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Tautomeric isomerism is very important in DNA/RNA research, especially base-pair mismatches. However, the tautomeric polymorph of anhydrous guanine (AG) composed of a N7-G purine ring has never been reported in the literature. Herein, a novel crystal phase of anhydrous guanine consisting of a N9-G purine ring was obtained by dehydration of guanine monohydrate (GM) at 111 °C, termed dehydrated-GM, the first reported tautomeric polymorph of AG (N7-G). The dehydration/hydration transformation between GM and dehydrated-GM can be repeated more than 10 times without any observable phase damage. The dehydrated-GM can harvest 8 wt % water within 30 min at relative low humidity (below 20%). Furthermore, dehydrated-GM has long-term stability in a very dry environment when the temperature is in between RT and 150 °C. The channel structure of dehydrated-GM can enlighten the design of materials to harvest water from atmospheric air. The tautomeric polymorphism of N7-G and N9-G purine rings provides a new insight in nu...

The reaction of the bis(dichlorogold) complex of 2,3-bis(diphenylphosphino)maleic anhydride (L1) with S(SiMe3)2 in the presence of NaBPh4 yields the ionic dodecanuclear cluster compound [Au12(PPh2)2S4(L2)4](BPh4)2 (1). During the formation of 1, the initial ligand L1 is transformed into the doubly sylilated derivative, 3,4-bis(diphenylphosphino)-2,5-bis(trimethylsilyloxy)-furan (L2). The presence of bridging PPh2 groups is a result of the transformation of L1 in the coordination sphere of Au(i). Compound 1 was characterized by single crystal X-ray diffraction and electrospray-ionization (ESI) mass spectrometry.

A new mixed-metal polyborate, Na5Li[B12O18(OH)6]·2H2O (1), has been synthesized using solvothermal method and characterized by IR spectroscopy, thermogravimetric analysis, UV–Vis spectroscopy, powder and single-crystal X-ray diffraction, respectively. It crystallizes in the trigonal space group R-3c (No. 167) with unit cell parameters of a = b = 9.6767(6) A, c = 36.358(5) A, and Z = 6. Its structure features unprecedented 3D framework constructed from novel honeycomb-shaped inorganic Na-O sheets with unique 12-MR sodium rings and supramolecular polyborate 2D layers of lithium-centered [B12O18(OH)6]6-. UV–Vis spectral characterization indicates that compound 1 is a wide-band-gap semiconductor.

Catalytic reactions that require more than one active sites are popular, such as selective catalytic reduction of NOx with NH3 (NH3-SCR) for the elimination of NOx contaminant containing redox and acid dinuclear sites. Doping/supporting other elements is a general strategy for introduction of the one that catalysts lack. Herein, we prepared a highly defective α-Fe2O3 with enhanced acid (Lewis and Bronsted) and redox properties on homoatomic dinuclear sites comprising more positively charged Fe3+ and oxygen vacancy-coupled Fe2+ ions. The NH3-SCR activity is improved at lower temperature without adding another acid transition metal. Furthermore, the significant amounts of Bronsted acid provide precaution against the poisoning of H2O and SO2. This work greatly broadened applicability of the state of the art concept of dinuclear sites for NH3-SCR and open a new avenue to enhance activity via defective engineering for a single metal oxide.

A new layered silicogermanate, PKU-22, was hydrothermally synthesized under fluoride conditions using the tetraethylammonium (TEA+) cation as the structure directing agent (SDA). The crystal structure was determined by single crystal X-ray diffraction. Structure analysis reveals that PKU-22 is constructed by sti layers stacking along the [100] direction in an ···AAAA··· manner, with TEA+ cations occurring in the interlayer spaces and F– anions residing within the layer and connecting to Ge atoms, which also act as the charge compensation species. In situ temperature-variable powder X-ray diffraction results indicated that PKU-22 could be transferred into a three-dimensional STI-type zeolite PKU-22a on heating. It is interesting that the TEA+ cations remain intact in the structure of the condensed product. Solid-state NMR, inductively coupled plasma atomic emission spectroscopy, thermogravimetric-differential scanning calorimetry, and carbon, hydrogen, and nitrogen elemental analyses were applied to aid th...

