Ambient-Condition Recoverable Polymeric N10 Discovered from the Predicted Zr-N Compounds.

Polynitrogen has been widely studied recently as a rising star of high energy density materials. Here, we performed a systematic study of the Zr-N compounds in the N-rich region by the first-principles method. The high-pressure phase diagram of the Zr-N system is enriched by proposing five new compounds. ZrN10 with the infinitely extended band shaped structure is first reported. The band-like polynitrogen of ZrN10 decomposes into a more stable chain-like polynitrogen structure under the influence of temperature. Additionally, the novel honeycomb-like band-shaped N10 structure hcb-N10 has been discovered by removing the Zr atoms. The absence of the -4 oxidation state in the N10 unit prompts its further polymerization, which makes hcb-N10 possess dynamical and thermal stability in ambient conditions. hcb-N10 is a semiconductor with a bandgap of 2.97 eV due to highly localized electrons. Both chain-ZrN10 and hcb-N10 represent potential candidates for HEDMs with outstanding energy and explosive performance.

Realizing long range π-conjugation in phenanthrene and phenanthrene-based molecular crystals for anomalous piezoluminescence.

Unlike the known aggregation-caused quenching (ACQ) that the enhancement of π-π interactions in rigid organic molecules usually decreases the luminescent emission, here we show that an intermolecular "head-to-head" π-π interaction in the phenanthrene crystal, forming the so-called "transannular effect", could result in a higher degree of electron delocalization and thus photoluminescent emission enhancement. Such a transannular effect is molecular configuration and stacking dependent, which is absent in the isomers of phenanthrene but can be realized again in the designed phenanthrene-based cocrystals. The transannular effect becomes more significant upon compression and causes anomalous piezoluminescent enhancement in the crystals. Our findings thus provide new insights into the effects of π-π interactions on luminescence emission and also offer new pathways for designing efficient aggregation-induced emission (AIE) materials to advance their applications.

Influence of ligands on the optical properties of rod-shaped Au25 nanoclusters.

In this study, we successfully synthesized rod-shaped [Au25(PPh3)10(S-Adm)5Cl2]2+ nanoclusters using kinetic controls. The complete molecular structure was determined by single-crystal X-ray crystallography and electrospray ionization mass spectrometry. In comparison with the previously reported [Au25(PPh3)10(PET)5Cl2]2+ clusters, both nanoclusters have an icosahedral composition of Au13 linked by Au atoms that share a vertex, but [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters appear elongated due to the rigidity of adamantane. We conducted ultraviolet-visible spectrophotometry (UV-vis) measurements of [Au25(PPh3)10(PET)5Cl2]2+ and [Au25(PPh3)10(S-Adm)5Cl2]2+ in dichloromethane solvent to elucidate the modulation of the cluster properties of different ligands. The lowest energy absorption peak of [Au25(PPh3)10(S-Adm)5Cl2]2+ shifted to lower energies compared to the [Au25(PPh3)10(PET)5Cl2]2+ clusters in UV-vis measurements. Temperature-dependent absorption measurements revealed that [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters were less affected by temperature compared to [Au25(PPh3)10(PET)5Cl2]2+. This result is attributed to the exciton phonon coupling of [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters being weaker than [Au25(PPh3)10(PET)5Cl2]2+ clusters. Furthermore, the absorption spectra of [Au25(PPh3)10(PET)5Cl2]2+ and [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters were measured using different types of solutions, and it was found that the lowest energy absorption peaks of [Au25(PPh3)10(S-Adm)5Cl2]2+ were shifted and affected by the solution at room temperature, which suggested that the [Au25(PPh3)10(S-Adm)5Cl2]2+ clusters with solution hydrogen bonds also interacted strongly at room temperature. Theoretical calculations show that changes in ligands affect the differences in the molecular orbitals and structures of the clusters, which cause changes in the optical properties.

Amorphous Metal-Organic Framework-Derived Electrocatalyst to Boost Water Oxidation.

