On-Surface Self-Assembly Kinetic Study of Cu-Hexaazatriphenylene 2D Conjugated Metal-Organic Frameworks on Coinage Metals and MoS Substrates.

Supramolecular coordination self-assembly on solid surfaces provides an effective route to form two-dimensional (2D) metal-organic frameworks (MOFs). In such processes, surface-adsorbate interaction plays a key role in determining the MOFs' structural and chemical properties. Here, we conduct a systematic study of Cu-HAT (HAT = 1,4,5,8,9,12-hexaazatriphenylene) 2D conjugated MOFs (-MOFs) self-assembled on Cu(111), Au(111), Ag(111), and MoS substrates.

A p-orbital honeycomb-Kagome lattice realized in a two-dimensional metal-organic framework.

The experimental realization of p-orbital systems is desirable because p-orbital lattices have been proposed theoretically to host strongly correlated electrons that exhibit exotic quantum phases. Here, we synthesize a two-dimensional Fe-coordinated bimolecular metal-organic framework which constitutes a honeycomb lattice of 1,4,5,8,9,12-hexaazatriphenylene molecules and a Kagome lattice of 5,15-di(4-pyridyl)-10,20-diphenylporphyrin molecules on a Au(111) substrate. Density-functional theory calculations show that the framework features multiple well-separated spin-polarized Kagome bands, namely Dirac cone bands and Chern flat bands, near the Fermi level.

On-surface synthesis and spontaneous segregation of conjugated tetraphenylethylene macrocycles.

Creating conjugated macrocycles has attracted extensive research interest because their unique chemical and physical properties, such as conformational flexibility, intrinsic inner cavities and aromaticity/antiaromaticity, make these systems appealing building blocks for functional supramolecular materials. Here, we report the synthesis of four-, six- and eight-membered tetraphenylethylene (TPE)-based macrocycles on Ag(111) via on-surface Ullmann coupling reactions. The as-synthesized macrocycles are spontaneously segregated on the surface and self-assemble as large-area two-dimensional mono-component supramolecular crystals, as characterized by scanning tunneling microscopy (STM).

Synthesis of Single-Layer Two-Dimensional Metal-Organic Frameworks M (HAT) (M=Ni, Fe, Co, HAT=1,4,5,8,9,12-hexaazatriphenylene) Using an On-Surface Reaction.

1,4,5,8,9,12-Hexaazatriphenylene (HAT) is one of the smallest polyheterocyclic aromatic building blocks for forming conjugated metal-organic frameworks (cMOFs). However, the strong inter-molecular steric hindrance impedes the growth of HAT-based cMOFs. Here we employ on-surface synthesis to grow single-layer two-dimensional cMOFs of M (HAT) (M=Ni, Fe, Co).

Stress-induced optical waveguides written by an ultrafast laser in Nd, Y co-doped SrF crystals.

In this paper, we report on the ultrafast laser-induced birefringence, refractive index changes, and enhanced photoluminescence properties in the volume of neodymium (Nd), yttrium (Y) co-doped strontium fluoride (SrF) and Nd, Y co-doped calcium fluoride (CaF) crystals. The optical waveguides written with 500 kHz repetition rate provided lowest propagation loss of 1.63±0.

Functionalized Graphene Oxide Enables a High-Performance Bulk Heterojunction Organic Solar Cell with a Thick Active Layer.

Novel functionalized graphene oxide π-π stacking with conjugated polymers (P-GO) is fabricated via a simple ethanol-mediated mixing method, leading to better dispersion in organic nonpolar solvents and bypassing the inherent restrictions of hydrophilicity and oleophobicity. We analyze the mechanism of the incorporation of P-GO into inverted organic solar cells (OSCs) based on a poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4- b]thiophenediyl]] (PTB7):[6,6]-phenyl C butyric acid methyl ester (PCBM) system to investigate the possibility of high-performance thick-film OSC fabrication. It is verified that the incorporation of P-GO into the PTB7:PCBM blend films leads to a decreased π-π stacking distance, enlarged coherence length for polymer, and optimized phase separation, resulting in more effective charge dissociation, reduced bimolecular recombination, and more balanced charge transport.