Anh Phạm Quốc Nghị, ĐH KHTN Hà Nội, đã lấy bằng PhD tại Université du Maine, France, hiện anh Nghị đang làm postdoc tại INPL-Nancy, France. Anh Nghị ủng hộ PhD Thesis và 9 bài báo của anh ấy cho thư viện ChemVN. BM cho các bài báo vào folder Hóa Vô cơ nhé.
PhD Thesis: Elaboration et caractérisation d'oxydes perovskites pour capteurs de pH - Etude du mécanisme de fonctionnement de ces capteurs
Author: Quoc Nghi PHAM
Université du Maine, France Issue date: September 2006
Các bài báo trên tạp chí quốc tế:
1, Influence of the gelator structure and solvent on the organisation and chirality of self-assembling fibrillar networks
New J. Chem., 2008
Quoc Nghi Pham, Nicolas Brosse, Céline Frochot, Dominique Dumas, Alexandre Hocquet and Brigitte Jamart-Grégoire
Abstract: Chromophoric probes of naphthalimide moieties enable evaluation of their assembling behaviour photophysically through fluorescence spectroscopy and microscopy, and circular dichroism. These experiments highlight the influence of the nature of the chemical substitution of the organogelator. Very interesting results were also obtained by performing CD experiments showing that the nature of the solvent should modify the chirality of self-assembled aggregates. Highly oriented network structures were observed in the gel state and disappeared in isotropic solution. Microfibrous self-aggregation of organogels is in situ observed via fluorescence and SHG imaging and confirmed by transmission electron microscopic analysis of the dried sample.
2, Synthesis and Characterization of Nanostructured Fast Ionic Conductor Li0.30La0.56TiO3
Chem. Mater., 18 (18), 4385 -4392, 2006
Quoc Nghi Pham, Claude Bohnké, Marie-Pierre Crosnier-Lopez, and Odile Bohnké
Abstract:
The preparation of a pure and nanostructured phase of the fast lithium conductor Li0.30La0.56TiO3 at low temperature (350 C for 2 h) is reported for the first time. The synthesis has been carried out by the Pechini-type in-situ polymerizable method. It has been shown that the molar ratios ethylene glycol/citric acid and citric acid/metals, as well as the temperature, are crucial parameters during this synthesis. A careful control of the temperature during polyesterification allowed us to prepare the nanosized phase of oxide and to avoid the formation of thermally stable impurities. The crystallite size (20-30 nm) of the oxide has been determined by the analysis of the broadening of the powder X-ray diffraction lines. The particles size has been confirmed by transmission electron microscopy and the macroporous character of the powder has been evidenced by scanning electron microscopy.
3, Synthesis of the perovskite ceramic Li3xLa2/3–xTiO3 by a chemical solution route using a triblock copolymer surfactant
Journal of Sol-Gel Science and Technology, Volume 46, Number 2 / May, 2008, 137-145
Thi Ngoc Ha Le, Mickaël Roffat, Quoc Nghi Pham, Stéphanie Kodjikian, Odile Bohnke and Claude Bohnke
Abstract: The synthesis of the perovskite Li3xLa2/3–x□1/3–2xTiO3 by a chemical solution route, using a triblock copolymer surfactant, PEOn–PPOm–PEOn, is described. This titanate is a non-hygroscopic fast lithium conductor and therefore is a good candidate for electrochemical applications. It is generally prepared by a conventional solid-state reaction (SSR) method. However this synthesis method does not allow the preparation of nanopowders or the formation of thin films. For these special purposes, synthesis by a chemical solution route, with the formation of a polymeric precursor during synthesis, has been investigated. By using the above-mentioned non-ionic surfactant, the preparation of nanopowders of complex oxides can be done. Furthermore, this way of synthesis leads to the formation of an intermediate polymeric precursor which can be easily spread on substrates to obtain films. We show that the formation of a pure phase of the perovskite Li3xLa2/3–x□1/3–2xTiO3 is highly dependent on the synthesis conditions, namely the presence of water in the solvent, the EO/metal ratio, the Li+ content in the precursor and the calcination temperature. The influence of these parameters on the microstructure of the oxide is studied by X-ray diffraction, scanning electron microscopy and granulometry. A powder of Li3xLa2/3–x□1/3–2xTiO3 (x = 0.10), with an average particles size of 200 nm, has been obtained. The ionic conductivity of this oxide is the same as the one obtained with oxide prepared by SSR (a bulk conductivity of 1.4 × 10−3 S/cm at 37 °C). The ceramic obtained from this powder after sintering at 1,150 °C shows a good pH response. This material can then be used as a sensitive membrane in a potentiometric pH sensor. The presence of hydrophobic PPO groups in the polymer precursor allowed preparing films of Li3xLa2/3–x□1/3–2xTiO3 with a good adherence on Pt substrate. This kind of synthesis is then very promising to prepare micro pH sensors.
4, Potentiometric measurements and impedance characteristics of Li0.30La0.57TiO3 membrane in lithium anhydrous solutions
The potentiometric response of the Li+ ion-selective electrode based on the fast ion conductor Li3xLa2/3−xTiO3 (x = 0.10) membrane (named LLTO) as well as the impedance of the LLTO membrane/Li+ solution in either anhydrous or hydrated PC solvent have been carried out. A four-electrode configuration has been used for the investigation of the interfacial phenomenon. It has been shown that the LLTO membrane can be used to detect the Li+ activity in anhydrous solutions through a Li+ ion exchange mechanism. The potentiometric response shows a Nernstian behavior with a Li+ sensitivity of −72 mV/decade at 25 °C. This high sensitivity can be correlated to a localised hydroxylation of the oxide surface with the residual water present in the solution in combination to the Li+ exchange reaction. An apparent standard current density of 12 μA/cm2 and a charge-transfer coefficient of 0.29 have been determined. However, as water content in the electrolyte increases, the activity domain of the detection decreases to lead to the disappearance of the Li+ ion exchange mechanism in Li+ aqueous solution. This annihilation of the exchange process may be due to the predominant catalytic reaction of [Ti–O]− with H2O and/or to the formation of a water layer on the oxide surface.
