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  • 251. Wood, Christopher J.
    et al.
    Cheng, Ming
    DUT-KTH Joint Research Centre on Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), China .
    Clark, Charlotte A.
    Horvath, Raphael
    Clark, Ian P.
    Hamilton, Michelle L.
    Towrie, Michael
    George, Michael W.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. DUT-KTH Joint Research Centre on Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), China .
    Yang, Xichuan
    Gibson, Elizabeth A.
    Red-Absorbing Cationic Acceptor Dyes for Photocathodes in Tandem Solar Cells2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 30, s. 16536-16546Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A pair of new donor-pi-acceptor dyes that absorb toward the red region of the visible spectrum (CAD 1 and CAD 2) utilizing indolium cationic acceptor units have been synthesized for use in p-type dye-sensitized solar cells (p-DSC). Their optical and electrochemical properties were determined experimentally, including application of ultrafast transient absorption and time-resolved infrared spectroscopies. Our results are supported by computational modeling. NiO-based p-DSCs with CAD 1 and CAD 2 gave short-circuit photocurrent densities of 3.6 and 3.3 mA cm(-2), respectively, which are substantially higher than that of any previous red-absorbing p-DSC. These results are a step toward tandem dye-sensitized solar cells that absorb higher-energy photons at the TiO2 anode and lower-energy photons at the NiO cathode. Routes to further improve the efficiency of NiO DSCS are also discussed.

  • 252.
    Xie, Zhen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Duan, Sai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Wang, Chuan-Kui
    Shandong Normal Univ, Shandong Prov Key Lab Med Phys & Image Proc Techn, Sch Phys & Elect, Jinan 250014, Shandong, Peoples R China..
    Luo, Yi
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Monitoring Hydrogen/Deuterium Tautomerization in Transient Isomers of Single Porphine by Highly Localized Plasmonic Field2019Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, nr 17, s. 11081-11093Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inner proton transfer between two trans isomers (tautomerization) in porphyrins plays a crucial role in many biological systems as well as molecular nanotechnology. Although the stepwise mechanism of tautomerization is well accepted, the involved intermediate cis-isomer has not been directly detected owing to its short lifetime and the extremely low intensities of corresponding hydrogen vibrations. Here, taking a single porphine as the prototype, we theoretically demonstrate that Raman intensities of the hydrogen vibrations become accessible under the highly localized plasmonic field because of the symmetry breaking effect. In addition, with the ultrafast incident excitations, we find that Raman signals of cis-porphine could be distinguished from the stable trans isomer, suggesting a general protocol for the direct characterization of transient isomers. Moreover, calculated results reveal that the position of inner hydrogen/deuterium can be unambiguously visualized from Raman images of the corresponding stretching modes, providing a unique optical means for the chemical monitoring of tautomerization in porphine and its derivatives.

  • 253. Xu, Fang
    et al.
    Mudiyanselage, Kumudu
    Baber, Ashleigh E.
    Soldemo, Markus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Weissenrieder, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    White, Michael G.
    Stacchiola, Dario J.
    Redox-Mediated Reconstruction of Copper during Carbon Monoxide Oxidation2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 29, s. 15902-15909Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Copper has excellent initial activity for the oxidation of CO, yet it rapidly deactivates under reaction conditions. In an effort to obtain a full picture of the dynamic morphological and chemical changes occurring on the surface of catalysts under CO oxidation conditions, a complementary set of in situ ambient pressure (AP) techniques that include scanning tunneling microscopy, infrared reflection absorption spectroscopy (IRRAS), and X-ray photoelectron spectroscopy were conducted. Herein, we report in situ AP CO oxidation experiments over Cu(111) model catalysts at room temperature. Depending on the CO:O-2 ratio, Cu presents different oxidation states, leading to the coexistence of several phases. During CO oxidation, a redox cycle is observed on the substrate's surface, in which Cu atoms are oxidized and pulled from terraces and step edges and then are reduced and rejoin nearby step edges. IRRAS results confirm the presence of under-coordinated Cu atoms during the reaction. By using control experiments to isolate individual phases, it is shown that the rate for CO oxidation decreases systematically as metallic copper is fully oxidized.

