CdS半导体与吩噻嗪树枝有机材料的超快动力学过程
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摘要
在光学和光电子技术高速发展的当今时代,非线性光学材料是一类具有重要应用前景的新材料。其中,具有双光子吸收特性的材料在荧光显微成像、频率上转换激光器、光限幅和三维光存储等领域的巨大应用前景使其备受关注。而飞秒激光器的广泛应用和飞秒光谱学的日臻完善使人们对新型材料中的超快动力学过程的探测成为可能。由于这些超快过程包含着分子结构以及光与物质相互作用等丰富而重要的信息,对它们的深入研究为合成和优化新型材料,探索新颖器件及其应用提供坚实而可靠的基础。因此,应用飞秒激光来研究材料的非线性光学性质和超快动力学过程就成为近年来光学领域的前沿课题之一。
本文应用飞秒激光技术研究了CdS半导体晶体和吩噻嗪有机分子的超快动力学过程。对不同的超快过程,采用相对应的研究方法。研究了CdS晶体的非线性光学性质和载流子弛豫过程。通过对CdS晶体的飞秒克尔效应测试,观察到了大约1ps的超快时间响应,计算非共振三阶非线性光学极化率为7.9×10~(-12)esu,分析非线性的来源主要是局域场效应和电子结构失谐。利用飞秒脉冲泵浦—探测技术研究了CdS晶体载流子的超快动力学特性,测量了CdS样品的瞬态吸收随延迟时间的变化,观察发现超快弛豫曲线由载流子初始散射、载流子—晶格热平衡和载流子回复三个部分组成,对应的时间分别是500fs、2ps和10ps。结果表明:这类材料具有较大的光学非线性和快速的相应时间,有望在高速光开关等方面有潜在的应用前景。
利用飞秒脉冲抽运—探测技术研究了一代与二代吩噻嗪树枝分子的超快动力学特性。吩噻嗪是一类含有富电子的氮和硫原子的芳香杂环化合物,将吩噻嗪作为EL材料的研究直到最近几年才开始,但已获得了很大的进展。吩噻嗪及其衍生物是一种含有氮和硫两个杂原子的富电子芳香杂环化合物,具有很好的空穴传输能力,也具有较低的电离势,因此吩噻嗪被认为是一种非常好的能够有效降低有机半导体材料离子化电势(ionicpotential)的结构基元。本论文测量了样品的瞬态吸收率随延迟时间的变化曲线,观察发现超快弛豫曲线由分子到达激发态和通过分子间碰撞失去能量回到基态两部分组成。对应的时间分别是1ps、6ps(一代)、5ps(二代)。结果表明:通过对比特征时间,分析得到分子的内转换过程与外树枝结构相关。
Along with the great developments of the optical science and optical electronics in recent decades,the materials with excellent nonlinear optical properties have currently attracted considerable attention and show a variety of potential applications. Among the various classes of nonlinear optical materials,two-photon absorbing materials have been the subject of growing interest because of their potential application in many field,including two-photon fluorescence imaging,two-photon up-conversion laser,optical limiting and,three-dimensional data storage.With the wide utilization of the femtosecond laser system and the great achievement in the field of the ultrafast spectroscopy,ultrafast processes of the novel material can now be investigated in the picosecond and femtosecond domains.Because the ultrafast processes can reflect a lot of significant information about the interaction between light and matter,the research results of these processes are meaningful for the synthesizing and optimizing the new materials,as well as exploring the novel devices. Therefore,the study of nonlinear optical properties and ultrafast dynamics of the materials with intense two-photon absorption becomes one of the frontier and hot topics in the optical science.
In this work,the ultrafast dynamics in CdS semiconductor crystal and phenothiazine organic molecule were studied using femtosecond laser technique. Different experimental methods were used to investigate different ultrafast processes. By using optical Kerr technique we got the ultrafast nonlinear optical property curve. Theχ~((3)) of CdS crystal was calculated by comparing with standard sample CS_2. We also analyzed the reason,which caused the large nonlinearity of CdS.The purpose of the paper is to study the ultrafast response of optical nonlinearity of semiconductor. By using femtosecond pump-probe technique we studied the ultrafast excited state relaxation of CdS crystal and phenothiazine organic molecule.We also analyzed and explained the reason in order to study the excited state dynamics very and to provide the reliable theoretical and experimental basis for their practical application.The important result in the paper as following:
1.The femtosecond ultrafast measurement system controlled by computer was set up,and it can measure optical Kerr effect,ultrafast pump-probe absorption spectroscopy,ultrafast pump-probe reflectivity spectroscopy.