5, Synthesis and electrical characterization of Li0.30Ca0.35TaO3 perovskite synthesized via a polymerized complex route
Journal of Solid State Chemistry, Volume 178, Issue 6, June 2005, Pages 1915-1924
Quoc Nghi Pham, Murugesan Vijayakumar, Claude Bohnke, Odile Bohnke
Abstract
The synthesis of Li0.30Ca0.35TaO3 perovskite by a Pechini-type polymerizable precursor method is carefully described. The thermal decomposition of the precursor and the formation of a pure perovskite phase were investigated by means of differential thermal analysis–thermogravimetric analysis (DTA–TGA) and XRD techniques. A pure and well-crystallized phase has been obtained at a lower temperature and with a much shorter synthesis time than the phase obtained by conventional solid-state reaction method. The morphology of the powder after heating at 1300 °C was observed by laser granulometry, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Impedance spectroscopy data allowed us to determine the electrical properties, i.e., permittivity and dc-conductivity, of the bulk and grain boundaries. The results are discussed on the assumption of the brick layer model.
6, A new perovskite phase Li2xCa0.5−xTaO3: Li+ ion conductivity and use as pH sensor
Solid State Ionics, Volume 176, Issues 5-6, 14 February 2005, Pages 495-504
Quoc Nghi Pham, Claude Bohnke, Joël Emery, Odile Bohnke, Françoise Le Berre, Marie-Pierre Crosnier-Lopez, Jean-Louis Fourquet, Pierre Florian
Abstract
Several compounds of a new solid solution Li2xCa0.5−xTaO3 (0.05≤x≤0.25) with perovskite structure have been synthesised by classical solid state reaction. It has been found that synthesis at 1773 K followed by a quenching in air was necessary to obtain a pure perovskite phase. The cell parameters and their variation with composition x have been determined through X-ray diffraction patterns analysis. Scanning electron microscopy showed the presence of grains of 10 μm size and of aggregates of 50–100 μm thick. Impedance spectroscopy in the frequency range from 10 MHz to 1 Hz and in the temperature range from 348 to 573 K has been carried out to determine the electrical properties. A bulk dc-conductivity slightly higher than 10−6 S cm−1 has been found at 473 K. 7Li nuclear magnetic resonance relaxation times, T1 and T1ρ, vs. inverse of temperature have been measured to investigate the microscopic ionic motions of Li+ ions. Two motions of Li+ ions, a short and a long range one, are evidenced by these experiments. Furthermore, the Galvani potential of the ionic conductive membrane electrode, when put in contact with an aqueous solution, depends on the pH of the solution. The fast response on pH variation enables it then to be used as pH sensor in aqueous solutions.
7, Lithium lanthanum titanate ceramic as sensitive material for pH sensor: Influence of synthesis methods and powder grains size
Journal of the European Ceramic Society, Volume 25, Issue 12, 2005, Pages 2973-2976
Murugesan Vijayakumar, Quoc Nghi Pham, Claude Bohnke
Abstract
The lithium lanthanum titanate (LLTO), prepared by two different methods (solid state reaction and sol–gel), has been studied as sensitive element for detecting the pH variations in aqueous solutions when used as a potentiometric sensor. This property is dependent on mechanical and thermal treatments of the synthesised powder. A screening design was performed with the material obtained by solid state reaction. Several parameters (grinding time, heating rate for sintering process…) have been optimized. The main step, which increases the sensitivity, is the grinding of the powder before a heat treatment when the LLTO is synthesised by solid state reaction. We suppose that a small grains size of the powder is favourable to the pH variations sensitivity. A comparison with LLTO synthesised by the sol–gel route without grinding is also shown. The sensitivities of these two materials to the pH variations are very similar.
8, Effect of surface treatments on Li0.30Ln0.57TiO3 (Ln = La, Nd) perovskite ceramics: an X-ray photoelectron spectroscopy study
To explain the sensitivity of some titanate ceramics to pH variation in aqueous solutions, the lithium lanthanum titanate (LLTO) and lithium neodymium titanate (NLTO) surfaces were analysed by X-ray photoelectron spectroscopy. The surface of LLTO was modified by chemical treatments and sputtering. XPS spectrum of LLTO exhibits the peaks of lanthanum (La 3d3/2, La 3d5/2, La 4p, La 4d), titanium (Ti 2p1/2, Ti 2p3/2) and oxygen (O 1s). However, the immersion of the ceramic in sodium hydroxide or surface sputtering affect mainly the narrow-scan spectra of oxygen (O 1s). This study reveals that an acido-basic reaction takes place in the neighbourhood of the TiO6 octahedra of the perovskite. The results also suggest that hydroxyl species may associate with lanthanum. Furthermore, the study on C 1s line rules out the assumption that View the MathML source species are involved in the pH detection.
9, Crystal structure of new Li+ ion conducting perovskites: Li2xCa0.5−xTaO3 and Li0.2[Ca1−ySry]0.4TaO3
Solid State Sciences, Volume 6, Issue 9, September 2004, Pages 923-929
Quoc Nghi Pham, Marie-Pierre Crosnier-Lopez, Françoise Le Berre, François Fauth, Jean-Louis Fourquet
Abstract
Two new solid solutions—Li2xCa0.5−xTaO3 (0.05<x<0.25) and Li0.2[Ca1−ySry]0.4TaO3 (0<y<0.15)—based on the A defective ABO3 perovskite structural type, are synthesized. The crystal structures of these Li+ ion conducting compounds are solved from synchrotron radiation and conventional X-ray powder diffraction data. The unit cells exhibit a classical orthorhombic distortion of the cubic perovskite model (space group Pnma No. 62) with parameters close to Image , 2ap, Image (ap, primitive cubic cell parameter). The distortion of the cubic aristotype arises from the three tilts system a+b−b− of the TaO6 octahedra. For the same lithium content (x=0.10), the Sr2+ substitution to Ca2+ is found to enhance the electrical conductivity by quasi-one order of magnitude (at 200 °C, bulk dc conductivity values are close to 2.3×10−6 and 1.1×10−5 S cm−1 for Li0.2Ca0.4TaO3 and Li0.2[Ca0.9Sr0.1]0.4TaO3, respectively).