The structural stability is crucially important for thermoelectric material from the point view of energy harvesting applications. Herein, p-type Zn-Sb semiconductor doped with magnesium (Mg 0.04 Zn 3.96 Sb 3 ) was experimentally investigated after thermal cycles to verify its structure stability, via a combination of synchrotron-based X-ray absorption spectroscopy (XAFS), grazing-incidence X-ray diffraction (GI-XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). While no visible structure change was discovered from XRD measurement after annealed to 573 K in air, well-preserved atomic structure of Mg-doped Zn-Sb was also demonstrated by XAFS. Interestingly, SEM indicated significantly improved surface morphology whilst EDS clearly showed the relative steadiness of each element's spatial distribution on surface. On basis of these findings, it was concluded in the end that the doping of magnesium substantially improves the thermal stability of zinc-antimonite compounds, and the possible mechanism underneath was also demonstrated.

// Jing Yang 1, 2 , Qiaoling Zhu 2 , Qiao Liu 2 , Yingxia Wang 2 , Weimin Xie 1 and Lili Hu 3 1 Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China 2 Department of Obstetrics and Gynecology, Maternal and Child Health Care Hospital of Hunan Province, Changsha, China 3 Department of Obstetrics and Gynecology, Jilin Central Hospital, Jilin, China Correspondence to: Weimin Xie, email: xwm315423@163.com Keywords: statin, endometrial cancer, cancer risk, meta-analysis Received: March 17, 2017 Accepted: May 04, 2017 Published: June 27, 2017 ABSTRACT Several studies have evaluated the association between statin use and endometrial cancer risk. We carried out a meta-analysis of randomized controlled trials (RCTs) and non-randomized studies to evaluate the effect of statins on endometrial cancer risk. A comprehensive search of electronic databases, conference abstracts and clinical trial registers was conducted for published and unpublished results. Studies that evaluated exposure to statins and endometrial cancer risk were considered. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using either a fixed-effects or a random-effects model. Two RCTs and eleven non-randomized studies (four cohort and seven case-control studies) involving 9,517 cases of endometrial cancer were included in the analysis. There was no evidence of an association between statin use and endometrial cancer risk either among RCTs (RR, 0.72; 95% CI, 0.19 to 2.67) or among non-randomized studies (RR, 0.94; 95% CI, 0.82 to 1.07). Combined analysis of all included studies also showed that statin use did not significantly affect endometrial cancer risk (RR, 0.94; 95% CI, 0.82 to 1.07). The sensitivity analysis confirmed the stability of our results. Our findings do not support a protective effect of statins against endometrial cancer at the population level.

A new zinc borate [Zn(dap)2][B4O6(OH)2] (1, dap = 1,3-diaminopropane) has been hydrothermally synthesized and structurally characterized by IR, elemental analysis, thermogravimetric analysis, powder and single-crystal X-ray diffractions. It crystallized in the monoclinic P21/c space group, a = 7.0050(4) A, b = 7.8160(2) A, c = 18.4470(5) A, β = 94.571(3) A, V = 1006.78(7) A3, Z = 4, R 1 = 0.0342, wR 2 = 0.0835. Compound 1 displays a novel two-dimensional inorganic–organic hybrid zinc borate layer constructed from the assembly of [B4O6(OH)2]2− clusters, ZnO2N2 tetrahedra and organic dap molecules. The occurrence of infinite Zn–amine–Zn chains in the structure is uncommon and noteworthy in borate materials.

A robust iridium(iii)-porphyrin metal–organic framework acts as a selective catalyst for carbenoid insertion into primary Si–H bonds with excellent effectivity., An iridium-porphyrin ligand, Ir(TCPP)Cl (TCPP = tetrakis(4-carboxyphenyl)porphyrin), has been utilized to react with HfCl4 to generate a stable Ir(iii)-porphyrin metal–organic framework of the formula [(Hf6(μ3-O)8(OH)2(H2O)10)2(Ir(TCPP)Cl)3]·solvents (Ir-PMOF-1(Hf)), which possesses two types of open cavities (1.9 × 1.9 × 1.9 and 3.0 × 3.0 × 3.0 nm3) crosslinked through orthogonal channels (1.9 × 1.9 nm2) in three directions. The smaller cavity is surrounded by four catalytic Ir(TCPP)Cl walls to form a confined coordination space as a molecular nanoreactor, while the larger one facilitates reactant/product feeding and release. Therefore, the porous Ir-PMOF-1(Hf) can act as a multi-channel crystalline molecular flask to promote the carbenoid insertion reaction into Si–H bonds, featuring high chemoselectivity towards primary silanes among primary, secondary and tertiary silanes under heterogeneous conditions that are inaccessible by conventional homogeneous catalysts.

