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Shu Seki - One of the best experts on this subject based on the ideXlab platform.
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Confinement of Single Polysilane Chains in Coordination Nanospaces
Journal of the American Chemical Society, 2015Co-Authors: Takashi Kitao, Shu Seki, Silvia Bracco, Angiolina Comotti, Piero Sozzani, Masanobu Naito, Takashi Uemura, Susumu KitagawaAbstract:Understanding the intrinsic properties of single conducting polymer chains is of interest, largely for their applications in molecular devices. In this study, we report the accommodation of single Polysilane chains with hole-transporting ability in porous coordination polymers (PCPs), [Al(OH)(L)]n (1a; L = 2,6-naphthalenedicarboxylate, channel size = 8.5 × 8.5 A2, 1b; L = 4,4′-biphenyldicarboxylate, channel size = 11.1 × 11.1 A2). Interestingly, the isolation of single Polysilane chains increased the values of carrier mobility in comparison with that in the bulk state due to the elimination of the slow interchain hole hopping. Moreover, even when the chains are isolated one another, the main chain conformation of Polysilane could be controlled by changing the pore environment of PCPs, as evidenced by Raman spectroscopy, solid-state NMR measurements, and molecular dynamics simulation. Hence, we succeeded in varying the conducting property of single Polysilane chains. Additionally, Polysilanes have a drawba...
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Confinement of Single Polysilane Chains in Coordination Nanospaces
2015Co-Authors: Takashi Kitao, Shu Seki, Silvia Bracco, Angiolina Comotti, Piero Sozzani, Masanobu Naito, Takashi Uemura, Susumu KitagawaAbstract:Understanding the intrinsic properties of single conducting polymer chains is of interest, largely for their applications in molecular devices. In this study, we report the accommodation of single Polysilane chains with hole-transporting ability in porous coordination polymers (PCPs), [Al(OH)(L)]n (1a; L = 2,6-naphthalenedicarboxylate, channel size = 8.5 × 8.5 Å2, 1b; L = 4,4′-biphenyldicarboxylate, channel size = 11.1 × 11.1 Å2). Interestingly, the isolation of single Polysilane chains increased the values of carrier mobility in comparison with that in the bulk state due to the elimination of the slow interchain hole hopping. Moreover, even when the chains are isolated one another, the main chain conformation of Polysilane could be controlled by changing the pore environment of PCPs, as evidenced by Raman spectroscopy, solid-state NMR measurements, and molecular dynamics simulation. Hence, we succeeded in varying the conducting property of single Polysilane chains. Additionally, Polysilanes have a drawback, photodegradation under ultraviolet light, which should be overcome for the application of Polysilanes. It is noteworthy that the accommodation of Polysilane in the nanopores did not exhibit photodegradation. These results highlight that PCP–Polysilane hybrids are promising candidates for further use in the field of molecular electronics
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evidence of electron conductivity in Polysilanes and its implications in design of ultraviolet emitting devices
Journal of Applied Physics, 2010Co-Authors: Niladri Banerjee, Shu SekiAbstract:Polysilanes are thought to be primarily hole conducting. Consequently, poor efficiency of a Polysilane based light emitting diode is explained on the basis of propensity of the charge carriers to nonradiatively recombine near the cathode. We fabricated a single layer device based on poly(n-octylphenylsilane) with a calcium cathode. This device, however, cannot be analyzed on the basis of a single carrier (hole) transport and the device, unexpectedly, exhibits an injection limited current, though no barrier to hole injection exists. Simulation based analysis reveals bipolar transport, with electron mobility much greater than the hole mobility. This now also makes Polysilane electron transport layers possible. In addition, we establish that the time-of-flight measured mobilities in Polysilanes may not be relevant to electronic devices, which employ much thinner layers. Based on these observations, the basis for device design is revised. Accordingly, a N, N-diphenyl-N, N-bis(1-naphthyl)(1,1-biphenyl)-4,4 dia...
