porous TiO2 electrodes were prepared by oxidizing two-dimensional titanium carbide nanosheets (Ti3C2 MXene) and the electrodes were tested in dye-sensitized solar cells. The effects of oxidation temperature and duration time together with various thicknesses on the device performance were investigated. A power conversion efficiency of 2.66% was observed. [ABSTRACT FROM AUTHOR]

Julolidine and benzothiadiazole have been employed separately as building blocks for sensitizers to widen absorption spectrum for dye-sensitized solar cells (DSSCs). We synthesize a new dye combining the two blocks. The DSSCs using the dye show incident photon-to-electron conversion efficiency (IPCE) spectrum up to 850 nm and the maximum IPCE value of about 80%. Then we examine various co-adsorbents and find that co-adsorbing with a bulky dye enhances the IPCE of the new dye even at the wavelengths that the bulky dye does not absorb. On the other hand, such effect is not observed with co-adsorption of chenodeoxycholic acid and a flat structured dye. The results suggest that even if small dyes do not have alkyl chains, the dyes can benefit from the blocking function of the alkyl chains attached to the co-adsorbed bulky dyes. [ABSTRACT FROM AUTHOR]

A variety of charge extraction (CE) techniques have been developed to measure charge density and recombination coefficients in bulk heterojunction solar cells. Charge recombination during charge extraction as a major limitation of this method has not been systematically quantified. This study reports CE measurements using a newly designed fast switch, which enables the application of a reverse bias to the solar cells facilitating charge extraction. With applied reverse bias, more than 40% increase in the extracted charge is obtained in solar cells with thicker active layers or with fast recombination. The measured charge carrier lifetime increases by up to a factor of three at sufficiently high applied biases (up to 8 V), suggesting significant errors in CE measurements without applied bias. The increased extracted charges with increasing applied bias are attributed to a combination of three cases: (i) slightly faster charge extraction due to the larger electric field; (ii) increased charge extraction rate at high light intensities when the transients are space charge disturbed; (iii) increased charge separated lifetime during charge extraction attributed to the spatial separation of the electron and hole density due to the applied electric field. [ABSTRACT FROM AUTHOR]

• Sustainable organic reactions with water coordinated on TiO 2 and renewable energies. • Hydroxyl radical in water, as immortal agent, for scalable C H bond functionalization. • Charge trapping ability dramatically altered with coordination environment of water. • Highly selective electrochemical hydrogenations of organic acid derivatives. There is an increasing demand to replace conventional industrial systems that emit massive amounts of CO 2 with lower-carbon emitting systems, and this has spurred research on the application of renewable energy for chemical conversions. Hydrogen and other simple chemical products have been efficiently manufactured using renewable light energy or secondary energy sources, such as electricity. More importantly, the direct use of water as a ubiquitous and clean hydrogen (or electron) and oxygen source in organic synthesis has recently been realized. Semiconductor photo- and electrocatalysts, such as metal oxides, play significant roles in energy transformations and in the activation of reactant chemicals. This paper reviews recent developments in organic synthesis using water and renewable light or electric energy to achieve sustainable chemical production. TiO 2 is especially featured as a reaction platform where both reactants and water are efficiently activated through coordination with the TiO 2 surface. We also discuss the role of water in the reaction on the TiO 2 surface from the perspectives of synthetic chemistry, physical surface chemistry, and nanomaterial chemistry. [ABSTRACT FROM AUTHOR]

The article offers information about a study that explores the use of alkyl-functionalized organic dyes for efficient molecular photovoltaics. This study is in line with the considerably increasing interest in organic devices such as light-emitting diodes, field effect transistors, and photovoltaic cells whose performance depend mainly on the properties of the functionalized organic molecules.

A series of zinc phthalocyanine sensitizers ( PcS22- 24) having a pyridine anchoring group are designed and synthesized to investigate the structural dependence on performance in dye-sensitized solar cells. The pyridine-anchor zinc phthalocyanine sensitizer PcS23 shows 79 % incident-photon to current-conversion efficiency (IPCE) and 6.1 % energy conversion efficiency, which are comparable with similar phthalocyanine dyes having a carboxylic acid anchoring group. Based on DFT calculations, the high IPCE is attributed with the mixture of an excited-state molecular orbital of the sensitizer and the orbitals of TiO2. Between pyridine and carboxylic acid anchor dyes, opposite trends are observed in the linker-length dependence of the IPCE. The red-absorbing PcS23 is applied for co-sensitization with a carboxyl-anchor organic dye D131 that has a complementary spectral response. The site-selective adsorption of PcS23 and D131 on the TiO2 surface results in a panchromatic photocurrent response for the whole visible-light region of sun light. [ABSTRACT FROM AUTHOR]