Cảm ơn anh Phạm Quốc Nghị đã ủng hộ tài liệu cho thư viện Chemvn. Các bạn quan tâm truy cập http://lib.chemvn.net để download nhé.
Trích:
Nguyên văn bởi aqhl
Anh Phạm Quốc Nghị, ĐH KHTN Hà Nội, đã lấy bằng PhD tại Université du Maine, France, hiện anh Nghị đang làm postdoc tại INPL-Nancy, France. Anh Nghị ủng hộ PhD Thesis và 9 bài báo của anh ấy cho thư viện ChemVN. BM cho các bài báo vào folder Hóa Vô cơ nhé.
PhD Thesis: Elaboration et caractérisation d'oxydes perovskites pour capteurs de pH - Etude du mécanisme de fonctionnement de ces capteurs
Author: Quoc Nghi PHAM
Université du Maine, France Issue date: September 2006
Các bài báo trên tạp chí quốc tế:
Trích:
1, Influence of the gelator structure and solvent on the organisation and chirality of self-assembling fibrillar networks
New J. Chem., 2008
Quoc Nghi Pham, Nicolas Brosse, Céline Frochot, Dominique Dumas, Alexandre Hocquet and Brigitte Jamart-Grégoire
Abstract: Chromophoric probes of naphthalimide moieties enable evaluation of their assembling behaviour photophysically through fluorescence spectroscopy and microscopy, and circular dichroism. These experiments highlight the influence of the nature of the chemical substitution of the organogelator. Very interesting results were also obtained by performing CD experiments showing that the nature of the solvent should modify the chirality of self-assembled aggregates. Highly oriented network structures were observed in the gel state and disappeared in isotropic solution. Microfibrous self-aggregation of organogels is in situ observed via fluorescence and SHG imaging and confirmed by transmission electron microscopic analysis of the dried sample.
Trích:
2, Synthesis and Characterization of Nanostructured Fast Ionic Conductor Li0.30La0.56TiO3
Chem. Mater., 18 (18), 4385 -4392, 2006
Quoc Nghi Pham, Claude Bohnké, Marie-Pierre Crosnier-Lopez, and Odile Bohnké
Abstract:
The preparation of a pure and nanostructured phase of the fast lithium conductor Li0.30La0.56TiO3 at low temperature (350 C for 2 h) is reported for the first time. The synthesis has been carried out by the Pechini-type in-situ polymerizable method. It has been shown that the molar ratios ethylene glycol/citric acid and citric acid/metals, as well as the temperature, are crucial parameters during this synthesis. A careful control of the temperature during polyesterification allowed us to prepare the nanosized phase of oxide and to avoid the formation of thermally stable impurities. The crystallite size (20-30 nm) of the oxide has been determined by the analysis of the broadening of the powder X-ray diffraction lines. The particles size has been confirmed by transmission electron microscopy and the macroporous character of the powder has been evidenced by scanning electron microscopy.
Trích:
3, Synthesis of the perovskite ceramic Li3xLa2/3–xTiO3 by a chemical solution route using a triblock copolymer surfactant
Journal of Sol-Gel Science and Technology, Volume 46, Number 2 / May, 2008, 137-145
Thi Ngoc Ha Le, Mickaël Roffat, Quoc Nghi Pham, Stéphanie Kodjikian, Odile Bohnke and Claude Bohnke
Abstract: The synthesis of the perovskite Li3xLa2/3–x□1/3–2xTiO3 by a chemical solution route, using a triblock copolymer surfactant, PEOn–PPOm–PEOn, is described. This titanate is a non-hygroscopic fast lithium conductor and therefore is a good candidate for electrochemical applications. It is generally prepared by a conventional solid-state reaction (SSR) method. However this synthesis method does not allow the preparation of nanopowders or the formation of thin films. For these special purposes, synthesis by a chemical solution route, with the formation of a polymeric precursor during synthesis, has been investigated. By using the above-mentioned non-ionic surfactant, the preparation of nanopowders of complex oxides can be done. Furthermore, this way of synthesis leads to the formation of an intermediate polymeric precursor which can be easily spread on substrates to obtain films. We show that the formation of a pure phase of the perovskite Li3xLa2/3–x□1/3–2xTiO3 is highly dependent on the synthesis conditions, namely the presence of water in the solvent, the EO/metal ratio, the Li+ content in the precursor and the calcination temperature. The influence of these parameters on the microstructure of the oxide is studied by X-ray diffraction, scanning electron microscopy and granulometry. A powder of Li3xLa2/3–x□1/3–2xTiO3 (x = 0.10), with an average particles size of 200 nm, has been obtained. The ionic conductivity of this oxide is the same as the one obtained with oxide prepared by SSR (a bulk conductivity of 1.4 × 10−3 S/cm at 37 °C). The ceramic obtained from this powder after sintering at 1,150 °C shows a good pH response. This material can then be used as a sensitive membrane in a potentiometric pH sensor. The presence of hydrophobic PPO groups in the polymer precursor allowed preparing films of Li3xLa2/3–x□1/3–2xTiO3 with a good adherence on Pt substrate. This kind of synthesis is then very promising to prepare micro pH sensors.
Trích:
4, Potentiometric measurements and impedance characteristics of Li0.30La0.57TiO3 membrane in lithium anhydrous solutions
The potentiometric response of the Li+ ion-selective electrode based on the fast ion conductor Li3xLa2/3−xTiO3 (x = 0.10) membrane (named LLTO) as well as the impedance of the LLTO membrane/Li+ solution in either anhydrous or hydrated PC solvent have been carried out. A four-electrode configuration has been used for the investigation of the interfacial phenomenon. It has been shown that the LLTO membrane can be used to detect the Li+ activity in anhydrous solutions through a Li+ ion exchange mechanism. The potentiometric response shows a Nernstian behavior with a Li+ sensitivity of −72 mV/decade at 25 °C. This high sensitivity can be correlated to a localised hydroxylation of the oxide surface with the residual water present in the solution in combination to the Li+ exchange reaction. An apparent standard current density of 12 μA/cm2 and a charge-transfer coefficient of 0.29 have been determined. However, as water content in the electrolyte increases, the activity domain of the detection decreases to lead to the disappearance of the Li+ ion exchange mechanism in Li+ aqueous solution. This annihilation of the exchange process may be due to the predominant catalytic reaction of [Ti–O]− with H2O and/or to the formation of a water layer on the oxide surface.
