2D Transition Metal Dichalcogenides for Photocatalysis

Two-dimensional (2D) transition metal dichalcogenides (TMDs), a rising star in the post-graphene era, are fundamentally and technologically intriguing for photocatalysis. Their extraordinary electronic, optical, and chemical properties endow them as promising materials for effectively harvesting light and catalyzing the redox reaction in photocatalysis. Here, we present a tutorial-style review of the field of 2D TMDs for photocatalysis to educate researchers (especially the new-comers), which begins with a brief introduction of the fundamentals of 2D TMDs and photocatalysis along with the synthesis of this type of material, then look deeply into the merits of 2D TMDs as co-catalysts and active photocatalysts, followed by an overview of the challenges and corresponding strategies of 2D TMDs for photocatalysis, and finally look ahead this topic.     

Phosphine-Triggered Structural Defects in Au44 Homologues Boost Electrocatalytic CO2 Reduction

The systematic induction of structural defects at the atomic level is crucial to metal nanocluster research because it endows cluster-based catalysts with highly reactive centers and allows for a comprehensive investigation of viable reaction pathways. Herein, by substituting neutral phosphine ligands for surface anionic thiolate ligands, we establish that one or two Au₃ triangular units can be successfully introduced into the double-stranded helical kernel of Au₄₄(TBBT)₂₈, where TBBT=4-tert-butylbenzenethiolate, resulting in the formation of two atomically precise defective Au₄₄ nanoclusters. Along with the regular face-centered-cubic (fcc) nanocluster, the first series of mixed-ligand cluster homologues is identified, with a unified formula of Au₄₄(PPh₃)_n(TBBT)_28−2n (n=0–2). The Au₄₄(PPh₃)(TBBT)₂₆ nanocluster having major structural defects at the bottom of the fcc lattice demonstrates superior electrocatalytic performance in the CO₂ reduction to CO. Density functional theory calculations indicate that the active site near the defects significantly lowers the free energy for the *COOH formation, the rate-determining step in the whole catalytic process.     

Bipleiophylline, an unprecedented cytotoxic bisindole alkaloid constituted from the bridging of two indole moieties by an aromatic spacer unit

A cytotoxic bisindole alkaloid possessing an unprecedented structure in which two indole moieties are bridged by an aromatic spacer unit has been isolated from Alstonia angustifolia. The structure was established by analysis of the spectroscopic data and confirmed by X-ray diffraction analysis. A possible biogenetic pathway from pyrocatechuic acid and pleiocarpamine is presented.     

Hexagonal‐Shaped Tin Glycolate Particles: A Preliminary Study of Their Suitability as Li‐Ion Insertion Electrodes

Tin glycolate particles were prepared by a simple, one‐step, polyol‐mediated synthesis in air in which tin oxalate precursor was added to ethylene glycol and heated at reflux. Hexagonal‐shaped, micron‐sized tin glycolate particles were formed when the solution had cooled. A series of tin oxides was produced by calcination of the synthesized tin glycolate at 600–800 °C. It was revealed that the micron‐sized, hexagonal‐shaped tin glycolate now consisted of nanosized tin‐based particles (80–120 nm), encapsulated within a tin glycolate shell. XRD, TGA, and FT‐IR measurements were conducted to account for the three‐dimensional growth of the tin glycolate particles. When applied as an anode material for Li‐ion batteries, the synthesized tin glycolate particles showed good electrochemical reactivity in Li‐ion insertion/deinsertion, retaining a specific capacity of 416 mAh g^?1 beyond 50 cycles. This performance was significantly better than those of all the other tin oxides nanoparticles (<160 mAh g^?1) obtained after heat treatment in air. We strongly believe that the buffering of the volume expansion by the glycolate upon Li–Sn alloying is the main factor for the improved cycling of the electrode.     

The multiplier algebra of a nuclear quasidiagonal C*-algebra

If is a unital separable simple nuclear quasidiagonal C*-algebra,then ( ) has the AF-property in the strict topology; that is,there is a unital AF-subalgebra ( ) such that is strictlydense in ( ). We also give a multiplier algebra characterizationof nuclearity and quasidiagonality for a unital separable simpleC*-algebra.     

