Lei Wang

Tsinghua University, Peping, Beijing, China

Are you Lei Wang?

Claim your profile

Publications (129)301.45 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Perovskite bismuth ferrite-BFO (111) membranes, as a potential sensitive electrochemical sensor, are investigated for the detection of amino acids by molecular dynamics (MD) and density functional theory (DFT) techniques. For the detection mechanism of the ferromagnetic phase BFO (111) membrane, the cation bridge model indicates that there is a electronic signal amplification (0.01–0.09 V), due to the enhancement of Fe3+–COO− triple degeneracy orbit (t2g). It is an excellent detection sensitivity for various AAs that can be used to distinguish the surface charges. However, the Fe-d7/2 momentum changes its orientation from upward to downward, on the anti-ferromagnetic phase BFO (111) membrane. The empty d0 orbital degenerates to the O↓ orbital that weakens the Fe–O electron transfer rate, weakening the electronic signal (0.005–0.05 V).
  • [Show abstract] [Hide abstract]
    ABSTRACT: The prognostic value of IDH1 mutations has been systematically evaluated in acute myeloid leukemia (AML) patients recently. However, the role of IDH1 expression in AML is still under exploration. To investigate the clinical significance, we analyzed the IDH1/2 expression in 320 patients with cytogenetically normal AML (CN-AML) by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR). High expression of IDH1 was predominant in patients with FLT3-ITD and DNMT3A mutations, and less prevalent in cases with CEBPA double allele mutations. Strong association was observed between high IDH1 expression and low expression of microRNA 181 family. Prognosis was adversely affected by high IDH1 expression with shorter overall survival (OS) and event free survival (EFS) in the context of clinical characteristics including age, WBC, and gene mutations of NPM1, FLT3-ITD, CEBPA, IDH1, IDH2, and DNMT3A in CN-AML. Moreover, the clinical outcome of IDH1 expression in terms of OS, EFS and complete remission rate still remained in multivariate models in CN-AML. Importantly, the prognostic value was validated using the published microarray data from 79 adult patients treated according to the German AMLCG-1999 protocol. Our results demonstrated that high IDH1 expression is associated with a poor prognosis of CN-AML. This article is protected by copyright. All rights reserved. © 2014 UICC.
    International Journal of Cancer 09/2015; 137(5). DOI:10.1002/ijc.29395 · 5.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effects of cation distribution on optical properties of MnxCo2.52−xNi0.48O4 serial thin films are investigated by spectroscopic ellipsometry and Raman technique. The optical constants present a distinctive difference with the change of the cation distribution in the serial films. Three absorption structures are found in the dielectric constant spectra while their intensities strongly depend on the distribution of cations. Complementary Raman scattering measurements corroborate the varying absorptions are mainly contributed by Mn ions in high photon energy range but Co ions in low.
    Materials Letters 08/2015; 153. DOI:10.1016/j.matlet.2015.04.046 · 2.27 Impact Factor
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We reported a facile single-solution fabrication method to grow large-scale CH3NH3PbBr3 hybrid perovskite single crystal at room temperature. The obtained single crystal in this experiment was 14 × 14 mm. The sample’s in situ photophysics properties under dark and illumination, including the surface morphology, work function, surface current distribution, microcosmic I–V curves, as well as the polarization behavior, were in situ characterized by integrated utilization of a scanning probe microscopy, respectively. Piezoresponse force microscopy (PFM) phase angles indicated the existence of “polarization” in CH3NH3PbBr3 lattice. Interestingly, the “polarization effect” was enhanced by the plus light source. Moreover, a surface potential shift as large as 200 mV was observed under the condition of the illumination on and off. This research is proposed to provide an opportunity to take a fresh look at the architectural design and photovoltaic performance origin of the hybrid perovskite solar cells.Keywords: I−V curve; scanning probe microscopy; piezoresponse force microscopy; hybrid perovskite solar cell
    Journal of Physical Chemistry Letters 06/2015; 6(13):2622-2628. DOI:10.1021/acs.jpclett.5b01017 · 7.46 Impact Factor
  • Source
    Lei Wang · Wei Li · Steven J. Schmieg · Duan Weng
    [Show abstract] [Hide abstract]
    ABSTRACT: In the present work, a series of Cu/SAPO-34 catalysts with varying number of Brønsted acid sites has been prepared by ion exchanging with potassium to investigate the role of Brønsted acidity in the NH3-SCR reaction. The impact of potassium on the structural and acidic properties of Cu/SAPO-34 catalysts has been studied. No significant changes in both the SAPO-34 structure and the copper species were observed in the presence of potassium. With increasing potassium loading, the NH3-SCR activity of the Cu-K/SAPO-34 catalysts decreased in accordance with the decreasing Brønsted acidity. The quantification method of Brønsted acid sites in the Cu-(K)/SAPO-34 was developed by using IR spectroscopy, which was confirmed by acid site generation mechanism and NH3-TPD results. A linear relationship was found between the amounts of Brønsted OH groups determined by DRIFTS and the NH3 desorbed at high temperatures from NH3-TPD.
    Journal of Catalysis 04/2015; 324. DOI:10.1016/j.jcat.2015.01.011 · 6.07 Impact Factor
  • Source
    Jiaqi Zhang · Liang Bian · Wei Ren · Lei Wang · Jinbao Xu
    [Show abstract] [Hide abstract]
    ABSTRACT: The electrical and microstructural properties of SnO2-based varistor ceramic sample were improved by addition of Pr6O11. It was found that the introduction of Pr6O11 can lead to a great improvement in the threshold voltage and the non-linear electrical properties of SnO2-based varistors. As the amount of Pr6O11 increased from 0.00 to 0.5 mol%, the mean grain size decreases from 16.64 to 7.58 μm, the relative dielectric constant (at 1 kHz) increases from 1243.2 to 4534.6, the non-linear coefficient increases from 15.44 to 18.25 and the break down electrical field increases from 275.3 to 880.5 V/mm. The structure-property relationship is discussed systematically.
