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  • 901.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xie, Sheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Enzyme- and Ruthenium-Catalyzed Dynamic Kinetic Resolution Involving Cascade Alkoxycarbonylations for Asymmetric Synthesis of 5-Substituted N-AryloxazolidinonesManuscript (preprint) (Other academic)
  • 902.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Zhang, Yan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Xie, Sheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lipase-catalyzed kinetic resolution of 3-phenyloxazolidin-2-one derivatives: Cascade O- and N-alkoxycarbonylations2016In: Catalysis communications, ISSN 1566-7367, E-ISSN 1873-3905, Vol. 82, p. 11-15Article in journal (Refereed)
    Abstract [en]

    A lipase-catalyzed, cascade kinetic resolution protocol has been established for the synthesis of 3-phenyloxazolidin-2-one derivatives with up to excellent enantioselectivities (95% ee). Candida antarctica lipase B showed high catalytic activity and stereoselectivity in sequential O- and N-alkoxycarbonylation processes.

  • 903.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Yan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xie, Sheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lipase-Catalyzed Kinetic Resolution of 3-Phenyloxazolidin-2-one Derivatives: CascadeO‐ and N‐AlkoxycarbonylationsManuscript (preprint) (Other academic)
  • 904. Zhang, Yuchen
    et al.
    Elawad, Mohammed
    Yu, Ze
    Jiang, Xiaoqing
    Lai, Jianbo
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian Univ Technol, Peoples R China.
    Enhanced performance of perovskite  solar cells with P3HT hole-transporting materials via molecular p-type doping2016In: RSC ADVANCES, ISSN 2046-2069, Vol. 6, no 110, p. 108888-108895Article in journal (Refereed)
    Abstract [en]

    The conducting polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) has been widely used as a polymeric hole-transporting material (HTM) in inorganic-organic perovskite solar cells (PSCs). However, pristine P3HT-based PSC devices typically exhibit mediocre overall performance, mainly due to its relatively low conductivity. Herein, we successfully introduced tetrafluoro-tetracyano-quinodimethane (F4TCNQ) as an efficient p-type dopant for P3HT as a HTM in mesoscopic PSCs. The overall performance was significantly enhanced after the introduction of F4TCNQ into P3HT. Under an optimal doping condition (1.0%, w/w), an impressive power conversion efficiency (PCE) of 14.4% was achieved, which was considerably higher than the pristine P3HT based devices (10.3%). The dramatic improvement of the PCE originated from the increase of the photocurrent density and fill factor, strongly correlated to the significant increase of the bulk conductivity of F4TCNQ doped P3HT. After doping with 1.0% F4TCNQ, the conductivity of the P3HT film was significantly increased by more than 50 times. UV-Vis and Fourier transform infrared spectroscopy (FTIR) measurements indicated that p-doping occurs via the electron transfer from the highest occupied molecular orbital (HOMO) level of P3HT to the lowest unoccupied molecular orbital (LUMO) level of the F4TCNQ, which led to a substantial increase of the bulk conductivity. Furthermore, PSCs based on the P3HT: F4TCNQ composite as a HTM also exhibited superior long-term stability under ambient conditions with a humidity of 40%. F4TCNQ was thus demonstrated to be an effective p-dopant for P3HT to improve the electrical properties and thereby the overall performance for highly efficient and stable PSCs.

  • 905. Zhao, Guang-Jiu
    et al.
    Chen, Rui-Kui
    Sun, Meng-Tao
    Liu, Jian-Yong
    Li, Guang-Yue
    Gao, Yun-Ling
    Han, Ke-Li
    Yang, Xi-Chuan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Photoinduced intramolecular charge transfer and S-2 fluorescence in thiophene-pi-conjugated donor-acceptor systems: Experimental and TDDFT studies2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 23, p. 6935-6947Article in journal (Refereed)
    Abstract [en]

    Experimental and theoretical methods were used to study newly synthesized thiophene-pi-cojugated donor-acceptor compounds, which were found to exhibit efficient intramolecular charge-transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. To gain insight into the solvatochromic behavior of these compounds, the dependence of the spectra on solvent polarity was studied on the basis of Lippert-Mataga models. We found that intramolecular charge transfer in these donor-acceptor systems is significantly dependent on the electron-with-drawing substituents at the thienyl 2-position. The dependence of the absorption and emission spectra of these compounds in methanol on the concentration of trifluoroacetic acid was used to confirm intramolecular charge-tranfer emission. Moreover, the calculated absorption and emission energies, which are in accordance with the experimental values, suggested that fluorescence can be emitted from different geometric confirmations. In addition, a novel S-2 fluorescence phenomenon for some of these compounds was also be observed. The fluorescence excitation spectra were used to confirm the S-2 fluorescence. We demonstrate that S-2 fluorescence can be explained by the calculated energy gap between the S-2 and S-1 states of these molecules. Furthermore, nonlinear optical behavior of the thiophene-pi-conjugated compound with diethylcyanomethylphosphonate substituents was predicted in theory.

  • 906. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Molecular Design and Performance of Hydroxylpyridium Sensitizers for Dye-Sensitized Solar Cells2013In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, no 11, p. 5227-5231Article in journal (Refereed)
    Abstract [en]

    Four hydroxylpyridium organic dyes were synthesized and applied in dye-sensitized solar cells (DSSCs). Hydroxylpyridium was introduced as an electron acceptor in donor-pi-conjugated bridge-acceptor (D-pi-A) system. The traditional anchoring groups, such as the carboxyl group, were replaced by hydroxyl group. It was found that the existence of the hydroxylpyridium exhibits a large effect on the absorption spectra of dyes JH401-JH404. For JH series of dyes, hexylthiophene was employed as the pi-conjugated bridge, and triphenylamine, phenothiazine, and their derivatives were used as the electron donor. The performances of the dyes with different structure were investigated by photophysical, photovoltaic, and electrochemical methods. When applied in the DSSCs, the sensitizer JH401 yields the best efficiency, 2.6% (J(sc) = 6.35 mA/cm(2), V-oc = 605 mV, FF = 67.696) under 100 mW/cm(2) light illumination. Its maximum incident photon-to-current conversion efficiency (IPCE) is 80% at 440 nm light wavelength, which is the highest IPCE value achieved with hydroxyl group adsorbent organic dyes so far.

