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1.
  • Beal, Jacob, et al. (författare)
  • Robust estimation of bacterial cell count from optical density
  • 2020
  • Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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2.
  • Chen, Ruikui, et al. (författare)
  • Photoinduced intramolecular charge-transfer state in thiophene-π-conjugated donor-acceptor molecules.
  • 2008
  • Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 876:1-3, s. 102-109
  • Tidskriftsartikel (refereegranskat)abstract
    • Novel thiophene-π-conjugated donor-acceptor mols., 5-[2-(1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)-vinyl]-thiophene-2-carbaldehyde (QTC) and (1-cyano-2-{5-[2-(1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)-vinyl]-thiophen-2-yl}-vinyl)-phosphonic acid di-Et ester (QTCP), were designed and synthesized. Combined exptl. and theor. methods were performed to investigate the photoinduced intramol. charge-transfer (ICT) processes of these compds. Steady-state absorption and fluorescence measurements in different solvents indicate the photoinduced ICT characters of QTC and QTCP. Solvent dependency of the large Stokes shifts and high dipole moment of the excited state also support the charge-transfer character of the excited state. Theor. calcns. based on time-dependent d. functional theory (TDDFT) method were performed to investigate ICT states of these compds. The results reveal that the excited states have adopted a distortion of the C=C double bond between the donor moiety and the thiophene-π-bridge. [on SciFinder(R)]
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3.
  • Dong, Bin, et al. (författare)
  • Experimental and theoretical evidence for the chemical mechanism in SERRS of rhodamine 6G adsorbed on colloidal silver excited at 1064 nm
  • 2010
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 41:7, s. 719-720
  • Tidskriftsartikel (refereegranskat)abstract
    • The evidence for the existence of a chemical mechanism in surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) adsorbed on colloidal silver excited at 1064 nm is reported on the basis of experimental and theoretical analyses. A weak absorption peak at around 1060 nm for R6G-functionalized silver nanoparticles was observed, which is not present in the individual spectra of R6G or silver nanoparticles. Theoretically, the charge difference density reveals that this weak absorption is a metal-to-molecule charge transfer excited state. Copyright (C) 2010 John Wiley & Sons, Ltd.
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4.
  • Dong, Bin, et al. (författare)
  • Is 4-nitrobenzenethiol converted to p,p '-dimercaptoazobenzene or 4-aminothiophenol by surface photochemistry reaction?
  • 2011
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 42:6, s. 1205-1206
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, the experimental and theoretical evidence for the conversion of 4-nitrobenzenethiol (4-NBT) to p,p'-dimercaptoazobenzene (DMAB) in Ag and Cu sols by surface photochemistry reaction is obtained with surface-enhanced Raman scattering (SERS) spectroscopy. The SERS spectrum of 4-NBT in Cu sol is identical to that of DMAB produced from 4-aminothiophenol in Ag sol as reported in recent literature, thereby providing direct spectral evidence. Copyright (C) 2011 John Wiley & Sons, Ltd.
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5.
  • Dong, Bin, et al. (författare)
  • Local and Remote Charge-Transfer-Enhanced Raman Scattering on One-Dimensional Transition-Metal Oxides
  • 2010
  • Ingår i: Chemistry - An Asian Journal. - : Wiley. - 1861-4728. ; 5:8, s. 1824-1829
  • Tidskriftsartikel (refereegranskat)abstract
    • The one-dimensional (1D) transition-metal oxide MoO3 belt is synthesized and characterized with Xray diffraction, scanning electron microscopy, and Raman spectroscopy. Charge-transfer-(CT) enhanced Raman scattering of 4-mercaptobenzoic acid (4-MBA) on a 1D MoO3 belt was investigated experimentally and theoretically. The chemical enhancement of surface-enhanced Raman scattering (SERS) of 4-MBA on the MoO3 belt by CT is in the order of 10(3). The SERS of 4-MBA was investigated theoretically by using a quantum chemical method. The remote SERS of 4-MBA along the 1D MoO3 belt (the light excitation to one side of the MoO3 belt, and the SERS spectrum is collected on the other side of the MoO3 belt) is also shown experimentally, which provides potential applications of SERS. The incident polarization dependence of remote SERS spectra has also been investigated experimentally.
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6.
  • Dong, Bin, et al. (författare)
  • Substrate-, Wavelength-, and Time-Dependent Plasmon-Assisted Surface Catalysis Reaction of 4-Nitrobenzenethiol Dimerizing to p,p '-Dimercaptoazobenzene on Au, Ag, and Cu Films
  • 2011
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:17, s. 10677-10682
  • Tidskriftsartikel (refereegranskat)abstract
    • In this article, we experimentally investigate the substrate, wavelength, and time dependence of the plasmon-assisted surface-catalyzed dimerization of 4-nitrobenzenethiol to form p,p'-dimercaptoazobenzene on Au, Ag, and Cu films. We provide direct experimental evidence that surface plasmon resonance plays the most important role in these surface-catalyzed reactions. It is found that the reaction is strongly dependent on the substrate, the wavelength of the laser, and the reaction timescales. Our experimental results revealed that optimal experimental conditions can be rationally chosen to control (accelerate or restrain) this reaction. The experimental results are also confirmed by theoretical calculations.
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7.
  • Fang, Yurui, et al. (författare)
  • Ascertaining p,p '-Dimercaptoazobenzene Produced from p-Aminothiophenol by Selective Catalytic Coupling Reaction on Silver Nanoparticles
  • 2010
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:11, s. 7737-7746
  • Tidskriftsartikel (refereegranskat)abstract
    • Combining experiment and theory, evidence from surface-enhanced Raman scattering (SERS) were obtained for p,p'-dimercaptoazobenzene (DMAB) produced from p-aminothiophenol (PATP) by selective catalytic coupling reaction on silver nanoparticles. The time-dependent SERS spectra of PATE are consistent with the calculated SERS spectra of DMAB), which is the direct evidence or the production of DMAB from PATE by selective catalytic coupling reaction on silver nanoparticles. The so-called "b(2) modes" of PATP is the -N=N- related vibrational modes of DMAB. The silver nanoparticles could be assembled together to form different size of aggregates with different concentration of PATE solution. When the concentration of Ag nanoparticle (the radius 40 nm) in colloid is 35 pM, the time-dependent SERS of DMA B reveals that the better experimental conditions for observing SERS signals of DMA B are (1) concentration of PATE is around 5 x 0(-6) M in which condition the aggregates consist with about 3-5 silver nanoparticles. which are not too big and suitable for SERS measurement, and (2) the Raman signal will be strongest at the thne delay about 27 min for this concentration. By analyzing the symmetry of strong enhanced vibrational modes, it is derived that all ask strong vibrational modes are mostly enhanced by surface plasmons (electromagnetic field). The SERS enhancement calculated with finite-difference time-domain method is on the order of |M|(4) = 9.0 x 10(8) in junctions of AgNPs at 632.8 nm, where |M|(4) = E-loc/E-in and E-loc and E-in are local and incident electric fields, respectively. The total chemical enhancements, including static chemical and resonant enhancements, are on the order of 10(3).
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8.