Through the technology of femtosecond pump-probe transient absorption,we can get the time-resolved spectroscopy of material that excited by laser.The basic theory of pump-probe technology is to get time-resolved by laser delay in space.The laser pulse is divided into pump pulse and probe pulse.The two pulses have a alterable time delay.The stronger pump pulse is able to excite the material leading the character to change,the probe pulse detects the changes coursed by pump pulse.
The technology of optical Kerr effect is one of the method for measuring of material nonlinear optical response.The basic theory is using a strong linearly polarized light as pump pulse to excite the material to produce optical birefringence, and using the other pulse to detect.
2.First,we studied the Kerr effect of CdS semiconductor crystal.There are two purposes.One is to study the third-order nonlinear of CdS,the other is to get the time zero point of femtosecond pump-probe experiment.Through comparing with standard sample CS_2 we obtain theχ~((3)) of CdS crystal.The Kerr response time is about lps. The value ofχ~((3)) is 7.9×10~(12) esu by calculated.It is analyzed that the source of nonlinear coursed of local-field effect.
3.Second,the ultrafast dynamics of CdS is studied by using femtosecond pump-probe method with laser pulse of 800 nm wavelength.The basic characteristics of CdS carrier relaxation contain three phases:a splitting upwards phase,a fast downwards phase and a slow downwards phase.CdS photogenic charge carrier relaxation contains several important aspects:carrier initial scattering,carrier-lattice energy redistributions,carrier recombination and transport.These are based on selective electron excitation on a time scale shorter than that of electron-electron and electron-lattice energy redistributions.The injected energy is subsequently redistributed among the electrons by e-e scattering eventually leading to the establishment of an electron temperature,and transferred to the lattice by electron-phonon interactions.
4.About organic molecule,we studied phenothiazine which is a well known heterocyclic compound with electron-rich nitrogen and sulfur heteroatom.The method of experiment is femtosecond pump-probe technology with laser pulse of 800nm wavelength.The basic characteristics of phenothiazine excited state relaxation contain two phases:a splitting upwards and a slow downwards phase.After the energy transfer to the upper excitation state,the excitation energy experiences an ultrafast relaxation to the next lowest excitation state,and results in the transient population of this state and the thermalization of the temporally localized electron on this state.As a result,it was observed an ultra_fast process of the excited state absorption from the dynamic traces.By comparing with characteristic time,it is analyzed that the internal conversion time is related with branch structure.
本文应用飞秒激光技术研究了CdS半导体晶体和吩噻嗪有机分子的超快动力学过程。对不同的超快过程,采用相对应的研究方法。研究了CdS晶体的非线性光学性质和载流子弛豫过程。通过对CdS晶体的飞秒克尔效应测试,观察到了大约1ps的超快时间响应,计算非共振三阶非线性光学极化率为7.9×10~(-12)esu,分析非线性的来源主要是局域场效应和电子结构失谐。利用飞秒脉冲泵浦—探测技术研究了CdS晶体载流子的超快动力学特性,测量了CdS样品的瞬态吸收随延迟时间的变化,观察发现超快弛豫曲线由载流子初始散射、载流子—晶格热平衡和载流子回复三个部分组成,对应的时间分别是500fs、2ps和10ps。结果表明:这类材料具有较大的光学非线性和快速的相应时间,有望在高速光开关等方面有潜在的应用前景。
利用飞秒脉冲抽运—探测技术研究了一代与二代吩噻嗪树枝分子的超快动力学特性。吩噻嗪是一类含有富电子的氮和硫原子的芳香杂环化合物,将吩噻嗪作为EL材料的研究直到最近几年才开始,但已获得了很大的进展。吩噻嗪及其衍生物是一种含有氮和硫两个杂原子的富电子芳香杂环化合物,具有很好的空穴传输能力,也具有较低的电离势,因此吩噻嗪被认为是一种非常好的能够有效降低有机半导体材料离子化电势(ionicpotential)的结构基元。本论文测量了样品的瞬态吸收率随延迟时间的变化曲线,观察发现超快弛豫曲线由分子到达激发态和通过分子间碰撞失去能量回到基态两部分组成。对应的时间分别是1ps、6ps(一代)、5ps(二代)。结果表明:通过对比特征时间,分析得到分子的内转换过程与外树枝结构相关。
Along with the great developments of the optical science and optical electronics in recent decades,the materials with excellent nonlinear optical properties have currently attracted considerable attention and show a variety of potential applications. Among the various classes of nonlinear optical materials,two-photon absorbing materials have been the subject of growing interest because of their potential application in many field,including two-photon fluorescence imaging,two-photon up-conversion laser,optical limiting and,three-dimensional data storage.With the wide utilization of the femtosecond laser system and the great achievement in the field of the ultrafast spectroscopy,ultrafast processes of the novel material can now be investigated in the picosecond and femtosecond domains.Because the ultrafast processes can reflect a lot of significant information about the interaction between light and matter,the research results of these processes are meaningful for the synthesizing and optimizing the new materials,as well as exploring the novel devices. Therefore,the study of nonlinear optical properties and ultrafast dynamics of the materials with intense two-photon absorption becomes one of the frontier and hot topics in the optical science.
