Surface‐Anchored MOF‐Based Photonic Antennae

The loading of a metal‐organic framework (MOF), [Cu₃(btc)₂xH₂O] HKUST‐1, with europium β‐diketonate complexes is studied with the goal to using the porous molecular framework as a photonic antenna. Whereas loading of HKUST‐1 powder particles produced via the conventional solvothermal synthesis method was strongly hindered, for HKUST‐1 SURMOFs, thin MOF films fabricated using the liquid phase epitaxy method, a high filling factor can be achieved. The optical properties of the HKUST‐1‐MOFs before and after loading were analysed with the aid of luminescence spectroscopy. Careful analysis of the absorption spectra reveals the presence of an effective energy transfer between the HKUST‐1 framework and the Eu³⁺ centers.     

Surface‐Tension‐Confined Microfluidics and Their Applications

This article is a brief overview of the emerging microfluidic systems called surface‐tension‐confined microfluidic (STCM) devices. STCM devices utilize surface energy that can control the movement of fluid droplets. Unlike conventional poly(dimethylsiloxane)‐based microfluidics which confine the movement of fluids by three‐dimensional (3D) microchannels, STCM systems provide two‐dimensional (2D) platforms for microfluidics. A variety of STCM devices have been prepared by various micro‐/nanofabrication strategies. Advantages of STCM devices over conventional microfluidics are significant reduction of energy consumption during device operation, facile introduction of fluids onto 2D microchannels without the use of a micropump, increased flow rate in a special type of STCM device, among others. Thus, STCM devices can be excellent alternatives for certain areas in microfluidics. In this Minireview, fabrication methods, operating modes, and applications of STCM devices are introduced.     

Core‐and‐Surface‐Functionalized Polyphenylene Dendrimers for Solution‐Processed,Pure‐Blue Light‐Emitting Diodes Through Surface‐to‐Core Energy Transfer

Several pyrene‐based polyphenylene dendrimers (PYPPDs) with different peripheral chromophores (PCs) are synthesized and characterized. Deep blue emissions solely from the core are observed for all of them in photoluminescence spectra due to good steric shielding of the core and highly efficient surface‐to‐core Förster resonant energy transfers (FRETs). Device performances are found in good correlation with the energy gaps between the work function of the electrodes and the frontier molecular orbital (FMO) levels of the PCs. Pure blue emission, luminance as high as 3700 cd m⁻² with Commission Internationale de l'Éclairage 1931 (CIE_xy) = (0.16, 0.21), and a peak current efficiency of 0.52 cd A⁻¹ at CIE_xy = (0.17, 0.20) are achieved. These dendrimers are among the best dendritic systems so far for fluorescent blue light‐emitting materials.

     

Surface‐Assisted Large‐Scale Ordering of DNA Origami Tiles

The arrangement of DNA‐based nanostructures into extended higher order assemblies is an important step towards their utilization as functional molecular materials. We herein demonstrate that by electrostatically controlling the adhesion and mobility of DNA origami structures on mica surfaces by the simple addition of monovalent cations, large ordered 2D arrays of origami tiles can be generated. The lattices can be formed either by close‐packing of symmetric, non‐interacting DNA origami structures, or by utilizing blunt‐end stacking interactions between the origami units. The resulting crystalline lattices can be readily utilized as templates for the ordered arrangement of proteins.     

A Theoretical Investigation of Surface‐enhanced Sum‐frequency Generation

Following the surface enhanced Raman scattering (SERS), we shall investigate the possibility of observing surface‐enhanced sum‐frequency generation (SESFG), which refers to the transformation of ordinary vibrational SFG (i.e. singly resonant) into SESFG. Two mechanisms of SESFG will be studied; one is due to the transformation of singly‐resonant vibrational SFG into doubly resonant vibrational SFG (that is, both vibrationally resonant and Raman‐scattering resonant) and the other is due to the enhancement of the polarizability in addition to the original vibrational resonance in vibrational SFG.     

Surface‐Assisted Self‐Assembly Strategies Leading to Supramolecular Hydrogels

Localized molecular self‐assembly processes leading to the growth of nanostructures exclusively from the surface of a material is one of the great challenges in surface chemistry. In the last decade, several works have been reported on the ability of modified or unmodified surfaces to manage the self‐assembly of low‐molecular‐weight hydrogelators (LMWH) resulting in localized supramolecular hydrogel coatings mainly based on nanofiber architectures. This Minireview highlights all strategies that have emerged recently to initiate and localize LMWH supramolecular hydrogel formation, their related fundamental issues and applications.     

Noble‐Metal‐Free Materials for Surface‐Enhanced Raman Spectroscopy Detection

Surface‐enhanced Raman spectroscopy (SERS) is an attractive tool for the sensing of molecules in the fields of chemical and biochemical analysis as it enables the sensitive detection of molecular fingerprint information even at the single‐molecule level. In addition to traditional coinage metals in SERS analysis, recent research on noble‐metal‐free materials has also yielded highly sensitive SERS activity. This Minireview presents the recent development of noble‐metal‐free materials as SERS substrates and their potential applications, especially semiconductors and emerging graphene‐based nanostructures. Rather than providing an exhaustive review of this field, possible contributions from semiconductor substrates, characteristics of graphene enhanced Raman scattering, as well as effect factors such as surface plasmon resonance, structure and defects of the nanostructures that are considered essential for SERS activity are emphasized. The intention is to illustrate, through these examples, that the promise of noble‐metal‐free materials for enhancing detection sensitivity can further fuel the development of SERS‐related applications.     

Surface‐Guided Formation of an Organocobalt Complex

Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson–Khand, Friedel–Crafts, and Nicholas reactions. Herein, a single‐molecule‐level investigation addressing the formation of an organocobalt complex at a solid–vacuum interface is reported. Deposition of 4,4′‐(ethyne‐1,2‐diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X‐ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar–Chatt–Duncanson model for a two‐electron‐donor ligand where an alkyne‐to‐Co donation occurs together with a strong metal‐to‐alkyne back‐donation.     

Surface‐Electron Coupling for Efficient Hydrogen Evolution

Maximizing the activity of materials towards the alkaline hydrogen evolution reaction while maintaining their structural stability under realistic working conditions remains an area of active research. Herein, we report the first controllable surface modification of graphene(G)/V₈C₇ heterostructures by nitrogen. Because the introduced N atoms couple electronically with V atoms, the V sites can reduce the energy barrier for water adsorption and dissociation. Investigation of the multi‐regional synergistic catalysis on N‐modified G/V₈C₇ by experimental observations and density‐functional‐theory calculations reveals that the increase of electron density on the epitaxial graphene enable it to become favorable for H* adsorption and the subsequent reaction with another H₂O molecule. This work extends the range of surface‐engineering approaches to optimize the intrinsic properties of materials and could be generalized to the surface modification of other transition‐metal carbides.