  • Jin, Yuepeng, et al. (författare)
  • Involvement of the PI3K/Akt/NF- B Signaling Pathway in the Attenuation of Severe Acute Pancreatitis-Associated Acute Lung Injury by Sedum sarmentosum Bunge Extract
  • 2017
  • Ingår i: BioMed Research International. - : Hindawi Limited. - 2314-6133 .- 2314-6141. ; 2017
  • Tidskriftsartikel (refereegranskat)abstract
    • Sedum sarmentosum Bunge possesses excellent anti-inflammatory properties and was used in the treatment of inflammatory diseases. The aim of the present study was to investigate the efficiency of Sedum sarmentosum Bunge extract (SSBE) on severe acute pancreatitis-associated (SAP-associated) acute lung injury (ALI) in rats and to explore the underlying mechanisms. Here, we used a sodium taurocholate-induced SAP rat model to determine the role of SSBE in ALI. During the course of pancreatitis, the expressions of phosphorylated phosphoinositide 3-kinases (PI3K)/protein kinase B (Akt) and nuclear factor-kappa B (NF-B) p65 in the lungs were upregulated. Meanwhile, a parallel increase in the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor- (TNF-) in the lungs was observed after the induction of SAP. Treatment with SSBE significantly reduced the expression of p-Akt and p-p65 in the lungs and attenuated the severity of SAP-associated ALI compared to the SAP group at 12 h and 24 h. In summary, this study showed that SSBE has beneficial effects on SAP-associated ALI, probably through the PI3-K/Akt signaling pathways by suppressing the NF-B activities.
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9.
  • Li, Yuanzuo, et al. (författare)
  • Theoretical Characterization of the PC60BM:PDDTT Model for an Organic Solar Cell
  • 2011
  • Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:44, s. 21865-21873
  • Tidskriftsartikel (refereegranskat)abstract
    • We use time-dependent density functional theory together with a set of extensive multidimensional visualization techniques to characterize band gap, optical absorption properties, intramolecular and intern-wreaths charge transfer, exciton binding energy, charge transfer integral, and the rate of charge transfer and recombination in the PC60BM:PDDTT Model of an organic,solar cell. These theoretical methods and calculation techniques only promote deeper understanding of the connection between chemical structures and the optical and electronic properties Of the donor-acceptor system but also can be used to rational design novel donor-acceptor system.
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10.
  • Lin, Weihua, et al. (författare)
  • Physical mechanism on exciton-plasmon coupling revealed by femtosecond pump-probe transient absorption spectroscopy.
  • 2017
  • Ingår i: Materials Today Physics. - : Elsevier BV. - 2542-5293. ; 3, s. 33-40
  • Tidskriftsartikel (refereegranskat)abstract
    • The unclear mechanism of exciton-plasmon coupling interaction in monolayer MoS2-Ag nanoparticles hybrid, as a longstanding target in molecular nanotechnology and catalysis, is systemically investigated with transmission spectra and femtosecond pump-probe transient absorption spectroscopy in this paper. The properties of exciton in monolayer MoS2 are strongly enhanced due to the local surface plasmon resonance (LSPR) induced by Ag nanoparticles, and manifested by obvious changes in transmission spectra. Furthermore, we discuss the dynamic processes of exciton-plasmon coupling interaction with the femtosecond transient absorption spectroscopy, which indicates that there are three lifetimes, Auger scattering, electron-electron interaction and electron-phonon interaction, and illustrate the reason of the enlarged lifetime in hybrid system. Meanwhile, the intensity of A excitonic state in femtosecond transient absorption spectroscopy is significantly enhanced by LSPR, instead of excitonic state B. In conclusion, our study can promote the deeper understanding and illustrate the unique merits of the exciton-plasmon coupling interaction in the monolayer MoS2-Ag nanoparticles hybrid system.
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11.
  • Lv, Wanzhi, et al. (författare)
  • Lipoxin A4 attenuation of endothelial inflammation response mimicking pancreatitis-induced lung injury
  • 2013
  • Ingår i: Experimental Biology and Medicine. - : SAGE Publications. - 1535-3702 .- 1535-3699. ; 238:12, s. 1388-1395
  • Tidskriftsartikel (refereegranskat)abstract
    • Lipoxins (LXs) and their analogues are known to display potent anti-inflammatory actions. Previously, we reported that lipoxin A4 (LXA4) possessed powerful anti-inflammatory properties in acute pancreatitis in rats and that it may ameliorate the concomitant acute lung injury by reducing cytokine generation and inhibiting neutrophil activation. Considering that the vascular endothelium plays an important role during adherence, migration and activation of leukocytes, the present study was designed to investigate the effects of LXA4 on the inflammatory response induced by tumor necrosis factor a (TNF-alpha) in human pulmonary microvascular endothelial cells (HPMECs) and explore the potential mechanisms involved in these processes. We found that LXA4 markedly down-regulated the expression of monocyte chemotactic protein-1 (MCP-1), E-selectin, and interleukin-6 (IL-6) mRNA, as well as intercellular adhesion molecule-1 (ICAM-1) in TNF-alpha-exposed HPMECs. Moreover, LXA4 inhibited the phosphorylation and nuclear translocation of nuclear factor-kappa B/p65 (NF-kappa B/p65) and phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) in HPMECs following TNF-alpha stimulation. Heme oxygenase-1 (HO-1), a cytoprotective enzyme, was up-regulated by LXA4 in both non- and TNF-alpha-stimulated HPMECs. In conclusion, the protective effects of LXA4 to ALI may be executed through inhibition inflammation pathways of NF-kappa B and p38 MAPK and up-regulation of cytoprotective HO-1.
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12.
  • Persson, Nils-Krister, et al. (författare)
  • Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices
  • 2005
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 123:20, s. 204718-
  • Tidskriftsartikel (refereegranskat)abstract
    • In a joint experimental and theoretical work the optical response and excited-state character of two novel conjugated polymers for photovoltaic applications are studied. The polymers, alternating polyfluorene (APFO) Green 1 and APFO Green 2, are both copolymers of fluorene, thiophene, and electron accepting groups. The band gaps are extended into the red and near infrared with onsets of 780 and 1000 nm, respectively, due to alternating donor and acceptor moieties along the polymer chain. Spectroscopic ellipsometry and subsequent modeling made it possible to extract the dielectric function in the range of 260-1200 nm. Semiempirical quantum chemical calculations (ZINDO) revealed the character of the main electronic transitions in the studied spectral region. The spectral band just above 400 nm was assigned to a delocalized π - π* transition for both polymers. The red band lying at 622 and 767 nm in the two polymers corresponds to an electronic state mainly occupying the acceptor units and having a strong charge-transfer character. We show that the ZINDO transition energies are valuable input to the application of Lorentz oscillators in modeling of the dielectric function of the polymer material.
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13.
  • Song, Peng, et al. (författare)
  • External Electric Field-Dependent Photoinduced Charge Transfer in a Donor-Acceptor System for an Organic Solar Cell
  • 2013
  • Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:31, s. 15879-15889
  • Tidskriftsartikel (refereegranskat)abstract
    • External electric field is incorporated into the generalized Mulliken-Hush model and Marcus theory. With this new development, we have investigated the field-dependent electronic structure and rate of photoinduced charge transfer in organic donor-acceptor dyad using time-dependent density functional theory and extensive multidimensional visualization techniques. The model is used to evaluate the influence of the external electric field on the electronic coupling between donor and acceptor. The reorganization energy and the free energy change of the electron transfer were calculated. It was found that the major effects in the external electric field dependent rate of the charge transfer originate from changes in the electronic coupling. The new theoretical approach not only promotes a deeper understanding of the connection between the external electric field, chemical structure, and optical and electronic properties of the donor-acceptor system, but also can be used for rational design of novel donor-acceptor system for organic solar cells.
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14.
  • Song, Peng, et al. (författare)
  • Photoinduced Electron Transfer in Organic Solar Cells.
