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109 results on '"Zheng, Wanquan"'

12. Molecules in interaction with nanoparticles grown on alumina film : the benefits of combined SFG spectroscopy and STM microscopy

Author

Alyabyeva, Natalia, Ghalgaoui, Ahmed, Ouvrard, Aimeric, Carrez, Serge, Zheng, Wanquan, Ouvrard, Aimeric, Laboratoire de Physique de la Matière Condensée (LPMC), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences Moléculaires d'Orsay (ISMO), and Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-OPTICS] Physics [physics]/Physics [physics]/Optics [physics.optics], [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.PHYS.PHYS-ATM-PH] Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], ComputingMilieux_MISCELLANEOUS, [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Abstract

International audience

Published
2020

13. Investigation of defect modes with Al2O3 and TiO2 in one-dimensional photonic crystals

Author

Li Shuhong, Xing Xiao, Wang Wenjun, Gao Xuexi, Zheng Wanquan, Du Qianqian, Zhang Bingyuan, and Zhang Dong

Subjects
Materials science, business.industry, Transfer-matrix method (optics), Physics::Optics, Resonance, 02 engineering and technology, Filter (signal processing), 021001 nanoscience & nanotechnology, 01 natural sciences, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Pulsed laser deposition, 010309 optics, Optics, 0103 physical sciences, Transmittance, Optoelectronics, Electrical and Electronic Engineering, 0210 nano-technology, business, Refractive index, Layer (electronics), Photonic crystal
Abstract

One-dimensional photonic crystal (1D PC) filters with one defect layer are investigated at visible frequencies both theoretically and experimentally. 1D PC filters containing one Al 2 O 3 or TiO 2 defect layer are fabricated by pulsed laser deposition. The optical properties of the filters, including the transmittance and the resonance wavelength, are numerically calculated by using the transfer matrix method. Our results show that the defect layer with the lower refractive index is more suitable for the filters. Both blue- and red- shifts of the filter resonance are observed, depending on the thickness of the defect layer. We also find that the resonance may disappear as the number of periods in the filter increases (with the optical thickness of the defect layer fixed at 3/2 λ .

Published
2016

19. A Spatially Confined gC3N4–Pt Electrocatalyst with Robust Stability

Author

Cheng, Kun, primary, Zhu, Kang, additional, Liu, Shengli, additional, Li, Mengxue, additional, Huang, Jinhua, additional, Yu, Lihuan, additional, Xia, Zhuo, additional, Zhu, Chang, additional, Liu, Xiaobo, additional, Li, Wenhui, additional, Lu, Wangting, additional, Wei, Feng, additional, Zhou, Youhua, additional, Zheng, Wanquan, additional, and Mu, Shichun, additional

Published
2018
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21. Interaction of coadsorbed CH3Cl and D2O layers on Pd(111) studied by sum frequency generation.

Author

Fournier, Frédéric, Dubost, Henri, Carrez, Serge, Zheng, Wanquan, and Bourguignon, Bernard

Subjects
METHYL chloride, FEMTOCHEMISTRY, ADSORPTION (Chemistry), RESONANT vibration, SURFACE chemistry, SPECTRUM analysis
Abstract

Adsorption of methyl chloride and coadsorption of CH3Cl and D2O on Pd(111) surfaces at T=100 K have been studied under ultrahigh-vacuum conditions using femtosecond sum frequency generation (SFG) spectroscopy in the spectral regions of CH and OD bands. On the bare Pd(111) substrate, the CH3Cl coverage dependence of the resonant SFG signal is consistent with a progressive molecular rearrangement starting at half saturation followed by the growth of two ordered monolayers in which the molecular axes are perpendicular to the surface. When CH3Cl is adsorbed on top of predeposited D2O on Pd(111), the SFG signals as a function of the CH3Cl exposure indicate that methyl chloride is adsorbed onto D2O through hydrogen bonding. On the contrary when the adsorption order is reversed the strong decrease of the CH3 signal as a function of the D2O exposure is explained by assuming that water molecules penetrate inside the CH3Cl layers, leading to the formation of disordered CH3Cl clusters. In all cases a nonresonant contribution due to molecular adsorption is observed and it shows a dependence upon surface structure and coverage significantly different from that of the resonant vibrational bands. [ABSTRACT FROM AUTHOR]

Published
2005
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22. Novel cyanoterphenyl self-assembly monolayers on Au(111) studied by ellipsometry, x-ray photoelectron spectroscopy, and vibrational spectroscopies.

