Clustering-Evolved Frontier Orbital for Low-Temperature CO2 Dissociation.

In this study, single Ni2 clusters (two Ni atoms bridged by a lattice oxygen) are successfully synthesized on monolayered CuO. They exhibit a remarkable activity toward low-temperature CO2 thermal dissociation, in contrast to cationic Ni atoms that nondissociatively adsorb CO2 and metallic Ni ones that are chemically inert for CO2 adsorption. Density functional theory calculations reveal that the Ni2 clusters can significantly alter the spatial symmetry of their unoccupied frontier orbitals to match the occupied counterpart of the CO2 molecule and enable its low-temperature dissociation. This study may help advance single-cluster catalysis and exploit the unexcavated mechanism for low-temperature CO2 activation.

Diazulenorubicene as a Non-benzenoid Isomer of peri-Tetracene with Two Sets of 5/7/5 Membered Rings Showing Good Semiconducting Properties.

Non-benzenoid polycyclic aromatic hydrocarbons (PAHs) have received a lot of attention because of their unique optical, electronic, and magnetic properties, but their synthesis remains challenging. Herein, we report a non-benzenoid isomer of peri-tetracene, diazulenorubicene (DAR), with two sets of 5/7/5 membered rings synthesized by a (3+2) annulation reaction. Compared with the precursor containing only 5/7 membered rings, the newly formed five membered rings switch the aromaticity of the original heptagon/pentagon from antiaromatic/aromatic to non-aromatic/antiaromatic respectively, modify the intermolecular packing modes, and lower the LUMO levels. Notably, compound 2 b (DAR-TMS) shows p-type semiconducting properties with a hole mobility up to 1.27 cm2  V-1 s-1 . Moreover, further extension to larger non-benzenoid PAHs with 19 rings was achieved through on-surface chemistry from the DAR derivative with one alkynyl group.

Single-Cation Catalyst: Ni Cation in Monolayered CuO for CO Oxidation.

It is vital to differentiate catalytic properties between cationic and metallic single atoms at the atomic level. To achieve this, we fabricated well-defined cationic Ni atoms snugged in and metallic Ni atoms supported on monolayered CuO. The Ni cations are chemically inert for CO adsorption even at 70 K but highly active toward O2 dissociation at room temperature. The adsorbed O atoms are active to oxidize incoming CO molecules from the gas phase into CO2, which follows the Eley-Rideal mechanism, in contrast to the Mars-van Krevelen mechanism on CuO-monolayer-supported metallic Ni atoms as well as our previously reported Au and Pt model catalysts. This study helps understand the chemistry of a supported single-metal cation, which is of great importance in heterogeneous catalysis.

Formation of Unconventional Stoichiometric Na-Cl Magic-Number Nanoclusters and 2D Assembly on Ir(111).

Sodium chlorides in non-1:1 stoichiometry are counterintuitive but recently their existence has been found under the high pressure condition or in the confined space between graphene sheets. Here the direct observation of the formation of Na3 Cl nanoclusters, a stable magic-number structure, is reported on an Ir(111) surface using scanning tunneling microscopy and noncontact atomic force microscopy. The stability of Na3 Cl nanoclusters in the free and adsorbed state is corroborated by density functional theory calculations. It is also found that a density of nanoclusters together with Cl adatoms may further aggregate and self-assemble into a Na3 Cl4 monolayer, forming a novel metastable phase of NaCl(111) with a honeycomb lattice. Further calculations suggest that charge transfer between the polar nanoclusters and the metal substrate stabilizes NaCl of non-1:1 stoichiometry. The work exhibits the possibility of exploring unconventional ionic crystals on the surface with atomically precise control of structure and composition.

Structural Phase Transitions of Molecular Self-Assembly Driven by Nonbonded Metal Adatoms.

The involvement of metal atoms in molecular assemblies has enriched the structural and functional diversity of two-dimensional supramolecular networks, where metal atoms are incorporated into the architecture via coordination or ionic bonding. Here we present a temperature-variable study of the self-assembly of the 1,3,5-tribromobenzene (TriBB) molecule on Cu(111) that reveals the involvement of nonbonded adatoms in the molecular matrix. By means of scanning tunneling microscopy and noncontact atomic force microscopy, we demonstrate the molecular-level details of a phase transition of TriBB assembly from the close-packed to porous honeycomb structures at 78 K. This is an unexpected transformation because the close-packed phase is thermodynamically favored in view of its higher molecular density and more intermolecular bonds as compared to the honeycomb lattice. A comprehensive density functional theory calculation suggests that Cu adatoms should be involved in the formation of the honeycomb network, where the Cu adatoms help stabilize the molecular assembly via enhanced van der Waals interactions between TriBB molecules and the underlying substrate. Both calculation and experimental results suggest no chemical bonding or direct charge transfer between the adatoms and the molecules, thus the electronic characteristics of the Cu adatoms trapped in the molecular confinement are close to the intrinsic ones on a clean metal surface and different from those in the traditional coordination-bonded framework. The nonbonded metal adatoms embedded self-assemblies may complement the metal-organic coordination system and can be used to tailor the chemical reactivity and electronic properties of supramolecular structures.

