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The interfacial stability is highly responsible for the longevity and safety of sodium ion batteries (SIBs). However, the continuous solid-electrolyte interphase(SEI) growth would deteriorate its stability. Essentially, the SEI growth is associated with the electron leakage behavior, yet few efforts have tried to suppress the SEI growth, from the perspective of mitigating electron leakage. Herein, we built two kinds of SEI layers with distinct growth behaviors, via the additive strategy. The SEI physicochemical features (morphology and componential information) and SEI electronic properties (LUMO level, band gap, electron work function) were investigated elaborately. Experimental and calculational analyses showed that, the SEI layer with suppressed growth delivers both the low electron driving force and the high electron insulation ability. Thus, the electron leakage is mitigated, which restrains the continuous SEI growth, and favors the interface stability with enhanced electrochemical performance.

Chalcogen elements, such as sulfur (S), selenium (Se), tellurium (Te) and the interchalcogen compounds, have been studied extensively as cathode materials for the next-generation rechargeable lithium/sodium (Li/Na) batteries. The high energy output of the Li/Na-chalcogen battery originates from the two-electron conversion reaction between chalcogen cathode and alkali metal anode, through which both electrodes are able to deliver high theoretical capacities. The reaction also leads to parasitic reactions that deteriorate the chemical environment in the battery, and different cathode-anode combinations show their own features. In this article, we intend to discuss the fundamental conversion electrochemistry between chalcogen elements and alkali metals and its potential influence, either positive or negative, on the performance of batteries. The strategies to improve the conversion electrochemistry of chalcogen cathode are also reviewed to offer insights into the reasonable design of rechargeable Li/Na-chalcogen batteries.

We report a molecular investigation of a cobalt phthalocyanine (CoPc)-catalyzed CO2 reduction reaction by electrochemical scanning tunneling microscopy (ECSTM). An ordered adlayer of CoPc was prepared on Au(111). Approximately 14 % of the adsorbed species appeared with high contrast in a CO2 -purged electrolyte environment. The ECSTM experiments indicate the proportion of high-contrast species correlated with the reduction of CoII Pc (-0.2 V vs. saturated calomel electrode (SCE)). The high-contrast species is ascribed to the CoPc-CO2 complex, which is further confirmed by theoretical simulation. The sharp contrast change from CoPc-CO2 to CoPc is revealed by in situ ECSTM characterization of the reaction. Potential step experiments provide dynamic information for the initial stage of the reaction, which include the reduction of CoPc and the binding of CO2 , and the latter is the rate-limiting step. The rate constant of the formation and dissociation of CoPc-CO2 is estimated on the basis of the in situ ECSTM experiment.

Molybdenum disulfide is considered one of the most promising anodes for lithium-ion batteries due to its high specific capacity; however, it suffers from an unstable solid electrolyte interphase. Understanding its structural evolution and reaction mechanism upon charging/discharging is crucial for further improvements in battery performance. Herein, the interfacial processes of solid electrolyte interphase film formation and lithiation/delithiation on ultra-flat monolayer molybdenum disulfide are monitored by in situ atomic force microscopy. The live formation of ultra-thin and dense films can be induced by the use of fluoroethylene carbonate as an additive to effectively protect the anode electrodes. The evolution of the fluoroethylene carbonate-derived solid electrolyte interphase film upon cycling is quantitatively analysed. Furthermore, the formation of wrinkle-structure networks upon lithiation process is distinguished in detailed steps, and accordingly, structure-reactivity correlations are proposed. These quantitative results provide an in-depth understanding of the interfacial mechanism in molybdenum disulfide-based lithium-ion batteries., MoS2 is a highly promising anode material for lithium ion batteries. Here, aided by atomic force microscopy, the authors reveal the formation of an ultra-thin solid electrolyte interphase between MoS2 and electrolyte, providing fresh insight into the structural evolution and reaction mechanism at the interface.

Three types of well-ordered covalent two-dimensional tilings including triangular, rhombille and semi-regular Archimedean tilings were successfully constructed via on-surface Schiff base reaction. Among them, the covalent organic framework (COF) constructed from a C6 symmetry monomer and C3 symmetry monomer is the first reported COF with kgd (rhombille tiling) topology.

