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We explore the structure of the energy spectra of quasi-one dimensional organic conductors subjected to the field-induced spin-density-wave (FISDW) state. We show that the structure of the energy spectra can exhibit Hofstadter butterfly, which is generally believed to appear in two dimensional systems. The phenomenon of the quantized Hall conductance due to FISDW is also investigated. We find that the Hall number L, which is defined by L = σxy/(e²/h), coincides with the number described by FISDW order parameter. The sign reversal of the quantized Hall conductance is discussed theoretically. [ABSTRACT FROM AUTHOR]

A detailed analysis of photoluminescence (PL) from InP quantum dots (QDs) grown on Si has been carried out to understand the effect of substrate/host material in the luminescence and carrier escape process from the surface quantum dots. Such studies are required for the development of monolithically integrated next generation III-V QD based optoelectronics with fully developed Si microelectronics. The samples were grown by atmospheric pressure metalorganic chemical vapor deposition technique, and the PL measurements were made in the temperature range 10-80K. The distribution of the dot diameter as well as the dot height has been investigated from atomic force microscopy. The origin of the photoluminescence has been explained theoretically. The band alignment of InP/Si heterostructure has been determined, and it is found be type II in nature. The positions of the conduction band minimum of Si and the 1st excited state in the conduction band of InP QDs have been estimated to understand the carrier escape phenomenon. A blue shift with a temperature co-efficient of 0.19meV/K of the PL emission peak has been found as a result of competitive effect of different physical processes like quantum confinement, strain, and surface states. The corresponding effect of blue shift by quantum confinement and strain as well as the red shift by the surface states in the PL peaks has been studied. The origin of the luminescence in this heterojunction is found to be due to the recombination of free excitons, bound excitons, and a transition from the 1st electron excited state in the conduction band (e1) to the heavy hole band (hh1). Monotonic decrease in the PL intensity due to increase of thermally escaped carriers with temperature has been observed. The change in barrier height by the photogenerated electric-field enhanced the capture of the carriers by the surface states rather than their accumulation in the QD excited state. From an analysis of the dependence of the PL intensity, peak position, and line width with temperature and excitation source, the existence of free and bound excitonic recombination together with e1 →hh1 transitions in the QDs is established. [ABSTRACT FROM AUTHOR]

The ¹JCC and ¹JCH spin-spin coupling constants have been calculated by means of density functional theory (DFT) for a set of derivatives of aliphatic hydrocarbons substituted with I, At, Cd, and Hg in order to evaluate the substituent and relativistic effects for these properties. The main goal was to estimate HALA (heavy-atom-on-light-atom) effects on spin-spin coupling constants and to explore the factors which may influence the HALA effect on these properties, including the nature of the heavy atom substituent and carbon hybridization. The methods applied range, in order of reduced complexity, from Dirac-Kohn-Sham method (density functional theory with four-component Dirac-Coulomb Hamiltonian), through DFT with two- and one-component Zeroth Order Regular Approximation (ZORA) Hamiltonians, to scalar non-relativistic effective core potentials with the non-relativistic Hamiltonian. Thus, we are able to compare the performance of ZORA-DFT and Dirac-Kohn-Sham methods for modelling of the HALA effects on the spin-spin coupling constants. [ABSTRACT FROM AUTHOR]

Native defects in InxGa1-xN layers grown by metalorganic chemical vapor deposition were studied using monoenergetic positron beams. Measurements of Doppler broadening spectra of the annihilation radiation and lifetime spectra of positrons for a 200-nm-thick In0.13Ga0.87N layer showed that vacancy-type defects were introduced by InN alloying, and the major species of such defects was identified as complexes between a cation vacancy and nitrogen vacancies. The presence of the defects correlated with lattice relaxation of the In0.13Ga0.87N layer and the increase in photon emissions from donor-acceptor-pair recombination. The species of native defects in In0.06Ga0.94N layers was the same but its concentration was decreased by decreasing the InN composition. With the layer thickness increased from 120 nm to 360 nm, a defect-rich region was introduced in the subsurface region (<160 nm), which can be associated with layer growth with the relaxation of compressive stress. [ABSTRACT FROM AUTHOR]

Luminescence dynamics for the near-band-edge (NBE) emission peak at around 250 nm of c-plane Si-doped Al0.6Ga0.4N films grown on AlN templates by low-pressure metalorganic vapor phase epitaxy were studied using deep ultraviolet time-resolved photoluminescence and time-resolved cathodoluminescence spectroscopies. For the films with the Si-doping concentration, [Si], lower than 1.9 × 1017 cm-3, the doping lessened the concentration of cation vacancies, [VIII], through the surfactant effect or the aid of the reactant doping in a form of H3SiNH2. However, the room-temperature nonradiative lifetime, and, consequently, the equivalent value of internal quantum efficiency in the weak excitation regime steeply decreased when [Si] exceeded 1018 cm-3. Simultaneously, the intensity ratio of the deep-state emission band to the NBE emission abruptly increased. Because the increase in [Si] essentially gives rise to the increase in [VIII] (for [Si]>1.9×1017 cm-3) and the overcompensation of Si is eventually observed for the film with [Si] = 4.0 × 1018 cm-3, the formation of acceptor-type native-defect complexes containing Si such as VIII-SiIII is suggested. [ABSTRACT FROM AUTHOR]

