Template-Assisted Proximity for Oligomerization of Fullerenes.

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 C84 units in the TMA pores formulates a proximity that is ideal for bond formation. The oligomerization of C84 is triggered by an electric pulse via a scanning tunneling microscope tip. The spacing between C84 moieties becomes 1.4 nm, which is larger than the edge-to-edge diameter of 1.1-1.2 nm of C84 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.

Large-Scale Production of Large-Size Atomically Thin Semiconducting Molybdenum Dichalcogenide Sheets in Water and Its Application for Supercapacitor.

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 µm(2), 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/cm(3). Therefore, the organic salts-assisted liquid-phase exfoliation has great potential for large-scale production of 2H-MoS2 suspensions for supercapacitor application.

Force Spectroscopy of Metal-Crown Ether Multivalency: Effect of Local Environments on Energy Landscape and Sensing Kinetics.

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(ß)=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.

Paper spray-MS for bioanalysis.

This Review provides a general understanding of paper spray-MS, including the methodology and theory associated with a number of different related applications. This method has become a direct sampling/ionization method for mass spectrometric analysis at ambient conditions and, as a result, it has greatly simplified and increased the speed of mass-spectrum analysis. It has now become an increasingly popular and important method for MS. The first part of this review discusses the fundamentals of paper spray. Some modifications are also reviewed, including nib-assisted paper spray, droplet monitoring, high-throughput paper spray, leaf spray, tissue spray and wooden tip spray. The second part focuses on recent applications, including the analysis of DBS, foodstuffs, drugs and oil. These studies show that paper spray-MS has great potential for use as a fast sampling ionization method, and for the direct analysis of biological and chemical samples at ambient conditions.

Dual polarization interferometric and capillary electrophoretic analysis of supported lipid bilayer constructed on silica-based surface: evaluation of its anti-protein adsorption effect.

Supported lipid bilayer (SLB) has been demonstrated as a model of cell membranes with prospective bioanalytical or biotechnological applications. In this study, the formation of SLB and their potential biofunctionality against protein adsorption were investigated by Dual Polarization Interferometry (DPI) and Capillary Electrophoresis (CE). DPI studies on different formulations of double-chained, zwitterionic phospholipidlipids, allow the process of bilayer formation to be followed in situ and in real time. Furthermore the anti-protein adsorption effect provided by the various formulated SLBs was examined by DPI. In addition, the SLB coatings of the same lipid formulations were subsequently employed in CE experiments as a pseudo-stationary phase for demonstrating more efficient separation of alkaline protein standard mixtures. SLB-assisted CE was found to be capable of separating 4 alkaline proteins (protonated at neutral pH). This study demonstrates the applicability of DPI to monitor the process of SLB formation; and our findings, obtained by both DPI and CE, confirm that the presence of the SLB reduced drastically the problematic interactions between cationic, alkaline proteins and the negatively charged silica capillary wall, leading to better recovery and efficient separation of the proteins under investigation.

Online identification of the fluorescent whitening agent 4,4-bis(2-sulfostyrol)biphenyl using a sweeping technique combined with capillary electrophoresis/77 K fluorescence spectroscopy.

The feasibility of combining the techniques of online concentration and CE/low-temperature fluorescence spectroscopy in the detection and identification of E,E-4,4'-bis(2-sulfostyryl)biphenyl (DSBP) in synthetic detergents at 77 K is demonstrated. The technique involves the use of sweeping-MEKC, and was used for the initial online concentration and separation, after which a cryogenic molecular fluorescence experiment was performed at 77 K. The proposed method not only permits the separation and detection of E,E-DSBP in a synthetic detergent sample, but also ensures that the online spectrum is readily distinguishable and can be unambiguously assigned at 77 K. The photoconversion and isomer separation of DSBP are also described.