Trích:
5, Synthesis and electrical characterization of Li0.30Ca0.35TaO3 perovskite synthesized via a polymerized complex route
Journal of Solid State Chemistry, Volume 178, Issue 6, June 2005, Pages 1915-1924
Quoc Nghi Pham, Murugesan Vijayakumar, Claude Bohnke, Odile Bohnke
Abstract
The synthesis of Li0.30Ca0.35TaO3 perovskite by a Pechini-type polymerizable precursor method is carefully described. The thermal decomposition of the precursor and the formation of a pure perovskite phase were investigated by means of differential thermal analysis–thermogravimetric analysis (DTA–TGA) and XRD techniques. A pure and well-crystallized phase has been obtained at a lower temperature and with a much shorter synthesis time than the phase obtained by conventional solid-state reaction method. The morphology of the powder after heating at 1300 °C was observed by laser granulometry, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Impedance spectroscopy data allowed us to determine the electrical properties, i.e., permittivity and dc-conductivity, of the bulk and grain boundaries. The results are discussed on the assumption of the brick layer model.
Trích:
6, A new perovskite phase Li2xCa0.5−xTaO3: Li+ ion conductivity and use as pH sensor
Solid State Ionics, Volume 176, Issues 5-6, 14 February 2005, Pages 495-504
Quoc Nghi Pham, Claude Bohnke, Joël Emery, Odile Bohnke, Françoise Le Berre, Marie-Pierre Crosnier-Lopez, Jean-Louis Fourquet, Pierre Florian
Abstract
Several compounds of a new solid solution Li2xCa0.5−xTaO3 (0.05≤x≤0.25) with perovskite structure have been synthesised by classical solid state reaction. It has been found that synthesis at 1773 K followed by a quenching in air was necessary to obtain a pure perovskite phase. The cell parameters and their variation with composition x have been determined through X-ray diffraction patterns analysis. Scanning electron microscopy showed the presence of grains of 10 μm size and of aggregates of 50–100 μm thick. Impedance spectroscopy in the frequency range from 10 MHz to 1 Hz and in the temperature range from 348 to 573 K has been carried out to determine the electrical properties. A bulk dc-conductivity slightly higher than 10−6 S cm−1 has been found at 473 K. 7Li nuclear magnetic resonance relaxation times, T1 and T1ρ, vs. inverse of temperature have been measured to investigate the microscopic ionic motions of Li+ ions. Two motions of Li+ ions, a short and a long range one, are evidenced by these experiments. Furthermore, the Galvani potential of the ionic conductive membrane electrode, when put in contact with an aqueous solution, depends on the pH of the solution. The fast response on pH variation enables it then to be used as pH sensor in aqueous solutions.
Trích:
7, Lithium lanthanum titanate ceramic as sensitive material for pH sensor: Influence of synthesis methods and powder grains size
Journal of the European Ceramic Society, Volume 25, Issue 12, 2005, Pages 2973-2976
Murugesan Vijayakumar, Quoc Nghi Pham, Claude Bohnke
Abstract
The lithium lanthanum titanate (LLTO), prepared by two different methods (solid state reaction and sol–gel), has been studied as sensitive element for detecting the pH variations in aqueous solutions when used as a potentiometric sensor. This property is dependent on mechanical and thermal treatments of the synthesised powder. A screening design was performed with the material obtained by solid state reaction. Several parameters (grinding time, heating rate for sintering process…) have been optimized. The main step, which increases the sensitivity, is the grinding of the powder before a heat treatment when the LLTO is synthesised by solid state reaction. We suppose that a small grains size of the powder is favourable to the pH variations sensitivity. A comparison with LLTO synthesised by the sol–gel route without grinding is also shown. The sensitivities of these two materials to the pH variations are very similar.
Trích:
8, Effect of surface treatments on Li0.30Ln0.57TiO3 (Ln = La, Nd) perovskite ceramics: an X-ray photoelectron spectroscopy study
To explain the sensitivity of some titanate ceramics to pH variation in aqueous solutions, the lithium lanthanum titanate (LLTO) and lithium neodymium titanate (NLTO) surfaces were analysed by X-ray photoelectron spectroscopy. The surface of LLTO was modified by chemical treatments and sputtering. XPS spectrum of LLTO exhibits the peaks of lanthanum (La 3d3/2, La 3d5/2, La 4p, La 4d), titanium (Ti 2p1/2, Ti 2p3/2) and oxygen (O 1s). However, the immersion of the ceramic in sodium hydroxide or surface sputtering affect mainly the narrow-scan spectra of oxygen (O 1s). This study reveals that an acido-basic reaction takes place in the neighbourhood of the TiO6 octahedra of the perovskite. The results also suggest that hydroxyl species may associate with lanthanum. Furthermore, the study on C 1s line rules out the assumption that View the MathML source species are involved in the pH detection.
Trích:
9, Crystal structure of new Li+ ion conducting perovskites: Li2xCa0.5−xTaO3 and Li0.2[Ca1−ySry]0.4TaO3
Solid State Sciences, Volume 6, Issue 9, September 2004, Pages 923-929
Quoc Nghi Pham, Marie-Pierre Crosnier-Lopez, Françoise Le Berre, François Fauth, Jean-Louis Fourquet
Abstract
Two new solid solutions—Li2xCa0.5−xTaO3 (0.05<x<0.25) and Li0.2[Ca1−ySry]0.4TaO3 (0<y<0.15)—based on the A defective ABO3 perovskite structural type, are synthesized. The crystal structures of these Li+ ion conducting compounds are solved from synchrotron radiation and conventional X-ray powder diffraction data. The unit cells exhibit a classical orthorhombic distortion of the cubic perovskite model (space group Pnma No. 62) with parameters close to Image , 2ap, Image (ap, primitive cubic cell parameter). The distortion of the cubic aristotype arises from the three tilts system a+b−b− of the TaO6 octahedra. For the same lithium content (x=0.10), the Sr2+ substitution to Ca2+ is found to enhance the electrical conductivity by quasi-one order of magnitude (at 200 °C, bulk dc conductivity values are close to 2.3×10−6 and 1.1×10−5 S cm−1 for Li0.2Ca0.4TaO3 and Li0.2[Ca0.9Sr0.1]0.4TaO3, respectively).
thay đổi nội dung bởi: bluemonster, ngày 05-12-2008 lúc 05:32 AM.
