2016 |
Aliaga, A E; Leyton, P; Clavijo, E; Campos-Vallette, M Fluorescence and Surface-Enhanced Vibrational Spectroscopies of Lawsone and Plumbagin Artículo de revista Spectroscopy Letters, 49 (5), pp. 326-335, 2016, ISSN: 0038-7010. Resumen | Enlaces | BibTeX | Etiquetas: behavior, calculations, enhanced fluorescence, infrared-absorption, lawsone, nanoparticles, plumbagin, quinones raman raman-scattering, reduction, scattering, selection, sers, silver spectrum, surface theoretical @article{RN318, title = {Fluorescence and Surface-Enhanced Vibrational Spectroscopies of Lawsone and Plumbagin}, author = { A.E. Aliaga and P. Leyton and E. Clavijo and M. Campos-Vallette}, url = {/brokenurl#<Go to ISI>://WOS:000405754400002}, doi = {10.1080/00387010.2016.1146772}, issn = {0038-7010}, year = {2016}, date = {2016-01-01}, journal = {Spectroscopy Letters}, volume = {49}, number = {5}, pages = {326-335}, abstract = {The natural dyes lawsone and plumbagin (1,4-naphthoquinones) were studied by using fluorescence, Raman, infrared (IR), surface-enhanced Raman scattering (SERS), and surface-enhanced IR absorption. From the absorption spectrum, it was possible to infer that the enol-lawsone tautomer concentration decreases in silver colloidal solution. Plumbagin dimers, both in water and in silver colloidal solution, were identified from the fluorescence band profile and surface-SERS spectrum. The SERS spectrum of lawsone was obtained by using silver colloidal solution after 12-hour settle; the keto and enol lawsone silver colloid interaction occurs. The assignment of Raman and IR bands of both dyes was calculated with density functional theory calculations. Only a monomeric structure of lawsone interacting with a silver cluster model was predicted. The monomer adopts a nearly coplanar orientation onto the silver surface; the shortest distance is 3.2 angstrom, suggesting an electrostatic interaction.}, keywords = {behavior, calculations, enhanced fluorescence, infrared-absorption, lawsone, nanoparticles, plumbagin, quinones raman raman-scattering, reduction, scattering, selection, sers, silver spectrum, surface theoretical}, pubstate = {published}, tppubtype = {article} } The natural dyes lawsone and plumbagin (1,4-naphthoquinones) were studied by using fluorescence, Raman, infrared (IR), surface-enhanced Raman scattering (SERS), and surface-enhanced IR absorption. From the absorption spectrum, it was possible to infer that the enol-lawsone tautomer concentration decreases in silver colloidal solution. Plumbagin dimers, both in water and in silver colloidal solution, were identified from the fluorescence band profile and surface-SERS spectrum. The SERS spectrum of lawsone was obtained by using silver colloidal solution after 12-hour settle; the keto and enol lawsone silver colloid interaction occurs. The assignment of Raman and IR bands of both dyes was calculated with density functional theory calculations. Only a monomeric structure of lawsone interacting with a silver cluster model was predicted. The monomer adopts a nearly coplanar orientation onto the silver surface; the shortest distance is 3.2 angstrom, suggesting an electrostatic interaction. |
Gallardo-Fuentes, S; Contreras, R; Isaacs, M; Honores, J; Quezada, D; Landaeta, E; Ormazabal-Toledo, R On the Mechanism of Co2 Electro-Cycloaddition to Propylene Oxides Artículo de revista Journal of Co2 Utilization, 16 , pp. 114-120, 2016, ISSN: 2212-9820. Resumen | Enlaces | BibTeX | Etiquetas: atmospheric calculations, capture carbonate catalyst co2 co2, complexes, conversion, cyclic density dioxide, efficient electro-cycloaddition, electrochemical functional high-capacity, ionic liquids, mechanism, reaction recovery, reduction, salen synthesis, system @article{RN327, title = {On the Mechanism of Co2 Electro-Cycloaddition to Propylene Oxides}, author = { S. Gallardo-Fuentes and R. Contreras and M. Isaacs and J. Honores and D. Quezada and E. Landaeta and R. Ormazabal-Toledo}, url = {/brokenurl#<Go to ISI>://WOS:000389089200013}, doi = {10.1016/j.jcou.2016.06.007}, issn = {2212-9820}, year = {2016}, date = {2016-01-01}, journal = {Journal of Co2 Utilization}, volume = {16}, pages = {114-120}, publisher = {2016 Elsevier Ltd.}, abstract = {We herein present a systematic study on the mechanism of CO2 electro-cycloaddition to propylene oxide, using both experimental and theoretical procedures. The study considers the analysis of mild and sustainable conditions to obtain cyclic carbonates from CO2 recycling. Within the electrochemical approach, the application of an overpotential in the reaction enhances the reaction yield significantly with respect to the thermal pathway. The quantum-mechanical approach provides relevant information about the reaction mechanism. Specifically, the use of the Lewis acid catalyst Mg2+ in the presence of the [C(4)C(1)Im][Br] ionic liquid provides the best condition for the electro-synthesis. The theoretical predictions were confirmed by a new set of experiments.