Raman Investigations of Atomic/Molecular Clusters and Aggregates

Efforts to tune optic responses of molecular aggregates often alter the characteristics and performance of functional materials, revealing that chemical properties largely rely on molecular stacking and interactions. Although the intrinsic nature of materials is primarily determined by single-molecule structures, molecular aggregation behavior that determines material property resembles the architectural style of a building in which the bricks themselves could be less important. While the establishment of surface-enhanced Raman spectroscopy (SERS) inspired numerous research interest for trace analysis up to single-molecule level, Raman spectroscopy is also recognized for its importance in solving several issues relating to molecule aggregates owing to the capability of non-destructive detection and spectral fingerprints by which chemical structures and aggregation states can be identified. Raman spectroscopy is not only applied to identify chemicals at the gas phase, liquid phase and solid state and to monitor in-situ reactions of materials at reduced sizes but also to probe gas-to-particle conversion in aerosols, microcrystal magnetization and phase transition at aggregated states, which are believed to attract uprising research interest in the near future

Ethyl {6-[6-(ethoxy­carbon­yl)picolin­amido­carbon­yl]picolinamido­carbon­yl}picolinate

The title mol­ecule, C25H21N5O8, adopts a helical conformation, which is stabilized by two intra­molecular bifurcated N—H⋯(N,N) hydrogen bonds

1-Phenyl-3-(pyren-1-yl)prop-2-en-1-one

The title compound, C25H16O, was prepared by the condens­ation reaction of pyrene-1-carbaldehyde and acetophenone in ethanol solution at room temperature. The phenyl ring forms a dihedral angle of 39.10 (11)° with the pyrene ring system. In the crystal structure, adjacent pyrene ring systems are linked by aromatic π–π stacking inter­actions, with a perpendicular inter­planar distance of 3.267 (6) Å and a centroid–centroid offset of 2.946 (7) Å

Tris[2-(pyrrol-2-ylmethyl­eneamino)eth­yl]amine

The title compound, C21H27N7, was synthesized by reaction of tris­(2-amino­ethyl)amine and pyrrole-2-carbaldehyde in ethanol at room temperature. The structure is stabilized by intra- and inter­molecular C—H⋯N and N—H⋯N hydrogen-bonding inter­actions

Revealing the Role of d Orbitals of Transition-Metal-Doped Titanium Oxide on High-Efficient Oxygen Reduction

Precise catalysis is critical for the high-quality catalysis industry. However, it remains challenging to fundamentally understand precise catalysis at the atomic orbital level. Herein, we propose a new strategy to unravel the role of specific d orbitals in catalysis. The oxygen reduction reaction (ORR) catalyzed by atomically dispersed Pt/Co-doped Ti$_{1−x}$O$_{2}$ nanosheets (Pt$_{1}$/Co$_{1}$–Ti$_{1−x}$O$_{2}$) is used as a model catalysis. The z-axis d orbitals of Pt/Co–Ti realms dominate the O$_{2}$ adsorption, thus triggering ORR. In light of orbital-resolved analysis, Pt$_{1}$/Co$_{1}$–Ti$_{1−x}$O$_{2}$ is experimentally fabricated, and the excellent ORR catalytic performance is further demonstrated. Further analysis reveals that the superior ORR performance of Pt$_{1}$–Ti$_{1−x}$O2 to Co$_{1}$–Ti$_{1−x}$O$_{2}$ is ascribed to stronger activation of Ti by Pt than Co via the d–d hybridization. Overall, this work provides a useful tool to understand the underlying catalytic mechanisms at the atomic orbital level and opens new opportunities for precise catalyst design

A room-temperature electrical-field-enhanced ultrafast switch in organic microcavity polariton condensates

Integrated electro-optical switches are essential as one of the fundamental elements in the development of modern optoelectronics. As an architecture for photonic systems, exciton polaritons, that are hybrid bosonic quasiparticles that possess unique properties derived from both excitons and photons, have shown much promise. For this system, we demonstrate a significant improvement of emitted intensity and condensation threshold by applying an electric field to a microcavity filled with an organic microbelt. Our theoretical investigations indicate that the electric field makes the excitons dipolar and induces an enhancement of the exciton-polariton interaction and of the polariton lifetime. Based on these electric field induced changes, a sub-nanosecond electrical-field-enhanced polariton condensate switch is realized at room temperature, providing the basis for developing an on-chip integrated photonic device in the strong light-matter coupling regime

Riemannian Surface on Carbon Anodes Enables Li-Ion Storage at −35 °C

Since sluggish Li$^{+}$ desolvation leads to severe capacity degradation of carbon anodes at subzero temperatures, it is urgently desired to modulate electron configurations of surface carbon atoms toward high capacity for Li-ion batteries. Herein, a carbon-based anode material (O-DF) was strategically synthesized to construct the Riemannian surface with a positive curvature, which exhibits a high reversible capacity of 624 mAh g$^{-1}$ with an 85.9% capacity retention at 0.1 A g$^{-1}$ as the temperature drops to −20 °C. Even if the temperature drops to −35 °C, the reversible capacity is still effectively retained at 160 mAh g$^{-1}$ after 200 cycles. Various characterizations and theoretical calculations reveal that the Riemannian surface effectively tunes the low-temperature sluggish Li$^{+}$ desolvation of the interfacial chemistry via locally accumulated charges of non-coplanar sp$^{x}$ (2 < x < 3) hybridized orbitals to reduce the rate-determining step of the energy barrier for the charge-transfer process. Ex-situ measurements further confirm that the sp$^{x}$-hybridized orbitals of the pentagonal defect sites should denote more negative charges to solvated Li$^{+}$ adsorbed on the Riemannian surface to form stronger Li–C coordinate bonds for Li$^{+}$ desolvation, which not only enhances Li-adsorption on the curved surface but also results in more Li$^{+}$ insertion in an extremely cold environment