  • 254.
    Yang, Miao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Evaluation of the O-2 and pH Effects on Probes for Surface Bound Hydroxyl Radicals2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 15, s. 7971-7979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interfacial reactions between H2O2 and metal oxides are important in several fields but are yet not fully understood. Recently, tris(hydroxymethyl)aminomethane (Tris) was used as a probe in detecting the intermediate hydroxyl radical (HO center dot) during such process via the formation of formaldehyde (CH2O). In this work, we evaluate two probes (methanol and Tris) for detection of surface bound HO center dot by investigating the O-2 and pH effects on the production of formaldehyde. Moreover, we also examine the pH effect on the production of formaldehyde from Tris in the catalytic decomposition of H2O2 on ZrO2. The influence of O-2 and pH on the yield of formaldehyde under homogeneous conditions was studied via gamma-radiolysis of water. The solution was either deoxygenated or saturated with gas containing 20% 02, and the pH was ranging from 7.0 to 9.0. In the gamma-radiolysis experiment, O-2 shows a strong impact on the yield of formaldehyde: 14-68% for methanol and 16-29% for Tris. However, during the catalytic decomposition of H2O2, O-2 only enables a 30% enhancement of the production of CH2O when using Tris as the scavenger. While for methanol, the O-2 effect is almost negligible, and the production of CH2O from Tris is much higher than that from methanol. For practical reasons, only Tris was studied when evaluating the pH effect. A significant increase in the production of formaldehyde is observed by increasing pH during gamma-radiolysis of water while an even more pronounced pH-dependent increase is observed in the catalytic decomposition of H2O2 on ZrO2. The former indicates that the scavenging yield is base-catalyzed while the latter indicates that the formation of HO center dot is also base-catalyzed. On the basis of the observed effects of O-2 and pH, we propose a mechanism for the production of formaldehyde from Tris. The mechanism accounts for the observed impacts of O-2 and pH on the yield of formaldehyde.

  • 255.
    Yang, Miao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Zhang, Xian
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Grosjean, Alex
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Soroka, Inna
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Kinetics and Mechanism of the Reaction between H2O2 and Tungsten Powder in Water2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 39, s. 22560-22569Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the reaction between H2O2 and tungsten powder in the presence of Tris(hydroxymethyl) aminomethane was studied experimentally. The production of hydroxyl radicals can be quantified indirectly by quantifying the scavenging product formaldehyde (CH2O). XRD, XPS, and SEM analysis shows that no significant structural or compositional changes occur after reaction. We compared H2O2 consumption and CH2O formation in both heterogeneous W(s)/H2O2/Tris system and homogeneous W(aq)/H2O2/Tris system. Increasing the amount of W powder leads to the increase in dissolution rate of W species, insignificant increase of H2O2 consumption rate and the decrease of final CH2O production. By contrast, the consumption rate of H2O2 increases as increasing the concentration of dissolved W species. Based on the experimental results, a mechanism of H2O2 reacting with W powder in the presence of Tris is proposed. The mechanism well explained the relationship between surface reactions and homogeneous Haber–Weiss peroxide chain breakdown.

