Search

2,6-pyridine dicarboxylic acid (DPA) is an exceptional biomarker of notorious anthrax spores. Therefore, the rapid, sensitive, and selective quantitative detection of DPA is extremely significant and urgent. This paper reports a Zn(II) metal–organic framework with the formula of {[Zn6(NDA)6(DPBT)3] 2H2O·3DMF}n (MOF-1), which consists of 2,6-naphthalenedicarboxylic acid (2,6-NDA), 4,7-di(4-pyridyl)-2,1,3-benzothiadiazole (DPBT), and Zn(II) ions. Structural analysis indicated that MOF-1 is a three-dimensional (3D) network which crystallized in the monoclinic system with the C2/c space group, revealing high pH, solvent, and thermal stability. Luminescence sensing studies demonstrated that MOF-1 had the potential to be a highly selective, sensitive, and recyclable fluorescence sensor for the identification of DPA. Furthermore, fluorescent test paper was made to detect DPA promptly with color changes. The enhancement mechanism was established by the hydrogen-bonding interaction and photoinduced electron transfer transition between MOF-1 and DPA molecules. [ABSTRACT FROM AUTHOR]

In this work, NH2‐containing organic ligand 5‐Aminoisophthalic acid (AIPA), and trans‐1,2‐bis(4‐pyridyl)ethene (bpe) were selected as organic ligands to construct a new two‐dimensional luminescent Zn(II) metal‐organic framework [Zn(AIPA)(bpe)1/2]⋅named MOF‐1. It is worth noting that MOF‐1 exhibited excellent thermal stability and chemical stability in common solvents and different pH aqueous solution. As we expected, the luminescence sensing investigations demonstrated that MOF‐1 could be deemed as a multifunctional fluorescence sensor toward Cr2O72− and Fe3+ via a "turn‐off" effect. Notably, MOF‐1 had high selectivity and sensitivity for Fe3+ and Cr2O72− with low detection limits of 9.72×10−5 M and 1.95×10−5 M, respectively. Furthermore, the possible quenching mechanisms were also explored in detail. [ABSTRACT FROM AUTHOR]

A new molecular magnetic compound, formulated as {[Mn2(L)2(C6H4ClSeO2)]2(ClO4)2}n (1) [H2L = 2,2′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))diphenol], has been synthesized, and analysed in terms of its structure and magnetic properties. The complex features a one-dimensional polymeric chain in which the Mn(III) ions are connected via a double phenoxido bridge and O–Se–O bridge. The magnetic behavior of the 1-D compound revealed canted antiferromagnetic interactions and SCM behavior characterized by Δτ = 36.9 K with pre-exponential factor τ0 = 3.99 × 10−9 s. It was noted that this SCM behavior was accompanied by a magnetic order leading to a canted antiferromagnet. This compound stands as an uncommon instance of an O–Se–O bridged Mn(III) system displaying SCM characteristics. [ABSTRACT FROM AUTHOR]

Under solvothermal condition, one new three-dimensional Co(II) metal–organic framework (MOF), namely {[Co2(TFBA)(μ3-O)(dpa)]·3DMF·9H2O}nCoMOF-1 (H3TFBA = tris(3′-F-4′-carboxybiphenyl)amine, dpa = 9,10-di(4-pyridyl)anthracene, DMF = N,N-dimethyl formamide) was successfully synthesized and characterized. CoMOF-1 displays three-dimensional framework with 2, 3, 10-c network topology based on tetranuclear [Co4O14] units. Besides, magnetic properties revealed that antiferromagnetic interactions between two adjacent metal centers. In addition, a series of luminescence sensing investigations demonstrated that CoMOF-1 could be used as a sensitive material toward nitrofuran antibiotics (nitrofurazone, NFZ, nitrofurantoin, NFT, furazolidone, FZD) with the average quenching Ksv values of 1.84 × 105 M−1, 1.78 × 105 M−1, and 1.2 × 105 M−1, and the limit of detection of 0.14 μM, 0.15 μM and 0.23 μM, respectively. Additionally, the possible luminescent quenching reasons for nitrofuran antibiotics were mainly due to competitive excitation and electron transfer mechanism. [ABSTRACT FROM AUTHOR]

One Ni(II)-Na(I) complex namely {[NiII-L-NaI(dca)]2}n [H2L = 1,2-ethanediylbis(2-iminomethylene-6-methoxy-phenol)] was synthesized under mild conditions at room temperature and characterized by elemental analysis, infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. Single crystal X-ray diffraction analyses show that Ni(II) centers are in four-coordinate D4h geometry and Na(I) centers are in a six-coordinate slightly distorted pentagonal pyramidal C5v geometry in the complex. The basic structural components of the complex are the [NiII-L-NaI] units, which are further connected by the dicyanamide through μ1,5 mode between the Na centers to form 1D chain structures. Thermogravimetric analysis indicate that complex 1 shows good thermal stability. [ABSTRACT FROM AUTHOR]

