Lijun Wan

Chinese Academy of Sciences, Peping, Beijing, China

Are you Lijun Wan?

Claim your profile

Publications (57)151.42 Total impact

  • Source
    [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.
    Advanced Functional Materials 08/2014; · 10.44 Impact Factor
  • [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.
    Langmuir 12/2012; · 4.38 Impact Factor
  • [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.
    Journal of the American Chemical Society 10/2012; · 10.68 Impact Factor
  • [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.
    Journal of the American Chemical Society 08/2012; 134(32):13252-5. · 10.68 Impact Factor
  • [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.
    Talanta 04/2011; 84(2):501-7. · 3.50 Impact Factor
  • [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.
    Journal of Electroanalytical Chemistry - J ELECTROANAL CHEM. 01/2011; 656(1):304-311.
  • [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$ \sqrt 3 $ \sqrt 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.
    Science in China Series B Chemistry 01/2009; 52(5):559-565. · 1.20 Impact Factor
  • [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.
    Science in China Series C Life Sciences 03/2008; 51(2):95-103. · 1.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two-dimensional (2D) self-assembly of two 1,3,2-dioxaborine derivatives was investigated by STM. The molecules consist of π system and steric end groups. A droplet of toluene solution containing the molecules was deposited onto HOPG for preparing the assemblies. STM images showed that the molecular structures affect the assembly structure. The dipole-dipole interaction and steric repulsion played important roles in the formation of the self-assembled monolayers.
    Chinese Science Bulletin 01/2007; 52(18):2486-2490. · 1.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Light-induced structural transformation of 4-(amyloxy)cinnamic acid (AOCA) on the surface of highly oriented pyrolytic graphite (HOPG) was investigated with scanning tunneling microscopy (STM). AOCA molecules form highly-ordered adlayer on HOPG spontaneously, stabilized by hydrogen bonding between neighboring molecules. After UV-light irradiation onto the adlayer, the ordered adlayer was disrupted and a new disordered structure was observed, which indicated that dimerization of AOCA molecules took place. The STM results reveal the direct evidence for the photoisomerization of cinnamic acid at atom level.
    Chinese Science Bulletin 05/2006; 51(11):1389-1392. · 1.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To assess the toxicity of copper nanoparticles (23.5 nm) in vivo, LD(50), morphological changes, pathological examinations and blood biochemical indexes of experimental mice are studied comparatively with micro-copper particles (17 microm) and cupric ions (CuCl(2).2H(2)O). The LD(50) for the nano-, micro-copper particles and cupric ions exposed to mice via oral gavage are 413, >5000 and 110 mg/kg body weight, respectively. The toxicity classes of nano and ionic copper particles both are class 3 (moderately toxic), and micro-copper is class 5 (practically non-toxic) of Hodge and Sterner Scale. Kidney, liver and spleen are found to be target organs of nano-copper particles. Nanoparticles induce gravely toxicological effects and heavy injuries on kidney, liver and spleen of experimental mice, but micro-copper particles do not, on mass basis. Results indicate a gender dependent feature of nanotoxicity. Several factors such as huge specific surface area, ultrahigh reactivity, exceeding consumption of H(+), etc. that likely cause the grave nanotoxicity observed in vivo are discussed.
    Toxicology Letters 05/2006; 163(2):109-20. · 3.