  • 256.
    Yang, Wenxing
    et al.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden.;Imperial Coll London, Dept Chem, London SW7 2AZ, England..
    Hao, Yan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Kloo, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Carrier Dynamics of Dye Sensitized-TiO2 in Contact with Different Cobalt Complexes in the Presence of Tri(p-anisyl)amine Intermediates2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 26, s. 14345-14354Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heterogeneous charge transfer processes at sensitized wide bandgap semiconductor surfaces are imperative for both fundamental knowledge and technical applications. Herein, we focus on the investigation of carrier dynamics of a triphenylamine-based dye, LEG4, sensitized TiO2 (LEG4/TiO2) in contact with two types of electrolyte systems: pure cobalt-based electrolytes and in combination with an organic donor, tri(p-anisyl)amine (TPAA). Four different cobalt redox systems with potentials spanning a 0.3 V range were studied, and the carrier recombination and regeneration kinetics were monitored both at low and at high TiO2 (e(-)) densities (1.3 X 10(18) and 1.3 X 10(19) cm(-3), respectively). The results reveal that the introduction of the TPAA intermediate more effectively suppress the recombination loss of TiO2 (e(-)) under high charge conditions, close to open-circuit, as compared to low charge conditions. As a result, the charge transfer from the cobalt complexes to the oxidized dyes is significantly improved by the addition of TPAA. Dye-sensitized solar cells fabricated with the TPAA-containing electrolytes demonstrate remarkable improvement in both V-OC and J(SC) and lead to more than 25% increase of the light-to-electricity conversion efficiency. Furthermore, an unprecedented detrimental impact of TPAA on the device performance was identified when the redox potential of the TPAA donor and the cobalt complexes are close. This is ascribed to the formation of TPAA(center dot+) which can act as an active recombination centers and thus lower the solar cell performance. These insights point at a strategy to enhance the lifetimes of electrons generated in sensitized semiconductor electrodes by overcoming the charge recombination between TiO2 and the oxidized dye under high carrier densities in the semiconductor substrate and offer practical guidance to the design of future efficient electrolyte systems for dye-sensitized solar cells.

  • 257.
    Yu, Shun
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Palmgren, Pal
    Hennies, Franz
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Modification of Charge Transfer and Energy Level Alignment at Organic/TiO2 Interfaces2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 31, s. 13765-13771Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption of titanyl phthalocyanine (TiOPc) on rutile TiO2(110) modified by a set of pyridine derivatives (2,2'-bipyridine, 4,4'-bipyridine, and 4-tert-butyl pyridine) has been investigated using synchrotron radiation based X-ray photoelectron spectroscopy (XPS). For the unmodified TiOPc/TiO2 system, a strong charge transfer is observed from the first layer TiOPc into the substrate, which leads to a molecular layer at the interface with a depleted highest occupied molecular orbital (HOMO). However, precovering the TiO2 surface with a saturated pyridine monolayer effectively reduce this process and leave the TiOPc in a less perturbed molecular state. Furthermore, the TiOPc HOMO and core levels are observed at different binding energies ranging by 0.3 eV on the three pyridine monolayers, which is ascribed to differences in surface potentials set up by the different pyridine/TiO2 systems.

  • 258.
    Yu, Shun
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Sun, Chenghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Palmgren, Pal
    Hennies, Franz
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    4-tert-Butyl Pyridine Bond Site and Band Bending on TiO2(110)2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 5, s. 2315-2320Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, we study the bonding of 4-tert-butyl pyridine (4TBP) to the TiO2(110) surface using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The results show that at low coverage, 4TBP adsorbs preferentially on oxygen vacancies. The calculated adsorption energy at the vacancies is 120 kJ/mol larger than that oil the five-fold-coordinated Ti4+ sites located in the rows on the TiO2 surface. The vacancy is "healed" by 4TBP, and the related gap state is strongly reduced through charge transfer into empty pi* orbitals on the pyridine ring. This leads to a change in surface band bending by 0.2 eV toward lower binding energies. The band bending does not change with further 4TBP deposition when saturating the surface to monolayer coverage, where the TiO2 surface is effectively protected against further adsorption by the dense 4TBP layer.