}, keywords = {atmospheric calculations, capture carbonate catalyst co2 co2, complexes, conversion, cyclic density dioxide, efficient electro-cycloaddition, electrochemical functional high-capacity, ionic liquids, mechanism, reaction recovery, reduction, salen synthesis, system}, pubstate = {published}, tppubtype = {article} } We herein present a systematic study on the mechanism of CO2 electro-cycloaddition to propylene oxide, using both experimental and theoretical procedures. The study considers the analysis of mild and sustainable conditions to obtain cyclic carbonates from CO2 recycling. Within the electrochemical approach, the application of an overpotential in the reaction enhances the reaction yield significantly with respect to the thermal pathway. The quantum-mechanical approach provides relevant information about the reaction mechanism. Specifically, the use of the Lewis acid catalyst Mg2+ in the presence of the [C(4)C(1)Im][Br] ionic liquid provides the best condition for the electro-synthesis. The theoretical predictions were confirmed by a new set of experiments. |
2015 |
Aliaga, J A; Araya, J F; Lozano, H; Benavente, E; Alonso-Nunez, G; González, G An Easy One-Pot Solvothermal Synthesis of Poorly Crystalline Solid Res2/C Microspheres Artículo de revista Materials Chemistry and Physics, 151 , pp. 372-377, 2015, ISSN: 0254-0584. Resumen | Enlaces | BibTeX | Etiquetas: amorphous carbon chalcogenides, composite growth-mechanism, material, nanoparticles, reduction, rhenium sulfide, technetium, temperature @article{aliaga2015onepot, title = {An Easy One-Pot Solvothermal Synthesis of Poorly Crystalline Solid Res2/C Microspheres}, author = { J.A. Aliaga and J.F. Araya and H. Lozano and E. Benavente and G. Alonso-Nunez and G. Gonz\'{a}lez}, url = {/brokenurl#<Go to ISI>://WOS:000348263600051}, doi = {10.1016/j.matchemphys.2014.12.012}, issn = {0254-0584}, year = {2015}, date = {2015-01-01}, journal = {Materials Chemistry and Physics}, volume = {151}, pages = {372-377}, publisher = {2014 Elsevier B.V.}, abstract = {Dense microspheres consisting of poorly crystalline ReS2 embedded in carbon were synthesized with a high yield via a facile one-pot solvothermal route, by reacting dirhenium decacarbonyl, elemental sulfur and an aromatic solvent (benzene, toluene or p-xylene) for 24 h at 180 degrees C. X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Fourier transform infrared spectroscopy (Fr-IR) techniques were used to characterize the samples. The resulting microspheres were dense, with average diameters between 0.79 and 1.40 mu m, had smooth surfaces and were constructed of ReS2 sheet-like structures with 4.5-9.8 wt % of structural amorphous carbon, which is retained as a textural stabilizer after calcination at 800 degrees C. The synthesis was repeated using isopropanol and cyclohexane, whose products were agglomerated grains and botryoidal quasi-spherical particles, respectively. A possible formation mechanism of ReS2/C microspheres was preliminarily presented, in order to clarify the mechanistic differences between the rhenium carbonyl and other transition metal carbonyls used in similar syntheses.}, keywords = {amorphous carbon chalcogenides, composite growth-mechanism, material, nanoparticles, reduction, rhenium sulfide, technetium, temperature}, pubstate = {published}, tppubtype = {article} } Dense microspheres consisting of poorly crystalline ReS2 embedded in carbon were synthesized with a high yield via a facile one-pot solvothermal route, by reacting dirhenium decacarbonyl, elemental sulfur and an aromatic solvent (benzene, toluene or p-xylene) for 24 h at 180 degrees C. X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Fourier transform infrared spectroscopy (Fr-IR) techniques were used to characterize the samples. The resulting microspheres were dense, with average diameters between 0.79 and 1.40 mu m, had smooth surfaces and were constructed of ReS2 sheet-like structures with 4.5-9.8 wt % of structural amorphous carbon, which is retained as a textural stabilizer after calcination at 800 degrees C. The synthesis was repeated using isopropanol and cyclohexane, whose products were agglomerated grains and botryoidal quasi-spherical particles, respectively. A possible formation mechanism of ReS2/C microspheres was preliminarily presented, in order to clarify the mechanistic differences between the rhenium carbonyl and other transition metal carbonyls used in similar syntheses. |