Amorphous metal-organic framework (MOF) materials have drawn extensive interest in the design of high-performance electrocatalysts for use in the electrochemical oxygen evolution reaction. However, there are limitations to the utilization of amorphous MOFs due to their low electrical conductivity and unsatisfactory stability. Herein, a novel amorphous-crystalline (AC) heterostructure is successfully constructed by synthesizing a crystalline metal sulfide (MS)-embedded amorphous Ni0.67Fe0.33-MOF, namely an MS/Ni0.67Fe0.33-MOF. It exhibits excellent catalytic performance (a low overpotential of 248 mV at 10 mA cm-2 with a small Tafel slope of 50 mV decade-1), durability, and stability (only 8% degradation of the current density at a constant voltage after 24 h). This work thus sheds light on the engineering of highly efficient catalysts with AC heterointerfaces for optimizing water-splitting systems.

Electrical devices designed based on inorganic clusters.

The idea of exploring the bottom brink of material science has been carried out for more than two decades. Clusters science is the frontmost study of all nanoscale structures. Being an example of 0-dimensional quantum dot, nanocluster serves as the bridge between atomic and conventionally understood solid-state physics. The forming mechanism of clusters is found to be the mutual effects of electronic and geometric configuration. It is found that electronic shell structure influences the properties and geometric structure of the cluster until its size becomes larger, where electronic effects submerge in geometric structure. The discrete electronic structures depend on the size and conformation of clusters, which can be controlled artificially for potential device applications. Especially, small clusters with a size of 1-2 nm, whose electronic states are possibly discrete enough to overcome thermal fluctuations, are expected to build a single-electron transistor with room temperature operation. However, exciting as the progress may be seen, cluster science still falls within the territory of merely the extension of atomic and molecular science. Its production rate limits the scientific and potential application research of nanoclusters. It is suggested in this review that the mass-produce ability without losing the atomic precision selectivity would be the milestone for nanoclusters to advance to material science.

Anomalous pressure-responsive emission enhancement of FCO-CzS due to molecular configuration and electronic structure changes.

Studying the stimuli-responsive properties of luminescent materials is important for their applications, while the luminescent materials studied up to now usually exhibit emission quenching and red shift in photoluminescence (PL) energy upon compression. Designing luminescent material with abnormal pressure responses remains challenging. Here, we report the discovery of abnormal luminescent properties of FCO-CzS upon compression. A theoretical study on the excited state decay process has been carried out for FCO-CzS at high pressure by hybrid quantum mechanics/molecular mechanics (QM/MM). A significant emission enhancement and blue shift are observed as pressure increases up to 20 GPa. This is opposite to the pressure response behaviours reported for other luminescent materials. It is further revealed that both the unique molecular configuration and the electronic structure change contribute to the anomalous pressure-responsive emission of FCO-CzS, which reduces the non-radiative rate and increases the radiative rate, respectively. Our study provides a strategy for the design of luminescent materials with desired pressure responses.

Novel polymeric phases proposed by cold-pressing SiC tubes.

A detailed structural evolution behavior of SiC single-wall nanotubes (SiC SWNTs) under high-pressure is studied by using density functional theory. We proposed four new polymeric phases (hP4-SiC, hP48-SiC, oI32-SiC and oA40-SiC), which possess the high stability, outstanding electronic and mechanical properties. The hP4-SiC, hP48-SiC and oA40-SiC are indirect band gap semiconductors, while the oI32-SiC is direct band gap semiconductor. The exhibited suitable band gap (∼3.1 eV) allows hP4-SiC, hP48-SiC, oI32-SiC and oA40-SiC as the potential blue-laser diodes materials. The Si-C bond in four new structures is the strong covalent bond in sp3hybridization, which results in their high stability and hardness. The exhibited high decomposition temperature and high hardness make them as the potential high temperature abrasive materials. The stacking way of different rings in structures and atomic arrangement configurations of C and Si atoms in rings induce the anisotropic stiffness of polymeric structures. The analysis of x-ray diffraction, Raman and infrared radiation spectra is performed for a guideline of their synthesis in experiment. These results would help to understand the structural evolution of SiC SWNTs under high pressure and contribute to develop the high hardness and temperature materials.

Pressure-stabilized polymerization of nitrogen in manganese nitrides at ambient and high pressures.

