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  • 601.
    Zeng, Yong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Chen, Xiaoshuang
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science.
    Lu, Wei
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Complete band gaps in three-dimensional quantum dot photonic crystals2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 11, p. 115325-Article in journal (Refereed)
    Abstract [en]

    Nonlocal investigations have been performed about exciton-photon couplings in three-dimensional quantum-dot (QD) photonic crystals and a complete photonic band gap has been found in the band structure of a diamond lattice. The width of such a band gap can be broadened by increasing the filling ratio of the QDs (increasing the QD radius or/and decreasing the lattice constant of the photonic crystal). By decomposing the diamond lattice into two interlacing face-centered-cubic (fcc) sublattices, we have found that by significantly modifying the QD radius in one fcc sublattice (the diamond lattice therefore changed to the zinc blende lattice), the band structure of the zinc blende lattice is in principle the sum of two individual fcc sublattices. However, a huge exciton-photon coupling is observed near the band gaps of the two individual fcc sublattices when the radii of the QDs in the two fcc sublattices approach each other, resulting in the complete band gaps of the diamond structure.

  • 602. Zeng, Yong
    et al.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Chen, Xiaoshuang
    Lu, Wei
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Dynamics of the damping oscillator formed by the collective generation of surface polaritons for extraordinary light transmission through subwavelength hole arrays in thin metal films2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, no 12Article in journal (Refereed)
    Abstract [en]

    Light transmissions through a subwavelength hole array in a thin metal film are characterized by resonance peaks in the transmission spectrum. In this work we study the surface polaritons (SPs) in perforated thin metal films by analyzing the dynamic behavior of the Poynting vectors based on a full-vector finite-difference time-domain approach. It is shown that each resonance peak in the transmission spectrum is caused by a collective generation of SPs in the form of a dynamic damping oscillator which oscillates in space and time. The energy of the incident light is transported between the upper and the lower metal-air surfaces during the spatial oscillations largely through the air holes. This energy transport mechanism prevails even when the metal-film thickness becomes as thin as 100 nm, under which circumstance the wave functions of the SPs, localized separately on the two metal-air surfaces when the metal film is thick, begin to strongly overlap with each other. The lifetimes of the damping oscillators are different for different resonance peaks in the transmission spectrum and remain distinguishable by the order of their temporal development.

  • 603.
    Zeng, Yong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Chen, Xiaoshuang
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science.
    Lu, Wei
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Extended plane-wave-based transfer-matrix approach to simulating dispersive photonic crystals2006In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 139, no 7, p. 328-333Article in journal (Refereed)
    Abstract [en]

    It has been difficult to compute the band structures and transmission spectra for photonic crystals (PCs) with dispersive components included in the periodic units. Here we show that by using an extended plane-wave-based transfer-matrix method, we are able to formulate the problem for computing optical properties of dispersive PCs, including magnetic and left-handed PCs. This approach is very general, since it can treat PCs with arbitrary Bravais lattice composed of materials with arbitrary dielectric permittivities and magnetic permeabilities. Combined with the supercell method, this method can further simulate defective PCs such as PC-based waveguides and microcavities.

  • 604. Zeng, Yong
    et al.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Chen, Xiaoshuang
    Lu, Wei
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Highly efficient generation of entangled photon pair by spontaneous parametric downconversion in defective photonic crystals2007In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 24, no 6, p. 1365-1368Article in journal (Refereed)
    Abstract [en]

    We study the process of spontaneous parametric downconversion in a one-dimensional defective quadratic nonlinear photonic crystal. It is shown that the strong confinements of both the pump and signal waves around the defective layer result in a giant enhancement of the entangled photon-pair generation. An enhancement factor as high as 3.4 X 10(6) is obtained in our defective structure based on the dual-localized modes. Furthermore, the linewidth of the downconverted fields is only 0. 1 nm. Such a photonic crystal structure can be applied as a highly efficient source of entangled photon pairs for highly integrated all-optical circuits.

  • 605.
    Zeng, Yong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Chen, Xiaoshuang
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science.
    Lu, Wei
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Selective excitation of surface-polariton Bloch waves for efficient transmission of light through a subwavelength hole array in a thin metal film2007In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 76, no 3, p. 035427-Article in journal (Refereed)
    Abstract [en]

    Electromagnetic (EM) field was found to be able to transmit efficiently through a subwavelength hole array in a metal thin film at specific resonant frequencies. By analyzing the near-field distributions of EM fields in the array system, as well as the corresponding Fourier spectra, we show that the surface-polariton (SP) Bloch waves focus the energy of the incident plane-wave EM field to the vicinity of the hole at resonances (through SP scattering provided by the periodic hole). Furthermore, the wave vectors of the SP waves that contribute to the focusing effect are quantized as functions of the geometric shape of the holes in such a way that the focusing effect of the EM energy into the hole is maximal. The transmission efficiency and bandwidth at resonances are found to partially depend on the number of SP modes which contribute to the focusing effect.

  • 606.
    Zhang, Fuguo
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Cong, Jiayan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Bergstrand, Jan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Liu, Haichun
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Cai, Bin
    State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT).
    Hajian, Alireza
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Yao, Zhaoyang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Wang, Linqin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Hao, Yan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Yang, Xichuan
    State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT).
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Widengren, Jerker
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT).
    A facile route to grain morphology controllable perovskite thin films towards highly efficient perovskite solar cells2018In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 53, p. 405-414Article in journal (Refereed)
    Abstract [en]

    Perovskite photovoltaics have recently attracted extensive attention due to their unprecedented high power conversion efficiencies (PCEs) in combination with primitive manufacturing conditions. However, the inherent polycrystalline nature of perovskite films renders an exceptional density of structural defects, especially at the grain boundaries (GBs) and film surfaces, representing a key challenge that impedes the further performance improvement of perovskite solar cells (PSCs) and large solar module ambitions towards commercialization. Here, a novel strategy is presented utilizing a simple ethylammonium chloride (EACl) additive in combination with a facile solvent bathing approach to achieve high quality methyammonium lead iodide (MAPbI3) films. Well-oriented, micron-sized grains were observed, which contribute to an extended carrier lifetime and reduced trap density. Further investigations unraveled the distinctively prominent effects of EACl in modulating the perovskite film quality. The EACl was found to promote the perovskite grain growing without undergoing the formation of intermediate phases. Moreover, the EACl was also revealed to deplete at relative low temperature to enhance the film quality without compromising the beneficial bandgap for solar cell applications. This new strategy boosts the power conversion efficiency (PCE) to 20.9% and 19.0% for devices with effective areas of 0.126 cm2 and 1.020 cm2, respectively, with negligible current hysteresis and enhanced stability. Besides, perovskite films with a size of 10 × 10 cm2, and an assembled 16 cm2(5 × 5 cm2 module) perovskite solar module with a PCE of over 11% were constructed.

