Research on the mechanism of threefold discrepancy in thermal conductivity between room temperature and phase transition temperature for 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals.

Cracks originating from thermal expansion and thermally induced phase transitions significantly hinder thermal conduction in certain energetic materials. For 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals, a classic explosive, their temperature-dependent thermal conductivity serves as a crucial parameter determining safety and stability. In this work, the thermal conductivity of HMX single crystals before and after thermal damage under different heating conditions was measured and calculated, as well as the thermal conductivity of different regions of each single crystal. A threefold discrepancy in thermal conductivity was observed between room temperature and the phase transition temperature of the HMX crystal. The different effects of different types of damage and cracks, characterized by using 3D X-ray computed tomography (CT), on the thermal conduction process of the crystal were further analyzed. The results indicate that different heating methods influence the phase transformation of the crystals and the distributions of fast cracks and small cracks. The strong directivity of the fast cracks will significantly impact the thermal conductivity along two horizontal directions, whereas small cracks exert the greatest influence on the primary direction of heat conduction. The relevant conclusions were also verified by finite element analysis (FEA) modeling.

Exploration of Response Mechanisms in the Gills of Pacific Oyster (Crassostrea gigas) to Cadmium Exposure through Integrative Metabolomic and Transcriptomic Analyses.

Marine mollusks, including oysters, are highly tolerant to high levels of cadmium (Cd), but the molecular mechanisms underlying their molecular response to acute Cd exposure remain unclear. In this study, the Pacific oyster Crassostrea gigas was used as a biological model, exposed to acute Cd stress for 96 h. Transcriptomic analyses of their gills were performed, and metabolomic analyses further validated these results. In our study, a total of 111 differentially expressed metabolites (DEMs) and 2108 differentially expressed genes (DEGs) were identified under acute Cd exposure. Further analyses revealed alterations in key genes and metabolic pathways associated with heavy metal stress response. Cd exposure triggered physiological and metabolic responses in oysters, including enhanced oxidative stress and disturbances in energy metabolism, and these changes revealed the biological response of oysters to acute Cd stress. Moreover, oysters could effectively enhance the tolerance and detoxification ability to acute Cd exposure through activating ABC transporters, enhancing glutathione metabolism and sulfur relay system in gill cells, and regulating energy metabolism. This study reveals the molecular mechanism of acute Cd stress in oysters and explores the molecular mechanism of high tolerance to Cd in oysters by using combined metabolomics and transcriptome analysis.

Glycogen Quantification and Gender Identification in Di-, Tri-, and Tetraploid Crassostrea gigas Using Portable Near-Infrared Spectroscopy.

Near-infrared spectroscopy (NIR) has become an essential tool for non-destructive analysis in various fields, including aquaculture. This study presents a pioneering application of portable NIR spectrometers to analyze glycogen content in the gonadal tissues of the Pacific oyster (Crassostrea gigas), marking the first instance of developing quantitative models for glycogen in tetraploid C. gigas. The research also provides a comparative analysis with models for diploid and triploid oysters, underscoring the innovative use of portable NIR technology in aquaculture. Two portable NIR spectrometers were employed: the Micro NIR 1700 (908-1676 nm) and the Micro PHAZIR RX (1624-2460 nm). Near-infrared spectra were acquired from the gonadal tissues of diploid, triploid, and tetraploid C. gigas. Quantitative models for glycogen content were developed and validated using cross-validation methods. Additionally, qualitative models for different ploidies and genders were established. For the Micro NIR 1700, the cross-validation correlation coefficients (Rcv) and cross-validation relative predictive errors (RPDcv) for glycogen were 0.949 and 3.191 for diploids, 0.915 and 2.498 for triploids, and 0.902 and 2.310 for tetraploids. The Micro PHAZIR RX achieved Rcv and RPDcv values of 0.781 and 2.240 for diploids, 0.839 and 2.504 for triploids, and 0.717 and 1.851 for tetraploids. The Micro NIR 1700 demonstrated superior quantitative performance, with RPD values exceeding 2, indicating its effectiveness in predicting glycogen content across different ploidy levels. Qualitative models showed a performance index of 91.6 for diploid and 95 for tetraploid genders using the Micro NIR 1700, while the Micro PHAZIR RX achieved correct identification rates of 99.79% and 100% for diploid and tetraploid genders, respectively. However, differentiation of ploidies was less successful with both instruments. This study's originality lies in establishing the first quantitative models for glycogen content in tetraploid C. gigas using portable NIR spectrometers, highlighting the significant advancements in non-destructive glycogen analysis. The applicability of these findings is substantial for oyster breeding programs focused on enhancing meat quality traits. These models provide a valuable phenotyping tool for selecting oysters with optimal glycogen content, demonstrating the practical utility of portable NIR technology in aquaculture.

