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We report on experimental determination of the strain and bandgap of InAsP in epitaxially grown InAsP-InP core-shell nanowires. The core-shell nanowires are grown via metal-organic vapor phase epitaxy. The as-grown nanowires are characterized by transmission electron microscopy, X-ray diffraction, micro-photoluminescence (mu PL) spectroscopy, and micro-Raman (mu-Raman) spectroscopy measurements. We observe that the core-shell nanowires are of wurtzite (WZ) crystal phase and are coherently strained with the core and the shell having the same number of atomic planes in each nanowire. We determine the predominantly uniaxial strains formed in the core-shell nanowires along the nanowire growth axis and demonstrate that the strains can be described using an analytical expression. The bandgap energies in the strained WZ InAsP core materials are extracted from the mu PL measurements of individual core-shell nanowires. The coherently strained core-shell nanowires demonstrated in this work offer the potentials for use in constructing novel optoelectronic devices and for development of piezoelectric photovoltaic devices., Funding Agencies|Myfab; Swedish Research Council (VR); Ministry of Science and Technology of China through the National Key Research and Development Program of China [2017YFA0303304, 2016YFA0300601]; National Natural Science Foundation of China [11874071, 91221202, 91421303]

This paper describes the preparation and the characterization of a photovoltaic cell based on the sensitization of a wide band gap p-type semiconductor (NiO) with a phosphorus porphyrin. A photophysical study with femtosecond transient absorption spectroscopy showed that light excitation of the phosphorus porphyrin chemisorbed on NiO particles induces a very rapid interfacial hole injection into the valence band of NiO, occurring mainly on the 2-20 ps time scale. This is followed by a recombination in which ca. 80% of the ground-state reactants are regenerated within 1 ns. A photoelectrochernical device, prepared with a nanocrystalline NiO electrode coated with the phosphorus porphyrin, yields a cathodic photocurrent indicating that electrons indeed flow from the NiO electrode toward the solution. The low incident-to-photocurrent efficiency (IPCE) can be rationalized by the rapid back recombination reaction between the reduced sensitizer and the injected hole which prevents an efficient regeneration of the sensitizer ground state from the iodide/triiodide redox mediator. To the best of our knowledge, this work represents the first example of a photovoltaic cell in which a mechanism of hole photoinjection has been characterized., QC 20100525

To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these compl plexes, a mixed-valent dinuclear Ru-2(II,III) moiety with one phenoxy and two acetato bridges is covalently linked to a Ru-II tris-bipyridine photosensitizer. The properties and photoinduced electron/energy transfer of these complexes were studied. The results show that the Ru-2(II,III) moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru-2(II,II) and Ru-2(II,III) states, respectively. This could allow for photooxidation of the sensitizer part with an external acceptor and subsequent electron transfer from the dinuclear ruthenium moiety to regenerate the sensitizer. However, all trinuclear ruthenium complexes have a very short excited-state lifetime, in the range of a few nanoseconds to less than 100 ps. Studies by femtosecond time-resolved techniques suggest that a mixture of intramolecular energy and electron transfer between the dinuclear ruthenium moiety and the excited [Ru(bpy)(3)](2+) photosensitizer is responsible for the short lifetimes. This problem is overcome by anchoring the complexes with ester- or carboxyl-substituted bipyridine ligands (2a, 2b) to nanocrystalline TiO2, and the desired electron transfer from the excited state of the [Ru(bPY)(3)](2+) moiety to the conduction band of TiO2, followed by intramolecular electron transfer from the dinuclear Ru-2(II,III) moiety to photogenerated Ru-III was observed. The resulting long-lived Ru-2(III,III) state decays on the millisecond timescale., QC 20100525

A model of the iron hydrogenase active site with the structure [(mu-ADT)Fe-2(CO)(6)] (ADT = azadithiolate (S-CH2-NR-CH2-S), (2: R = 4-bromophenyl, 3: R = 4-iodophenyl)) has been assembled and covalently linked to a [Ru(terpy)(2)](2+) photosensitizer. This trinuclear complex 1 represents one synthetic step toward the realization of our concept of light-driven proton reduction. A rigid phenylacetylene tether has been incorporated as the linking unit in 1 in order to prolong the lifetime of the otherwise short-lived [Ru(terpy)(2)](2+) excited state. The success of this strategy is demonstrated by comparison of the photophysical properties of 1 and of two related ruthenium complexes bearing acetylenic terpyridine ligands, with those of [Ru(terpy)(2)](2+). IR and electrochemical studies reveal that the nitrogen heteroatom of the ADT bridge has a marked influence on the electronic properties of the [Fe-2(CO)(6)] core. Using the Rehm-Weller equation, the driving force for an electron transfer from the photoexcited *[Ru(terpy)(2)](2+) to the diiron site in 1 was calculated to be uphill by 0.59 eV. During the construction of the trinuclear complex 1, n-propylamine has been identified as a decarbonylation agent on the [(mu-ADT)Fe-2(CO)(6)] portion of the supermolecule. Following this procedure, the first azadithiolate-bridged dinuclear iron complex coordinated by a phosphine ligand [(mu-ADT)Fe-2(CO)(5)PPh3] (4, R = 4-bromophenyl) was synthesized., QC 20100525