We report on the two-dimensional self-assembly of C2v-symmetric [1,1′:3′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid (TPTA) at the solid/liquid interface by using scanning tunneling microscopy (STM). Two kinds of different self-assembly structure, i.e. a close-packed and porous rosette structure, are formed by TPTA molecules through intermolecular hydrogen bonds. When adding coronene (COR) as a guest into the TPTA assembly, structural transformation from a densely packed row structure to a rosette network structure is observed. It was found that two kinds of cavities with different sizes in the rosette network structure can be used to realize the selective co-adsorption of guest molecules with appropriate shape and size. Three-component 2D host–guest structures were successfully constructed by using 1,2,3,4,5,6-hexakis(4-bromophenyl)benzene (HBPBE) and copper phthalocyanine (CuPc) as guest molecules.

Here we show a conceptual approach to realize the scanning tunneling microscopy based induced-assembly of fullerene (C60) molecules on top of a buffer organic adlayer at room temperature in a solution environment. The realization of spatially-defined C60 assembly is attributed to the modulation of substrate-molecular interactions with the assistance of a buffer layer.

The construction of a spatially defined assembly of molecular building blocks, especially in the vertical direction, presents a great challenge for surface molecular engineering. Herein, we demonstrate that an electric field applied between an STM tip and a substrate triggered the formation of a bilayer structure at the solid-liquid interface. In contrast to the typical high electric-field strength (10(9) V m(-1) ) used to induce structural transitions in supramolecular assemblies, a mild electric field (10(5) V m(-1) ) triggered the formation of a bilayer structure of a polar molecule on top of a nanoporous network of trimesic acid on graphite. The bilayer structure was transformed into a monolayer kagome structure by changing the polarity of the electric field. This tailored formation and large-scale phase transformation of a molecular assembly in the perpendicular dimension by a mild electric field opens perspectives for the manipulation of surface molecular nanoarchitectures.

A facile protocol is developed for the direct observation and characterization of a single particle electrode during the lithium ion battery operation by using in situ AFM. The SEI formation on the LiNi0.5Mn1.5O4 particle cathode surface is found to be highly related to the exposed planes.

Surface covalent organic frameworks (SCOFs), featured by atomic thick sheet with covalently bonded organic building units, are promised to possess unique properties associated with reduced dimensionality, well-defined in-plane structure, and tunable functionality. Although a great deal of effort has been made to obtain SCOFs with different linkages and building blocks via both "top-down" exfoliation and "bottom-up" surface synthesis approaches, the obtained SCOFs generally suffer a low crystallinity, which impedes the understanding of intrinsic properties of the materials. Herein, we demonstrate a self-limiting solid-vapor interface reaction strategy to fabricate highly ordered SCOFs. The coupling reaction is tailored to take place at the solid-vapor interface by introducing one precursor via vaporization to the surface preloaded with the other precursor. Following this strategy, highly ordered honeycomb SCOFs with imine linkage are obtained. The controlled formation of SCOFs in our study shows the possibility of a rational design and synthesis of SCOFs with desired functionality.

An unusual wurtzite phase of Cu2ZnGeSe4 (CZGSe) has been discovered and its corresponding nanocrystals (NCs) were synthesized by using a facile hot-injection solution-phase synthesis method. Moreover, the formation mechanism of this new phase of CZGSe, instead of the typically observed stannite structure, has been investigated in detail, which indicates that wurtzite CZGSe, which represents the kinetic phase, could be prepared by using a kinetic growth process without phase transformation into the thermodynamically stable stannite structure during the colloidal synthesis. In addition, the potential of wurtzite CZGSe as a thermoelectric material is demonstrated by characterizing the thermoelectric properties of as-synthesized wurtzite CZGSe NCs. This work allows for a rational manipulation of the NCs with a desired crystal structure through adjusting the thermodynamics and kinetics without using any additives and, because of its simplicity and versatility, it may be extended to the phase-controlled synthesis of other chalcogenide NCs.