  • 2016
  • Ingår i: The Chemical Record. - : Wiley. - 1527-8999.
  • Tidskriftsartikel (refereegranskat)abstract
    • Electron transfer (ET) is the key process in light-driven charge separation reactions in organic solar cells. The current review summarizes the progress in theoretical modelling of ET in these materials. First we give an account of ET, with a description originating from Marcus theory. We systematically go through all the relevant parameters and show how they depend on different material properties, and discuss the consequences such dependencies have for the performance of the devices. Finally, we present a set of visualization methods which have proven to be very useful in analyzing the elementary processes in absorption and charge separation events. Such visualization tools help us to understand the properties of the photochemical and photobiological systems in solar cells.
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15.
  • Sun, Mengtao, et al. (författare)
  • A Novel Application of Plasmonics: Plasmon-Driven Surface-Catalyzed Reactions
  • 2012
  • Ingår i: Small. - : Wiley. - 1613-6829 .- 1613-6810. ; 8:18, s. 2777-2786
  • Forskningsöversikt (refereegranskat)abstract
    • The first experimental and theoretical evidence of the surface-catalyzed reaction of p,p'-dimercaptoazobenzene (DMAB) produced from para-aminothiophenol (PATP) by local surface plasmons was reported in 2010, and since that time a series of investigations have supported these findings using different experimental and theoretical methods. Recent work has also found that local plasmons can drive a surface-catalyzed reaction of DMAB converted from 4-nitrobenzenethiol (4NBT), assisted by local surface plasmons. There are at least three important discoveries in these investigations: 1) in the field of surface-enhanced Raman scattering (SERS) the widely accepted misinterpretation (since 1994) that the chemical mechanism resulting in three additional Raman peaks of PATP in Ag or Au solutions has been corrected with a new mechanism; 2) it is confirmed that SERS is not always a noninvasive technique, and under certain conditions cannot always obtain the vibrational fingerprint information of the original surface species; 3) a novel method to synthesize new molecules, induced by local surface plasmons or plasmon waveguides on the nanoscale, has been found. This Review considers recent novel applications of plasmonics to chemical reactions, especially to plasmon-driven surface-catalyzed reactions.
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16.
  • Sun, Mengtao, et al. (författare)
  • Activated vibrational modes and Fermi resonance in tip-enhanced Raman spectroscopy
  • 2013
  • Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 87:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Using p-aminothiophenol (PATP) molecules on a gold substrate and high-vacuum tip-enhanced Raman spectroscopy (HV-TERS), we show that the vibrational spectra of these molecules are distinctly different from those in typical surface-enhanced Raman spectroscopy. Detailed first-principles calculations help to assign the Raman peaks in the TERS measurements as Raman-active and IR-active vibrational modes of dimercaptoazobenzene (DMAB), providing strong spectroscopic evidence for the dimerization of PATP molecules to DMAB under the TERS setup. The activation of the IR-active modes is due to enhanced electromagnetic field gradient effects within the gap region of the highly asymmetric tip-surface geometry. Fermi resonances are also observed in HV-TERS. These findings help to broaden the versatility of TERS as a promising technique for ultrasensitive molecular spectroscopy. DOI:10.1103/PhysRevE.87.020401
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17.
  • Sun, Mengtao, et al. (författare)
  • Can information of chemical reaction propagate with plasmonic waveguide and be detected at remote terminal of nanowire?
  • 2011
  • Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 3:10, s. 4114-4116
  • Tidskriftsartikel (refereegranskat)abstract
    • We attempt to provide experimental and theoretical evidence that information of chemical reaction can propagate with plasmonic waveguide along the nanowire and be detected at the remote terminal of nanowire, where the chemical reaction is the surface catalyzed reaction of DMAB produced from PATP assisted by surface plasmon polaritons.
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18.
  • Sun, Mengtao, et al. (författare)
  • Charge and energy transfer in binaphthalene molecule with two spiropyran units used for chiral molecular switches and logic gates
  • 2006
  • Ingår i: Journal of Theoretical & Computational Chemistry. - 0219-6336. ; 5:2, s. 163-174
  • Tidskriftsartikel (refereegranskat)abstract
    • A new binaphthalene molecule with two spiropyran units used for chiral molecular switches and logic gates was synthesized and chaxacterized.(12) In this paper, charge and energy transfer in binaphthalene molecule with two spiropyran units are theoretically investigated with quantum chemistry method, as well as 2D and 3D real space analysis methods, since molecule construction with photoinduced electron transfer or charge transfer is one of the most frequently used pathways for building useful sensors and molecular machines. The orientation and strength of transition dipole moment in absorption spectra are obtained by 3D transition density. The orientation and results of intramolecular charge transfer on the excitation are obtained with 3D charge difference densities. The electron-hole coherence and excitation delocalization in absorption spectra are investigated with 2D contour plots of transition density matrix. Overall, the computed results remain in good agreement with the relevant experimental data, and the theoretical results reveal the relationship between the function of sensor and the excited state properties of the structure and transformation of the compound, upon addition of acid and base in absorption spectra.
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19.
  • Sun, Mengtao (författare)
  • Charge transfer state induced from locally excited state by polar solvent
  • 2005
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 408:1-3, s. 128-133
  • Tidskriftsartikel (refereegranskat)abstract
    • The photophysical properties of the novel perylene imide (Pi) and oligo-pentaphenyl bisfluorene (pPh) containing molecule have been investigated by quantum chemical methods. It is concluded that the first excited singlet state in the gas is the locally excited state; while the lowest excited state in polar solvents is the intramolecular charge transfer (ICT) state, which corresponds to the ICT from pPh to Pi. This excited state in the polar solvent adopts a planar geometry, in marked contrast to the twisted geometry in the gas phase. The planar geometry in the polar solvent significantly delocalized densities of HOMOs, compared to those in the gas phase, but the influence of the planar geometry to densities of LUMO is very small. Overall, the computed results remain in good agreement with the relevant experimental data. (c) 2005 Elsevier B.V. All rights reserved.
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20.
  • Sun, Mengtao, et al. (författare)
  • Chemical and electromagnetic mechanisms of tip-enhanced Raman scattering
  • 2009
  • Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 11:41, s. 9412-9419
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we attempt to reveal the nature of the chemical and electromagnetic mechanisms of tip-enhanced Raman scattering (TERS). Direct visual evidence regarding the chemical mechanism via charge transfer was obtained with charge difference density. It is found that there are several kinds of charge transfer: (1) tip to molecule, (2) surface to molecule, (3) tip and surface to molecule simultaneously, and (4) tunneling charge transfer between the tip and the surface. Direct evidence regarding the electromagnetic mechanism via intracluster (tip or surface) charge redistribution was also revealed via charge difference density. The distance (between tip and surface) dependence of the near electric field distribution and the TERS enhancement at different incident lights is also discussed using the three-dimensional finite-difference time-domain (FDTD) method. The electromagnetic enhancement of double-tip TERS is approximately 10 times larger than that of conventional TERS. Theoretical results reveal that plasmon coupling effects between the metal tip and surface play an important role in TERS.
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21.