  • 607. Zhang, Kai
    et al.
    Wei, Pingchun
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xie, Yongshu
    Oxidative Ring Closure and Metal Triggered Ring Opening: Syntheses of Macrocyclic and Linear Hexapyrroles2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 24, p. 6354-6357Article in journal (Refereed)
    Abstract [en]

    A C6F5-substituted hexapyrrane (1) was synthesized in one step. Oxidative cyclization of 1 with DDQ afforded a phlorindipyrrin conjugate (2), and subsequent FeCl3-assisted oxidative cleavage of 2 afforded a terminally di-a-methoxy substituted hexapyrrin (3). On the other hand, oxidation of 1 with FeCl3 afforded 3, a hexapyrrinone Fe3+ complex (4), and a hexaphyrin (1,1,1,1,1,0) (5). These results indicate that the oxidation of hexapyrranes may be developed as an effective approach for the syntheses of novel linear and macrocyclic hexapyrroles.

  • 608. Zhang, Kai
    et al.
    Zhang, Junda
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Guo, Rui
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ou, Zhongping
    Ishida, Masatoshi
    Furuta, Hiroyuki
    Xie, Yongshu
    Synthesis of a Neo-Confused Octaphyrin and the Formation of Its Mononuclear Complexes2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 19, p. 4806-4809Article in journal (Refereed)
    Abstract [en]

    Novel neo-confused octaphyrin(1.1.1.1.1.1.1.0) (1) was synthesized by oxidative ring closure of an octapyrrane bearing two terminal "confused" pyrroles. Crystal structures of its Zn(II) and Cu(II) complexes (2 and 3) show a figure-of-eight conformation with unique mononuclear coordination structures. Photophysical data and theoretical calculations suggest that the neo-confused octaphyrin 1 is a 34 pi electron conjugated species showing nonaromaticity. Coordination of pocopper and zinc ions results in the further narrowing of the HOMO-LUMO gaps.

  • 609.
    Zhang, Qiong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    The adsorption of xyloglucan on cellulose: effects of explicit water and side chain variation2011In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, no 16, p. 2595-2602Article in journal (Refereed)
    Abstract [en]

    The interaction between para-crystalline cellulose and the cross-linking glycan xyloglucan (XG) plays a central role for the strength and extensibility of plant cell walls. The coating of XGs on cellulose surfaces is believed to be one of the most probable interaction patterns. In this work, the effects of explicit water and side chain variation on the adsorption of XGs on cellulose are investigated by means of atomistic molecular dynamics simulations. The adsorption properties are studied in detail for three XGs on cellulose I beta 1-10 surface in aqueous environment, namely GXXXGXXXG, GXXLGXXXG, and GXXFGXXXG, which differ in the length and composition of one side chain. Our work shows that when water molecules are included in the theoretical model, the total interaction energies between the adsorbed XGs and cellulose are considerably smaller than in vacuo. Furthermore, in water environment the van der Waals interactions prevail over the electrostatic interactions in the adsorption. Variation in one side chain does not have significant influence on the interaction energy and the binding affinity, but does affect the equilibrium structural properties of the adsorbed XGs to facilitate the interaction between both the backbone and the side chain residues with the cellulose surface. Together, this analysis provides new insights into the nature of the XG-cellulose interaction, which helps to further refine current molecular models of the composite plant cell wall.

  • 610.
    Zhang, Qiong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512). KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512). KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Tu, Yaoquan
    A molecular dynamics study of the thermal response of crystalline cellulose I beta2011In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 18, no 2, p. 207-221Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations were performed to better understand the atomic details of thermal induced transitions in cellulose I beta. The latest version of the GLYCAM force field series (GLYCAM06) was used for the simulations. The unit cell parameters, density, torsion angles and hydrogen-bonding network of the crystalline polymer were carefully analyzed. The simulated data were validated against the experimental results obtained by X-ray diffraction for the crystal structure of cellulose I beta at room and high temperatures, as well as against the temperature-dependent IR measurements describing the variation of hydrogen bonding patterns. Distinct low and high temperature structures were identified, with a phase transition temperature of 475-500 K. In the high-temperature structure, all the origin chains rotated around the helix axis by about 30A degrees and the conformation of all hydroxymethyl groups changed from tg to either gt on origin chains or gg on center chains. The hydrogen-bonding network was reorganized along with the phase transition. Compared to the previously employed GROMOS 45a4 force field, GLYCAM06 yields data in much better agreement with experimental observations, which reflects that a cautious parameterization of the nonbonded interaction terms in a force field is critical for the correct prediction of the thermal response in cellulose crystals.

  • 611.
    Zhang, Qiong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Tu, Yaoquan
    Tian, He
    Zhao, Yan-Li
    Stoddart, J. Fraser
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Working Mechanism for a Redox Switchable Molecular Machine Based on Cyclodextrin: A Free Energy Profile Approach2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 19, p. 6561-6566Article in journal (Refereed)
    Abstract [en]

    This paper reports the working mechanism for a redox-responsive bistable [2]rotaxane incorporating an alpha-cyclodextrin (alpha-CD) ring (J. Am. Chem. Soc. 2008, 130, 11294-11296), based on free energy profiles obtained from all-atom molecular dynamics simulations. Employing an umbrella sampling technique, the free energy profiles (potential of mean force, PMF) were calculated for the shuttling motion of the alpha-CD ring between a tetrathiafulvalene (TTF) recognition site and a triazole (TZ) unit on the dumbbell of the rotaxane for three oxidation states (0, +1, +2) of the TTF unit. These calculated free energy profiles verified the experimentally observed binding preference for each state. Analysis of the free energy components reveals that, for these alpha-CD-based rotaxanes with charged TTF units, the real driving force for the shuttling in the oxidized states is actually the interactions between water and the rotaxane components, which overwhelms the attractive interactions between the alpha-CD ring and the charged dumbbell. In this work, we put forward a feasible approach to correctly describe the complexation behavior of CD with charged species, that is, free energy profiles obtained from all-atom molecular dynamics simulation.