Organic–inorganic hybrid perovskite single-crystalline thin films (SCTFs) are promising for enhancing photoelectric device performance due to high carrier mobility, long diffusion length, and carrier lifetime. However, bulk perovskite single crystals available today are not suitable for practical device application due to the unfavorable thickness. Herein, we report a facile space-confined solution-processed strategy to on-substrate grow various hybrid perovskite SCTFs in a size of submillimeter with adjustable thicknesses from nano- to micrometers. These SCTFs exhibit photoelectric properties comparable to bulk single crystals with low defect density and good air stability. The clear thickness-dependent colors allow fast visual selection of SCTFs with a suitable thickness for specific device application. The present substrate-independent growth of perovskite SCTFs opens up opportunities for on-chip fabrication of diverse high-performance devices.

We systematically studied the operation of coadsorber-induced surface chirality in a series of enantiomeric surface supramolecular assemblies. The correlation of chiral amplification degree with the proportion of enantiomeric interaction in the total intermolecular interaction is deduced.

We have fabricated hybrid molecular chain structures formed by electron acceptor compound 1 and electron donor molecules 2 and 3 at the liquid/solid interface of graphite surface. The structural details of the mono-component and the binary assemblies are revealed by high resolution scanning tunneling microscopy (STM). Compound 1 can form two well-ordered lamellar patterns at different concentrations. In the co-adsorption structures, compounds 2 and 3 can insert into the space between molecular chains of compound 1 and form large area well-ordered nanoscale phase separated lamellar structures. The unit cell parameters for the coassemblies can be “flexibly” adjusted to make the electron donors and acceptors perfectly match along the molecular chains. Scanning tunneling spectroscopy (STS) results indicate that the electronic properties of individual molecular donors and acceptors are preserved in the binary self-assembly. These results provide molecular insight into the nanoscale phase separation of organic electron acceptors and donors on surfaces and are helpful for the fabrication of surface supramolecular structures and molecular devices.

The production of clean and renewable hydrogen through water splitting using photocatalysts has received much attention due to the increasing global energy crises. In this study, a high efficiency of the photocatalytic H(2) production was achieved using graphene nanosheets decorated with CdS clusters as visible-light-driven photocatalysts. The materials were prepared by a solvothermal method in which graphene oxide (GO) served as the support and cadmium acetate (Cd(Ac)(2)) as the CdS precursor. These nanosized composites reach a high H(2)-production rate of 1.12 mmol h(-1) (about 4.87 times higher than that of pure CdS nanoparticles) at graphene content of 1.0 wt % and Pt 0.5 wt % under visible-light irradiation and an apparent quantum efficiency (QE) of 22.5% at wavelength of 420 nm. This high photocatalytic H(2)-production activity is attributed predominantly to the presence of graphene, which serves as an electron collector and transporter to efficiently lengthen the lifetime of the photogenerated charge carriers from CdS nanoparticles. This work highlights the potential application of graphene-based materials in the field of energy conversion.

The formation of several molecular 2D tilings with long-range periodicity, including the Kagome network, distorted Kagome network, and snub trihexagonal tiling from the adsorption and assembly of thiacalix[4]arene tetrasulfonate (TCAS) at the 0.1 M HClO(4)/Au(111) interface has been investigated by electrochemical scanning tunneling microscopy (STM). The internal structures of the tilings have been disclosed by high-resolution STM images. The basic structural motifs, namely, the tiles of these tilings are similar, including triangular units and hexagonal units. Due to the different arrangement of the molecules within the triangular units, tiles with different configurations are formed, which further result in the polymorphism of the 2D tiling. This result is of significance for understanding the formation of 2D tiling as well as the design and construction of molecular self-assembled nanostructures.

Halogen bonding has attracted much attention recently as an important driving force for supramolecular assembly and crystal engineering. Herein, we demonstrate for the first time the formation of a halogen bond-based open porous network on a graphite surface using ethynylpyridine and aryl-halide based building blocks. We found that the electrical stimuli of a scanning tunneling microscopy (STM) tip can induce the formation of a binary supramolecular structure on the basis of halogen bond formation between terminal pyridyl groups and perfluoro-iodobenzene. This electrical manipulation method can be applied to engineer a series of linear or porous structures by selecting halogen bond donor and acceptor fragments with different symmetries, as the directional interactions ultimately determine the structural outcome.