Anh Nguyễn Chí Sơn, BM Hóa Lý, vừa ủng hộ thư viện ChemVN Master thesis (cả 2 bản tiếng Anh và Tiếng Việt) cùng 3 bài báo trên các journal. Nick trên 4rum của anh Sơn là ncson, hiện nay anh tạm thời quy ẩn, nên nhờ mình up hộ lên 4rum. Tháng 8 năm nay anh Sơn sẽ sang học PhD bên USA (University of California, Berkeley). Chúc anh Sơn thành công và đóng góp nhiều paper nữa cho ChemVN. BM cho các bài báo vào folder Hóa Tính toán nhé.
Master Thesis: Linear Dichroism Spectroscopic and Theoretical Investigations of the compound Emodin
Author: Nguyen Chi Son
Roskilde University, Denmark Issue date: 2004
Abstract: The LD UV-VIS spectra of Emodin (1,3,8-trihydroxy-6-methyl anthraquinone) in stretched PE and PVA have been recorded and analysed. Orientation factor of the observed electronic transition were determined through stepwise reduction. The electronic transition moment direction of observed transition is determined by the assumption of molecule has Cs symmetry. The observed electronic transition moment directions belong to the “long” and “short” molecular symmetry axes. This information leads to the conclusion that Emodin still remembers the exited states of parent molecule, Chrysazin. When changing from PE solvent to PVA solvent, almost electronic transitions have small red shift by 200 – 500 cm-1, except a strong band at 44500 cm-1 don’t move anymore, the electronic transition moment directions of observed transitions still remain.
The LD UV-VIS spectra of Emodin anion in stretched PVA also have been recorded and analysed. The electronic transitions of anion are completely different the electronic transitions of neutral molecule because of redistribution of negative charge. The observed electronic transition moment directions do not belong to the “long” and “short” molecular symmetry axes.
The TD-DFT calculation, B3LYP/6-31G+(d,p)//B3LYP/6-31G(d,p), has a good agreement to the assignment of observed transitions in both transitions and its moment directions.
Các bài báo trên tạp chí quốc tế:
1, A computational study of halomethyllithium carbenoid mixed aggregates with lithium halides and lithium methoxide
Lawrence M. Pratt, Shayla Merry, Son Chi Nguyen, Phung Quan, B.T. Thanh
Tetrahedron, Volume 62, Issue 47, 20 November 2006, Pages 10821-10828
Abstract
Density functional theory calculations were used to examine the formation of lithium halide and lithium alkoxide mixed aggregates with halomethyllithium carbenoids. These mixed aggregates may be the important intermediates in carbenoid reactions where lithium halides are formed as byproducts, or when the mixture has been exposed to small amounts of air. The calculations showed that in the gas phase and in THF solution, mixed dimers, trimers, and tetramers may coexist with free lithium carbenoids, depending on the lithium salt. The calculations also indicated that mixed aggregates may influence the activation free energies of cyclopropanation reactions of lithium carbenoids.
2, Electronic states of emodin and its conjugate base. Synchrotron linear dichroism spectroscopy and quantum chemical calculations
Nguyen Chi Son, Bjarke Knud Vilster Hansen, Søren Vrønning Hoffmann and Jens Spanget-Larsen
Submitted to Physical Chemistry Chemical Physics (PCCP)
Abstract: The electronic transitions of emodin (1,3,8-trihydroxy-6-methyl-9,10-anthraquinone, E) and its conjugate base (3-oxido-6-methyl-1,8-dihydroxy-9,10-anthraquinone, Ecb) were investigated by UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched poly(vinylalcohol). The experiments in the UV region were performed with synchrotron radiation, thereby obtaining significantly improved signal to noise ratio compared with traditional technology. The LD spectra provided information on the polarization directions of the observed transitions, thereby leading to resolution of otherwise overlapping, differently polarized transitions. The investigation was supported by PCM-TD-DFT calculations; a mixed discrete/continuum solvation model was applied in the case of the strongly solvated Ecb anion. The calculations led to excellent agreement with the observed transitions, resulting in the assignment of at least 7 excited electronic states in the region 15000 – 50000 cm-1 for each species. A recent assignment of the absorption spectrum of E to a superposition of contributions from 9,10- and 1,10-anthraquinoid tautomeric forms was not supported by the results of the present investigation.
3, Calculation of the solvation state of organolithium compounds: Effects of basis sets and electron correlation methods.
Lawrence M. Pratt, Darrel Jones, Andrea Sease, Donta Busch, Emmanuel Faluade, Son C. Nguyen, Bui T. Thanh
Accepted in International Journal of Quantum Chemistry, 2008
Abstract: The free energies of successive solvation of organolithium species by THF ligands was examined by DFT and ab initio methods. The popular B3LYP method using three different basis sets, and the MPW1PW91/6-31+G(d) DFT method, were compared to MP2 calculations, and when possible, to the G3MP2 method. The DFT methods generally underestimated the exergonic free energies of solvation compared to MP2 and G3MP2.
thay đổi nội dung bởi: aqhl, ngày 05-02-2008 lúc 07:18 PM.
Cảm ơn thầy Nguyễn Chí Sơn đã đóng góp tài liệu cho thư viện Chemvn. Các bạn quan tâm có thể vào http://lib.chemvn.net để download nhé.