  • 612. Zhang, Qiong
    et al.
    Tu, Yaoquan
    Tian, He
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Molecular dynamics simulations of local field factors2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 1Article in journal (Refereed)
    Abstract [en]

    In the present work, the authors evaluate a scheme based on molecular dynamics to derive local field factors. These are given without any assumption of a cavity by fitting the Langevin functions to the order parameters obtained from the molecular dynamics simulations. The local field factors so obtained, with the detailed chromophore-solvent interactions and solvent structures taken into account, are much smaller than those calculated from the conventional Onsager and Lorentz models. A numerical demonstration is given for two typical organic chromophore molecules, p-nitroaniline and p-nitro-N,N-dimethylaniline dissolved in chloroform.

  • 613. Zhang, Qiong
    et al.
    Tu, Yaoquan
    Tian, He
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Molecular dynamics simulations of polycarbonate doped with Lemke chromophores2007In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 36, p. 10645-10650Article in journal (Refereed)
    Abstract [en]

    In the search for optimal electro-optical modulating materials we report in this work molecular dynamics simulations of polycarbonate doped with Lemke chromophores which is a promising candidate system for materials with such functionality. The simulations cover the electric field poling effects on the chromophore order at a temperature above the glass transition temperature (T-g) of the material, the cooling procedure from liquid state to the glass state in the presence of the poling field, and the back relaxation of the system after removal of the field. Our study shows that electric field poling results in a higher chromophore order and that the order is also maintained during the cooling procedure with the poling field applied. In the liquid state, the applied poling field has little effect on the structure of the material. However, after the cooling procedure, the structure changes significantly because the polymer matrix tends to become closely packed. Our study thus indicates that for the bulk material, the structure of the host matrix is very important in determining the performance of the material.

  • 614. Zhang, Qi-Wei
    et al.
    Li, Dengfeng
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    White, Paul B.
    Mecinovic, Jasmin
    Ma, Xiang
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Nolte, Roeland J. M.
    Tian, He
    Multicolor Photoluminescence Including White-Light Emission by a Single Host-Guest Complex2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 41, p. 13541-13550Article in journal (Refereed)
    Abstract [en]

    Achieving multicolor photoluminescence, 'especially white-light emission, under mild conditions based on a single "fluorescent compound-is a great challenge. Herein, we report a novel colorful-emission host guest complex BPCY, which is composed of a two-arm fluorescent guest molecule (BPC) and gamma-cyclodextrin (gamma-CD) as the host-molecule. BPC bears a unique asymmetrical donor acceptor donor (D-1-A(+)similar to D-2)-type structure, where D-1, A(+), and D-2 stand for the binaphthol electron donor, pyridinium electron acceptor, and coumarin electron donor, respectively. The luminescence property of BPC shows dual-sensitivity, i.e., toward the excitation wavelength and the cyclodextrin host molecule. Under certain conditions, the complex shows three different emission wavelengths, allowing the realization of multicolor photoluminescence, including red (R), green (G), and blue (B) as well as various intermediate colors by orthogonally modulating these two stimuli. In this way, nearly pure white-light emission with CIE coordinates (0.33, 0.34) could be generated. A combination of structural, spectroscopic, and computational simulation studies revealed the occurrence of synergetic mechanistic processes for the stimuli-responsive multicolor luminescence of the BPCY complex, namely, host-enhanced intramolecular charge-transfer (ICT) and host-induced restriction of intramolecular rotation (RIR). This new supramolecular complex with superior multicolor emission abilities may find wide applications in the fields of information processing and display media. Furthermore, the molecular design rationale presented here may provide a new design strategy for the development of high performance optical materials using a single supramolecular platform.

  • 615. Zhang, X.
    et al.
    Chen, L.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Mao, J.
    Wu, W.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hua, J.
    Photovoltaic properties of bis(octyloxy)benzo-[c][1,2,5]thiadiazole sensitizers based on an N,N-diphenylthiophen-2-amine donor2014In: Journal of Materials Chemistry C, ISSN 2050-7526, Vol. 2, no 20, p. 4063-4072Article in journal (Refereed)
    Abstract [en]

    Three D-A-π-A sensitizers (DOBT-IV to DOBT-VI) with N,N- diphenylthiophen-2-amine as the donor and bis(octyloxy)benzo-[c][1,2,5] thiadiazole (DOBT) as the auxiliary acceptor have been designed and synthesized. Their applications to dye-sensitized solar cells with I-/I 3 - and Co(ii)/(iii) electrolytes were measured and characterized. Via fine tuning of the π-bridge, the highest photoelectric conversion efficiency of 7.16% was obtained with Jsc = 16.88 mA cm-2, Voc = 0.662 V and FF = 64.03% for the DOBT-V based dye-sensitized solar cells using the I-/I3 - electrolyte under standard global AM1.5 solar conditions. A photoelectric conversion efficiency of 6.14% was obtained with Jsc = 11.35 mA cm-2, Voc = 0.760 V and FF = 71.16% with the Co(ii)/(iii) electrolyte under standard global AM1.5 solar conditions. The optical and electrochemical properties and the photovoltaic performance were evaluated and investigated using density functional theory calculations, a behavior study of the four performance parameters with dependence of the incident light intensity, electrochemical impedance spectroscopy and intensity-modulated photo-voltage spectrometry.

