Synthesis of 2,3,6-trisubstituted pyridines by transition-metal free cyclization of 1,3-diynes with amino acids

Amino acids are firstly employed in transition-metal free heterocyclization reaction of 1,3-diynes in the presence of K₃PO₄ and DMSO at 120 °C. This method produces 2,3,6-trisubstituted pyridines with up to 86% yield. The –CO₂H group on the amino acids is crucial for this heterocyclization reaction. The mechanism of such a heterocyclization reaction is discussed, as well.     

Development of a light-up fluorescent probe for HRAS G-quadruplex DNA

The development of small-molecule G-quadruplex DNA probes has attracted significant attention in recent years. However, G-quadruplexes can display a wide variety of topologies, which process different structures and functions. Therefore, selective discrimination one G-quadruplex structure over another is promising. Herein, we reported the design, synthesis and biological evaluation of a long-chain fatty amine functionalized triphenylamine-quinolinium conjugate 1b. Significant enhancement of the fluorescence intensity (over 180 fold) was observed when 1b bound with HRAS G-quadruplex DNA, while much weaker enhancements were presented in the presence of other G-quadruplexes (45–90-fold) and single/double-stranded DNAs (less than 20-fold), indicating 1b had an excellent selectivity to HRAS. The details of the interactions were investigated by UV–Vis, FID and CD analysis. The results show 1b could interact and stabilize HRAS structure mainly by π-π stacking binding mode. The introduced amine chain of the structure core was found to be better in the terms of inducing selectivity toward G-quadruplex structure. In addition, the application of 1b as a fluorescent agent for living cell imaging was also demonstrated.     

Fluorometric aptamer based determination of adenosine triphosphate based on deoxyribonuclease I-aided target recycling and signal amplification using graphene oxide as a quencher

Microchimica Acta - The authors describe an aptamer based fluorometric assay for the determination of ATP. It is based on deoxyribonuclease I-aided target recycling and signal amplification. The...     

Atomically flat single terminated oxide substrate surfaces

Scientific interest in atomically controlled layer-by-layer fabrication of transition metal oxide thin films and heterostructures has increased intensely in recent decades for basic physics reasons as well as for technological applications. This trend has to do, in part, with the coming post-Moore era, and functional oxide electronics could be regarded as a viable alternative for the current semiconductor electronics. Furthermore, the interface of transition metal oxides is exposing many new emergent phenomena and is increasingly becoming a playground for testing new ideas in condensed matter physics. To achieve high quality epitaxial thin films and heterostructures of transition metal oxides with atomically controlled interfaces, one critical requirement is the use of atomically flat single terminated oxide substrates since the atomic arrangements and the reaction chemistry of the topmost surface layer of substrates determine the growth and consequent properties of the overlying films. Achieving the atomically flat and chemically single terminated surface state of commercially available substrates, however, requires judicious efforts because the surface of as-received substrates is of chemically mixed nature and also often polar. In this review, we summarize the surface treatment procedures to accomplish atomically flat surfaces with single terminating layer for various metal oxide substrates. We particularly focus on the substrates with lattice constant ranging from 4.00 Å to 3.70 Å, as the lattice constant of most perovskite materials falls into this range. For materials outside the range, one can utilize the substrates to induce compressive or tensile strain on the films and explore new states not available in bulk. The substrates covered in this review, which have been chosen with commercial availability and, most importantly, experimental practicality as a criterion, are KTaO₃, REScO₃ (RE = Rare-earth elements), SrTiO₃, La_0.18Sr_0.82Al_0.59Ta_0.41O₃ (LSAT), NdGaO₃, LaAlO₃, SrLaAlO₄, and YAlO₃. Analyzing all the established procedures, we conclude that atomically flat surfaces with selective A- or B-site single termination would be obtained for most commercially available oxide substrates. We further note that this topmost surface layer selectivity would provide an additional degree of freedom in searching for unforeseen emergent phenomena and functional applications in epitaxial oxide thin films and heterostructures with atomically controlled interfaces.     

Geometry of spacelike generalized constant ratio surfaces in Minkowski 3-space

Generalized constant ratio surfaces are defined by the property that the tangential component of the position vector is a principal direction on the surfaces. In this work, we study these class of surfaces in the 3-dimensional Minkowski space L³. We achieve a complete classification of spacelike generalized constant ratio surfaces in L³.     