  • Sun, Mengtao, et al. (författare)
  • Chemical mechanism of surface-enhanced resonance Raman scattering via charge transfer in pyridine-Ag-2 complex
  • 2008
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 39:3, s. 402-408
  • Tidskriftsartikel (refereegranskat)abstract
    • A theoretical model is presented to describe the chemical mechanism of surface-enhanced resonance Raman scattering (SERRS) via charge transfer (CT) in the pyridine-Ag-2 complex. We first describe the influence of the interaction between the metal cluster and pyridine to the ground-state properties of the pyridine-Ag-2 complex, such as charge redistribution, the change of the atomic-resolved density of state, and the change of energy levels of occupied and unoccupied molecular orbitals. Second, we visualize the CT between the metal cluster and pyridine and within the intracluster on the electronic state transitions with charge difference density. The CT between the metal cluster and pyridine is the direct evidence of chemical mechanism for SERRS. Third, the spectra of SERRS are calculated with different incident light wavelengths that resonate with the different electronic state energy levels, and the enhanced intensities of different vibrational modes are compared, which show that there are different enhancement rates for different vibrational modes. Strong Raman scattering can be achieved not only by the CT between pyridine and the metal cluster but also by electronic intracluster excitation via a type of Forster excitation transfer, and the latter results from the local field effects by collective plasmons. The selection rules for the SERRS have been obtained for these two types of enhanced mechanisms. Copyright (C) 2008 John Wiley & Sons, Ltd.
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22.
  • Sun, Mengtao, et al. (författare)
  • Comparison of the electronic structure of PPV and its derivative DIOXA-PPV
  • 2006
  • Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 327:2-3, s. 474-484
  • Tidskriftsartikel (refereegranskat)abstract
    • Electronic structure of two conjugated polymers, PPV and its derivative DIOXA-PPV, are studied by quantum-chemistry methods. Good agreement between the calculations and available experimental data validates the applied methods and enables us to draw conclusions about properties of excitons and polarons in these polymers. In particular, simultaneous use of different correlation plots in atomic site representation and transition densities in real space representation reveals electronic structure and spatial localization of the elementary excitations. The properties of the DIOXA-PPV are discussed in context of possible applications in molecular electronics devices. (c) 2006 Elsevier B.V. All rights reserved.
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23.
  • Sun, Mengtao, et al. (författare)
  • Control of emission by intermolecular fluorescence resonance energy transfer and intermolecular charge transfer
  • 2006
  • Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 110:19, s. 6324-6328
  • Tidskriftsartikel (refereegranskat)abstract
    • Control of emission by intermolecular fluorescence resonant energy transfer (IFRET) and intermolecular charge transfer (ICT) is investigated with the quantum-chemistry method using two-dimensional (2D) and three-dimensional (3D) real space analysis methods. The work is based on the experiment of tunable emission from doped 1,3,5-triphenyl-2-pyrazoline (TPP) organic nanoparticles (Peng, A. D.; et al. AdV. Mater. 2005, 17, 2070). First, the excited-state properties of the molecules, which are studied (TPP and DCM) in that experiment, are investigated theoretically. The results of the 2D site representation reveal the electron-hole coherence and delocalization size on the excitation. The results of 3D cube representation analysis reveal the orientation and strength of the transition dipole moments and intramolecular or intermolecular charge transfer. Second, the photochemical quenching mechanism via IFRET is studied (here "resonance" means that the absorption spectrum of TPP overlaps with the fluorescence emission spectrum of DCM in the doping system) by comparing the orbital energies of the HOMO (highest occupied molecular orbital) and the LUMO (lowest unoccupied molecular orbital) of DCM and TPP in absorption and fluorescence. Third, for the DCM-TPP complex, the nonphotochemical quenching mechanism via ICT is investigated. The theoretical results show that the energetically lowest ICT state corresponds to a pure HOMO-LUMO transition, where the densities of the HOMO and LUMO are strictly located on the DCM and TPP moieties, respectively. Thus, the lowest ICT state corresponds to an excitation of an electron from the HOMO of DCM to the LUMO of TPP.
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24.
  • Sun, Mengtao (författare)
  • Control of structure and photophysical properties by protonation and subsequent intramolecular hydrogen bonding
  • 2006
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 124:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Protonation and subsequent intramolecular hydrogen bonding as methods to control chain structure and tune luminescence in heteroatomic conjugated polymers were reported experimentally [A. P. Monkman , J. Am. Chem. Soc. 124, 6049 (2002)]. In this paper, the structure and photophysical properties of the model teraryl compound of phenylene-pyridylene copolymer before and after protonation are theoretically studied with quantum chemistry methods. From the optimized ground states, intramolecular hydrogen bonding to the adjacent oxygen atom in the alkoxy substituent planarizes the backbone of the molecules, and the optimized detailed results of compound 9 before and after protonation, such as the dihedral angles between the central benzene and the two pyridyl rings, the bond lengths, and the bond angles, are consistent with the experimental results. From the results of the calculated excited states, the protonation and subsequent intramolecular hydrogen bonding result in the redshifts of the absorption, the increase of the ionization energy, the increase of the electron affinity, the decrease of the energy difference of the highest occupied molecular orbital and lowest unoccupied molecular orbital, the decrease of the binding gap, and the delocalization of the electron-hole coherence. The photophysical properties of compound 9 before and after protonation are further studied with a three-dimensional real-space analysis method of transition and charge difference densities (study transition dipole moment and charge transfer in the absorption and fluorescence processes) and two-dimensional real-space analysis method of transition density matrices (study the electron-hole coherence and the excitation delocalization). The calculated results show theoretically an insight understanding on the influence of the protonation and subsequent intramolecular hydrogen bonding to chain structure and photophysical properties. (c) 2006 American Institute of Physics.
  •  
25.
  • Sun, Mengtao, et al. (författare)
  • Direct visual evidence for chemical mechanisms of SERRS via charge transfer in Au-20-pyrazine-Au-20 junction
  • 2009
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 40:12, s. 1942-1948
  • Tidskriftsartikel (refereegranskat)abstract
    • The essence of the chemical mechanism for surface-enhanced resonance Raman scattering (SERRS) is the charge transfer (CT) between the metal and the molecule at the resonant electronic transition, which results in the mode-selective enhancement in the SERRS spectrum. The site-orientated CT can directly interpret the mode-selective chemical enhancement in SERRS. However, it is a great challenge to intutively visualize the orientation and site of the CT. In this paper, for the pyrazine-Au-2 complex, a three-dimensional [3D) cubic representation is built to provide direct visual evidence for chemical mechanisms of SERRS via CT from the Au-2 cluster to pyrazine at the resonant electronic transition. The relationship between the mode-selective enhancements in SERRS and the site-orientated CT was clearly revealed. The intracluster excitation (analog of plasmon excitation in large naonoparticles) was also visualized by the 3D cubic presentation, which provided the direct evidence of local electromagnetic field enhancement of SERRS. To study the quantum size effect and the coupling effect of the nanoparticles, the photoexcitation mechanisms of the Au-20 - pyrazine complex and the Au-20 - pyrazine - Au-20 junction were also investigated. The tunneling charge transfer from one Au-20 cluster to another Au-20 cluster outside the pyrazine in Au-20 - pyrazine - Au-20 junction was also revealed visually. The calculated normalized extinction spectra of Au nanoparticles using the generalized Mie theory reveal that the resonance peak is red-shifted due to the coupling between particles. Copyright (C) 2009 John Wiley & Sons, Ltd.
  •  
26.