  • 616. Zhang, Xiaoyu
    et al.
    Guo, Fuling
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    He, Jinxiang
    Wu, Wenjun
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hua, Jianli
    Effect of thiophene in bithiazole-bridged sensitizers on the performance of dye-sensitized solar cells2014In: Nano, ISSN 1793-2920, Vol. 9, no 5, p. 1440009-Article in journal (Refereed)
    Abstract [en]

    In this paper, we have designed and synthesized four bithiazole-bridged sensitizers (BT-T2, TBT-T2, BT-T3 and TBT-T3) with triphenylamine and indoline as the donor segment and applied them to dye-sensitized solar cells (DSSCs). For triphenylamine-based sensitizers as BT-T2 and TBT-T2, adding one thiophene unit between triphenylamine donor and bithiazole moiety not only led to bathochromic shift of the maximum absorption and increase of molar extinction coefficient, but also enhanced the photovoltaic conversion efficiency from 7.12% of BT-T2 to 7.51% of TBT-T2. But for indoline-based sensitizers as BT-T3 and TBT-T3, adding one thiophene unit between indoline donor and bithiazole moiety resulted in hypochromatic shift instead of bathochromic shift. We employed the density functional theory (DFT) calculations to further investigate the influence of the thiophene unit on their optical and electronic properties and photovoltaic performance of corresponding DSSC devices. Given the results, a reasonable explanation is the introduction of thiophene unit suppressed the intramolecular charge transfer and charge separation in the conjugation system of indoline-based sensitizer, which led to the hypochromatic shift of the maximum absorption wavelength and finally the low J(sc). Since the J(sc) dropped sharply from 15.26mAcm(-2) to 4.52mAcm(-2), the photovoltaic conversion efficiency decreased dramatically from 7.86% to 1.93%.

  • 617. Zhang, Xiaoyu
    et al.
    Mao, Jiangyi
    Wang, Dan
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yang, Jiabao
    Shen, Zhongjin
    Wu, Wenjun
    Li, Jing
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hua, Jianli
    Comparative Study on Pyrido[3,4-b]pyrazine-Based Sensitizers by Tuning Bulky Donors for Dye-Sensitized Solar Cells2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 4, p. 2760-2771Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSSCs) with cobalt electrolytes have gained increasing attention. In this Research Article, two new pyrido[3,4-b]pyrazine-based sensitizers with different cores of bulky donors (indoline for DT-1 and triphenylamine for DT-2) were designed and synthesized for a comparative study of their photophysical and electrochemical properties and device performance and were also analyzed through density functional theory calculations. The results of density function theory calculations reveal the limited electronic communication between the biphenyl branch at the cis-position of N-phenylindoline and the indoline core, which could act as an insulating blocking group and inhibit the dye aggregation and charge recombination at the interface of TiO2/dye/electrolyte. As expected, DSSCs based on DT-1 with cobalt redox electrolyte gained a higher photoelectric conversion efficiency of 8.57% under standard AM 1.5 G simulated sunlight, with J(sc) = 16.08 mA cm(-2), V-oc = 802 mV, and FF = 0.66. Both electrochemical impedance spectroscopy (EIS) and intensity-modulated photovoltage spectroscopy (IMVS) suggest that charge recombination in DSSCs based on DT-1 is much less than that in their counterparts of DT-2, owing to the bigger donor size and the insulating blocking branch in the donor of DT-1.

  • 618. Zhang, Zhisen
    et al.
    Shen, Jiawei
    Wang, Hongbo
    Wang, Qi
    Zhang, Junqiao
    Liang, Lijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Effects of Graphene Nanopore Geometry on DNA Sequencing2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 9, p. 1602-1607Article in journal (Refereed)
    Abstract [en]

    In this Letter we assess the effect of graphene nanopore geometries on DNA sequencing by considering DNA fragments including A, T, C, G, and 5-methylcytosine (MC) pulled out of graphene nanopores of different geometries with diameters down to similar to 1 nm. Using steered molecular dynamics simulations it is demonstrated that the bases (A, T, C, G, and MC) can be indentified at single-base resolution through the characteristic peaks on the force profile in a circular graphene nanopore but not in nanopores with other asymmetric geometries. Our study suggests that the graphene nanopore surface should be modified as symmetrically as possible in order to sequence DNA by atomic force microscopy or optical tweezers.

  • 619.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Zou, Rongfeng
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Guanglin, Kuang
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Angstrom, Bengt
    Uppsala Univ, Dept Chem, S-75123 Uppsala, Sweden..
    Halidin, Christer
    Karolinska Inst, Ctr Psychiat Res, Dept Clin Neurosci, S-17176 Stockholm, Sweden.;Stockholm Cty Council, S-17176 Stockholm, Sweden..
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Henan Univ, Coll Chem & Chem Engn, Kaifeng 475004, Henan, Peoples R China..
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Enhanced Sampling Simulations of Ligand Unbinding Kinetics Controlled by Protein Conformational Changes2019In: Journal of Chemical Information and Modeling, ISSN 1549-9596, E-ISSN 1549-960X, Vol. 59, no 9, p. 3910-3918Article in journal (Refereed)
    Abstract [en]

    Understanding unbinding kinetics of protein-ligand systems is of great importance for the design of ligands with desired specificity and safety. In recent years, enhanced sampling techniques have emerged as effective tools for studying unbinding kinetics of protein-ligand systems at the atomistic level. However, in many protein-ligand systems, the ligand unbinding processes are strongly coupled to protein conformational changes and the disclosure of the hidden degrees of freedom closely related to the protein conformational changes so that sampling is enhanced over these degrees of freedom remains a great challenge. Here, we show how potential-scaled molecular dynamics (sMD) and infrequent metadynamics (InMetaD) simulation techniques can be combined to successfully reveal the unbinding mechanism of 3-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-6-[F-18]fluorodibenzo[b,d]thiophen e 5,5-dioxide ([F-18]ASEM) from a chimera structure of the alpha 7-nicotinic acetylcholine receptor. By using sMD simulations, we disclosed that the "close to "open" conformational change of loop C plays a key role in the ASEM unbinding process. By carrying out InMetaD simulations with this conformational change taken into account as an additional collective variable, we further captured the key states in the unbinding process and clarified the unbinding mechanism of ASEM from the protein. Our work indicates that combining sMD and InMetaD simulation techniques can be an effective approach for revealing the unbinding mechanism of a protein-ligand system where protein conformational changes control the unbinding process.