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study of transport properties in fullerene doped Polysilane films using flash photolysis time resolved microwave technique
Chemical Physics Letters, 2005Co-Authors: Anjali Acharya, Shu Seki, Akinori Saeki, Yoshiko Koizumi, Seiichi TagawaAbstract:Abstract The charge carrier photo generation in fullerene (C60) doped Polysilane (PS) is a multistage process including, photo induced electron transfer between Polysilane to 3 C 60 ∗ and relaxation of the charge-transfer state which results in polaron pair (PS + and C 60 - ) formation. To study the mobility of charge carriers in Polysilane films (PS1-8) doped with fullerene (C60), the flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements have been performed. Second harmonic generation (SHG), laser of wavelength 532 nm has been used as excitation source. The highest ϕ∑μ value (7 × 10−5 cm2/V s) obtained for PS6 among all Polysilanes due to its highly ordered structure. The photo carrier generation efficiency of Polysilane films have increased due to fullerene doping. The fast decay kinetics of TRMC signal is due to backward electron transfer between PS + and C 60 - where as slow decay can be attributed to charge recombination after diffusion process.
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Dynamics of positive charge carriers on Si chains of Polysilanes.
Journal of the American Chemical Society, 2004Co-Authors: Shu Seki, Tomoyo Kawaguchi, Yoshiko Koizumi, Hidefumi Habara, Seiichi TagawaAbstract:The transient absorption of radical cations of a variety of substituted Polysilanes is discussed quantitatively in terms of the molar extinction coefficient and oscillator strength by nanosecond pulse radiolysis. Oxygen-saturated Polysilane solutions in benzene exhibit a strong transient absorption band ascribed to the Polysilane radical cation. The transient species react with N,N,N',N'-tetramethyl-p-phenylene-diamine (TMPD) to produce TMPD radical cations. On the basis of the molar extinction coefficient of the TMPD radical cation, the molar extinction coefficients for the radical cations of Polysilanes are found to increase in the range 3.3 x 10(4) to 2.0 x 10(5) M(-)(1) cm(-)(1) with increasing polymer segment length. The stepwise increase in the total oscillator strength with an increase in the number of phenyl rings directly bonded to the Si skeleton suggests the delocalization of the positive polaron state and/or the SOMO state over the phenyl rings, indicating the importance of phenyl rings in intermolecular hole transfer processes.
Seiichi Tagawa - One of the best experts on this subject based on the ideXlab platform.
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study of transport properties in fullerene doped Polysilane films using flash photolysis time resolved microwave technique
Chemical Physics Letters, 2005Co-Authors: Anjali Acharya, Shu Seki, Akinori Saeki, Yoshiko Koizumi, Seiichi TagawaAbstract:Abstract The charge carrier photo generation in fullerene (C60) doped Polysilane (PS) is a multistage process including, photo induced electron transfer between Polysilane to 3 C 60 ∗ and relaxation of the charge-transfer state which results in polaron pair (PS + and C 60 - ) formation. To study the mobility of charge carriers in Polysilane films (PS1-8) doped with fullerene (C60), the flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements have been performed. Second harmonic generation (SHG), laser of wavelength 532 nm has been used as excitation source. The highest ϕ∑μ value (7 × 10−5 cm2/V s) obtained for PS6 among all Polysilanes due to its highly ordered structure. The photo carrier generation efficiency of Polysilane films have increased due to fullerene doping. The fast decay kinetics of TRMC signal is due to backward electron transfer between PS + and C 60 - where as slow decay can be attributed to charge recombination after diffusion process.
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Dynamics of positive charge carriers on Si chains of Polysilanes.
Journal of the American Chemical Society, 2004Co-Authors: Shu Seki, Tomoyo Kawaguchi, Yoshiko Koizumi, Hidefumi Habara, Seiichi TagawaAbstract:The transient absorption of radical cations of a variety of substituted Polysilanes is discussed quantitatively in terms of the molar extinction coefficient and oscillator strength by nanosecond pulse radiolysis. Oxygen-saturated Polysilane solutions in benzene exhibit a strong transient absorption band ascribed to the Polysilane radical cation. The transient species react with N,N,N',N'-tetramethyl-p-phenylene-diamine (TMPD) to produce TMPD radical cations. On the basis of the molar extinction coefficient of the TMPD radical cation, the molar extinction coefficients for the radical cations of Polysilanes are found to increase in the range 3.3 x 10(4) to 2.0 x 10(5) M(-)(1) cm(-)(1) with increasing polymer segment length. The stepwise increase in the total oscillator strength with an increase in the number of phenyl rings directly bonded to the Si skeleton suggests the delocalization of the positive polaron state and/or the SOMO state over the phenyl rings, indicating the importance of phenyl rings in intermolecular hole transfer processes.
