In this paper, we present a system developed to identify metal nanoparticles at different orienta... more In this paper, we present a system developed to identify metal nanoparticles at different orientations, using digital image processing and analysis. The correct identification is important in nanotechnology, where it is possible to build structures for different purposes at the nanometric level. The recognition system computes automatically different characteristics such as: nanoparticle area, polygons, symmetry and molecular arrays (twins) in order to recognize different nanostructures. All these characteristics are obtained through the use of morphological, texture (co-occurrence matrix) and region analysis. Complexity issues, advantages, and results are presented and discussed.
We report the study of aurothiol nanoclusters using high-resolution electron microscopy, energy l... more We report the study of aurothiol nanoclusters using high-resolution electron microscopy, energy loss spectroscopy, X-ray photoelectron spectroscopy, Auger spectroscopy, and microscopy. It is concluded that the sulfur atoms are located on the surface of the gold nanoparticles in both (100) and (111) microfacets. The X-ray photoelectron spectroscopy data show that there is a Au-Au bond as well as a Au-S bond. Auger depth profile measurements made by sputtering of the nanoparticles corroborates that the sulfur is located on the surface of the nanoparticle. Quantitative Auger analysis indicates a ratio Au/S between approximately 1.79 and 1.98.
Hexagonal cadmium selenide nanorods 32-170 nm in length and 12-28 nm in diameter were grown by a ... more Hexagonal cadmium selenide nanorods 32-170 nm in length and 12-28 nm in diameter were grown by a solvothermal technique by reacting cadmium chloride and selenium powders in ethylenediamine at 140 degrees C. Using electron microscopy, the shape, size, and crystal structure of the nanorods were determined. A detailed microscopy analysis revealed that the nanorods grow through the coalescence of very small particles or fiberlike structures of the compound. The size, shape and strain structures in the nanorods are defined by their growth mechanism.
Small (1-5 nm) metallic nanoparticles of Pt, Au, and Au/Pt of different nominal compositions in c... more Small (1-5 nm) metallic nanoparticles of Pt, Au, and Au/Pt of different nominal compositions in colloidal form were synthesized by a chemical reduction method using polymer (PVP) as protecting agent. Analytical techniques like HREM and UV-vis spectroscopy have been used to characterize the morphology and structural properties of these small particles. Theoretical simulations based on molecular dynamical have been used to interpret the experimental structural results and analyze the macroscopic properties like stability and catalytic selectivity of these nanoparticles based on the morphology and atomic distribution in the clusters.
... CUA Postal 70–360. Delegación Coyoacán. CP 04510. México DF. b, Instituto Mexicano del Petról... more ... CUA Postal 70–360. Delegación Coyoacán. CP 04510. México DF. b, Instituto Mexicano del Petróleo. Eje Central Lázaro Cárdenas 152. San Bartolo Atepehuacan. CP 07730. México DF. c, Instituto de Cerámica y Vidrio, CSIC. Madrid, España. ...
The understanding of inorganic matter sequestration by plants in soils and water bodies is associ... more The understanding of inorganic matter sequestration by plants in soils and water bodies is associated with mechanisms of selective molecule and metal organic complex formation. We used experimental methods to understand the absorption of metal particularly by the water hyacinth. By use ...
Poly[(methacrylato)aluminum(III)] was prepared by applying g-radiation to the corresponding alumi... more Poly[(methacrylato)aluminum(III)] was prepared by applying g-radiation to the corresponding aluminum(III) methacrylate monomer. Scanning electron microscopy images show pellets of $ 500 nm for the aluminum(III) methacrylate monomer, and submicrometric fibers-made granules for the aluminum-containing polymers. X-ray photoelectron spectroscopy measurements reveal two peaks in the Al 2p core-level spectra of the monomer and of the poly[(methacrylato)aluminum(III)], which means that two different coordination modes for the Al(III) ions might be present in these compounds. Infrared and Raman spectroscopy studies confirmed that the structure for this novel co-ordination polymer consists of hexa-coordinated Al(III) ions linked by the carboxylate groups of methacrylate ligands, along with hydroxyl groups and coordinated water, in a combination of monodentate and bridging bidentate coordination modes. Hence, combination of spectroscopic methods is a helpful tool to get valuable information on the structure of nonmacrocrystalline coordination polymers.