An efficient and stable CdS@MoS2 core@shell heterostructure was prepared by using a facile solvothermal approach. The MoS2@CdS heterostructure reveals efficient charge separation, giving rise to excellent performance on H2 generation from photocatalytic lactic acid decomposition. Thanks to the MoS2 shell protection, CdS corrosion was significantly prohibited, thus resulting in the long-term photocatalytic stability of the CdS@MoS2 heterostructure. The corresponding charge transfer properties and catalytic mechanism have been analyzed and discussed in detail. The present study provides a novel insight into the design of high performance and cost-effective photocatalysts. [ABSTRACT FROM AUTHOR]

A novel molecular magnetic material with the formula of {[Mn2(salen)2(C4H3SSeO2)](ClO4)}n (Complex 1) [salen = N,N′-(ethylene)bis(salicylideneiminato)] was designed, synthesized and characterized structurally and magnetically. This complex crystallizes in the triclinic space group Pī and exhibits a one-dimensional (1D) zig-zag chain structure, which is formed through linking Mn2(salen)2 dimers by O–Se–O in syn–syn coordination mode. All the Mn(III) atoms in the chain display a six-coordinate distorted octahedral geometry. It is revealed by static magnetic measurement that there is antiferromagnetic coupling between the Mn(III) ions through selenite ligands (O–Se–O), while ferromagnetic coupling through a double phenoxido bridge of the MnIII dimer. Due to the strong uniaxial anisotropy of Mn(salen), complex 1 behaves as the single chain magnet (SCM)-based antiferromagnet. This compound represents a rare example of an O–Se–O bridged Mn(III)-based system with the SCM dynamics. [ABSTRACT FROM AUTHOR]

The active sites of [FeFe]-hydrogenase promoted by Fe/E (E = S, Se) clusters have attracted considerable interest due to their significance in understanding the interconversion of hydrogen with protons and electrons. As an extension of the study on Fe/Se clusters related to H-cluster model compounds of [FeFe]-hydrogenase, a series of tertiary phosphine substituted Fe/Se carbonyls were successfully prepared. The treatment of Fe2(μ-SePh)2(CO)6 (A) and excess PR3 resulted in the ferrous bis(selenolate) carbonyls Fe(SePh)2(CO)2(PR3)2 (PR3 = PPhMe2, 1; PMe3, 2) in moderate yields. In striking contrast, the reaction of Fe2(μ-SeCH2Ph)2(CO)6 (B) with the same PR3 ligand resulted in the PR3-disubstituted models Fe2(μ-SeCH2Ph)2(CO)4(PR3)2 (PR3 = PPhMe2, 3; PMe3, 4) as the principal products. The more interesting finding is that two independent isomers (anti- and syn-) can be isolated according to different reaction temperatures. Further reactions of 3 or 4 with PR3 under UV irradiation afforded the first PR3-trisubstituted 2Fe2Se derivatives Fe2(μ-SeCH2Ph)2(CO)3(PR3)3 (PR3 = PPhMe2, 5; PMe3, 6). 6 could be further converted into the tetrasubstituted product Fe2(μ-SeCH2Ph)2(CO)2(PMe3)4 (7), while no further substitution was observed with 5 and excess of PPhMe2. All the prepared compounds were fully characterized by elemental analysis, various spectroscopic techniques and X-ray crystallography. In addition, some electrochemical properties of these models were studied by cyclic voltammetry (CV) in MeCN. Compounds 4, 6 and 7 were found to be catalysts for the H2 evolution reaction under electrochemical conditions. [ABSTRACT FROM AUTHOR]

Objectives: Temozolomide (TMZ) resistance is a key factor that restricts the therapeutic effect of glioblastoma (GBM). YTH‐domain family member 2 (YTHDF2) is highly expressed in GBM tissues, while the mechanism of YTHDF2 in TMZ resistance in GBM remains not fully elucidated. Methods: The YTHDF2 expression in TMZ‐resistant tissues and cells was detected. Kaplan–Meier analysis was employed to evaluate the prognostic value of YTHDF2 in GBM. Effect of YTHDF2 in TMZ resistance in GBM was explored via corresponding experiments. RNA sequence, FISH in conjugation with fluorescent immunostaining, RNA immunoprecipitation, dual‐luciferase reporter gene and immunofluorescence were applied to investigate the mechanism of YTHDF2 that boosted TMZ resistance in GBM. Results: YTHDF2 was up‐regulated in TMZ‐resistant tissues and cells, and patients with high expression of YTHDF2 showed lower survival rate than the patients with low expression of YTHDF2. The elevated YTHDF2 expression boosted TMZ resistance in GBM cells, and the decreased YTHDF2 expression enhanced TMZ sensitivity in TMZ‐resistant GBM cells. Mechanically, YTHDF2 bound to the N6‐methyladenosine (m6A) sites in the 3′UTR of EPHB3 and TNFAIP3 to decrease the mRNA stability. YTHDF2 activated the PI3K/Akt and NF‐κB signals through inhibiting expression of EPHB3 and TNFAIP3, and the inhibition of the two pathways attenuated YTHDF2‐mediated TMZ resistance. Conclusion: YTHDF2 enhanced TMZ resistance in GBM by activation of the PI3K/Akt and NF‐κB signalling pathways via inhibition of EPHB3 and TNFAIP3. [ABSTRACT FROM AUTHOR]