Exploration of Molecular Mechanisms of Immunity in the Pacific Oyster (Crassostrea gigas) in Response to Vibrio alginolyticus Invasion.

Over the years, oysters have faced recurring mass mortality issues during the summer breeding season, with Vibrio infection emerging as a significant contributing factor. Tubules of gill filaments were confirmed to be in the hematopoietic position in Crassostrea gigas, which produce hemocytes with immune defense capabilities. Additionally, the epithelial cells of oyster gills produce immune effectors to defend against pathogens. In light of this, we performed a transcriptome analysis of gill tissues obtained from C. gigas infected with Vibrio alginolyticus for 12 h and 48 h. Through this analysis, we identified 1024 differentially expressed genes (DEGs) at 12 h post-injection and 1079 DEGs at 48 h post-injection. Enrichment analysis of these DEGs revealed a significant association with immune-related Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. To further investigate the immune response, we constructed a protein-protein interaction (PPI) network using the DEGs enriched in immune-associated KEGG pathways. This network provided insights into the interactions and relationships among these genes, shedding light on the underlying mechanisms of the innate immune defense mechanism in oyster gills. To ensure the accuracy of our findings, we validated 16 key genes using quantitative RT-PCR. Overall, this study represents the first exploration of the innate immune defense mechanism in oyster gills using a PPI network approach. The findings provide valuable insights for future research on oyster pathogen control and the development of oysters with enhanced antimicrobial resistance.

High Spatial Resolution 2D Imaging of Current Density and Pressure for Graphene Devices under High Pressure Using Nitrogen-Vacancy Centers in Diamond.

Current density imaging is helpful for discovering interesting electronic phenomena and understanding carrier dynamics, and by combining pressure distributions, several pressure-induced novel physics may be comprehended. In this work, noninvasive, high-resolution two-dimensional images of the current density and pressure gradient for graphene ribbon and hBN-graphene-hBN devices are explored using nitrogen-vacancy (NV) centers in diamond under high pressure. The two-dimensional vector current density is reconstructed by the vector magnetic field mapped by the near-surface NV center layer in the diamond. The current density images accurately and clearly reproduce the complicated structure and current flow of graphene under high pressure. Additionally, the spatial distribution of the pressure is simultaneously mapped, rationalizing the nonuniformity of the current density under high pressure. The current method opens a significant new avenue to investigate electronic transport and conductance variations in two-dimensional materials and electrical devices under high pressure as well as for nondestructive evaluation of semiconductor circuits.

Guiding the Formation of Metal-Organic Structures of 1,4-Diaminoanthraquinone through Surface-Based Cu Atoms.

The gradual guidance of the formation of metal-organic structures through surface-based Cu atoms for 1,4-diaminoanthraquinones (DAQs) has been studied by scanning tunneling microscopy (STM) at room temperature. On the Ag(110) surface, the transition from a hydrogen-bond network structure to metal-organic coordination structures of DAQs can be induced by introducing foreign copper atoms. Due to the weak interaction between DAQs and Ag(110), thermal treatment easily leads to the desorption of DAQs from the surface. To address this challenge, Cu(111) is selected as the substrate. Under thermal driving and in the presence of copper adatoms, the hydrogen-bond network structure of DAQs on the surface gradually undergoes a transition into a metal-coordinated structure, eventually leading to the formation of metal-organic complexes through amino dehydrogenation. It is demonstrated that the construction of a metal-organic coordination structure on metal surfaces is a result of the competition among factors such as metal atoms, functional groups of molecules, surface chemical activity, and temperature.

Pressure-induced luminescence evolution of 3,3'-diamino-4,4'-azofurazan: Role of restricting chemical bond vibration and conformational modification.