  • 620.
    Zhou, Yunyun
    et al.
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Baryshnikov, Gleb V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine..
    Li, Xuping
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Zhu, Mingjie
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Zhu, Liangliang
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Anti-Kasha's Rule Emissive Switching Induced by Intermolecular H-Bonding2018In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 21, p. 8008-8016Article in journal (Refereed)
    Abstract [en]

    The exploration of emission pathways from high-excited states in organic luminogens has recently become prosperous owing to improved possibilities to study so-called anti-Kasha's rule emission with the potential of improving the luminescent quantum efficiency. However, emission pathway switching among different high-excited states has rarely been addressed through external control. We here present a rational design and synthesis of a novel azulene-based emitter to achieve a responsive control of its anti-Kasha's rule emissive switching. The emitter initially gives rise to an S-3-to-S-0 dominant emission as indicated by our experimental and theoretical studies. On this basis, it can be toggled into an S-2-to-S-0 dominant emission upon the H-bond formation between the triformyl groups and water molecules. Such a process, which originates from the H-bonding regulated distribution of excited state energy, is accompanied by a remarkable fluorescent color conversion and a significant improvement of the fluorescent quantum yield in the azulene family. Moreover, a reversible emissive switching in doped films was observed to depend on a solid-state H-bond tuning process with moisture sensitivity. These results may provide new insight for building advanced chemical systems for visualized sensing with high distinguishability.

  • 621. Zhu, Haibo
    et al.
    Li, Wenqin
    Wu, Yongzhen
    Liu, Bo
    Zhu, Shiqin
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhu, Weihong
    Insight into Benzothiadiazole Acceptor in D-A-pi-A Configuration on Photovoltaic Performances of Dye-Sensitized Solar Cells2014In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 2, no 4, p. 1026-1034Article in journal (Refereed)
    Abstract [en]

    The option of conjugated pi-linkers is critical for molecular engineering toward the energy-level strategy of donor-pi-acceptor (D-pi-A) sensitizers. There is always a balance in the optimization of a it-linker. The pi-conjugation should be enlarged to expand the light-harvesting capability of sensitizers for an increase in photocurrent; however, the oversized it-linker also would affect seriously the photovoltage and photostability. Two sensitizers, WS-22 and WS-23, are constructed without or with benzothiadiazole (BTD) in a molecular skeleton, aiming to gain insight into the effect of an auxiliary acceptor in D-A-pi-A sensitizers on the photophysical and photovoltaic performances, especially focusing on the exploitation of the short circuit current density (J(sc)) and open circuit voltage (V-oc). Compared with the typical D-pi-A sensitizer WS-22, the incorporation of an auxiliary acceptor of BTD in WS-23 can improve the light-harvesting ability both in red-shifting the absorption peaks and the increment of absorption coefficient. The predominant increase by 15.6% in light-harvesting efficiency (LHE) of WS-23 results in a relatively higher J(sc) from 13.77 (WS-22) to 16.91 mA cm(-2) (WS-23). Moreover, the improvement of the V-oc in WS-23 is originated by a synergy contribution of the uplifting of E-CB and inhibition of charge recombination. The stepped light-induced transient (SLIT) measurements indicate that the introduction of BTD can negatively shift the conduction band of the TiO2 film. For WS-23, the higher molecular dipole moment can bring forth a more effective charge separation between donor and acceptor units, also resulting in an increase in V-oc. The incorporated BTD unit can increase V-oc by 57 mV, arising from the CB edge shift of TiO2 (accounting for 40%, 23 mV) and the retarding charge recombination (accounting for 60%, 34 mV). As a consequence, WS-23 realizes an optimizing photovoltaic efficiency (eta = 8.15%), with an improvement of 36.5% with respect to WS-22.

  • 622. Zhu, L.
    et al.
    Ang, C. Y.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Nguyen, K. T.
    Tan, S. Y.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Y.
    Luminescent color conversion on cyanostilbene-functionalized quantum dots via in-situ photo-tuning2012In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 24, no 29, p. 4020-4024Article in journal (Refereed)
    Abstract [en]

    Photo-responsive CdSe quantum dots functionalized with the cyanostilbene unit are synthesized. The as-prepared quantum dot hybrid reveals a photo-tunable dual fluorescent characteristic. White light emission can be generated in situ from the hybrid through photoirradiation to adjust the relative intensities of the two complementary emissions. Luminescent color conversion through yellow, white, and blue can be realized by varying the photoirradiation time.

  • 623. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sanders, Samuel N.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Unimolecular Photopolymerization of High-Emissive Materials on Cylindrical Self-Assemblies2015In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 48, no 15, p. 5099-5105Article in journal (Refereed)
    Abstract [en]

    We report a novel self-assembly pathway from a bis(imidazolyl) diphenyl-diacetylene (DPDA) compound as a realization of self-templated photopolymerization with high polymerization degrees. The work takes advantage of a cylindrical self-assembly that strengthens the preorganization of the diphenyl-diacetylene moiety at the single molecular level. On this basis, photopolymerization of DPDA can be conducted smoothly to form high-molecular-weight polydiphenyl diacetylene. Such a cylindrical self-assembly is highly dependent on molecular structure, and control studies show that only oligomers can be formed on random self-assemblies from a monoimidazolyl or nonimidazolyl diphenyl-diacetylene compound. Moreover, the cylindrical self-assembly based systems bear aggregation-induced emission enhancement characteristics and are solution processable. The leading thin-film could afford a selectively tunable function in luminescent micropatterns.

