Enhancing DSSCs and Photocatalytic Hydrogen Production with D-A1-A2-π-A Sensitizers Containing 10'H-Spiro[fluorene-9,9'-phenanthren]-10'-one and Benzo[c][1,2,5]thiadiazole.

Novel D-A1-A2-π-A organic sensitizers (FZ-sensitizer), utilizing spiro[fluorene-9,9'-phenanthren]-10'-one (A1) and benzo[c][1,2,5]thiadiazole(A2) moiety as two auxiliary acceptors, are synthesized and applied in dye-sensitized solar cells (DSSCs) and hydrogen production. By incorporating a bulky A1 and A2 between the donor (D) and π-bridge moiety, structural modifications inhibit molecular aggregation, while the carbonyl group enhances the capture of Li+ ions, thereby delaying charge recombination. Furthermore, the extended π-conjugation broadens the light absorption range and enhances the power conversion efficiency (PCE) of FZ-2 under AM1.5 conditions, achieving up to 5.72%. Co-sensitization with N719 and FZ-2 shows PCE of 9.60% under one sun. Under TL84 indoor light conditions, the efficiency is 29.69% at 2500 lux. FZ-sensitizers also exhibit high efficiency in photocatalytic hydrogen production. The hydrogen production activities of FZ-2 are 9190 µmol/g (1 hour) and 76582 µmol/g (12 hours) respectively, while those of FZ-1 are 7430 µmol/g (1 hour) and 64004 µmol/g (12 hours), indicating that FZ-2 can inject charges into TiO2 more efficiently and utilize them for water splitting. Stability testing of photocatalytic water splitting after 12 hours shows a turnover number (TON) of 4249 for FZ-1 and 5378 for FZ-2.

Hybridizing Tetraglyme to Aqueous Electrolyte with Concentrated Salts Promote Intercalation of Anions on Graphite Cathode in Dual-Ion Battery.

The amount of support salt in electrolytes determines the capacity of a dual-ion battery (DIB), and highly concentrated electrolytes are required for developing the high energy density DIB. In this study, hybrid aqueous tetraglyme (G4) electrolyte is investigated to develop high energy density aqueous DIB that is composed of carbon and Mo6 S8 for cathode and anode, respectively. Impedance measurement reveals that introduced G4 increases the activation energy of the anode; however, decreases the activation energy for anion intercalation into the carbon cathode. This decreases the activation energy resulted from the G4 molecule strongly solvated to Li+ resulting in weakening anion trapped in "contact ion pair" in concentrated aqueous electrolyte. So, hybrid G4-aqueous electrolyte is useful for better electrochemical intercalation of anion. In addition, this hybrid electrolyte is highly stable by formation of stable solid electrode-electrolyte interphase on Mo6 S8 anode and discharge capacity of 37 mAh g-1 , and 72% retained capacity after 500 cycles with a high average coulombic efficiency of 93% is achieved.

Solvated Structure of Hybrid Tetraglyme-Aqueous Electrolyte Dissolving High-Concentration LiTFSI-LiFSI for Dual-Ion Battery.

The solvated structure of a highly concentrated hybrid tetraglyme (G4)-water electrolyte was studied for an increasing cycle stability and performance of a KS6 used dual-ion battery. Hybrid solvent of G4 and water with a weight ratio of 2 to 8 was able to dissolve 9LiFSI-1LiTFSI supporting salts up to 37 mol kg-1 (37 mol kg-1 G2W8). In spite of such high concentration of supporting salts, reasonable charge and discharge performance of dual-ion battery (discharge capacity of ≈40 mAh g-1 and coulombic efficiency of 90 %) were exhibited over 300 cycles. This was attributed to the decreased hydrogen evolution reaction (HER) potential to -1.05 V vs. Ag/AgCl by addition of G4. From Fourier-transform infrared, nuclear magnetic resonance, and Raman spectroscopies, G4 molecules were more strongly coordinated to Li+ to form ion pairs of [Li(G4)x (H2 O)y ]+ complex in hybrid G4-water electrolyte. Co-intercalation of bis(trifluoromethanesulfonyl)imide (TFSI- ) and bis(fluorosulfonyl)imide (FSI- ) into graphitic carbon KS6 cathode was confirmed in hybrid aqueous electrolyte.