The luminescence and electronic structure of 3,3'-Diamino-4,4'-azofurazan (DAAzF) were studied under high pressure conditions through experimental and calculation approaches. The transition of π* â†’ π was primarily responsible for DAAzF's broad light emission. Upon applying pressure to DAAzF, high-pressure-stiffened hydrogen-bond interactions enable the restriction of the stretching vibration of NH2 group. The reduced energy loss through nonradiative rotational relaxation and molecular motions lead to a ∼20 times luminescent enhancement of DAAzF from 1 atm to 8.9 GPa. With the further strengthening of interlayer hydrogen bond interactions at higher pressure, the deviation of hydrogen atoms in amino groups from the molecular plane lessens the radiation transition efficiency. In addition, the bending of the C-C-N=N bond further leads to molecular conformation changes at approximately 20.7 GPa, which induces an abrupt redshift and moderate quenching of the luminescence. Furthermore, the band gap of DAAzF is significantly influenced by pressure. As the color undergoes a transition from yellow to red, and becomes darker as the pressure increases, the absorption edge shifted towards red. At 3.4, 9, and 21 GPa, three conformational variations were identified in conjunction with electronic structural alterations.

Phase Transitions of Naphthalene-2,3-carbonitride Steered by Solvent Effects and Metal Ion Concentration Variation.

The delicate regulation of structural phase transition can provide advanced approaches for fabricating desired and well-organized nanoarchitectures on surfaces. Introduction of metal ions into pure organic systems can facilitate the phase transition from hydrogen-bonded structures to metal-organic structures by coordinating with organic molecules. However, it remains a challenge to attain a phase transition dominated by variable metal coordination configurations through adjustment of the metal ion concentration. Herein, we report the phase transitions of naphthalene-2,3-carbonitride (2,3-DCN) molecules on highly oriented pyrolytic graphite (HOPG) under varying solvents and Cu2+ ion concentrations. By integrating data from scanning tunneling microscopy imaging and density functional theory calculations, it is demonstrated that phase transitions of 2,3-DCN occur through forming diverse coordination configurations where Cu2+ ions can coordinate with 2,3-DCN and 1-nonanoic acid or Cl- ions to form different ligand components with a coordination number of 4 when varying the molar ratios of 2,3-DCN to Cu2+ ion in the 1-nonanoic acid solvent. However, in the case of 1-heptanoic acid as a solvent, the self-assembly structure of 2,3-DCN only changes via the alteration of hydrogen bonding sites and Cu2+ ions do not coordinate with 2,3-DCN molecules. These findings provide valuable insights into the coordination behavior of metal ions in different solvents.

Insights into the Rearrangement of the Molecular Assembly Structure of 6-Aminonicotinic Acid in Its Hydrated Environment.

Water, as a ubiquitous and essential component of life, is known to have a significant impact on the structure and function of organic molecules. In this study, we investigate the role of water in the phase transition of organic molecular assembly structures by scanning tunneling microscopy at room temperature. The results show that the -O-H···O hydrogen induced by water molecules can lead to a significant structural transition in the molecular assembly, specifically through selective weakening of -C-H···O between 6-aminonicotinic acid and the formation of new -O-H···O bonds between 6-aminonicotinic acid and water molecules. Subsequent thermal treatment of these molecular assembly structures reveals that the formation of -N-H···O hydrogen bonds induced by water molecules has created a different pathway for the phase transition of the molecular assembly structure. This knowledge has important implications for the design of organic molecules with specific nanostructures that can be controlled through hydration.

Pressure-Modulated Dissolution Behavior of LLM-105 Crystals in High-Temperature Water.

The exploration of the microstructural evolution and reaction kinetics of energetic materials with high-temperature and high-pressure water contributes to the understanding of their microscopic physicochemical origin, which can provide critical experimental data for the use of energetic materials. As a promising high-energy and insensitive energetic material, LLM-105 has been investigated under extreme conditions such as high pressure and high temperature. However, little information is available about the effect of water on LLM-105 under high pressure and high temperature. In this work, the interaction between LLM-105 and water under HP-HT was investigated in detail. As a result, the dissolving behavior of LLM-105 in water under high pressure and high temperature is related to the initial pressure. When the initial pressure is less than 1 GPa, LLM-105 crystals are dissolved in high-temperature water; when the initial pressure is above 1 GPa, LLM-105 particles are only decomposed in high-temperature water. When the solution is saturated at a high temperature, recrystallization of the LLM-105 sample appears in the solution. High pressure hindered the dissolution process of the sample in HP-HT water because the interaction between the solute and the solvent was weakened by high pressure. The initial pressure is one of the significant parameters that determines whether LLM-105 crystals can be dissolved in high-temperature water. More importantly, water under high pressure and high temperature can not only act as a solvent when dissolving the samples but also act as a catalyst to accelerate the decomposition process. In addition, the HP-HT water reduced the decomposition temperature of the LLM-105 crystal to a large extent. The research in this paper not only provides insights into the interaction between LLM-105 and water but also contributes to the performance of energetic materials under extreme conditions and their practical applications in complex conditions.