  • 259.
    Yu, Shun
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Sun, Chenghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Schulte, Karina
    Pietzsch, Annette
    Hennies, Franz
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy2011Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, nr 30, s. 14969-14977Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron transfer time is determined to be around 16 fs in the crystalline film, which is in good agreement with the charge-transfer hopping time estimated from the best device performance reported. The crystallized film shows more p-type characteristics than the amorphous with all the energy levels shifting toward the vacuum level. However, the greatly improved charge transfer is assigned to the molecular orbital coupling rather than this shift. From density functional theory and RPES, we specify the contribution of two differently coordinated nitrogen atoms (N2c and N3c) to the experimental results and illustrate that the N3c related orbital has experienced a dramatic change, which is keenly related to the improved charge transfer.

  • 260.
    Yu, Shun
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Deutsches Elektronen-Synchrotron (DESY), Germany.
    Santoro, Gonzalo
    Yao, Yuan
    Babonneau, David
    Schwartzkopf, Matthias
    Zhang, Peng
    Vayalil, Sarathlal Koyiloth
    Wessels, Philipp
    Doehrmann, Ralph
    Drescher, Markus
    Mueller-Buschbaum, Peter
    Roth, Stephan V.
    Following the Island Growth in Real Time: Ag Nanocluster Layer on A1q3 Thin Film2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 8, s. 4406-4413Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The progress of organic electronics demands an increased participation of nanotechnology, and it has already been shown that the presence of metallic nanoparticles and/or nanostructured thin films can enhance the device performance. Nevertheless, to gain control over the device final performance, it is crucial to achieve a profound understanding of the nanostructure development and assembly. We investigate the growth kinetics of silver (Ag) on a tris(8-hydroxyquinolinato)aluminum (Alq3) thin film via sputter deposition. The increase of the average electron density of the Ag nanostructured film is observed to follow a sigmoidal shape development as a function of the deposited Ag thickness, as a consequence of dominant island-mediated growth. The nanoclustered film is percolated at around a thickness of 5.0 +/- 0.1 nm. At this film thickness the effective film density is about 50%. Moreover, our simulation results indicate that the shape of the nanoclusters changes from truncated spheres to cylinders upon surpassing the percolation threshold.

  • 261.
    Yu, Ze
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Gorlov, Mikhail
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Boschloo, Gerrit
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Synergistic Effect of N-Methylbenzimidazole and Guanidinium Thiocyanate on the Performance of Dye-Sensitized Solar Cells Based on Ionic Liquid Electrolytes2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 50, s. 22330-22337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of additives guanidinium thiocyanate (GSCN) and N-methylbenzimidazole (MBI) on the photovoltaic performance of dye-sensitized solar cells based on low-viscous, binary ionic liquid and organic liquid electrolytes were investigated. Addition of only GSCN to the electrolyte has a pronounced influence on the short-circuit current, owing largely to the positive shift of the conduction band edge potential, probably increasing the injection efficiency of the excited dye. When only MBI was added to the electrolyte, a significant improvement of the open-circuit voltage was found, which could be attributed to a negative shift of the TiO2 conduction band edge potential and a longer electron lifetime under open-circuit conditions. Synergistic effects were observed when GSCN and MBI were used together in the ionic liquid-based electrolyte. In this case, optimal open-circuit voltage and total conversion efficiency were obtained among the ionic liquid electrolytes studied mainly due to the more efficient retardation of the recombination loss reaction at the TiO2/electrolyte interface.

  • 262.
    Yu, Ze
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Gorlov, Mikhail
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Nissfolk, Jarl
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Boschloo, Gerrit
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Investigation of Iodine Concentration Effects in Electrolytes for Dye-Sensitized Solar Cells2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 23, s. 10612-10620Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work describes the effects of different iodine concentrations and iodine-to-iodide ratios in electrolytes for dye-sensitized solar cells based on low-viscous, binary ionic liquid and organic liquid solvents. Current-voltage characteristics, photoelectrochemical measurements, electrochemical impedance spectroscopy, and Raman spectroscopy were used for characterization. Optimal short-circuit current and overall conversion efficiency were achieved using intermediate and low iodine concentration in ionic liquid-based and acetonitrile-based electrolytes, respectively. Results from photoelectrochemical and Raman-spectroscopic measurements reveal that both triiodide mobility and chemical availability affect the optimal iodine concentration required in these two types of electrolytes. The higher iodine concentrations required for the ionic liquid-based electrolytes partly compensate for these effects, although negative effects from higher recombination losses and light absorption of iodine-containing species start to become significant.