In this work, novel branched palladium–gold (PdAu) bimetallic nanowires supported on graphene (PdAu/graphene) were fabricated at relatively low temperatures for the first time by a one-pot co-reduction method with the aid of poly(diallyldimethyl-ammonium chloride). The structural characteristics of PdAu/graphene were confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, high-angle annular dark-field scanning transmission electron microscopy and element mapping observations. The electrochemical properties of the PdAu/graphene were characterised by cyclic voltammetry and chronoamperometry (CA) in the formic acid oxidation reaction. Compared with a commercial Pd/C catalyst, the PdAu/graphene catalyst prepared in this work exhibited enhanced electrocatalytic activity including a higher oxidation current density, enhanced CO tolerance, and a more negative onset potential. Moreover, CA analyses demonstrated that PdAu/graphene shows higher stability than the Pd/C catalyst. The PdAu/graphene catalyst exhibited higher activity and strong poisoning resistance, which could be attributed to its special branched structure from PdAu nanowires.

In this work, the effect of cold rolling and heat treatment upon the microstructure and texture of the surface layer and cross-section of Ni5W alloy substrate was analyzed via the EBSD technique. A typical copper deformation texture was shown by the cold-rolled Ni5W alloy substrate. The cube-oriented nuclei were attributed to the rolling direction&ndash, transverse direction (RD-TD) plane due to the presence of copper and S rolling textures. Typical large-shape cold-rolled microstructure was presented by the RD-ND surface in the cube-oriented area. During the recrystallization process, the cube-oriented grains did not have a nucleation quantity advantage, but they did have an obvious growth advantage compared with other orientation grains. They can form a strong cube texture by absorbing the random orientation and rolling orientation through the migration of large-angle grain boundaries.

Carrageenan fibers have attractive applications in textile, but their low strength remains a problem that needs to be urgently addressed. In this work, a novel facile, environmental friendly method for fabricate high-strength carrageenan fibers is proposed. It involves the crosslinking of a small amount of Ba

In this article, nano-NbC particles toughened Si₃N₄-based ceramics were prepared by injection moulding and their mechanical properties along with toughening mechanism were studied. An increase of nano-NbC content, gradually homogenizes microstructure of the Si₃N₄-based ceramics along with increase in its density. However, the fracture toughness and flexural strength first increases and then decreases. The Si₃N₄-based ceramics demonstrate good comprehensive properties at the 15 wt% nano-NbC content and sintering temperature of 1550 °C (where the density is 85.3%, the flexural strength is 845 MPa, and the fracture toughness is 9.3 MPa·m

A simple method was proposed for preparing the dialdehyde-β-cyclodextrin (DA-β-CD) cross-linked carboxymethyl chitosan (CMCS) hydrogels for drug delivery. DA-β-CD was yielded from the sodium periodate oxidation of β-CD. Phenolphthalein (PhP) was adopted as a model drug to study the drug loading and releasing properties of the obtained hydrogels. The results show that the ability of the hydrogel to load drug is affected by the aldehyde content of DA-β-CD. The inclusion constant of DA-β-CD toward PhP is lower than that of the original β-CD and decreased with the rising of the aldehyde content. An increased cross-linking degree between DA-β-CD and CMCS slows the PhP release to some extent. In comparison with glyoxal/CMCS, DA-β-CD/CMCS presents better PhP release properties. Only 19.2 % of PhP loaded in glyoxal/CMCS was released within 24 h. Half of PhP loaded in DA-β-CD/CMCS was released in 2 h and about 90 % was released within 12 h.

Intrinsic isotropic near-zero thermal expansion is discovered in borate crystal Zn4 B6 O13 with high transparency in the ultraviolet region. First-principles calculations demonstrate that the very low thermal expansion originates mainly from the invariability of the solid [B24 O48 ] truncated octahedra that are fixed by the [Zn4 O13 ] clusters in the ZBO structure.

A new silicogermanate (PKU-20) was hydrothermally synthesized using triethylisopropylammonium cation as the structure directing agent in the presence of fluoride. Its structure was determined from ...