Isothermal structural evolution of CL-20/HMX cocrystals under slow roasting at 190 °C.

As a new type of energetic material, cocrystal explosives demonstrate many excellent properties, such as high energy density and low sensitivity, due to the interaction between the molecules of the two components. The known decomposition temperature is 235 °C for CL-20/HMX cocrystals at a faster heating rate. CL-20 molecules could separate from the cocrystal matrix and decompose at a higher temperature, much lower than the decomposition temperature. The current work provided deep insight into the isothermal structural evolution of CL-20/HMX cocrystals with slow roasting at 190 °C. We found that the initial decomposition originates from separating CL-20 molecules from the surface along the (010) plane of the cocrystals. The gas products, such as NO2 and NO, escape from the largest exposed surface of the (010) plane and generates microbubbles and microholes. At the same time, the residual HMX molecules form δ-phase HMX crystals and shrink the volume by 72%. By increasing the time held at 190 °C, the decomposition of CL-20 molecules and recrystallization of the residual HMX molecules form a gully-like structure on the (010) plane of the CL-20/HMX cocrystal. After a long time at 190 °C, the CL-20 component completely decomposes, and all HMX molecules recrystallize in the δ-HMX form. The interaction between HMX and CL-20 molecules makes the decomposition rate of the CL-20/HMX cocrystal much slower than that of the CL-20 pure crystal with a similar decomposition activation energy during isothermal heating. This work can help to deeply understand the safety of CL-20/HMX cocrystal explosives at a temperature lower than the recognized decomposition temperature.

Structural evolution of CL-20/DNB cocrystals at high temperature: Phase transition and kinetics of thermal decomposition.

As a typical new energetic material, CL-20/DNB cocrystals have been recognized as a promising explosive owing to their excellent comprehensive performance. The thermal decomposition behavior, structural evolution and dynamic process of CL-20/DNB cocrystals under high temperature were studied by means of thermogravimetric differential heating, X-ray diffraction, Raman spectroscopy to gain insight into the cocrystal materials. The study found that the decomposition of CL-20/DNB cocrystal is a heterogeneous process accompanied by the sublimation of DNB and structural change of CL-20. The phase transition of ߠ→ Î³-CL-20 was observed at 120 °C. The kinetics of decomposition and the mechanism of micro structural evolution on CL-20/DNB cocrystals with heating were revealed. The primary NO⋯H hydrogen bonds of the cocrystal are broken, accompanied by the melting of DNB in the temperature range of 100-120 °C. Subsequently, the DNB single component decomposes completely, leading to lattice collapse of cocrystal; simultaneously, CL-20 undergoes a transition process from ß phase to γ phase. Ultimately, γ-CL-20 gradually decomposes with increasing temperature. The activation energy of cocrystal is also obtained as 129 ± 10 kJ/mol. The understanding of cocrystal explosive was deepened and the further application was promoted.

Diagnostic value and safety of ultrathin bronchoscope and endobronchial ultrasonography with a guide sheath combined with rapid on-site evaluation system for peripheral pulmonary infectious diseases.

BACKGROUND: The aim of this study was to investigate the diagnostic value and safety of ultrathin bronchoscope and endobronchial ultrasonography with a guide sheath (EBUS-GS) combined with rapid on-site evaluation (ROSE) system for peripheral pulmonary infectious diseases. METHODS: The clinical data of 196 patients visiting our hospital, who had peripheral pulmonary lesions (PPLs) indicated by spiral computed tomography (CT) of the chest and were finally diagnosed as infectious PPLs, were retrospectively collected. Then the patients were divided into ultrathin bronchoscope + ROSE group, EBUS-GS + ROSE group and ultrathin bronchoscope + EBUS-GS + ROSE group based on different diagnostic techniques. Moreover, the general conditions, diagnostic results and specific operation parameters of the patients were recorded, and the diagnostic rate, sensitivity and complications were compared. RESULTS: In ultrathin bronchoscope + EBUS-GS + ROSE group, the time of localizing lesions and operation time were the shortest, and the grade of bronchi reached by the bronchoscope was the highest. The differences were significant between any two groups (P<0.05). Patients with bacterial pneumonia, and patients with pulmonary tuberculosis and nontuberculous mycobacterial disease, ultrathin bronchoscope + EBUS-GS + ROSE group exhibited the highest definite diagnosis rate of bronchoscope and diagnostic sensitivity of ROSE system, with significant differences from those of the other two groups (P<0.05). The incidence rates of complications were low in all groups, and there were no significant differences between any two groups (P>0.05). CONCLUSIONS: Ultrathin bronchoscope and EBUS-GS combined with ROSE system can prominently decrease the time of localizing lesions and operation time, remarkably improve the diagnostic accuracy and sensitivity and result in fewer complications.