The electrical property of a self-assembled monolayer (SAM) of mercaptohexadecanoic acid (HS-C15H30-COOH) has been investigated with a tunneling junction confined in a capillary. This capillary method can shun the interference of vacuum gap. The contact area can be determined according to the diameter of capillary. The nonlinear current-voltage curve and dl/dV curve are measured in the potential range of +/-0.8 V. The slight asymmetry of I-V curve and dl/dV curve is attributed to the different coupling between the metal and the end-groups of molecule. This method will supply a simple way to measure the property of single molecules and monolayers.

Heterocyclic aromatic compounds have attracted considerable attention because of their high carrier mobility that can be exploited in organic field-effect transistors. This contribution presents a comparative study of the packing structure of 3,6-didodecyl-12-(3,6-didodecylphenanthro[9,10-b]phenazin-13-yl)phenanthro[9,10-b]phenazine (DP), an N-heterocyclic aromatic compound, on Au(111) and highly ordered pyrolytic graphite (HOPG). High-resolution scanning tunneling microscopy (STM) combined with atomistic simulations provide a picture of the interface of this organic semiconductor on an electrode that can have an impact on the field-effect transistor (FET) performance. DP molecules adsorb with different conformational isomers (R/S: trans isomers; C: cis isomer) on HOPG and Au(111) substrates. All three isomers are found in the long-range disordered lamella domains on Au(111). In contrast, only the R/S trans isomers self-assemble into stable chiral domains on the HOPG surface. The substrate-dependent adsorption configuration selectivity is supported by theoretical calculations. The van der Waals interaction between the molecules and the substrate dominates the adsorption binding energy of the DP molecules on the solid surface. The results provide molecular evidence of the interface structures of organic semiconductors on electrode surfaces.

With graphene-like topology and designable functional moieties, single-layered covalent organic frameworks (sCOFs) have attracted enormous interest for both fundamental research and application prospects. As the growth of sCOFs involves the assembly and reaction of precursors in a spatial defined manner, it is of great importance to understand the kinetics of sCOFs formation. Although several large families of sCOFs and bulk COF materials based on different coupling reactions have been reported, the synthesis of isomeric sCOFs by exchanging the coupling reaction moieties on precursors has been barely explored. Herein, a series of isomeric sCOFs based on Schiff-base reaction is designed to understand the effect of monomer structure on the growth kinetics of sCOFs. The distinctly different local packing motifs in the mixed assemblies for the two isomeric routes closely resemble to those in the assemblies of monomers, which affect the structural evolution process for highly ordered imine-linked sCOFs. In addition, surface diffusion of monomers and the molecule-substrate interaction, which is tunable by reaction temperature, also play an important role in structural evolutions. This study highlights the important roles of monomer structure and reaction temperature in the design and synthesis of covalent bond connected functional nanoporous networks.

The electron donor-acceptor dyads are an emerging class of materials showing important applications in nonlinear optics, dye-sensitized solar cells, and molecular electronics. Investigation of their structure and electron transfer at the molecular level provides insights into the structure-property relationship and can benefit the design and preparation of electron donor-acceptor dyad materials. Herein, the interface adstructure and electron transfer of buckyferrocene Fe(C60Me5)Cp, a typical electron donor-acceptor dyad, is directly probed using in situ electrochemical scanning tunneling microscopy (STM) combined with theoretical simulations. It is found that the adsorption geometry and assembled structure of Fe(C60Me5)Cp is significantly affected by the electrochemical environments. In 0.1 M HClO4 solution, Fe(C60Me5)Cp forms well-ordered monolayers and multilayers on Au(111) surfaces with molecular dimer as the building block. In 0.1 M NaClO4 solution, typical six-fold symmetric close-packed monolayer with vertically adsorbed Fe(C60Me5)Cp is formed. Upon electrochemical oxidation, the oxidized Fe(C60Me5)Cp shows higher brightness in an STM image, which facilitates the direct visualization of the interfacial electrochemical electron transfer process. Theoretical simulation indicates that the electrode potential-activated, one-electron transfer from Fe(C60Me5)Cp to the electrode leads to the change of the delocalization character of the frontier orbital in the molecule, which is responsible for the STM image contrast change. This result is beneficial for understanding the structure and property of single electron donor-acceptor dyads. It also provides a direct approach to study the electron transfer of electron donor-acceptor compounds at the molecular level.