High-Yield Formation of Graphdiyne Macrocycles through On-Surface Assembling and Coupling Reaction.

Rationally designed halogenated hydrocarbons are widely used building blocks to fabricate covalent-bonded carbon nanostructures on surfaces through a reaction pathway involving generation and dissociation of organometallic intermediates and irreversible covalent bond formation. Here, we provide a comprehensive picture of the on-surface-assisted homocoupling reaction of 1,3-bis(2-bromoethynyl)benzene on Au(111), aiming for the synthesis of graphdiyne nanostructures. Submolecular resolution scanning tunneling microscopy and noncontact atomic force microscopy observations identify the organometallic intermediates and their self-assemblies formed in the dehalogenation process. The demetallization of the organometallic intermediates at increased temperatures produces butadiyne moieties that spontaneously formed two different covalent structures ( i.e., graphdiyne zigzag chains and macrocycles), whose ratio was found to depend on the initial coverage of organometallic intermediates. At the optimal condition, the stepwise demetallization and cyclization led to a high-yield production of graphdiyne macrocycles up to 95%. Statistical analysis and theoretical calculations suggested that the favored formation of macrocycles resulted from the complex interplay between thermodynamic and kinetic processes involving the organometallic bonded intermediates and the covalently bonded butadiyne moieties.

Direct Formation of C-C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of gem-Dibromomethyl Molecules.

Conductive polymers are of great importance in a variety of chemistry-related disciplines and applications. The recently developed bottom-up on-surface synthesis strategy provides us with opportunities for the fabrication of various nanostructures in a flexible and facile manner, which could be investigated by high-resolution microscopic techniques in real space. Herein, we designed and synthesized molecular precursors functionalized with benzal  gem-dibromomethyl groups. A combination of scanning tunneling microscopy, noncontact atomic force microscopy, high-resolution synchrotron radiation photoemission spectroscopy, and density functional theory calculations demonstrated that it is feasible to achieve the direct formation of C-C double-bonded structural motifs via on-surface dehalogenative homocoupling reactions on the Au(111) surface. Correspondingly, we convert the sp3-hybridized state to an sp2-hybridized state of carbon atoms, i. e., from an alkyl group to an alkenyl one. Moreover, by such a bottom-up strategy, we have successfully fabricated poly(phenylenevinylene) chains on the surface, which is anticipated to inspire further studies toward understanding the nature of conductive polymers at the atomic scale.

On-surface synthesis of poly(p-phenylene ethynylene) molecular wires via in situ formation of carbon-carbon triple bond.

The carbon-carbon triple bond (-C≡C-) is an elementary constituent for the construction of conjugated molecular wires and carbon allotropes such as carbyne and graphyne. Here we describe a general approach to in situ synthesize -C≡C- bond on Cu(111) surface via homo-coupling of the trichloromethyl groups, enabling the fabrication of individual and arrays of poly(p-phenylene ethynylene) molecular wires. Scanning tunneling spectroscopy reveals a delocalized electronic state extending along these molecular wires, whose structure is unraveled by atomically resolved images of scanning tunneling microscopy and noncontact atomic force microscopy. Combined with density functional theory calculations, we identify the intermediates formed in the sequential dechlorination process, including surface-bound benzyl, carbene, and carbyne radicals. Our method overcomes the limitation of previous on-surface syntheses of -C≡C- incorporated systems, which require the precursors containing alkyne group; it therefore allows for a more flexible design and fabrication of molecular architectures with tailored properties.

Direct Formation of C-C Triple-Bonded Structural Motifs by On-Surface Dehalogenative Homocouplings of Tribromomethyl-Substituted Arenes.

