Surface Science Reports最新文献

The formation of chiral nanostructures via molecular assembly and reaction on solid surfaces is a ubiquitous surface process due to the symmetry-breaking at 2D surface. Studying chirality during the adsorption, assembly, and reaction of molecules on 2D solid surfaces at molecular level not only sheds deep insights into the enantioselective heterogeneous catalysis, chiral recognition, origin and evolution of chirality, and many important physical chemistry processes but also provides an important strategy to create chiral nanostructures. Here, we give a survey of recent advances in chiral expression and control in molecular assemblies and reactions on surfaces. We firstly give a brief introduction to the general concepts of chiral molecular nanostructures on surfaces. And then we focus on the induction and control of chirality expressed in molecular assemblies. The recent developments in the control strategies such as chiral co-adsorber, chiral auxiliary, chiral solvent, chiral templated surfaces, as well as the underlying mechanism to achieve the chiral induction and amplification, are reviewed. After that, we review the studies of chirality expressed in on-surface synthesis which has been proved to be a promising strategy to fabricate covalently bonded low-dimensional nanostructures and materials. In this respect, we introduce the chiral expression in the intramolecular and intermolecular coupling reactions on surfaces. In addition, we survey the methods to steer the stereoselectivity of on-surface reactions including the design of precursor structure, steric hindrance effect, substrate, kinetic parameters et al. Finally, the future outlook in this field is discussed.

Fundamental mechanisms for energy conversion and dissipation on surfaces and at interfaces have been significant issues in the community of surface science. Electronic excitation in exothermic chemical reactions or photon absorption involves the generation of energetic or hot electrons that are not in thermal equilibrium via non-adiabatic electronic excitation. A number of experimental and theoretical studies have demonstrated the influence of excited hot electrons on atomic and molecular processes, and it is a key moderator in the surface energy conversion process. The charge transfer through the metal-oxide interfaces has a significant impact on catalytic performance in mixed metal-oxide catalysts. In order to understand the influence of hot electrons and metal-oxide interfaces on the surface reactions, various detection schemes of exoelectron detection, including metal-insulator-metal and metal-semiconductor Schottky diodes, have been developed. Catalysts coupled with surface plasmons exhibit peculiar catalytic performance related to hot electron flow. In this review, we outline recent research efforts to relate hot electron flow with surface reactions occurring at metal-oxide interfaces. We report recent studies on the observation of hot electrons and the correlation between hot electrons and catalytic activity and selectivity on metallic surfaces. We show recent results from studies of surface reactions on nanocatalysts coupled with surface plasmons, where hot electron transport is the key process in energy dissipation and conversion processes.

The direct epoxidation of propylene to propylene oxide (PO) using molecular oxygen is an attractive alternative to current production methods using chlorohydrin or hydroperoxide-mediated processes, which are environmentally harmful and expensive. Although direct ethylene epoxidation using Ag-based catalysts has been practiced industrially for decades, due to the presence of allylic hydrogen in propylene the selectivity toward epoxide is generally much lower for propylene than for ethylene. Mechanistic understanding on well-characterized surfaces of model catalysts can potentially provide guidance to effectively alter the electronic properties of the catalyst in order to increase PO selectivity. This review summarizes both experimental and theoretical studies on model catalysts for propylene epoxidation and their contributions to elucidating the reaction mechanism, intermediates, and active sites. We first show examples of experimental studies on Cu, Ag, and Au surfaces, and compare the reaction pathways and intermediates on these surfaces. Novel approaches including plasmon-mediated catalysis and utilization of shape-controlled crystal facets that open new opportunities for improving PO selectivity will also be discussed. We then describe how density functional theory (DFT) calculations have provided important insights into the reaction mechanism and active sites on Cu, Ag, and Au surfaces and clusters. Propylene oxidation pathways on other relevant metal surfaces will also be discussed. The combined experimental and computational studies elucidate the nature of surface oxygen species and the role of the oxametallacycle intermediate. We conclude by highlighting design principles and insights for guiding further development of active and selective propylene epoxidation catalysts.

Among fundamental diatomic molecules, the adsorption of carbon monoxide (CO) and nitric oxide (NO) on metal surfaces has been a subject of intensive research in the surface science community, partly owing to its relevance to heterogeneous catalysis used for environmental control. Compared to the rather well-defined adsorption mechanism of CO, that of NO is less understood because the adsorption results in much more complex reactions. The complexity is ascribed to the open-shell structure of valence electrons, making the molecule readily interact with the metal surface itself as well as with co-adsorbed molecules. Furthermore, the interaction crucially depends on the local structure of the surface. Therefore, to elucidate the interaction at the molecular scale, it is essential to study the valence state as well as the bonding geometry for individual NO molecules placed in a well-defined environment on the surface. Scanning tunneling microscopy (STM) is suitable for this purpose. In this review, we summarize the knowledge about the interaction of NO with metal surfaces, mainly focused on the valence electronic states, followed by recent studies using STM and atomic force microscopy (AFM) at the level of individual molecules.