  • 907. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    New Organic Dyes with a Phenanthrenequinone Derivative as the pi-Conjugated Bridge for Dye-Sensitized Solar Cells2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 25, p. 12936-12941Article in journal (Refereed)
    Abstract [en]

    A series of organic dyes based on a phenanthrenequinone derivative have been employed for the first time as a it-conjugated bridge in the molecular design of D-pi-A structured organic dyes. Photophysical and electrochemical properties of dyes JH201-JH203 have been systematically investigated. The result shows that dye JH202 exhibits a higher molar extinction coefficient and widened absorption spectrum than dye JH201. Upon replacing the butoxyltriphenylamiine electron donor with phenothiazine, a bathochromic shift absorption spectrum for dye JH203 was observed. When applied in dye-sensitized solar cells (DSSCs), the device sensitized by JH203 yields the best photo-to-current conversion efficiency of 6.0% under standard AM 1.5G illumination (100 rnW/cm(2)) with a short-circuit photocurrent density (J(sc)) of 11.1 mA/cm(2), an open circuit photovoltage (V-oc) of 720 mV, and a fill factor (ff) of 74.9%. The maximum incident photo-to-current conversion efficiency reaches 87% at 460 nm.

  • 908. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Wang, Xiuna
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Highly efficient iso-quinoline cationic organic dyes without vinyl groups for dye-sensitized solar cells2013In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 7, p. 2441-2446Article in journal (Refereed)
    Abstract [en]

    Four organic dyes without a vinyl group are synthesized and applied in dye-sensitized solar cells (DSSCs). The iso-quinoline cation is employed firstly as an electron acceptor in the dye molecular structure. The effect of different dye structures on the photo-electrochemical properties and the performance of the DSSCs are systematically studied. The photovoltaic performances of the DSSCs sensitized by the JH304 dye exhibit the best conversion efficiency of 7.3% (under standard AM 1.5G illumination (100 mW cm(-2))) with a short-circuit current density (J(sc)) of 14.4 mA cm(-2), an open-circuit voltage (V-oc) of 684 mV and a fill factor (ff) of 74.4%. In comparison, the device sensitized by the N719 dye shows an efficiency of 7.9%. The DSSC device sensitized by JH304 also exhibits excellent soaking stability under sunlight for 1000 h.

  • 909. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Wang, Weihan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Influence of different methylene units on the performance of rhodanine organic dyes for dye-sensitized solar cells2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 10, p. 4811-4816Article in journal (Refereed)
    Abstract [en]

    In D-p-A structured organic dyes, rhodanine acetic acid and its derivates have served as electron acceptors successfully. In this work, two single rhodanine organic dyes with different methylene units have been synthesized and applied in dye-sensitized solar cells (DSSCs). The photophysical, electrochemical and photovoltaic properties have been studied systematically. The results show that dye with double methylene units produces a higher photon-to-electron conversion efficiency (eta) of 4.5% than that of a single methylene unit dye with a eta of 4.1%. Also, it is interesting to notice that the lengthened distance between electron acceptor and TiO2 surface does not decrease the short-circuit current density (J(sc)) and IPCE response for both structured dyes. On the contrary, rhodanine dye bearing double methylene units exhibits a better J(sc) and IPCE response than the single methylene unit. The explanation for this trend is probably due to the fact that increased methylene units could suppress regeneration between the injected electron and the oxidized dye effectively.

  • 910. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Hao, Yan
    Cheng, Ming
    Tian, Jie
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Effect of Different Numbers of -CH2- Units on the Performance of Isoquinolinium Dyes2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 6, p. 3907-3914Article in journal (Refereed)
    Abstract [en]

    Three new dyes have been synthesized to investigate the influence of the distance between the electron acceptor and TiO2 surface on the performance of dye-sensitized solar cells (DSSCs). In these dyes, the isoquinolinium acceptor, with a -(CH2)(n) COOH anchoring group, and a functionalized triphenylamine donor are separated by an oligothiophene bridge. The physical and electrochemical properties of the dyes were investigated systematically. The results prove that different numbers of -CH2- units between the isoquinolinium acceptor and the carboxyl anchoring group have a less pronounced effect on the physical and electrochemical properties of these dyes. However, when applied in DSSCs, a sharp decrease in the short-circuit current (J(SC)) was observed with increasing numbers of -CH2- units. For example, the device containing the organic dye bearing three -CH2- units produced the lowest J(SC) of 7.94 mA.cm(-2). In contrast, the device containing the dye bearing only one -CH2- unit exhibited the highest J(SC) of 13.88 mA.cm(-2). The higher photocurrent obtained with the device incorporating the dye with one -CH2- unit resulted in a higher power conversion efficiency of 6.8%.

  • 911.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Conifer chemical defense: Rugulation of bark beetle colonization and pheromone emission2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Terpenes and phenols are of importance in conifer defense against insects and pathogens. Knowledge about tree chemical defense is vital for developing practical methods to maintain healthy forests. With the aims of characterizing the defensive chemical induction in Norway spruce Picea abies and demonstrating its ecological function to spruce bark beetle Ips typographus, we measured the terpenoid and phenolic content in the bark of mature Norway spruce trees suffering windstorm, inoculated with Ceratocystis polonica, or treated with methyl jasmonate (MeJA), and investigated the colonization and pheromone emission of I. typographus.

    All three stressors altered the chemical profile in the bark of Norway spruce. Trees damaged by windstorm had lower proportions of (+)-3-carene and two unidentified stilbenes, and a higher taxifolin glycoside content than trees without apparent windstorm damage; C. polonica inoculation induced extremely strong quantitative terpene accumulation in the wound reaction zone, but only increased the levels of (+)-3-carene, sabinene and terpinolene in the bark near the reaction zone; MeJA treatment generally elicited quantitative terpene accumulation, but the induction differed extensively between individual trees. In addition, logs from MeJA-treated tree showed much stronger wounding response compared to control logs.

    The chemical profile of Norway spruce affected the colonization and pheromone emission of I. typographus. In response to fungal inoculation, terpene present in the reaction zone inhibited the colonization of I. typographus in a dose-dependent manner. Host defense elicited by MeJA treatment reduced emissions of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two key aggregation pheromone components of I. typographus, and altered the ratio between the two components.