  • 624. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wu, Shaojue
    Nguyen, Kim Truc
    Yan, Hong
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Yanli
    Chirality Control for in Situ Preparation of Gold Nanoparticle Superstructures Directed by a Coordinatable Organogelator2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 24, p. 9174-9180Article in journal (Refereed)
    Abstract [en]

    Imposing chirality into nanoscale superstructures is a major step forward toward systematic understanding and utilization of nanomaterials. In an attempt to achieve tunable chirality during in situ preparation of hybrid nanomaterials, we here report a novel unimolecular strategy of employing a coordinatable organogelator for the realization of chirality control in the formation of gold nanoparticle superstructures. The work takes advantage of thermally reversible sol-gel transition of the chiral dispersion as template, which causes different micelle properties that can influence the coordination ability between the organogelator and Au(III) ions. Followed by a reduction reaction, gold nanoparticle superstructures with P-helicity were prepared from the sol form of the template through a coordination-induced chiral inversion, whereas those with M-helicity were obtained from the gel form with chiral holding. Such superstructures are solvent-stable and the chirality difference between them could be observed in many solvent environments.

  • 625. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, Quan
    Ma, Xing
    Li, Menghuan
    Zhang, Huacheng
    Luo, Zhong
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Yanli
    Unimolecular Photoconversion of Multicolor Luminescence on Hierarchical Self-Assemblies2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 13, p. 5175-5182Article in journal (Refereed)
    Abstract [en]

    Facile tuning of photophysical properties is highly desirable for boosting the performance and versatility of photoluminescent materials. In an attempt to overcome the challenge of achieving the photoswitching of multicolor luminescence on unimolecular platforms, we here report a novel hierarchical self-assembly of a cyanostilbene-naphthalimide dyad as the realization of phototunable luminescence at the unimolecular level. The work takes advantage of the photoisomerization of the cyanostilbene moiety from the Z form to its E form, which causes a morphological disorder in the molecular self-assembly and gives rise to a dual fluorescent characteristic accompanied by a progressive luminescent color conversion from yellow to green and finally to blue. Such systems with convertible multicolor luminescence might exhibit application potentials for unimolecular selective imaging and labeling, as exemplified by the cell imaging studies presented in this work.

  • 626. Zhu, Liangliang
    et al.
    Tran, Helen
    Beyer, Frederick L.
    Walck, Scott D.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Killops, Kato L.
    Campos, Luis M.
    Engineering Topochemical Polymerizations Using Block Copolymer Templates2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 38, p. 13381-13387Article in journal (Refereed)
    Abstract [en]

    With the aim to achieve rapid and efficient topochemical polymerizations in the solid state, via solution-based processing of thin films, we report the integration of a diphenyldiacetylene monomer and a poly(styrene-b-acrylic acid) block copolymer template for the generation of supramolecular architectural photopolymerizable materials. This strategy takes advantage of non-covalent interactions to template a topochemical photopolymerization that yields a polydiphenyldiacetylene (PDPDA) derivative. In thin films, it was found that hierarchical self-assembly of the diacetylene monomers by microphase segregation of the block copolymer template enhances the topochemical photopolymerization, which is complete within a 20 s exposure to UV light. Moreover, UV-active cross-linkable groups were incorporated within the block copolymer template to create micropattems of PDPDA by photolithography, in the same step as the polymerization reaction. The materials design and processing may find potential uses in the microfabrication of sensors and other important areas that benefit from solution-based processing of flexible conjugated materials.

  • 627. Zou, Qi
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xu, Qunjie
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Wandong
    Qu, Yi
    A near-infrared "on-off" fluorescent and colourimetric cyanide chemodosimeter based on phenothiazine with applications in living cell imaging2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 104, p. 59809-59816Article in journal (Refereed)
    Abstract [en]

    A great deal of effort has been devoted to developing easy-to-use near-infrared probes for detecting analytes due to their advantages in the field of biosensing. Herein, a near-infrared "on-off" fluorescent chemodosimeter PTZ based on dicyano-vinyl-functionalised phenothiazine was designed and synthesised. The PTZ compound was shown to efficiently recognise cyanide ions in aqueous media by virtue of the special nucleophilicity of cyanide ions, which affects the intramolecular charge transfer efficiency in the molecule. Furthermore, it was found that it exhibited a rapid colourimetric and quenchable near-infrared (NIR) fluorescent response to cyanide ions with a detection limit as low as 67 nM, and that other anions showed almost no interference even at high concentrations. Optical spectroscopic measurements, H-1 NMR and mass spectrometry titrations, and theoretical simulations were carried out to elucidate the sensing mechanism of compound PTZ. Moreover, potential applications of this compound for biosensing have been exemplified by the successful fluorescent microscopic imaging for the detection of cyanide ions in HeLa cells.

  • 628. Zou, Qi
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhou, Ji
    Bai, Kangkang
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Synthesis and photochromism of a spirooxazine derivative featuring a carbazole moiety: Fast thermal bleaching and excellent fatigue resistance2014In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 107, p. 174-181Article in journal (Refereed)
    Abstract [en]

    A novel photochromic spirooxazine derivative bearing a carbazole moiety (SOC) was synthesized and studied in solution under flash photolysis conditions. It is found to exhibit excellent characteristics like high photochromic response, large steady-state optical density, fast thermal bleaching rate and good fatigue-resistance. The effect of different solvents on the photochromic properties of the compound was evaluated, revealing that the photochromic properties can be modulated by different solvents based on the corresponding polarity. The mechanism and kinetics of the thermal fading process of compound SOC were additionally investigated by theoretical simulations, where the isomerization pathway from the trans-trans-cis conformation was found to be several times faster than that from the cis-trans-cis conformation. This type of fast-bleaching and fatigue-resistent photochromic compounds is expected to pave an exciting avenue in future development of high-performance photochromic materials.

  • 629. Zou, Qi
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Configurable photochromism of an unsymmetrical dithienylethene derivative by Cu2+ ions or water2014In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 111, p. 1-7Article in journal (Refereed)
    Abstract [en]

    We describe a gated photochromic behavior of an unsymmetrical dithienylethene derivative, which is intrinsically inert to photoisomerization in organic solvents and which is activated by addition of Cu2+ ions or water. The mechanism behind the gated photochromic property is interpreted by theoretical simulations, suggesting that the energy levels of frontier molecular orbitals are altered by the interaction of the Schiff base moiety with Cu2+ ions or water molecules. Potential applications of such gated photochromic materials have been exemplified not only by the reversible interchange between the photoactive and photoinactive states triggered by Cu2+ ions and EDTA, but also by the construction of a keypad with sequence-dependent input signals at the molecular level.

