Demonstrated herein is an unprecedented porous template-assisted reaction at the solid-liquid interface involving bond formation, which is typically collision-driven and occurs in the solution and gas phases. The template is a TMA (trimesic acid) monolayer with two-dimensional pores that host fullerenes, which otherwise exhibit an insignificant affinity to an undecorated graphite substrate. The confinement of C units in the TMA pores formulates a proximity that is ideal for bond formation. The oligomerization of C is triggered by an electric pulse via a scanning tunneling microscope tip. The spacing between C moieties becomes 1.4 nm, which is larger than the edge-to-edge diameter of 1.1-1.2 nm of C due to the formation of intermolecular single bonds. In addition, the characteristic mass-to-charge ratios of dimers and trimers are observed by mass spectrometry. The experimental findings shed light on the active role of spatially tailored templates in facilitating the chemical activity of guest molecules.
Sandwich complexation involving alkali or alkaline-earth metals, multivalency, and effects associated with local environments is widely encountered in biological and synthetic systems yet the mechanic properties remain unexplored. Herein, AFM (atomic force microscopy)-based single-molecule force spectroscopy is employed to investigate a classical model of M(n+)[15C5]2, a metal cation hosted jointly by two 15-crown-5 moieties immobilized on both the substrate and the AFM tip. Factors reportedly promoting the recognition performance are examined. The rupture force required to break apart M(n+)[15C5]2 is found to be in the order of tens of pico-Newton, e.g., f(β)=31 pN for K(+)[15C5]2. The presence of a second functional group, carboxylate, confers K(+)[15C5]2 with a longer lifetime (from 13 to 16 ms), faster association (from 0.4 to 1.3×10(6) M(-1) s(-1)), and slower dissociation (from 77 to 62 s(-1)). The effect of local environments is significant on association yet less critical on dissociation pathways.
To progress from laboratory research to commercial applications, it is necessary to develop an effective method to prepare large quantities and high-quality of the large-size atomically thin molybdenum dichalcogenides (MoS2). Aqueous-phase processes provide a viable method for producing thin MoS2 sheets using organolithium-assisted exfoliation; unfortunately, this method is hindered by changing pristine semiconducting 2H phase to distorted metallic 1T phase. Recovery of the intrinsic 2H phase typically involves heating of the 1T MoS2 sheets on solid substrates at high temperature. This has restricted and hindered the utilization of 2H phase MoS2 sheets suspensions. Here, we demonstrate that the synergistic effect of the rigid planar structure and charged nature of organic salt such as imidazole (ImH) can be successfully used to produce atomically thin 2H-MoS2 sheets suspension in water. Moreover, lateral size and area of the exfoliated sheet can be up to 50 μm and 1000 μm2, respectively. According to the XPS measurements, nearly 100% of the 2H-MoS2 sheets was successfully prepared. A composite paper supercapacitor using the exfoliated 2H-MoS2 and carbon nanotubes delivered a superior volumetric capacitance of ~410 F/cm3. Therefore, the organic salts-assisted liquid-phase exfoliation has great potential for large-scale production of 2H-MoS2 suspensions for supercapacitor application.
Sandwichcomplexation involving alkali or alkalineearth metals,m ultivalency,a nd effects associated with local environments is widely encountered in biological and synthetic systems yet the mechanic properties remain unexplored. Herein, AFM (atomic force microscopy)-based single-molecule force spectroscopyi se mployed to investigate ac lassical model of ). The effect of local environments is significant on association yet less critical on dissociation pathways.Molecular recognition through reversible noncovalent and multivalent interactions operating collectively with neighboring functionalities is one of the most significant features of chemical and biological systems.Among the sensing elements and synergistically acting components,m oieties of crown ethers [1][2][3] have long been acknowledged and are still actively involved in contemporary challenges;t on ame af ew: ionchannel transport, [4][5][6] modulating protein surface properties, [7] monitoring the motion of aguest molecule on amultitopic host, [8,9] template-assisted synthesis, [2,[10][11][12][13] switchable performance in catalysis [14,15] and in molecular machines, [12,13,16,17] and energy storage.[18] To achieve these tasks effectively and repeatedly,r eversible dissociation that restores the host configuration is as important as the step of associative recognition. However,t he mechanical nature to evaluate the reversibility for metal-crown ether complexes has yet been reported. Further surprisingly,literature work on thermodynamic and kinetic parameters in the solution phase [19] is scarce for the famous sandwich complexes, M n+ [crown] 2 ,t hat have been utilized in many phenomenal sensing applications.[20] Taking advantage of AFM-based (atomic force microscopy) single-molecule force spectroscopy, [21][22][23] we will quantitatively show here the mechanic strengths,free-energy landscapes,and the kinetic parameters of the dissociation of metal-crown ether complexes.Them odel system is M n+ [15C5] 2 and the experimental concept is illustrated in Figure 1Awith moieties of 15-crown5ether immobilized on Au substrate by sulfur-gold (RS-Au) .The grey and black traces indicate the directions of tip approaching toward and retracting from the substrate, respectively. To prepare panels Dand F, acquired for each case are 1000 force-distance traces in which 226 traces exhibit rupture forces for the former and 203 traces for the latter.The solid curves are Gaussian fitting from which the peak positions were determined.T he bin width of unbinding forces in the histograms is 5pN. Force measurements were performed with aloading rate of 10.5 nN s À1 (with an apparent spring constant of 0.035 nN nm À1 and aretraction velocity of 300 nm s À1 ).
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