  • 263. Yuesheng, Ning
    et al.
    Jun, Jiang
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Ziliang, Shi
    Qiang, Fu
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Jianzhao, Liu
    Yi, Luo
    Ben Zhong, Tang
    Nian, Lin
    Single molecule's conductance depending on its orientation2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 1, s. 26-30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Single molecules of 1,1,2,3,4,5-hexaphenylsilole adsorbed on Cu(111) have been investigated using low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, and quantum chemistry calculations. Two adsorption states have been identified, showing distinctive tunneling conductance. The molecules can switch their states under tip influence. Theoretical calculations indicate that the two states are associated with molecules adsorbed at two 90°-rotated orientations, and the tunneling conductance is attributed to molecular orbitals that spatially bridge tip-to-substrate gap. Our findings demonstrate a decisive dependence of single-molecule conductance on the molecular orientation with respect to electrodes.

  • 264.
    Zakomirnyi, Vadim
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Federal Siberian Research Clinical Centre under FMBA of Russia, Kolomenskaya 26, Krasnoyarsk 660037, Russia; Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk 660036, Russia.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Department of Physics, Kaunas University of Technology, Kaunas LT-51368, Lithuania.
    Baryshnikov, Gleb V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Sørensen, Lasse K.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Federal Siberian Research Clinical Centre under FMBA of Russia, Kolomenskaya 26, Krasnoyarsk 660037, Russia; College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, Henan, P. R. China.
    The Extended Discrete Interaction Model: Plasmonic Excitations of Silver Nanoparticles2019Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, nr 47, s. 28867-28880Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a new atomistic model for plasmonic excitations and optical properties of metallic nanoparticles, which collectively describes their complete response in terms of fluctuating dipoles and charges that depend on the local environment and on the morphology of the composite nanoparticles. Being atomically dependent, the total optical properties, the complex polarizability, and the plasmonic excitation of a cluster refer to the detailed composition and geometric characteristics of the cluster, making it possible to explore the role of the material, alloy mixing, size, form shape, aspect ratios, and other geometric factors down to the atomic level and making it useful for the design of plasmonic particles with particular strength and field distribution. The model is parameterized from experimental data and, at present, practically implementable for particles up to more than 10 nm (for nanorods even more), thus covering a significant part of the gap between the scales where pure quantum calculations are possible and where pure classical models based on the bulk dielectric constant apply. We utilized the method to both spherical and cubical clusters along with nanorods where we demonstrate both the size, shape, and ratio dependence of plasmonic excitations and connect this to the geometry of the nanoparticles using the plasmon length.