  • 630.
    Zou, Rongfeng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Guanglin, Kuang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Henan Univ, Coll Chem & Chem Engn, Kaifeng 475004, Henan, Peoples R China..
    Nordberg, Agneta
    Karolinska Univ Hosp, Karolinska Inst, Dept Neurobiol Care Sci & Soc, Ctr Alzheimer Res,Clin Geriatr Neo & Theme Aging, S-14183 Huddinge, Sweden..
    Långström, Bengt
    Uppsala Univ, Phys Organ Chem, Dept Chem, BMC, S-75123 Uppsala, Sweden..
    Tu, Yaoquan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Free Energy Profile for Penetration of Pittsburgh Compound-B into the Amyloid beta Fibril2019In: ACS Chemical Neuroscience, ISSN 1948-7193, E-ISSN 1948-7193, Vol. 10, no 3, p. 1783-1790Article in journal (Refereed)
    Abstract [en]

    The amyloid beta (A beta) fibril is a hallmark of Alzheimer's disease (AD) and has therefore served as an important target for early diagnosis of AD. The Pittsburgh Compound-B (PiB) is one of the most famous positron emission tomography (PET) tracers commonly used for in vivo detection of A beta fibrils. Many theoretical studies have predicted the existence of various core binding sites with different microenvironments for probes binding to the A beta fibril. However, little attention has been devoted to how the probes actually penetrate into the different core binding sites. In this study, an integrated molecular modeling scheme is used to study the penetration of PiB into the core binding sites of the A beta(1-42) fibril structure recently obtained by cryogenic electron microscopy. We find that there are two core binding sites for PiB with dramatic differences in cavity size and microenvironment properties, and furthermore that the penetration of PiB into site-1 is energetically prohibitive, whereas the penetration into site 2 is much more favorable. Therefore, the binding capacity at site-2 may be larger than that at site-1 despite its lower binding affinity. Our results thus suggest that site-2 may be a major binding site for PiB binding to A beta fibril and emphasize the importance to adopt a full dynamical picture when studying tracer fibril binding problems in general, something that in turn can be used to guide the development of tracers with higher affinity and selectivity for the A beta fibril.

  • 631.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Modeling of multi-photon-induced photoluminescence from organic fluorophores and metal-coated semiconductor nanoparticles2006In: Proceedings of International Symposium on Biophotonics, Nanophotonics and Metamaterials, 2006, p. 26-26Conference paper (Refereed)
    Abstract [en]

    In this talk I will describe some applications of multiphysics modeling of molecular and nano-particle materials that have been carried out at our department. Among the various multiphysics approaches, those that combine quantum mechanics with wave mechanics and quantum mechanics with statistical mechanics have turned out to be particularly powerful for predicting optical properties of organic fluorophores, respectively, nanoparticles. The first type of combined approach allows to estimate the optical transmission from cross sections of multi-photon absorption processes and from considerations of propagation and saturation effects. The other type of combined approach, quantum mechanics with statistical mechanics, allows to account for the spontaneous photon emission of two-photon excited quantum dots including the nonradiative energy dissipation process of phonon scattering. Multi-photon quantum dots offer the combined advantage of brilliance and photo-resistance of normal quantum dots with the 3-dimensional confocality and penetration of multi-photon excitation, something that can have a broad ramification on fluorescence based experiments in biology. We have in particular investigated multiphoton-induced photoluminescence from metal-coated coated quantum dots under the influence of electromagnetic field enhancement associated with surface plasmon resonances. It is argued that up-conversion luminescence of coated quantum dots is a promising approach for bio-imaging as it can generate the multiphoton excitation at reduced laser intensities.

  • 632.
    Ågren, Hans
    et al.
    KTH, Superseded Departments, Biotechnology.
    Gel'mukhanov, Faris
    KTH, Superseded Departments, Biotechnology.
    Kramers-Heisenberg and Weisskopf-Wigner descriptions of resonant X-ray Raman scattering2000In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 110, no 03-jan, p. 153-178Article in journal (Refereed)
    Abstract [en]

    An overview is presented of the theory of X-ray Raman scattering as originally formulated by Kramers and Heisenberg and by Weisskopf and Wigner. Two particular aspects of the theory are described in some detail; the formation of band profiles and the role of symmetry, These aspects are discussed in connection with recent results for atomic and molecular scatterers obtained in radiative and nonradiative scattering experiments conducted with 2nd and 3rd generation synchrotron radiation sources.

  • 633.
    Ågren, Hans
    et al.
    KTH, Superseded Departments, Biotechnology.
    Gel'mukhanov, Faris
    KTH, Superseded Departments, Biotechnology.
    Salek, Pawel
    KTH, Superseded Departments, Biotechnology.
    Dynamics of Inner Shell Resonant Raman Scattering.1999In: Journal of the Japanese Society for Synchrotron Radiation Research, ISSN 0914-9287, Vol. 12, no 4, p. 257-267Article in journal (Refereed)
    Abstract [en]

    Some recent advances in the theory of the resonant Raman process for atoms, molecules and solids involving inner shell electrons are reviewed. Special emphasis is put on the dynamical aspects and on the notion of a duration time for the x-ray Raman process (RXS), which brings about a distinetion of processes with different time scales responsible for the formation of the spectral profile. This notion has been useful for actual predietions of various phenomena associated with RXS such as "symmetry restoration" "vibrational collapse", and "control of dissociation". The temporal theory of RXS is based on the wave packet formalism. The increase of the broad "molecular" parts relative to the atomic, or fragment, decay upon frequency detuning is demonstrated. The atomic-like resonance and molecular parts are proved to show different dispersion relations. Under certain conditions the interference between the molecular and atomic parts produces conspicuous "spectral holes". These conceptual tools are applicable also in the case of solids; there is an analogous restoration of momentum selection rules and a collapse effect upon detuning the frequency. Thus when the duration of the scattering is shortened by a large detuning, the role of electron-phonon coupling of the core excited states is suppresssed. The shortening of the RXS duration in a certain sense leads to a deloealization of the core hole in a solid. We describe also some new features that derive from the Doppler effect on ejected Auger electrons.