[2.2]- and [3.3]Paracyclophane as Bridging Units in Organic Dyads for Visible-Light-Driven Dye-Sensitized Hydrogen Production.

Novel donor-acceptor dyads containing [2.2]- and [3.3]paracyclophane (PCP) as the bridging moiety were synthesized and used to effectively fabricate dye-sensitized hydrogen production systems. All the prepared compounds had a phenothiazine and a cyanoacrylic acid/pyridinyl acrylonitrile moiety acting as an electron donor and acceptor, respectively. Although cyclic voltammetry measurements showed similar electron-donating properties among all the synthesized dyads, the lowest absorption energy of the [2.2]PCP moiety was lower than that of the [3.3]PCP one; this was due to its shorter distance between benzene rings, which could effectively drive the charge transfer between the donor and acceptor chromophores. Under visible light (>395 nm), a dyad-loaded photocatalyst in a 0.5 M aqueous glycerol solution generated detectable hydrogen gases. The optimal turnover number and photocurrent order exhibited the same trend as the hydrogen production rate since the suggested number of excited photons played a critical role in hydrogen production.

Heptacene: Synthesis and Its Hole-Transfer Property in Stable Thin Films.

Heptacene (1) has been produced via a monoketone precursor, 2, which was prepared from 1,2,4,5-tetrabromobenzene in nine steps in a total yield of 10 %. Compound 2 was converted to 1 quantitatively by heating at 202 °C. Heptacene exhibited high thermal stability in the solid state without any observable change over two months. To investigate the potential value of 1 as a material for p-type organic field-effect transistors (OFETs), top-contact OFET devices were fabricated by vacuum deposition of 1 onto a hexamethyldisilazane (HMDS)/SiO2 /Si substrate. The best hole mobility performance was 2.2 cm2  V-1 s-1 . This is the first report of stable heptacene being used in an effective device and examined for its charge carrier properties.

Photo-biohydrogen Production by Photosensitization with Biologically Precipitated Cadmium Sulfide in Hydrogen-Forming Recombinant Escherichia coli.

An inorganic-biological hybrid system that integrates features of both stable and efficient semiconductors and selective and efficient enzymes is attractive for facilitating the conversion of solar energy to hydrogen. In this study, we aimed to develop a new photocatalytic hydrogen-production system based on Escherichia coli whole-cell genetically engineered as a biocatalysis for highly active hydrogen formation. The photocatalysis part was obtained by bacterial precipitation of cadmium sulfide (CdS), which is a visible-light-responsive semiconductor. The recombinant E. coli cells were sequentially subjected to CdS precipitation and heterologous [FeFe]-hydrogenase synthesis to yield a CdS@E. coli hybrid capable of light energy conversion and hydrogen formation in a single cell. The CdS@E. coli hybrid achieved photocatalytic hydrogen production with a sacrificial electron donor, thus demonstrating the feasibility of our system and expanding the current knowledge of photosensitization using a whole-cell biocatalyst with a bacterially precipitated semiconductor.

Characteristics of crystalline sputtered LaFeO3 thin films as photoelectrochemical water splitting photocathodes.

Stable photoelectrochemical (PEC) operation is a critical issue for the commercialization of PEC water-splitting systems. Unfortunately, most semiconductor photocathodes generating hydrogen in these systems are unstable in aqueous solutions. This is a huge limitation for the development of durable PEC water-splitting systems. Lanthanum iron oxide (LaFeO3) is a promising p-type semiconductor to overcome this drawback because of its stability in an aqueous solution and its proper energy level for reducing water. In this study, we fabricated a crystalline LaFeO3 thin film by radio frequency magnetron sputtering deposition and a post-annealing process in air for use as a PEC photocathode. Based on the morphological, compositional, optical and electronic characterizations, we found that it was ideal for a visible light-responsive PEC photocathode and tandem PEC water-splitting system with a small band gap absorber behind it. Furthermore, it showed stable PEC performance in a strong alkaline solution during PEC operation without any protection layers. Therefore, the crystalline sputtered LaFeO3 thin film suggested in this study would be feasible to apply as a PEC photocathode for durable, simple and low-cost PEC water splitting.