  • Sun, Mengtao, et al. (författare)
  • Direct visual evidence for quinoidal charge delocalization in poly-p-phenylene cation radical
  • 2007
  • Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 111:46, s. 13266-13270
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, X-ray crystallographic evidence of quinoidal charge delocalization in poly-p-phenylene cation radicals was reported [Banerjee, M. et al., J. Am. Chem. Soc. 2007, 129, 8070]. In this paper, direct visual evidence for quinoidal charge delocalization in quaterphylene (QP) is shown with three-dimensional (31)) charge difference densities. It was revealed that the extra positive charge mainly localized on the two center units at the ground state, while the extra positive charge will delocalize to the two outer units upon electronic state transitions by photoexcitation. The 2D plots together with the corresponding charge difference densities were interpreted as large distance-charge oscillations, implying that in the positive species upon excitation a nearly free oscillating motion of a hole occurs. For the QP cation radical,the transition dipole moment of S I represents mesoscopic dipole antennae.
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27.
  • Sun, Mengtao, et al. (författare)
  • Direct visual evidence for the chemical mechanism of surface-enhanced resonance Raman scattering via charge transfer
  • 2009
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 40:2, s. 137-143
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe the chemical and electromagnetic enhancements of surface-enhanced resonance Raman scattering (SERRS) for the pyridine molecule absorbed on silver clusters, in which different incident wavelength regions are dominated by different enhancement mechanisms. Through visualization we theoretically investigate the charge transfer (CT) between the molecule and the metal cluster, and the charge redistribution (CR) within the metal on the electronic intracluster collective oscillation excitation (EICOE). The CT between the metal and the molecule in the molecule-metal complex is considered as an evidence for chemical enhancement to SERRS. CR within the metal on EICOE is considered as an evidence for the electromagnetic enhancement by collective plasmons. For the incident wavelength from 300 to 1000 nm, the visualized method of charge difference density can classify the different wavelength regions for chemical and electromagnetic enhancement, which are consistent with the formal fragmented experimental studies. Copyright (C) 2008 John Wiley & Sons, Ltd.
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28.
  • Sun, Mengtao, et al. (författare)
  • Direct visual evidence for the chemical mechanism of surface-enhanced resonance Raman scattering via charge transfer: (II) Binding-site and quantum-size effects
  • 2009
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 40:9, s. 1172-1177
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe quantum-size and binding-site effects on the chemical and local field enhancement mechanisms of surface-enhanced resonance Raman scattering (SERRS), in which the pyridine molecule is adsorbed on one of the vertices of the Ag-20 tetrahedron. We first investigated the influence of the binding site on normal Raman scattering (NRS) and excited state properties of optical absorption spectroscopy. Second, we investigated the quantum-size effect on the electromagnetic (EM) and chemical mechanism from 300 to 1000 nm with charge difference density. It is found that the strong absorption at around 350 nm is mainly the charge transfer (CT) excitation (CT between the molecule and the silver cluster) for large clusters, which is the direct evidence for the chemical enhancement mechanism for SERRS; for a small cluster the strong absorption around 350 nm is mainly intracluster excitation, which is the direct evidence for the EM enhancement mechanism. This conclusion is further confirmed with the general Mie theory. The plasmon peak in EM enhancement will be red-shifted with the increase of cluster size. The influence of the binding site and quantum-size effects on NRS, as well as chemical and EM enhancement mechanisms on SERRS, is significant. Copyright (C) 2009 John Wiley & Sons, Ltd.
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29.
  • Sun, Mengtao, et al. (författare)
  • Direct Visualization of the Chemical Mechanism in SERRS of 4-Aminothiophenol/Metal Complexes and Metal/4-Aminothiophenol/Metal Junctions
  • 2009
  • Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 10:2, s. 392-399
  • Tidskriftsartikel (refereegranskat)abstract
    • We theoretically investigate the mechanism of chemical enhancement of surface-enhanced resonance Roman scattering (SERRS) of para-aminothiophenol (PATP)/metal complexes and metal/PATP/metal junctions. The method of charge difference density is used to visualize intracluster excitation and charge transfer (CT) between PATP and metal during the process of resonant electronic transitions. It is found that the selective enhancement of the b(2) mode in SERRS spectra result not only from Albrecht's A term (the Frank-Condon term), but also from the Herzberg-Teller term (Albrecht's B mechanism) via resonant CT For the metal/PATP/metal junctions, the calculated results reveal that the Roman spectrum is of SERRS nature and the nontotally symmetric b(2) mode is strongly enhanced at the incident wavelength of 1064 nm when Au and Ag nanoparticles are the first and second layer, respectively, and the dominant enhancement mechanism is the Herzberg-Teller term in chemical enhancement via tunneling charge transfer (intervalence electron transfer from the Ag cluster to the Au cluster). When the first and second layers were inverted (i.e. the Ag and Au nanoparticles are the first and second layers, respectively), the Roman spectrum at on incident wavelength of 1064 nm is due to normal Roman scattering, and the nontotally symmetric b(2) mode is not strongly enhanced. Our theoretical results not only support the experimental findings, but also provide a clear physical interpretation.
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30.
  • Sun, Mengtao, et al. (författare)
  • Do coupling exciton and oscillation of electron-hole pair exist in neutral and charged pi-dimeric quinquethiophenes?
  • 2007
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical physical properties of neutral and charged quinquethiophene monomer, and neutral and cationic pi-dimeric quinquethiophenes were investigated with density functional theory as well as the two dimensional (2D) site (transition density matrix) and three dimensional (3D) cube (transition density and charge difference density) representations, stimulated by the recent experimental report [T. Sakai , J. Am. Chem. Soc. 127, 8082 (2005)]. Transition density shows the orientation and strength of the transition dipole moment of neutral and charged quinquethiophene monomer, and charge difference density reveals the orientation and result of the charge transfer in neutral and charged quinquethiophene monomer. To study if coupling exciton and oscillation of electron-hole pair exist in neutral and cationic pi-dimeric quinquethiophenes, the coupling constants J (coupling exciton of electron-hole pair) and K (coupling oscillation of electron-hole pair) were introduced to the exciton coordinate and momentum operators, respectively, and the 2D and 3D analysis methods were further developed by extending our previous theoretical methods [M. T. Sun, J. Chem. Phys. 124, 054903 (2006)]. With the new developed 2D and 3D analysis methods, we investigated the excited state properties of neutral and cationic pi-dimeric quinquethiophenes, especially on the coupling exciton and oscillation of electron-hole pair between monomers. The 2D results show that there is neither coupling exciton (J=0) nor oscillation (K=0) of electron-hole pair in neutral pi-dimeric quinquethiophenes. For some excited states of cationic pi-dimeric quinquethiophenes, there is no coupling exciton (J=0), but there is coupling oscillation (K not equal 0); while for some excited states, there are both coupling exciton and coupling oscillator simultaneously (J not equal 0 and K not equal 0). The strength of transition dipole moments of pi-dimeric quinquethiophenes were interpreted with 3D transition density, which reveals the orientations of their two subtransition dipole moments. The 3D charge transition density reveals the orientation and result of intermonomer and/or intramonomer charge transfer. The calculated results reveal that excited state properties of neutral pi-dimeric quinquethiophene are significantly different from those of the cationic pi-dimeric quinquethiophenes. (c) 2007 American Institute of Physics.
  •  
31.
  • Sun, Mengtao, et al. (författare)
  • Excited state properties of acceptor-substitute carotenoids: 2D and 3D real-space analysis
  • 2005
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 401:4-6, s. 558-564
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited state properties of three (neutral, weak and strong) acceptor-substitute carotenoids (beta-carotene) are studied theoretically with the methods of two-dimensional (2D) and three-dimensional (3D) real-space analysis. The influences of different (neutral, weak and strong) function groups attached to the polyene chain to the excited state property of the carotenoids are discussed. By the 3D real-space analysis, the charge and energy transfer of the three acceptor-substitute carotenoids after vertical absorption are studied with the transition density and charge difference density. By the 2D real-space analysis, the electron-hole coherences and excitation delocalization of the three acceptor-substitute carotenoids are studied with the transition density matrix. (C) 2004 Elsevier B.V. All rights reserved.