Author

Zhang, Hao-Li, Evans, Stephen D., Critchley, Kevin, Fukushima, Hitoshi, Tamaki, Takashi, Fournier, Frédéric, Zheng, Wanquan, Carrez, Serge, Dubost, Henri, and Bourguignon, Bernard

Subjects
ELLIPSOMETRY, SPECTRUM analysis, OPTICAL polarization, MONOMOLECULAR films, ELECTRON spectroscopy, PHOTOELECTRON spectroscopy
Abstract

The self-assembled monolayers (SAMs) of two asymmetric disulfides derivatives (namely, LC1 and LC2) were prepared on Au(111). The disulfides contain a pure alkyl chain and an alkyl chain terminated by a cyanoterphenyl group. LC1 and LC2 differ by the way the cyanoterphenyl group is attached onto the alkyl chain: it is expected to be aligned with the alkyl chain in the case of LC1 and perpendicular to it in the case of LC2 (T shape). The consequences in terms of surface coverage, chemical composition, and molecular conformation of the two SAMs are studied using ellipsometry, x-ray photoelectron spectroscopy (XPS), reflection absorption infrared spectroscopy (RAIRS), and broadband femtosecond sum-frequency generation (SFG). A model of coverage and tilt angle based on ellipsometry and XPS results shows that the SAM “manages” the large size of the terphenyl group by lowering the terphenyl containing chain coverage and by increasing the tilt. In the case of LC2, the disulfide breaks during molecular assembly, less terphenyl chains adsorb than pure alkyl chains, and the overall chain coverage is smaller than for LC1. RAIRS and SFG results show that these differences in surface coverage correspond to a drastically different orientation of the terphenyl axis, which lies nearly parallel to the surface for LC2, while it is tilted by ≈28° for LC1. This shows that the terphenyl group takes much more space on the surface in the case of LC2 and explains why the terphenyl coverage is found smaller for LC2. The anomalous SFG relative intensities observed in the region of CH stretch between CH2 and CH3 modes, and symmetric and antisymmetric modes, show that the chains are not in the fully stretched, all-trans conformation, LC2 being probably more distorted than LC1. These distorsions allow the molecules to occupy the space available below the large terphenyl group. The relative intensities of symmetric and antisymmetric modes are discussed qualitatively for some typical molecular conformations and orientations of the alkyl chain. [ABSTRACT FROM AUTHOR]

Published
2005
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23. Vibrational dynamics of adsorbed molecules under conditions of photodesorption: Pump-probe SFG spectra of CO/Pt(111).

Author

Fournier, Frédéric, Zheng, Wanquan, Carrez, Serge, Dubost, Henri, and Bourguignon, Bernard

Subjects
*SPECTRUM analysis, *PARTICLES (Nuclear physics), *VIBRATIONAL spectra, *LATTICE dynamics, *MOLECULAR spectroscopy, *CATHODE rays
Abstract

Interaction of CO adsorbed on Pt(111) with electrons and phonons is studied experimentally by means of a pump-probe experiment where CO is probed by IR+visible sum frequency generation under a pump laser intensity that allows photodesorption. Vibrational spectra of CO internal stretch are obtained as a function of pump-probe delay. A two-temperature and anharmonic coupling model is used to extract from the spectra the real time variations of CO peak frequency and dephasing time. The main conclusions are the following: (i) The CO stretch is perturbed by two low-frequency modes, assigned to frustrated rotation and frustrated translation. (ii) The frustrated rotation is directly coupled to electrons photoexcited in Pt(111) by the pump laser. (iii) There is no evidence of Pt-CO stretch excitation in the spectra. The implications for the photodesorption dynamics are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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42. Fournieret al.Reply

