Detection of Ascorbic Acid by Two-Dimensional Conductive Metal-Organic Framework-Based Electrochemical Sensors.

The realization of efficient and accurate detection of biomolecules has become a key scientific issue in the field of life sciences. With the rapid development of nanotechnology, electrochemical sensors constructed from the superior physical and chemical properties of nanomaterials show faster and more accurate detection. Among nanomaterials, two-dimensional conductive MOF (2D cMOF) is considered to be a star material in electrochemical sensors due to its remarkable conductivity, high porosity, and stability. In this paper, a Cu3(HHTP)2/SPE electrochemical sensor for the detection of ascorbic acid (AA) was constructed by modifying 2D cMOF (Cu3(HHTP)2) on the surface of the screen-printed electrode (SPE). The sensor exhibited excellent catalytic activity in the detection of AA, with a lower detection limit of 2.4 µmol/L (S/N = 3) and a wide linear range of 25-1645 µmol/L. This high catalytic activity can be attributed to the abundant catalytic sites in Cu3(HHTP)2 and the rapid electron transfer between Cu+ and Cu2+, which accelerates the oxidation of AA. This work lays a foundation for the subsequent development of MOFs with special electrochemical catalytic properties and the integration of 2D cMOF into intelligent electrical analysis devices.

The competition between the intrinsic and Rashba spin-orbit coupling and effects of correlations on Rashba SOC-driven transitions in the Kane-Mele model.

We investigate, firstly, the competition between the Rashba spin-orbit coupling (SOC) and the intrinsic SOC in Kane-Mele model. For the small intrinsic SOC, we investigate the effects of the Rashba SOC on the touching point of the valence and conduction bands when the ratio of the Rashba SOC to the intrinsic SOC is greater than classical value23. For the large intrinsic SOC, we find that the critical ratio of the two SOCs at which the band touching occurs decreases with the increasing intrinsic SOC and the locations of these touching points deviate from pointsKandK' of the Brillouin zone. Furthermore, effects of the Rashba SOC on these touching points are discussed in detail when the ratio is greater than the critical value. The Rashba SOC-driven topologically trivial and non-trivial transitions are also obtained in the first part of the work. Secondly, using the slave-rotor mean field method we investigate the influences of the correlation on the Rashba SOC-driven topologically trivial and non-trivial transitions in both the charge condensate and Mott regions. The topological Mott insulator with gapped or gapless spin excitations which arises from the interplay of the Rashba SOC and correlations is obtained in the work.

Tungstate-Catalyzed Biomimetic Oxidative Halogenation of (Hetero)Arene under Mild Condition.

Aryl halide (Br, Cl, I) is among the most important compounds in pharmaceutical industry, material science, and agrochemistry, broadly utilized in diverse transformations. Tremendous approaches have been established to prepare this scaffold; however, many of them suffer from atom economy, harsh condition, inability to be scaled up, or cost-unfriendly reagents and catalysts. Inspired by vanadium haloperoxidases herein we presented a biomimetic approach for halogenation (Br, Cl, I) of (hetero)arene catalyzed by tungstate under mild pH in a cost-efficient and environment- and operation-friendly manner. Broad substrates, diverse functional group tolerance, and good chemo- and regioselectivities were observed, even in late-stage halogenation of complex molecules. Moreover, this approach can be scaled up to over 100 g without time-consuming and costly column purification. Several drugs and key precursors for drugs bearing aryl halides (Br, Cl, I) have been conveniently prepared based on our approach.

Anticancer Molecule Discovery via C2-Substituent Promoted Oxidative Coupling of Indole and Enolate.

C2, C3-disubstituted indole is one of the most frequently encountered motifs in bioactive alkaloids and medicinal chemistry. Thus, developing novel, concise, and efficient access to it is highly desired in drug discovery. Herein, we present such an approach to this scaffold by direct oxidative coupling of C2-substituted indoles and enolates. Compared with indole bearing no C2-substituent, higher yields (up to 96%) were obtained for C2-substituted indoles in most cases. Mechanistic studies showed the reaction went through a Fe-chelated radical-anion oxidative coupling procedure promoted by C2-substituent on indole by two means: (1) stabilizing C2-radical intermediate during the reaction; (2) reducing indole homocoupling. This approach serves as a synthetic useful tool to quickly build up bioactive small molecule library of C2, C3-disubstituted indoles, and several products showed promising anticancer activities. Besides, indomethacin and its analogs were conveniently prepared in three-step sequence efficiently, indicating the potential application of our approach in medicinal chemistry.

Phase transitions of the Kane-Mele-Hubbard model with a long-range hopping.

The interacting Kane-Mele model with a long-range hopping is studied using analytical method. The original Kane-Mele model is defined on a honeycomb lattice. In the work, we introduce a four-lattice-constant range hopping and the on-site Hubbard interaction into the model and keep its lattice structure unchanged. From the single-particle energy spectrum, we obtain the critical strength of the long-range hopping t L at which the topological transition occurs in the non-interacting limit of the model and our results show that it is independent of the spin-orbit coupling. After introducing the Hubbard interaction, we investigate the Mott transition and the magnetic transition of the generalized strongly correlated Kane-Mele model using the slave-rotor mean field theory and Hartree-Fock mean field theory respectively. In the small long-range hopping region, it is a correlated quantum spin Hall state below the Mott transition, while a topological Mott insulator above the Mott transition. By comparing the energy band of spin degree of freedom with the one of electrons in non-interacting limit, we find a condition for the t L-driven topological transition. Under the condition, critical values of t L at which the topological transition occurs are obtained numerically from seven self-consistency equations in both regions below and above the Mott transition. Influences of the interaction and the spin-orbit coupling on the topological transition are discussed in this work. Finally, we show complete phase diagrams of the generalized interacting topological model at some strength of spin-orbital coupling.