Single-Electron-Trapped Oxygen Vacancy on Ultrathin WO3·0.33H2O {100} Facets Suppressing Backward Reaction for Promoted H2 Evolution in Pure Water Splitting.

Solar water splitting to produce hydrogen is a promising solution for global energy issues. One of the main bottlenecks in this technology is the spontaneous fast backward reaction (2H2 + O2 → H2O, Δ G < 0), limiting the solar energy conversion efficiency. How to suppress backward reaction is vitally important but rarely reported. Here we found that single-electron-trapped oxygen vacancy (Vo·) can suppress spontaneous backward reaction in pure water splitting. Taking WO3·0.33H2O catalyst as an example, ultrathin WO3·0.33H2O {100} facets with large amount of surface Vo· realized a continuous H2 evolution from pure water splitting with a productivity of 9.9 µmol/g·h without the assistance of any sacrifice agent and noble metal cocatalyst. Quantum chemical calculations revealed that the backward-reaction suppression ability of Vo· is attributed to the high concentration of localized electrons around Vo·, stimulating unidirectional simultaneous water dissociation into H and OH under light irradiation.

A Cocatalyst that Stabilizes a Hydride Intermediate during Photocatalytic Hydrogen Evolution over a Rhodium-Doped TiO2 Nanosheet.

The hydrogen evolution reaction using semiconductor photocatalysts has been significantly improved by cocatalyst loading. However, there are still many speculations regarding the actual role of the cocatalyst. Now a photocatalytic hydrogen evolution reaction pathway is reported on a cocatalyst site using TiO2 nanosheets doped with Rh at Ti sites as one-atom cocatalysts. A hydride species adsorbed on the one-atom Rh dopant cocatalyst site was confirmed experimentally as the intermediate state for hydrogen evolution, which was consistent with the results of density functional theory (DFT) calculations. In this system, the role of the cocatalyst in photocatalytic hydrogen evolution is related to the withdrawal of photo-excited electrons and stabilization of the hydride intermediate species; the presence of oxygen vacancies induced by Rh facilitate the withdrawal of electrons and stabilization of the hydride.

Donor-Donor'-Acceptor Triads Based on [3.3]Paracyclophane with a 1,4-Dithiafulvene Donor and a Cyanomethylene Acceptor: Synthesis, Structure, and Electrochemical and Photophysical Properties.

Donor-donor'-acceptor triads (1, 2), based on [3.3]paracyclophane ([3.3]PCP) as a bridge, with electron-donating properties (D') using 1,4-dithiafulvene (DTF; TTF half unit) as a donor and dicyanomethylene (DCM; TCNE half unit) or an ethoxycarbonyl-cyanomethylene (ECM) as an acceptor were designed and synthesized. The pulse radiolysis study of 1 a in 1,2-dichloroethane allowed the clear assignment of the absorption bands of the DTF radical cation (1 a.+ ), whereas the absorption bands due to the DCM radical anion could not be observed by γ-ray radiolysis in 2-methyltetrahydrofuran rigid glass at 77 K. Electrochemical oxidation of 1 a first generates the DTF radical cation (1 a.+ ), the absorption bands of which are in agreement with those observed by a pulse radiolysis study, followed by dication (1 a2+ ). The ESR spectrum of 1 a.+ showed a symmetrical signal with fine structure and an ESR simulation predicted that the spin of 1 a.+ is delocalized over S and C atoms of the DTF moiety and the central C atom of the trimethylene bridge bearing the DTF moiety. Pulse radiolysis, ESR, and electrochemical studies indicate that the DTF radical cation of 1 a.+ is more stable than that of 6.+ , and the latter shows a strong tendency to dimerize. This result indicates that the [3.3]PCP moiety as a bridge can stabilize the DTF radical cation more than the 1,3-diphenylpropane moiety because of kinetic stability due to its rigid structure and the weak electronic interaction of DTF and DCM moieties through [3.3]PCP.