The possibility to produce hydroxylapatite, for biomaterials applications, from different kind of... more The possibility to produce hydroxylapatite, for biomaterials applications, from different kind of precursors has motivated many efforts. In this work we have analyzed several common precursors, mainly calcium based systems. Quantum mechanics calculations, by density-functional theory and semi-empirical approximations, were used to study the characteristic crystals and the particular behavior of the PO 3À 4 molecules interaction, both by the electronic distributions in order to give a new possibility for the study of these materials and for improving new synthesis methods. High resolution electron microscopy images are also calculated, by a multislice method, to confirm our approaches and also to show a easy way to distinguish this materials experimentally as is proved in this work. (J.A. Ascencio). 0927-0256/02/$ -see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 7 -0 2 5 6 ( 0 2 ) 0 0 2 4 3 -4
Structural, optical, and chemical properties of the WO x -ZrO 2 nanometric system were investigat... more Structural, optical, and chemical properties of the WO x -ZrO 2 nanometric system were investigated using Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and UV-visible diffuse reflectance. From diffuse reflectance spectroscopy, the absorption profile of the species in which WO x was present (layers and small clusters) on the surface of ZrO 2 crystals was obtained. This study shows three main energetic regions for optical absorption. As tungsten (W) concentration diminished, which corresponded with a decrease in WO x layer thickness, the absorption edge showed a blue shift, and the band gap increased. The analysis of such behaviors suggests that they are due to quantum confinement produced by 0-or 1-dimensional WO x species. Local chemical analyses and HRTEM observations allowed determination of the presence of an irregular thin coating, a small cluster, and a crystalline thin film formation over the ZrO 2 for samples with loadings of 6, 10, and 20 wt % of W, respectively. The results obtained from different techniques were used to propose a chemical approach to the relationship between structure and electronic behavior of the active surface as a function of W concentration.
The complex(153)Sm(III)DTPA-bis-biotin was prepared with a 99% radiochemical purity and a specifi... more The complex(153)Sm(III)DTPA-bis-biotin was prepared with a 99% radiochemical purity and a specific activity of 370 MBq/mg employing a molar ratio of DTPA-bis-biotin/Sm from 2 to 4 at pH 8.0. In vitro studies demonstrated that the complex is stable after dilution in saline and in human serum. Avidity of labeled biotin for avidin was not affected by the labeling procedure. Pharmacokinetic data of (153)Sm(III)DTPA-bis-biotin in normal mice showed that blood clearance is biexponential during the time interval from 0 to 24 h and that 3 h postinjection 92 +/- 4.32% of the dose is eliminated in the urine. To have further evidence which could sustain that (153)Sm(III)DTPA-bis-biotin is stable in solution as a real coordination complex, (152)Sm(III)DTPA-bis-biotin was obtained in macroscopic quantities and its characterization was done by IR, TGA, and conductivity measurements. The results indicated that the complex was chemically pure, where the Sm(3+) ion is neutralized by three carboxylate groups of the DTPA-bis-biotin ligand and coordinated to it. Using the Force Field method followed by ab initio calculations, the DTPA-bis-biotin and the Sm(III)DTPA-bis-biotin molecules were done. Accordingly, the coordination sphere of Sm(III) was totally satisfied with nitrogen and oxygen donors; the best coordination number was 9. The conformation geometry of both compounds is presented.
... Ben-David, Y. Lerech, J. Deutscher, JM Penisson, A. Bourret, R. Kofman, and P. Cheyssac (1997... more ... Ben-David, Y. Lerech, J. Deutscher, JM Penisson, A. Bourret, R. Kofman, and P. Cheyssac (1997). Phys. Rev. Lett. 78, 2585. 7. M. Mitone, Y. Tanishiro, and K. Takayanaji (1989). Z. Phys. DIZ 45. 196 Ascencio et al. Page 9. 8. JA Ascencio, M. Perez, and M. Jose-Yacaman (2001 ...
A constant rate of evaporation (1 ˚A/s) was maintained through-out the evaporation of the ZnPc th... more A constant rate of evaporation (1 ˚A/s) was maintained through-out the evaporation of the ZnPc thin films. A rotary drive was employed to obtain uniform thickness during the evaporation. Thicknesses of the films were monitored by a quartz-crystal thickness monitor and were cross verified ...
We characterized the structure of tungstated zirconia (WO xZrO 2) by combining X-ray diffraction... more We characterized the structure of tungstated zirconia (WO xZrO 2) by combining X-ray diffraction, Raman spectroscopy and High Resolution Electron Microscopy (HREM) together with molecular simulations. Our results indicate that the structure of this material consists ...
1 Universidad Popular Autónoma del Estado de Puebla, 21 sur 1103, Col. Santiago, Puebla, Pue., Mé... more 1 Universidad Popular Autónoma del Estado de Puebla, 21 sur 1103, Col. Santiago, Puebla, Pue., México 2 Instituto de Metalurgia, Universidad Michoacana de San Nicolas de Hidalgo, PO Box 52-B 58000, Morelia, Mich., México 3 Programa de Ingenierıa Molecular, Instituto ...