Spontaneous symmetry-breaking of a racemic mixture of supramolecular triginal prisms into chiral domains on a Au(111) surface is observed by scanning tunneling microscopy (STM). High-resolution STM analysis enables the structural aspects of each enantiomeric domain to be elucidated. The ability to resolve chirality on achiral surfaces has potential applications in heterogeneous stereoselective synthesis and catalysis.

PPA nanobelts were synthesized using nanocopper particles as catalysts in the gas-phase polymerization of phenylacetylene. This route offers several advantages over the conventional method: copper is used instead of expensive noble metal catalysts; gas-phase reaction avoids the use of toxic organic solvents; highly crystalline PPA nanobelt arrays can be produced. PPA nanobelts were characterized by XRD, SEM, TEM, AFM, and DSC techniques. The PPA nanobelts were highly crystalline and have the cis-specific conformation. The I−V characteristics of a single nanobelt with different doped levels were characterized. All three belts show semiconductor features. An undoped PPA belt has the largest insulating gap (about 10 V). Doping the nanobelts with iodine significantly decreases the gap. The belt that underwent 30 min of iodine doping is nearly a conductor.

A facile method for controlling the self-assembly of supramolecular metallocycles on a highly oriented pyrolytic graphite (HOPG) surface is described. The process was demonstrated using 1,3,5-tris(10-carboxydecyloxy)benzene (TCDB), which self-assembles to form a stable monolayer with nanoscale cavities on HOPG, to template the deposition of supramolecular rectangles. Molecular distribution is controlled and monodispersion is achieved as the metallocycles self-organize into the cavities of the TCDB template.

This communication provides a facile method for distributing and dispersing molecules within a molecular template. Using the self-assembled template of oligo(phenylene-ethynylene) (OPE), organic molecules such as coronene (COR) and biomolecules such as tripeptide are controllably distributed and dispersed within this molecular template on highly oriented pyrolytic graphite (HOPG) surfaces. COR molecules were controllably distributed into various regular arrays by simply adjusting the molecular molar ratio, while tripeptide molecules were uniformly positioned at the vacancies of the OPE template.

A microscopic investigation of the molecular packing structures of a fused thiophene derivative reveals the important role of intermolecular S···S interaction in directing the 2D self-assembly. Thermal annealing of the assembly results in the irreversible phase transition to a new structure with different molecular trimeric packing motifs.

The successful exfoliation of graphite to graphene sheets in a liquid phase via tip sonication was achieved. A number of solvents were examined for several time periods and it was found that o-dichlorobenzene (o-DCB) and N-methyl-1,2-pyrolidone (NMP) are ideal solvents to exfoliate graphite and produce stable dispersions of graphene. The exfoliated graphene dispersions were characterized by complementary techniques including AFM, DLS, TGA and Raman. Furthermore, treatment of stable dispersions of exfoliated graphene sheets in NMP with poly[styrene-b-(2-vinylpyridine)] block copolymer, under acidic conditions, resulted in aqueous solubilization of graphene. Similar results were obtained, i.e. transfer of graphene from the organic to the aqueous phase, when the poly(isoprene-b-acrylic acid) block copolymer was added on exfoliated graphene in NMP.

The co-adsorption of trinitrotoluene (TNT), a typical π-electron acceptor, and triphenylene (TP), a typical π-electron donor, on a Au(111) surface was investigated by in situ Electrochemical Scanning Tunneling Microscopy (ECSTM). DFT calculations proved that parallelly stacked and well-overlapped TP and TNT molecules can form Donor-Acceptor dyads through intermolecular π-π charge transfer, which agree well with the experimental results in the present work.

A two step programmed method is developed to load mono dispersed SnO2 nanoparticles onto single layer graphene sheets. The SnO2-G composite has near mono dispersion of the SnO2 nanocrystals as well as a high SnO2 content of over 60 wt%. These outstanding features are desirable and enable the composite material to be an excellent anode material for Li-ion batteries.

Electrochemistry and adlayer structure of trinitrotoluene (TNT) on an Au(111) electrode were investigated using cyclic voltammetry and in situ electrochemical scanning tunneling microscopy (ECSTM).