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32.
  • Sun, Mengtao (författare)
  • Excited state properties of novel p- and n-type organic semiconductors withl an anthracene unit
  • 2006
  • Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 320:2-3, s. 155-163
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoinduced dynamics of novel p- and n-type organic semiconductors with an anthracene unit are theoretically investigated with quantum chemistry methods. The calculated vertical absorption and fluorescence frequencies of them are consistent with the experimental data. The changing tendencies of the dihedral angles between anthracene unit and trifluoromethylphenyl (or thiophene) in the photoinduced dynamics processes (vertical absorption and vertical fluorescence) are examined from the geometries of optimized ground and excited states. To study the influence of the individual units of the derivatives to the excited state properties of the derivatives, the energies and densities of frontier orbital HOMOs and LUMOs of the individual unit and the derivatives are studied in the processes of vertical absorption and fluorescence. The excited state properties of the two derivatives in the processes of vertical absorption and fluorescence are studied with 2D and 3D real space analysis methods, which are employed to study the electron-hole coherence and the excitation delocalization (with transition density matrix method), and charge and energy transfer (with transition and charge difference density method). Overall, the computed results remain in good agreement with the relevant experimental data, and the theoretical results promote deeper understanding to the optical and electronic properties of the semiconductor in the process of photoinduced dynamics. (c) 2005 Elsevier B.V. All rights reserved.
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33.
  • Sun, Mengtao (författare)
  • Excited state properties of the chromophore of the asFP595 chromoprotein: 2D and 3D theoretical analyses
  • 2006
  • Ingår i: International Journal of Quantum Chemistry. - : Wiley. - 0020-7608 .- 1097-461X. ; 106:4, s. 1020-1026
  • Tidskriftsartikel (refereegranskat)abstract
    • The ground and excited state properties (e.g., the intramolecular charge and energy transfer, and electron-hole coherence) of the chromophore of the asFP595 chromoprotein from Anemonia sulcata in the neutral and anionic forms are theoretically studied with quantum chemistry methods. The ground-state properties of the asFP595 in the neutral and anionic forms, such as the alternations of the bond lengths and the Mulliken charge distributions, are compared. The calculated transition energies of the asFP595 in the neutral and anionic form are consistent with the experimental results. To study the excited state properties of the asFP595 chromophore, the energies and densities of highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs), as well as the CI main coefficients, are compared between the two forms. The intramolecular charge and energy transfer in the neutral and anionic forms are investigated and compared with the three-dimensional (31)) real-space analysis methods, including the strength and orientation of the transition dipoles with transition density, and the orientation and result of the intramolecular charge transfer with charge difference density. The electron-hole coherence and delocalization on the excitation are studied with the 2D real-space analysis method of the transition density matrix. In all, the calculated results are remain in good agreement with the experimental data, and the theoretical analysis results supported the proposed models in the experiment. (c) 2005 Wiley Periodicals, Inc. Int J Quantum Chem 106: 1020-1026, 2006
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34.
  • Sun, Mengtao, et al. (författare)
  • Intermolecular charge and energy transfer in neurosporene and chlorophyll a derivative complex
  • 2005
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 412:4-6, s. 425-429
  • Tidskriftsartikel (refereegranskat)abstract
    • Dye-sensitized solar cells using a chlorophyll a derivative (PPB a der.) as the sensitizer and carotenoids having different conjugation lengths as redox spacers was studied experimentally. In this Letter, the excited state properties of the neurosporene & PPB a der. complex are investigated theoretically with quantum chemistry method. The 2D real space analysis with the transition density matrix reveals that some excited states are locally excited states, and some is the intermolecular charge transfer (ICT) state. The 3D real space analysis reveals: (1) that the orientation and the strength of the dipole moment from transition density, and (2) the orientation and result of ICT in Neurosporene & PPB a der. complex from charge difference density. (c) 2005 Elsevier B.V. All rights reserved.
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35.
  • Sun, Mengtao, et al. (författare)
  • Intramolecular charge transfer and locally excited states of the fullerene-linked quarter-thiophenes dyad
  • 2005
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 413:1-3, s. 110-117
  • Tidskriftsartikel (refereegranskat)abstract
    • The ground and the excited state properties of the fullerene-linked quarter-thiophenes dyad were studied theoretically with the quantum chemistry method. To reveal the excited state properties of them in the vertical absorption process, the energies and densities of the HOMO and LUMO, the intramolecular charge transfer (ICT), locally excited (LE) are studied with transition density matrix, charge difference density and the off-resonant and resonant non-linear polarizabilities. The conclusion is drawn that there are also some intramolecular charge transfer (ICT) excited states, which result from large data of off-resonant and the resonant nonlinear polarizabilities in the vertical absorption process. (c) 2005 Elsevier B.V. All rights reserved.
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36.
  • Sun, Mengtao, et al. (författare)
  • Intramolecular charge transfer in the porphyrin-oligothiophene-fullerene triad
  • 2005
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 416:1-3, s. 94-99
  • Tidskriftsartikel (refereegranskat)abstract
    • Intramolecular charge transfer (ICT) in porphyrin-oligothiophene-fullerene triad was reported experimentally [J. Ikemoto, K. Takimiya, Y. Aso. T. Otsubo, M. Fujitsuka, O. Ito, Org. Lett. 4 (2002) 309], and the weak distance dependence of the oligothiophene spacer was found. In this Letter, ICT in this triad is theoretically investigated with quantum chemistry method as well as the 2D and 3D real space analysis methods. The calculated transition energies and oscillator strengths are consistent with the experimental data. The theoretical analysis with 2D and 3D real space analysis reveal that there are two ICT mechanisms. The experimental weak distance dependence of the oligothiophene spacer is benefitted from the superexchange mechanism. (c) 2005 Elsevier B.V. All rights reserved.
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37.
  • Sun, Mengtao, et al. (författare)
  • Near- and Deep-Ultraviolet Resonance Raman Spectroscopy of Pyrazine-Al-4 Complex and Al-3-Pyrazine-Al-3 Junction
  • 2009
  • Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:44, s. 19328-19334
  • Tidskriftsartikel (refereegranskat)abstract
    • Near- and deep-ultraviolet (UV) resonance Raman spectroscopy of pyrazine-Al-4 complex and Al-3-pyrazine-Al-3 junction was investigated theoretically with a quantum chemical method. Here, 325 and 244 nm were employed as near- and deep-UV sources in our theoretical study The intensities of static normal Raman spectra of pyrazine-Al-4 complex and Al-3-pyrazine-Al-3 junction were enhanced oil the orders of 10 and 10(3) by a static chemical mechanism, respectively The calculated absorption spectra reveal strong B-6(2) and B-13(2u) electronic transitions near 325 nm for pyrazine-Al-4 complex and 244 nm for Al-3-pyrazine-Al-3 junction, respectively. The analyses of orbital transitions in electronic transitions reveal they are the mixture of (metal to molecule) charge transfer excitation and intracluster excitation. The intensity of near-UV resonance Raman spectroscopy of pyrazine-Al-4 complex and the intensity of deep-UV resonance Raman spectroscopy of Al-3-pyrazine-Al-3 junction are strongly enhanced on the order of 10(5) and 10(4), respectively, compared to the Raman intensity of isolated pyrazine excited at 325 and 244 nm. The calculations of Mic theory and the three-dimensional finite-difference time domain method reveal strong surface plasmon resonance and strong electromagnetic enhancements at 325 and 244 nm for single and dimer nanoparticles at suitable sizes and gap distance, respectively. The strongest SERS enhancement in the system of junction is on the order of 10(8) at the incident lights of 325 and 244 nm. The total enhancements, including the chemical and electromagnetic enhancements, can reach Lip to 10(13). So, Al is a suitable material for near- and deep-UV surface-enhanced resonance Raman scattering
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38.