On-surface synthesis shows significant potential in constructing novel nanostructures/nanomaterials, which has been intensely studied in recent years. The formation of acetylenic scaffolds provides an important route to the fabrication of emerging carbon nanostructures, including carbyne, graphyne, and graphdiyne, which feature chemically vulnerable sp-hybridized carbon atoms. Herein, we designed and synthesized a tribromomethyl-substituted compound. By using a combination of high-resolution scanning tunneling microscopy, non-contact atomic force microscopy, and density functional theory calculations, we demonstrated that it is feasible to convert these compounds directly into C-C triple-bonded structural motifs by on-surface dehalogenative homocoupling reactions. Concurrently, sp3 -hybridized carbon atoms are converted into sp-hybridized ones, that is, an alkyl group is transformed into an alkynyl moiety. Moreover, we achieved the formation of dimer structures, one-dimensional molecular wires, and two-dimensional molecular networks on Au(111) surfaces, which should inspire further studies towards two-dimensional graphyne structures.

Graphene-like nanoribbons periodically embedded with four- and eight-membered rings.

Embedding non-hexagonal rings into sp2-hybridized carbon networks is considered a promising strategy to enrich the family of low-dimensional graphenic structures. However, non-hexagonal rings are energetically unstable compared to the hexagonal counterparts, making it challenging to embed non-hexagonal rings into carbon-based nanostructures in a controllable manner. Here, we report an on-surface synthesis of graphene-like nanoribbons with periodically embedded four- and eight-membered rings. The scanning tunnelling microscopy and atomic force microscopy study revealed that four- and eight-membered rings are formed between adjacent perylene backbones with a planar configuration. The non-hexagonal rings as a topological modification markedly change the electronic properties of the nanoribbons. The highest occupied and lowest unoccupied ribbon states are mainly distributed around the eight- and four-membered rings, respectively. The realization of graphene-like nanoribbons comprising non-hexagonal rings demonstrates a controllable route to fabricate non-hexagonal rings in nanoribbons and makes it possible to unveil their unique properties induced by non-hexagonal rings.

[Clinical significance of high-sensitivity C-reactive protein in development of chronic hepatitis B].

OBJECTIVE: To explore the clinical significance of high-sensitivity C-reactive protein (hsCRP) in the development of chronic hepatitis B (CHB). METHODS: A total of 182 patients with untreated CHB and 50 healthy individuals (controls) participated in the study. Correlation analysis was performed to determine the association of serum hs-CRP with the age,sex,medical history,serum hepatitis B virus (HBV) DNA, liver function parameters,liver stiffness measure (LSM) and hepatic fibrosis; in addition, correlation analysis was carried out for the associations of degree of liver damage with grade of hepatic fibrosis, LSM and the serum levels of hs-CRP. RESULTS: CHB patients showed significantly higher serum hs-CRP levels than healthy controls (2.38 ± 2.79 vs.0.78 ± 1.07; t =2.495, P < 0.05). Serum hs-CRP levels were significantly correlated with HBV DNA (r = 0.159), liver function parameters (total bilirubin, r = 0.271; alanine aminotransferase, r = 0.298; aspartate aminotransferase, r = 0.389), and LSM, r = 0.562) (all P < 0.05). The correlations with liver function (r = 0.340), LSM (r = 0.292) and hepatic fibrosis grade were positive (r = 0.434) (all P < 0.01). CONCLUSION: Serum hs-CRP levels in CHB patients can reflect degree of liver damage and of liver fibrosis.

Serum high-sensitivity C-reactive protein are associated with HBV replication, liver damage and fibrosis in patients with chronic hepatitis B.

BACKGROUND/AIMS: The aim of this study was to explore the potential role of serum high-sensitivity C-reactive protein (hs-CRP) in the pathogenic process of chronic hepatitis B. METHODOLOGY: A total of 380 patients with chronic hepatitis B were included in this study. All patients received the concentrations of serum hs-CRP, Hepatitis B sero-markers, serum HBV-DNA loads, liver function parameters and liver stiffness were measured, and in which 172 patients undertaken liver biopsy and immunohistochemistry analysis. RESULTS: Serum hs-CRP concentration in patients with the chronic hepatitis B (2.38 ± 5.52) was significantly higher than healthy controls (0.60 ± 0.53), P < 0.05. The area under ROC curve in fibrosis S4 and S3 is 0.826 and 0.78. The sensitivity and specificity of hs-CRP for fibrosis S3 and S4 diagnosis were 81.8%, 80% and 73.4%, 76.2% respectively (cut off: 1.01 mg/ml, 1.11 mg/l). CONCLUSIONS: C-reactive Protein are associated with HBV replication, liver damage and fibrosis in patients with chronic hepatitis B, and serum High-sensitivity C-reactive Protein may be a marker for diagnosing significant fibrosis in patients with chronic hepatitis B, and can reflect the severity of liver damage.