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  • 751.
    Zhang, Rui
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, Xianbiao
    Wang, Huifang
    Zhang, Yao
    Jiang, Song
    Hu, Chunrui
    Zhang, Yang
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Dong, Zhenchao
    Distinguishing Individual DNA Bases in a Network by Non-Resonant Tip-Enhanced Raman Scattering2017In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, no 20, p. 5561-5564Article in journal (Refereed)
    Abstract [en]

    The importance of identifying DNA bases at the single-molecule level is well recognized for many biological applications. Although such identification can be achieved by electrical measurements using special setups, it is still not possible to identify single bases in real space by optical means owing to the diffraction limit. Herein, we demonstrate the outstanding ability of scanning tunneling microscope (STM)-controlled non-resonant tip-enhanced Raman scattering (TERS) to unambiguously distinguish two individual complementary DNA bases (adenine and thymine) with a spatial resolution down to 0.9 nm. The distinct Raman fingerprints identified for the two molecules allow to differentiate in real space individual DNA bases in coupled base pairs. The demonstrated ability of non-resonant Raman scattering with super-high spatial resolution will significantly extend the applicability of TERS, opening up new routes for singlemolecule DNA sequencing.

  • 752. Zhang, Song Bin
    et al.
    Kimberg, Victor
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Siberian Federal University, Russian Federation.
    Rohringer, Nina
    Nonlinear resonant Auger spectroscopy in CO using an x-ray pump-control scheme2016In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 94, no 6, article id 06413Article in journal (Refereed)
    Abstract [en]

    In the present paper we propose nonlinear femtosecond x-ray pump-probe spectroscopy to study the vibrational dynamics of a core-excited molecular state and discuss numerical results in CO. A femtosecond pump resonantly excites the carbon core-excited 1s-1π∗ state of the CO molecule. A second strong probe (control) pulse is applied at variable delay and is resonantly coupled to a valence excited state of the molecule. The strong nonlinear coupling of the control pulse induces Rabi flopping between the two electronic states. During this process, a vibrational wave packet in the core-excited state is created, which can be effectively manipulated by changing the time delay between pump and control pulses. We present an analysis of the resonant Auger electron spectrum and the transient absorption or emission spectrum on the pump transition and discuss their information content for reconstruction of the vibrational wave packet.

  • 753. Zhang, T.
    et al.
    Brumboiu, Iulia
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Lanzilotto, V.
    Luder, J.
    Grazioli, C.
    Giangrisostomi, E.
    Ovsyannikov, R.
    Sass, Y.
    Bidermane, I.
    Stupar, M.
    de Simone, M.
    Coreno, M.
    Ressel, B.
    Pedio, M.
    Rudolf, P.
    Brena, B.
    Puglia, C.
    Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26372-26378Article in journal (Refereed)
    Abstract [en]

    The occupied and empty densities of states of cobalt phthalocyanine (CoPc) were investigated by photoelectron and X-ray absorption spectroscopies in the gas phase and in thin films deposited on a Au(111) surface. The comparison between the gas-phase results and density functional theory single-molecule simulations confirmed that the CoPc ground state is correctly described by the (2)A(1g) electronic configuration. Moreover, photon-energy-dependent valence photoemission spectra of both the gas phase and thin film confirmed the atomic character of the highest occupied molecular orbital as being derived from the organic ligand, with dominant contributions from the carbon atoms. Multiplet ligand-field theory was employed to simulate the Co L-edge X-ray absorption spectroscopy results.

  • 754. Zhang, W.
    et al.
    Wu, Y.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, E.
    Song, X.
    Jiang, H.
    Shen, C.
    Zhang, H.
    Tian, H.
    Zhu, W. -H
    Molecular engineering and sequential cosensitization for preventing the “trade-off” effect with photovoltaic enhancement2017In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 8, no 3, p. 2115-2124Article in journal (Refereed)
    Abstract [en]

