Hierarchical Self-assembly of Ag-coordinated Motifs on Ag(111)

Abstract

Metal-organic nanostructures on surfaces have attracted considerable attention owing to their structural stability and potential applications. In metal-organic nanostructures, metal atoms are derived from the externally deposited metals or native surface atoms. Externally deposited metals are of rich diversity and depend on the targeted nanostructures. However, native surface atoms are restricted to single-crystalline metal surfaces of gold, silver, and copper, which are usually used in surface science. Metal-organic nanostructures mostly consist of Au-or Cu-coordinated motifs, while only a few consist of surface Ag atoms. Further investigation into the molecule-metal interactions is beneficial for the accurately controlled fabrication of the desired nanostructure. As for the building blocks, organic molecules coordinate with native surface atoms by M-C, M-N, and M-O bonds. The reactions of terminal alkynes or Ullmann couplings could realize the formation of C-M-C linkages. Cu and Au atoms could coordinate with molecules with terminal cyano or pyridyl groups to form N-M-N bonds. In addition, surface Ag adatoms could coordinate with phthalocyanine through Ag-N bonds. However, a comprehensive study of M-O coordination bonds is still lacking. Thus, we used hydroxyl-terminated molecules to coordinate with Ag adatoms to form metal-organic coordination nanostructures and study the O-Ag linkages. In this case, we successfully built and investigated a series of ordered structures by depositing 4,4'-dihydroxy-1,1':3',1''-terphenyl (H3PH) molecules on the Ag(111) surface by scanning tunneling microscopy. At room temperature, a close-packed ordered structure was formed by H3PH molecules through cyclic hydrogen bonds, and the repeat unit of such nanostructures contained eight H3PH molecules. Upon increasing the annealing temperature, the formation of O-Ag bond led to a change in the self-assembly pattern. When the annealing temperature was increased to 330 K, a new ordered nanostructure occurred due to the combination of O-Ag coordination and hydrogen bonds. Upon further increasing the annealing temperature to 420 K, a honeycomb structure and coexisting two-fold coordination chains appeared, which only consisted of O-Ag-O linkages. Density functional theory calculations were carried out to analyze the metal-molecule reaction pathways and energy barriers of the O-Ag-O bonds. The energy barrier of the O-Ag bond is 1.41 eV, which is less than that of the O-Ag-O linkage calculated to be 1.85 eV. The low energy barrier of the O-Ag bond and large coordination energy of the O-Ag-O linkage can be attributed to the formation of the hierarchical metal-organic nanostructure.The results obtained herein provide an effective approach for designing and building two-dimensional hierarchical structures with organic small molecules and metal adatoms on single-crystalline metal surfaces.

Chemical Way to Tune Spin Excitation of Magnetic Atoms in Sierpiński Triangles

“…After annealing at 80 °C for 10 min, the samples are cooled to 4 K in 30 min, and three kinds of STs are obtained, as shown in Figure b–d, respectively. In the coordination process, the hydroxyl groups are deprotonated. ,, Although the STM topographic images of them look similar, the difference in the functional groups may lead to disparate physicochemical properties. Every ST displayed in Figure includes 42 organic molecules and 27 Fe atoms, and the coordination number of each Fe atom is 3.…”

Peroxidase-like MoS2/Ag nanosheets with synergistically enhanced NIR-responsive antibacterial activities

“…By accelerating the movement of electrons, the combination of precious metals with semiconductor materials can considerably enhance the photodynamic characteristics of semiconductor materials ( Xia et al, 2015 ; Raza et al, 2017 ). The superior conductivity and inherent antibacterial properties of Ag make it a suitable precious metal material ( Li et al, 2022b ). More importantly, the Ag also have the effect of surface plasmon resonance, which allows electrons to escape from the outermost surface and be captured by the surrounding oxygen to produce ROS ( Zhu et al, 2020 ).…”

Tuning Surface Organic Structures by Small Gas Molecules through Catassembly and Coassembly

“…Leveraging the principles of molecular self-assembly, a diverse array of materials has surfaced across various domains such as materials science, nanotechnology, and biomedicine, highlighting the versatility and potential of this approach. − Emerging applications include molecular electronics, , surface functionalization, biocatalysts, , etc. In general, the fabrication of assembly structures relies primarily on how we harness the relatively weak interactions such as π–π stacking, van der Waals forces, hydrogen bond, coordination bond, , and electrostatic interactions …”

“…1−3 Emerging applications include molecular electronics, 4,5 surface functionalization, 6 biocatalysts, 7,8 etc. In general, the fabrication of assembly structures relies primarily on how we harness the relatively weak interactions such as π−π stacking, 9 van der Waals forces, 10 hydrogen bond, 11 coordination bond, 12,13 and electrostatic interactions. 14 Molecular assembly processes usually involve complex thermodynamics and dynamics and thus require exquisite regulation of their growth conditions.…”