Ultrathin WO3·0.33H2O Nanotubes for CO2 Photoreduction to Acetate with High Selectivity.

Artificial photosynthesis from CO2 reduction is severely hampered by the kinetically challenging multi-electron reaction process. Oxygen vacancies (Vo) with abundant localized electrons have great potential to overcome this limitation. However, surface Vo usually have low concentrations and are easily oxidized, causing them to lose their activities. For practical application of CO2 photoreduction, fabricating and enhancing the stability of Vo on semiconductors is indispensable. Here we report the first synthesis of ultrathin WO3·0.33H2O nanotubes with a large amount of exposed surface Vo sites, which can realize excellent and stable CO2 photoreduction to CH3COOH in pure water under solar light. The selectivity for acetum generation is up to 85%, with an average productivity of about 9.4 µmol g-1 h-1. More importantly, Vo in the catalyst are sustainable, and their concentration was not decreased even after 60 h of reaction. Quantum chemical calculations and in situ DRIFT studies revealed that the main reaction pathway might be CO2 → •COOH → (COOH)2 → CH3COOH.

Synthesis and physical properties of brominated hexacene and hole-transfer properties of thin-film transistors.

A halide-substituted higher acene, 2-bromohexacene, and its precursor with a carbonyl bridge moiety were synthesized. The precursor was synthesized through 7 steps in a total yield of 2.5%. The structure of precursor and thermally converted 2-bromohexacene were characterized by solid state NMR, IR, and absorption spectra, as well as by DFT computation analysis. It exhibited high stability in the solid state over 3 months, therefore can be utilized in the fabrication of opto-electronic devices. The organic thin-film transistors (OFETs) were fabricated by using 2-bromohexacene and parent hexacene through vaccum deposition method. The best film mobility of 2-bromohexacene was observed at 0.83 cm2 V-1 s-1 with an on/off ratio of 5.0 × 104 and a threshold of -52 V, while the best film mobility of hexacene was observed at 0.076 cm2 V-1 s-1 with an on/off ratio of 2.4 × 102 and a threshold of -21 V. AFM measurement of 2-bromohexacene showed smooth film formation. The averaged mobility of 2-bromohexacene is 8 fold higher than the non-substituted hexacene.

Dye-sensitized photocatalyst for effective water splitting catalyst.

Renewable hydrogen production is a sustainable method for the development of next-generation energy technologies. Utilising solar energy and photocatalysts to split water is an ideal method to produce hydrogen. In this review, the fundamental principles and recent progress of hydrogen production by artificial photosynthesis are reviewed, focusing on hydrogen production from photocatalytic water splitting using organic-inorganic composite-based photocatalysts.

Synthesis of 1,2-Bis(2-aryl-1H-indol-3-yl)ethynes via 5-exo-Digonal Double Cyclization Reactions of 1,4-Bis(2-isocyanophenyl)buta-1,3-diyne with Aryl Grignard Reagents.