In this work,the ultrafast dynamics in CdS semiconductor crystal and phenothiazine organic molecule were studied using femtosecond laser technique. Different experimental methods were used to investigate different ultrafast processes. By using optical Kerr technique we got the ultrafast nonlinear optical property curve. Theχ~((3)) of CdS crystal was calculated by comparing with standard sample CS_2. We also analyzed the reason,which caused the large nonlinearity of CdS.The purpose of the paper is to study the ultrafast response of optical nonlinearity of semiconductor. By using femtosecond pump-probe technique we studied the ultrafast excited state relaxation of CdS crystal and phenothiazine organic molecule.We also analyzed and explained the reason in order to study the excited state dynamics very and to provide the reliable theoretical and experimental basis for their practical application.The important result in the paper as following:
1.The femtosecond ultrafast measurement system controlled by computer was set up,and it can measure optical Kerr effect,ultrafast pump-probe absorption spectroscopy,ultrafast pump-probe reflectivity spectroscopy.
Through the technology of femtosecond pump-probe transient absorption,we can get the time-resolved spectroscopy of material that excited by laser.The basic theory of pump-probe technology is to get time-resolved by laser delay in space.The laser pulse is divided into pump pulse and probe pulse.The two pulses have a alterable time delay.The stronger pump pulse is able to excite the material leading the character to change,the probe pulse detects the changes coursed by pump pulse.
The technology of optical Kerr effect is one of the method for measuring of material nonlinear optical response.The basic theory is using a strong linearly polarized light as pump pulse to excite the material to produce optical birefringence, and using the other pulse to detect.
2.First,we studied the Kerr effect of CdS semiconductor crystal.There are two purposes.One is to study the third-order nonlinear of CdS,the other is to get the time zero point of femtosecond pump-probe experiment.Through comparing with standard sample CS_2 we obtain theχ~((3)) of CdS crystal.The Kerr response time is about lps. The value ofχ~((3)) is 7.9×10~(12) esu by calculated.It is analyzed that the source of nonlinear coursed of local-field effect.
3.Second,the ultrafast dynamics of CdS is studied by using femtosecond pump-probe method with laser pulse of 800 nm wavelength.The basic characteristics of CdS carrier relaxation contain three phases:a splitting upwards phase,a fast downwards phase and a slow downwards phase.CdS photogenic charge carrier relaxation contains several important aspects:carrier initial scattering,carrier-lattice energy redistributions,carrier recombination and transport.These are based on selective electron excitation on a time scale shorter than that of electron-electron and electron-lattice energy redistributions.The injected energy is subsequently redistributed among the electrons by e-e scattering eventually leading to the establishment of an electron temperature,and transferred to the lattice by electron-phonon interactions.
4.About organic molecule,we studied phenothiazine which is a well known heterocyclic compound with electron-rich nitrogen and sulfur heteroatom.The method of experiment is femtosecond pump-probe technology with laser pulse of 800nm wavelength.The basic characteristics of phenothiazine excited state relaxation contain two phases:a splitting upwards and a slow downwards phase.After the energy transfer to the upper excitation state,the excitation energy experiences an ultrafast relaxation to the next lowest excitation state,and results in the transient population of this state and the thermalization of the temporally localized electron on this state.As a result,it was observed an ultra_fast process of the excited state absorption from the dynamic traces.By comparing with characteristic time,it is analyzed that the internal conversion time is related with branch structure.