    Ceramics International 04/2015; 41(8). DOI:10.1016/j.ceramint.2015.03.315 · 2.09 Impact Factor
  • Lei Wang · Shao Xie · Longjun Ma · Yi Chen · Wei Lu
    [Show abstract] [Hide abstract]
    ABSTRACT: Fifteen novel homocamptothecin derivatives with α-OMe substituted E-rings were designed and synthesized. All of the derivatives exhibited similar or superior cytotoxicities compared with that of SN-38, and they inhibited Topo I activity in a cell-free assay in a manner similar to that of SN-38, confirming that they represent a new class of Topo I inhibitors. Notably, the water soluble compound 36o (1.2mg/mL) exhibited increased lactone stability, and at 0.5mg/kg and 3.0mg/kg, it demonstrated significant antitumor activity in mice bearing a xenograft model using human colon cancer cell line HT-29. On the basis of these positive results, further development of 36o-related compounds as potential anticancer clinical trial candidates is definitely warranted. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Bioorganic & medicinal chemistry 03/2015; 23(9). DOI:10.1016/j.bmc.2015.03.031 · 2.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, ZnO–CuO composite porous spheres with core–shell structure were successfully synthesized through a controllable simple top-down route to take advantage of the excellent features of ZnO and CuO. The crystal structure and morphology of the as-prepared products were characterized, and a possible growth mechanism was proposed. The obtained sample with a core surrounded by a porous shell has a large surface area. As CuO can well catalyze glucose in alkaline solution, together with the good electron transfer property of ZnO and the hetero-junction formed between them, non-enzymatic glucose sensors based on ZnO–CuO composite porous spheres show good performance with a wide linear range of 0.02–4.86 mM, a high sensitivity of 1,217.4 μA cm−2 mM−1, and a low detection limit of 1.677 μM, indicating a good detection behavior of glucose.
    Applied Physics A 03/2015; 118(3). DOI:10.1007/s00339-014-8855-8 · 1.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Spontaneous polarization behaviors of hybrid perovskite CH3NH3PbI3 film were confirmed by in situ PFM and spectroscopic ellipsometry. The film exhibits uniform spontaneous polarization and ferroelectric domain inversion performance. The fitted dielectric constants spectra agree well with the calculated ones. We attribute the spontaneous polarization behaviors of hybrid perovskite to lone pair electrons, and its outstanding photovoltaic performance partially originates from spontaneous polarization and plasma resonance. This report will facilitate understanding of the instinct physical essence of hybrid perovskite solar cells.
    Scripta Materialia 02/2015; 102. DOI:10.1016/j.scriptamat.2015.01.030 · 2.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Idiopathic thrombocytopenic purpura (ITP) is a primary autoimmune disease with a decreased platelet count caused by platelet destruction mediated mainly by platelet antibodies. T follicular helper (TFH) cells have demonstrated important roles in autoimmune diseases. The aim of this study is to explore the might role of TFH cells in the patients of ITP. Twenty-three ITP patients and 12 healthy controls (HC) were enrolled in this study. The frequency of circulating TFH cells in both the patients and HC was analyzed by flow cytometry. Serum interleukin (IL)-21 and IL-6 levels were measured using ELISA, and platelet antibodies were tested using a solid phase technique. Additionally, IL-21, IL-6, Bcl-6 and c-Maf mRNA expressions in peripheral blood mononuclear cells (PBMCs) were detected using real-time PCR. The percentages of circulating CXCR5(+) CD4(+)TFH cells with ICOS(high) or PD-1(high) expression were significantly higher in the ITP patients than in the HC. Moreover, the frequencies of circulating CXCR5(+) CD4(+)TFH cells with inducible costimulator (ICOS)(high) or programmed death-1 (PD-1)(high) expression were notably higher in ITP with platelet-antibody-positive ( ITP (+) ) patients than in ITP with platelet-antibody-negative ( ITP (-) ) patients and HC, as were the serum IL-21 and IL-6 levels (significant). Moreover, a positive correlation was found between the CXCR5(+)CD4(+)TFH cells with ICOS(high) or PD-1(high) expression and the serum IL-21 levels of ITP (+) patients. Additionally, the mRNA expression levels of IL-21, IL-6, Bcl-6 and c-Maf were significantly increased in ITP patients, especially in ITP (+) patients. This study demonstrated TFH cells and effector molecules might play an important role in the pathogenesis of ITP, which are possible therapeutic targets in ITP patients.
    International journal of biological sciences 01/2015; 11(2):220-9. DOI:10.7150/ijbs.10178 · 4.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The variations of work functions in Mn1.56Co0.96Ni0.48O4 (MCN) thin films are investigated in the temperature range from 30 to 80 [degree]C. The high resolution images of the contact potential difference (CPD) of MCN thin films were obtained through Kelvin probe force microscopy (KPFM) and the correlations between the work functions and temperatures were demonstrated through the imaginary part of the dielectric functions. The complex dielectric spectra are temperature dependent while their intensities have the inverse trend according to the work functions. The phenomenon can be interpreted by different chemical states that relate to the Mn3+ state.
    RSC Advances 01/2015; 5(83):67738-67741. DOI:10.1039/C5RA11628G · 3.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The optical properties of spinel Mn1.56Co0.96Ni0.48O4 thin films have been investigated by spectroscopic ellipsometry in the temperature range from 20 to 260 degrees C. By fitting the measured ellipsometric parameter data with a three-layer model by Tauc-Lorentz oscillator dispersion formula, the refractive index and extinction coefficient of the thin films are determined in the spectral range of 280-850 nm. The refractive index decreases in the short-wavelength region but increases in the long-wavelength region with increasing temperature. The extinction coefficient increases with increasing temperature in all visible region.
