OsRH52A, a DEAD-Box protein, is required for embryo sac development by regulating functional megaspore specification in rice.

The development of the embryo sac is an important factor affecting seed setting in rice. Numerous genes associated with embryo sac (ES) development have been identified in plants. However, the function of the DEAD-box RNA helicase family genes on ES is poorly known in rice. Here, we characterized a rice DEAD-box protein, OsRH52A, which was localized in the nucleus and cytoplasm and highly expressed in the floral organs in rice. The knockout mutant, rh52a, displayed partial ES sterility, including degenerated ES (21.0%) and the presence of double-female-gametophyte (DFG) structure (11.8%). The DFG developed from two functional megaspores (FM) near the chalazal end in one ovule, and 3.4% of DFG could fertilize via the sac near the micropylar pole in rh52a. OsRH52A was found to interact with OsMFS1 and ZIP4, both of which play a role in homologous recombination in rice meiosis. RNA-seq identified 234 down-regulated differentially expressed genes (DEGs) associated with reproductive development, including the two genes, OsMSP1 and HSA1b, required for female germline cell specification. Taken together, our study demonstrated that OsRH52A is essential for the development of the embryo sac and provided cytological evidence regarding the formation of DFG.

The heterointerface effect to boost the catalytic performance of single atom catalysts for sulfur conversion in lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are considered as one of the promising next-generation energy storage devices due to their characteristics of high energy density and low cost. However, the shuttle effect and sluggish conversion of lithium polysulfide (LiPs) have hindered their commercial applications. To address these issues, in our previous works, we have screened several highly efficient single atom catalysts (SACs) (MN4@G, M = V, Mo and W) with atomically dispersed transition metal atoms supported by nitrogen doped graphene based on high throughput calculations. Nevertheless, they still suffer from low loading of metal centers and unsatisfactory capability for accelerating the reaction kinetics. To tackle such problems, based on first-principles calculations, we systematically investigated the heterointerface effect on the catalytic performance of such three MN4@G toward sulfur conversion upon forming heterostructures with 5 typical two-dimensional materials of TiS2, C3N4, BN, graphene and reduced graphene oxide. Guided by efficient descriptors proposed in our previous work, we screened VN4@G/TiS2, MoN4@G/TiS2 and WN4@G/TiS2 possessing low Li2S decomposition barriers of 0.54, 0.44 and 0.41 eV, respectively. They also possess enhanced capabilities for catalyzing the sulfur reduction reaction as well as stabilizing soluble LiPs. More interestingly, the heterointerface can enhance the capability of the carbon atoms far away from the metal centers for trapping LiPs. This work shows that introducing a heterointerface is a promising strategy to boost the performance of SACs in Li-S batteries.

Metallic C5N monolayer as an efficient catalyst for accelerating redox kinetics of sulfur in lithium-sulfur batteries.

Lithium-sulfur battery is one of the most promising applicants for the next generation of energy storage devices whose commercial applications are impeded by the key issue of the shuttle effect. To overcome this obstacle, various two-dimensional (2D) carbon-based metal-free compounds have been proposed to serve as anchoring materials for immobilizing soluble lithium polysulfides (LiPs), which however suffer from low electronic conductivity implying unsatisfactory performance for catalyzing sulfur redox. Therefore, we have predicted metallic C5N monolayers, possessing hexagonal (H) and orthorhombic (O) phases, exhibiting excellent performance for suppressing the shuttle effect. First-principles simulations demonstrate that O-C5N could serve as a bifunctional anchoring material due to its strong adsorption capability to LiPs and excellent catalytic performance for sulfur redox with active sites from both basal plane and zigzag edges. Furthermore, the rate of Li2S oxidation over O-C5N is fast due to the low energy barrier of 0.93 eV for Li2S decomposition. While for H-C5N, only N atoms located at the armchair edges can efficiently trap LiPs and boost the formation and dissociation of Li2S during discharge and charge processes, respectively. The current work opens an avenue of designing 2D metallic carbon-based anchoring materials for lithium-sulfur batteries, which deserves further experimental research efforts.