New π-conjugated 1,2-bis(2-aryl-1H-indol-3-yl)ethynes 1a-j having various substituents on the two aryl groups were efficiently synthesized via unusual 5-exo-digonal double isocyanide-acetylene cyclization reactions of 1,4-bis(2-isocyanophenyl)buta-1,3-diyne 3 and aryl Grignard reagents (R-MgBr, R = C6H5 (1a), 4-H3CC6H4 (1b), 2-H3CC6H4 (1c), 3-MeOC6H4 (1d), 3-(CH3)2NC6H4 (1e), 4-F3CC6H4 (1f), 4-FC6H4 (1g), 3-FC6H4 (1h), 4-PhOC6H4 (1i), and 2-Naph (1j)) in 19-85% yields. The UV-vis spectra were rationalized in detail using time-dependent DFT and single point calculations. The fluorescence emission peaks for 1a-j were observed at around 450 nm. Especially for 1f and 1j, those spectra displayed broad emission bands and relatively large Stokes shifts (3977-4503 cm-1), indicating the contribution of an intramolecular charge transfer. The absolute quantum yields (0.50-0.62) of 1a-j were higher than those of parent 8 (0.19) and 2-phenyl-1H-indole (0.11). The electrochemical features for 1a-j were investigated by cyclic voltammetry. The frontier molecular orbital levels for 1a-j were estimated based on the combination of oxidation potentials, UV-vis, and DFT calculated data. The structural property of 1,2-bis(2-phenyl-1H-indol-3-yl)ethyne 1a was characterized by several spectroscopic methods and finally determined by X-ray analysis of a single crystal of 1a recrystallized from ethyl acetate. The structural features of 1a-j were also supported by DFT calculations.

Synthesis and Investigation of the Effect of Substitution on the Structure, Physical Properties, and Electrochemical Properties of Anthracenodifuran Derivatives.

A series of syn/anti mixtures of anthradifuran (ADF) and substituent compounds were systematically synthesized, and the effect of substitution at the 5,11-positions on the neutral and radical states of ADF was investigated. All compounds were measured and analyzed by absorption and fluorescence spectroscopy, cyclic voltammetry, electrochemical absorption spectroscopy, and DFT calculations. The absorption spectra of 5,11-substituent compounds in their neutral state were red-shifted. In addition, the substituted compounds exhibited increased thermal stability with respect to the parent 1a because of elongation of the π-conjugation and an increased steric hindrance effect due to the bulky ethynyl substituent groups. The cyclic voltammograms of all of the compounds exhibited irreversible reduction potentials and irreversible oxidation potentials, except in the case of (trimethylsilyl)silylethynyl-substituted ADF. When the materials were subjected to oxidation/reduction potentials, the radical cation and anion species were generated. The absorption spectra of the radical-cation species of the compounds exhibited similar characteristics and similar absorption ranges (550-1400 nm), whereas the spectra of the radical anion species were blue-shifted (550-850 nm) compared than that of the parent 1a(•-) (550-1100 nm). The DFT computation results suggested that the radical states of lowest energy transitions occurred primarily from π to π(SOMO) or from π(SOMO) to π*.

Crystal structure of a four-layered [3.3](3,5)pyridino-phane.

The title compound, C40H46N2 {systematic name: 12,30-di-aza-hepta-cyclo[21.13.1.1(5,19).1(6,18).1(10,14).1(24,36).1(28,32)]do-tetra-conta-1(37),5(40),6(41),10(42),11,13,18,23,28,30,32(39),36(38)-dodeca-ene}, has syn-anti-syn geometry wherein the two outer [3.3]meta-cyclo-phane (MCP) moieties have a syn geometry, and contain the facing benzene and pyridine rings at dihedral angles of 26.26 (10) and 26.46 (10)°, respectively. The rings of the central [3.3]MCP unit are not parallel, but orientated at a slight angle of 2.66 (9)°. Three bridging methyl-ene groups are disordered over two sets of sites in a 0.60:0.40 ratio. In the crystal, the mol-ecules are linked by C-H⋯N inter-actions and inter-molecular C-H⋯π short contacts, generating a three-dimensional network.

Synthesis and electronic and photophysical properties of [2.2]- and [3.3]paracyclophane-based donor-donor'-acceptor triads.