    In dye-sensitized solar cells (DSSCs), it is essential to use rational molecular design to obtain promising photosensitizers with well-matched energy levels and narrow optical band gaps. However, the “trade-off” effect between the photocurrent and photovoltage is still a challenge. Here we report four benzoxidazole based D-A-π-A metal-free organic dyes (WS-66, WS-67, WS-68 and WS-69) with different combinations of π-spacer units and anchoring-acceptor groups. Either extending the π-spacer or enhancing the electron acceptor can efficiently modulate the molecular energy levels, leading to a red-shift in the absorption spectra. The optimal dye, WS-69, containing a cyclopentadithiophene (CPDT) spacer and cyanoacetic acid acceptor, shows the narrowest energy band gap, which displays a very high photocurrent density of 19.39 mA cm−2, but suffers from a relatively low photovoltage of 696 mV, along with the so-called deleterious “trade-off” effect. A cosensitization strategy is further adopted for enhancing the device performance. Optimization of the dye loading sequence is found to be capable of simultaneously improving the photocurrent and photovoltage, and distinctly preventing the “trade-off” effect. The superior cosensitized cell exhibits an excellent power-conversion efficiency (PCE) of 10.09% under one-sun irradiation, and 11.12% under 0.3 sun irradiation, which constitutes a great achievement in that the efficiency of a pure metal-free organic dye with iodine electrolyte can exceed 11% even under relatively weak light irradiation. In contrast with the previous cosensitization strategy which mostly focused on compensation of light-harvesting, we propose a novel cosensitization architecture, in which the large molecular-sized, high photocurrent dye WS-69 takes charge of broadening the light-harvesting region to generate a high short-circuit current (JSC) while the small molecular-sized, high photovoltage dye WS-5 is responsible for retarding charge recombination to generate a high open-circuit voltage (VOC). In addition, adsorption amount and photo-stability studies suggest that the cyano group in the anchoring acceptor is important for the stability since it is beneficial towards decreasing the LUMO levels and enhancing the binding of dyes onto TiO2 nanocrystals.

  • 755. 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.

  • 756. 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%.

  • 757. 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.

  • 758. Zhang, Yue-Jiao
    et al.
    Li, Song-Bo
    Duan, Sai
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Lu, Bang-An
    Yang, Ji
    Panneerselvam, Rajapandiyan
    Li, Chao-Yu
    Fang, Ping-Ping
    Zhou, Zhi-You
    Phillips, David Lee
    Li, Jian-Feng
    Tian, Zhong-Qun
    Probing the Electronic Structure of Heterogeneous Metal Interfaces by Transition Metal Shelled Gold Nanoparticle-Enhanced Raman Spectroscopy2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 37, p. 20684-20691Article in journal (Refereed)
    Abstract [en]

    In heterogeneous catalysis, characterization of heterogeneous metal interfaces of bimetallic catalysts is a crucial step to elucidate the catalytic performance and is a key to develop advanced catalysts. However, analytical techniques such as X-ray photoelectron spectroscopy can only work in vacuum conditions and are difficult to use for in situ analysis. Here, we present efficient and convenient core-shell nano particle-enhanced Raman spectroscopy to explore the in situ electronic structures of heterogeneous interfaces (Au@Pd and Au@Pt core-shell NPs) by varying the shell thickness. The experimental observations reported here clearly show that Pd donates electrons to Au, while Pt accepts electrons from Au at the heterogeneous interfaces. This conclusion gains further support from ex situ X-ray photoelectron spectroscopy results. The Au core greatly affects the electronic structures of both the Pd and Pt shells as well as catalytic behaviors. Finally, the as prepared core-shell nanoparticles were used to demonstrate their improved catalytic properties in real electrocatalytic systems such as methanol oxidation and oxygen reduction reactions.

  • 759. Zhang, Z.
    et al.
    Zhang, J.
    Wu, B.
    Li, X.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Chen, Y.
    Huang, J.
    Zhu, L.
    Tian, H.
    Diarylethenes with a Narrow Singlet–Triplet Energy Gap Sensitizer: a Simple Strategy for Efficient Visible-Light Photochromism2018In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 6, no 6, article id 1700847Article in journal (Refereed)
    Abstract [en]

    All-organic visible-light photochromism is reported here via a novel strategy with narrow singlet–triplet energy gap (ΔEST) materials as a sensitizer. Taking advantage of the narrow ΔEST feature and the triplet–triplet energy transfer process, highly efficient photochromism of diarylethenes (DAEs) with both ring-open and ring-closure excitations shifted to visible light region is successfully achieved. Moreover, the wavelength of the visible excitation light can be easily modulated (e.g., from 405 to 470 nm) by elaborate selection of matched sensitized molecules. The “write-and-erase” application of this photochromic system in polymer films is further demonstrated. This strategy provides a simple and versatile selection of well-matched DAE/sensitizer couples for visible-light photochromism without complicated molecular design.