  • 634.
    Ågren, Hans
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Harczuk, Ignat
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Vahtras, Olav
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Decomposition of molecular properties2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 5, p. 2251-2270Article in journal (Refereed)
    Abstract [en]

    We review recent work on property decomposition techniques using quantum emical methods and discuss some topical applications in terms of antum mechanics-molecular mechanics calculations and the constructing properties of large molecules and clusters. Starting out from the -called LoProp decomposition scheme [Gagliardi et al., J. Chem. Phys., 04, 121, 4994] for extracting atomic and inter-atomic contributions to lecular properties we show how this method can be generalized to calized frequency-dependent polarizabilities, to localized perpolarizabilities and to localized dispersion coefficients. Some plications of the generalized decomposition technique are reviewed - lculations of frequency-dependent polarizabilities, Rayleigh attering of large clusters, and calculations of hyperpolarizabilities proteins.

  • 635.
    Ågren, Hans
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Mikkelsen, Kurt
    Homogeneous and heterogeneous solvent models for nonlinear optical properties2008In: Continuum Solvation Models in Chemical Physics: from theory to applications / [ed] Benedetta Mennucci; Roberto Cammi, John Wiley & Sons, 2008Chapter in book (Refereed)
  • 636.
    Ågren, Hans
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Norman, Patrick
    Baev, Alexander
    Multiphysics modelling of optical materials2006In: Optical Materials in Defence Systems Technology III / [ed] Grote, JG; Kajzar, F; Lindgren, M, BELLINGHAM, WA: SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6401, p. U8-U24Conference paper (Refereed)
    Abstract [en]

    We review multiphysics modeling of pulse propagation in non-linear media and highlight some recent applications on optical materials containing organic or organometallic chromophores.

  • 637.
    Ågren, Hans
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Modeling of Non-linear Optic Properties of Guest-Host Systems2006In: Nonlinear Optics, Quantum Optics: concepts in modern optics, ISSN 1543-0537, Vol. 35, no 1-3, p. 39-55Article in journal (Refereed)
    Abstract [en]

    In this paper we summarize our recent work in computer modeling of nonlinear optical (NLO) properties of guest-host systems. The modeling involves quantum chemistry calculations to predict the NLO properties of a single chromophore molecule and molecular dynamics simulations to estimate the macroscopic NLO properties of the corresponding guest-host systems and to find the microscopic origin behind the macroscopic properties. The systems studied cover solutions solvated with NLO chromophores and amorphous polymers doped with dipolar chromophore molecules. Some gained insight and conclusions obtained from the combined modeling approaches are presented.

  • 638.
    Ågren, Hans
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Modelling nonlinear optical effects in guest-host systems2005In: Chinese Optics Letters (COL), ISSN 1671-7694, Vol. 3, no Suppl., p. S17-S22Article in journal (Refereed)
    Abstract [en]

    We briefly outline a modelling strategy, combining quantum chemistry and molecular dynamics simulations, for obtaining macroscopic nonlinear optical coefficients in guest-host systems like chromophores in solutions or in polymer matrices. The parameters required for the calculation of the macroscopic nonlinear optical property, like the chromophore number density, local field factors, and the order parameter of the chromophore molecules, are derived. These parameters, together with the molecular first hyperpolarizabilities, obtained from quantum chemistry calculations, are used to estimate the macroscopic electro-optic coefficients. The combined approach leads to some new conclusions about the relation of the chromophore property and its solvent interactions in order to optimize the nonlinear optical coefficient. For instance, from the simulation results a totally different notion is derived about the collective properties of octupolar molecules. We find that such molecules receive a solvent induced dipole moment that makes it possible to pole them by an external electric field, but also that they can aggregate as an effect of this solvent interaction.

  • 639. Şen, Pınar
    et al.
    Hirel, Catherine
    Andraud, Chantal
    Bretonnière, Yann
    Mohammed, Abdelsalam
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Minaev, Boris
    Minaeva, Valentina
    Baryshnikov, Gleb
    Lee, Hung-Hsun
    Duboisset, Julien
    Lindgren, Mikael
    Fluorescence and FTIR Spectra Analysis of Trans-A2B2-Substituted Di- and Tetra-Phenyl Porphyrins2010In: Materials, ISSN 1996-1944, no 8, p. 4446-4475Article in journal (Refereed)
    Abstract [en]

    A series of asymmetrically substituted free-base di- and tetra-phenylporphyrins and the associated Zn-phenylporphyrins were synthesized and studied by X-ray diffraction, NMR, infrared, electronic absorption spectra, as well as fluorescence emission spectroscopy, along with theoretical simulations of the electronic and vibration structures. The synthesis selectively afforded trans-A2B2 porphyrins, without scrambling observed, where the AA and BB were taken as donor- and acceptor-substituted phenyl groups. The combined results point to similar properties to symmetrically substituted porphyrins reported in the literature. The differences in FTIR and fluorescence were analyzed by means of detailed density functional theory (DFT) calculations. The X-ray diffraction analysis for single crystals of zinc-containing porphyrins revealed small deviations from planarity for the porphyrin core in perfect agreement with the DFT optimized structures. All calculated vibrational modes (2162 modes for all six compounds studied) were found and fully characterized and assigned to the observed FTIR spectra. The most intense IR bands are discussed in connection with the generic similarity and differences of calculated normal modes. Absorption spectra of all compounds in the UV and visible regions show the typical ethio type feature of meso-tetraarylporphyrins with a very intense Soret band and weak Q bands of decreasing intensity. In diphenyl derivatives, the presence of only two phenyl rings causes a pronounced hypsochromic shift of all bands in the absorption spectra. Time-dependent DFT calculations revealed some peculiarities in the electronic excited states structure and connected them with vibronic bands in the absorption and fluorescence spectra from associated vibrational sublevels.

10111213 601 - 639 of 639
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