A novel serpentine channel structure is used to mask the sapphire substrate for the epitaxial growth of dislocation-free GaN. Compared to the existing epitaxial lateral overgrowth methods, the main advantages of this novel technique are: (a) one-step epitaxial growth; (b) up to 4 times wider defect-free regions; and (c) the as-grown GaN film can be transferred easily to any type of substrate. TEM, etch pits and cathodoluminescence experiments are conducted to characterize the quality of as-grown GaN. The results show that the average etch-pit density in the yet-to-be-optimized GaN epi-layers is about 4 × 105 cm-2. The underlying physics of selective nucleation and growth is investigated using the finite element method (COMSOL). It is concluded that the proximity effect dominates the selective growth of GaN on the serpentine channel structure masked sapphire. This novel technique is a promising candidate for the growth of high quality III-nitride and the subsequent high-performance device fabrication including high brightness LED, laser diodes, and high-power, high-efficiency transistors. [ABSTRACT FROM AUTHOR]

The aims of this study are (i) to demonstrate the synthesis of Cr3+-activated β-Ga2O3 films by metal-organic deposition and (ii) to report the temperature-dependent photoluminescence (PL) properties of such films from 20 to 300 K. An activation energy of ∼0.9 eV for the Cr3+ ions in β-Ga2O3 is determined from a plot of PL intensity vs calcination temperature. The red-line emission doublet R1 and R2 at ∼1.8 eV and the broad emission band with a peak at ∼1.7 eV are ascribed to the Cr3+ ions in the β-Ga2O3 host. The energies of the excited states, i.e., 2E, 4T2, 2T2, 4T1, and 4T1, in Cr3+ are determined from the experimental PL and PL excitation spectra using a newly developed analysis model. The high-energy luminescence tail of the broad 4T2 → 4A2 emission band can be explained by the hot-carrier effect of the photoexcited electrons in the 4T2 state. The relative intensities of the R-line emission doublet can also be explained very well by the population and depopulation of the electron numbers in the [formula] (R1) and [formula] (R2) states. PL properties, such as the temperature-dependent PL intensity, peak energy, and spectral width, are analyzed in detail. [ABSTRACT FROM AUTHOR]

We report the observation of photoluminescence (PL) transitions in ZnO epilayers grown by metalorganic vapor phase epitaxy (MOVPE) on C-sapphire substrates with linewidths as low as 0.2 meV at 4.2 K. A dominant donor bound exciton (D0X) peak at 3361.0 meV is observed in all undoped samples together with the corresponding ionized donor bound exciton (D+X) peak at 3372.9 meV. The addition of In dopant using trimethylindium results in the appearance of the I9 transition at 3357.8 meV, which has been previously attributed to In D0X transitions. By intentionally doping the epilayers with In we can calibrate the PL energy spectra, and thereby identify the dominant D0X transition in undoped material at 3361.0 meV as due to Ga donors. The In and Ga identifications are also confirmed by the observation of two electron satellites. High temperature annealing under O2 results in a strong reduction of the In and Ga transitions, and the appearance of a third line which we attribute to Al out-diffusing from the sapphire substrate. Temperature dependent PL measurements on In-doped samples above 4 K show additional lines due to well-resolved D0X (B) transitions separated by 4.6 meV for both Ga and In donors due to the crystal field splitting of the valence band. The line intensities are modeled by simple Boltzmann statistics. On the basis of comparison with accepted values of the I9 transition energy in homoepitaxial ZnO samples, we deduce a strain-induced blueshift of ∼ 1.2 meV which is consistent with residual compressive strain induced in the ZnO films due to the smaller in-plane effective lattice constant of sapphire. [ABSTRACT FROM AUTHOR]

InGaN epitaxial films grown by metalorganic chemical vapor deposition using trimethylgallium and triethylgallium as precursors exhibited different optical and electrical properties. The films were characterized by x-ray diffraction, photoluminescence, secondary ion mass spectroscopy, and atomic force microscopy. Impacts of unactivated Mg-doped GaN in situ grown cap layers on InGaN and GaN films were further investigated. Current-voltage and spectral response measurements combined with Hall-effect measurement and analytical modeling have been used to assess possible current transport mechanisms of reverse dark and photo current flow in metal-semiconductor-metal photodetectors fabricated from InGaN and GaN. Unlike the dominant thermionic emission, which can be blocked by higher and thicker potential barrier in GaN, the trap-assisted tunneling is more pronounced in InGaN. The passivation effect on high density surface states in InGaN is proposed to explain the improved device performances after the incorporation of Mg-doped GaN. [ABSTRACT FROM AUTHOR]