  • 760. 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.

  • 761. Zhou, Haitao
    et al.
    Huang, Wei
    Ding, Li
    Cai, Shengyun
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Bo
    Su, Jianhua
    New cyano-substituted organic dyes containing different electrophilic groups: aggregation-induced emission and large two-photon absorption cross section2014In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, no 39, p. 7050-7056Article in journal (Refereed)
    Abstract [en]

    Three aggregation-induced emission active dyes (3a-c) were synthesized and their one- and two-photon absorption properties have been investigated. They were all found to be weakly fluorescent in THF solution, while they exhibited dramatic fluorescence enhancement in water/THF mixtures. The solid fluorescence of 3a-c was recorded and their fluorescence quantum efficiency (Phi(F)) values were determined to be 8.0%, 8.1%, and 16.4%, respectively. Moreover, the two-photon absorption (2PA) cross-sections (sigma) of 3a-c were measured and 3a showed the highest value of 702 GM. The excellent aggregation-induced emission and 2PA properties provide a promising alternative for biophotonic materials.

  • 762.
    Zhou, Yang
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Multi-parametric stability investigation for thin spherical membranes with contacts2017In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 131-132, p. 334-344Article in journal (Refereed)
    Abstract [en]

    The instability behavior for a thin truncated spherical membrane completely filled with fluid or containing both gas and fluid, fixed on a circular platform and in contact with two vertical planes was investigated. Different penalty functions for contacts, and symmetry aspects of the discretized model were studied, and gave effects on instability behavior. Stability conclusions for the multi-parametric problems were made using generalized eigenvalue analyses, showing limit points, bifurcation points and turning point. Contact conditions were shown to introduce bifurcations and secondary paths, dependent on the contact implementations and discretizations. Their effects on stability behaviors in connection with various controlling equations are discussed.

  • 763. Zhou, Ying
    et al.
    Li, Xing
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Chen, Jue
    Yu, Fengtao
    Hua, Jianli
    The Effect of Pyridyl Nitrogen Atom Position in Pyrido-[3,4-b]pyrazines in Donor-Acceptor-pi-Acceptor Dyes on Absorption, Energy Levels, and Photovoltaic Performances of Dye-Sensitized Solar Cells2016In: ASIAN JOURNAL OF ORGANIC CHEMISTRY, ISSN 2193-5807, Vol. 5, no 2, p. 293-300Article in journal (Refereed)
    Abstract [en]

    A donor-acceptor-pi-acceptor (D-A-pi-A)-type organic dye (DTN-1) incorporating a pyrido[3,4-b]pyrazine (PP) unit with the pyridyl N atom adjacent to the anchoring group has been synthesized for use in dye-sensitized solar cells (DSSCs). The maximum absorption wavelength of DTN-1 was clearly red-shifted compared with dye DT-1, based on PP unit with the pyridyl N atom adjacent to the donor group. However, this change of structure has a negative effect on photovoltaic performances, and devices made with DTN-1 only reached a power conversion efficiency of 6.10% under AM1.5G irradiation compared with 8.57% achieved by DT-1. Density functional theory calculations suggest that DTN-1 has a smaller oscillator strength, which is connected to its relatively low light-harvesting efficiency. In addition, the results of electrochemical impedance spectroscopy (EIS) reveal that charge recombination in DSSCs based on DTN-1 is more than that in the counterpart DT-1, thus leading to a lower open-circuit voltage (V-oc).

  • 764. Zhou, Yunyun
    et al.
    Zhuang, Yaping
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yu, Lin
    Ding, Jiandong
    Zhu, Liangliang
    Selective Dual-Channel Imaging on Cyanostyryl-Modified Azulene Systems with Unimolecularly Tunable Visible-Near Infrared Luminescence2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 32, p. 7642-7647Article in journal (Refereed)
    Abstract [en]

    Although organic light-emitting molecules have received a growing attention and applicability in modern bioimaging science, the design and control of complex photoluminescent properties in unimolecularly selective imaging remains a challenging topic. Considering that tunable multipathway imaging can be advantagedly connected with treatment processes in therapy, the integration of an azulene and a cyanostyryl moiety into one skeleton is carried out for the generation of in situ stimuli-responsive luminescent materials, with the aim to achieve tunable and effective emissions in distinct channels through smart molecular design on a single-molecular platform. This strategy takes advantage of 1) the Z/E isomerization of the cyanostyryl unit that can vary the push-pull effect of the substitution on azulene, accompanied by altering absorption and emission of individual excited states, and 2) an optimized excited-state regulation for opening a near infrared emissive channel and making up for a controllable dual-pathway luminescent system together with the utilization of visible emission. As exemplified by a demonstration of manipulating the luminescence at the cell level, the materials exhibit a superior application potential for unimolecularly selective imaging, labeling and probing events.