Two recently introduced concepts in the design of high-energy-density materials (HEDMs), namely Metal–organic frameworks (MOFs) and Chelating energetic material (CEM), have been applied in the synthesis of the energetic manganese (II) compound {[Mn(btm)(H2O)3]2·H2O}n (1) (H2btm = bis(tetrazole)methane), cocrystalized by a dinuclear CEM and a 1D MOF, which is characterized by elemental analysis and FTIR spectroscopy. Single-crystal X-ray diffraction analysis revealed that 1 crystallizes in the monoclinic space group P21/c. The Mn2+ was hexa-coordinated with two btm groups and three water molecules. Btm presents tridentate coordination modes. The thermal decomposition mechanism of 1 was studied by differential scanning calorimetry (DSC). The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa-Doyle's method, respectively. Sensitivity tests revealed that 1 is insensitive to mechanical stimuli. [ABSTRACT FROM AUTHOR]

A novel nitrogen and oxygen rich chelating energetic material (CEM) Zn(SCZ)2(H2O)2·2HTNR (1, SCZ = semicarbazide, TNR = styphnic acid) was prepared and characterized by elemental analysis, IR spectra and differential scanning calorimetry (DSC). Its crystal structure was determined through X-ray single crystal diffraction at 153(2) K. The crystal belongs to triclinic. Space group is P-1 with crystal parameters of the unit cell dimensions: a = 0.8284(2) nm, b = 1.1848(4) nm, c = 1.3411(4) nm, α = 99.617(4)°, β = 92.593(4)°, γ = 97.148(4)°, V = 1.2642(6) nm3, Z = 2 and Dc =1.943 g·cm–3. The kinetic parameters of the first exothermic process of 1 were studied by the Kissinger's method and Ozawa-Doyle's method. Sensitivity tests revealed that 1 is insensitive to mechanical stimuli. Energy of combustion and enthalpy of formation of 1 were calculated. [ABSTRACT FROM AUTHOR]

To deepen the study on heptacoordinate transition metal coordination complexes, a novel seven-coordinated coordination compound [Cd(SCZ)3·H2O](HTNR)2(H2O)2(1, SCZ = semicarbazide, H2TNR = styphnic acid) was synthesized and characterized by elemental analysis and FTIR spectroscopy. Single-crystal X-ray diffraction analysis revealed that1crystallizes in the triclinic space groupP-1. The thermal decomposition mechanism of1was studied by differential scanning calorimetry (DSC). The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa-Doyle's method, respectively. Sensitivity tests revealed that1is insensitive to mechanical stimuli. The heat of combustion was measured by oxygen bomb calorimetry and the enthalpy of formation was calculated. [ABSTRACT FROM PUBLISHER]

Using a semiclassical model, we investigate the effect of the initial longitudinal velocity of the tunnel-ionized electron on low-energy structure (LES) in above-threshold ionization (ATI) spectra. Our analysis shows that the effect (reduction or enhancement) of the initial longitudinal velocity pz0 on the LES is dependent on the direction of the initial longitudinal velocity. For the initial longitudinal velocity along the direction of the laser electric field at the moment of tunneling (i.e., pz0 > 0), the Coulomb interaction between the photoelectron and ion core is enhanced, while for the initial longitudinal velocity in the opposite direction (i.e., pz0 < 0), the Coulomb effect is reduced. Our work provides solid evidence that the initial electron longitudinal velocity has considerable effect on the photoelectron dynamics in the ATI process. [ABSTRACT FROM AUTHOR]

In this paper, the in-situ preparation and characterization of a porous copper-sodium perchlorate energetic nano-composite (PCu/NaClO4) and its electrical ignition properties are presented. Porous copper was in-situ produced by electro-deposition on a Ni/Cr alloy wire, which acts as a cathode during the electro-deposition. The PCu/NaClO4 nano-composite was produced by dipping the bridge with porous copper into a saturated sodium perchlorate acetone solution. SEM, EDS, and XRD were used to characterize the composite and DSC was used to study the thermal decomposition of the composite. The copper grain size was reduced by using additives such as CTAB in the electrolyte. The PCu/NaClO4 nano-composite on the bridge can be ignited by feeding a current through the bridge and the ignition delay time and electrical ignition sensitivity were measured. [ABSTRACT FROM AUTHOR]