Solvent-mediated crystal-to-crystal interconversion between discrete lanthanide complexes and one-dimensional coordination polymers and selective sensing for small molecules.

Two isostructural 1D coordination polymers {[Ln(OAc)2(H2O)(OBPT)]·3H2O}n (HOBPT = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol, Ln = Eu(3+), 1; Tb(3+), 3) and two discrete complexes [Ln(OAc)2(DMF)2(OBPT)] (Ln = Eu(3+), 2; Tb(3+), 4) have been synthesized in H2O-MeOH or DMF solvents, respectively. Their structures were identified by powder X-ray diffraction. Single-crystal X-ray studies for complexes 1 and 2 revealed that the coordination geometries of the Eu(3+) ions are similar and can be described as a distorted tricapped trigonal prism with six oxygen atoms and three nitrogen atoms. The difference between them is that one aqua ligand and one oxygen atom from the OBPT ligand complete the coordination sphere in complex 1, whereas two DMF molecules complete the coordination sphere in complex 2. Interestingly, the solvent-mediated, reversible crystal-to-crystal transformation between them was achieved by immersing the crystalline samples in the corresponding solvent (H2O or DMF) or by exposing them to solvent vapor. Complex 1 shows a highly selective luminescence enhancement in response to DMF in comparison to that observed in response to other examined solvents such as acetone, ethyl acetate, ethanol, acetonitrile, methanol, and THF.

SrTiO3@NiFe LDH core-shell composites for photocatalytic CO2 conversion.

A series of core@shell SrTiO3@NiFe LDH composites (STONFs) were synthesized and their photocatalytic CO2 reduction performance was studied. The photocatalyst STONF 2 exhibited enhanced CO2 reduction performance with CO yield of 7.9 µmol g-1 h-1. The yield was 25.7 times and 8.8 times higher than that of NiFe LDH and SrTiO3 respectively, and also higher than most LDH based photocatalysts. Compared with two individual components, STONFs exhibited their combined merits of widened absorption spectrum, higher transportation efficiency and alleviated recombination of e-/h+ pairs. In addition, there were fewer oxygen vacancies in STONF 2 than as-prepared SrTiO3. Lower oxygen vacancies concentration would increase the opportunity of direct bonding between interface atoms of two components and successively increase the electron transportation and separation. These factors synergistically contributed to enhanced photocatalytic performance. This work will provide new insight for designing complementary multi-component photocatalysis systems.

Simultaneously Enhancing Catalytic Performance and Increasing Density of Bifunctional CuN3 Active Sites in Dopant-Free 2D C3N3Cu for Oxygen Reduction/Evolution Reactions.

Atomically dispersed M-N-C has been considered an effective catalyst for various electrochemical reactions such as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which faces the challenge of increasing metal load while simultaneously maintaining catalytic performance. Herein, we put forward a strategy for boosting catalytic performances of a single Cu atom coordinated with three N atoms (CuN3) for both ORR and OER by increasing the density of connected CuN3 moieties. Our calculations first show that a single CuN3 moiety exhibiting no catalytic performance for ORR and OER can be activated by increasing the density of metal centers, which weakens the binding affinity to *OH due to the lowered d-band center of the metal atoms. These findings stimulate the further theoretical design of a two-dimensional compound of C3N3Cu with a high concentration of homogeneously distributed CuN3 moieties serving as bifunctional active sites, which demonstrates efficient catalytic performance for both ORR and OER as reflected by the overpotentials of 0.71 and 0.43 V, respectively. This work opens a new avenue for designing effective single-atom catalysts with potential applications as energy storage and conversion devices possessing high density of metal centers independent of the doping strategy and defect engineering, which deserves experimental investigation in the future.

Chemical synthesis, structural characterization, optical properties, and photocatalytic activity of ultrathin ZnSe nanorods.