A Comparison of NO Reduction Over Mn–Cu/ZSM5 and Mn–Cu/MWCNTs Catalysts Assisted by Plasma at Ambient Temperature

Manganese–copper bimetal oxide catalysts supported on ZSM5 and acid-treated multi-walled carbon nanotubes (MWCNTs) were produced by incipient wetness impregnation for selective catalytic reduction of NO with dielectric barrier discharge plasma. Plasma can activate molecules even at ambient temperature, generating active oxygen species such as O, O₃, and HO₂ radicals, which can oxidize NO to NO₂ effectively. The SCR activity of Mn–Cu/MWCNTs was studied and compared to that of the Mn–Cu/ZSM5. The obtained samples were characterized by XRD, SEM, TEM, ICP, H₂-TPR, Raman spectroscopy, and XPS. The results show that Mn–Cu/MWCNTs catalyst possesses NO removal activity superior to that of the Mn–Cu/ZSM5 catalyst. MWCNTs-based catalyst attains NO removal efficiency of 88% at 480 J/L, while the ZSM5-supported catalyst achieves NO removal efficiency of 82% at the same energy density. The oxygen content increased from 3.33 to 19.07% on the nanotube surface after introducing Mn and Cu, which almost remained unchanged on ZSM5. The oxygen-containing functionalities are important for NO_x adsorption and removal. Moreover, the characterization revealed that CuO is the main phase of copper oxide, but copper dispersion decreases on Mn–Cu/ZSM5 surface because of the formation of copper dimer species. The manganese is well-dispersed on the catalysts, MnO₂ and Mn₂O₃ contents of Mn–Cu/MWCNTs are larger than that of Mn–Cu/ZSM5, MnO₂ is the predominant phase of manganese oxide.     

Effect of ultraviolet absorption reagent for determination of piperidinium ionic liquid cations by ion pair chromatography with indirect ultraviolet detection

Indirect ultraviolet detection method is a simple and effective method for the determination of ionic liquid cations without ultraviolet absorption group. This paper focused on the influence of different background ultraviolet absorption reagents on the determination of piperidinium ionic liquid cations by ion pair chromatography with indirect ultraviolet detection. Ultraviolet absorption reagents are divided into cationic (4-aminophenol hydrochloride, 1-ethyl-3-methylimidazolium tetrafluoroborate, and N-ethylpyridinium tetrafluoroborate), anionic (potassium biphthalate and 5-sulfosalicylic acid), and amphiprotic (p-aminobenzoic acid). The results showed that piperidinium cations can be separated and detected by cationic and anionic ultraviolet absorption reagents. In general, the cationic ultraviolet absorption reagents have the best effect for separation and detection of the piperidinium cations by ion pair chromatography with indirect ultraviolet detection.     

Synthesis,characterization of new bisphenol-based benzoxazines and the thermal properties of their polymers

Journal of Thermal Analysis and Calorimetry - New bisphenol-based benzoxazines (BBA-a and BBA-bra) were synthesized from bisphenol containing trityl group, paraformaldehyde, aniline and...     

Lanthanide-organic frameworks based on terphenyl-tetracarboxylate ligands: syntheses,structures, optical properties and selective sensing of nitro explosives

Three isostructural three-dimensional(3D) lanthanide-based metal-organic frameworks [Ln_2L(H_2L)(NMP)_2].H_2O(Ln=Sm(1), Eu(2), Gd(3); H_4L=1,1′:4′,1″-terphenyl-2′,4,4″,5′-tetracarboxylic acid; NMP=N-methyl-2-pyrrolidone) have been synthesized and structurally characterized. In 1–3, two Ln3+ ions are doubly-bridged by two oxygen atoms of two carboxylate groups to form the dinuclear Ln_2(OCOO–)_2 unit. Each Ln_2(OCOO–)_2 unit links with four H_2L~(2-) ligands and four L4. ligands to lead to the 3D framework,which can be rationalized as a new trinodal 4,4,8-connected(44.62)(45.6)(412.616) topological network by considering the dinuclear Ln_2(OCOO–)_2 units as 8-connected nodes and L~4./H_2L~(2-) ligands as planar 4-connected nodes, respectively. 1 and 3 exhibit blue emission originated from the ligand with the emission maximum at 384 nm, while 2 shows intense characteristic red emission of Eu~(3+) ions and weak ligand-centered emission. Moreover, 2 has fluorescent quenching response towards the aromatic nitro compounds, especially for the 3,4-dinitrotoluene(3,4-DNT) with the linear Stern-Volmer relationship in the concentration range of 0–1 mM and the quenching constant(Ksv) of 2.084×10~3 M~(-1).