  • 265. Zhang, Jinbao
    et al.
    Yang, Lei
    Shen, Yang
    Park, Byung-Wook
    Hao, Yan
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Gabrielsson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Jarboui, Adel
    Perruchot, Christian
    Jouini, Mohamed
    Vlachopoulos, Nick
    Hagfeldt, Anders
    Poly(3,4-ethylenedioxythiophene) Hole-Transporting Material Generated by Photoelectrochemical Polymerization in Aqueous and Organic Medium for All-Solid-State Dye-Sensitized Solar Cells2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 30, s. 16591-16601Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We applied organic donor-pi-acceptor (D-pi-A) sensitizers for photoelectrochemical polymerization (PEP) because of their appropriate energy levels and high light absorption. The polymerized conducting polymer PEDOT was used as hole conductor in all-solid-state dye-sensitized solar cells (ssDSCs). By combination of the D-pi-A sensitizers and the generated PEDOT from PEP of bis-EDOT in acetonitrile, the resulting device showed an average power conversion efficiency of 5.6%. Furthermore, the PEP in aqueous micellar electrolytic medium was also employed because of the ability to decrease oxidation potential of the precursor, thereby making the polymerization process easier. The latter method is a cost-effective and environmentally friendly approach. Using as hole conductor the so-obtained PEDOT from PEP of bis-EDOT in aqueous electrolyte, the devices exhibited impressive power conversion efficiency of 5.2%. To compare the properties of the generated polymer from bis-EDOT in these two PEP methods, electron lifetime, photoinduced absorption (PIA) spectra, and UV-vis-NIR spectra were measured. The results showed that PEDOT from organic PEP exhibits a delocalized conformation with high conductivity and a smooth and compact morphology; a rough morphology with high porosity and polymer structure of relatively shorter chains was assumed to be obtained from aqueous PEP. Therefore, better dye regeneration but faster charge recombination was observed in the device based on PEDOT from aqueous PEP of bis-EDOT. Subsequently, to extend the aqueous PEP approach in consideration of the ability to decrease the oxidation potential of the precursor, the easily available precursor EDOT was for the first time used for PEP in aqueous medium in a variant of the aforementioned procedure, and the device based on the so-obtained PEDOT shows a more than 70-fold increase in efficiency, 3.0%, over that based on the polymer generated from EDOT by PEP in organic media. It was demonstrated that aqueous micellar PEP with EDOT as monomer is an efficient strategy for generation of conducting polymer hole-transporting materials.

  • 266. Zhang, Lin
    et al.
    Kang, Zheng-Zhong
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. Zhejiang Univ, Dept Chem, Zheda Rd 38, Hangzhou 310027, Zhejiang, Peoples R China.
    Qi, Shi-Chao
    Liu, Xiao-Qin
    Wang, Zhi-Min
    Sun, Lin-Bing
    Ultradeep Removal of Moisture in Gases to Parts-per-Billion Levels: The Exploration of Adsorbents2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 5, s. 2840-2847Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Owing to the rigid standards of manufacturing semiconductor components, decrease of the moisture to parts-per-billion (ppb), at a global level, is always vital but extremely nerve-racking in the production of high-purity gases. Herein, typical adsorbents including oxides (SiO2 and gamma-Al2O3), zeolites (4A and NaX), and metal-organic frameworks (MOFs; HKUST-1, UiO-66, and ZIF-8) are investigated with respect to the abilities of ultradeep dewatering from N-2. Compared with other adsorbents, NaX performs much better on both dewatering efficiency (DE, from 2750 to 66 ppb) and the adsorption capacity (AC, 1.55 x 10(4) L N-2.g(-1)). Moreover, it is for the first time experimentally and theoretically proved that the dewatering ability of X zeolite mainly depends on its cation species (Na+, Li+, K+, Cs+, Mg2+, Ca2+, Sr2+, or Ba2+), the forces between the zeolite and H2O, and the number of H2O molecules per cell of the zeolite. CaX thus shows a fascinating DE from 2750 to 33 ppb, a huge AC of 9.08 x 10(4) L N-2.g(-1), and an ideal reusability, compared with results of the scarce contributions reported to date.