The effect of thedonor in an organic dye on the electron lifetimeof dye-sensitized solar cells (DSSCs) employing a cobalt redox electrolytewas investigated. We synthesized organic dyes with donor moietiesof carbazole, coumarin, triphenylamine, and N-phenyl-carbazoleand measured the current–voltage characteristics and electronlifetimes of the DSSCs with these dyes. The cell with the triphenylaminedonor dye produced the highest open circuit voltage and longest electronlifetime. On the other hand, the lowest open circuit voltage and shortestelectron lifetime was obtained with coumarin donor dye, suggestingthat the coumarin attracted the cobalt redox couples to the surfaceof the TiO2layer, thus increasing the concentration ofcobalt complex. On the other hand, the longest electron lifetime withtriphenylamine was attributed to the blocking effect by steric hindranceof the nonplanar structure of the donor. [ABSTRACT FROM AUTHOR]

A series of zinc-phthalocyanine sensitizers ( PcS16- 18) with different adsorption sites have been designed and synthesized in order to investigate the dependence of adsorption-site structures on the solar-cell performances in zinc-phthalocyanine based dye-sensitized solar cells. The change of adsorption site affected the electron injection efficiency from the photoexcited dye into the nanocrystalline TiO2 semiconductor, as monitored by picosecond time-resolved fluorescence spectroscopy. The zinc-phthalocyanine sensitizer PcS18, possessing one carboxylic acid directly attached to the ZnPc ring and six 2,6-diisopropylphenoxy units, showed a record power conversion efficiency value of 5.9 % when used as a light-harvesting dye on a TiO2 electrode under one simulated solar condition. [ABSTRACT FROM AUTHOR]

A series of panchromatic ruthenium sensitizers ( MJ sensitizers) with attached thiophene and phenyl units bearing alkyl chains was synthesized. A new synthetic route was used to examine all possible positions for the alkyl chains. The absorption spectra showed the sum of a ruthenium complex and peripheral organic chromophore units. The hypochromic effect and blueshift of the metal-to-ligand charge-transfer band observed in the modified ruthenium sensitizers were suppressed by changing the positions of the alkyl chains on the attached thiophene ring. Changing only one alkyl chain also influenced the performance of dye-sensitized solar cells. Ruthenium sensitizer MJ-10 with bulky substituent harvests visible and near-infrared light, and solar cells sensitized by MJ-10 exhibit an efficiency of 9.1 % under 1 sun irradiation. [ABSTRACT FROM AUTHOR]

When an alkyl-functionalized metal-free organic dye (MK-2) was employed as a sensitizer, dye-sensitized TiO2solar cells (DSSCs) fabricated with an ionic liquid (IL) electrolyte showed an energy conversion efficiency of 7.6%, which was comparable to that with a volatile liquid electrolyte. This contrasts with the case of DSSCs employing conventional Ru complex sensitizer (N719), whose efficiency was decreased markedly when the electrolyte was replaced from the volatile to IL. As a result, with the IL electrolyte, the conversion efficiency with MK-2 was higher than that with N719. The result was mainly attributed to longer electron lifetime in the DSSCs with MK-2. The longer electron lifetime is remarkable because with conventional volatile electrolyte, the lifetimes with many organic dyes including MK-2 were shorter than that with N719. This high compatibility of MK-2 with the IL electrolyte shows that the molecular modification of organic dyes can overcome the both disadvantages of ILs and organic dyes, mostly originated from their high viscosity and from the short electron lifetime observed with volatile electrolyte, respectively. Long-term stability of the DSSCs with MK-2 and the ionic electrolyte was also investigated, showing the efficiency of more than 7% for 2000 h under 1 sun conditions. [ABSTRACT FROM AUTHOR]

Electron diffusion coefficient, lifetime, and density in the TiO2 electrode of dye-sensitized TiO2 solar cells (DSCs) employing I-/I3- redox couples were measured with eight different metal-free organic dyes and three Ru complex dyes. At matched electron density, all DSCs using organic dyes (ODSCs) showed shorter electron lifetime with comparable or larger diffusion coefficients in comparison to the DSCs using the Ru dyes (RuDSC). The shorter lifetime was attributed partially to the slower dye cation reduction rate of the organic dyes by I-, faster electron diffusion coefficient in the TiO2, and mostly higher I3- concentration in the vicinity of the TiO2 surface. Whereas a slight shift of the conduction band edge potential (Ecb) of the TiO2 was seen with a few organic dyes, no correlation was found with the dipole moment of the adsorbed dyes. This implies that the adsorbed dyes interact with cations in the electrolyte, so the direction of the dipole is altered or simply screened. The increase of [I3-] in the vicinity of the TiO2 surface was interpreted with partial charge distribution of the dyes. Under one-sun conditions, less electron density due to shorter electron lifetime was found to be the main reason for the lower values of Voc for all ODSCs in comparison to that of RuDSCs. Among the organic dyes, having larger molecular size and alkyl chains showed longer electron lifetime, and thus higher Voc. Toward higher open circuit voltage, a design guide of organic dyes controlling the electron lifetime is discussed. [ABSTRACT FROM AUTHOR]

