[Show abstract][Hide abstract] ABSTRACT: The electrode/electrolyte interface plays a critical role in the performance of a Li-ion battery. In view of the dynamic and complex nature of the interface, in situ research approaches can provide valuable information of interfacial phenomena during battery operation. In situ scanning probe microscopy (SPM) is a powerful technique used for the interfacial investigation of the Li-ion batteries. The versatile SPM techniques and their various operation modes have been utilized to measure the morphology and other properties of the electrode interface at high resolution. Herein, we discuss the related SPM techniques to study the topography, mechanics and electrochemistry research of electrodes. Recent progresses of in situ SPM research on the electrode/electrolyte interface are summarized. Finally, the outlook of the technique is discussed.
[Show abstract][Hide abstract] ABSTRACT: Polyanion-type cathode materials are well known for their low electronic conductivity. Accordingly the addition of conductive carbon in the cathode materials becomes an indispensable step for their application in lithium ion batteries. To maximize the contribution of carbon, a core shell structure with a full coverage of carbon should be favorable due to an improved electronic contact between different particles. Here, we report the formation of a uniform carbon nanoshell on a typical cathode material, LiFePO4, with the shell thickness precisely defined via the 3-Aminophenol-Formaldehyde polymerization process. In addition to the higher discharge capacity and the improved rate capability as expected from the carbon nanoshell, we identified that the core-shell configuration could lead to a much safe cathode material as revealed by the obviously-reduced iron dissolution, much less heat released during the cycling, and better cyclability at high temperature.
No preview · Article · Dec 2014 · ACS Applied Materials & Interfaces
[Show abstract][Hide abstract] ABSTRACT: The poly(maleic anhydride-alt-1-octadecene-poly(ethylene glycol)) (C18PMH-PEG) modified single-walled carbon nanohorns (SWNHs) are designed with high stability and biocompatibility. The as-prepared SWNHs/C18PMH-PEG not only can serve as an excellent photothermal agent but also can be used as a promising photoacoustic imaging (PAI) agent both in vitro and in vivo due to its strong absorption in the near infrared (NIR) region. The PAI result reveals that the SWNHs/C18PMH-PEG possesses ultra long blood circulation time and can significantly be accumulated at the tumor site through the enhanced penetration and retention (EPR) effect. The maximum accumulation of SWNHs/C18PMH-PEG at tumor site could be achieved at the time point of 24 h after intravenous injection, which is considered to be the optimal time for the 808 nm laser treatment. The subsequent photothermal ablation of tumors can be achieved without triggering any side effects. Therefore, a PAI guided PTT platform based on SWNHs is proposed and highlights the potential theranostic application for biomedical uses.
Full-text · Article · Nov 2014 · Advanced Functional Materials
[Show abstract][Hide abstract] ABSTRACT: We investigated the interfacial electrochemical processes on graphite anode of lithium ion battery by using highly oriented pyrolytic graphite (HOPG) as a model system. In situ electrochemical atomic force microscopy experiments were performed in 1 M lithium bis(trifluoromethanesulfonyl)imide/ethylene carbonate/diethyl carbonate to reveal the formation process of solid electrolyte interphase (SEI) on HOPG basal plane during potential variation. At 1.45 V, the initial deposition of SEI began at the defects of HOPG surface. After that, direct solvent decomposition took place at about 1.3 V, and the whole surface was covered with SEI. The thickness of SEI was 10.4 ± 0.2 nm after one cycle, and increased to 13.8 ± 0.2 nm in the second cycle, which is due to the insufficient electron blocking ability of the surface film. The Young’s modulus of SEI was measured by a peak force quantitative nanomechanical mapping (QNM). The Young’s modulus of SEI is inhomogeneous. The statistic value is 45 ± 22 MPa, which is in agreement with the organic property of SEI on basal plane of HOPG.
No preview · Article · Nov 2013 · Science China-Chemistry
[Show abstract][Hide abstract] ABSTRACT: The adsorption behaviors of subphthalocyanine (SubPc) and subnaphthalocyanine (SubNc) on the Au(111) surface were investigated by electrochemical scanning tunneling microscopy (ECSTM). Two types of ordered adlayer structures of SubPc were observed at 550 mV vs reversible hydrogen electrode (RHE). All the SubPc molecules take the Cl-down adsorption configuration on Au(111) in both structures. The ordered adlayers exist in the potential range between 350 mV and 650 mV. The SubNc molecules adsorb on Au(111) in a less ordered pattern than the SubPc molecules. The present work provides direct evidence for understanding the potential-controlled adsorption behaviors of SubPc and SubNc on the Au(111) surface.
