The Experts below are selected from a list of 5025 Experts worldwide ranked by ideXlab platform
Shining Bao - One of the best experts on this subject based on the ideXlab platform.
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The chemisorption of tetracene on Si(100)-2×1 surface
The Journal of chemical physics, 2009Co-Authors: Hongying Mao, Hanjie Zhang, Fei Song, Weidong Dou, Dandan Guan, Meiliang Chen, Shining BaoAbstract:The adsorption of tetracene on Si(100)-2×1 substrate has been studied by ultraviolet photoemission spectroscopy (UPS). Six features deriving from the organic material are located at 1.22, 2.41, 3.63, 4.67, 7.11, and 8.77 eV below the Fermi level. These features shift in binding energy with increasing the thickness of the organic film. In the case of a monolayer, angle-resolved UPS measurements suggest that the molecular plane is parallel to the substrate. Further theoretical density functional theory calculation reveals the most stable structure of tetracene molecule on Si substrate in which six covalent Si–C chemical bonds are formed between carbon atoms of the tetracene molecule and the Si atoms on the substrate.
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Study on the interaction between tetracene and Cu(110) surface.
The Journal of chemical physics, 2007Co-Authors: Weidong Dou, Shining Bao, Hanjie Zhang, Han Huang, Fei Song, Dandan Guan, Qiao ChenAbstract:The electronic structure of tetracene on Cu (110) surface has been studied by using ultraviolet photoemission spectroscopy (UPS). The emission features from the organic molecule are located from 1 to 10 eV below the Fermi level, and they shift in binding energy with increasing the coverage of the organic material. For the surface with multilayer of tetracene, six well-resolved features were found at 1.90, 3.40, 4.70, 5.95, 6.95, and 9.15 eV below the Fermi level, respectively. On the surface with a lower coverage of tetracene, angle-resolved UPS measurements suggest that the molecular plane is parallel to the substrate. Density functional theory calculation confirms the flat-lying adsorption mode and shows that the tetracene molecule prefers to be adsorbed on the long bridge site with its long axis in the [1(1)over bar 0] azimuth.
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Study of the initial adsorption state of tetracene on Ru( 10(1)over-bar0)
2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the Ru( 10 (1) over bar0) surface has been investigated by ultraviolet photoemission spectroscopy ( UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the Ru( 10 (1) over bar0) surface up to 150 degrees C.
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Study of the initial adsorption state of tetracene on [Formula: see text].
Journal of physics. Condensed matter : an Institute of Physics journal, 2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the [Formula: see text] surface has been investigated by ultraviolet photoemission spectroscopy (UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the [Formula: see text] surface up to 150 °C.
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Study of the initial adsorption state of tetracene on Ru(1010)
Journal of Physics: Condensed Matter, 2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the Ru(1010) surface has been investigated by ultraviolet photoemission spectroscopy (UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the Ru(1010) surface up to 150°C.
Christopher J. Bardeen - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and photophysical properties of a "face-to-face" stacked tetracene dimer.
Physical chemistry chemical physics : PCCP, 2015Co-Authors: Heyuan Liu, Li Shen, Yuhan Chen, Valerie M. Nichols, Setarah Jahansouz, Kerry M. Hanson, Christopher J. BardeenAbstract:A covalently linked tetracene dimer has been prepared and its molecular structure is characterized by (1)H NMR and MALDI-TOF mass spectroscopy, and elemental analysis. The minimized molecular structure reveals that the tetracene subunits in a dimer adopt a "face-to-face" stacked configuration. Its absorption spectrum differs significantly from that of the monomeric counterpart in solution, suggesting the presence of strong interactions between the two tetracene subunits. In solution, the fluorescence spectrum is dominated by a band at around 535 nm, due to an oxidative impurity. In the longer wavelength range, a short-lived lower energy emission can be identified as the intrinsic emission of the dimer. In a polystyrene matrix or at low temperatures, the lifetime of the lower energy emission lengthens and it becomes more prominent. We suggest that the interactions between the two tetracene subunits produce a short-lived, lower energy "excimer-like" state. The fluorescence decays show no observable dependence on an applied magnetic field, and no obvious evidence of significant singlet fission is found in this dimer. This research suggests that even though there are strong electronic interactions between the tetracene subunits in the dimer, singlet fission cannot be achieved efficiently, probably because the formation of "excimer-like" states competes effectively with singlet fission.