This paper investigates the structure of adaptive noise cancellers with center-frequency adjustable IIR bandpass filter and notch-frequency adjustable IIR band-reject filter. First, the mean-square errors of variable coefficients of scalar structure are analyzed under the assumption of large input SNR. Next, the parallel block structures of the adaptive noise cancellers are introduced. The proposed structure can be implemented with multiinput, single-output digital filters operating in parallel. Design formulas of the present structures also are given. Finally, the performances of an adaptive noise canceller realized by the parallel block structures are tested by computer simulation. It is shown that the new filter structure enables high-speed signal processing. [ABSTRACT FROM AUTHOR]

The synthesis of three-dimensional compounds containing perylene bis(dicarboximide) for application as acceptor materials in organic photovoltaics is reported. Physicochemical measurements as well as device evaluations revealed that the characteristic properties of these materials are derived from their three-dimensional structure. [ABSTRACT FROM AUTHOR]

While perylene dyes have suitable properties for dye-sensitized solar cells (DSSCs), the performance has been limited by various factors that are not fully understood yet. We prepared DSSCs based on mesoporous TiO 2 and ZnO with three blue piperidinyl-substituted perylene derivatives and three different electrolyte solutions. The perylene dyes have different non-conjugated side units and HOMO levels, and the anchoring group is a mono-anhydride moiety that would provide better compatibility with ZnO. Using current - voltage characteristics, incident and absorbed photon-to-electron conversion efficiency measurements (IPCE/APCE), stepped light induced transient measurements, and transient absorption spectroscopy (TAS), the limiting processes governing the solar cell performance are analyzed. With TiO 2 , weak electronic coupling between the dye and TiO 2 appears to limit the injection efficiency, while for ZnO, the coupling seems stronger resulting in higher injection yield and higher APCE. The HOMO levels and structural differences of the dyes have only a minor impact on the reduction kinetics of oxidized dyes. DFT calculations illustrate that the HOMO and LUMO of the dye are spatially not well separated. This probably leads to a short-excited state lifetime, resulting in the relatively low APCE values. The TA measurements of the cells with and without redox couple show similar decays, suggesting the oxidized dyes in the solar cells are reduced not only by redox couple but also by electrons from TiO 2 and ZnO, further decreasing the conversion efficiency. These results suggest the design rules to be followed for the successful implementation of all-organic perylene-based dyes for DSSCs. [ABSTRACT FROM AUTHOR]

Abstract: Dye-sensitized solar cells (DSSCs) are prepared using a combination of various carbazole dye derivatives or a ruthenium (Ru) complex dye (N719) and cobalt (Co) complex or I−/I3 − redox couples. With the Co redox couple, the largest molecular dye (MK14) demonstrated a longer lifetime and higher V oc than that of N719 and a comparable lifetime and V oc to those of N719 and the I−/I3 − redox couple. These results are due to the enhanced blocking effect that is obtained with the large dye and redox couple combination, providing a longer distance between the TiO2 surface and Co complex oxidized species. Thus, employing bulky redox couples for organic dyes that possess higher dispersion forces is effective in increasing the electron lifetime. [Copyright &y& Elsevier]

A remarkable 300% efficiency enhancement driven by a matching increase in the short circuit current was observed in a mixed porphyrin dye-sensitized solar cell constructed from two dyes in a 3:1 ratio. Absorbed photon-to-current conversion efficiency measurements indicate an improved charge injection yield for both dyes in the mixture. Several possible origins for the observed performance enhancement are discussed. [ABSTRACT FROM AUTHOR]

The article provides information on a research that demonstrates porphyrin in an array's contribution to current generation in a solar cell. It states that nanostructured semiconductor electrodes with order of a 1000 surface roughness factor were used in the study. It also investigates the use of a variety of porphyrin assays in the dye-sensitized solar cell (DSSC). Results show that dimer-sensitized DSSC's performance depends on dye uptake conditions.

We designed and synthesized two zinc phthalocyanine sensitizers (PcS27 and PcS28), substituted with branched or cyclic alkoxy chains, to investigate the structural effect of peripheral alkyl chains on the performance of dye-sensitized TiO2 solar cells. The bulky cyclic alkyl chains of PcS28 decreased the adsorption density of PcS28 on the TiO2 electrode, while the terminal branches of alkoxy chains of PcS27 did not influence the adsorption density in comparison to the previously published PcS20 with linear alkoxy chains. Under one sun conditions, PcS27 cells exhibited higher open-circuit voltage but a slightly lower energy conversion efficiency, 6.0% less than PcS20. These results suggest that the small alternation of alkoxy chains resulted in decreasing electron pushing ability of peripheral phenoxy units, giving lower short-circuit current. [ABSTRACT FROM AUTHOR]