Coordination-Controlled One-Dimensional Molecular Chains in Hexapodal Adenine-Silver Ultrathin Films

On-Surface Synthesis of Novel Kagome Lattices Coordinated via Four-Fold N-Ag Bonding

The Kagome lattice structures based on metal-organic coordination have garnered widespread interest because of their topologically Dirac/flat bands and other exotic electronic structures. However, the experimental fabrication of large-area two-dimensional (2D) Kagome lattice structures of metal-organic frameworks (MOFs) via on-surface synthesis remains limited. Herein, we successfully construct two kinds of large-scale 2D Kagome-type lattices stabilized by 4-fold N-Ag coordination on the Ag(111) surface. With the aid of scanning tunneling microscopy (STM) and synchrotron radiation photoemission spectroscopy (SRPES), we clearly elucidate the reaction pathway and mechanism of fabrication of the two Kagome lattices. This work provides a novel platform for investigating related intriguing physical properties.

In-situ generation of nanozymes by natural nucleotides: a biocatalytic label for quantitative determination of hydrogen peroxide and glucose

Four natural nucleotides including 5'-cytidine monophosphate (CMP), 5'-thymidine monophosphate (TMP), guanosine monophosphate (GMP) and 5'-adenosine monophosphate (AMP) were employed to modulate the coordination environment and the valence state of PtCl₄^2-. This is the first report that natural nucleotides have the ability to produce highly active Pt nanoclusters. The latter are shown to act as peroxidase mimetics. Both the size distribution and the charge state of Pt-nucleotide nanozymes vary with the chemical structures of nucleotides, thereby contributing to distinct enzyme-like activities. By adopting Pt-CMP as a signal amplifier, a photometric assay was well-established for quantitative determination of glucose. The assay is based on the oxidation of glucose by glucose oxidase. The oxidation product (H₂O₂) is detected at 652 nm via the Pt-CMP-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine with H₂O₂. Response is linear in the 5 to 100 μM glucose concentration range, and the limit of detection is 0.12 μM (at S/N= 3). The method excels by a low signal background, high sensitivity, and low consumption of energy and materials. Graphical abstract Peroxidase mimicking Pt nanoclusters were synthesized by employing natural nucleotides as both the reducing agent and the stabilization template.

Exfoliating a CdII -Purine Framework: Conversion of Nanosheets-to-Nanofibers and Studies of Elastic and Capacitive Properties

Layered bulk crystals are amenable to exfoliation to yield 2D nanosheets through isolation and intercalation processes, which could be further converted to 1D nanoscale structures. The latter inherit gross morphological and physical properties associated with the precursor structures. Herein, we report three purine-based crystal structures 1, 2, and 3, where 3 is obtained by a single-crystal-to-single-crystal transformation from 2 and is a conformational polymorph of 1. Next, we describe the sonication-assisted liquid exfoliation of 1, a Cd^II -purine coordination framework, into nanosheets and nanofibers in a solvent-dependent process. The exfoliation was carefully studied at low temperatures to ascertain this unique conversion. This work also features the determination of the Young's modulus and surface potential of the bioinspired Cd^II -based nanostructures by using amplitude modulation-frequency modulation atomic force microscopy and Kelvin probe force microscopy, respectively, revealing their interesting elastic and capacitive properties for their possible use in electronics and energy devices. Electron impedance spectroscopy measurements further established a higher value of capacitance for the exfoliated Cd^II framework as compared to the ligand alone.

Surface modification and pattern formation by nucleobases and their coordination complexes

This review presents recent progress concerning the organization of nucleobases on highly ordered pyrolytic graphite (HOPG), mica, Cu(110) and Au(111) surfaces, followed by their studies using microscopy methods such as atomic force microscopy (AFM), scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). Interesting research prospects related to surface patterning by nucleobases, nucleobase-functionalized carbon nanotubes (CNTs) and metal–nucleobase coordination polymers are also discussed, which offer a wide array of functional molecules for advanced applications. Nucleobases and their analogs are able to invoke non-covalent interactions such as π–π stacking and hydrogen bonding, and possess the required framework to coordinate metal ions, giving rise to fascinating supramolecular architectures. The latter could be transferred to conductive substrates, such as HOPG and gold, for assessment by high-end tunneling microscopy under various conditions. Clear understanding of the principles governing nucleobase self-assembly and metal ion complexation, and precise control over generation of functional architectures, might lead to custom assemblies for targeted nanotechnological and nanomaterial applications.

This review highlights recent advancements in surface patterning of nucleobases, their analogs including nucleobase-CNT hybrids and metal complexes, using various microscopy techniques for nanotechnological applications.