引文
[1]Nishiwaki D,Hamanaka Y,Nonogaki Y et al..Hot carrier relaxation dynamics in InGaAs studied by femtosecond pump-probe spectroscopy.Journal of Luminescence,1999,83(84):49-53
[2]Hong Ye,Wicks G W,Fauchet P M.Electron and hole dynamics in GaN.Materials Science and Engineering.2001,82:131-133
[3]Youngdahl C J,Weertman J R,Hugo R C.Deformation Behavior In nanocrystalline copper.Scriptamater,2001,44:1475-1478
[4]马国宏,郭立俊,钱士雄.飞秒物理、飞秒化学和飞秒生物学.物理,2001,6:349-355
[5]Hess C,Funk S,Bonn M.Femtosecond dynamics of chemical reactions at surfaces.Appl.Phys.A,2000,71:477-483
[6]Oudar J L,Hulin D.Migus A et al..Subpicosecond Spectral Hole Burning Due to Nonthermalized Photoexcited Carriers in GaAs[J].Phys.Rev.Lett.,1985,24:2074-2080
[7]Elsaesser T,Shah J,Rota,L et al..Initial thermalization of photoexcited carriers in GaAs studied by femtosecond luminescence spectroscopy.Phys.Rev.Lett.,1990,66:1757-1760
[8]Lin W Z,Schoenlein R W,Fujimoto J G.Femtosecond absorption saturation studies of hot carriers in GaAs and AlGaAs[J].IEEE J.Quant.Elect.,1988,24:267-275
[9]Becker P C,Fragnito H L,Brito-Cruz C H et al..Femtosecond intervalley scattering in GaAs[J].Appl.Phys.Lett.,1988,53:2089-2090
[10]Leitenstorfer A,Laubereau A,Kaiser W et al..Femtosecond Carrier Dynamics in GaAs Far from Equilibrium[,1].Phys.Rev.Lett.,1996,76:1545-1548
[11]Kash J A,Tsang J C,Hvam J M et al..Subpicosecond Time-Resolved Raman Spectroscopy of LO Phonons in GaAs[J].Phys.Rev.Lett.,1985,54:2151-2154
[12]N.,1.Turro,Modern Molecular Photochemistry,Benjamjn Publishing Co.,Ino.Inc.,1978
[13]J.A.Barltropand and J.D.Coyle,Principles of Photochemistry,Chichester,Wiley,1978
[14]J.R.Lakowicz,Principles of Fluorescence Spectroscopy,N.Y.Plencum Pr.,1983
[15]G.G.Guilbault,Practical Fluorescence Theory,Methods and Techniques,N.Y.Dekker 1973
[16]J.Guillet,Polymer Photophysics and Photochemistry,Cambridge University Press,1985
[17]Galileo Galileoi,Dialogues Concerning Two New Science,edited by H.Crew,A.de Salvio,Northwestern University Press,1950
[18]Li C Y,Wang L,Fu P M et al..Carrier dynamics in low temperature grown AlGa/GaAs multiple Quantum wells.Physical Review B,2003,67:134304-1-4
[19]Seifert G,Kaempfe M,Berg K J,Femtosecond pump-probe investigation of ultrafast silver nanoparticle deformation in a glass matrix.Appl.Phys.,2000,B71:795-800
[20]Ziolek M,Lorenc M,Naskr R et al..Determination of the temporal response function in femtosecond pump-probe systems.Appl.Phys.,2001,B72:843-847
[21]Diels J C,Rudolph W.Ultrashort Laser Pulse phenomena[M].United Kingdom Edition,London:Academic Press,Inc,1996,407-410
[22]Wollenhaupt M,Assion A,Bazhan O et al..One-parameter control of quantum dynamics using femtosecond pump-probe photoelectron spectroscopy on a model system[J].Appl.Phys.B,2002,74:S121-S125
[23]Portella M T,Rigot J Y,Schoenlein R W et al..K-space carriers dynamics in GaAs.Ultrafast Phenomena,1990,7:285-287
[24]Lin Guo,Xicheng Ai.Femtosecond optical Kerr effect of PbS nanoparticles modification effect.Materials Chemistry and Physics,2000,63:30-36
[25]Diels J C,Rudolph W.Ultrashort Laser Pulse Phenomena[M].United Kingdom Edition,London:Academic Press,Inc,1996,411-413