    Materials Letters 12/2014; 136:225-228. DOI:10.1016/j.matlet.2014.08.025 · 2.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 thin films have been deposited on Pt/Ti/SiO2/Si substrates by a modified sol-gel technique. The samples are well-crystallized perovskite ferroelectrics at room temperature, with good surface topography. Optical properties of these films in the 280-850 nm wavelength range have been investigated by spectroscopic ellipsometry at room temperature. The measured ellipsometry parameters are well fitted by Tauc-Lorentz oscillator dispersion formula. As the wavelength increases, the refractive index and extinction coefficient rise in the beginning and then descend, with a peak at about 300 nm. The calculated absorption coefficient demonstrates that as-grown films have selective absorption, with a broad transparent range, and possess a big energy gap (4.18 eV).
    Journal of Alloys and Compounds 12/2014; 615:526-530. DOI:10.1016/j.jallcom.2014.06.186 · 2.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have systematically studied the feasibility of CaMnO3 thin film, an n-type perovskite, to be utilized as the buffer layer for hybrid halide perovskite photovoltaic-thermoelectric device. Locations of the conduction band and the valence band, spontaneous polarization performance, and optical properties were investigated. Results indicate the energy band of CaMnO3 can match up well with that of CH3NH3PbI3 on separating electron-hole pairs. In addition, the consistent polarization angle helps enlarge the open circuit voltage of the composite system. Besides, CaMnO3 film shows large absorption coefficient and low extinction coefficient under visible irradiation, demonstrating high carrier concentration, which is beneficial to the current density. More importantly, benign thermoelectric properties enable CaMnO3 film to assimilate phonon vibration from CH3NH3PbI3. All the above features lead to a bright future of CaMnO3 film, which can be a promising candidate as a buffer layer for hybrid halide perovskite photovoltaicthermoelectric systems.
    Journal of Applied Physics 11/2014; 116:194901. DOI:10.1063/1.4901636 · 2.19 Impact Factor
  • Source
    Ceramics International 09/2014; 41(1). DOI:10.1016/j.ceramint.2014.08.094 · 2.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Although lithium ion battery is known to be an excellent renewable energy provider in electronic markets further application of it has been limited by its notoriously poor performance at low temper- ature, especially below ?20 ? C. In this paper, the electrochemical performance of the LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials coated by lithium boron oxide (LBO) glass was investigated at a temperature range from 20 to ?40 ? C. The results show that the LBO coating not only helps to improve the discharge ca- pacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 at room temperature but also increase the discharge capacity retention of the LiNi 1/3 Co 1/3 Mn 1/3 O 2 from 22.5% to 57.8% at ?40 ? C. Electrochemical impedance spectra results reveal that the LBO coating plays an important role in reducing the charge-transfer resistance on the electrolyte eelectrode interfaces and improving lithium ion diffusion coefficients. The mechanism associated with the change of the structure and electrical properties are discussed in detail.
    Journal of Power Sources 08/2014; 277:139-146. DOI:10.1016/j.jpowsour.2014.11.149 · 6.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: LaMnO3 thick films doped with Al were fabricated on Al2O3 substrates by screen printing technique. Significantly composition-dependent structural phase transformation and grain size were observed in Al-doped LMO thick films by X-ray diffraction and scanning electron microscopy. The resistivity of all the thick films decreased with the increase of temperature, indicating a negative temperature coefficient effect. Al doping resulted in a sharp rise in room resistivity (rho(0)) and thermal constant (B) as compared with non-doped films. Among the films investigated, the film with composition x=0.4 showed a unique electrical property and was further examined in detail using the complex impedance analysis, in order to unveil the structure property relationship.
    Ceramics International 08/2014; 40(7-7):10505-10510. DOI:10.1016/j.ceramint.2014.03.022 · 2.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Inorganic-organolead halide perovskite CH3NH3PbI3 modified BiFeO3 polycrystalline film has been established. The composite photoelectrode presents much larger open voltage and several magnitudes superior photoelectric conversion performance in comparison to the ordinary BiFeO3 polycrystalline film. The I-V curve shows that the short-circuit current (Jsc) is 1.74 mA·cm−2 and open-circuit voltage (Voc) is 1.62 V, the device's photon to current efficiency is over 1%. The large open voltage and high photovoltaic efficiency is believed to attributed to the spontaneous polarization of composite perovskite induced by BiFeO3 lattice and modified reduced work function of the modified BiFeO3 surface. Our results clearly show that the present BiFeO3-CH3NH3PbI3 planar device is capable to generate a large voltage in macro scale under visible light, leading an approach to further applications on photodetectors and optoelectronic switch.
    Applied Physics Letters 07/2014; 105(1):013901-013901-5. DOI:10.1063/1.4888912 · 3.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new way to prepare BiFeO3 nano-powders by low-heating temperature solid state precursor method is presented in this paper. Room-temperature solid state reaction was adopted to prepare the precursors, which were further calcined in low-heating temperature at 500°C to synthesize nano-BiFeO3. The particle size of BiFeO3, ranging from 18 to 80 nanometers, can be effectively controlled by different alkali in raw materials. Owing to the quantum size effect, the optical band gaps and magnetic characteristics of BiFeO3 increased with the decreasing particle size.
    Integrated Ferroelectrics 06/2014; 156(1). DOI:10.1080/10584587.2014.906888 · 0.37 Impact Factor