Self-assembly of a new metalloporphyrin tetracarboxylic ligand Ir(TCPP)Cl (TCPP = tetrakis(4-carboxyphenyl)porphyrin) with ZrCl4 in the presence of benzoic acid leads to the formation of a three-dimensional (3D) iridium(III)-porphyrin metal–organic framework (Ir-PMOF) with the formula of [(Zr6(μ3-O)8(OH)2(H2O)10)2(Ir(TCPP)Cl)3]·solvents (Ir-PMOF-1(Zr)), which possesses square-shaped channels of 1.9 × 1.9 nm2 (atom-to-atom distances across opposite Ir metal atoms) in three orthogonal directions as disclosed by the single-crystal X-ray diffraction analysis. Ir-PMOF-1(Zr) represents the first MOF bearing a self-supporting iridium-porphyrin catalytic framework, featuring high porosity and stability. The catalytic tests disclose that the activated Ir-PMOF-1(Zr) can promote O–H insertion with a turnover frequency (TOF) up to 4260 h−1. Ir-PMOF-1(Zr) can be recycled and reused for 10 runs without significant loss of catalytic activity, and the total turnover number (TON) for O–H insertion after 10 successive runs reaches 875.

Carrageenan fibers have attractive applications in textile, but their low strength remains a problem that needs to be urgently addressed. In this work, a novel facile, environmental friendly method for fabricate high-strength carrageenan fibers is proposed. It involves the crosslinking of a small amount of Ba2+ ions in the carrageenan solution, followed by using recyclable alcohol in coagulation and stretching baths. Carrageenan molecular chains were allowed to first sufficiently interact with metal barium ions, and then were stretched and dehydrated with alcohol to increase the hydrogen bonding interaction between the molecular chains. As a result, the carrageenan fibers with high-strength ionic and hydrogen bonds were obtained. The fibers obtained by the novel method had high tensile strength at 1.63 cN/dtex, which is two times higher than that of those obtained by the traditional process.

The thermal stability and structural transformation mechanism are critical for the industrial applications of zeolites and the design of new framework types. Herein, a new zeolite PKU-26 has been hydrothermally synthesized under fluoride conditions using a tetraethylammonium (TEA+ ) cation as the structure-directing agent (SDA) and its framework contains partial Q3 T atoms [Q3 for T(-O-T)3 OH]. Upon calcination, PKU-26 processed a single-crystal to single-crystal transformation to another novel zeolite PKU-27 with the elimination of terminal -OH groups and enhanced thermal stability up to 650 °C, exhibiting the first Q3 →Q4 transformation [Q4 for T(-O-T)4 ] in 3D zeolite frameworks. The mechanism of the structural transformation, involving proton transfer, framework dehydration, and TO4 reconstruction, is proposed and supported by theoretical calculations.

Construction of spirocyclic pyrrolidines bearing a spiro quaternary stereocenter is an enormous challenge in synthetic organic chemistry. In this report, we introduce a Ag(I)/CAAA-amidphos-catalyzed enantioselective 1,3-dipolar cycloaddition between azomethine ylides and &alpha, methylene-&gamma, butyrolactone as an effective strategy for the construction of excellent endo-selective spiro-[butyrolactone-pyrrolidine] derivatives. Meanwhile, the catalytic system was also successfully applied in the three-component one-pot reaction of azomethine ylides formed in situ under the action of N,N&prime, diisopropylcarbodiimide serving as a dehydrator. Under the optimal conditions, endo-pyrrolidine derivatives bearing a spiro quaternary stereocenter were obtained with high to excellent yields (up to 95% yield) and enantioselectivities (up to 93% ee).

The reaction of the bis(dichlorogold) complex of 2,3-bis(diphenylphosphino)maleic anhydride (L1) with S(SiMe

g rap hical a bstract � A series of Na-rich antiperovskites were developed as advanced solid electrolytes. � The materials are nonflammable, low-cost and suitable for thermo- plastic processing. � Enhanced sodium ionic conductivity was achieved by structural manipu- lation approaches. � The Na ionic conductivity of Na2.9S- r0.05OBr0.6I0.4 reaches 1.9 � 10 � 3 S/cm at 200 � C. abstract High-performance solid electrolytes are critical for realizing all-solid-state batteries with enhanced safety and cycling efficiency. However, currently available candidates (sulfides and the NASICON-type ceramics) still suffer from drawbacks such as inflammability, high-cost and unfavorable machinability. Here we present the structural manipulation approaches to improve the sodium ionic conductivity in a series of affordable Na-rich antiperovskites. Experimentally, the whole solid solutions of Na3OX (X ¼ Cl, Br, I) are synthesized via a facile and timesaving route from the cheapest raw materials (Na, NaOH and NaX). The materials are nonflammable, suitable for thermoplastic processing due to low melting tem- peratures (

Hydrogarnets Sr3M2(OH)12 (M = Al, Cr and Fe) were synthesized through a solid state reaction at room temperature with Al(NO3)3·9H2O, CrCl3·6H2O, FeCl3·6H2O, Sr(NO3)2 and NaOH as the starting materials. All X-ray diffraction (XRD) data of Sr3M2(OH)12 were indexed by the cubic system with the space group of Ia−3d. XRD, differential thermal analysis and thermogravimetric (DTA–TG), and scanning electron microscopy (SEM) were employed to investigate the structural stability, thermal properties and morphologies of Sr based hydrogarnets. The cause of room temperature synthesis and the thermal decomposition behaviors of Sr-based hydrogarnets Sr3M2(OH)12 (M = Al, Cr and Fe) are discussed.