  • 765. 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.

  • 766. 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.

  • 767. 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.

  • 768. 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.

  • 769. 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.

  • 770. 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.

  • 771.
    Zhu, Ning
    et al.
    E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China.;E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China..
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Yuan
    Chinese Acad Sci, Key Lab Photochem Convers & Optoelect Mat, Tech Inst Phys & Chem, Beijing 100190, Peoples R China..
    Ma, Xiang
    E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China.;E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China..
    Photo-responsive chiral cyclic molecular switches based on stiff stilbene2016In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 125, p. 259-265Article in journal (Refereed)
    Abstract [en]

    Two novel photo-responsive chiral cyclic molecular switches constituted of stiff stilbene and binaphthyl moieties connected through alkyl chains of different length were fabricated. The cyclization synthetic strategy employed herein made it convenient to obtain the pure Z isomers rather than Z/E isomer mixtures. The detailed photo-switching behaviors of target compounds were studied by the UV-Vis absorption and circular dichroism spectra in dichloromethane. The twist angles of the binaphthyl of the switches were able to be reversibly modulated by Z/E isomerization of stiff stilbene unit under alternative UV light stimuli and influenced by the length of alkyl chain to some extent.

  • 772. Zhu, X.
    et al.
    Zou, Rongfeng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sun, P.
    Wang, Q.
    Wu, J.
    A supramolecular peptide polymer from hydrogen-bond and coordination-driven self-assembly2018In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 9, no 1, p. 69-76Article in journal (Refereed)
    Abstract [en]

    A terpyridine- and guanine-functionalized peptide was developed that could form different morphologies by self-assembly or coordination with Fe2+ in dimethyl sulfoxide. The self-assembly of the peptide is attributed to the G-quartet formation of a guanine moiety and intermolecular terpyridine π-π stacking. Upon the addition of Fe2+, a Fe2+-(terpyridine)2 complex is formed that turns the square-planar self-assembly to a three-dimensional self-assembly. As a consequence, a variety of interesting morphologies and chemical properties were observed. The self-assembled polymers were studied by nuclear magnetic resonance spectroscopy, ultraviolet-visible and fluorescence spectroscopy, viscosity measurement, circular dichroism, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and atomic force microscopy. This external stimuli driven self-assembly of a peptide may be further applied to drug delivery applications. 

  • 773. 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.

  • 774. 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.

  • 775. 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.

  • 776. Zou, Yidong
    et al.
    Liu, Yang
    Wang, Xiangxue
    Sheng, Guodong
    Wang, Suhua
    Ai, Yuejie
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Liu, Yunhai
    Hayat, Tasawar
    Wang, Xiangke
    Glycerol-Modified Binary Layered Double Hydroxide Nanocomposites for Uranium Immobilization via Extended X-ray Absorption Fine Structure Technique and Density Functional Theory Calculation2017In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 5, no 4, p. 3583-3595Article in journal (Refereed)
    Abstract [en]

    Novel, efficient, glycerol-modified nanoscale layered double hydroxides (rods Ca/Al LDH-Gl and flocculent Ni/Al LDH-Gl) were successfully synthesized by a simple one-step hydrothermal synthesis route and showed excellent adsorption capacities for U(VI) from aqueous solutions under various environmental conditions. The advanced spectroscopy analysis confirmed the existence of abundant oxygen-containing functional groups (e.g., C-O, O-C=O, and C=O) on the surfaces of Ca/AI LDH-Gl and Ni/Al LDH-Gl, which could provide enough free active sites for the binding of U(VI). The maximum adsorption capacities of Macro-application (Environment U(VI) calculated from the Sips model were 266.5 mg.g(-1) for Ca/Al LDH-Gl and 142.3 mg.g(-1) for Ni/Al LDH-Gl at 298.15 K, and the higher adsorption capacity of Ca/Al LDH-Gl might be due to more functional groups and abundant high-activity "Ca-O" groups. Macroscopic experiments proved that the interaction of U(VI) on Ca/Al LDH-Gl and Ni/Al LDH-Gl was due to surface complexation and electrostatic interactions. The extended Xray absorption fine structure analysis confirmed that U(IV) did not transformation to U(VI) on solid particles, and stable inner sphere complexes were not formed by reduction interaction but by chemical adsorption. The density functional theory (DFT) calculations further evidenced that the higher adsorption energies (i.e., E-ad = 4.00 eV for Ca/AI LDH-Gl-UO22+ and E-ad = 2.43 eV for Ca/Al LDH-Gl-UO2CO3) were mainly attributed to stronger hydrogen bonds and electrostatic interactions. The superior immobilization performance of Ca/AI LDH-Gl supports a potential strategy for decontamination of UO22+ from wastewater, and it may provide new insights for the efficient removal of radionuclides in environmental pollution cleanup.

