Recent Applications of Molecular Structures at Silicon Anode Interfaces

Silicon (Si) is a promising anode material to realize many-fold higher anode capacity in next-generation lithium-ion batteries (LIBs). Si electrochemistry has strong dependence on the property of the Si interface, and therefore, Si surface engineering has attracted considerable research interest to address the challenges of Si electrodes such as dramatic volume changes and the high reactivity of Si surface. Molecular nanostructures, including metal–organic frameworks (MOFs), covalent–organic frameworks (COFs) and monolayers, have been employed in recent years to decorate or functionalize Si anode surfaces to improve their electrochemical performance. These materials have the advantages of facile preparation, nanoscale controllability and structural diversity, and thus could be utilized as versatile platforms for Si surface modification. This review aims to summarize the recent applications of MOFs, COFs and monolayers for Si anode development. The functionalities and common design strategies of these molecular structures are demonstrated.

TiO x /Pt3Ti(111) surface-directed formation of electronically responsive supramolecular assemblies of tungsten oxide clusters

Highly ordered titanium oxide films grown on a Pt3Ti(111) alloy surface were utilized for the controlled immobilization and tip-induced electric field-triggered electronic manipulation of nanoscopic W3O9 clusters. Depending on the operating conditions, two different stable oxide phases, z’-TiO x and w’-TiO x , were produced. These phases show a strong effect on the adsorption characteristics and reactivity of W3O9 clusters, which are formed as a result of thermal evaporation of WO3 powder on the complex TiO x /Pt3Ti(111) surfaces under ultra-high vacuum conditions. The physisorbed tritungsten nano-oxides were found as isolated single units located on the metallic attraction points or as supramolecular self-assemblies with a W3O9-capped hexagonal scaffold of W3O9 units. By applying scanning tunneling microscopy to the W3O9–(W3O9)6 structures, individual units underwent a tip-induced reduction to W3O8. At elevated temperatures, agglomeration and growth of large WO3 islands, which thickness is strongly limited to a maximum of two unit cells, were observed. The findings boost progress toward template-directed nucleation, growth, networking, and charge state manipulation of functional molecular nanostructures on surfaces using operando techniques.

Directing on-surface polymerization via substrate-directed molecular template

Using template to control on-surface polymerization process is valuable for building functional molecular nanostructures. Here, the role of the symmetric matching between a halogen-ligand component (H2TBrPP) and substrate on the...

Temperature-Programmed Desorption of Large Molecules: Influence of Thin Film Structure and Origin of Intermolecular Repulsion

Although the exact knowledge of the binding energy of organic adsorbates on solid surfaces is of vital importance for the realization of molecular nanostructures and the theoretical modelling of molecule-substrate...

Development of Perylene-Based Non-Fullerene Acceptors through Bay-Functionalization Strategy

Perylene has had a tremendous impact in the history of material research for the molecular semiconductors. Among numerous derivatives of this polyaromatic hydrocarbon, perylene diimide (PDI) represents a promising class of organic materials envisioned as non-fullerene acceptors (NFAs) for the practical organic photovoltaic (OPV) applications due to their enhanced photo- and thermal stability and remarkably high electron affinity, some of which realize band-like transport properties. The present review guides some of the representative achievements in the development of rationally designed PDI systems, highlighting synthetic methodologies based on bay-functionalization strategies for creating well-designed molecular nanostructures and structure-performance relationship of perylene-based small molecular acceptors (SMAs) for the photovoltaic outcomes.

Molecular self-assembly of porphyrin and BODIPY chromophores connected with diphenylalanine moieties

In this study, a series of diphenylalanine tetra-substituted porphyrin derivatives were synthesized and their self-assembly ability was extensively studied. Apart from investigating the impact of incorporating many peptide moieties onto a porphyrin molecule; another perspective was investigated as well, namely the connection of two different chromophore entities (porphyrin and BODIPY) onto the same diphenylalanine molecule. Interestingly, various supra-molecular nanostructures were observed depending on the solvent mixture as well as the protecting group of the peptides, namely spheres, plaques and fibrils. The obtained self-assemblies were studied via UV-vis absorption and emission spectroscopies. Mainly red shifting was observed, indicating the formation of [Formula: see text]-aggregates in the self-assembled state. However, in one case a blue shifted UV-vis spectrum was obtained suggesting the formation of [Formula: see text]-type aggregates. Concerning the porphyrin-diphenylalanine-BODIPY derivative, additional fluorescence studies were performed in order to examine a possible interaction between the two chromophores in the excited state. Indeed, the emission measurements indicated that upon photo-excitation of the BODIPY entity, a very efficient energy or electron transfer process takes place from the BODIPY molecule to the porphyrin macrocycle.