One of the challenges in materials science has been to prepare crystalline inorganic compounds with mesopores. Although several design strategies have been developed to address the challenge, expan ...

A novel inorganic–organic hybrid open-framework zinc phosphate, (NH4)[Zn5(PO4)3(HPO4)2(HAPIM)2]·(H2O) (1), was solvothermally synthesized in the presence of 1-(3-aminopropyl)imidazole (APIM) as structure-directing agent. Its structure is built up by the alternate linkages between ZnO4, ZnO3N, PO4 and HPO4 tetrahedral moieties, forming an unusual three-dimensional framework with intersecting 8-, 10-, and 16-ring channels. The arrangement of the monoprotonated APIM molecules in 1 is unique and they play dual roles as both ligands and countercations. It is the first example with APIM as template in extra-large-channel structures in zincophosphates. The framework contains a Zn/P ratio of 1:1 and exhibits remarkable low framework density. Photoluminescence studies show that there is a ligand-to-metal charge transfer.

A series of homochiral metal-organic cages (MOCs) have been obtained from self-assembly of Cu(II) salts with chiral N,N'-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-amino acids. Single-crystal X-ray diffraction analyses reveal that these compounds show a lantern-type cage structure, in which one pair of Cu2(CO2)4 paddlewheels is linked by four diacid ligands. The resulting homochiral cages have been fully characterized by EA, TOF-MS, TGA, VTPXRD, IR, UV, and CD measurements. The catalytic tests reveal that these Cu(II) cages are effective in cyclopropanation with excellent diastereoselectivity (up to 99 : 1 E/Z). In addition, the cage catalysts can promote the aziridination reaction with PhI=NNs.

Positron emission mammography (PEM) is an effective means for early diagnosis of breast cancer. In this work, we designed a double-plane detector for PEM based on silicon photomultiplier tubes (SiPM). Each detector was composed of $5 \times 6$ blocks with a total area of $168.6 \times 202.4$ mm$^{\mathbf {2}}$. Each block consisted of $\mathrm {a}16 \times 16$ LYSO array with the pixel size of $1.9 \times 1.9 \times 15$ mm$^{\mathbf {3}}$. An $8 \times 8$ SiPM array constructed with SensL's C30035 sensors was coupled to the LYSO with a 1.5mm thick glass. By using a splittype design, the active part of the front-end electronics was kept away from SiPMs to avoid the influence of temperature. Selfdesigned data acquisition system was also used. The test results shown that each pixel can be clearly distinguished. The block's average energy resolutions at 511keV and 140keV were 11.39% and 21.31% separately. The coincidence time resolution of 1.32ns and intrinsic spatial resolution of 1.87mm were also achieved using a $^{\mathbf {22}}$Na point source. The preliminary results indicated that this PET detector could also be used for SPECT application.

Immune recovery (IR) after haploidentical stem cell transplantation (haplo-SCT) in severe aplastic anemia (SAA) patients remains relatively unknown. In this study, we examined immune cell subset counts and immunoglobulins in 81 SAA patients from day 30 to day 365 after haplo-SCT. Simultaneously, we determined which factors influence IR and analyzed the effects of immune cell subsets on transplant outcomes. We found that: (i) The reconstitution of different immune cell subsets occurred at different rates after haplo-SCT. Monocytes were the first to recover, followed by CD8+ T and CD19+ B cells, and finally CD4+ T cells. (ii) In the multivariate analysis, lower recipient age, female gender, high mononuclear cell counts in the graft and absence of CMV reactivation were associated with improved IR after transplant. (iii) A CD4/CD8 ratio less than 0.567 on day 30 post transplantation was associated with higher overall survival after haplo-SCT in SAA patients. In conclusion, SAA patients showed a faster recovery of monocytes and CD8+ T cells after haplo-SCT, whereas the recovery of the CD4+ T-cell subset was delayed. Our results may provide insight into methods for better predicting and modulating IR of SAA patients and subsequently improving outcomes after transplantation.