AlGaN/GaN-based high electron mobility transistor heterostructures with different GaN cap layer thicknesses were grown by metalorganic vapor phase epitaxy (MOVPE) and molecular beam epitaxy. The influence of the different growth methods on the structure of the GaN caps was examined by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Due to the high surface sensitivity of these methods, several effects, such as residual Al incorporation into the GaN cap during growth, etching of the GaN cap during cool-down, and preferential etching of Ga out of the AlGaN barrier could be evaluated. It is demonstrated that these effects play a major role for MOVPE-grown structures. [ABSTRACT FROM AUTHOR]

Monodispersed ferrite nanoparticles of Fe3O4, MnFe2O4, and CoFe2O4 (near to 10 nm), were synthesized by organometallic synthesis, showing the same homogeneous chemical, morphological, and crystalline characteristics. The study and correlation of the thermal relaxation processes were analyzed through static and dynamic measurements. Due to the intrinsic chemical characteristics and magnetocrystalline anisotropy of the ferrite nanoparticles, the energy barrier can be tuned to a range between 1100 K ≤ EB ≤ 7300 K, showing an alternative approach for tuning the magnetic dynamic properties, in contrast to the well-known mechanism through particle-size-effects. Specific loss power efficiencies were evaluated for the three ferrite samples. Comparing the three samples at the maximum ac frequency of ν = 10 kHz, MnFe2O4 exhibits the single-peak maximum of loss with the value of 273 erg/s · g at T = 65 K, whereas for the CoFe2O4, a maximum of 132 erg/s · g (T = 217 K) was determined. A considerable drop in the efficiency was determined for the Fe3O4 nanoparticles, with the value of 20 erg/s · g at T = 43.5 K. [ABSTRACT FROM AUTHOR]

In this article several kinetic effects are proposed that induce compositional instabilities in thick InGaN heteroepitaxial layers on GaN templates grown by metalorganic chemical vapor deposition. It was found that by reducing the growth temperature, or increasing the growth rate, or introducing Mg doping, the epitaxial layer changes from a pseudomorphic InGaN with a low indium mole fraction to a relaxed InGaN with a high indium mole fraction. In certain circumstances, both phases can be present in a single layer. The composition and strain inhomogeneity was correlated to the surface morphology and crystalline quality, governed by the growth conditions. It is believed that the compositional instability in InGaN originates from the coupled effects of compressive strain and surface morphology. A smooth surface allows for the growth of pseudomorphic low-indium InGaN, whereas a rough surface promotes the formation of a relaxed high-indium InGaN layer. [ABSTRACT FROM AUTHOR]

We studied 10 MeV electron irradiation effects in a group of n-GaN films grown by standard metalorganic chemical vapor deposition (MOCVD) and by epitaxial lateral overgrowth (ELOG) techniques. The samples were either undoped or Si-doped, so that the shallow donor concentrations ranged from 1014 cm-3 to 3 × 1018 cm-3. It was found that electron irradiation led to the compensation of n-type conductivity and that the carrier removal rate substantially increased with an increase in the starting donor concentration. For the MOCVD samples, it was observed that the main compensating defect introduced by electrons was a 0.15 eV electron trap detected by admittance spectroscopy. Once the Fermi level crossed the level of these traps two other centers with activation energies of 0.2 and 1 eV were found to contribute to the compensation, so that after high doses, the Fermi level in moderately doped samples was pinned near Ec -1 eV. In ELOG samples the 0.15 eV electron traps were not detected. Instead only the 0.2 and 1 eV traps were introduced by irradiation. The carrier removal rate in the ELOG n-GaN was found to be measurably lower than for MOCVD samples with a similar doping level. The results are compared to previously published data and possible models of compensation are discussed. [ABSTRACT FROM AUTHOR]

We measure the time-resolved photoluminescence characteristics of a novel type of lithographically patterned quantum dot fabricated by electron beam lithography, wet chemical etching, and overgrowth of the barrier layers by metalorganic chemical vapor deposition.We find that the quantum dot (QD) photoluminescence exhibits a bi-exponential decay that we explain in terms of the fast capture of carriers by defect states followed by a slower radiative relaxation process. We also perform a systematic investigation of the rise time and decay time as a function of the QD density, size, and temperature. These measurements indicate that the carrier capture process in this type of QD is limited by carrier drift within the GaAs barrier material. [ABSTRACT FROM AUTHOR]

A monomeric trinickel(ii)-substituted phosphotungstate [H9P2W15O62Ni3]9− ion is stabilized by grafting three {Re(CO)3} organometallic groups on the surface for the first time. Magnetic measurements manifest that the resulting complex, Na(NH4)5[P2W15O56Ni3(H2O)3(μ3-OH)3(Re(CO)3)3]·18H2O (1), displays overall ferromagnetic interactions with the presence of ZFS for Ni2+ at low temperature. [ABSTRACT FROM AUTHOR]