  • 267.
    Zhang, Pan
    et al.
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices.
    Wang, Mei
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices.
    Dong, Jingfeng
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices.
    Li, Xueqiang
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices.
    Wang, Feng
    Tech Inst Phys & Chem, Key Lab Photochem Convers & Optoelect Mat, Beijing.
    Wu, Lizhu
    Tech Inst Phys & Chem, Key Lab Photochem Convers & Optoelect Mat, Beijing.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Photocatalytic Hydrogen Production from Water by Noble-Metal-Free Molecular Catalyst Systems Containing Rose Bengal and the Cobaloximes of BFx-Bridged Oxime Ligands2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 37, s. 15868-15874Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrogen evolution was observed from the noble-metal-free catalyst systems, comprising Rose Bengal, BFx-bridged cobaloximes, and triethylamine, in an aqueous solution under irradiation of visible light. Two types of BFx-bridged cobaloximes namely, the annulated cobaloximes [Co(dmgBF(2))(2)(H2O)(2)] (1, dmgBF(2) = (difluoroboryl)dimethylglyoximate anion) and [Co(dpgBF(2))(2)(H2O)(2)] (2, dpgBF(2) =(difluoroboryl)diphenylglyoximate anion), and the clathrochelated cobaloximes [Co(dmg(BF)(2/3))(3)](BF4) (3) and [Co(dpg(BF)(2/3))(3)](BF4) (4)-were used as catalysts. Among the four cobalt complexes, complex 1 displayed the highest hydrogen-evolving efficiency, with turnovers up to 327. Complexes 2 and 4 that bear the diphenylglyoximate ligands exhibited much lower efficiencies as compared with their analogues 1 and 3 that have the dimethylglyoximate ligands. The hydrogen-evolving efficiency of the annulated cobalt(II) complex 1 that contains two labile axial ligands is more than three times as high as that of the encapsulated cobalt(III) complex 3 that has a single macrobicyclic ligand. The different pathways for formation of the cobalt(I) species from these two types of cobaloximes are discussed on the basis of the results obtained from fluorescence and laser flash photolysis spectroscopic studies.

  • 268.
    Zhang, T.
    et al.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Brumboiu, I. E.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Grazioli, C.
    Sincrotrone Trieste, CNR, ISM, I-34149 Trieste, Basovizza, Italy..
    Guarnaccio, A.
    CNR, ISM, I-85050 Potenza, Italy..
    Coreno, M.
    Sincrotrone Trieste, CNR, ISM, I-34149 Trieste, Basovizza, Italy..
    de Simone, M.
    Sincrotrone Trieste, Lab TASC, CNR, IOM, I-34149 Trieste, Basovizza, Italy..
    Santagata, A.
    CNR, ISM, I-85050 Potenza, Italy..
    Rensmo, H.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Brena, B.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Lanzilotto, V.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Puglia, C.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 31, s. 17706-17717Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Triphenylamine (TPA) and its thiophene-analog, N,N-diphenyl-2-thiophenamine (DPTA), are both well-known as electron-donating molecules implemented in optoelectronic devices such as organic solar cells and LEDs. Comprehensive valence and core level photoelectron spectroscopy, as well as near edge X-ray absorption spectroscopy (NEXAFS), measurements have been performed on gas phase TPA and DPTA. The experimental results have been compared to density functional theory calculations, providing a detailed description of the molecular electronic structure. Specifically, the C 1s photoelectron lines of both TPA and DPTA were resolved in the different C atom contributions and their binding energies explained as the result of two counter-acting effects: (1) the electronegativity of the nitrogen atom (and sulfur atom in DPTA) and (2) the the N (and S in DPTA) lone-pair electrons. In addition, the C K-edge NEXAFS spectrum of DPTA reveals that the lowest unoccupied molecular orbital (LUMO) energy position is affected differently if the core hole site is on the phenyl compared to the thiophene ring. The electron-donating properties of these two molecules are largely explained by the significant contribution of the N lone-pair electrons (p(z)) to the highest occupied molecular orbital. The contribution to the LUMO and to the empty density of states of the sulfur of the thiophene ring in DPTA explains the better performance of donor-pi-acceptor molecules containing this moiety and implemented in photoenergy conversion devices.

  • 269. Zhang, T.
    et al.
    Brumboiu, Iulia
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    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 Study2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 47, s. 26372-26378Artikel i tidskrift (Refereegranskat)
    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.