The layered perovskite cobaltite $R{\mathrm{BaCo}}_{2}{\mathrm{O}}_{5.5}$ ($R$: rare-earth elements) exhibits an abrupt temperature-induced metal-insulator transition (MIT) that has been attributed to spin-state ordering (SSO) of ${\mathrm{Co}}^{3+}$ ions. Here we investigate the hole-doping member of ${\mathrm{PrBaCo}}_{2}{\mathrm{O}}_{5.5+x}$ ($0\ensuremath{\le}x\ensuremath{\le}0.24$) with multiple techniques. The analysis of crystal and magnetic structures by electron and neutron diffraction confirm the SSO in the insulating phase of undoped ${\mathrm{PrBaCo}}_{2}{\mathrm{O}}_{5.5}$, which is melted by increasing the temperature across the MIT. In addition, we discover that hole doping to ${\mathrm{PrBaCo}}_{2}{\mathrm{O}}_{5.5}$ also melts the SSO in conjunction with an insulator-metal transition. The experimental results from electron and neutron diffraction and soft-x-ray absorption spectroscopy (XAS) all lead to the conclusion that hole-doping-induced MIT occurs in the same manner as the temperature-induced MIT. Therefore, we propose a unified mechanism that dominates the temperature- and hole-doping-induced MIT in the ${\mathrm{PrBaCo}}_{2}{\mathrm{O}}_{5.5+x}$ system. Specifically, this mechanism involves symmetry breaking coupled with a SSO in the paramagnetic phase.

Isostructural compounds RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} (RE=La, Pr, Nd, Sm–Ho) with an ordered pyrochlore structure were synthesized. The structure of La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} was solved ab initio based on powder XRD data, and refined by combining with high resolution neutron diffraction data. La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} crystallizes in the space group R-3m with the unit cell parameters a=7.52954(2) A and c=17.59983(6) A. The structures of other members in this family are confirmed by Rietveld refinement using powder X-ray diffraction data. The cations (RE, Sb and Co) in RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} are orderly distributed, presenting as [RE{sub 3}Co][Sb{sub 3}Co]O{sub 14} formula, and giving rise to two distinctive Kagome lattices constructed by RE{sup 3+} and Sb{sup 5+}, respectively. Co{sup 2+} occupies 8-coordinated and 6-coordinated environments, showing low spin (S=1/2) and high spin (S=3/2) states respectively. The magnetic susceptibility and UV–visual spectroscopy supports the magnetic observation. TDDFT calculation was performed to interpret the electronic states. The compounds [RE{sub 3}Co][Sb{sub 3}Co]O{sub 14} provide a profound example in which the ideal 2D Kagome lattice is derived from the 3D pyrochlore-type structure by an ordered distribution of the metal cations. - Graphical abstract: La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} crystallizes inmore » a pyrochlore related structure with an ordered distribution of cations, giving rise to two sets of ideal 2D Kagome lattices formed by La{sup 3+} or Sb{sup 5+} respectively. This rhombohedral pyrochlore is a tolerant structure for stable compounds composed by many light rare-earth and d-transition elements. Substituting Zn{sup 2+} or Mg{sup 2+} for Co{sup 2+} will provide a series of compounds useful for studying magnetic interactions in the rare-earth Kagome lattices. - Highlights: • Pyrochlore-type La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} shows an ordered distribution of cations in its structure. • It presents two sets of ideal 2D Kagome lattices formed by La{sup 3+} or Sb{sup 5+}, respectively. • A family of isostructural compounds RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} (RE=Pr, Nd, Sm–Ho) were realized. • Co{sup 2+} presents two spin states with S=1/2, 3/2 due to two coordinated environments.« less