Mechanical Properties Evaluation of Polymer-Binding C-S-H Structure from Nanoscale to Macroscale: Hydroxyl-Terminated Polydimethylsiloxane (PDMS) Modified C-S-H.

Exploring and modifying the C-S-H structure at a micro-nano level is an effective solution to improve the performance of Portland cement. Compared with organics inserting C-S-H, the research on the performance of a polymer-binding C-S-H structure from nanoscale to macroscale is limited. In this work, the mechanical properties of a modified C-S-H, using hydroxyl-terminated polydimethylsiloxane (PDMS) as the binders, are evaluated. The PDMS-modified C-S-H structures are introduced into macro-defect-free cement to obtain stress-strain curves changes at a macro scale. The AFM-FM was adopted to measure the morphology and elastic modulus of C-S-H at a nano scale. The molecular dynamics (MD) simulation was performed to assess the toughness, tensile properties, and failure mechanism. The results show that the PDMS-modified C-S-H powders change the break process and enhance ductility of MDF cement. The elastic modulus of PDMS-modified C-S-H is lower than pure C-S-H. When PDMS molecules are located between the stacking crystal units, it can enhance the toughness of C-S-H aggregates. The PDMS-modified C-S-H stacking structure has better plasticity, and its tensile strains are higher than the pure C-S-H. PDMS molecules hinder the initial crack expansion, leading to the branching of the initial crack. In addition, the measurement of AFM-FM can identify and obtain the mechanical properties of basic units of C-S-H. This paper enhances the understanding of cement strength sources and modification methods.

Biofunctional roles of estrogen in coronavirus disease 2019: Beyond a steroid hormone.

The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), epidemic poses a major global public health threat with more than one million daily new infections and hundreds of deaths. To combat this global pandemic, efficient prevention and management strategies are urgently needed. Together with the main characteristics of COVID-19, impaired coagulation with dysfunctions of the immune response in COVID-19 pathophysiology causes high mortality and morbidity. From recent clinical observations, increased expression of specific types of estrogen appears to protect patients from SARS-CoV-2 infection, thereby, reducing mortality. COVID-19 severity is less common in women than in men, particularly in menopausal women. Furthermore, estrogen levels are negatively correlated with COVID-19 severity and mortality. These findings suggest that estrogen plays a protective role in the pathophysiology of COVID-19. In this review, we discuss the potential roles of estrogen in blocking the SARS-CoV-2 from invading alveolar cells and replicating, and summarize the potential mechanisms of anti-inflammation, immune modulation, reactive oxygen species resistance, anti-thrombosis, vascular dilation, and vascular endothelium protection. Finally, the potential therapeutic effects of estrogen against COVID-19 are reviewed. This review provides insights into the role of estrogen and its use as a potential strategy to reduce the mortality associated with COVID-19, and possibly other viral infections and discusses the possible challenges and pertinent questions.

Orthorhombic-to-Hexagonal Phase Transition of REF3 (RE = Sm to Lu and Y) under High Pressure.

For the famous functional REF3 family, there exist two typical structures, that is, orthorhombic phase and hexagonal phase. In the present work, high pressure behaviors of the orthorhombic phase REF3 (RE = Sm to Lu and Y) were investigated by experimental methods and first-principles calculations. The pressure-induced phase transitions of GdF3, TbF3, YbF3, and LuF3 were studied by using in situ photoluminescence measurements in the diamond anvil cell. At room temperature, all these four compounds follow the phase transition route from orthorhombic to hexagonal phase at 5.5-20.6 GPa. The pressure ranges of phase transition are 5.5-9.3, 8.4-11.9, 13.5-20.3, and 14.8-20.6 GPa for GdF3, TbF3, YbF3, and LuF3, respectively. In combination with first-principles calculations, we infer that all orthorhombic REF3 members from Sm-Lu and Y obey the same orthorhombic-to-hexagonal phase transition rules under high pressures. For lanthanide trifluorides, the transition pressures increase as zero pressure volumes of REF3 in the orthorhombic phase become smaller. As the calculation results show, this is because the difference in value of energy from the two structures is larger. This work not only provides precise structural change but also benefits the understanding of two typical structures for rare-earth trifluorides, which may play a significant role in the applications of REF3.