A chemically stable cationic MOF encapsulating an in situ formed water-hydroxide supramolecular anionic chain is realized for high hydroxide (OH−) ion conductivity in the solid-state (Type A). High OH− ion conductivity and low activation energy of the MOF demonstrate the advantage of the in situ incorporation of OH− ions to achieve efficient OH− ion conduction in the solid-state. [ABSTRACT FROM AUTHOR]

We first reported an anionic metal–organic framework for electrode material for the electrochemical detection of Cu2+. The modified electrode shows an excellent selectivity, high stability and sensitivity, wide linear range and lower detection limit. This strategy for generating new electrode materials will be useful for preparing new sensors and reporters for biological systems. [ABSTRACT FROM AUTHOR]

Incorporating the in situ formed size-matching molecular building blocks (MBBs) into the open channels will remarkably improve the robustness and gas sorption performance of an evacuated metal–organic framework. As a result, such MBBs can transfer the open metal sites from the framework walls to the channel centers and separate the large channels into multiple smaller voids, leading to a molecular sieving effect and high-performance gas-separation of the modified material. [ABSTRACT FROM AUTHOR]

The arc plasma deposition (APD) method is first applied to prepare metal–organic framework (MOF) composites loading metal nanoparticles having a direct contact with the MOF. We demonstrate the detailed growth mechanism of metal particles on the MOFs and the applicability of the APD for various combinations of metals and MOFs. [ABSTRACT FROM AUTHOR]

Reactions of 4′-(4-nalkyloxyphenyl)-4,2′:6′,4′′-terpyridines (alkyl = hexyl or nonyl) with Co(NCS)2 lead to three structurally characterized chiral 3D assemblies which adopt rare neb topologies. For the nhexyl-functionalized ligands, both enantiomorphic lattices of the neb nets (crystallizing in the tetragonal space groups P41212 and P43212, respectively) are presented. [ABSTRACT FROM AUTHOR]

Luminescent metal–organic frameworks (MOFs) represent interesting materials for applications in detection and sensing, for example. While most of these MOFs are based on carboxylate, azole or pyridyl ligands, the dipyrromethene moiety, also referred to as dipyrrin, seems also rather appealing. Indeed, this bis-pyrrolic backbone can be readily functionalized and can act as a monoanionic chelate under basic conditions, allowing the preparation of a variety of coordination compounds. Some of its metal complexes as well as its boron difluoride derivatives, BODIPYs, feature good stability, high quantum yield and tuneable emission wavelength. Therefore, several approaches have been proposed for their incorporation in MOFs to afford materials with interesting photophysical properties: self-assembly of ligands bearing multiple dipyrromethene moieties with metal cations or of luminescent metal complexes bearing peripheral coordinating moieties, stepwise construction of heterometallic architectures using metal complexes or BODIPYs as metalloligands, post-synthetic functionalization of the pores or the faces of MOF crystals by BODIPY dyes. These synthetic strategies as well as the photophysical properties of the resulting materials are reviewed in this highlight article. [ABSTRACT FROM AUTHOR]

Understanding how small molecules interact with DNA is essential since it underlies a multitude of pathological conditions and therapeutic interventions. Many different intercalator compounds have been studied because of their activity as mutagens or drugs, but little is known regarding their interaction with nucleosomes, the protein-packaged form of DNA in cells. Here, using crystallographic methods and molecular dynamics simulations, we discovered that adducts formed by [(η6-THA)Ru(ethylenediamine)Cl][PF6] (THA=5,8,9,10-tetrahydroanthracene; RAED-THA-Cl[PF6]) in the nucleosome comprise a novel one-stranded intercalation and DNA distortion mode. Conversely, the THA group in fact remains solvent exposed and does not disrupt base stacking in RAED-THA adducts on B-form DNA. This newly observed DNA binding mode and topology dependence may actually be prevalent and should be considered when studying covalently binding intercalating compounds. [ABSTRACT FROM AUTHOR]

Functionalization of metal–organic frameworks (MOFs) with Cu(i) sites is extremely desirable for various applications including adsorption, catalysis, and sensing. The traditional method for the conversion of supported Cu(ii) to Cu(i) is high-temperature autoreduction (HTA), which produces Cu(i) with an unsatisfactory yield (ca. 50%) but requires quite harsh conditions (e.g. 700 °C, 12 h) that are unsuitable for MOFs. Here we report the rational design of an efficient, controllable strategy for the conversion of supported Cu(ii) to Cu(i) by using vapor-induced selective reduction (VISR), in which vapors of weak reducing agents (e.g. methanol) diffuse into the pores of MOFs and interact with Cu(ii) precursors. This strategy allows the fabrication of Cu(i) sites with a 100% yield without the formation of Cu(0) at much lower temperatures (e.g. 200 °C, 6 h) and subsequently preserves the structure of MOFs well. Due to the abundant Cu(i) sites and high porosity of MOF supports, the obtained materials exhibit excellent performance in adsorptive desulfurization with regard to capacity, selectivity, and recyclability. [ABSTRACT FROM AUTHOR]