[Show abstract][Hide abstract] ABSTRACT: Hierarchical structures, in which structure is generated and controlled simultaneously at different size scales, have attracted increasing attention due to their potentials in both theoretical research and practical applications. In this review, a “non-classical crystallization” mechanism is discussed for their possibilities in morphology control of hierarchically-structured materials. Differently, this crystallization route is not based on the attaching and detaching of monomers as happened in the classical case, but through the self-organization of preformed building blocks as nanosized subunits, whose oriented attachment leads to mesocrystals with favorable morphology and texture. Representative materials including both inorganic and organic crystals are reported with possible mechanisms proposed. Synthetic protocols based on this mechanism provide unique inspirations for materials design and could be applied to morphological and structural control of new materials with optimized functions.
Full-text · Article · Nov 2012 · Science China-Chemistry
[Show abstract][Hide abstract] ABSTRACT: Silicon-based nanomaterials have been of scientific and commercial interest in lithium-ion batteries due to the low cost, low toxicity, and high specific capacity with an order of magnitude beyond that of conventional graphite. The poor capacity retention, caused by pulverization of Si during cycling, triggers researchers and engineers to explore better battery materials. This review summarizes recent work in improving Si-based anode materials via different approaches from diverse Si nanostructures, Si/metal nanocomposites, to Si/C nanocomposites, and also offers perspectives of the Si-based anode materials.
Full-text · Article · Nov 2012 · Chinese Science Bulletin
[Show abstract][Hide abstract] ABSTRACT: Lithium-sulfur battery holds a high theoretical energy density, 4-5 times of today's lithium-ion batteries, yet its applications have been hindered by poor electronic conductivity of the sulfur cathode and most importantly, its rapid capacity fading due to the formation of soluble polysulfide intermediates (Li2Sn, n = 4-8). Despite of numerous efforts concerning this issue, the combat with sulfur loss still remains one of the greatest challenges. Here we show that such a problem can be effectively diminished by controlling the sulfur into smaller allotropes. Metastable small sulfur molecules of S2-4 were synthesized with the space confinement effect of a conductive microporous carbon matrix. Different from the commonly-used large S8, the confined S2-4 as a new cathode material can totally avoid the unfavorable transition between S8 and S42-. Lithium-sulfur batteries base on this concept exhibits unprecedented electrochemical behavior with high specific capacity, good cycling stability and superior rate capability, which promise a practicable battery with high energy density for the applica-tions in portable electronics, electric vehicles, as well as large-scale energy storage systems.
No preview · Article · Oct 2012 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: We have designed and synthesized a polyaniline (PANI)-decorated Pt/C@PANI core-shell catalyst that shows enhanced catalyst activity and durability compared with nondecorated Pt/C. The experimental results demonstrate that the activity for the oxygen reduction reaction strongly depends on the thickness of the PANI shell and that the greatest enhancement in catalytic properties occurs at a thickness of 5 nm, followed by 2.5, 0, and 14 nm. Pt/C@PANI also demonstrates significantly improved stability compared with that of the unmodified Pt/C catalyst. The high activity and stability of the Pt/C@PANI catalyst is ascribed to its novel PANI-decorated core-shell structure, which induces both electron delocalization between the Pt d orbitals and the PANI π-conjugated ligand and electron transfer from Pt to PANI. The stable PANI shell also protects the carbon support from direct exposure to the corrosive environment.
No preview · Article · Aug 2012 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: SnO2 hollow spheres have been synthesized via a facile hydrothermal method using sulfonated polystyrene beads as a template followed by a calcination process in air. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy show that the as-obtained SnO2 hollow spheres have a wall thickness of about 50 nm, and consist of nanosized SnO2 particles with a mean diameter of about 15 nm. Electrochemical measurements indicate that the SnO2 hollow spheres exhibit improved electrochemical performance in terms of specific capacity and rate capability in comparison with commercial SnO2 when used as anode materials for lithium-ion batteries. The enhanced performance may be attributed to the spherical and hollow structure, as well as the building blocks of SnO2 nanoparticles.
No preview · Article · Jul 2012 · Science China-Chemistry
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Jan 2012 · Science China-Chemistry
[Show abstract][Hide abstract] ABSTRACT: A hybrid electrochemical energy storage device was fabricated in aqueous NaOH with the 2,2,6,6-tetramethyl-1-piperidinyloxy
(TEMPO) nitroxide radical as the active material, hydroquinone as the counter electrode active material, and an OH−-selective separating membrane. The working principle of this device was investigated and it can be considered as a supercapacitor-battery
hybrid energy storage system. Device performance was characterized by cyclic voltammetry and galvanostatic charge-discharge
testing. When using multi-walled carbon nanotubes (MWCNTs) as electrode support materials, a high pseudo-capacitance of 1280
F g−1 was obtained with the TEMPO nitroxide radical as the active material at a 1 mV s−1 scan rate. This was ∼33 times larger than the inherent double layer capacitance of MWCNTs. The electrode material and active
material dissolved in solution could potentially be substituted with similar materials. This simple design provides a new
approach for fabricating high performance supercapacitor-battery hybrid energy storage devices.