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Oxidative stress is considered to be one of the important mechanisms involved in carcinogenesis. In our previous study, gadolinium endohedral metallofullerenol ([Gd@C82(OH)22]n nanoparticles) have shown high inhibitory activity on hepatoma cell (H22) growth in mice. To explore the antioxidative functions of nanoparticles, we investigated the biodistribution of [Gd@C82(OH)22]n nanoparticles, the changes of blood coagulation profiles, the metabolism of reactive oxygen species (ROS) in the tumor-bearing mice as well as the possible relationships between nanoparticles treatment and ROS production in this paper. The activities of hepatic superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST) and catalase (CAT) as well as the levels of reduced glutathione (GSH), protein-bound thiols and malondialdehyde (MDA) were compared between the tumor-bearing mice and normal mice. Transplanted tumors were grown in mice by subcutaneous injection of murine hepatoma cells in the mice. The comparison of the above parameters between nanoparticles and cyclophosphamide (CTX) therapy were also investigated. [Gd@C82(OH)22]n administration can efficiently restore the damaged liver and kidney of the tumor-bearing mice. All the activities of enzymes and other parameters related to oxidative stress were reduced after [Gd@C82(OH)22]n treatment and tended closely to the normal levels. The results suggest that [Gd@C82(OH)22]n nanoparticle treatment could regulate ROS production in vivo.
    Biochemical Pharmacology 04/2006; 71(6):872-81. · 4.58 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report a novel process to prepare well-dispersed Pt nanoparticles on CNTs. Pt nanoparticles, which were modified by the organic molecule triphenylphosphine, were deposited on multiwalled carbon nanotubes by the organic molecule, which acts as a cross linker. By manipulating the relative ratio of Pt nanoparticles and multiwalled carbon nanotubes in solution, Pt/CNT composites with different Pt content were achieved. The so-prepared Pt/CNT composite materials show higher electrocatalytic activity and better tolerance to poisoning species in methanol oxidation than the commercial E-TEK catalyst, which can be ascribed to the high dispersion of Pt nanoparticles on the multiwalled carbon nanotube surface.
    The Journal of Physical Chemistry B 01/2006; 109(47):22212-6. · 3.61 Impact Factor
  • Yuxia Diao, Dirk Rohde, Lijun Wan
    [Show abstract] [Hide abstract]
    ABSTRACT: AbstractThe adsorption of four β-dicarbonyl derivatives on highly oriented pyrolytic graphite (HOPG) surface was studied by scanning tunneling microscopy (STM) in an ambient environment. All the molecules include a π-conjugated part and alkyl chains in their chemical structures. The molecules were dissolved in toluene solvent and a drop of the solution was deposited on HOPG to form self-assembled adlayers. The characteristic stripe-like structure in the self-assembled monolayers (SAMs) on the high-resolution STM images of the compounds was observed. Different molecular structures led to different SAMs. It was found that noncovalent interactions such as hydrogen bonds and dipole-dipole interactions played an important role in the formation of different SAMs.
    Acta Physico-Chimica Sinica. 01/2006;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Novel air-stable n-type organic field-effect transistors based on 4,4'-bis[(6,6'-diphenyl)-2,2-difluoro- 1,3,2-dioxaborine] (DOB) have been fabricated. The devices exhibit a filed-effect mobility of 1 x 10(-4) cm(2) V-1 s(-1), an on/off ratio of 10(4) and a threshold voltage of 8.6 V at room temperature under ambient conditions. Moreover, ambipolar organic field-effect transistors based on DOB and copper phthalocyanine (CuPc) have been fabricated. Two device structures were adopted to investigate their transport properties. When devices were constructed with DOB as the first layer and CuPc as the second layer, they showed typical ambipolar transport properties. However, when the two layers were exchanged, the devices only showed p-channel transport properties. It is probable that CuPc, a bad electron transport material, blocks the electron transport to the DOB layer, leading to the disappearance of electron enhancement.
    Journal of Materials Chemistry 01/2006; 16(46):4499-4503. · 5.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Platinum (Pt) and Pt-based composite nanotubes were fabricated by a facile dipping method within alumina templates. The morphology, structure, and composition of the nanotubes were characterized by SEM, TEM, and EDX. A hydrogen sensor based on Pt/TiO2 composite nanotubes showed high hydrogen sensitivity.