Synthesis,single crystal structure determination,and solution behavior of an 8-hydroxyquinoline derivative of niobium(V) ethoxide

An 8-hydroxyquinoline derivative of niobium(V) ethoxide was synthesized and characterized by elemental analysis, mass spectrometry, infrared, electronic, and ¹H, ¹³C, and ⁹³NMR spectroscopies. Tetraethoxy(8-quinolinato)niobium(V), as shown by the single crystal structure determination, exists as an octahedral compound in the solid state in which the 8-quinolinato group chelates to the metal atom. In solution, this group partially becomes unidentate; the six-coordinate species is in equilibrium with the five-coordinate species, as shown by ⁹³Nb and variable-temperature ¹H NMR spectroscopy.     

High sintering resistance of platinum nanoparticles embedded in a microporous hollow carbon shell fabricated through a photocatalytic reaction

Platinum (Pt) nanoparticles encapsulated in microporous carbon with a hollow structure (nPt@hC) were fabricated on the basis of a titanium(IV) oxide (TiO2) photocatalytic reaction. From the tomogram of a sample studied by using a transmission electron microscope (TEM), the Pt nanoparticles were found to be embedded in the carbon shell and were physically separated from each other by the carbon matrix. Owing to this unique structure, the Pt particles showed high resistance to sintering when subjected to thermal treatment at temperatures up to 800 degrees C. As a result, hydrogenation reactions using various heat-treated nPt@hCs as catalysts indicated that loss of catalytic activity was minimized. Thus, the present system will be a promising system for optimizing catalyst nanostructures utilized in processes requiring rigorous conditions.     

Infrared-vacuum ultraviolet-pulsed field ionization-photoelectron study of CH(3)I(+) using a high-resolution infrared laser

By using a high-resolution single mode infrared-optical parametric oscillator laser to prepare CH(3)I in single (J,K) rotational levels of the nu(1) (symmetric C-H stretching) =1 vibrational state, we have obtained rovibrationally resolved infrared-vacuum ultraviolet-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) spectra of the CH(3)I(+)(X(2)E(32);nu(1)(+)=1;J(+),P(+)) band, where (J,K) and (J(+),P(+)) represent the respective rotational quantum numbers of CH(3)I and CH(3)I(+). The IR-VUV-PFI-PE spectra observed for K=0 and 1 are found to have nearly identical structures. The IR-VUV-PFI-PE spectra for (J,K)=(5,0) and (7, 0) are also consistent with the previous J-selected IR-VUV-PFI-PE measurements. The analysis of these spectra indicates that the photoionization cross section of CH(3)I depends strongly on DeltaJ(+)=J(+)-J: but not on J and K. This observation lends strong support for the major assumption adopted for the semiempirical simulation scheme, which has been used for the simulation of the origin bands observed in VUV-PFI-PE study of polyatomic molecules. Using the state-to-state photoionization cross sections determined in this IR-VUV study, we have obtained excellent simulation of the VUV-PFI-PE origin band of CH(3)I(+)(X (2)E(32)), yielding more precise IE(CH(3)I)=76 930.7+/-0.5 cm(-1) and nu(1) (+)=2937.8+/-0.2 cm(-1).     

A vacuum ultraviolet laser photoionization and pulsed field ionization study of nascent S(3P2,1,0) and S(1D2) formed in the 193.3 nm photodissociation of CS2

The photoionization efficiency (PIE) and pulsed field ionization-photoion (PFI-PI) spectra for sulfur atoms S(3P2,1,0) and S(1D2) resulting from the 193.3 nm photodissociation of CS2 have been measured using tunable vacuum ultraviolet (vuv) laser radiation in the frequency range of 82 750-83 570 cm(-1). The PIE spectrum of S(3P2,1,0) near their ionization threshold exhibits steplike structures. On the basis of the velocity-mapped ion-imaging measurements, four strong autoionizing peaks observed in the PIE measurement in this frequency range have been identified to originate from vuv excitation of S(1D2). The PFI-PI measurement reveals over 120 previously unidentified new Rydberg lines. They have been assigned as Rydberg states [3p3(4S composite function nd3 D composite function (n=17-64)] converging to the ground ionic state S+(4S composite function) formed by vuv excitations of S(3P2,1,0). The converging limits of these Rydberg series have provided more accurate values, 82 985.43+/-0.05, 83 162.94+/-0.05, and 83 559.04+/-0.05 cm(-1) for the respective ionization energies of S(3P0), S(3P1), and S(3P2) to form S+(4S composite function). The relative intensities of the PFI-PI bands for S(3P0), S(3P1), and S(3P2) have been used to determine the branching ratios for these fine structure states, S(3P0):S(3P1):S(3P2)=1.00:1.54:3.55, produced by photodissociation of CS2 at 193.3 nm.