  • 912.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Axelsson, Karolin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, P.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fungal Symbionts of the Spruce Bark Beetle Synthesize the Beetle Aggregation Pheromone 2-Methyl-3-buten-2-ol2015In: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561Article in journal (Refereed)
    Abstract [en]

    Tree-killing bark beetles depend on aggregation pheromones to mass-attack their host trees and overwhelm their resistance. The beetles are always associated with phytopathogenic ophiostomatoid fungi that probably assist in breaking down tree resistance, but little is known about if or how much these fungal symbionts contribute to the beetles’ aggregation behavior. In this study, we determined the ability of four major fungal symbionts of the spruce bark beetle Ips typographus to produce beetle aggregation pheromones. The fungi were incubated on Norway spruce Picea abies bark, malt agar, or malt agar amended with 0.5 % 13C glucose. Volatiles present in the headspace of each fungus were analyzed for 7 days after incubation using a SPME autosampler coupled to a GC/MS. Two Grosmannia species (G. penicillata and G. europhioides) produced large amounts of 2-methyl-3-buten-2-ol (MB), the major component in the beetles’ aggregation pheromone blend, when growing on spruce bark or malt agar. Grosmannia europhioides also incorporated 13C glucose into MB, demonstrating that the fungi can synthesize MB de novo using glucose as a carbon source. This is the first clear evidence that fungal symbionts of bark beetles can produce components in the aggregation pheromone blend of their beetle vectors. This provides new insight into the possible ecological roles of fungal symbionts in bark beetle systems and may deepen our understanding of species interactions and coevolution in these important biological systems.

  • 913.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Eerbilgin, Nadir
    Krokene, Paal
    Host resistance elicited by methyl jasmonate reduces emission of aggregation pheromones by the spruce bark beetle: Ips typographus2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 167, no 3, p. 691-699Article in journal (Refereed)
    Abstract [en]

    We treated Norway spruce (Picea abies) stems with methyl jasmonate (MeJA) to determine possible quantitative and qualitative effects of induced tree defenses on pheromone emission by the spruce bark beetle Ips typographus. We measured the amounts of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two main components of the beetle's aggregation pheromone, released from beetle entrance holes, along with phloem terpene content and beetle performance in MeJA-treated and untreated Norway spruce logs. As expected, phloem terpene levels were higher and beetle tunnel length was shorter (an indication of poor performance) in MeJA-treated logs relative to untreated logs. Parallel to the higher phloem terpene content and poorer beetle performance, beetles in MeJA-treated logs released significantly less 2-methyl-3-buten-2-ol and (S)-cis-verbenol, and the ratio between the two pheromone components was significantly altered. These results suggest that host resistance elicited by MeJA application reduces pheromone emission by I. typographus and alters the critical ratio between the two main pheromone components needed to elicit aggregation. The results also provide a mechanistic explanation for the reduced performance and attractivity observed in earlier studies when bark beetles colonize trees with elicited host defenses, and extend our understanding of the ecological functions of conifer resistance against bark beetles.

  • 914.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, Paal
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Christiansen, Erik
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    The influence of Ceratocystis polonica inoculation and methyl jasmonate application on terpene chemistry of Norway spruce, Picea abies2010In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 71, no 11-12, p. 1332-1341Article in journal (Refereed)
    Abstract [en]

    Constitutive and inducible terpene production is involved in conifer resistance against bark beetles and their associated fungi. In this study 72 Norway spruce (Picea abies) were randomly assigned to methyl jasmonate (MJ) application, inoculation with the bluestain fungus Ceratocystis polonica, or no-treatment control. We investigated terpene levels in the stem bark of the trees before treatment, 30 days and one year after treatment using GC-MS and two-dimensional GC (2D-GC) with a chiral column, and monitored landing and attack rates of the spruce bark beetle, Ips typographus, on the trees by sticky traps and visual inspection. Thirty days after fungal inoculation the absolute amount and relative proportion of (+)-3-carene, sabinene, and terpinolene increased and (+)-alpha-pinene decreased. Spraying the stems with MJ tended to generally increase the concentration of most major terpenes with minor alteration to their relative proportions, but significant increases were only observed for (-)-beta-pinene and (-)-limonene. Fungal inoculation significantly increased the enantiomeric ratio of (-)-alpha-pinene and (-)-limonene 1 month after treatment, whereas MJ only increased that of (-)-limonene. One year after treatment, both MJ and fungal inoculation increased the concentration of most terpenes relative to undisturbed control trees, with significant changes in (-)-beta-pinene, (-)-beta-phellandrene and some other compounds. Terpene levels did not change in untreated stem sections after treatment, and chemical induction by MJ and C polonica thus seemed to be restricted to the treated stem section. The enantiomeric ratio of (-)-alpha-pinene was significantly higher and the relative proportions of ( -)-limonene were significantly lower in trees that were attractive to bark beetles compared to unattractive trees. One month after fungal inoculation, the total amount of diterpenes was significantly higher in putative resistant trees with shorter lesion lengths than in putative susceptible trees with longer lesions. Thus, terpene composition in the stem bark may be related to resistance of Norway spruce against I. typographus and C. polonica.

  • 915.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, Paal
    Hu, Jiang
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Christiansen, Erik
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Induced Terpene Accumulation in Norway Spruce Inhibits Bark Beetle Colonization in a Dose-Dependent Manner2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 10, p. e26649-Article in journal (Refereed)
    Abstract [en]

    Background: Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization. Methods: To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark. Results: Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m(-2)) and 2.6% as much gallery length (0.029 m m(-2) vs. 1.11 m m(-2)) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of similar to 100 mg terpene g(-1) dry phloem trees suffered only moderate beetle colonization, and above a high threshold of similar to 200 mg terpene g(-1) dry phloem trees were virtually unattacked. Conclusion/Significance: This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.

  • 916.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Långström, Bo
    Performance of Tomicus yunnanensis and Tomicus minor (Col., Scolytinae) on Pinus yunnanensis and Pinus armandii in Yunnan, Southwestern China2012In: Psyche, ISSN 0033-2615, p. 363767-Article in journal (Refereed)
    Abstract [en]

    Pine shoot beetles, Tomicus yunnanensis Kirkendall and Faccoli and Tomicus minor Hartig (Col., Scolytinae), have been causing substantial mortality to Yunnan pine (Pinus yunnanensis Franch) in Yunnan, southwestern China, whereas only a few Armand pine (Pinus armandii Franch) were attacked by the beetles. In order to evaluate the suitability of P. armandii as host material for the two Tomicus, adults of both Tomicus were caged on living branches and felled logs of the two pines during shoot feeding and trunk attack phase, respectively. More beetles survived on the living branches of P. yunnanensis than on P. armandii. Tomicus yunnanensis and T. minor produced similar progeny in the logs of the two pines. The sex ratio and developmental period were not affected by host species, but the brood beetles emerging from Armand pine weighed less than those from Yunnan pine, suggesting that P. armandii are less suitable to be host of T. yunnanensis and T. minor.

  • 917.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Solheim, Halvor
    Långström, Bo
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Storm-induced tree resistance and chemical differences in Norway spruce (Picea abies)2011In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 68, no 3, p. 657-665Article in journal (Refereed)
    Abstract [en]

    Windstorm is one of the most destructive environmental disturbance factors on forests, but its influence on conifer defense chemistry and susceptibility to insects and diseases is not well understood.