Publication Stats

949 Citations
301.45 Total Impact Points

Institutions

  • 2010–2015
    • Tsinghua University
      • School of Materials Science and Engineering
      Peping, Beijing, China
  • 2007–2015
    • Chinese Academy of Sciences
      Peping, Beijing, China
  • 1996–2015
    • Zhejiang University
      • • Institute of Ecology
      • • State Key Lab of Silicon Materials
      • • State Key Lab of Modern Optical Instrumentation
      • • Department of Management Science and Engineering
      • • School of Management
      Hang-hsien, Zhejiang Sheng, China
  • 2011–2014
    • East China Normal University
      • • Department of Chemistry
      • • Institute of Biomedical Sciences and School of Life Sciences
      Shanghai, Shanghai Shi, China
    • Shandong University of Science and Technology
      Tsingtao, Shandong Sheng, China
    • University of California, Berkeley
      • Department of Environmental Science, Policy, and Management
      Berkeley, California, United States
  • 2013
    • China Academy of Chinese Medical Sciences
      Peping, Beijing, China
  • 2008–2013
    • Beijing Normal University
      • State Key Laboratory of Remote Sensing Sciences
      Peping, Beijing, China
  • 2012
    • Zhejiang Medical University
      Hang-hsien, Zhejiang Sheng, China