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The Dynamics of Singlet Fission in Crystalline Tetracene and Covalent Analogs
Accounts of chemical research, 2013Co-Authors: Jonathan James Burdett, Christopher J. BardeenAbstract:Singlet fission (SF) is a spin-allowed process in which an excited singlet state spontaneously splits into a pair of triplet excitons. This relaxation pathway is of interest as a mechanism for increasing the efficiency of photovoltaic solar cells, since ionization of the triplets could produce two charge carriers per absorbed photon. In this Account, we summarize our recent work on trying to understand how SF occurs using both covalent and noncovalent assemblies of tetracene. We first give a brief overview of the SF process and discuss why tetracene, where the singlet and triplet pair energies are nearly degenerate, is a particularly useful molecule for studying this process. Then we describe our experiments, beginning with the study of phenylene-linked tetracene dimers as covalent analogs for the crystal form, where SF is known to be very efficient. We found that only 2–3% of the initially excited singlets underwent SF in these dimers. These results motivated us to study crystalline tetracene in more det...
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Exciton delocalization and superradiance in tetracene thin films and nanoaggregates.
Physical review letters, 2004Co-Authors: Sang-hyun Lim, Thomas G. Bjorklund, Frank C. Spano, Christopher J. BardeenAbstract:The structure and dynamics of luminescent excitons in tetracene thin films and nanoaggregates are investigated using time-resolved spectroscopy and theoretical calculations. The orientation of tetracene's transition dipole moment along its short molecular axis leads to properties qualitatively different from those observed in aggregates of phenylene-vinylene and thiophene oligomers, despite similar crystal structures. The spectral shape, temperature dependence, and radiative lifetime are consistent with a short-lived superradiant exciton delocalized over approximately 10 tetracene molecules.
Qiao Chen - One of the best experts on this subject based on the ideXlab platform.
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Study on the interaction between tetracene and Cu(110) surface.
The Journal of chemical physics, 2007Co-Authors: Weidong Dou, Shining Bao, Hanjie Zhang, Han Huang, Fei Song, Dandan Guan, Qiao ChenAbstract:The electronic structure of tetracene on Cu (110) surface has been studied by using ultraviolet photoemission spectroscopy (UPS). The emission features from the organic molecule are located from 1 to 10 eV below the Fermi level, and they shift in binding energy with increasing the coverage of the organic material. For the surface with multilayer of tetracene, six well-resolved features were found at 1.90, 3.40, 4.70, 5.95, 6.95, and 9.15 eV below the Fermi level, respectively. On the surface with a lower coverage of tetracene, angle-resolved UPS measurements suggest that the molecular plane is parallel to the substrate. Density functional theory calculation confirms the flat-lying adsorption mode and shows that the tetracene molecule prefers to be adsorbed on the long bridge site with its long axis in the [1(1)over bar 0] azimuth.
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Study of the initial adsorption state of tetracene on Ru( 10(1)over-bar0)
2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the Ru( 10 (1) over bar0) surface has been investigated by ultraviolet photoemission spectroscopy ( UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the Ru( 10 (1) over bar0) surface up to 150 degrees C.
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Study of the initial adsorption state of tetracene on [Formula: see text].
Journal of physics. Condensed matter : an Institute of Physics journal, 2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the [Formula: see text] surface has been investigated by ultraviolet photoemission spectroscopy (UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the [Formula: see text] surface up to 150 °C.
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Study of the initial adsorption state of tetracene on Ru(1010)
Journal of Physics: Condensed Matter, 2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the Ru(1010) surface has been investigated by ultraviolet photoemission spectroscopy (UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the Ru(1010) surface up to 150°C.