Ultrathin ZnSe nanorods in the cubic phase have been synthesized by the reaction of selenium and zinc oleate for 30 min at 240 °C. These nanorods showed an average diameter of 2.4 nm, which is much smaller than the Bohr size of bulk ZnSe. Thus, they exhibited a remarkable quantum size effect in terms of their optical properties. The formation of the ultrathin nanorods could be attributed to the oriented attachment mechanism, which was supported by the structure of the nanorods and the control experiments. The ultrathin nanorods were transferred into an aqueous solution by ligand exchange. The performance of these nanorods as a catalyst was examined, using the photodegradation of methyl orange as a model reaction. It was found that the ultrathin nanorods possessed better photocatalytic activities than conventional ones.

CdSe/ZIF-8-x: synthesis and photocatalytic CO2 reduction performance.

The photocatalytic reduction of CO2 is an effective way to solve the greenhouse effect. Different kinds of materials, such as semiconductors, coordination compounds, and bioenzymes, have been widely investigated to increase the efficiency of the photocatalytic reduction of CO2. However, a high selectivity and great stability are still challenges for material scientists. Here, we report for the first time visible light photocatalytic CO2 reduction by a series of CdSe/ZIF-8 nanocomposites combining the excellent CO2 adsorption capacity of ZIF-8 and the narrow energy gap of CdSe quantum dots (QDs). The composites show a higher catalytic performance than those of the pure components. Among CdSe/ZIF-8-x (x = n CdSe/n ZIF-8), the highest yield (42.317 µmol g-1) for reducing CO2 to CO in 12 h, was obtained using nanocomposites with a ratio of 0.42 (n CdSe/n ZIF-8) within the range of investigation.

Synthesis, characterization, photophysics, and anion binding properties of platinum(ii) acetylide complexes with urea group.

A new class of platinum(ii) acetylide complexes with urea group, [Pt((t)Bu3tpy)(C[triple bond, length as m-dash]CC6H4-4-NHC(O)NHC6H4-4-R)](OTf) ((t)Bu3tpy = 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine; R = H (), Cl (), CF3 (), and NO2 ()), has been synthesized and characterized. The crystal structures of , ·DMF·THF, ·CH3CN, and ·CH3CN have been determined by X-ray diffraction. Upon excitation at λ > 380 nm, the solid samples of complexes show orange light at 298 K. The anion binding properties of complexes have been studied by UV-vis titration experiments in CH3CN and DMSO. In general, the log K values of with the same anion in CH3CN depend on the substituent R on the acetylide ligand of and follow this order: R = NO2 () > CF3 () > Cl () > H (). For the same complex with different anions, the log K values are in the following order: F(-) > OAc(-) > Cl(-) > Br(-) ≈ HSO4(-) ≈ NO3(-) > I(-), which is in accordance with the decrease in the basicity of anions. Complex with NO2 group shows a dramatic colour change towards F(-) in DMSO, allowing the naked eye detection of F(-).

Interaction between biimidazole complexes of ruthenium and acetate: hydrogen bonding and proton transfer.