Three new organically templated zinc phosphates, namely, [ dmdabco ][Zn 2 (HPO 4 ) 3 ]·(H 2 O) ( 1 ), [tm pip ] 0.5 [Zn 2 (HPO 4 ) 2 (H 2 PO 4 )] ( 2 ) and [tm pip ][Zn 3 (HPO 4 ) 4 ] ( 3 ) (dm dabco = N,N′-dimethyl-1,4-diazabicyclo[2,2,2]octane, tm pip = N,N,N′,N′-tetramethyl-piperazinium), were successfully synthesized under solvothermal reactions and structurally characterized by single-crystal X-ray diffraction. The dm dabco 2 + and tm pip 2 + templating agents were derived respectively from simple in situ N -alkylation transformations between the methanol solvent and organic cyclic aliphatic diamines, 1,4-diazabicyclo[2,2,2]octane ( dabco ) in 1 and 1-methylpiperazine in 2 and 3 . Such direct methylation feature is unique, and quite different from conventional Eschweiler–Clarke methylation in which an excess of formic acid and formaldehyde was required. Compound 1 exhibits a 4-connected 2D (4, 4) net with pentameric [Zn 2 (HPO 4 ) 3 ] clusters as secondary building units (SBUs); 2 possesses a complex double layered structure with 12-ring windows. Compound 3 has a (3, 4)-connected 3D pcu architecture with heptameric [Zn 3 (HPO 4 ) 4 ] clusters as SBUs, forming intersecting 8- and 12-ring channels.

Borosilicate zeolites with CHA-type framework are synthesized hydrothermally by using N,N,N-trimethylcyclohexylammonium hydroxide as structure directing agent. The use of this cation induces an increase of boron content in the CHA-type zeolites, and the Si/B ratios of the as-synthesized samples is in the range of 11.8–6.9. Rietveld refinements of the calcinated samples reveal a contraction of unit cells with the increase of boron content, and the 8-ring opening window of cha cavity becomes narrower. 11B MAS NMR shows that all the boron atoms are incorporated into the framework as tetrahedral BO4 units in the as-synthesized samples. The thermal stability of these CHA-type borosilicates decreases with the increase of boron content, and the framework can retain up to 800 °C. These borosilicates, with the BET surfaces of 583–632 m2/g, show a high adsorption capacity for H2 at 77 K, 900 mmHg and a preferential adsorption for CO2 at 273 K. This selective adsorption property enables CHA-type borosilicates to be potential materials as CO2 adsorbent.

Employing the common pyridine (=py) solvent as the source of structure-directing agents (SDAs), a novel three-dimensional open-framework beryllium phosphite (Hpy)4[Be6(HPO3)8]·H2O (1), has been solvothermally synthesized and structurally characterized by IR, elemental analysis, thermogravimetric analysis, powder and single-crystal X-ray diffractions. It crystallizes in the orthorhombic system, space group Pbca (No. 61), a = 20.0034(4) A, b = 20.2188(4) A, c = 20.9731(3) A, V = 8482.5(3) A3, and Z = 8. The alternating connection of BeO4 tetrahedra and HPO3 pseudopyramids give rise to a (3, 4)-connected network with multidirectional intersecting 12-ring channels. The compound possesses a low density and a new {4.8.10}{42.6.8.10.12}{42.6}3{42.8.102.12}{43.62.8} topology.

Lanthanide upconversion (UC) materials that convert near-infrared excitations into visible emissions are of extensive current interest owing to their potential applications in biosensing, 3D displays, and solar cells. A wise choice of the host lattice is crucial for high-quality UC luminescence with desired emission wavelengths. From the viewpoint of structural chemistry, here we propose monoclinic scandium oxyfluoride (M-ScOF) as a promising UC host material for the following reasons: (1) the shortest Sc3+–Sc3+ distance (3.234 A, versus 3.584 A of Y3+–Y3+ in hexagonal NaYF4); (2) the unique crystallographic site of Sc in the structure; (3) specific coordination environment of Sc with 4O + 3F in C1 symmetry. Lanthanide doping in an individual host with such structural features is highly expected to achieve single band emission and fast energy migration for high-efficiency UC process. Experimentally, we employ a low temperature fluorination method to synthesize pure and lanthanides doped M-ScOF samples suc...

Two new organically templated zinc phosphites, [H2dmpip][Zn3(HPO3)4] (1) and [HMedmpip][Zn3(HPO3)4] (2), where dmpip = 2,6-dimethyl-piperazine and Medmpip = N-methyl-2,6-dimethyl-piperazinium, have been synthesized and structurally characterized. Note that the new Medmpip2 + template in 2 is generated from in situ N-methylation reaction between CH3OH and the dmpip amine precursor, which is used to serve as template in 1. Such direct N-methylation transformation is unique, and quite different from conventional Eschweiler–Clarke methylation in which an excess of formic acid and formaldehyde was required. Both compounds are constructed from strictly alternating ZnO4 and HPO3 units, and possess different (3,4)-connected interrupted frameworks with intersecting 8-, 10- and 12-ring channels (for 1), and 8-, 12-ring channels (for 2), respectively. The occurrence of helical channels in the open structure of 1, and fascinating hydrogen-bonded helices between the host inorganic chains and guest organic templates are also noteworthy.