In this paper, we present a system developed to identify metal nanoparticles at different orienta... more In this paper, we present a system developed to identify metal nanoparticles at different orientations, using digital image processing and analysis. The correct identification is important in nanotechnology, where it is possible to build structures for different purposes at the nanometric level. The recognition system computes automatically different characteristics such as: nanoparticle area, polygons, symmetry and molecular arrays (twins) in order to recognize different nanostructures. All these characteristics are obtained through the use of morphological, texture (co-occurrence matrix) and region analysis. Complexity issues, advantages, and results are presented and discussed.
We report the study of aurothiol nanoclusters using high-resolution electron microscopy, energy l... more We report the study of aurothiol nanoclusters using high-resolution electron microscopy, energy loss spectroscopy, X-ray photoelectron spectroscopy, Auger spectroscopy, and microscopy. It is concluded that the sulfur atoms are located on the surface of the gold nanoparticles in both (100) and (111) microfacets. The X-ray photoelectron spectroscopy data show that there is a Au-Au bond as well as a Au-S bond. Auger depth profile measurements made by sputtering of the nanoparticles corroborates that the sulfur is located on the surface of the nanoparticle. Quantitative Auger analysis indicates a ratio Au/S between approximately 1.79 and 1.98.
Hexagonal cadmium selenide nanorods 32-170 nm in length and 12-28 nm in diameter were grown by a ... more Hexagonal cadmium selenide nanorods 32-170 nm in length and 12-28 nm in diameter were grown by a solvothermal technique by reacting cadmium chloride and selenium powders in ethylenediamine at 140 degrees C. Using electron microscopy, the shape, size, and crystal structure of the nanorods were determined. A detailed microscopy analysis revealed that the nanorods grow through the coalescence of very small particles or fiberlike structures of the compound. The size, shape and strain structures in the nanorods are defined by their growth mechanism.
Small (1-5 nm) metallic nanoparticles of Pt, Au, and Au/Pt of different nominal compositions in c... more Small (1-5 nm) metallic nanoparticles of Pt, Au, and Au/Pt of different nominal compositions in colloidal form were synthesized by a chemical reduction method using polymer (PVP) as protecting agent. Analytical techniques like HREM and UV-vis spectroscopy have been used to characterize the morphology and structural properties of these small particles. Theoretical simulations based on molecular dynamical have been used to interpret the experimental structural results and analyze the macroscopic properties like stability and catalytic selectivity of these nanoparticles based on the morphology and atomic distribution in the clusters.
... CUA Postal 70–360. Delegación Coyoacán. CP 04510. México DF. b, Instituto Mexicano del Petról... more ... CUA Postal 70–360. Delegación Coyoacán. CP 04510. México DF. b, Instituto Mexicano del Petróleo. Eje Central Lázaro Cárdenas 152. San Bartolo Atepehuacan. CP 07730. México DF. c, Instituto de Cerámica y Vidrio, CSIC. Madrid, España. ...
The understanding of inorganic matter sequestration by plants in soils and water bodies is associ... more The understanding of inorganic matter sequestration by plants in soils and water bodies is associated with mechanisms of selective molecule and metal organic complex formation. We used experimental methods to understand the absorption of metal particularly by the water hyacinth. By use ...
Poly[(methacrylato)aluminum(III)] was prepared by applying g-radiation to the corresponding alumi... more Poly[(methacrylato)aluminum(III)] was prepared by applying g-radiation to the corresponding aluminum(III) methacrylate monomer. Scanning electron microscopy images show pellets of $ 500 nm for the aluminum(III) methacrylate monomer, and submicrometric fibers-made granules for the aluminum-containing polymers. X-ray photoelectron spectroscopy measurements reveal two peaks in the Al 2p core-level spectra of the monomer and of the poly[(methacrylato)aluminum(III)], which means that two different coordination modes for the Al(III) ions might be present in these compounds. Infrared and Raman spectroscopy studies confirmed that the structure for this novel co-ordination polymer consists of hexa-coordinated Al(III) ions linked by the carboxylate groups of methacrylate ligands, along with hydroxyl groups and coordinated water, in a combination of monodentate and bridging bidentate coordination modes. Hence, combination of spectroscopic methods is a helpful tool to get valuable information on the structure of nonmacrocrystalline coordination polymers.