  • 918. Zhao, Zhenbo
    et al.
    Wang, Mei
    Dong, Weibing
    Li, Ping
    Yu, Ze
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Synthesis and characterization of carboxy-functionalized diiron model complexes of FeFe -hydrogenases: Decarboxylation of Ph2PCH2COOH promoted by a diiron azadithiolate complex2009In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 694, no 15, p. 2309-2314Article in journal (Refereed)
    Abstract [en]

    Two carboxy-functionalized diiron complexes [{(mu-SCH2)(2)X}{Fe(CO)(3)}{Fe(CO)(2)L}] (X = NC3H7, L = Ph2PCH2CH2COOH, 4; X = CH2, L = Ph2PCH2COOH, 5) were prepared, as biomimetic models of the [FeFe] hydrogenase active site, from the CO-replacement of [{(mu-SCH2)(2)NC3H7}Fe-2(CO)(6)] (1) and (mu-pdt)Fe-2(CO)(6) (2) by phosphine ligands in CH3CN at 40 degrees C, respectively. In contrast, the reaction of 1 with Ph2PCH2COOH under the same condition afforded complex [{(mu-SCH2)(2)NC3H7}{Fe(CO)(3)}{Fe- (CO)(2)(Ph2PCH3)}] (3) with a decarboxylated phosphine ligand. The molecular structures of complexes 3-5 were determined by X-ray crystallographic analyses, which show that they have similar frameworks with the phosphine ligand on the apical position. The interesting C-H center dot center dot center dot S contacts between the methylene hydrogen atoms of the PhCH2COOH ligand and the mu-S atoms of the pdt-bridge are found in the crystal of 5. According to the experimental evidence, a plausible mechanism, via sequential phosphine coordination, N-protonation, and decarboxylation steps, is proposed for the formation of 3 and for explanation of the contrastive reactivities of the adt- (2-aza-1,3-propanedithiolato) and the pdt-(1,3-propanedithiolato) bridged diiron complexes toward decarboxylation of the Ph2PCH2COOH ligand.

  • 919. Zheng, D.
    et al.
    Wang, M.
    Chen, L.
    Wang, N.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Redox reactions of [FeFe]-hydrogenase models containing an internal amine and a pendant phosphine2014In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, no 3, p. 1555-1561Article in journal (Refereed)
    Abstract [en]

    A diiron dithiolate complex with a pendant phosphine coordinated to one of the iron centers, [(μ-SCH2)2N(CH2C 6H4-o-PPh2){Fe2(CO)5}] (1), was prepared and structurally characterized. The pendant phosphine is dissociated together with a CO ligand in the presence of excess PMe3, to afford [(μ-SCH2)2N(CH2C 6H4-o-PPh2){Fe(CO)2(PMe 3)}2] (2). Redox reactions of 2 and related complexes were studied in detail by in situ IR spectroscopy. A series of new Fe IIFeI ([3]+ and [6]+), Fe IIFeII ([4]2+), and FeIFe I (5) complexes relevant to Hox, Hox CO, and Hred states of the [FeFe]-hydrogenase active site were detected. Among these complexes, the molecular structures of the diferrous complex [4]2+ with the internal amine and the pendant phosphine co-coordinated to the same iron center and the triphosphine diiron complex 5 were determined by X-ray crystallography. To make a comparison, the redox reactions of an analogous complex, [(μ-SCH2)2N(CH 2C6H5){Fe(CO)2(PMe 3)}2] (7), were also investigated by in situ IR spectroscopy in the absence or presence of extrinsic PPh3, which has no influence on the oxidation reaction of 7. The pendant phosphine in the second coordination sphere makes the redox reaction of 2 different from that of its analogue 7.

  • 920. Zheng, Dehua
    et al.
    Wang, Mei
    Chen, Lin
    Wang, Ning
    Cheng, Minglun
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, China.
    The influence of a S-to-S bridge in diiron dithiolate models on the oxidation reaction: a mimic of the H-ox(air) state of [FeFe]-hydrogenases2014In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, no 66, p. 9255-9258Article in journal (Refereed)
    Abstract [en]

    Two-electron oxidation of a diiron complex (1) containing a bulky S-to-S bridge with an exocyclic carbonyl group affords [1(OH)](+), which replicates the coordination structure and electronic configuration of H-ox(air), and the chemically reversible reaction between 1 and [1(OH)](+) mimics the bioprocess of interconversion of the inactive H-ox(air) and the active H-red states of the [FeFe]-hydrogenases.

  • 921. Zheng, Dehua
    et al.
    Wang, Mei
    Wang, Ning
    Cheng, Minglun
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    Effect of Bridgehead Steric Bulk on the Intramolecular C-H Heterolysis of [FeFe]-Hydrogenase Active Site Models Containing a P2N2 Pendant Amine Ligand2016In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 2, p. 411-418Article in journal (Refereed)
    Abstract [en]

    A series of pendant amine-containing [FeFe]-hydrogenase models, [X(CH2S-μ)2{Fe(CO)3}{Fe(CO)(P2 PhN2 Bn)}] (1H, X = CH2; 2Me, C(CH3)2; 3Et, C(CH2CH3)2; and P2 PhN2 Bn = 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) with different groups at the bridgehead carbon of the S-to-S linker were synthesized. The oxidations of these complexes as well as the reverse reduction reaction were studied by cyclic voltammetry and in situ IR spectroscopy. Regardless of the bridgehead steric bulk, all three complexes demonstrate intramolecular iron-mediated C(sp3)-H bond heterolytic cleavage with the assistance of the pendant amine base within the chelating diphosphine ligand in the two-electron oxidation process. X-ray crystallographic analysis shows that the doubly oxidized products, [1′H]+, [2′Me]+, and [3′Et]+, all have a rigid FeSC three-membered ring at the open apical site of the rotated iron center. The most noticeable difference in structures of the oxidized complexes is that the single CO ligand of the rotated Fe(P2 PhN2 Bn)(CO) unit in [1′H]+ and [2′Me]+ is found below the Fe⋯Fe vector, while in [3′Et]+ an unusually rotated Fe(P2 PhN2 Bn)(CO) moiety positions one of the P donors within the bidentate ligand under the Fe⋯Fe vector. The starting FeIFeI complexes can be recovered from their corresponding doubly oxidized complexes by reduction in the presence of Brönsted acid.