Trích:
Master Thesis: Linear Dichroism Spectroscopic and Theoretical Investigations of the compound Emodin
Author: Nguyen Chi Son
Roskilde University, Denmark Issue date: 2004
Abstract: The LD UV-VIS spectra of Emodin (1,3,8-trihydroxy-6-methyl anthraquinone) in stretched PE and PVA have been recorded and analysed. Orientation factor of the observed electronic transition were determined through stepwise reduction. The electronic transition moment direction of observed transition is determined by the assumption of molecule has Cs symmetry. The observed electronic transition moment directions belong to the “long” and “short” molecular symmetry axes. This information leads to the conclusion that Emodin still remembers the exited states of parent molecule, Chrysazin. When changing from PE solvent to PVA solvent, almost electronic transitions have small red shift by 200 – 500 cm-1, except a strong band at 44500 cm-1 don’t move anymore, the electronic transition moment directions of observed transitions still remain.
The LD UV-VIS spectra of Emodin anion in stretched PVA also have been recorded and analysed. The electronic transitions of anion are completely different the electronic transitions of neutral molecule because of redistribution of negative charge. The observed electronic transition moment directions do not belong to the “long” and “short” molecular symmetry axes.
The TD-DFT calculation, B3LYP/6-31G+(d,p)//B3LYP/6-31G(d,p), has a good agreement to the assignment of observed transitions in both transitions and its moment directions.
Các bài báo trên tạp chí quốc tế:
Trích:
1, A computational study of halomethyllithium carbenoid mixed aggregates with lithium halides and lithium methoxide
Lawrence M. Pratt, Shayla Merry, Son Chi Nguyen, Phung Quan, B.T. Thanh
Tetrahedron, Volume 62, Issue 47, 20 November 2006, Pages 10821-10828
Abstract
Density functional theory calculations were used to examine the formation of lithium halide and lithium alkoxide mixed aggregates with halomethyllithium carbenoids. These mixed aggregates may be the important intermediates in carbenoid reactions where lithium halides are formed as byproducts, or when the mixture has been exposed to small amounts of air. The calculations showed that in the gas phase and in THF solution, mixed dimers, trimers, and tetramers may coexist with free lithium carbenoids, depending on the lithium salt. The calculations also indicated that mixed aggregates may influence the activation free energies of cyclopropanation reactions of lithium carbenoids.
Trích:
2, Electronic states of emodin and its conjugate base. Synchrotron linear dichroism spectroscopy and quantum chemical calculations
Nguyen Chi Son, Bjarke Knud Vilster Hansen, Søren Vrønning Hoffmann and Jens Spanget-Larsen
Submitted to Physical Chemistry Chemical Physics (PCCP)
Abstract: The electronic transitions of emodin (1,3,8-trihydroxy-6-methyl-9,10-anthraquinone, E) and its conjugate base (3-oxido-6-methyl-1,8-dihydroxy-9,10-anthraquinone, Ecb) were investigated by UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched poly(vinylalcohol). The experiments in the UV region were performed with synchrotron radiation, thereby obtaining significantly improved signal to noise ratio compared with traditional technology. The LD spectra provided information on the polarization directions of the observed transitions, thereby leading to resolution of otherwise overlapping, differently polarized transitions. The investigation was supported by PCM-TD-DFT calculations; a mixed discrete/continuum solvation model was applied in the case of the strongly solvated Ecb anion. The calculations led to excellent agreement with the observed transitions, resulting in the assignment of at least 7 excited electronic states in the region 15000 – 50000 cm-1 for each species. A recent assignment of the absorption spectrum of E to a superposition of contributions from 9,10- and 1,10-anthraquinoid tautomeric forms was not supported by the results of the present investigation.
Trích:
3, Calculation of the solvation state of organolithium compounds: Effects of basis sets and electron correlation methods.
Lawrence M. Pratt, Darrel Jones, Andrea Sease, Donta Busch, Emmanuel Faluade, Son C. Nguyen, Bui T. Thanh
Accepted in International Journal of Quantum Chemistry, 2008
Abstract: The free energies of successive solvation of organolithium species by THF ligands was examined by DFT and ab initio methods. The popular B3LYP method using three different basis sets, and the MPW1PW91/6-31+G(d) DFT method, were compared to MP2 calculations, and when possible, to the G3MP2 method. The DFT methods generally underestimated the exergonic free energies of solvation compared to MP2 and G3MP2.
thay đổi nội dung bởi: bluemonster, ngày 05-12-2008 lúc 05:34 AM.
Đáp ứng lời kêu gọi của ban quản trị diễn đàn, lipid70 xin đóng góp 2 bài báo nhỏ nhằm xây dựng chủ đề này ngày càng hưng thịnh hơn.
Bluemonster: Đã nhận các file, BM delete file attach nhé !
thay đổi nội dung bởi: bluemonster, ngày 05-02-2008 lúc 09:07 PM.
Những thành viên sau CẢM ƠN bạn lipid70 vì ĐỒNG Ý với ý kiến của bạn:
Bạn lipid70 hiện đang là giảng viên Khoa Khoa học Cơ bản, Trường Đại học Y Dược TpHCM. Nhiệt liệt chào mừng bạn tham gia và đóng góp cho Diễn đàn Hóa học ChemVN. Chúc bạn sớm tìm được học bổng PhD như ý muốn.
Cảm ơn anh Nguyễn Thành Trung - lipid70 đã đóng góp tài liệu cho thư viện Chemvn. Các bạn quan tâm hãy vào http://lib.chemvn.net để download nhé.
1. Preparation and structural characterization of a new class of stable thioetones: ortho-hydroxythioacetophenones
Trung Thanh Nguyen, Thach Ngoc Le, Poul Erik Hansen and Fritz Duus
Tetrahedron Letters 47 (2006) 8433–8435
Abstract:
Ortho-hydroxythioacetophenone and four structurally related ortho-hydroxyaryl methyl thioketones have been prepared from the corresponding ketones by reaction with gaseous H2S and HCl in ethanol under strictly controlled reaction conditions. The remarkable stability of the new monomeric thioketones seems to be due to a strong intramolecular O-H...S=C hydrogen bonding.