2013 |
Campos, C; Munoz, M; Barrientos-Poblete, L; Lang, E; Jara, P; Sobrados, I; Yutronic, N Adhesion of Gold and Silver Nanoparticles onto Urea-Alkylamine Inclusion Compounds Artículo de revista Journal of Inclusion Phenomena and Macrocyclic Chemistry, 75 (1-2), pp. 165-173, 2013, ISSN: 1388-3127. Resumen | Enlaces | BibTeX | Etiquetas: alpha-cyclodextrin, amine aspects, compounds, dynamics gold guests, inclusion molecules, nanoparticle, nanoparticles, reduction, silver structural temperature, thiourea, urea x-ray-diffraction @article{RN137, title = {Adhesion of Gold and Silver Nanoparticles onto Urea-Alkylamine Inclusion Compounds}, author = { C. Campos and M. Munoz and L. Barrientos-Poblete and E. Lang and P. Jara and I. Sobrados and N. Yutronic}, url = {/brokenurl#<Go to ISI>://WOS:000314898300018}, doi = {10.1007/s10847-012-0157-1}, issn = {1388-3127}, year = {2013}, date = {2013-01-01}, journal = {Journal of Inclusion Phenomena and Macrocyclic Chemistry}, volume = {75}, number = {1-2}, pages = {165-173}, abstract = {We report the synthesis and characterization of a new series of urea inclusion compounds containing primary alkylamine (octyl, decyl and dodecyl) as guests, as well as the deposition of gold and silver nanoparticles onto the crystalline surface of these complexes. X-ray diffraction confirms the inclusion process of the amine in the urea cavities. The structures determined for the three complexes correspond to a hexagonal channel structure with space group P6(1)22. Alkylamine-urea stoichiometric ratios in all cases satisfy the relationship 1:3n (n = 2 for octylamine and 3 for decylamine and dodecylamine), determined by elemental analysis. The deposition of gold and silver nanoparticles by the magnetron sputtering technique onto microcrystals of the complexes was analyzed by Diffuse Reflectance Spectroscopy, showing characteristic surface plasmon resonance for metal nanoparticles. Transmission electron microscopy demonstrates the presence of metal nanoparticles (MNPs) in a size range between 5 and 60 nm for gold and between 5 and 20 nm for silver, and furthermore, in some cases it shows vestiges of a hexagonal arrangement of the MNPs. X-ray diffraction and IR measurements demonstrate that the basic structure of the matrix remains unchanged after the MNPs adhesion. IR also shows increased broadening and intensity of the characteristic NH2 bending frequencies (1,597 cm(-1)) when the MNPs interact with the inclusion compounds. We conclude that the interactions between the inclusion compounds and metal nanoparticles occurs mainly through the amino groups of the guest molecules that can emerge from the entrance of the inclusion compound cavities attracted by the metallic nanoparticles, in opposition to the restoring van der Waals interactions present inside channels, which increase with increasing chain length of the guest molecules., Schematic representation of urea inclusion compounds containing primary alkylamine (octyl, decyl and dodecyl) as guests and the deposition of gold and silver nanoparticles onto the crystalline surface of these complexes.}, keywords = {alpha-cyclodextrin, amine aspects, compounds, dynamics gold guests, inclusion molecules, nanoparticle, nanoparticles, reduction, silver structural temperature, thiourea, urea x-ray-diffraction}, pubstate = {published}, tppubtype = {article} } We report the synthesis and characterization of a new series of urea inclusion compounds containing primary alkylamine (octyl, decyl and dodecyl) as guests, as well as the deposition of gold and silver nanoparticles onto the crystalline surface of these complexes. X-ray diffraction confirms the inclusion process of the amine in the urea cavities. The structures determined for the three complexes correspond to a hexagonal channel structure with space group P6(1)22. Alkylamine-urea stoichiometric ratios in all cases satisfy the relationship 1:3n (n = 2 for octylamine and 3 for decylamine and dodecylamine), determined by elemental analysis. The deposition of gold and silver nanoparticles by the magnetron sputtering technique onto microcrystals of the complexes was analyzed by Diffuse Reflectance Spectroscopy, showing characteristic surface plasmon resonance for metal nanoparticles. Transmission electron microscopy demonstrates the presence of metal nanoparticles (MNPs) in a size range between 5 and 60 nm for gold and between 5 and 20 nm for silver, and furthermore, in some cases it shows vestiges of a hexagonal arrangement of the MNPs. X-ray diffraction and IR measurements demonstrate that the basic structure of the matrix remains unchanged after the MNPs adhesion. IR