  • 922. Zheng, Dehua
    et al.
    Wang, Ning
    Wang, Mei
    Ding, Shengda
    Ma, Chengbing
    Darensbourg, Marcetta Y.
    Hall, Michael B.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Intramolecular Iron-Mediated C-H Bond Heterolysis with an Assist of Pendant Base in a [FeFe]-Hydrogenase Model2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 48, p. 16817-16823Article in journal (Refereed)
    Abstract [en]

    Although many metalloenzymes containing iron play a prominent role in biological C-H activation processes, to date iron-mediated C(sp(3-)H heterolysis has not been reported for synthetic models of Fe/S-metalloenzymes. In contrast, ample precedent has established that nature's design for reversible hydrogen activation by the diiron hydrogenase ([FeFe]-H(2)ase) active site involves multiple irons, sulfur bridges, a redox switch, and a pendant amine base, in an intricate arrangement to perform H-H heterolytic cleavage. In response to whether this strategy might be extended to C-H activation, we report that a [FeFe]-H2ase model demonstrates iron-mediated intramolecular C-H heterolytic cleavage via an agostic C-H interaction, with proton removal by a nearby pendant amine, affording Fe-II-[ Fe'(II)-CH- S] three-membered-ring products, which can be reduced back to 1 by (CpCo)-Co-2 in the presence of HBF4. The function of the pendant base as a proton shuttle was confirmed by the crystal structures of the N-protonated intermediate and the final deprotonated product in comparison with that of a similar but pendant-amine-free complex that does not show evidence of C-H activation. The mechanism of the process was backed up by DFT calculations.

  • 923.
    Zhou, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Regio- and Stereoselective Hydrosilylation of 1,3-Enynes Catalyzed by Palladium2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 7, p. 1444-1447Article in journal (Refereed)
    Abstract [en]

    In the presence of Pd(0) and a phosphine, hydrosilylation of 1,3-enynes with Me2SiHCI proceeds to yield dienylsilanes with the silicon function added to the internal alkyne carbon atom and with (E)-configuration of newly formed olefinic bond. The silanols isolated after hydrolysis of the primarily obtained products serve as precursors to conjugated dienes with different substitution patterns.

  • 924.
    Zhou, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Tunable cross coupling of silanols: Selective synthesis of heavily substituted allenes and butadienes2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 38, p. 15992-15999Article in journal (Refereed)
    Abstract [en]

    1,3-Dienyl-2-silanols with a wide range of substitution patterns are readily obtained by palladium-catalyzed silaboration of 1,3-enynes followed by Suzuki-Miyaura cross coupling with aryl bromides. Subsequent Hiyama-Denmark cross coupling with aryl iodides provides either 1,3- or 1,2-dienes in high yields. The site selectivity can be fully controlled by the choice of activator used in the coupling reaction. In the presence of strong bases such as NaOt-Bu, KOt-Bu, and NaH, clean formation of 1,2-dienes takes place via allylic rearrangement. In contrast, stereo- and site-selective formation of tetra- and trisubstituted 1,3-dienes results from use of Ag 2O and Bu 4NF·3H 2O, respectively, as activators. Under microwave heating at 100 °C the base-mediated cross couplings are largely accelerated and are completed within one hour or less. The ratio of diastereomeric allenes varies depending on the substitution pattern of the silanol and ranges from >99:1 to 52:48.

  • 925.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Butchosa, Nuria
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Jayawardena, H. Surangi N.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Glycan-Functionalized Fluorescent Chitin Nanocrystals for Biorecognition Applications2014In: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 25, no 4, p. 640-643Article in journal (Refereed)
    Abstract [en]

    A new platform based on chitin nanocrystals has been developed for biorecognition applications. TEMPO-oxidized chitin nanocrystals (TCNs) were labeled with a fluorescent imidazoisoquinolinone dye, and simultaneously conjugated with carbohydrate ligands, resulting in dually functionalized TCNs. The biorecognition properties of the nanocrystals were probed with lectins and bacteria, resulting in selective interactions with their corresponding cognate carbohydrate-binding proteins, as visualized by optical, fluorescence, STEM, and TEM imaging. This represents a new approach to multifunctional nanomaterials based on naturally occurring polymers, holding high potential for biomedical applications.

  • 926.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Hao, Nanjing
    De Zoyza, Thareendra
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. University of Massachusetts, United States.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lectin-gated, mesoporous, photofunctionalized glyconanoparticles for glutathione-responsive drug delivery2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 48, p. 9833-9836Article in journal (Refereed)
    Abstract [en]

    A stimuli-responsive drug delivery system based on fluorescent, lectin-gated, mesoporous glyconanoparticles has been developed and evaluated in normal- and cancer lung epithelial cells. The gating process proved efficient, exhibiting good sealing properties in the absence of the glutathione redox trigger, avoiding premature release in normal cells. In the presence of higher levels of glutathione in cancer cells, the lectin gate was rapidly opened and the anticancer drug released.

  • 927.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Jayawardana, Kalana
    University of Massachusetts, United States .
    Kong, Na
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ren, Yansong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hao, Nanjing
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. University of Massachusetts, United States .
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Trehalose-Conjugated Mesoporous Silica Nanoparticles for Efficient Delivery of Isoniazid into MycobacteriaManuscript (preprint) (Other academic)
  • 928.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Jayawardana, Kalana W.
    Kong, Na
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ren, Yansong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hao, Nanjing
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. University of Massachusetts, United States.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Trehalose-Conjugated, Photofunctionalized Mesoporous Silica Nanoparticles for Efficient Delivery of Isoniazid into Mycobacteria2015In: ACS BIOMATERIALS-SCIENCE & ENGINEERING, ISSN 2373-9878, Vol. 1, no 12, p. 1250-1255Article in journal (Refereed)
    Abstract [en]

    Glyconanoparticle carriers have been synthesized and efficiently delivered into mycobacteria. Mesoporous silica nanoparticles were functionalized with a,a-trehalose through azide-mediated surface photoligation, and loaded with the antitubercular drug isoniazid. The glyconanoparticles showed high isoniazid loading capacity and higher antimicrobial activity than the free drug.

  • 929.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Robles, Nuria
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    Dually functionalized chitin nanocrystals for biorecognition applications2013In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 246, p. 192-POLY-Article in journal (Other academic)
  • 930. Zhou, Xu
    et al.
    Li, Fei
    Li, Hua
    Zhang, Biaobiao
    Yu, Fengshou
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Photocatalytic Water Oxidation by Molecular Assemblies Based on Cobalt Catalysts2014In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 9, p. 2453-2456Article in journal (Refereed)
    Abstract [en]

    Chromophore-catalyst molecular assemblies towards visible light-driven water oxidation were synthesized by covalent integration of a light-harvesting complex [Ru(bpy)(3)](2+) (bpy= 2,2'-bipyridine) and a Co4O4 cubane water oxidation catalyst. The two components were assembled either in linear or macrocyclic configurations. In the presence of the sacrificial reagent, the Ru-Co metallocycle exhibits remarkable photocatalytic activity for oxygen evolution, which is one order of magnitude higher than that of a multicomponent system and exceeds that of a linear assembly by a factor of five, offering access to highly active photocatalyst through molecular design.