Author

Fournier, Frédéric, primary, Zheng, Wanquan, additional, Carrez, Serge, additional, Dubost, Henri, additional, and Bourguignon, Bernard, additional

Published
2004
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47. Non-invasive SFG spectroscopy: a tool to reveal the conformational change of grafted chains due to bacterial adhesion

Author

Bulard, Emilie, Dubost, Henri, Fontaine-Aupart, Marie-Pierre, Zheng, Wanquan, Herry, Jean-Marie, Bellon-Fontaine, Marie-Noëlle, Briandet, Romain, and Bourguignon, Bernard

Abstract

In many fields such as biomedical or food industry, surface colonization by micro-organisms leads to biofilms formation that are tridimentional biostructures highly resistant to the action of antimicrobials, by mechanisms still unclear. In order to deepen our understanding of the initial interaction of bacteria cells with a solid surface, we analyze by in situ vibrational Sum Frequency Generation (SFG) spectroscopy the effect of the adhesion of hydrophilic Lactoccocus lactis bacteria and its hydrophobic mutants in distilled water on a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film. When a homogeneous bacterial monolayer is deposited on this ordered surface, SFG spectrum of the ODT SAM shows significant intensity changes from that in air or in water. Its modelling as a function of conformation allows to distinguish optical effects due to the water solution surrounding bacteria from conformational changes of the ODT SAM due to the presence of the bacteria cells. Futhermore, bacterial adhesion induces different measurable effects on the ODT SAM conformation, depending on the hydrophobic / hydrophilic character of the bacterial surface. Such a result deserves to be taken into account for the design of new materials with improved properties or to control biofilm formation.

Published
2011
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48. High Efficiency Electron Transfer Layer based on Ag-Al Co-Doped ZnS in Organic Lighting Emission Devices

Author

He, Xiaoxiao, Wang, Wenjun, Li, Shuhong, Wang, Qingru, Zheng, Wanquan, Shi, Qiang, and Liu, Yunlong

Abstract

Electron transmission improvement in organic light-emitting devices with Ag-Al co-doped ZnS has been demonstrated. The electroluminescence (EL) of device with co-doped ZnS electron transfer layer (ETL) is more than that of devices without ETL and the co-doped ZnS ETL device performs higher EL compared to pure ZnS ETL device. The using of co-doped ZnS can reduce the thickness of ETL from 40 nm to 8 nm and performs comparable efficiency and higher EL. According to the PL spectra studies and current density-voltage characters, the improved electron transmission is attributed to the introduction of impurity energy level and the increased concentration of electron.

Published
2015

50. The Effect of Bacterial Adhesion on Grafted Chains Revealed by the Non-Invasive Sum Frequency Generation Spectroscopy

Author

Bulard, Emilie, Fontaine-Aupart, Marie-Pierre, Dubost, Henri, Zheng, Wanquan, Herry, Jean-Marie, Bellon-Fontaine, Marie-Noëlle, Briandet, Romain, and Bourguignon, Bernard

Abstract

In biomedical and food industry, surface colonization by bacteria is harmful: it leads to biofilm formation, a microbial consortia more resistant to antibiotics than planktonic bacteria. In order to design materials able to limit the biofilm formation, the effect of bacteria on materials has to be well characterized. In this work, a well-defined surface composed of a self-assembled monolayer (SAM) of octadecanethiol (ODT) onto a gold surface is probed in situ. The SAM conformation is obtained using the femtosecond vibrational sum frequency generation (SFG) spectroscopy. This technique provides selectively the molecular vibrational signature of the interface. The behaviour of the ODT SAM is studied in different environments: in air, in water, and upon exposure to hydrophilic or hydrophobic Lactococcus lactis bacteria. Modelling the experimental SFG spectra reveals a measurable change of the SAM conformation which depends on the environment, especially on the hydrophilic-hydrophobic character.

Published
2012
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