It was a long-cherished dream for chemists to take a direct look at chemical bonding, a fundamental component of chemistry. This dream was finally accomplished by the state-of-the-art noncontact atomic force microscopy (NC-AFM) equipped with qPlus force sensors and carbon monoxide (CO) functionalized tips. The resolved interconnectivity between atoms and molecules in NC-AFM frequency shift images is interpreted as chemical bonding, providing essential knowledge of the bond length, bond angle and even bond order. The featured contrast of different chemical bonds can serve as fingerprints for further interpretation of chemical structures toward unknown species synthesized on surfaces. This breakthrough enriches characterization tools for surface science and brings our understanding of on-surface reactions to a new level. Beyond bond imaging, the application of NC-AFM has been extended to quantifying interatomic interactions, identifying three-dimensional nanostructures, manipulating molecules and reactions, as well as determining molecular electronic characteristics. Moreover, some recent efforts address the improvement of the usability and versatility of the bond-resolved NC-AFM technique, including high-resolution molecular investigation on bulk insulators, application-specific tip modification, stable bond imaging above liquid helium temperature and autonomous experimentation implemented by artificial intelligence.

Infrared (IR) spectroscopy has evolved into a powerful analytical technique to probe molecular and lattice vibrations, low-energy electronic excitations and correlations, and related collective surface plasmon, phonon, or other polaritonic resonances. In combination with scanning probe microscopy, near-field infrared nano-spectroscopy and -imaging techniques have recently emerged as a frontier in imaging science, enabling the study of complex heterogeneous materials with simultaneous nanoscale spatial resolution and chemical and quantum state spectroscopic specificity. Here, we describe synchrotron infrared nano-spectroscopy (SINS), which takes advantage of the low-noise, broadband, high spectral irradiance, and coherence of synchrotron infrared radiation for near-field infrared measurements across the mid- to far-infrared with nanometer spatial resolution. This powerful combination provides a qualitatively new form of broadband spatio-spectral analysis of nanoscale, mesoscale, and surface phenomena that were previously difficult to study with IR techniques, or even any form of micro-spectroscopy in general. We review the development of SINS, describe its technical implementations, and highlight selected examples representative of the rapidly growing range of applications in physics, chemistry, biology, materials science, geology, and atmospheric and space sciences.

Many far-reaching applications of graphene require a deep understanding of the interactions between graphene and other surfaces, including the wetting behaviour of graphene. However, its two-dimensional nature does not allow qualifying graphene as simply hydrophobic or hydrophilic, but instead gives rise to a diversity of interfacial phenomena governing the apparent wettability of graphene. As a result, wide disparities in the wetting properties of graphene have been widely reported. In this review we analyse the wettability of graphene with a special focus on the experimental conditions and on discriminating the causes of the reported inconsistencies. The elimination of the environmental factors causing misleading data is a major challenge. Importantly, progresses made in graphene research yielded new experimental insights and tools enabling the minimization of unwanted effects and, ultimately, the achievement of reliable contact angle measurements. Besides the macroscopic wettability studied using contact angle measurements under ambient conditions or by theoretical modelling, we also analysed correlations with the wettability of graphene at the molecular level in supremely pure environment of ultra-high vacuum.

First-principles predictions play an important role in understanding chemistry at the electrochemical interface. Electronic structure calculations are straightforward for vacuum interfaces, but do not easily account for the interfacial fields and solvation that fundamentally change the nature of electrochemical reactions. Prevalent techniques for first-principles prediction of electrochemical processes range from expensive explicit solvation using ab initio molecular dynamics, through a hierarchy of continuum solvation techniques, to neglecting solvation and interfacial field effects entirely. Currently, no single approach reliably captures all relevant effects of the electrochemical double layer in first-principles calculations.

This review systematically lays out the relation between all major approaches to first-principles electrochemistry, including the key approximations and their consequences for accuracy and computational cost. Focusing on ab initio methods for thermodynamic properties of aqueous interfaces, we first outline general considerations for modeling electrochemical interfaces, including solvent and electrolyte dynamics and electrification. We then present the specifics of various explicit and implicit models of the solvent and electrolyte. Finally, we discuss the compromise between computational efficiency and accuracy, and identify key outstanding challenges and future opportunities in the wide range of techniques for first-principles electrochemistry.

The establishment of electronic and opto-electronic products relying on organic semiconductors (OSCs) has been intensely explored over the past few decades due to their great competitiveness in large area, low cost, flexible, wearable and implantable devices. Many of these products already entered our daily lives, such as organic light-emitting diodes-based displays, portable organic solar cells and organic field-effect transistors. The device performance of OSC devices are determined by the supramolecular organization (orientation, morphology) as well as the supramolecular organization dependent energy level alignment at various interfaces (organic/electrode, organic/dielectric, organic/organic). This review focuses on the impact of non-covalent interaction on the molecular self-assembly of organic thin films, their electronic and optical properties, as well as the device performance. Beginning with the growth of multiple OSCs on substrates with different interfacial interaction strengths (metals, insulators, semiconductors), the critical roles of molecule-substrate and intermolecular interactions in determining the thin film organization have been demonstrated. Several non-covalent interactions that contribute to the energy levels of organic materials in solid phase are summarized, mainly including the induction contributions, electrostatic interactions, band dispersions and interface dipoles. The excitonic coupling in specific aggregations of organic molecules and the corresponded effect on their optical properties are also discussed. Finally, the influences of weak intermolecular interactions on the device performance are presented.