The first Ni-catalyzed Suzuki-Miyaura coupling of amides for the synthesis of widely occurring biaryl compounds through N−C amide bond activation is reported. The reaction tolerates a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents on both coupling partners. The reaction constitutes the first example of the Ni-catalyzed generation of aryl electrophiles from bench-stable amides with potential applications for a broad range of organometallic reactions. [ABSTRACT FROM AUTHOR]

A nickel-catalyzed three-component reaction involving terminal alkynes, boronic acids, and alkyl halides is presented herein. Trisubstituted alkenes can be obtained in a highly regio- and stereocontrolled manner by the simultaneous addition of both aryl and alkyl groups across the triple bond in a radical-mediated process. The reaction, devoid of air- and moisture-sensitive organometallic reagents and catalysts, is operationally simple and offers a broad scope and functional-group tolerance. [ABSTRACT FROM AUTHOR]

We report the structural design and control of electronic states of a new series of ultrafine metal-organic right square prism-shaped nanowires. These nanowires have a very small inner diameter of about 2.0 Å, which is larger than hydrogen and similar to xenon atomic diameters. The electronic states of nanowires can be widely controlled by substitution of structural components. Moreover, the platinum homometallic nanowire shows a 100 times higher proton conductivity than a palladium/platinum heterometallic one depending on the electronic states. [ABSTRACT FROM AUTHOR]

Enzymes typically depend on either NAD(P)H or FADH2 as hydride source for reduction purposes. In contrast, organometallic catalysts most often rely on isopropanol or formate to generate the reactive hydride moiety. Here we show that incorporation of a Cp*Ir cofactor possessing a biotin moiety and 4,7-dihydroxy-1,10-phenanthroline into streptavidin yields an NAD(P)H-dependent artificial transfer hydrogenase (ATHase). This ATHase (0.1 mol%) catalyzes imine reduction with 1 mM NADPH (2 mol%), which can be concurrently regenerated by a glucose dehydrogenase (GDH) using only 1.2 equiv of glucose. A four-enzyme cascade consisting of the ATHase, the GDH, a monoamine oxidase, and a catalase leads to the production of enantiopure amines. [ABSTRACT FROM AUTHOR]

Eleven trace metal(loid)s were determined in the household dust samples from Chengdu and Tianjin, China, and related human exposure and health risk to metal(loid)s via indoor dust intake were evaluated. The trace metal(loid)s were found to be highly concentrated and polluted in the indoor environment of Chengdu and Tianjin, especially for Cu, Zn, Cd, Sb, and Pb, of which the enrichment factors exceeding 5. Metal(loid) levels in the indoor dust samples exhibited no statistical differences between the two cities, with the exception of Sb, which was detected higher in the Chengdu samples. Bioaccessibilities in stomach phase of each element were estimated, Cd, Pb, and Sr exhibited higher bioaccessibility, and Sb showed the lowest bioaccessibility in both Chengdu and Tianjin. Dust ingestion was the main metal(loid) exposure pathway for Chengdu and Tianjin inhabitants, followed by dermal contact, dust inhalation accounted for less than 1 % of the total daily metal(loid) intakes and thus could be negligible. Children suffered more risk when exposure to metal(loid)s via indoor dust intake due to their higher frequency of hand to mouth activities. Risk evaluation indicated that, for most Chengdu and Tianjin inhabitants, there is little non-cancer and carcinogen risk when exposure to indoor dust. However, there is a potential non-cancer and carcinogen risk for children and adults in Chengdu, in the case of highly exposed scenario based on the current study. [ABSTRACT FROM AUTHOR]

The flexibility and structure transition behaviour of ZIF-8 in a series of samples with different particle size has been studied using a combination of high-resolution N2 gas adsorption isotherms and, for the first time, a broad in situ PXRD and Rietveld analysis. During the stepped adsorption process, large particles showed a narrow adsorption/desorption pressure range with a shorter equilibrium time due to lower kinetic hindrance, deriving from higher amount of active sites. In situ PXRD showed that both the rotation of imidazole ring and a bend in the methyl group led to the gate opening of ZIF-8. [ABSTRACT FROM AUTHOR]

By inserting a ligand into a reported metal–organic framework (Co-MOF1), the reformed aggregation of triangle grids (Co-MOF1-tpt) shows enhanced stability. In addition, owing to its structural characteristic, the Co-MOF1-tpt also reveals a certain CO2 storage ability and CO2/CH4 adsorption selectivity as expected. [ABSTRACT FROM AUTHOR]