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Studies of growth behavior of tetracene on Ru(101¯0) at submonolayer coverage
Surface Science, 2006Co-Authors: H.j. Zhang, Bin Song, Qiao Chen, Shining BaoAbstract:Abstract The growth behavior and the adsorption geometries of tetracene on the Ru ( 1 0 1 ¯ 0 ) surface in the submonolayer regime were investigated by scanning tunneling microscopy (STM) and density-functional theory (DFT) calculations. Tetracene molecules are in the flat-lying geometry on Ru ( 1 0 1 ¯ 0 ) , and orientated with their long axes mainly along the [ 1 2 ¯ 1 0 ] and [0 0 0 1] directions. Tetracene form neither islands, nor ordered structure at submonolayer coverages, and for the tetracene overlayer near to a monolayer, a parquet-like pattern evolves. The DFT calculations showed an adsorption energy of 4.23 eV for tetracene adsorbed between the top and the second Ru atoms rows with its long molecular axis along the [ 1 2 ¯ 1 0 ] direction, and a slightly smaller adsorption energy of 4.19 eV for tetracene adsorbed with its long axis perpendicular to [ 1 2 ¯ 1 0 ] , consisting qualitatively with the orientational distributions observed by STM. The results indicate that growth of tetracene on Ru ( 1 0 1 ¯ 0 ) is mainly controlled by the adsorbate-substrate interactions, and the laterally intermolecular interaction has little influence on the growth.
Samuel W Thomas - One of the best experts on this subject based on the ideXlab platform.
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two dimensional acene containing conjugated polymers that show ratiometric fluorescent response to singlet oxygen
Macromolecules, 2015Co-Authors: Esra Altinok, Zachary Smith, Samuel W ThomasAbstract:This paper describes two-dimensional conjugated poly(phenylene–ethynylene)s (PPEs) linked to singlet oxygen-reactive diethynyltetracene units through phenylene–ethynylene (PE) bridges that are conjugated to the polymer backbones. Successive Sonogashira coupling reactions enabled the preparation of the tetracene-containing PE pendants, the linking of the pendants to the monomer unit, and the polymerization reactions. Small molecule models of the polymers showed ratiometric responses of fluorescence upon exposure to photogenerated singlet oxygen due to cycloaddition reactions increasing the excited state of individual chromophores. The fluorescent responses of the tetracene-linked PPEs, however, showed markedly different behavior: (i) an initial increase in fluorescence intensity and fluorescence lifetime of the side-chain Tetracenes upon exposure to 1O2 indicated an analyte-induced slowing of self-quenching due to high local acene concentration, and (ii) ratiometric blue-shifted response did not occur unti...
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Two-Dimensional, Acene-Containing Conjugated Polymers That Show Ratiometric Fluorescent Response to Singlet Oxygen
2015Co-Authors: Esra Altinok, Zachary C. Smith, Samuel W ThomasAbstract:This paper describes two-dimensional conjugated poly(phenylene–ethynylene)s (PPEs) linked to singlet oxygen-reactive diethynyltetracene units through phenylene–ethynylene (PE) bridges that are conjugated to the polymer backbones. Successive Sonogashira coupling reactions enabled the preparation of the tetracene-containing PE pendants, the linking of the pendants to the monomer unit, and the polymerization reactions. Small molecule models of the polymers showed ratiometric responses of fluorescence upon exposure to photogenerated singlet oxygen due to cycloaddition reactions increasing the excited state of individual chromophores. The fluorescent responses of the tetracene-linked PPEs, however, showed markedly different behavior: (i) an initial increase in fluorescence intensity and fluorescence lifetime of the side-chain Tetracenes upon exposure to 1O2 indicated an analyte-induced slowing of self-quenching due to high local acene concentration, and (ii) ratiometric blue-shifted response did not occur until approximately 75% of pendant acenes were oxidized, highlighting the potential utility of analyte-induced removal of traps in light-harvesting fluorescent materials
Hanjie Zhang - One of the best experts on this subject based on the ideXlab platform.