  • 931. Zhou, Xu
    et al.
    Li, Fei
    Li, Xiaona
    Li, Hua
    Wang, Yong
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Photocatalytic oxidation of organic compounds in a hybrid system composed of a molecular catalyst and visible light-absorbing semiconductor2015In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 2, p. 475-479Article in journal (Refereed)
    Abstract [en]

    Photocatalytic oxidation of organic compounds proceeded efficiently in a hybrid system with ruthenium aqua complexes as catalysts, BiVO4 as a light absorber, [Co(NH3)(5)Cl](2+) as a sacrificial electron acceptor and water as an oxygen source. The photogenerated holes in the semiconductor are used to oxidize molecular catalysts into the high-valent Ru-IV=O intermediates for 2e(-) oxidation.

  • 932. Zhou, Y.
    et al.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Dong, H.
    Organosilicon-mediated regioselective acetylation of carbohydrates2012In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 48, no 43, p. 5370-5372Article in journal (Refereed)
    Abstract [en]

    Organosilicon-mediated, regioselective acetylation of vicinal- and 1,3-diols is presented. Methyl trimethoxysilane or dimethyl dimethoxysilane was first used to form cyclic 1,3,2-dioxasilolane or 1,3,2-dioxasilinane intermediates, and subsequent acetate-catalyzed monoacylation was efficiently performed by addition of acetic anhydride or acetyl chloride under mild conditions. The reaction exhibited high regioselectivity, resulting in the same protection pattern as in organotin-mediated schemes.

  • 933. Zhu, Hongjun
    et al.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Photoelectrochemistry of mesoporous NiO electrodes in Iodide/Triiodide electrolytes2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 47, p. 17455-17458Article in journal (Refereed)
    Abstract [en]

    Mesoporous NiO electrodes were used in photoelectrochemical cells using iodide/triiodide-based redox electrolytes. Cathodic photocurrents were found upon visible light excitation. These photocurrents were enhanced when coumarin 343 dye was adsorbed at the NiO surface or when a unanchored dye (coumarin 337) was added to the electrolyte. The proposed reaction for photocurrent generation is as follows: in the absence of dyes, excitation of triiodide leads to the generation of diiodide radicals, which subsequently accept electrons from the NiO electrode. Enhanced photocurrent generation in the presence of dyes is possibly due to energy transfer from excited dye molecules to triiodide. Charge transport studies of C343-sensitized NiO suggest that hole transport in mesoporous NiO is due to hopping of positive charge between Ni-surface atoms.

  • 934. Zhuang, Zanyong
    et al.
    Chen, Hong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lin, Zhang
    Dang, Zhi
    Mn2O3 hollow spheres synthesized based on an ion-exchange strategy from amorphous calcium carbonate for highly efficient trace-level uranyl extraction2016In: ENVIRONMENTAL SCIENCE-NANO, ISSN 2051-8153, Vol. 3, no 6, p. 1254-1258Article in journal (Refereed)
    Abstract [en]

    Well-defined hierarchical hollow spheres constructed from Mn2O3 quantum dots were prepared via an ion-exchange strategy starting from small-sized amorphous calcium carbonate. They show outstanding capability to extract trace-level uranyl from field water.

  • 935. Zierkiewicz, W.
    et al.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    A computational study of oxidation of ruthenium porphyrins via ORuIV and (ORuO)-O-VI species2006In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 15, p. 1867-1874Article in journal (Refereed)
    Abstract [en]

    An unrestricted density functional theory (UDFT) was applied to study the oxidation of ruthenium porphyrins, [RuP], via an interaction with molecular oxygen. The important role of dimeric [ RuP] complexes, i.e. [RuP]-O-2-[RuP], in the oxidation mechanism and particular in the cleavage of O-O bond of molecular oxygen has been studied. Geometries and relative Gibbs free energies of the intermediate Ru-complexes, i.e. dimeric oxo-Ru-porphyrins and O2RuII-(or O-2(-) Ru-III)-, ORuIV- and (ORuO)-O-VI-porphyrins, were evaluated along the proposed reaction pathway. The detailed thermodynamic data of the oxidation reaction [(RuP)-P-II] -> O[(RuP)-P-IV] -> O[(RuP)-P-VI]O and important aspects of the vibrational spectra of an oxo-[RuP] has been presented.

  • 936. Zierkiewicz, W.
    et al.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    A theoretical study of the essential role of DMSO as a solvent/ligand in the Pd(OAc)(2)/DMSO catalyst system for aerobic oxidation2005In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 24, no 24, p. 6019-6028Article in journal (Refereed)
    Abstract [en]

    Dimethyl sulfoxide (DMSO) has unique properties as an aprotic, polar solvent. The oxygen atom in DMSO can interact with positive charges and thus stabilize metal cation. The sulfur atom, although somewhat positively charged, does not interact with negative charges effectively. Also, two methyl groups surround the sulfur atom and influence binding properties of DMSO. These features of DMSO are addressed in the present computational study of the Pd(AcO)(2)/DMSO-catalyzed aerobic oxidation system. Mechanistic and computational details are provided. The step-by-step Gibbs energy of reaction was calculated using the electronic energy at the B3LYP density functional level with thermal functions calculated at the same level of theory. The solvent was modeled using the polarized medium (PCM) with additional DMSO molecules in the second coordination sphere of the complexes studied. The overall reaction pathway was divided into several steps in accord with available experimental data. All steps, including the first deprotonation and the beta-hydride elimination transition states, were elucidated in good detail. Coordination and reorganization of DMSO in Pd(II)(AcO)(2)/DMSO and Pd(0)/(DMSO)(n) complexes has been studied to provide realistic data about coordination of DMSO with hard (O) versus soft (S) ligand donor atoms. The P-hydride elimination transition state was identified computationally to give an estimation of the activation energy of the alcohol oxidation reaction. Therefore, we suggest that the rate-determining step is related to the alcohol part of the reaction cycle.