Silicon is being investigated extensively as an anodic material for next-generation lithium ion batteries for portable energy storage and electric vehicles. However, the large changes in volume during cycling lead to the breakdown of the conductive network in Si anodes and the formation of an unstable solid-electrolyte interface, resulting in capacity fading. Here, we demonstrate nanoparticles with a Si@Mn22.6Si5.4C4@C double-shell structure and the formation of self-organized Si-Mn-C nanocomposite anodes during the lithiation/delithiation process. The anode consists of amorphous Si particles less than 10 nm in diameter and separated by an interconnected conductive/buffer network, which exhibits excellent charge transfer kinetics and charge/discharge performances. A stable specific capacity of 1100 mAh·g−1 at 100 mA·g−1 and a coulombic efficiency of 99.2% after 30 cycles are achieved. Additionally, a rate capacity of 343 mAh·g−1 and a coulombic efficiency of 99.4% at 12000 mA·g−1 are also attainable. Owing to its simplicity and applicability, this strategy for improving electrode performance paves a way for the development of high-performance Si-based anodic materials for lithium ion batteries.

Employing diethylenetriamine (=dien) as a structure-directing agent, a new open-framework beryllium phosphite H2dien·Be3(HPO3)4 (1), has been synthesized hydrothermally and structurally characterized by single crystal X-ray diffraction. The structure of 1 features a (3, 4)-connected framework with 8- and 12-ring channels, which is constructed from strictly alternating BeO4 tetrahedra and HPO32− pseudopyramids. The 3-D framework possesses a pcu topology when the heptameric [Be3(HPO3)4] clusters are regarded as 6-connected secondary building units. Crystal data: 1, monoclinic, C2/c (no. 15), a = 8.7350(3) A, b = 15.1704(6) A, c = 13.0851(4) A, β = 101.223(5)°, V = 1700.79(10) A3, Z = 4, R1 = 0.0625, wR2 = 0.1692.

Two new organically templated zinc phosphites, [tmpip]0.5[Zn2(HPO3)2(H2PO3)] (1) and [dmdabco][Zn3(HPO3)4]·(H2O) (2), have been synthesized under solvothermal conditions, where tmpip = N,N,N′,N′-tetramethyl-piperazinium and dmdabco = N,N′-dimethyl-1,4-diazabicyclo[2,2,2]octane. Note that the templating agents tmpip2 + and dmdabco2 + originated from in situ N-methylation transformations between CH3OH solvent and corresponding cyclic aliphatic amine precursors, i.e. piperazine, 1-methylpiperazine or 1,4-dimethylpiperazine in 1, and 1,4-diazabicyclo[2,2,2]octane in 2. Distinct from conventional Eschweiler–Clarke methylation with excess formic acid and formaldehyde, such direct methylation transformation from methanol molecules is unique. Compound 1 consists of ZnO4 tetrahedra, HPO3 and HPO2(OH) pseudopyramids, exhibiting a complex double layered structure with 12-ring windows. Compound 2 is constructed from strictly alternating ZnO4 tetrahedra and HPO3 pseudopyramids, and possesses a (3,4)-connected interrupted architecture with intersecting 8- and 12-ring channels.

PtCu x ( x = 1, 2 and 3) bimetallic nanocrystals with concave surface and dendritic morphology were prepared and used as electrocatalysts in methanol oxidation reaction (MOR) for polymer electrolyte membrane fuel cells. The bimetallic nanocrystals were synthesized via one-pot co-reduction of H 2 PtCl 6 and Cu(acac) 2 by oleylamine and polyvinyl pyrrolidone (PVP) in an autoclave at 180 °C. The concave dendritic bimetallic nanostructure consisted of a core rich in Cu and nanodendrites rich in Pt, which was formed via galvanic replacement of Cu by Pt. It was found that PVP played an important role in initiating, facilitating, and directing the replacement reaction. The electrochemical properties of the PtCu x were characterized by cyclic voltammetry (CV) and chronoamperometry (CA). The concave dendritic PtCu 2 /C nanocrystals exhibited exceptionally high activity and strong poisoning resistance in MOR. At 0.75 V (vs. reversible hydrogen electrode, RHE) the mass activity and specific activity of PtCu 2 /C were 3.3 and 4.1 times higher than those of the commercial Pt/C catalysts, respectively. The enhanced catalytic activity could be attributed to the unique concave dendritic morphology of the bimetallic nanocrystals.