The hydrogen bonding and deprotonation processes between four ruthenium biimidazole complexes, namely [Ru(bpy)(2)(BiimH(2))](PF(6))(2) (1, bpy is bipyridine, BiimH(2) is 2,2'-biimidazole), [Ru(bpy)(2)-(BbimH(2))](PF(6))(2) (2, BbimH(2) is 2,2'-bibenzimidazole), and [Ru(bpy)(2)(DMBbimH(2))](PF(6))(2) (3, DMBbimH(2) is 7,7'-dimethyl-2,2'-bibenzimidazole) and [Ru(bpy)(2)(TMBbimH(2))](2+) (4, TMBbimH(2) is 5,6,5',6'-tetramethyl-2,2'-bibenzimidazole), and acetate are investigated. Their hydrogen bonded adducts are indeed trapped and observed by absorption spectra and electrochemical experiments in acetonitrile solution in the presence of an excess of acetic acid for the first time. The binding constants log K(B) for these adducts are 6.74 for 1·OAc, 7.11 for 2·OAc, 7.26 for 3·OAc, and 6.99 for 4·OAc. A new approach to calculate the deprotonation constant is also developed by establishing a set of circular equilibria. The equilibrium constants for the first deprotonation step of the complexes log K(A) are 2.74 for 1, 5.19 for 2, 4.54 for 3, and 3.78 for 4. The pK(a1) values of the complexes in acetonitrile solution are calculated by subtracting log K(A) from pK(a) (HOAc in acetonitrile), giving 19.6 for 1, 17.1 for 2, 17.8 for 3, and 18.5 for 4. The degree of proton transfer (D(PT)) can be quantified by the calculation of absorption spectral and redox data, which is 0.41 for 1·OAc, 0.53 for 2·OAc, 0.57 for 3·OAc, and 0.47 for 4·OAc. Interestingly, the binding constant log K(B) (7.26) and D(PT) value (0.57) both reach their maxima at a critical point, where pK(a1) for the complex is 17.8 and ΔpK(a) for the adduct is 4.5 (ΔpK(a) = pK(a)(HOAc) - pK(a1), in acetonitrile solution). Moreover, the binding constant log K(B) shows linear correlation with the degree of proton transfer D(PT).

Photophysical, electrochemical and anion sensing properties of Ru(II) bipyridine complexes with 2,2'-biimidazole-like ligand.

A new anion sensor [Ru(bpy)(2)(DMBbimH(2))](PF(6))(2) (3) (bpy is 2, 2'-bipyridine and DMBbimH(2) is 7,7'-dimethyl-2,2'-bibenzimidazole) has been developed. Its photophysical, electrochemical and anion sensing properties are compared with two previously investigated systems, [Ru(bpy)(2)(BiimH(2))](PF(6))(2) (1) and [Ru(bpy)(2)(BbimH(2))](PF(6))(2) (2) (BiimH(2) is 2,2'-biimidazole and BbimH(2) is 2,2'-bibenzimidazole). The high acidity of the N-H fragments in these complexes make them easy to be deprotonated by strong basic anions such as F(-) and OAc(-), and they form N-H···X hydrogen bonds with weak basic anions like Cl(-), Br(-), I(-), NO(3)(-), and HSO(4)(-). Complex 3 displays strong hydrogen bonding with these 5 weak basic anions, with binding constants between 17,000 and 21,000, which are larger than those observed in complex 1, with binding constants between 3300 and 5700, and in complex 2, which shows no hydrogen bonding toward Cl(-), Br(-), I(-), and NO(3)(-), and forms considerable hydrogen bonds with HSO(4)(-) with a binding constant of 11,209. These hydrogen bonding behaviours give different NMR, emission and electrochemical responses. The different anion binding affinity of these complexes may be mainly attributed to their different pK(a1) values, 7.2 for 1, 5.7 for 2, and 6.2 for 3. The additional methyl groups at the 7 and 7' positions of complex 3 may also play an important role in the enhancement of anion binding strength.

Preparation and Characterization of Metal Sulfides in Ethylenediamine under Ambient Conditions through a gamma-Irradiation Route.

The gamma-irradiation technique has been extended to irradiate liquid ethylenediamine containing metal ions and sulfur powder, and a series of uniform metal sulfide particles including CdS, PbS, Cu(2)S, and Ag(2)S have been prepared at room temperature. X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-visible spectra have been used to characterize the products. In addition, the discussion shows that ethylenediamine and solvated electrons formed in ethylenediamine play crucial roles during the synthetic process. The stability constants of the metal chelates with ethylenediamine, the solubility product constants of the metal sulfides, and the standard electrode potentials of the metal ions also directly control the formation of metal sulfides. Copyright 2001 Academic Press.