A terpyridine ligand has been covalently linked to a Ru(bpy)(3) complex via an amide bond. By using this functionalized terpyridine ligand, a series of multinuclear bimetallic complexes have been synthesized and characterized. One of these complexes has the structure of di-mu-oxobridged Mn dimer. EPR spectra of this complex showed that, depending on the procedure for the preparation, the oxidation states of the Mn dimer is either a Mn-2(III,IV) dimer or a mixture of this and Mn-2(IV,IV) dimer. Water oxidation catalyzed by this complex has been performed., QC 20100525

Long-lived charge-separated states in the ns to mus range were observed upon laser flash excitation of a donor-chromophore-acceptor triad based on tris(bipyridine) ruthenium(II) as photosensitizer, naphthalene diimide as acceptor; and a hydrogen bonded phenol as donor., QC 20100525

Two electron donor-acceptor triads based on a benzoquinone acceptor linked to a light absorbing [Ru(bpy)(3)](2+) complex have been synthesized. In triad 6 (denoted Ru-II-BQ-Co-III), a [Co(bpy)(3)](3+) complex, a potential secondary acceptor, was linked to the quinone. In the other triad, 8 (denoted PTZ-Ru-II-BQ), a phenothiazine donor was linked to the ruthenium moiety. The corresponding dyads Ru-II-BQ (4) and PTZ-Ru-II (9) were prepared for comparison. Upon light excitation in the visible band of the ruthenium moiety, electron transfer to the quinone occurred with a rate constant k(1) = 5 x 10(9) s(-1) (tau(1) = 200 ps) in all the quinone containing complexes. Recombination to the ground state followed, with a rate constant k(b) similar to 4.5 x 10(8) s(-1) (tau(b) similar to 2.2 ns), for both Ru-II-BQ and Ru-II-BQ-Co-III with no indication of a charge shift to generate the reduced Coll moiety. In the PTZ-Ru-II-BQ triad, however, the initial charge separation was followed by a rapid (k > 5 x 10(9) s(-1)) electron transfer from the phenothiazine moiety to give the fairly long-lived PTZ(.+)-Ru-II-BQ(.-) state (tau = 80 ns) in unusually high yield for a [Ru(bPY)(3)](2+)- based triad (> 90%), that lies at DeltaGdegrees = 1.32 eV relative to the ground state. Unfortunately, this triad turned out to be rather photolabile. Interestingly, coupling between the oxidized PTZ(.+) and the BQ(.-) moieties seemed to occur. This discouraged further extension to incorporate more redox active units. Finally, in the dyad PTZ-Ru-II a reversible, near isoergonic electron transfer was observed on excitation. Thus, a quasiequilibrium was established with an observed time constant of 7 ns, with ca. 82% of the population in the PTZ-Ru-*(II) state and 18% in the PTZ(.+)Ru(II)(bpy(.-)) state. These states decayed in parallel with an observed lifetime of 90 ns. The initial electron transfer to form the PTZ(.+)-Ru-II(bpy(.-)) state was thus faster than what would have been inferred from the Ru, QC 20100525

Two series of photosensitizer-electron acceptor complexes have been synthesized and fully characterized: ruthenium(11) tris(bipyridine) {[Ru-II(bpy)(2)(bpy-X-NDI)], where X = -CH2-, tolylene, or phenylene, bpy is 2,2'-bipyridine, and NDI is naphthalenediimide} and ruthenium(II) bis(terpyridine) {[Ru-II(Y-tpy)(tpy-X-NDI)], where Y = H or tolyl and X = tolylene or phenylene, and tpy = 2,2':6',2-terpyridine}. The complexes have been studied by cyclic and differential pulse voltammetry and by steady state and time-resolved absorption and emission techniques. Rates for forward and backward electron transfer have been investigated, following photoexcitation of the ruthenium(II) polypyridine moiety. The terpyridine complexes were only marginally affected by the linked diimide unit, and no electron transfer was observed. In the bipyridine complexes we achieved efficient charge separation. For the complexes containing a phenyl link between the ruthenium(II) and diimide moieties, our results suggest a biphasic forward electron-transfer reaction, in which 20% of the charge-separated state was formed via population of the naphthalenediimide triplet state., QC 20100525

A dinuclear iron complex, related to the active site of Fe hydrogenases, has been covalently linked to a redox active ruthenium tris-bipyridine type photosensitizer. Photophysics and electrochemistry of this system are studied in solution. IR spectra of this complex together with its precursor, the dinuclear iron complex, were also shown., QC 20100525