[26]Bevilacqua G Martinell L,Vogel E E.Jahn-Teller effect and the luminescence spectra of ZnS and ZnSe [J].Phys.Rev.B,2002,66:155338:1-5
[27]Fazzio M,Caldas J,Zunger A.Many-electron multiplet effects in the spectra of 3d impurities in heteropolar semiconductors [J].Phys.Rev.B.1984,30:3403-3435
[28]Karazhanov S Z,Ravindran P,Kjekshus A,et al..Electronic structure and optical properries of ZnX(X=O.S.Se.Te):a density functional study [J].Phys.Rev.B.2007,75:155101:1-14
[29]Y.R.Shen,et al..The principles of nonlinear optics,New York,Pp.1984,294-296
[30]H.Y.Chen,Q.C.Yang,Y H.Zuo,Electronic and optical polymer systems,Edited by D.L.Wise,G E.Wnek,et al..1998,467-493
[31]J.He,W.Ji,G H.Ma et ah.Ultrafast and large third-order nonlinear optical properties of CdS nanocrystals in polymeric film.J.Phys.Chem.B 2005,109:4373-4376
[32]R.L.Sutherland,Handbook of nonlinear optics
[33]Y.Wang,Ace.Chem.Res.1999,24,133
[34]Benjarnin S D,Loka H S,Othonos A et al..Ultrafast dynamics of nonlinear aborption in low-temperature-grown GaAs.Appl.Phys.Lett.,1996,68(18):2544-2546
[35]Mark T M,Peter K G,Timothy B K.A highly emissive heteroleptic copper(Ⅰ)bis(phenanthroline)complex.[J].Journal of American Chemical Society.1999,121:4292-4293
[36]Yin S G,Wedel A,Janietz S,et al..Synthetic and electrolumineacent properties of polymer containing phenothiazine and oxadiazole units.Synthetic Metals,2003,137(1):1145-1146
[37]Wu T Y,Chen Y.Synthesis and characterization of novel luminescent polymers with alternate phenothiazine and divinyl-benzene units.Journal of Polymer Science Part A:Polymer Chemistry,2002,40(24):4452-5564
[38]Tian Y P,Zhang M L,Yu X Q,et al..Two novel two-photon polymerization initiators with extensive application prospects.Chemical Physics Letters,2004,338:325-329
[2]Hong Ye,Wicks G W,Fauchet P M.Electron and hole dynamics in GaN.Materials Science and Engineering.2001,82:131-133
[3]Youngdahl C J,Weertman J R,Hugo R C.Deformation Behavior In nanocrystalline copper.Scriptamater,2001,44:1475-1478
[4]马国宏,郭立俊,钱士雄.飞秒物理、飞秒化学和飞秒生物学.物理,2001,6:349-355
[5]Hess C,Funk S,Bonn M.Femtosecond dynamics of chemical reactions at surfaces.Appl.Phys.A,2000,71:477-483
[6]Oudar J L,Hulin D.Migus A et al..Subpicosecond Spectral Hole Burning Due to Nonthermalized Photoexcited Carriers in GaAs[J].Phys.Rev.Lett.,1985,24:2074-2080
[7]Elsaesser T,Shah J,Rota,L et al..Initial thermalization of photoexcited carriers in GaAs studied by femtosecond luminescence spectroscopy.Phys.Rev.Lett.,1990,66:1757-1760
[8]Lin W Z,Schoenlein R W,Fujimoto J G.Femtosecond absorption saturation studies of hot carriers in GaAs and AlGaAs[J].IEEE J.Quant.Elect.,1988,24:267-275
[9]Becker P C,Fragnito H L,Brito-Cruz C H et al..Femtosecond intervalley scattering in GaAs[J].Appl.Phys.Lett.,1988,53:2089-2090
[10]Leitenstorfer A,Laubereau A,Kaiser W et al..Femtosecond Carrier Dynamics in GaAs Far from Equilibrium[,1].Phys.Rev.Lett.,1996,76:1545-1548
[11]Kash J A,Tsang J C,Hvam J M et al..Subpicosecond Time-Resolved Raman Spectroscopy of LO Phonons in GaAs[J].Phys.Rev.Lett.,1985,54:2151-2154
[12]N.,1.Turro,Modern Molecular Photochemistry,Benjamjn Publishing Co.,Ino.Inc.,1978
[13]J.A.Barltropand and J.D.Coyle,Principles of Photochemistry,Chichester,Wiley,1978
[14]J.R.Lakowicz,Principles of Fluorescence Spectroscopy,N.Y.Plencum Pr.,1983