  • 937. Zietz, Burkhard
    et al.
    Gabrielsson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Johansson, Viktor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    El-Zohry, Ahmed M.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Photoisomerization of the cyanoacrylic acid acceptor group - a potential problem for organic dyes in solar cells2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 6, p. 2251-2255Article in journal (Refereed)
    Abstract [en]

    Organic solar cell dyes containing the most common anchoring group, cyanoacrylic acid, are shown to be photolabile and undergo photoisomerization. This may have significant consequences for dye-sensitized solar cells, as isomerisation competes with electron injection and leads to modifications of the dye and surface arrangement.

  • 938. Ziolek, Marcin
    et al.
    Cohen, Boiko
    Yang, Xichuan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Paulose, Maggie
    Varghese, Oomman K.
    Grimes, Craig A.
    Douhal, Abderrazzak
    Femtosecond to millisecond studies of electron transfer processes in a donor-(pi-spacer)-acceptor series of organic dyes for solar cells interacting with titania nanoparticles and ordered nanotube array films2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, no 8, p. 2816-2831Article in journal (Refereed)
    Abstract [en]

    Time-resolved emission and absorption spectroscopy are used to study the photoinduced dynamics of forward and back electron transfer processes taking place between a recently synthesized series of donor-(pi-spacer)-acceptor organic dyes and semiconductor films. Results are obtained for vertically oriented titania nanotube arrays (inner diameters 36 nm and 70 nm), standard titania nanoparticles (25 nm diameter) and, as a reference, alumina nanoparticle (13 nm diameter) films. The studied dyes contain a triphenylamine group as an electron donor, cyanoacrylic acid part as an electron acceptor, and differ by the substituents in a spacer group that causes a shift of its absorption spectra. Despite a red-shift of the dye absorption band resulting in an improved response to the solar spectrum, smaller electron injection rates and smaller extinction coefficients result in reduced dye sensitized solar cell (DSSC) conversion efficiencies. For the most efficient dye, TPC1, electron injection from the hot locally excited state to titania on a time scale of about 100 fs is suggested, while from the relaxed charge transfer state it proceeds in a non-exponential way with time constants from 1 ps to 50 ps. Our results imply that the latter process involves the trap states below the conduction band edge (or the sub-bandgap tail of the acceptor states), localized close to the dye radical cation, and is accompanied by fast electron recombination to the parent dye's ground state. This process should limit the efficiency of DSSCs made using these types of organic dyes. The residual, slower recombination can be described by a stretched exponential decay with a characteristic time of 0.5 ms and a dispersion parameter of 0.33. Both the electron injection and back electron transfer dynamics are similar in titania nanoparticles and nanotubes. Variations between the two film types are only found in the time resolved emission transients, which are explained in terms of the difference in local electric fields affecting the position of the emission bands.

  • 939. Ziolek, Marcin
    et al.
    Karolczak, Jerzy
    Zalas, Maciej
    Hao, Yan
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Douhal, Abderrazzak
    Aggregation and Electrolyte Composition Effects on the Efficiency of Dye-Sensitized Solar Cells. A Case of a Near-Infrared Absorbing Dye for Tandem Cells2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 1, p. 194-205Article in journal (Refereed)
    Abstract [en]

    Time-resolved laser spectroscopy studies of complete solar cells sensitized with a near-infrared absorbing dye (HY103) and filled with different electrolytes are applied to explain their macroscopic parameters (efficiency and short-circuit current). Particular attention is paid to the effect of coadsorbent, size of cations in electrolyte (lithium vs guanidine ones), and addition of tert-butylpyridine. A complete deactivation scheme in the cell is revealed, and the rates of electron injection and all other processes are explored. For the most efficient electrolyte, the electron injection rate constants are 0.21 ps(-1) from monomers and 0.07 ps(-1) from H-aggregates. Moreover, two important and novel findings are revealed: energy transfer from the excited state of monomers to H-aggregates (with rate constants from 0.04 to 0.25 ps(-1)) and the decrease of internal conversion rate in HY103 attached to the nanoparticles (0.01 ps(-1)) with respect to that of free dye in solution (0.06 ps(-1)). Thus, our study gives more clues to better understand the photobehavior of dye-sensitized solar cells.

  • 940. Ziolek, Marcin
    et al.
    Tacchini, Ignacio
    Martinez, M. Teresa
    Yang, Xichuan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Douhal, Abderrazzak
    A photo-induced electron transfer study of an organic dye anchored on the surfaces of TiO2 nanotubes and nanoparticles2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 9, p. 4032-4044Article in journal (Refereed)
    Abstract [en]

    We report on femtosecond-nanosecond (fs-ns) studies of the triphenylamine organic dye (TPC1) interacting with titania nanoparticles of different sizes, nanotubes and nanorods. We used time-resolved emission and absorption spectroscopy to measure the photoinduced dynamics of forward and back electron transfer processes taking place in TPC1-titania complexes in acetonitrile (ACN) and dichloromethane (DCM) solutions. We observed that the electron injection from the dye to titania occurs in a multi-exponential way with the main contribution of 100 fs from the hot excited charge-transfer state of anchored TPC1. This process competes with the relaxation of the excited state, mainly governed by solvation, that takes place with average time constants of 400 fs in ACN and 1.3 ps in DCM solutions. A minor contribution to the electron injection process takes place with longer time constants of about 1-10 ps from the relaxed excited state of TPC1. The latter times and their contribution do not depend on the size of the nanoparticles, but are substantially smaller in the case of nanotubes (1-3 ps), probably due to the caging effect. The contribution is also smaller in DCM than in ACN. The efficient back recombination takes place also in a multi-exponential way with times of 1 ps, 15 ps and 1 ns, and only 20-30% of the initial injected electrons in the conduction band are left within the first 1 ns after excitation. The faster recombination rates are suggested due to those originating from the free electrons in the conduction band of titania or the electrons in the shallow trap states, while the slower recombination is due to the electrons in the deep trap states. The results reported here should be relevant to a better understanding of the photobehaviour of an organic dye with promising potential for use in solar cells. They should also help to determine the important factors that limit the efficiency of solar cells based on the triphenylamine-based dyes for solar energy conversion.