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dynamics of positive charge carriers on si chains of Polysilanes
Journal of the American Chemical Society, 2004Co-Authors: Shu Seki, Tomoyo Kawaguchi, Yoshiko Koizumi, Hidefumi Habara, Seiichi TagawaAbstract:The transient absorption of radical cations of a variety of substituted Polysilanes is discussed quantitatively in terms of the molar extinction coefficient and oscillator strength by nanosecond pulse radiolysis. Oxygen-saturated Polysilane solutions in benzene exhibit a strong transient absorption band ascribed to the Polysilane radical cation. The transient species react with N,N,N‘,N‘-tetramethyl-p-phenylene-diamine (TMPD) to produce TMPD radical cations. On the basis of the molar extinction coefficient of the TMPD radical cation, the molar extinction coefficients for the radical cations of Polysilanes are found to increase in the range 3.3 × 104 to 2.0 × 105 M-1 cm-1 with increasing polymer segment length. The stepwise increase in the total oscillator strength with an increase in the number of phenyl rings directly bonded to the Si skeleton suggests the delocalization of the positive polaron state and/or the SOMO state over the phenyl rings, indicating the importance of phenyl rings in intermolecular ...
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Pulse radiolysis study of radical cations of Polysilanes
Chemical Physics Letters, 2003Co-Authors: Tomoyo Kawaguchi, Shu Seki, Kazumasa Okamoto, Akinori Saeki, Yoichi Yoshida, Seiichi TagawaAbstract:Abstract Molar extinction coefficients of radical cations are quantitatively discussed for a variety of substituted Polysilanes by nano-second pulse radiolysis. Polysilane solution in benzene under saturated oxygen exhibits a strong absorption band ascribed to Polysilane radical cation in the transient spectra. The transient species react with N,N,N′,N′-tetramethyl-p-phenylene-diamine (TMPD) to produce TMPD radical cations. Using the molar extinction coefficient of TMPD radical cation, the molar extinction coefficients for the radical cations of Polysilanes are found to increase in the range 3.8 × 104–15.0 × 104 M−1 cm−1 with an increase in the segment length of the polymers. This is the first report on the extinction coefficient and oscillator strength of Polysilane radical cations.
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Negative Resist Material Based on Polysilanes for Electron Beam and X-Ray Lithographies
Japanese Journal of Applied Physics, 2000Co-Authors: Shu Seki, Yusuke Sakurai, Kensaku Maeda, Yoshihisa Kunimi, Seiichi TagawaAbstract:In the present paper, we describe the mechanisms of photo- and radiation-induced reactions in silicon based resist materials, Polysilanes with Si-branchings and Si–H bondings, candidates for future resist materials. Polysilanes have been previously confirmed to show positive-type resist properties for ultra violet (UV) light, electron beams (EB), and X-rays under all conditions. However, the cross-linking reaction of the polymer became dominant in the Polysilane with Si-branchings, upon irradiation with UV light, EB, and ion beams. The efficiency of the cross-linking reaction strongly depended on the ratio of Si-branching producing polymer gels in the Polysilane with a higher amount of Si-branching than 5%, even with γ-ray irradiation. Polyhydrosilanes containing vinyl groups were revealed to cause efficient cross-linking reactions in the presence of catalysts for hydrosilylation upon exposure to deep UV or X-rays, leading to high-sensitive negative resist materials for extreme UV lithography.
Shinya Mimura - One of the best experts on this subject based on the ideXlab platform.
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optical properties of organic inorganic hybrid thin films containing Polysilane segments prepared from Polysilane methacrylate copolymers
Journal of Organometallic Chemistry, 2000Co-Authors: Shinya Mimura, Hiroyoshi Naito, Yoshihiko Kanemitsu, Kimihiro Matsukawa, Hiroshi InoueAbstract:Abstract Optical properties of Polysilane–silica hybrid thin films have been studied to examine confinement effects of Polysilane segments in silica matrices. Polysilane–methacryloxypropyltrimethoxysilane copolymers are synthesized from photo-radical copolymerization of 3-methacryloxypropyltrimethoxysilane and using polymethylphenylsilane. Organic–inorganic hybrid thin films with homogeneously dispersed Polysilane segments are successfully prepared from the copolymers by a sol–gel method. It is found that UV light-induced degradation of photoluminescence of the Polysilane–silica hybrid thin films is suppressed in comparison with that of polymethylphenylsilane at 10 K, and that UV light exposure decreases the refractive index of the Polysilane–silica hybrid thin film from 1.60 to 1.40 at room temperature. It is also found that the degree of the anisotropy of the linearly polarized photoluminescence approaches to the theoretical upper limit with decreasing Polysilane content in the Polysilane–silica hybrid thin films. These results indicate that the fabrication of Polysilane–silica hybrid thin film is a new approach for future Polysilane based opto-electronic devices.