Two stable high-pressure phases (C2/m-MnN4 and P1̄-MnN4) and four metastable phases (P4/mmm-MnN4, P1̄-MnN5, C2/m-MnN6 and P1̄-MnN8) are proposed by using ab initio evolutionary simulations. Besides the reported quasi-diatomic molecule N2, the armchair chain and S-like chain, the N4 ring and N22 ring are firstly reported in the P4/mmm-MnN4 and P1̄-MnN5 phases. A detailed study is performed on the energetic properties, mechanical properties and stability of these polynitrogen structures. Ab initio molecular dynamics simulations show that P1̄-MnN4 and P1̄-MnN5 can be quenched down to ambient conditions, and large decomposition energy barriers result in the high decomposition temperatures of P1̄-MnN4 (2000 K) and P1̄-MnN5 (3000 K). Interestingly, P4/mmm-MnN4 with the N4 ring exhibits outstanding mechanical properties, including high incompressibility, high hardness, uniform strength in the 2-D direction and excellent ductility. Strong N-N covalent bond and weak Mn-N ionic bond interactions are observed in the predicted Mn-N compounds, and the charge transfer between the Mn and N atoms provides an important contribution to the stabilization of polymeric N-structures. All the proposed structures are metallic phases. Our results provide a deep understanding of the chemistry of transition metal polynitrides under pressure and encourage experimental synthesis of these new manganese polynitrides in future.

Interface-Induced Self-Assembly Strategy Toward 2D Ordered Mesoporous Carbon/MXene Heterostructures for High-Performance Supercapacitors.

Invited for this month's cover is the group of Zhen-An Qiao at the Jilin University. The image shows the application of 2D ordered mesoporous carbon/MXene heterostructures in supercapacitors. The Full Paper itself is available at 10.1002/cssc.202101374.

Interface-Induced Self-Assembly Strategy Toward 2D Ordered Mesoporous Carbon/MXene Heterostructures for High-Performance Supercapacitors.

Two-dimensional transition metal carbonitrides (MXene) have demonstrated great potential in many fields. However, the serious aggregation and poor thermodynamic stability of MXene greatly hinder their applications. Here, an interface-induced self-assembly strategy to synthesize ordered mesoporous carbon/Ti3 C2 Tx heterostructures (OMCTs) was developed. In this method, the composite monomicelles formed by Pluronic F127 and low-molecular-weight phenolic resol self-assembled on the surface of Ti3 C2 Tx to prevent the restacking of Ti3 C2 Tx and maintain its thermostability. The obtained OMCTs possessed high specific surface areas (259-544 m2 g-1 ), large pore volumes (0.296-0.481 cm3 g-1 ), and excellent thermodynamic stability (up to 600 °C). Benefiting from these advantages, OMCTs serving as the electrode materials for supercapacitor exhibited superior supercapacitor performances, including high capacitance of 247 F g-1 at 0.2 A g-1 , satisfactory rate performance of 190 F g-1 at 5 A g-1 , and cyclability.

Pressure-Induced Electronic and Structural Transition in Nodal-Line Semimetal ZrSiSe.

The nodal-line semimetals have recently gained attention as a promising material due to their exotic electronic structure and properties. Here, we investigated the structural evolution and physical properties of nodal-line semimetal ZrSiSe under pressure via experiments and theoretical calculations. An isostructural electronic transition is observed at ∼6 GPa. Upon further compression, the original tetragonal phase starts to transform into an orthorhombic phase at ∼13 GPa and the two phases coexist until the maximal experimental pressure. By analysis of the electronic band structure, we suggest that the significant changes in the Fermi surface contribute to the occurrence of the isostructural electronic transition. The results provide a new insight into the structure and properties of ZrSiSe.

Enhanced Methanol Electro-Oxidation Activity of Nanoclustered Gold.

Size-selected 3 nm gas-phase Au clusters dispersed by cluster beam deposition (CBD) on a conducting fluorine-doped tin oxide template show strong enhancement in mass activity for the methanol electro-oxidation (MEO) reaction compared to previously reported nanostructured gold electrodes. Density functional theory-based modeling on the corresponding Au clusters guided by experiments attributes this high MEO activity to the high density of exposed under-coordinated Au atoms at their faceted surface. In the description of the activity trends, vertices and edges are the most active sites due to their favorable CO and OH adsorption energies. The faceted structures occurring in this size range, partly preserved upon deposition, may also prevent destructive restructuring during the oxidation-reduction cycle. These results highlight the benefits of using CBD in fine-tuning material properties on the nanoscale and designing high-performance fuel cell electrodes with less material usage.