A pH sensor is fabricated via a reaction between an AlIII salt and 2-aminoterephthalic acid in DMF which leads to a MOF (Al-MIL-101-NH2) with free amino groups. The Al-MIL-101-NH2 samples show good luminescence and an intact structure in aqueous solutions with pH ranging from 4.0 to 7.7. Given its exceptional stability and pH-dependent fluorescence intensity, Al-MIL-101-NH2 has been applied to fluorescent pH sensing. Significantly, in the whole experimental pH range (4.0–7.7), the fluorescence intensity almost increases with increasing pH (R2 = 0.99688) which can be rationalized using a linear equation: I = 2.33 pH + 26.04. In addition, error analysis and cycling experiments have demonstrated the accuracy and utilizability of the sensor. In practical applications (PBS and lake water), Al-MIL-101-NH2 also manifests its analytical efficiency in pH sensing. And the samples can be easily isolated from an aqueous solution by incorporating Fe3O4 nanoparticles. Moreover, the possible sensing mechanism based on amino protonation is discussed in detail. This work is on of the few cases for integrated pH sensing systems in aqueous solution based on luminescent MOFs. [ABSTRACT FROM AUTHOR]

An amidine-functionalised metal–organic framework (MOF) was shown to be an effective chemosensor in the presence of gaseous and aqueous phase CO2 by virtue of a quenched fluorescence response. This work demonstrates how multifunctional MOFs with high selectivity for CO2 may be exploited to develop CO2 chemosensors. [ABSTRACT FROM AUTHOR]

The pores/channels of porous 3D metal-organic frameworks (MOFs) have been widely applied to incorporate gas, solvent, or organic molecules. On the contrary, the utilization of the interlamellar void of layered metal-organic complexes (MOCs) remains underappreciated, although it is more flexible and available to accommodate molecules with different sizes. In this work, diverse sulfonates have been intercalated purposely into an identical layered MOC, which constructed various novel intercalation compounds possessing fluorescent, white-light emitting, photochromic, homochiral, or nonlinear optical (NLO) properties. With the help of single-crystal X-ray diffraction, their structures and the mutual interactions between the MOC host and the sulfonate guests were characterized. The properties of the guest molecules were tuned and meanwhile some new performances were generated after confining them into the interlayer region. Such a hybrid approach provides an efficient strategy to design and prepare multifunctional materials. [ABSTRACT FROM AUTHOR]

We fabricated monolithic solid state modules based on organometal CH3NH3PbI3 and CH3NH3PbI3 − xCl x perovskites using poly-(3-hexylthiophene) and Spiro-OMeTAD as hole transport materials (HTMs). In particular, we developed innovative and scalable patterning procedures to minimize the series resistance at the integrated series-interconnections. By using these optimization steps, we reached a maximum conversion efficiency of 8.2% under AM1.5G at 1 Sun illumination conditions using the CH3NH3PbI3 − xCl x perovskite and the poly-(3-hexylthiophene) as HTM. Finally, we investigated the double-step deposition of CH3NH3PbI3 using the Spiro-OMeTAD, reaching a maximum conversion efficiency on active area (10.08 cm2) equal to 13.0% (9.1% on aperture area) under AM1.5G at 1 Sun illumination conditions. This remarkable result represents the highest PCE value reached for the perovskite solar modules. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In meso-superstructured perovskite solar cells, the scaffolding layer, composed of insulating metal oxide nanoparticles, plays an important role in the loading efficiency of the perovskite layer. This communication describes 1D mesoporous silica nanoparticles that were successfully used as scaffolds to enhance the electron extraction from the perovskite absorber layer to the working electrode. [ABSTRACT FROM AUTHOR]

Four transition metal coordination polymers with 5-(1H-tetrazol-5-yl)isophthalic acid ligand (H3TZI) were synthesized and structurally characterized. They are formulated as [Zn(TZI)]·(CH3)2NH2+·H2O (1), [Cd2(OH)(TZI)(H2O)2]·DMF·0.5H2O (2), [MnNa(TZI)]·2H2O (3), and [Mn3(TZI)2(12H2O)]·4H2O (4). Compound 1 displays a 3D (4,4)-connected framework with a Schläfli symbol of 426282. 2 exhibits 3D frameworks in which strip-shaped chains with Cd3(μ3-OH) triangles are linked by TZI ligands, presenting a rare (3,4,5,6)-connected 4-nodal net topology with the point symbol (43)(4462)(4664)(4768). 3 features 2D 2p–3d heterometallic layers in which 1D chains with mixed bridges linking alternating Mn(ii) ions and Na(i) ions are interlinked by TZI spacers. The layers are further stabilized and associated into 3D architectures through intra- and interchain hydrogen bonds and/or π–π stacking. 4 consists of 1D double chains, and the 1D chains are assembled through hydrogen bonds to give a 3D supramolecular architecture. Intriguingly, Mn(ii) ions from different double chains are linked through hydrogen bonding bridges to give unprecedented hydrogen bonded chains with alternating single O–H…O bridges and double (O–H…O)2 bridges. Compounds 1 and 2 display intense photoluminescence properties in the solid state at room temperature, while 4 exhibits an antiferromagnetic interaction between Mn(ii) ions. [ABSTRACT FROM AUTHOR]