Keywordsnitroxide radical–electrochemical energy storage device–hybrid system–reversible redox reaction–aqueous solution electrolyte
Full-text · Article · Aug 2011 · Chinese Science Bulletin
[Show abstract][Hide abstract] ABSTRACT: The self-assembly and photo-induced structural transformation of a diarylethene derivative 1,2-bis(3,5-dimethyl dithioene [3,2-b:2′,3′-d]thiophene-2-yl) perfluorocyclopentene (BDDTP) have been investigated by cyclic voltammetry and electrochemical scanning tunneling microscopy (EC-STM) on a Au(111) substrate. BDDTP was found to form two ordered adlayer structures on Au(111) surface. STM observation revealed that the original ordered structures transformed into disordered adlayers after ex situ and in situ ultraviolet (UV) irradiation. Such a dramatic difference in the self-assembly behavior of BDDTP before and after UV irradiation results from the conformational transformation induced by photo-irradiation and the associated molecule–substrate interaction change. The result provides useful information to understand the self-assembly behavior and photochromic reaction of diarylethenes compounds on solid supports.
No preview · Article · Jun 2011 · Journal of electroanalytical chemistry
[Show abstract][Hide abstract] ABSTRACT: A new amphipathic block copolymer, poly(tert-butyl acrylate)(127)-block-poly(glycidyl methacrylate)(86), was developed for the coating in open tubular capillary electrochromatography. The self-assembly characters of the coating, which could form micelle-like aggregates under proper conditions, were observed by atomic force microscopy. Compared with bare capillary, this coating could act as surfactant and lead to improve the separation of steroids. In addition, the influence of pH, buffer concentration and organic solvents on the separation was investigated. The best separation of the three model steroid analytes could be achieved using 20.0mM borate buffer at pH 10.5. For covalent bonding, the coating showed good repeatability and stability with RSD of u(EOF) less than 3.3%. Then, this proposed method was well validated with good linearity (≥ 0.999), recovery (91.0-94.0%) and repeatability, and was successfully used for separation of steroids in spiked serum samples, which indicated that this new OT-CEC method could provide a potential tool to determine steroids in real biological system without interference.
[Show abstract][Hide abstract] ABSTRACT: A rapid and facile method was found to access one-molecule-thick free-standing organic nanosheets in a high yield with controllable size and shape by self-assembly of cucurbituril and small organic molecules.
Full-text · Article · Feb 2010 · Chemical Communications
[Show abstract][Hide abstract] ABSTRACT: The adsorption and adlayer structures of tetrathiofulvalene (TTF), tetracyanoquinodimethane (TCNQ) and TTF-TCNQ on Au(111)
have been systematically investigated by in situ electrochemical scanning tunneling microscopy (ECSTM) and cyclic voltammetry in 0.1 mol L−1 HClO4. All the three molecules were found to form well-ordered adlayers in the double-layer potential region of Au(111). For TTF
and TCNQ adlayers, (6×3) and (4×7) structures have been observed, respectively. A structural transition was observed on TCNQ
adlayer at potential negative of 0.08 V vs. the reversible hydrogen electrode (RHE), and induced a new phase with (3$
× 12) structure. On the other hand, the charge transfer complex, TTF-TCNQ, self-organized into ordered domains with a lamellar
structure different from those of the pure TTF and TCNQ adlayers on Au(111). Its packing arrangement was comparable to surface
structures of either single crystal or thin film of TTF-TCNQ.
No preview · Article · May 2009 · Science in China Series B Chemistry
[Show abstract][Hide abstract] ABSTRACT: As water is gradually added, a p-terphenyl derivative with dumbbell-like amphiphilic and rod-coil characteristics can hierarchically self-assemble to metastable rectangle columns architecting sheets first and then to stable quasi-hexagonal columns architecting rolled sheets, and finally to rod-like nanostructures in MeOH/H2O solution. Interestingly, the formed sheet, rolled sheet, and nanorod possess blue-light emitting property.
No preview · Article · Sep 2008 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8+/-0.09 nm in diameter and 1.9+/-0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40-60 nm, and a range of 1.8-5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12-40 nm for their diameter and 0.7-2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 microm(2). According to their size, we classified the invaginated pits into two types--larger pits measuring 139 nm in diameter and 7.2 nm in depth, and smaller pits measuring 96 nm in diameter and 2.3 nm in depth. On dehydration-induced dead protoplasts, the degree of polarization of plasma membranes decreased. Lipid molecular layers appeared relatively smooth, and the quantity of integral proteins reduced a lot. Invaginated pits were still detectable at the membrane surface, but due to dehydration-induced protoplast contraction, the orifice diameter of pits reduced, and their depth increased. Larger pits averagely measuring 47.4 nm in diameter and 31.9 nm in depth, and smaller pits measuring 26.5 nm in diameter and 43 nm in depth at average. The measured thickness of plasma membranes of mesophyll cells from winter wheat examined by AFM was 6.6-9.8 nm, thicker in regions covered with proteins.
No preview · Article · Mar 2008 · Science in China Series C Life Sciences