A Gd@C82 single-molecule electret.

Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C82. The encapsulated Gd atom forms a charged centre that sets up two single-electron transport channels. A gate voltage of ±11 V (corresponding to a coercive field of ~50 mV Å-1) switches the system between the two transport channels with a ferroelectricity-like hysteresis loop. Using density functional theory, we assign the two states to two different permanent electrical dipole orientations generated from the Gd atom being trapped at two different sites inside the C82 cage. The two dipole states are separated by a transition energy barrier of 11 meV. The conductance switching is then attributed to the electric-field-driven reorientation of the individual dipole, as the coercive field provides the necessary energy to overcome the transition barrier.

Pressure tuned photoluminescence and band gap in two-dimensional layered g-C3N4: the effect of interlayer interactions.

We show that the photoluminescence (PL) emission color of few layered g-C3N4 (FL-CN) can be tuned from blue to yellow by applying pressure. FL-CN also exhibits an anomalous PL enhancement and obvious change in the light absorption at very low pressure. Further studies reveal that the increase of pressure-induced interlayer interactions affects the charge separation of photo-induced electrons and holes and thus leads to PL enhancement. An obvious decrease in interlayer compressibility probably due to interlayer stacking transition in FL-CN has been observed at above 3 GPa, which becomes less compressible than that of graphite, accompanied by obvious PL intensity weakening and emission band broadening. The results suggest that interlayer interactions may play dominant roles in the optical properties of FL-CN, shedding new insights into our understanding on PL engineering in g-C3N4.

A platinum-nickel bimetallic nanocluster ensemble-on-polyaniline nanofilm for enhanced electrocatalytic oxidation of dopamine.

We report a new approach to design flexible functional material platforms based on electropolymerized polyaniline (PANI) polymer nanofilms modified with bimetallic nanoclusters (NCs) for efficient electro-oxidation of small organic molecules. Composition defined ligand free Pt0.75Ni0.25 NCs were synthesized in the gas phase using the Cluster Beam Deposition (CBD) technology and characterized using RToF, HAADF-STEM, XAFS and XPS. NCs were then directly deposited on PANI coated templates to construct electrodes. Dopamine (DP) molecules were used as a representative organic analyte and the influence of the NC-PANI hybrid atomistic structure on the electrochemical and electrocatalytic performance was investigated. The as prepared, nearly monodispersed, Pt0.75Ni0.25 NCs of ca. 2 nm diameter featuring a PtOx surface combined with a shallow platelet-like Ni-O(OH) phase formed a densely packed active surface on PANI at ultralow metal coverages. Electrochemical measurements (EIS and CV) show a 2.5 times decrease in charge transfer resistance and a remarkable 6-fold increase at lower potential in the mass activity for Pt0.75Ni0.25 NCs in comparison with their pure Pt counterparts. The enhanced electrochemical performance of the Pt0.75Ni0.25 NC hybrid's interface is ascribed to the formation of mixed Pt metal and Ni-O(OH) phases at the surface of the alloyed PtNi cores of the bimetallic NCs under electrochemical conditions combined with an efficient charge conduction pathway between NCs.

Decompression-Induced Diamond Formation from Graphite Sheared under Pressure.

Graphite is known to transform into diamond under dynamic compression or under combined high pressure and high temperature, either by a concerted mechanism or by a nucleation mechanism. However, these mechanisms fail to explain the recently reported discovery of diamond formation during ambient temperature compression combined with shear stress. Here we report a new transition pathway for graphite to diamond under compression combined with shear, based on results from both theoretical simulations and advanced experiments. In contrast to the known model for thermally activated diamond formation under pressure, the shear-induced diamond formation takes place during the decompression process via structural transitions. At a high pressure with large shear, graphite transforms into ultrastrong sp^{3} phases whose structures depend on the degree of shear stress. These metastable sp^{3} phases transform into either diamond or graphite upon decompression. Our results explain several recent experimental observations of low-temperature diamond formation. They also emphasize the importance of shear stress for diamond formation, providing new insight into the graphite-diamond transformation mechanism.