[15]G.G.Guilbault,Practical Fluorescence Theory,Methods and Techniques,N.Y.Dekker 1973
[16]J.Guillet,Polymer Photophysics and Photochemistry,Cambridge University Press,1985
[17]Galileo Galileoi,Dialogues Concerning Two New Science,edited by H.Crew,A.de Salvio,Northwestern University Press,1950
[18]Li C Y,Wang L,Fu P M et al..Carrier dynamics in low temperature grown AlGa/GaAs multiple Quantum wells.Physical Review B,2003,67:134304-1-4
[19]Seifert G,Kaempfe M,Berg K J,Femtosecond pump-probe investigation of ultrafast silver nanoparticle deformation in a glass matrix.Appl.Phys.,2000,B71:795-800
[20]Ziolek M,Lorenc M,Naskr R et al..Determination of the temporal response function in femtosecond pump-probe systems.Appl.Phys.,2001,B72:843-847
[21]Diels J C,Rudolph W.Ultrashort Laser Pulse phenomena[M].United Kingdom Edition,London:Academic Press,Inc,1996,407-410
[22]Wollenhaupt M,Assion A,Bazhan O et al..One-parameter control of quantum dynamics using femtosecond pump-probe photoelectron spectroscopy on a model system[J].Appl.Phys.B,2002,74:S121-S125
[23]Portella M T,Rigot J Y,Schoenlein R W et al..K-space carriers dynamics in GaAs.Ultrafast Phenomena,1990,7:285-287
[24]Lin Guo,Xicheng Ai.Femtosecond optical Kerr effect of PbS nanoparticles modification effect.Materials Chemistry and Physics,2000,63:30-36
[25]Diels J C,Rudolph W.Ultrashort Laser Pulse Phenomena[M].United Kingdom Edition,London:Academic Press,Inc,1996,411-413
[26]Bevilacqua G Martinell L,Vogel E E.Jahn-Teller effect and the luminescence spectra of ZnS and ZnSe [J].Phys.Rev.B,2002,66:155338:1-5
[27]Fazzio M,Caldas J,Zunger A.Many-electron multiplet effects in the spectra of 3d impurities in heteropolar semiconductors [J].Phys.Rev.B.1984,30:3403-3435
[28]Karazhanov S Z,Ravindran P,Kjekshus A,et al..Electronic structure and optical properries of ZnX(X=O.S.Se.Te):a density functional study [J].Phys.Rev.B.2007,75:155101:1-14
[29]Y.R.Shen,et al..The principles of nonlinear optics,New York,Pp.1984,294-296
[30]H.Y.Chen,Q.C.Yang,Y H.Zuo,Electronic and optical polymer systems,Edited by D.L.Wise,G E.Wnek,et al..1998,467-493
[31]J.He,W.Ji,G H.Ma et ah.Ultrafast and large third-order nonlinear optical properties of CdS nanocrystals in polymeric film.J.Phys.Chem.B 2005,109:4373-4376
[32]R.L.Sutherland,Handbook of nonlinear optics
[33]Y.Wang,Ace.Chem.Res.1999,24,133
[34]Benjarnin S D,Loka H S,Othonos A et al..Ultrafast dynamics of nonlinear aborption in low-temperature-grown GaAs.Appl.Phys.Lett.,1996,68(18):2544-2546
[35]Mark T M,Peter K G,Timothy B K.A highly emissive heteroleptic copper(Ⅰ)bis(phenanthroline)complex.[J].Journal of American Chemical Society.1999,121:4292-4293
[36]Yin S G,Wedel A,Janietz S,et al..Synthetic and electrolumineacent properties of polymer containing phenothiazine and oxadiazole units.Synthetic Metals,2003,137(1):1145-1146
[37]Wu T Y,Chen Y.Synthesis and characterization of novel luminescent polymers with alternate phenothiazine and divinyl-benzene units.Journal of Polymer Science Part A:Polymer Chemistry,2002,40(24):4452-5564
[38]Tian Y P,Zhang M L,Yu X Q,et al..Two novel two-photon polymerization initiators with extensive application prospects.Chemical Physics Letters,2004,338:325-329