  • Sun, Mengtao, et al. (författare)
  • Remote Excitation Polarization-Dependent Surface Photochemical Reaction by Plasmonic Waveguide
  • 2011
  • Ingår i: Plasmonics. - : Springer Science and Business Media LLC. - 1557-1963 .- 1557-1955. ; 6:4, s. 681-687
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, we report remote excitation polarization-dependent surface photochemical reaction by plasmonic waveguide. Remote excitation polarization-dependent surface-enhanced Raman scattering (SERS) spectra indicate a surface photochemical reaction that p-aminothiophenol is converted to p,p'-dimercaptoazobenzene (DMAB) induced by the plasmonic waveguide. Surface plasmon polaritons generated at the end of a silver nanowire can propagate efficiently along the nanowire, and be coupled by nanoparticles near the nanowire as a nanoantenna. Massive electromagnetic enhancement is generated in the nanogap between the nanowire and the nanoparticles. The remote excitation polarization-dependent SERS spectra can be obtained experimentally in the nanogaps; furthermore, the remote excitation polarization-dependent SERS spectra of DMAB reveal the occurrence of this surface catalytic reaction. Theoretical simulations using finite-difference time-domain methods strongly support our experimental results.
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39.
  • Sun, Mengtao, et al. (författare)
  • The pH-Controlled Plasmon-Assisted Surface Photocatalysis Reaction of 4-Aminothiophenol to p,p '-Dimercaptoazobenzene on Au, Ag, and Cu Colloids
  • 2011
  • Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:19, s. 9629-9636
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we report experimentally and theoretically a surface photocatalysis reaction of 4-aminothiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) on Au, Ag, and Cu colloids. Surface enhanced Raman scattering (SEAS) spectra of PATP on Au and Cu colloids are significantly different from the normal Raman spectrum of PATP powder. Quantum chemical calculations reveal that PATP on Au and Cu colloids is converted to DMAB by a surface photocatalysis reaction, and all the strongly enhanced Raman peaks are the symmetric Ag vibrational mode by surface plasmon. The pH value effects on surface photocatalysis reaction were also investigated experimentally. It is found that plasmon-assisted surface photocatalysis reaction can be efficiently controlled by different pH values. The possibility of protonation of PATP adsorbed on Au and Ag nanoparticles at pH 3 is investigated theoretically. The molecular mechanism is proposed for controlling surface photocatalysis reaction by pH values.
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40.
  • Sun, Mengtao, et al. (författare)
  • Visualizations of transition dipoles, charge transfer, and electron-hole coherence on electronic state transitions between excited states for two-photon absorption.
  • 2008
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The one-photon absorption (OPA) properties of donor-pi-bridge-acceptor-pi-bridge-donor (D-pi-A-pi-D)-type 2,1,3-benzothiadiazoles (BTD) were studied with two dimensional (2D) site and three dimensional (3D) cube representations. The 2D site representation reveals the electron-hole coherence on electronic state transitions from the ground state. The 3D representation shows the orientation of transition dipole moment with transition density, and the charge redistribution on the excited states with charge difference density. In this paper, we further developed the 2D site and 3D cube representations to investigate the two-photon absorption (TPA) properties of D-pi-A-pi-D-type BTD on electronic transitions between excited states. With the new developed 2D site and 3D cube representations, the orientation of transition dipole moment, the charge redistribution, and the electron-hole coherence for TPA of D-pi-A-pi-D-type BTD on electronic state transitions between excited states were visualized, which promote deeper understanding to the optical and electronic properties for OPA and TPA.
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41.
  • Wang, Jingang, et al. (författare)
  • Voltage-manipulating graphene-mediated surface-enhanced Raman scattering (G-SERS) : principle and applications
  • 2020
  • Ingår i: Applied Spectroscopy Reviews. - : Informa UK Limited. - 0570-4928 .- 1520-569X. ; 55:7, s. 558-573
  • Forskningsöversikt (refereegranskat)abstract
    • The voltage-controlled graphene-mediated surface-enhanced Raman scattering (G-SERS) spectroscopy is experimentally developing spectral technology, and which is prosperously applied in the fields of ultra-sensitive spectral analysis, sensor and catalysis. In this review, we introduce the physical principle, fabrication method, and recent applications of voltage-controlled G-SERS. We firstly introduce fabrication methods of voltage-controlled G-SERS substrate, based on the hybrid between graphene and noble metal. Secondly, the physical mechanism of voltage-controlled G-SERS is proposed for exploring the advantages of voltage-controlled G-SERS over traditional SERS. The plasmon–exciton coupling for G-SERS substrate is of greatly advantages than SERS substrate enhanced by plasmon only. The plasmon-exciton coupling can result in plexciton, and then G-SERS can also be considered as a kind of plexciton-enhanced Raman scattering (PERS). Thirdly, recent advances of voltage-controlled G-SERS on applications in spectral analysis; sensor and catalysis, especially on surface catalytic reactions, are summarized in detail. This review can not only promote deeper understating of physical principle on voltage-controlled G-SERS, but also promote potential applications in physical, chemical, material, spectral and environmental fields.
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42.
  •  
43.
  • Xia, Lixin, et al. (författare)
  • Selective reduction of nitroaromatic compounds on silver nanoparticles by visible light
  • 2012
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:8, s. 1024-1028
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, we report experimentally and theoretically that nitroaromatic compounds, 2,4-dinitrobenzenethiol and 4-chloro-2-nitrobenzenethiol, on silver sols can be selectively reduced to 2-amino-4-nitrobenzenethiol and 2-amino-4-chlorobenzenethiol simply by irradiating with a visible light in ambient conditions, and the selective photoreduction is a very facile process. The results of quantum chemical calculations are in good agreement with our experimental data. Copyright (c) 2012 John Wiley & Sons, Ltd.
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44.
  • Xia, Lixin, et al. (författare)
  • Visualized method of chemical enhancement mechanism on SERS and TERS
  • 2014
  • Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 45:7, s. 533-540
  • Forskningsöversikt (refereegranskat)abstract
    • We review our developed visualization method of charge transfer (CT) for chemical enhancement mechanism on surface-enhanced Raman scattering (SERS) and tip-enhanced Raman spectroscopy (TERS). Firstly, we describe our visualization method of charge difference density, which provides direct visual evidence for photoinduced CT. And then, using the visualization method of CT, we interpreted the mechanism of SERS and TERS. Photoinduced charge transfer in the processes of SERS and TERS can be clearly seen. Our visualization method provides a visual and easy understanding way for the mechanism of SERS and TERS. Copyright (C) 2014 John Wiley & Sons, Ltd.
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45.
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46.