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Electronic properties and adsorption structures of tetracene on the Ag(110) surface
Surface Science, 2015Co-Authors: Yongsheng Tao, Hongying Mao, Hanjie ZhangAbstract:Abstract The adsorption of tetracene on Ag(110) surface has been studied using ultraviolet photoemission spectroscopy (UPS) and first-principles density function theory (DFT) calculation. The five emission features originating from the organic molecules locate at 3.4, 5.7, 6.3, 7.2, and 8.8 eV below the Fermi level, respectively. There is no apparent binding energy shift of these features with the increasing coverage of tetracene, indicating a relatively weak interaction between tetracene and the Ag(110) substrate. Moreover, our DFT calculation shows that tetracene molecules prefer to adsorb between two Ag atomic rows of the first layer with its molecular axis along the [001] direction of the substrate, and the center of its second benzene ring locates at top site of Ag atoms of the second layer. With this optimized adsorption configuration, the π–d interactions between tetracene and Ag(110) are maximized. Comparing with the densities of states (DOS) before and after tetracene adsorption, no apparent intensity change can be observed for the DOS from p-orbital of tetracene, suggesting that the coupling between the substrate d-band and the filled p-orbitals of tetracene are relatively weak.
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The chemisorption of tetracene on Si(100)-2×1 surface
The Journal of chemical physics, 2009Co-Authors: Hongying Mao, Hanjie Zhang, Fei Song, Weidong Dou, Dandan Guan, Meiliang Chen, Shining BaoAbstract:The adsorption of tetracene on Si(100)-2×1 substrate has been studied by ultraviolet photoemission spectroscopy (UPS). Six features deriving from the organic material are located at 1.22, 2.41, 3.63, 4.67, 7.11, and 8.77 eV below the Fermi level. These features shift in binding energy with increasing the thickness of the organic film. In the case of a monolayer, angle-resolved UPS measurements suggest that the molecular plane is parallel to the substrate. Further theoretical density functional theory calculation reveals the most stable structure of tetracene molecule on Si substrate in which six covalent Si–C chemical bonds are formed between carbon atoms of the tetracene molecule and the Si atoms on the substrate.
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Study on the interaction between tetracene and Cu(110) surface.
The Journal of chemical physics, 2007Co-Authors: Weidong Dou, Shining Bao, Hanjie Zhang, Han Huang, Fei Song, Dandan Guan, Qiao ChenAbstract:The electronic structure of tetracene on Cu (110) surface has been studied by using ultraviolet photoemission spectroscopy (UPS). The emission features from the organic molecule are located from 1 to 10 eV below the Fermi level, and they shift in binding energy with increasing the coverage of the organic material. For the surface with multilayer of tetracene, six well-resolved features were found at 1.90, 3.40, 4.70, 5.95, 6.95, and 9.15 eV below the Fermi level, respectively. On the surface with a lower coverage of tetracene, angle-resolved UPS measurements suggest that the molecular plane is parallel to the substrate. Density functional theory calculation confirms the flat-lying adsorption mode and shows that the tetracene molecule prefers to be adsorbed on the long bridge site with its long axis in the [1(1)over bar 0] azimuth.
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Study of the initial adsorption state of tetracene on Ru( 10(1)over-bar0)
2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the Ru( 10 (1) over bar0) surface has been investigated by ultraviolet photoemission spectroscopy ( UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the Ru( 10 (1) over bar0) surface up to 150 degrees C.
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Study of the initial adsorption state of tetracene on [Formula: see text].
Journal of physics. Condensed matter : an Institute of Physics journal, 2007Co-Authors: Han Huang, Shining Bao, Hanjie Zhang, Qiao Chen, Fei Song, Weidong Dou, Wuzong ZhouAbstract:Tetracene on the [Formula: see text] surface has been investigated by ultraviolet photoemission spectroscopy (UPS). The UPS results show features, from tetracene, between 2.0 and 10.0 eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an ab initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the [Formula: see text] surface up to 150 °C.