The possibility to produce hydroxylapatite, for biomaterials applications, from different kind of... more The possibility to produce hydroxylapatite, for biomaterials applications, from different kind of precursors has motivated many efforts. In this work we have analyzed several common precursors, mainly calcium based systems. Quantum mechanics calculations, by density-functional theory and semi-empirical approximations, were used to study the characteristic crystals and the particular behavior of the PO 3À 4 molecules interaction, both by the electronic distributions in order to give a new possibility for the study of these materials and for improving new synthesis methods. High resolution electron microscopy images are also calculated, by a multislice method, to confirm our approaches and also to show a easy way to distinguish this materials experimentally as is proved in this work. (J.A. Ascencio). 0927-0256/02/$ -see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 7 -0 2 5 6 ( 0 2 ) 0 0 2 4 3 -4
Structural, optical, and chemical properties of the WO x -ZrO 2 nanometric system were investigat... more Structural, optical, and chemical properties of the WO x -ZrO 2 nanometric system were investigated using Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and UV-visible diffuse reflectance. From diffuse reflectance spectroscopy, the absorption profile of the species in which WO x was present (layers and small clusters) on the surface of ZrO 2 crystals was obtained. This study shows three main energetic regions for optical absorption. As tungsten (W) concentration diminished, which corresponded with a decrease in WO x layer thickness, the absorption edge showed a blue shift, and the band gap increased. The analysis of such behaviors suggests that they are due to quantum confinement produced by 0-or 1-dimensional WO x species. Local chemical analyses and HRTEM observations allowed determination of the presence of an irregular thin coating, a small cluster, and a crystalline thin film formation over the ZrO 2 for samples with loadings of 6, 10, and 20 wt % of W, respectively. The results obtained from different techniques were used to propose a chemical approach to the relationship between structure and electronic behavior of the active surface as a function of W concentration.
The complex(153)Sm(III)DTPA-bis-biotin was prepared with a 99% radiochemical purity and a specifi... more The complex(153)Sm(III)DTPA-bis-biotin was prepared with a 99% radiochemical purity and a specific activity of 370 MBq/mg employing a molar ratio of DTPA-bis-biotin/Sm from 2 to 4 at pH 8.0. In vitro studies demonstrated that the complex is stable after dilution in saline and in human serum. Avidity of labeled biotin for avidin was not affected by the labeling procedure. Pharmacokinetic data of (153)Sm(III)DTPA-bis-biotin in normal mice showed that blood clearance is biexponential during the time interval from 0 to 24 h and that 3 h postinjection 92 +/- 4.32% of the dose is eliminated in the urine. To have further evidence which could sustain that (153)Sm(III)DTPA-bis-biotin is stable in solution as a real coordination complex, (152)Sm(III)DTPA-bis-biotin was obtained in macroscopic quantities and its characterization was done by IR, TGA, and conductivity measurements. The results indicated that the complex was chemically pure, where the Sm(3+) ion is neutralized by three carboxylate groups of the DTPA-bis-biotin ligand and coordinated to it. Using the Force Field method followed by ab initio calculations, the DTPA-bis-biotin and the Sm(III)DTPA-bis-biotin molecules were done. Accordingly, the coordination sphere of Sm(III) was totally satisfied with nitrogen and oxygen donors; the best coordination number was 9. The conformation geometry of both compounds is presented.
... Ben-David, Y. Lerech, J. Deutscher, JM Penisson, A. Bourret, R. Kofman, and P. Cheyssac (1997... more ... Ben-David, Y. Lerech, J. Deutscher, JM Penisson, A. Bourret, R. Kofman, and P. Cheyssac (1997). Phys. Rev. Lett. 78, 2585. 7. M. Mitone, Y. Tanishiro, and K. Takayanaji (1989). Z. Phys. DIZ 45. 196 Ascencio et al. Page 9. 8. JA Ascencio, M. Perez, and M. Jose-Yacaman (2001 ...
A constant rate of evaporation (1 ˚A/s) was maintained through-out the evaporation of the ZnPc th... more A constant rate of evaporation (1 ˚A/s) was maintained through-out the evaporation of the ZnPc thin films. A rotary drive was employed to obtain uniform thickness during the evaporation. Thicknesses of the films were monitored by a quartz-crystal thickness monitor and were cross verified ...
We characterized the structure of tungstated zirconia (WO xZrO 2) by combining X-ray diffraction... more We characterized the structure of tungstated zirconia (WO xZrO 2) by combining X-ray diffraction, Raman spectroscopy and High Resolution Electron Microscopy (HREM) together with molecular simulations. Our results indicate that the structure of this material consists ...
1 Universidad Popular Autónoma del Estado de Puebla, 21 sur 1103, Col. Santiago, Puebla, Pue., Mé... more 1 Universidad Popular Autónoma del Estado de Puebla, 21 sur 1103, Col. Santiago, Puebla, Pue., México 2 Instituto de Metalurgia, Universidad Michoacana de San Nicolas de Hidalgo, PO Box 52-B 58000, Morelia, Mich., México 3 Programa de Ingenierıa Molecular, Instituto ...
Uploads
Papers by jorge ascencio