2. Intramolecular hydrogen bonding of novel o-hydroxythioacetophenones and related compounds evaluated by deuterium isotope effects on (13)C chemical shifts
Trung Thanh Nguyen, Thach Ngoc Le, Fritz Duus, Bjarke K. V. Hansen and
Poul Erik Hansen
Magn. Reson. Chem. 2007; 45: 245–252
Abstract:
A new class of compounds, the 2-hydroxythioacetophenones, and related compounds have recently been synthesized. The hydrogen-bond system has been characterized by NMR chemical shifts and deuterium isotope effects on these as well as by DFT calculations. Use of solid-state (13)C NMR has enabled measurements of the intrinsic deuterium isotope effects of the most abundant tautomer of -thioxoketones. The compounds show very interesting long-range deuterium isotope effects on the thiocarbonyl carbon. The intramolecular hydrogen bonds of o-hydroxythioacetophenones are found to be slightly stronger than those of the corresponding acetophenones. The reactivity and stability of the compounds can be related to hydrogen bonding and to the presence of electron donating substituents.
thay đổi nội dung bởi: bluemonster, ngày 05-12-2008 lúc 05:35 AM.
Anh Cổ Thanh Thiện, đã lấy bằng PhD ở South Korea, hiện nay đang công tác tại Viện Khoa học Vật liệu Ứng Dụng TpHCM. Anh Thiện ủng hộ 5 bài báo cho Thư viện ChemVN. BM cho các bài báo vào folder Hoá Xúc tác nhé.
1, 1,2-Ferrocenediylazaphosphinines 3: A New Class of Planar Chiral Ligands for Cu-Catalyzed Cyclopropanation
Seung Hwan Paek, Thanh-Thien Co, Dong Ho Lee, Yu Chul Park, and Tae-Jeong Kim
Bull. Korean Chem. Soc. 2002, Vol. 23, No. 12, 1702
Abstract:
The synthesis and catalytic application of a new class of planar chiral ferrocenes, 1,2-ferrocenediylazaphosphinines (1 and 2) are described. They are powerful ligands for the copper(I)-catalyzed asymmetric cyclopropanation of a range of alkenes with diazo esters to exhibit an exceptionally high degree of diastereoselectivity (~100% de) in favor of trans isomers, regardless the structure of the olefins and the diazo compounds. Comparative studies between 1 and 2 reveal that the former works better in terms of
diastereocontrol. In contrast, however, enantioselectivity is low with both 1 and 2 as a whole although, in certain cases with a proper combination of the olefin and the diazo ester, high optical yields (up to 100% ee) can be achieved. Other reaction parameters such as the reaction temperature and the structure of the ligand do exhibit some influence, although infinitestimal, on both chemical and optical yields.
2, Chiral [Iminophosphoranyl]ferrocenes: Synthesis, Coordination Chemistry, and Catalytic Application
Thanh Thien Co, Sang Chul Shim, Chan Sik Cho, Dong-Uk Kim, and Tae-Jeong Kim
Bull. Korean Chem. Soc. 2005, Vol. 26, No. 9, 1359
Abstract:
A series of new chiral [iminophosphoranyl]ferrocenes, {η5-C5H4-(PPh2=N-2,6-R2-C6H3)}Fe{η5-C5H3-1-PPh2-2-CH(Me)NMe2} (1: R = Me, iPr), {η5-C5H4-(PPh2=N-2,6-R21-C6H3)}Fe{η5-C5H3-1-(PPh2=N-2,6-R2-C6H3)-2-CH(Me)R2} (2: R1 = Me, Pr; R2 = NMe2, OMe), and (η5-C5H5)Fe{η5-C5H4-1-PR2-2-CH(Me)N=PPh3} (3:R = Ph, C6H11) have been prepared from the reaction of [1,1'-diphenylphosphino-2-(N,N-dimethylamino) ethyl]ferrocene with arylazides (1 & 2) and the reaction of phosphine dichlorides (R3PCl2) with [1,1'- diphenylphosphino-2-aminoethyl]ferrocene (3), respectively. They form palladium complexes of the type [Pd(C3H5)(L)]BF4 (4-6: L = 1-3), where the ligand (L) adopts an η2-N,N (2) or η2-P,N (3) as expected. In the case of 1, a potential terdentate, an η2-P,N mode is realized with the exclusion of the ?P=NAr group from the coordination sphere. Complexes 4-6 were employed as catalysts for allylic alkylation of 1,3-diphenylallyl acetate leading to an almost stoichiometric product yield with modest enantiomeric excess (up to 74% ee). Rh(I)-complexes incorporating 1-3 were also prepared in situ for allylic alkylation of cinnamyl acetate as a probe for both regio- and enantioselectivities of the reaction. The reaction exhibited high regiocontrol in favor of a linear achiral isomer regardless of the ligand employed.
3, Chiral (iminophosphoranyl)ferrocenes: highly efficient ligands for rhodium- and iridium-catalyzed enantioselective hydrogenation of unfunctionalized olefins
Thanh Thien Co and Tae-Jeong Kim
Chem.Commun., 2006, 3537–3539
Abstract:
A series of chiral (iminophosphoranyl)ferrocenes (1–3) are highly efficient ligands for Rh- and Ir-catalyzed hydrogenation of a number of unfunctionalized olefins; almost perfect
enantiomeric excesses (up to 99% ee) have been achieved under mild reaction conditions.
4, 1,2-Ferrocenediylazaphosphinines: An Unusual Coordination Behavior and Application to Allylic Alkylation
Thanh Thien Co, Seung Whan Paek, Sang Chul Shim, Chan Sik Cho, and Tae-Jeong Kim
Organometallics 2003, 22, 1475 - 1482
Abstract:
The reaction of 1,2-ferrocenediylazaphosphinines (1a, R1 = H; 1b, R1 = Me; 1c, R1 = Ph) with M(CO)6 (M = Mo, W), MX(CO)5 (M = Mn, Re; X = Br, Cl), and [Pd(3-C3H5)Cl]2 shows a strong tendency to adopt an unusual chelating bidentate coordination through nitrogen and the carbonyl oxygen, yielding M(2-N,O)(CO)4 (2, M = Mo; 3, M = W), M(2-N,O)(X)(CO)3 (6, M = Mn, X = Br; 7, M = Re, X = Cl), and [Pd(2-N,O)(3-C3H5)]BF4 (after treatment with AgBF4) (8), respectively. X-ray crystallographic structure determinations of 3a (R1 = H) and 8a (R1 = H) show the formation of a five-membered metallacycle with the distance of the metal-carbonyl oxygen bond being shorter than that of the metal-nitrogen bond in both compounds. The complexes 2 and 3 further undergo oxidative addition with allyl iodide to yield the corresponding M(II) complexes of the type [M(2-N,O)( 3-C3H5)(I)(CO)2] (4, M = Mo; 5, M = W). Complexes 2-5 and 8 were employed as catalysts for nucleophilic allylic substitution of allyl acetates as a probe for both regio- and enantioselectivities of the reaction. All reactions involving unsymmetrical allyl acetates (E)-RCH=CHCH2OAc (R = Pr, Ph) led exclusively to the formation of achiral linear product (E)-RCH=CHCH2Nu regardless of the type of catalysts, the ligand, or the allyl substrate employed. One exception to the above statement is the observation that Mo- and W-based catalysts (2-5) are totally inactive toward the allylic substitution of cinnamyl acetate (R = Ph). Asymmetric allylic alkylation of a symmetrically 1,3-disubstituted substrate, PhCH=CHCH(OAc)Ph, is accomplished only by Pd-catalysts (8) with enantiomeric excesses up to 50% ee.