Studying the room temperature broadband ultrafast transient response of photoexcitations in three perovskite films, namely MAPbI3, MAPbI1.1Br1.9, and MAPbI3− xCl x (MA = CH3NH3), allowed unravelling the branching ratio between photogenerated carriers and excitons, a key factor for optoelectronic applications of perovskites. An instantaneously generated mid-IR photoinduced absorption (PA) band, PA1 is observed in all three perovskites, as well as a strong derivative-like band of photoinduced bleaching (PB) and PA (PA2) close to the corresponding absorption band edge. From the distinguished different decay dynamics of the PA bands in MAPbI3, PA1 is interpreted as due to the exciton transition, whereas PA2 and PB are due to band-filling effect caused by the photocarriers. In contrast, all bands in MAPbI1.1Br1.9 and MAPbI3− xCl x share the same dynamics and are therefore due to the same species, namely photogenerated excitons. The transient photoinduced polarization memory (POM) for both excitons and photocarriers as well as the steady-state photoluminescence (PL) emission are observed in MAPbI3, but not in MAPbI1.1Br1.9 and MAPbI3− xCl x because they possess cubic symmetry at room temperature. The estimated long excitons diffusion length (≈150 nm) in MAPbI3 opens up the possibility of photocarriers generation at interfaces and grain boundaries even when the exciton binding energy is large compare to kB T. [ABSTRACT FROM AUTHOR]

Two three-dimensional (3-D) MOFs, [(C 2 H 5 ) 4 N)] 3 [H 3 O] 2 [Cd 6 Br(H 2 -DHBDC) 8 (DMF) 4 ] ( 1 ; H 4 -DHBDC=2,5-dihydroxy-1,4-benzenedicarboxylic acid, DMF=N,N-dimethylformamide) and [(CH 3 ) 2 NH 2 ] 2 [Cd 3 (H2-DHBDC) 4 (DMF) 2 ]·2DMF( 2 ), are prepared from the self-assembly reactions between Cd(CH 3 COO) 2 and H 4 -DHBDC, respectively. Both anionic frameworks consist of linear trinuclear Cd units (e.g., 1 : [Cd 3 BrO 2 (CO 2 ) 7 ] and [Cd 3 O 2 (CO 2 ) 8 ]; 2 : [Cd 3 O 2 (CO 2 ) 8 ]) linked by the H 2 -DHBDC ligands. The photoluminescent properties of compound 1 are tunable through cation-exchange with different metal ions. The results demonstrated an effective ion-exchange approach toward the functional modification of MOF materials. [ABSTRACT FROM AUTHOR]

Reactions of group 4 metallocene sources with 2-substituted pyridines were investigated to evaluate their coordination type between innocent and reductive dearomatisation as well as to probe the possibility for couplings. A dependence on the cyclopentadienyl ligands (Cp, Cp*), the metals (Ti, Zr), and the substrates (2-phenyl-, 2-acetyl-, and 2-iminopyridine) was observed. While 2-phenylpyridine is barely reactive, 2-acetylpyridine reacts vigorously with the Cp-substituted complexes and selectively with their Cp* analogues. With 2-iminopyridine, in all cases selective reactions were observed. In the isolated [Cp2Ti], [Cp2Zr], and [Cp*2Zr] compounds the substrate coordinates by its pyridyl ring and the unsaturated side-chain. Subsequently, the pyridine was dearomatised, which is most pronounced in the [Cp*2Zr] compounds. Using [Cp*2Ti] leads to the unexpected paramagnetic complexes [Cp*2TiIII( N,O-acpy)] and [Cp*2TiIII( N, N′-impy)]. This highlights the non-innocent character of the pyridyl substrates. [ABSTRACT FROM AUTHOR]

Density functional theory in combination with the nonequilibrium Green's function formalism is used to study the electronic transport properties of methylammonium lead-iodide perovskite CH3NH3PbI3. Electronic transport in homogeneous ferroelectric and antiferroelectric phases, both of which do not contain any charged domain walls, is quite similar. The presence of charged domain wall drastically (by about an order of magnitude) enhances the electronic transport in the lateral direction. The increase of the transmission originates from the smaller variation of the electrostatic potential profile along the charged domain walls. This fact may provide a tool for tuning transport properties of such hybrid materials by manipulating molecular cations having dipole moment. [ABSTRACT FROM AUTHOR]

The authors developed a seed-mediated method by GeO2 nano-particles (NPs) for growing crystal perovskite films. Poly(3,4-ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)-GeO2 composite films can act as an efficient underlayer for the growth of crystal perovskite films. GeO2 NPs are regarded as the growing sites of crystal nucleus of the perovskites. Superior quality of perovskite films are achieved by tuning the size of the GeO2 NPs, which results in a power conversion efficiency as high as 16.77%. The seed-mediated growing route on perovskite crystallization also gives a hint to seek other nano-particle materials for fabricating highly efficient and stable perovskite solar cells in the future. [ABSTRACT FROM AUTHOR]