  • 777. Zou, Yidong
    et al.
    Wang, Xiangxue
    Ai, Yuejie
    Liu, Yunhai
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Hongqing
    Hayat, Tasawar
    Alsaedi, Ahmed
    Hu, Wenping
    Wang, Xiangke
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    beta-Cyclodextrin modified graphitic carbon nitride for the removal of pollutants from aqueous solution: experimental and theoretical calculation study2016In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 37, p. 14170-14179Article in journal (Refereed)
    Abstract [en]

    A novel beta-cyclodextrin modified, multifunctional, layer-by-layer graphitic carbon nitride (g-C3N4/beta-CD) was successfully synthesized and applied as an effective adsorbent for the removal of methyl orange (MO) and Pb(II) from aqueous solutions under various environmental conditions (e.g., solution pH, solid content, contact time and temperature). The kinetic results indicated that the adsorption was dominated by chemisorption, and the higher adsorption capacity of g-C3N4/beta-CD was attributed to it having more oxygen-containing functional groups than g-C3N4. The Langmuir, Freundlich and Sips models were applied to simulate the adsorption isotherms of MO and Pb(II), and the results demonstrated that the adsorption of MO was attributed to multilayer adsorption, while the coverage adsorption of Pb(II) on the g-C3N4/beta-CD was monolayer adsorption. The thermodynamic parameters showed that the adsorption of both MO and Pb(II) was spontaneous and endothermic. The DFT calculations further evidenced the surface complexation and electrostatic interaction of Pb(II) on the g-C3N4 and g-C3N4/beta-CD, whereas, the interaction of MO with g-C3N4 and g-C3N4/beta-CD was mainly attributed to hydrogen bonds and strong pi-pi interactions. The results demonstrated that g-C3N4/beta-CD is a promising material for the efficient removal of organic and inorganic pollutants in environmental pollution remediation.

  • 778. Zou, Yidong
    et al.
    Wang, Xiangxue
    Ai, Yuejie
    Liu, Yunhai
    Li, Jiaxing
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Xiangke
    Coagulation Behavior of Graphene Oxide on Nanocrystallined Mg/AI Layered Double Hydroxides: Batch Experimental and Theoretical Calculation Study2016In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, no 7, p. 3658-3667Article in journal (Refereed)
    Abstract [en]

    Graphene oxide (GO) has attracted considerable attention because of its remarkable enhanced adsorption and multifunctional properties. However, the toxic properties of GO nanosheets released into the environment could lead to the instability of biological system. In aqueous phase, GO may interact with fine mineral particles, such as chloridion intercalated nanocrystallined Mg/Al layered double hydroxides (LDH-Cl) and nanocrystallined Mg/Al LDHs (LDH CO3), which are considered as coagulant molecules for the coagulation and removal of GO from aqueous solutions. Herein the coagulation of GO on LDHs were studied as a function of solution pH, ionic strength, contact time, temperature and coagulant concentration. The presence of LDH Cl and LDH-CO3 improved the coagulation of GO in solution efficiently, which was mainly attributed to the surface oxygen-containing functional groups of LDH Cl and LDH-CO3 occupying the binding sites of GO. The coagulation of GO by LDH-CI and LDH-CO3 was strongly dependent on pH and ionic strength. Results of coagulation of GO on LDHs was energetically favored by electrostatic interactions and hydrogen bonds, which was further evidenced by FTIR and XPS analysis. By integrating the experimental results, it was clear that LDH Cl could be potentially used as a cost-effective coagulant for the elimination of GO from aqueous solutions, which could efficiently decrease the potential toxicity of GO in the natural environment.

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