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Optical properties of organic–inorganic hybrid thin films containing Polysilane segments prepared from Polysilane–methacrylate copolymers
Journal of Organometallic Chemistry, 2000Co-Authors: Shinya Mimura, Hiroyoshi Naito, Yoshihiko Kanemitsu, Kimihiro Matsukawa, Hiroshi InoueAbstract:Abstract Optical properties of Polysilane–silica hybrid thin films have been studied to examine confinement effects of Polysilane segments in silica matrices. Polysilane–methacryloxypropyltrimethoxysilane copolymers are synthesized from photo-radical copolymerization of 3-methacryloxypropyltrimethoxysilane and using polymethylphenylsilane. Organic–inorganic hybrid thin films with homogeneously dispersed Polysilane segments are successfully prepared from the copolymers by a sol–gel method. It is found that UV light-induced degradation of photoluminescence of the Polysilane–silica hybrid thin films is suppressed in comparison with that of polymethylphenylsilane at 10 K, and that UV light exposure decreases the refractive index of the Polysilane–silica hybrid thin film from 1.60 to 1.40 at room temperature. It is also found that the degree of the anisotropy of the linearly polarized photoluminescence approaches to the theoretical upper limit with decreasing Polysilane content in the Polysilane–silica hybrid thin films. These results indicate that the fabrication of Polysilane–silica hybrid thin film is a new approach for future Polysilane based opto-electronic devices.
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Optical properties of (organic Polysilane)–(inorganic matrix) hybrid thin films
Journal of Luminescence, 2000Co-Authors: Shinya Mimura, Hiroyoshi Naito, Yoshihiko Kanemitsu, Kimihiro Matsukawa, H InoueAbstract:Abstract Polysilane–inorganic hybrid thin films – organic Polysilane embedded in a silica matrix – were fabricated using a sol–gel method to improve the durability of organic Polysilanes as optoelectric devices. Photoluminescence measurements at 10 K show that the durability against ultraviolet light exposure is improved in the Polysilane–inorganic hybrid thin films. In addition, the luminescence linear polarization memory is found at 10 K, suggesting the decrease in the interchain interaction of Polysilanes in the Polysilane–inorganic hybrid thin films.
Robert West - One of the best experts on this subject based on the ideXlab platform.
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Patai's Chemistry of Functional Groups - Polysilanes: Conformations, Chromotropism and Conductivity
PATAI'S Chemistry of Functional Groups, 2009Co-Authors: Robert WestAbstract:1 Introduction 2 Conformations and Electronic Structure 3 Chromotropism 4 Electrical Conductivity 5 Acknowledgements Keywords: Polysilanes - conformations, chromotropism and conductivity; conformations and electronic structure; Polysilane thermochromism in solution; Polysilane thermochromism as solids; solvatochromism; ionochromism; other chromotropic behavior; pristine Polysilanes and electrical conductivity
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Polysilanes conformations chromotropism and conductivity
Patai's Chemistry of Functional Groups, 2009Co-Authors: Robert WestAbstract:1 Introduction 2 Conformations and Electronic Structure 3 Chromotropism 4 Electrical Conductivity 5 Acknowledgements Keywords: Polysilanes - conformations, chromotropism and conductivity; conformations and electronic structure; Polysilane thermochromism in solution; Polysilane thermochromism as solids; solvatochromism; ionochromism; other chromotropic behavior; pristine Polysilanes and electrical conductivity
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Inorganic Polymers - Polysilanes and Related Polymers
Inorganic Polymers, 2005Co-Authors: James E. Mark, Harry R. Allcock, Robert WestAbstract:In Polysilane polymers, the polymer backbone is made up entirely of silicon atoms. Therefore these materials differ from other important inorganic polymers, the siloxanes and phosphazenes, in which the polymer chain is heteroatomic. Structurally, they are more closely related to homoatomic organic polymers such as the polyolefins. However, because the units in the main chain are all silicon atoms, the Polysilanes exhibit quite unusual properties. The cumulated silicon-silicon bonds in the polymer chain allow extensive electron delocalization to take place, and this delocalization of the sigma electrons in the Si-Si bonds gives the Polysilanes unique optical and electronic properties. Many of the potential technical uses, as well as the remarkable