Organometal trihalide perovskites have recently emerged as promising materials for low-cost, high-efficiency solar cells. In less than five years, the efficiency of perovskite solar cells (PSC) has been updated rapidly as a result of new strategies adopted in their fabrication process, including device structure, interfacial engineering, chemical compositional tuning, and crystallization kinetics control. To date, the best PSC efficiency has reached 20.1%, which is close to that of single crystal silicon solar cells. However, the stability of PSC devices is still unsatisfactory and is the main bottleneck impeding their commercialization. Here, we summarize recent studies on the degradation mechanisms of organometal trihalide perovskites in PSC devices, and the strategies for stability improvement. [ABSTRACT FROM AUTHOR]

Atomic/molecular layer deposition offers us an elegant way of fabricating crystalline copper(ii)terephthalate metal–organic framework (MOF) thin films on various substrate surfaces. The films are grown from two gaseous precursors with a digital atomic/molecular level control for the film thickness under relatively mild conditions in a simple and fast one-step process. [ABSTRACT FROM AUTHOR]

An efficient sequential 1,2-addition/cross-coupling of Weinreb amides with two organolithium reagents is reported. This synthetic approach allows access to a wide variety of functionalized ketones in a modular way. The one-pot procedure presented here takes advantage of a kinetically stable tetrahedral Weinreb intermediate during subsequent Pd-catalyzed cross-coupling with the second organolithium reagent leading, within short reaction times and under mild conditions, to the formation of ketones in excellent overall yields. [ABSTRACT FROM AUTHOR]

A novel zinc(ii) metal–organic framework UTSA-67a with narrow one-dimensional (1D) pore channels and inner cages of moderate size has been developed for highly selective separation of C2H2/C2H4 mixtures at room temperature. [ABSTRACT FROM AUTHOR]

A facile synthetic strategy is developed to prepare mono-dispersed SnO2 particles within three-dimensional porous carbon frameworks by utilizing the adsorption properties of metal–organic frameworks. This composite exhibits a high reversible capacity of 900 mA h g−1 at 100 mA g−1 after 50 cycles, with a stable capacity retention of 880 mA h g−1 at 100 mA g−1 even after 200 cycles. [ABSTRACT FROM AUTHOR]

A homochiral MOF film grown on a functionalized substrate in a capillary column with high orientation and homogeneity was successfully prepared by using a layer-by-layer liquid phase epitaxial method; by introducing self-polymerized 3,4-dihydroxy-l-phenylalanine (poly(l-DOPA)) as a chiral substrate, the obtained enantiopure substrate mounted homochiral MOF thin film showed improved enantiomer separation. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs), composed of organic ligands and metal nodes, are well known for their high and permanent porosity, crystalline nature and versatile potential applications, which promoted them to be one of the most rapidly developing research focuses in chemical and materials science. During the various applications of MOFs, the photoluminescence properties of MOFs have received growing attention, especially for nitroaromatics (NACs) sensing, due to the consideration of homeland security, environmental cleaning and military issues. In this highlight, we summarize the progress in recent research in NACs sensing based on LMOFs cataloged by sensing techniques in the past three years, and then we describe the sensing applications for nano-MOF type materials and MOF film, together with MOF film applications. [ABSTRACT FROM AUTHOR]

The example of alkylation of commercial zinc and cadmium powders with organic halides in the presence of binary systems comprising an organometallic and a transition metal compounds was used to show that the nature of the transition metal compound in the binary system strongly affects the rate of a steady-state process. Therewith, the significant factors are both the nature of the transition metal and the ligand composition. It was found that the activity of the binary systems correlates with the activity of the transition metal compound in the transmetalation reaction with the organometallic component of the binary system (reduction of the transition metal compound). [ABSTRACT FROM AUTHOR]

The crystal structure of a new natural compound NaCu2Cl3[N3C2H2]2[NH3]2·4H2O, (further denoted I in the text) from a guano deposit located on the Pabellón de Pica Mountain, Iquique Province, Tarapacá Region, Chile, was studied by single-crystal low-temperature (200 K) XRD, R = 2.42 %. The compound I is orthorhombic, space group P212121; a = 19.484(3), b = 7.2136(10), c = 11.999(4) Å, V = 1686.5(7) Å3, Z = 4. The crystal structure of I contains zig-zag chains of the corner-sharing Cu(1)-centered octahedra running along the a axis and isolated Cu(2)- centered octahedra connected with the chains via 1,2,4-triazolate anions. This structural fragment is close to that found in the mineral chanabayaite, Cu2(N3C2H2)2Cl(NH3, Cl, H2O, ⌀)4. In contrast to Na-free chanabayaite, in the structure of I Na cations occupy Na(H2O)6 octahedra connected via common edges to form chains parallel to the chains of Cu(1)-centered octahedra. I is the second natural compound, after chanabayaite, with 1,2,4-triazolate anions N3C2H2 - and is assumed to be a protophase of chanabayaite; the latter was presumably formed as a result of Na and Cl leaching and dehydration of I. [ABSTRACT FROM AUTHOR]