Phase transitions of the dimerized Kane-Mele model with/without strong interaction.

The dimerized Kane-Mele model with/without strong interaction is studied using analytical methods. The boundary of the topological phase transition of the model without strong interaction is obtained. Our results show that the occurrence of the transition only depends on dimerized parameter [Formula: see text]. From the one-particle spectrum, we obtain the completed phase diagram including the quantum spin Hall state and the topologically trivial insulator. Then, using different mean field methods, we investigate the Mott transition and the magnetic transition of the strongly correlated dimerized Kane-Mele model. In the region between the two transitions, the topological Mott insulator with characteristics of Mott insulators and topological phases may be the most interesting phase. In this work, the effects of hopping anisotropy and Hubbard interaction U on the boundaries of the two transitions are observed in detail. The completed phase diagram of the dimerized Kane-Mele-Hubbard model is also obtained in this work. Quantum fluctuations have extremely important influences on a quantum system. However, investigations are under the framework of mean field treatment in this work and the effects of fluctuations in this model will be discussed in the future.

Synthesis and evaluation of tetrahydroindazole derivatives as sigma-2 receptor ligands.

A series of tetrahydroindazole derivatives were synthesized and evaluated for their affinities for both sigma-1 and sigma-2 receptors. These compounds are hybrid structures of a tetrahydroindazole substituted benzamide and a 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline moiety or a 9-azabicyclo[3.3.1]nonan-3-yl-amine moiety. These newly synthesized hybrid analogs showed various affinities for sigma-2 receptor without any significant affinities for sigma-1 receptor. In particular, compounds 12, 15b, 15c, and 15d, demonstrated moderate affinity and excellent selectivity for sigma-2 receptor. It is interesting to note that 3-5 carbon units between the tetrahydroindazole substituted benzamide and the 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline moiety are appropriate for sigma-2 receptor binding. No substitution on the 9-aza nitrogen is proper for sigma-2 affinity in the 2-(9-azabicyclo[3.3.1]nonan-3-yl-amino)-4-(3,6,6-trimethyl-4-oxo-4,5,6,7-tetrahydro-1H-indazol-1-yl)benzamide analogs.

Accelerating propagation properties of misplaced Hermite-Gaussian beams.

A new family of finite-energy accelerating beams was constructed through misplacing the Hermite polynomial and Gaussian window function. The closed-form solution of k-space spectra and paraxial propagation of these beams are derived from the Fourier transform and the scalar angle spectra integral. These beams have similar propagation properties to finite Airy beams and parabolic beams, but the accelerating trajectory is hyperbola rather than parabola. The beam family can be experimentally generated by exponentially truncating the high-order Hermite-Gaussian beams in the spatial domain.

Fast and noninterpolating method for subpixel displacement analysis of digital speckle images using phase shifts of spatial frequency spectra.

A fast noninterpolation method for calculating displacement of digital speckle images with subpixel precision was introduced. In this method, the precise displacement is obtained from phase shifts of spatial frequency spectra of two digital speckle images instead of digital correlation calculation. First, digital speckle images before and after displacement are windowed and fast Fourier transform is performed. Then, phase shifts of different spatial frequencies are linearly fitted in spectral space using the least square method, and a coarse displacement value is directly calculated according to the phase shift theorem of Fourier transform. By a window technique and iterative procedure, the influence of finite image size on the accuracy of the results is eliminated, and the accurate displacement is obtained finally. It is significant that the method obtains the subpixel-precision displacement without any interpolation operations. The test results show that the method has high computing efficiency, high precision, and good robustness to low image quality.

Sigma-2 receptor ligands and their perspectives in cancer diagnosis and therapy.

The sigma-2 receptor is highly expressed in various rapidly proliferating cancer cells and regarded as a cancer cell biomarker. Selective sigma-2 ligands have been shown to specifically label the tumor sites, induce cancer cells to undergo apoptosis, and inhibit tumor growth. Sigma-2 ligands are potentially useful as cancer diagnostics, anticancer therapeutics, or adjuvant anticancer treatment agents. However, both the cloning of this receptor and the identification of its endogenous ligand have not been successful, and the lack of structural information has severely hindered the understanding of its physiological roles, its signaling pathways, and the development of more selective sigma-2 ligands. Recent data have implicated that sigma-2 binding sites are within the lipid rafts and that PGRMC1 (progesterone receptor membrane component 1) complex and sigma-2 receptor may be coupled with EGFR (epidermal growth factor receptor), mTOR (mammalian target of rapamycin), caspases, and ion channels. Due to its promising applications in cancer management, there are rapidly increasing research efforts that are being directed into this field. This review article updates the current understanding of sigma-2 receptor and its potential physiological roles, applications, interaction with other effectors, with special focuses on the development of sigma-2 ligands, their chemical structures, pharmacological profiles, applications in imaging and anticancer therapy.