Three-Bit Digital Comparator Based on Intracell Diffusion of Silver Single Atom.

Using a single atom to construct electronic components is a promising route for the microminiaturization of electronic instruments. However, effective control of the intrinsic property in a molecular/atomic prototype component is full of challenges. Here, we present that the intracell diffusion behavior of a target Ag single atom within a unit cell of Si reconstruction is controllably modulated by constructing Ag nanoclusters and arrays in the neighboring cells. Moreover, a three-bit digital comparator device is fabricated on the basis of the diffusion time of a Ag single atom that can be effectively regulated by using the intercoupling between the target Ag monomer and the surrounding metal arrays.

Inference of a "Hot Ice" Layer in Nitrogen-Rich Planets: Demixing the Phase Diagram and Phase Composition for Variable Concentration Helium-Nitrogen Mixtures Based on Isothermal Compression.

Van der Waals (vdW) chemistry in simple molecular systems may be important for understanding the structure and properties of the interiors of the outer planets and their satellites, where pressures are high and such components may be abundant. In the current study, Raman spectra and visual observation are employed to investigate the phase separation and composition determination for helium-nitrogen mixtures with helium concentrations from 20 to 95% along the 295 K isothermal compression. Fluid-fluid-solid triple-phase equilibrium and several equilibria of two phases including fluid-fluid and fluid-solid have been observed in different helium-nitrogen mixtures upon loading or unloading pressure. The homogeneous fluid in helium-nitrogen mixtures separates into a helium-rich fluid (F1) and a nitrogen-rich fluid (F2) with increasing pressure. The triple-phase point occurs at 295 K and 8.8 GPa for a solid-phase (N2)11He vdW compound, fluid F1 with around 50% helium, and fluid F2 with 95% helium. Helium concentrations of F1 coexisted with the (N2)11He vdW compound or δ-N2 in helium-nitrogen mixtures with different helium concentrations between 40 and 50% and between 20 and 40%, respectively. In addition, the helium concentration of F2 is the same in helium-nitrogen mixtures with different helium concentrations and decreases upon loading pressure. Pressure-induced nitrogen molecule ordering at 32.6 GPa and a structural phase transition at 110 GPa are observed in (N2)11He. In addition, at 187 GPa, a pressure-induced transition to an amorphous state is identified.

Transformation of the coordination nanostructures of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid molecules on HOPG triggered by the change in the concentration of metal ions.

The modulation effects of Cu2+/Fe3+ ions on the hydrogen-bonded structure of 4,4',4''-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid (TATB) on a HOPG surface have been investigated at the liquid-solid interface by scanning tunneling microscopy (STM). STM observations directly demonstrated that the self-assembled honeycomb network of TATB has been dramatically transformed after introducing CuCl2/FeCl3 with different concentrations. The metal-organic coordination structures are formed due to the incorporation of the Cu2+/Fe3+ ions. Interestingly, a Cu2+ ion remains coordinated to two COOH groups and only the number of COOH groups involved in coordination doubles when the concentration of Cu2+ ions doubled. A Fe3+ ion changes from coordination to three COOH groups to two COOH groups after increasing the concentration of Fe3+ ions in a mixed solution. Such results suggest that the self-assembled structures of TATB molecules formed by metal-ligand coordination bonds can be effectively adjusted by regulating the concentration of metal ions in a mixed solution, which has rarely been reported before. It explains that the regulatory effect of concentration leads to the diversity of molecular architectures dominated by coordination bonds.

Directing on-surface polymerization via a substrate-directed molecular template.

Using a template to control the on-surface polymerization process is valuable for building functional molecular nanostructures. Here, the role of the symmetric matching between a halogen-ligand component (H2TBrPP) and the substrate for the fabrication of a regular metal-organic structure on Cu(111) and Cu(100) surfaces was studied using scanning tunnelling microscopy (STM). Considering the formation of short-range order polymers on the Au(111) surface via the process of debromination due to the weak directing effect from the substrate to the precursors, a bilayer of ordered assembled structure of H2TBrPP/Au(111) has been fabricated and the molecules in the top layer are guided by the first-layer molecules. Owing to the steering effect of the substrate-directed molecular template, the H2TBrPP components in the top layer were polymerized into ordered molecular chain arrays along the given direction that is determined by the initial close-packed assembled structure of H2TBrPP components during the post-annealing treatment.