also shows increased broadening and intensity of the characteristic NH2 bending frequencies (1,597 cm(-1)) when the MNPs interact with the inclusion compounds. We conclude that the interactions between the inclusion compounds and metal nanoparticles occurs mainly through the amino groups of the guest molecules that can emerge from the entrance of the inclusion compound cavities attracted by the metallic nanoparticles, in opposition to the restoring van der Waals interactions present inside channels, which increase with increasing chain length of the guest molecules., Schematic representation of urea inclusion compounds containing primary alkylamine (octyl, decyl and dodecyl) as guests and the deposition of gold and silver nanoparticles onto the crystalline surface of these complexes. |
Benavente, E; Lozano, H; González, G Fabrication of Copper Nanoparticles: Advances in Synthesis, Morphology Control, and Chemical Stability Artículo de revista Recent Patents on Nanotechnology, 7 (2), pp. 108-132, 2013, ISSN: 1872-2105. Resumen | Enlaces | BibTeX | Etiquetas: assemblies, colloidal copper copper, cu enhanced fabrication irradiation, laser metal micelles, nanocopper, nanoparticle nanoparticles, nanosized particles, polyol process, raman-scattering, reduction, reverse size synthesis, thermal @article{RN133, title = {Fabrication of Copper Nanoparticles: Advances in Synthesis, Morphology Control, and Chemical Stability}, author = { E. Benavente and H. Lozano and G. Gonz\'{a}lez}, url = {/brokenurl#<Go to ISI>://WOS:000327780100002}, doi = {10.2174/1872210511307020002}, issn = {1872-2105}, year = {2013}, date = {2013-01-01}, journal = {Recent Patents on Nanotechnology}, volume = {7}, number = {2}, pages = {108-132}, abstract = {Metal nanoparticles have attracted great interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Although most pioneering advancements refers to gold and silver, more recently there is growing interest in nanoparticles of copper, mostly due to its relatively low cost, which could allow the use of these small metal objects in large-scale nanotechnology applications, for example, antiseptics materials and metallic inks. However, the manufacture of copper nanoparticles stable in air with controlled size and shape has been a major challenge because of the relatively high reactivity of this element. Great efforts in getting the basic knowledge and synthesis know-how has gone into finding better ways to produce particles protected against oxidation and self-aggregation under normal conditions. In this review article, we briefly discuss a number of selected papers and recent patents on procedures and other issues related to the fabrication of copper nanoparticles.}, keywords = {assemblies, colloidal copper copper, cu enhanced fabrication irradiation, laser metal micelles, nanocopper, nanoparticle nanoparticles, nanosized particles, polyol process, raman-scattering, reduction, reverse size synthesis, thermal}, pubstate = {published}, tppubtype = {article} } Metal nanoparticles have attracted great interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Although most pioneering advancements refers to gold and silver, more recently there is growing interest in nanoparticles of copper, mostly due to its relatively low cost, which could allow the use of these small metal objects in large-scale nanotechnology applications, for example, antiseptics materials and metallic inks. However, the manufacture of copper nanoparticles stable in air with controlled size and shape has been a major challenge because of the relatively high reactivity of this element. Great efforts in getting the basic knowledge and synthesis know-how has gone into finding better ways to produce particles protected against oxidation and self-aggregation under normal conditions. In this review article, we briefly discuss a number of selected papers and recent patents on procedures and other issues related to the fabrication of copper nanoparticles. |
2012 |
Aguilera-Venegas, B; Olea-Azar, C; Aran, V J; Maya, J D; Kemmerling, U; Speisky, H; Mendizabal, F Electrochemical, Esr and Theoretical Insights into the Free Radical Generation by 1,1 '-Hydrocarbylenebisindazoles and Its Evaluation as Potential Bio-Active Compounds Artículo de revista International Journal of Electrochemical Science, 7 (7), pp. 5837-5863, 2012, ISSN: 1452-3981. Resumen | Enlaces | BibTeX | Etiquetas: antiprotozoal biological bisnitroindazoles, carbonyl chagas-disease control, density-functional derivatives, electron-spin-resonance, evaluation, free metabolism microsomal oxidative production, radical, reductase, reduction, ros spin stress, theory, thiol trapping, trypanosoma-cruzi, trypanothione @article{RN425, title = {Electrochemical, Esr and Theoretical Insights into the Free Radical Generation by 1,1 '-Hydrocarbylenebisindazoles and Its Evaluation as Potential Bio-Active Compounds}, author = { B. Aguilera-Venegas and C. Olea-Azar and V.J. Aran and J.D. Maya and U. Kemmerling and H. Speisky and F. Mendizabal}, url = {/brokenurl#<Go to ISI>://WOS:000306399700009}, issn = {1452-3981}, year = {2012}, date = {2012-01-01}, journal = {International Journal of Electrochemical Science}, volume = {7}, number = {7}, pages = {5837-5863}, abstract = {A comprehensive multidisciplinary study is conducted here in order to assess the electrochemical behavior of a series of 1,1'-hydrocarbylenebisindazoles derivatives and its potential use as anti-T.cruzi drugs. At first, we have determined the electrochemical reduction mechanisms of this family by cyclic voltammetry (CV) studies, from which three kind of reduction mechanisms -depending on the substituent at positions 3 and 3'-were established, but sharing a first common step corresponding to the generation of a nitro anion radical, which was corroborated by ESR spectroscopy, showing a comparable hyperfine splitting pattern and a strong influence on the ESR spectral linewidths due to the radical-solvent interactions. Furthermore, in order to give a rational description about the electrochemical and ESR results, open- and closed-shell structures of bisindasoles were subjected to theoretical estimations at different levels of theory. For open-shell structures, the hyperfine splitting patterns were confirmed while for the closed-shell systems case, clear evidence about the electrochemical reactivity -in terms of their frontiers orbitals-were obtained. To conclude, all these compounds were assayed as growth inhibitors against T. cruzi, from which some degree of activity was observed for this family, highlighting a compound almost as active as the reference drug. Finally, in order to get some information about the potential action mechanisms involved in the trypanocidal activity, molecular modeling and spin trapping studies were also done.}, keywords = {antiprotozoal biological bisnitroindazoles, carbonyl chagas-disease control, density-functional derivatives, electron-spin-resonance, evaluation, free metabolism microsomal oxidative production, radical, reductase, reduction, ros spin stress, theory, thiol trapping, trypanosoma-cruzi, trypanothione}, pubstate = {published}, tppubtype = {article} } A comprehensive multidisciplinary study is conducted here in order to assess the electrochemical behavior of a series of 1,1'-hydrocarbylenebisindazoles derivatives and its potential use as anti-T.cruzi drugs. At first, we have determined the electrochemical reduction mechanisms of this family by cyclic voltammetry (CV) studies, from which three kind of reduction mechanisms -depending on the substituent at positions 3 and 3'-were established, but sharing a first common step corresponding to the generation of a nitro anion radical, which was corroborated by ESR spectroscopy, showing a comparable hyperfine splitting pattern and a strong influence on the ESR spectral linewidths due to the radical-solvent interactions. Furthermore, in order to give a rational description about the electrochemical and ESR results, open- and closed-shell structures of bisindasoles were subjected to theoretical estimations at different levels of theory. For open-shell structures, the hyperfine splitting patterns were confirmed while for the closed-shell systems case, clear evidence about the electrochemical reactivity -in terms of their frontiers orbitals-were obtained. To conclude, all these compounds were assayed as growth inhibitors against T. cruzi, from which some degree of activity was observed for this family, highlighting a compound almost as active as the reference drug. Finally, in order to get some information about the potential action mechanisms involved in the trypanocidal activity, molecular modeling and spin trapping studies were also done. |