  • 941. Ziolek, Marcin
    et al.
    Yang, Xichuan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Douhal, Abderrazzak
    Interrogating the ultrafast dynamics of an efficient dye for sunlight conversion2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 28, p. 8098-8107Article in journal (Refereed)
    Abstract [en]

    We report on studies of the recently synthesized compound (TPC1) with a promising potential use in dye-sensitized solar cells. We used steady-state as well as femtosecond (fs) to nanosecond (ns) time-resolved emission techniques to understand its behaviour under different conditions of solvation and light excitation. In polar solvents the equilibrium between TPC1 normal and anion structures was found to depend on solvent H-bond acceptor ability and concentration of the dye. We observed a correlation between the contribution of the normal form in the total absorption spectrum and solar energy conversion efficiency of the photovoltaic devices prepared in different baths, which are high in dichloromethane and low in tetrahydrofurane. Both forms exhibit a large charge transfer character in the excited state manifested by a large Stokes shift between absorption and emission maxima (up to 9000 cm(-1) in acetonitrile). The lifetime of the relaxed state of the normal structure varies significantly with the solvent polarity (from 80 ps in acetonitrile to 1.8 ns in n-hexane), and it is considerably shorter than that of the anion one (1.2-2.6 ns). The ultrafast relaxation processes are dominated by the solvation dynamics which is the fastest in acetonitrile (below 1 ps) and the slowest in ethanol (about 25 ps, the amplitude-averaged time). The results reported here should be relevant to a better understanding of the photobehaviour of metal-free dyes for solar cells and help in the design of new and more efficient dyes for conversion of light to electricity.

  • 942. Ziółek, M.
    et al.
    Martín, C.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Douhal, A.
    Effect of electrolyte composition on electron injection and dye regeneration dynamics in complete organic dye sensitized solar cells probed by time-resolved laser spectroscopy2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 50, p. 26227-26238Article in journal (Refereed)
    Abstract [en]

    Femtosecond time-gated fluorescence and nanosecond flash photolysis studies of seven complete, real titania nanoparticle solar cells sensitized with an efficient organic dye (TH305) were performed in order to investigate the role of the electrolyte composition on the charge transfer dynamics. The electron injection rate constants were found to range from 0.4 to 3.5 ps-1 in iodide-based electrolyte, and they well correlate with the shift of the conduction band edge potential of titania. The lithium cation additives resulted in 2 times faster electron injection rate constant (3.55 ps-1) with respect to that when larger sodium cations were used (1.86 ps-1). However, in the presence of a pyridine derivative component in the electrolyte solution, the electron injection rate constant decreased several times (0.38 ps-1 for Li+ and 0.54 ps-1 for Na+), while the electron injection efficiency was found to be still very high, 96-100%. The dye regeneration by the redox couple under relatively low fluence of excitation beam (0.4 mJ/cm2 giving about 4 electrons per titania nanoparticle) proceeds with an average rate constant of about 40 × 10 3 s-1 and efficiency close to 100%, independent of the electron composition. However, for a larger fluence (2 mJ/cm2) excitation, a titania-dye electron recombination process competes with the dye regeneration and lowers the solar cell efficiency. The effect of self-quenching, high vibrational levels of the dye excited state, and the neat solvent on the electron injection process are also discussed. This study clearly shows that for TH350-based DSSCs the best performance is obtained using Li+ and TBP as additives to the iodide electrolyte, giving the highest open circuit voltage and almost 100% efficiency of electron injection and dye regeneration.

  • 943. Zong, Xu
    et al.
    Na, Yong
    Wen, Fuyu
    Ma, Guijun
    Yang, Jinhui
    Wang, Donge
    Ma, Yi
    Wang, Mei
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Li, Can
    Visible light driven H-2 production in molecular systems employing colloidal MoS2 nanoparticles as catalyst2009In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 30, p. 4536-4538Article in journal (Refereed)
    Abstract [en]

    Colloidal MoS2 nanoparticles with diameters of less than 10 nm were prepared with a simple solvothermal method and demonstrated high efficiency in catalyzing H-2 evolution in Ru(bpy)(3)(2+)-based molecular systems under visible light.

  • 944.
    Zou, Dapeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Andersson, Samir
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Rong
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Shiguo
    Åkermark, Björn
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Selective binding of cucurbit 7 uril and beta-cyclodextrin with a redox-active molecular triad Ru(bpy)(3)-MV2+-naphthol2007In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 45, p. 4734-4736Article in journal (Refereed)
    Abstract [en]

    A 1:1:1 inclusion complex is formed by the binding interactions among beta-CD, CB[ 7] hosts, and Ru(bpy)(3)-terminated viologen naphthalene guest in aqueous solution, in which the positions of both CB[7] and beta-CD are closer to the Ru stopper than in the respective 1:1 inclusion complexes, forming a tightened nut on bolt'' structural mode.

  • 945.
    Zou, Dapeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Andersson, Samir
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Rong
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Shiguo
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Åkerrnark, Björn
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    A host-induced intramolecular charge-transfer complex and light-driven radical cation formation of a molecular triad with cucurbit 8 uril2008In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 73, no 10, p. 3775-3783Article in journal (Refereed)
    Abstract [en]

    The host-guest chemistry of systems containing a molecular triad Ru(bpy)(3)-MV2+-naphthol complex (denoted as Ru2+-MV2+-Np, 1) and cucurbit[8]uril (CB[8]) is investigated by NMR, EST-MS, UV-vis, and electrochemistry. The Ru2+-MV2+-Np guest and CB [8] host can form a stable 1:1 inclusion complex, in which the naphthalene residue is back-folded and inserted together with the viologen residue into the cavity of CB[8]. The selective binding of Ru2+-MV2+-Np guest with beta-CD and CB[8] host is also investigated. We find that CB[8] binds the Ru2+-MV2+-Np guest stronger than beta-CD. Upon light irradiation, a MV+center dot radical cation stabilized in the cavity of CB[8] accompanied by the naphthalene residue has been observed. This novel system may open a new way for design and synthesis of photoactive molecular devices.

  • 946.
    Åkerstedt, Josefin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Gorlov, Mikhail
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Synthesis and characterization of binuclear palladium(I) compounds and the influence of competing arenes2010In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 695, no 10-11, p. 1513-1517Article in journal (Refereed)
    Abstract [en]

    The binuclear palladium(I) compounds, [Pd-2(Ga2Cl7)(2)(C7H8)(2)] (1), [Pd-2(GaCl4)(2)(C9H12)(2)]center dot C9H12 (2) and [Pd-2(Ga2Cl7)(2)(C6H5Cl)(2)] (3), have been prepared from palladium(II) chloride in gallium(III) chloride-arene reaction media. All isolated crystalline solids (1, 2 and 3) have been structurally characterized by single crystal X-ray diffraction and Raman spectroscopy. The results form quantum chemical calculations on the interaction energies of the arenes and the dipalladium unit of these compounds is also presented.

  • 947.
    Åkerstedt, Josefin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Gorlov, Mikhail
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Synthesis of Bi5[GaCl4]3 from room-temperature ionic liquid reaction mediaManuscript (preprint) (Other academic)
16171819 901 - 947 of 947
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