  • 270.
    Zhang, Wenhua
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Li, Zhenyu
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Yang, Jinlong
    First Principles Study on the Geometric and Electronic Structures of the FeO/Pt(111) Surface2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 19, s. 8302-8305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The geometric, electronic, and magnetic properties of the FeO monolayer on a Pt(111) surface are investigated by first principles calculations. Generally, antiferromagnetic (AFM) structures are more stable than that of the ferromagnetic one. On the basis of a specific AFM structure, the long puzzling scanning tunneling microscopy (STM) experimental observations can be well explained. In this AFM model, the Fe-O layer distance at the fee region is larger than the hcp region, in contrast to previous theoretical results. The STM images at the field-emission regime are explained by local surface potential.

  • 271. Zhang, Yue-Jiao
    et al.
    Li, Song-Bo
    Duan, Sai
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    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 Spectroscopy2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 37, s. 20684-20691Artikel i tidskrift (Refereegranskat)
    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.

  • 272. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Li, Shifeng
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    New Organic Dyes with a Phenanthrenequinone Derivative as the pi-Conjugated Bridge for Dye-Sensitized Solar Cells2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 25, s. 12936-12941Artikel i tidskrift (Refereegranskat)
    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.

  • 273. Zhu, Hongjun
    et al.
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Boschloo, Gerrit
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Photoelectrochemistry of mesoporous NiO electrodes in Iodide/Triiodide electrolytes2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 47, s. 17455-17458Artikel i tidskrift (Refereegranskat)
    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.

  • 274. Ziolek, Marcin
    et al.
    Karolczak, Jerzy
    Zalas, Maciej
    Hao, Yan
    Tian, Haining
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    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 Cells2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 1, s. 194-205Artikel i tidskrift (Refereegranskat)
    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.

  • 275. Ziółek, M.
    et al.
    Martín, C.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    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 spectroscopy2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 50, s. 26227-26238Artikel i tidskrift (Refereegranskat)
    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.

  • 276.
    Önsten, Anneli
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Stoltz, Dunja
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Palmgren, Pål
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Yu, Shun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Water Adsorption on ZnO(0001): Transition from Triangular Surface Structures to a Disordered Hydroxyl Terminated phase2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 25, s. 11157-11161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present room temperature scanning tunneling microscopy and photoemission spectroscopy studies of water adsorption on the Zn-terminated ZnO(0001) surface. Data indicates that the initial adsorption is dissociative leaving hydroxyl groups on the surface. At low water coverage, the adsorption occurs next to the oxygen-terminated step edges, where water is believed to bind to zinc cations leaving off hydrogen atoms to under-coordinated oxygen anions. When increasing the water dose, triangular terraces grow in size and pits diminish until the surface is covered with wide irregular terraces and a large number of small pits. Higher water exposure (20 Langmuir) results in a much more irregular surface. Hydrogen, which is produced in the dissociation reaction is believed to have an important role in the changed surface structure at high exposures. The fact that adsorbed water completely changes the structure of ZnO(0001) is an important finding toward the understanding of this surface at atmospheric conditions.

  • 277.
    Önsten, Anneli
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Weissenrieder, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Stoltz, Dunja
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Yu, Shun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Role of defects in surface chemistry on Cu2O(111)2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 38, s. 19357-19364Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-resolution photoemission spectroscopy and scanning tunneling microscopy (STM) have been used to investigate defects on Cu2O(111) and their interaction with water and sulfur dioxide (SO2). Two types of point defects, i.e., oxygen and copper vacancies, are identified. Copper vacancies are believed to be the most important defects in both water and SO2 surface chemistry. Multiply coordinatively unsaturated oxygen anions (OMCUS) such as oxygen anions adjacent to copper vacancies are believed to be adsorption sites for both water and SO2 reaction products. Water adsorption at 150 K results in both molecular and dissociated water. Molecular water leaves the surface at 180 K. At 300 K and even more at 150 K, SO2 interacts with oxygen sites at the surface forming SO 3 species. However, thermal treatment up to 280 K of Cu 2O(111)/SO2 prepared at 150 K renders only SO4 on the surface.

3456 251 - 277 av 277
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