properties, of Polysilanes result from this unusual mobility of the sigma electrons. The Polysilanes can be regarded as one-dimensional analogs to elemental silicon, on which, of course, nearly all of modern electronics is based. The photophysical behavior of Polysilanes is not approached by any other materials, save for the less stable and more costly polygermanes and polystannanes. The remarkable properties of Polysilanes have led to intense interest, and to numerous proposed high-tech applications. But the great promise of Polysilanes as materials has yet to be realized. Their only commercial use at present is as precursors to silicon carbide ceramics, an application which takes no advantage of their optical or electronic properties. Linear Polysilane polymers, properly called poly(silylene)s, can be obtained as homopolymers or copolymers. Continuation of the Polysilane chain consumes two of the four valences of each silicon atom; the other two are taken up by pendent groups, which may be the same or different. Copolymers, which contain two or more kinds of silicon atoms, can be made up from units. A typical example is the copolymer of Me2Si and PhMeSi units, poly(dimethylsilylene-co-phenylmethylsilylene), which bears the popular name “polysilastyrene.” The pendent groups are typically organic units and can include alkyl, aryl, substituted aryl, hydrogen, Me3Si, ferrocenyl, and so on. An unlimited number of different polymers are possible, and several hundred compositions have been described in the literature.
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Mass Spectroscopy Study on Pyrolysis of Polysilanes.
Journal of Photopolymer Science and Technology, 1998Co-Authors: Lujun Pan, Robert West, Mei Zhang, Kunio Oka, Mikio Aramata, Yoshikazu NakayamaAbstract:Pyrolysis of Polysilanes with different molecular weights, solid states and substituents has been studied by quadrupole mass spectroscopy. The analysis of kinetics on the gas evolution spectra of a unit of the Polysilanes gives their activation energies having Gaussian distributions. The number reduction of the weak Si-Si bonds with the decrease of the chain length of Polysilanes results in the increase of activation energy of decomposition. The activation energy is also affected by the kind of solid states of Polysilane. Because of the stronger interaction among the molecules, Polysilane film has higher activation energies than powder. Due to the photodegradation and oxidation of Polysilanes, photooxidized film has higher activation energies of decomposition and a broader distribution of activation energies than the unoxidized film. Furthermore, substituents give intense effects on the activation energies and the order of the decomposition reactions. It is found that the decomposition reactions occur at the low temperature if the substituents are easy to be disconnected from Si.
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preparation of oriented langmuir blodgett films of Polysilanes bearing hydroxyalkyl or alkoxyalkyl groups
Macromolecules, 1994Co-Authors: Rikako Kani, Chien-hua Yuan, Shuzi Hayase, Yoshihiko Nakano, Yutaka Majima, Robert WestAbstract:Polysilane polymers bearing hydroxyalkyl or alkoxyalkyl groups form monolayers (L films) at an air-water interface. It is possible to transfer all of the L films to hydrophobic substituents to provide Langmuir-Blodgett films. Among these polymers, Polysilanes having more than three alkyl carbons have provided, oriented Polysilane thin films in which the silicon main chains align with each other in the direction parallel to the dipping direction of the substrates. The orientations were evaluated by their polarized UV absorptions
H Inoue - One of the best experts on this subject based on the ideXlab platform.
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Optical properties of (organic Polysilane)–(inorganic matrix) hybrid thin films
Journal of Luminescence, 2000Co-Authors: Shinya Mimura, Hiroyoshi Naito, Yoshihiko Kanemitsu, Kimihiro Matsukawa, H InoueAbstract:Abstract Polysilane–inorganic hybrid thin films – organic Polysilane embedded in a silica matrix – were fabricated using a sol–gel method to improve the durability of organic Polysilanes as optoelectric devices. Photoluminescence measurements at 10 K show that the durability against ultraviolet light exposure is improved in the Polysilane–inorganic hybrid thin films. In addition, the luminescence linear polarization memory is found at 10 K, suggesting the decrease in the interchain interaction of Polysilanes in the Polysilane–inorganic hybrid thin films.