    Journal of Nanoscience and Nanotechnology 12/2005; 5(11):1929-32. · 1.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, poly (lactide-co-glycolide) (PLGA) films were treated by oxygen plasma. The surface structure, topography and surface chemistry of treated PLGA films were characterized by contact angle measurement, scanning electron microscope observation, atomic force microscopy, and X-ray photoelectron spectrum analysis. The cell affinity of the oxygen plasma treated films was evaluated under dynamic conditions by Parallel Plate Flow Chamber (PPFC). The results showed that the hydrophilicity increased greatly after oxygen plasma treatment. High quantities of -C-O groups, such as hydroxyl and peroxyl groups could be incorporated into the surface of PLGA (70/30) by controlling appropriate plasma treatment conditions. Moreover, the oxygen plasma treatment resulted in formation of peaks and valleys on the sample surfaces, and the roughness increased with treatment time. Cells stretched very well and the ability to endure the shear stress was improved greatly after the PLGA (70/30) was modified by appropriate plasma treatment, i.e. under 50W for 2 or 10 min. However, when the treatment time was increased to 20 min, the percentage of adherent cells on the roughest surface decreased because the content of polar groups incorporated onto the surface decreased. The results showed that improved cell adhesion was attributed to the combination of surface chemistry and surface morphology of PLGA during plasma etching.
    Biomaterials 09/2004; 25(19):4777-83. · 8.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the present work, we investigated self-assembling of a poly(phenylacetylene) carrying L-valine pendants (PPA-Val) in a water/methanol solution, upon evaporation of the solution on mica, and on the water surface. With intercalation of a fluorescence probe of Ru(phen)2(dppx)2+ (phen = 1,10-phenanthroline, dppx=7,8-dimethyldipyridophenazine) into the hydrophobic cavities associated by the PPA-Val chains, their helical structures were directly detected in solution with an in situ fluorescence microscope. Helical aggregates were observed with AFM upon evaporation of the solvents, suggesting that the helical structures in the solution are the building blocks of the helical aggregates. Self-assembling structures of PPA-Val on the water surface were, however, very different from that formed upon evaporation of its THF solution on the mica surface. The polymer chains associated into a monolayer of extended fibers on the water surface, whereas superhelical fibers formed on the mica surface. Water molecules play a critical role in inducing the polymer to form diverse morphological structures in its bulk solution and on its surface. In solution, the isotropic hydrophobic effect drove the polymer chains to form superhelical aggregates, while on the water surface, the hydrophobic effect concentrated mainly on the lateral part of the polymer, thus giving a monolayer of extended fibers.
    Langmuir 09/2004; 20(18):7598-603. · 4.38 Impact Factor
  • Source
    Analytical Biochemistry 07/2004; 329(2):334-6. · 2.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In situ scanning tunneling microscopy (STM) and cyclic voltammetry were employed to investigate the adsorption structures of three semi-crown ligands on an Au(111) surface under the potential control. It is found that all the molecules formed ordered arrays in 0.1 mol/L HClO4 solution, although their geometric structures are complex and asymmetric. The driving force was supposed to come from the balance between intermolecular and molecule-substrate interactions. High resolution STM images revealed internal molecular structures, orientations and packing arrangements in the ordered adlayers. The results are useful for preparing ordered arrays of transition metal-mediated nanostructures.
    Science in China Series B Chemistry 06/2004; 47(4):320-325. · 1.20 Impact Factor

Publication Stats

610 Citations
151.42 Total Impact Points

Institutions

  • 2002–2014
    • Chinese Academy of Sciences
      • • Key Laboratory of Molecular Nanostructure and Nanotechnology
      • • Institute of Chemistry
      Peping, Beijing, China
  • 2002–2011
    • Technical Institute of Physics and Chemistry
      Peping, Beijing, China
  • 2001–2011
    • Northeast Institute of Geography and Agroecology
      • • Institute of Chemistry
      • • Laboratory of Photosynthesis and Environmental Biology
      • • Institute of High Energy Physics
      Beijing, Beijing Shi, China
  • 2003
    • China University of Mining & Technology Beijing Graduate School
      Peping, Beijing, China