5, Chiral (Iminophosphoranyl)ferrocenes: A New Class of Practical Ligands for Rhodium-Catalyzed Asymmetric Hydrogenation
Thanh Thien Co, Sang Chul Shim, Chan Sik Cho, and Tae-Jeong Kim
Organometallics, 24 (20), 4824 -4831, 2005
Abstract:
A series of new chiral (iminophosphoranyl)ferrocenes, {5-C5H4-(PPh2=N-2,6-R2-C6H3)}Fe{5-C5H3-1-PPh2-2-CH(Me)(Y)} (1a, Y = NMe2, R = Me; 1b, Y = NMe2, R = iPr; 1c, Y = OMe, R = iPr), {5-C5H4-(PPh2=N-2,6-R2-C6H3)}Fe{5-C5H3-1-(PPh2=N-2,6-R2-C6H3)-2-CH(Me)(Y)} (2a, R = Me, Y = NMe2; 2b, R = iPr, Y = NMe2,; 2c, R = Me, Y = OMe), and (5-C5H5)Fe{5-C5H4-1-PR2-2-CH(Me)N=PPh3} (3a, R = Ph; 3b, R = C6H11), have been prepared from the reaction of 1,1'-bis(diphenylphosphino)-2-[(dimethylamino)ethyl]ferrocene with aryl azides (1 and 2) and the reaction of phosphine dichlorides (R3PCl2) with 1,1'-bis(diphenylphosphino)-2-(aminoethyl)ferrocene (3), respectively. They form rhodium complexes of the type [Rh(NBD)(L)]ClO4 (4-6; L = 1-3), where the ligand (L) adopts an 2(N,N) (2) or 2(P,N) mode (3), as expected. In the case of 1, a potential tridentate species, however, a chelating bidentate mode through the -CH(Me)NMe2 and -PPh2 groups is realized with the exclusion of the -P=NAr group from the coordination sphere, as confirmed by the X-ray crystal structure of [Rh(NBD)(1b)]ClO4 (4b). The new ligands (1-3) exhibit exceptionally high enantioselectivity (up to 99%) and catalytic activity in the Rh-catalyzed asymmetric hydrogenation of (E)-2-methylcinnamic acid, (Z)-2-acetamidocinnamate, and (Z)-2-acetamidoacrylate.
Bạn Châu Nguyệt Trang Thanh vừa ủng hộ Thư Viện ChemVN 2 bài báo trên ACS. Bạn Thanh hiện đang làm PhD năm cuối tại Université du Maine, France. Cám ơn bạn Trang Thanh rất nhiều.
1, Toward a Better Understanding on the Mechanism of Ortholithiation. Tuning of Selectivities in the Metalation of meta-Anisic Acid by an Appropriate Choice of Base
Thi-Huu Nguyen, Nguyet Trang Thanh Chau, Anne-Sophie Castanet, Kim Phi Phung Nguyen, and Jacques Mortier
Org. Lett., 7 (12), 2445 -2448, 2005
Abstract:
If employed in THF at 0 C, LTMP metalates meta-anisic acid at the doubly activated position. In contrast, n-BuLi/t-BuOK deprotonates position C-4 preferentially at low temperature. Functionalization at C-6 requires protection of the C-2 site beforehand. As a result of these findings, a new mechanism is proposed for the heteroatom-directed ortholithiation of aromatic compounds.
2, First General, Direct, and Regioselective Synthesis of Substituted Methoxybenzoic Acids by Ortho Metalation
Thi-Huu Nguyen, Nguyet Trang Thanh Chau, Anne-Sophie Castanet, Kim Phi Phung Nguyen, and Jacques Mortier
J. Org. Chem., 72 (9), 3419 -3429, 2007
Abstract:
New general methodology of value in aromatic chemistry based on ortho-metalation sites in o-, m-, and p-anisic acids (1-3) (Scheme 1) is described. The metalation can be selectively directed to either of the ortho positions by varying the base, metalation temperature, and exposure times. Metalation of o-anisic acid (1) with s-BuLi/TMEDA in THF at -78 C occurs exclusively in the position adjacente to the carboxylate. On the other hand, a reversal of regioselectivity is observed with n-BuLi/t-BuOK. With LTMP at 0 C, the two directors of m-anisic acid (2) function in concert to direct introduction of the metal between them while n-BuLi/t-BuOK removes preferentially the proton located ortho to the methoxy and para to the carboxylate (H-4). s-BuLi/TMEDA reacts with p-anisic acid (3) exclusively in the vicinity of the carboxylate. According to these methodologies, routes to very simple methoxybenzoic acids with a variety of functionalities that are not easily accessible by other means have been developed.
thay đổi nội dung bởi: aqhl, ngày 05-12-2008 lúc 06:55 PM.
aqhl
bluemonster
-thioxoketones. The compounds show very interesting long-range deuterium isotope effects on the thiocarbonyl carbon. The intramolecular hydrogen bonds of o-hydroxythioacetophenones are found to be slightly stronger than those of the corresponding acetophenones. The reactivity and stability of the compounds can be related to hydrogen bonding and to the presence of electron donating substituents.
Linear Mode