Applying Mobile Augmented Reality (AR) to Teach Interior Design Students in Layout Plans: Evaluation of Learning Effectiveness Based on the ARCS Model of Learning Motivation Theory.

In this paper we present a mobile augmented reality (MAR) application supporting teaching activities in interior design. The application supports students in learning interior layout design, interior design symbols, and the effects of different design layout decisions. Utilizing the latest AR technology, users can place 3D models of virtual objects as e.g., chairs or tables on top of a design layout plan and interact with these on their mobile devices. Students can experience alternative design decision in real-time and increases the special perception of interior designs. Our system fully supports the import of interior deployment layouts and the generation of 3D models based on design artefacts based on typical design layout plan design symbols and allows the user to investigate different design alternatives. We applied John Keller's Attention, Relevance, Confidence, and Satisfaction (ARCS) learning motivation model to validate our solution to examine the students' willingness and verify the ability of students to improve learning through MAR technology. We compared a sample experimental group of N = 52 test-subjects with a sample of N = 48 candidates in a control group. Learning indicators as learning interest, confidence, satisfaction and effective have been utilized to assess the students' learning motivation through the use of MAR technology. The learning results have been determined by the independent sample t testing. The significance of the post-test had a p-value < 0.05 difference. The result of the study clearly shows that the reference group utilizing MAR technology as a learning aid show a higher learning effectiveness as the control group. Thus, we conclude that MAR technology does enhance students' learning ability for interior design and making appropriate design decisions.

Unravelling the nucleation mechanism of bimetallic nanoparticles with composition-tunable core-shell arrangement.

The structure and atomic ordering of Au-Ag nanoparticles grown in the gas phase are determined by a combination of HAADF-STEM, XPS and Refl-XAFS techniques as a function of composition. It is shown consistently from all the techniques that an inversion of chemical ordering takes place by going from Au-rich to Ag-rich compositions, with the minority element always occupying the nanoparticle core, and the majority element enriching the shell. With the aid of DFT calculations, this composition-tunable chemical arrangement is rationalized in terms of a four-step growth process in which the very first stage of cluster nucleation plays a crucial role. The four-step growth mechanism is based on mechanisms of a general character, likely to be applicable to a variety of binary systems besides Au-Ag.

Atomic Resolution Observation of a Size-Dependent Change in the Ripening Modes of Mass-Selected Au Nanoclusters Involved in CO Oxidation.

Identifying the ripening modes of supported metal nanoparticles used in heterogeneous catalysis can provide important insights into the mechanisms that lead to sintering. We report the observation of a crossover from Smoluchowski to Ostwald ripening, under realistic reaction conditions, for monomodal populations of precisely defined gold particles in the nanometer size range, as a function of decreasing particle size. We study the effects of the CO oxidation reaction on the size distributions and atomic structures of mass-selected Au(561±13), Au(923±20) and Au(2057±45) clusters supported on amorphous carbon films. Under the same conditions, Au(561±13) and Au(923±20) clusters are found to exhibit Ostwald ripening, whereas Au(2057±45) ripens through cluster diffusion and coalescence only (Smoluchowski ripening). The Ostwald ripening is not activated by thermal annealing or heating in O2 alone.

Hybrid atomic structure of the Schmid cluster Au55(PPh3)12Cl6 resolved by aberration-corrected STEM.

We have investigated the atomic structure of the Au55(PPh3)12Cl6 Schmid cluster by using aberration-corrected scanning transmission electron microscopy (STEM) combined with multislice simulation of STEM images. Atom counting was employed, with size-selected clusters as mass standards, to "fractionate" the correct cluster size in the image analysis. Systematic structure analysis shows that a hybrid structure, predicted by density functional theory, best matches nearly half the clusters observed. Most other clusters are amorphous. We believe our conclusions are consistent with all the previous, apparently contradictory structural studies of the Schmid cluster.