  • Yang, Xianzhong, et al. (författare)
  • Plasmon-exciton coupling of monolayer MoS2-Ag nanoparticles hybrids for surface catalytic reaction
  • 2017
  • Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 5, s. 72-78
  • Tidskriftsartikel (refereegranskat)abstract
    • The optical properties of monolayer molybdenum disulfide (MoS2)/Ag nanoparticle (NP) hybrids and their application to surface catalytic reactions were studied by transmission, photoluminescence (PL) and Raman spectroscopies. The local surface plasmon resonance (LSPR) of Ag nanoparticles was tuned to better match the exciton energy of monolayer MoS2. The PL of the hybrids was enhanced by more than 50 times when the local surface plasmon resonance (LSPR) peak was tuned systematically from 438 nm to 532 nm, indicating a stronger coupling and higher energy transfer rate between the plasmon of the Ag NPs and the excitons of the MoS2. Additionally, photocatalytic reactions of 4-nitrobenzenethiol (4NBT) were performed on the MoS2, the Ag nanoparticles, and the hybrid MoS2 with Ag nanoparticles. On the MoS2 substrate alone, there is no photocatalytic reaction. With a low laser intensity, the probability of a chemical reaction occurring for molecules directly adsorbed onto the Ag NPs is much lower than the probability of a reaction involving those molecules adsorbed onto the MoS2/Ag substrate. At a higher power, although the electric field was reduced by approximately 30% by the MoS2 layer, there is better efficiency for the plasmon-exciton co-driven surface catalytic reactions on the MoS2/Ag substrate compared to the Ag substrate alone. Our findings illustrate the potential to control hot carriers for better surface catalytic reactions by tuning the exciton-plasmon coupling between the 2D transition metal dichalcogenides (TMDCs) and Ag NPs.
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47.
  • Yang, Zhilin, et al. (författare)
  • Surface enhanced Raman scattering of pyridine adsorbed on Au@Pd core/shell nanoparticles
  • 2009
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:23
  • Tidskriftsartikel (refereegranskat)abstract
    • Surface enhanced Raman scattering (SERS) of pyridine adsorbed on Au@Pd core/shell nanoparticles has been investigated theoretically with quantum chemical method, generalized Mie theory and three-dimensional finite-difference time domain (3D-FDTD) method. We first studied the influence of the coated Pd on the electronic structure of Au nanoparticle, and compared the electronic structure of Au-20 cluster with that of Au10Pd10 (core/shell) cluster. Second, we studied SERS spectroscopy of pyridine on Au@Pd core/shell nanoparticles, which revealed the rate of static chemical enhancement and electromagnetic enhancement in the experimental reports. Third, the influence of the Pd shell thickness to the optical absorption of Au@Pd core/shell nanoparticles was investigated with generalized Mie theory. Fourth, we studied the influence of the shell thickness to the local electric field enhancement with 3D-FDTD method. The theoretical results reveal that the static chemical enhancement and electromagnetic enhancement are in the order of 10 and 10(3), respectively. These theoretical studies promote the deeper understanding of the electronic structure and optical absorption properties of Au@Pd, and the mechanisms for SERS of molecule adsorbed on Au@Pd.
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48.
  • Zhang, Zhenglong, et al. (författare)
  • Tip-Enhanced Ultrasensitive Stokes and Anti-Stokes Raman Spectroscopy in High Vacuum
  • 2013
  • Ingår i: Plasmonics. - : Springer Science and Business Media LLC. - 1557-1963 .- 1557-1955. ; 8:2, s. 523-527
  • Tidskriftsartikel (refereegranskat)abstract
    • We report ultrasensitive Stokes and anti-Stokes Raman spectra of 1,2-benzenedithiol monolayer on Ag film with home-made high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) system. Raman peaks that were orginally very weak were observed experimentally and assigned theoretically. The local temperature was obtained based on the observed Stokes and anti-Stokes HV-TERS spectra.
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49.
  • Zhou, Mengtao, et al. (författare)
  • The efficiency of continuous regional intra-arterial infusion in the treatment of infected pancreatic necrosis
  • 2013
  • Ingår i: Pancreatology. - : Elsevier BV. - 1424-3903. ; 13:3, s. 212-215
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: Our aim was to investigate the efficiency of continuous regional intra-arterial infusion (CRAI) with antisecretory agents and antibiotics in the treatment of infected pancreatic necrosis. Materials and methods: CRAI was used as a new clinical technique to treat acute pancreatitis patients during a 4-year period at the First Affiliated Hospital, Wenzhou Medical College, China. In this retrospective study, thirty-four patients with proven infected pancreatic necrosis were included. Twelve patients were treated with CRAL and were matched according to age, sex, APACHE II scores, Ranson scores and remote organ dysfunction, with 22 patients with IPN treated surgically. The clinical outcome following surgery and CRAI were compared. Results: No difference was found between the two groups when comparing age, gender, APACHE II scores, Ranson scores and remote organ dysfunction (p > 0.05). The patients treated with CRAI had a lower incidence of complications (33.3% vs 72.7%), duration of hospitalization (27.1 +/- 4.7 days vs 43.0 +/- 12.0 days) and cost of hospitalization (4.09 +/- 1.64 thousand RMB vs 8.77 +/- 3.74 thousand RMB) as compared to patients treated with surgery (p < 0.05). The survival rate was significantly higher in the CRAI group as compared to the surgical group (91.7% vs 63.6%; p < 0.01). However, the two groups had similar rates of concomitant operative treatment and incidence of remote organ dysfunction (p > 0.05). Conclusions: CRAI or CRAI in combination with abscess drainage seemingly improve the clinical outcome in patients with infected pancreatic necrosis. Further confirmative prospective randomized multicenter studies are warranted prior to broad introduction of the CRAI concept. Copyright (C) 2013, IAP and EPC. Published by Elsevier India, a division of Reed Elsevier India Pvt. Ltd. All rights reserved.
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50.
  • Zhou, Mengtao, et al. (författare)
  • The protective effects of Lipoxin A(4) during the early phase of severe acute pancreatitis in rats
  • 2011
  • Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 1502-7708 .- 0036-5521. ; 46:2, s. 211-219
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective. Our aim was to investigate the protective effects of a Lipoxin A(4) analogue (LXA(4)) in the early phase of acute pancreatitis in rats. Materials and methods. Severe acute pancreatitis (SAP) was induced by injection of 5% sodium taurocholate into the pancreatic duct. Rats with SAP were treated with LXA(4) (0.1 mg/kg), 10 min after the 5% sodium taurocholate injection, after which LXA(4) was administrated every 8 hours, three times (LXA(4) group). The sham group was only given the vehicle after operation. Plasma amylase activity, serum levels of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF-alpha) were measured at 4, 12, and 24 h after induction of SAP. The pancreatic index and histopathologic observations were evaluated and the expression of intercellular adhesion molecule-1 (ICAM-1) and NF-kappa B p65 in the pancreas, and the expression of ICAM-1 in the lungs were detected by immunohistochemistry. Results. LXA(4) treated rats had lower serum levels of TNF-alpha, IL-1, and IL-6 at all time points measured (p < 0.05), but significantly differed in plasma amylase activity only at 24 h as compared with the SAP group. The pancreatic index and the scores of pancreatitic histopathologic evaluations were lower in the LXA(4) group as compared to the SAP group. Immunohistochemistry showed that LXA(4) attenuated the expression of ICAM-1 and NF-kappa B p65 in the pancreas, as well as the expression of ICAM-1 in the lungs in animals with pancreatitis (p < 0.05). Conclusions. We demonstrate that LXA(4) has protective effects in experimental SAP, which may be achieved by inhibiting the NF-kappa B signalling pathway, thereby reducing the production of proinflammatory cytokines.
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