Three types of the donor(D)-donor'(D')-acceptor(A) triads 1-6 with different D-A combinations, carbazole (Cz, D)-[n.n]PCP(D')-1,8-naphthalimide (NI, A) (1-3), 10H-phenothiazine (PTZ, D)-[n.n]PCP(D')-NI(A) (4, 5), and 10-methyl-10H-phenothiazine (Me-PTZ, D)-[2.2]PCP-2,1,3-benzothiadiazole (BTD, A) 6, were synthesized for the elucidation of their photophysical properties. The absorption spectra and electrochemical properties indicated that the chromophores (D, D', and A) do not interact with each other in the ground state. Cz-(CH2)3-[2.2]PCP-(CH2)3-NI 1 and Cz-(CH2)3-[3.3]PCP-(CH2)3-NI 2 show an exciplex emission between the PCP and NI moieties in cyclohexane and the intensity of the band is much higher in 2 than in 1, whereas Cz-(CH2)2-[2.2]PCP-(CH2)2-NI 3 does not show any exciplex emission in cyclohexane. These results indicated that the combination of [3.3]PCP and a trimethylene chain is preferable for the exciplex formation. PTZ-(CH2)3-[2.2]PCP-(CH2)3-NI 4 shows a broad band at 519 nm in cyclohexane, which is associated with the formation of the exterplex band among the NI, [2.2]PCP, and PTZ moieties, while PTZ-(CH2)3-[3.3]PCP-(CH2)3-NI 5 does not show the band. Me-PTZ-(CH2)2-[2.2]PCP-(CH2)2-BTD 6 shows a broad fluorescence band due to both the BTD and PTZ moieties in cyclohexane. In CH3CN, the fluorescence spectra of 1-6 suggest the presence of a photoinduced charge separation process. The study of the photoinduced charge separation process will be soon reported elsewhere.

Crystal structure of (E)-2-cyano-3-(12-methyl-12H-benzo[b]pheno-thia-zin-11-yl)acrylic acid.

In the title compound, C21H14N2O2S, a donor-acceptor type of benzo[b]pheno-thia-zine (bpz) derivative, the thia-zine ring adopts a boat conformation and the bond-angle sum at the N atom is 360.0°. The dihedral angle between the benzene ring and the naphthelene ring system fused to the thia-zine ring is 32.76 (5)°. In the crystal, carb-oxy-lic-acid inversion dimers linked by pairs of O-H⋯O hydrogen bonds generate R 2 (2)(8) loops. Aromatic π-π stacking [shortest centroid-centroid separaton = 3.5242 (13)Å] consolidates the structure and very weak C-H⋯O and C-H⋯N inter-actions also occur.

Modification effects of meso-hexakis(pentafluorophenyl) [26]hexaphyrin aggregates on the photocatalytic water splitting.

Water splitting activity of a GaN:ZnO photocatalyst was improved by meso-hexakis(pentafluorophenyl) [26]hexaphyrin (3). The hexaphyrin (3) assisted the water splitting reaction over the GaN:ZnO photocatalyst by using visible light energy around 600 nm.

Four-layered [3.3]meta-cyclo-phane with ethene-tetra-carbo-nitrile.

The title complex C42H48·2C6N4 {systematic name: hepta-cyclo[21.13.1.1(5,19).1(6,18).1(10,14).1(24,36).1(28,32)]do-tetra-conta-1(37),5(40),6(41),10(42),11,13,18,23,28,30,32(39),36(38)-dodeca-ene-ethene-tetra-carbo-nitrile (1/2)}, consisting of four-layered [3.3]meta-cyclo-phane (MCP) with two tetra-cyano-ethyl-ene (TCNE) mol-ecules, was grown from a mixture of MCP and TCNE in chloro-form solution. The four-layered [3.3]MCP has an S-shaped structure in which three [3.3]MCP moieties take syn-(chair-boat), anti-(chair-boat) and syn-(chair-boat) conformations. The two outer [3.3]MCP moieties with syn geometry contain benzene rings with a tilt of 32.95 (7)°. The central [3.3]MCP moiety has an anti geometry, in which the two benzene rings are oriented parallel to each other at a transannular distance of 2.31 Å. The TCNE mol-ecules are stacked on either side of the outer [3.3]MCP units at a distance of 3.19 Šon one side and 3.24 Šon the other, and showed 0.80:0.20 and 0.44:0.56 disorder, respectively.