Ponce, I; Silva, J F; Onate, R; Rezende, M C; Paez, M; Zagal, J H; Pavez, J; Mendizabal, F; Miranda-Rojas, S; Munoz-Castro, A; Arratia-Perez, R Journal of Physical Chemistry C, 116 (29), pp. 15329-15341, 2012, ISSN: 1932-7447. Resumen | Enlaces | BibTeX | Etiquetas: activity, alkylation, density-functional electrocatalytic electronic-structure, electroreductive hydrogen-peroxide, iron materials, metal-complexes molecular oxygen phthalocyanine, reduction, scanning-tunneling-microscopy, theory @article{RN83, title = {Enhancement of the Catalytic Activity of Fe Phthalocyanine for the Reduction of O-2 Anchored to Au(111) Via Conjugated Self-Assembled Mono Layers of Aromatic Thiols as Compared to Cu Phthalocyanine}, author = { I. Ponce and J.F. Silva and R. Onate and M.C. Rezende and M. Paez and J.H. Zagal and J. Pavez and F. Mendizabal and S. Miranda-Rojas and A. Munoz-Castro and R. Arratia-Perez}, url = {/brokenurl#<Go to ISI>://WOS:000306725200017}, doi = {10.1021/jp301093q}, issn = {1932-7447}, year = {2012}, date = {2012-01-01}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {29}, pages = {15329-15341}, abstract = {We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (Fe Pc) and copper phthalocyanine (Cu Pc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reduction of O-2 in aqueous solutions and compared to that of bare gold and with gold coated directly with preadsorbed MPc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by MPc. STM images reveal that iron phthalocyanine molecules are chemically anchored to 4-aminothiophenol organic monolayers, probably having an "umbrella" type orientation with regards to the surface. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O-2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. The modified electrode obtained by simple adsorption of FePc directly to the Au(111) surface still promotes the 4-electron reduction process, but it shows a lower activity than the electrodes involving SAMs with FePc molecules positioned at the outmost portion of the self-assembled monolayers. The activity of the electrodes increases as follow: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc with the highest activity when FePc molecules are more separated from the Au surface. In contrast, the less active CuPc shows almost the same activity in all three configurations. Theoretical calculations suggest the importance of the back-bonding into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands.}, keywords = {activity, alkylation, density-functional electrocatalytic electronic-structure, electroreductive hydrogen-peroxide, iron materials, metal-complexes molecular oxygen phthalocyanine, reduction, scanning-tunneling-microscopy, theory}, pubstate = {published}, tppubtype = {article} } We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (Fe Pc) and copper phthalocyanine (Cu Pc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reduction of O-2 in aqueous solutions and compared to that of bare gold and with gold coated directly with preadsorbed MPc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by MPc. STM images reveal that iron phthalocyanine molecules are chemically anchored to 4-aminothiophenol organic monolayers, probably having an "umbrella" type orientation with regards to the surface. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O-2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. The modified electrode obtained by simple adsorption of FePc directly to the Au(111) surface still promotes the 4-electron reduction process, but it shows a lower activity than the electrodes involving SAMs with FePc molecules positioned at the outmost portion of the self-assembled monolayers. The activity of the electrodes increases as follow: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc with the highest activity when FePc molecules are more separated from the Au surface. In contrast, the less active CuPc shows almost the same activity in all three configurations. Theoretical calculations suggest the importance of the back-bonding into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands. |
2016 |
Fluorescence and Surface-Enhanced Vibrational Spectroscopies of Lawsone and Plumbagin Artículo de revista Spectroscopy Letters, 49 (5), pp. 326-335, 2016, ISSN: 0038-7010. |
On the Mechanism of Co2 Electro-Cycloaddition to Propylene Oxides Artículo de revista Journal of Co2 Utilization, 16 , pp. 114-120, 2016, ISSN: 2212-9820. |
2015 |
An Easy One-Pot Solvothermal Synthesis of Poorly Crystalline Solid Res2/C Microspheres Artículo de revista Materials Chemistry and Physics, 151 , pp. 372-377, 2015, ISSN: 0254-0584. |
2013 |
Adhesion of Gold and Silver Nanoparticles onto Urea-Alkylamine Inclusion Compounds Artículo de revista Journal of Inclusion Phenomena and Macrocyclic Chemistry, 75 (1-2), pp. 165-173, 2013, ISSN: 1388-3127. |
Fabrication of Copper Nanoparticles: Advances in Synthesis, Morphology Control, and Chemical Stability Artículo de revista Recent Patents on Nanotechnology, 7 (2), pp. 108-132, 2013, ISSN: 1872-2105. |
2012 |
Electrochemical, Esr and Theoretical Insights into the Free Radical Generation by 1,1 '-Hydrocarbylenebisindazoles and Its Evaluation as Potential Bio-Active Compounds Artículo de revista International Journal of Electrochemical Science, 7 (7), pp. 5837-5863, 2012, ISSN: 1452-3981. |
Journal of Physical Chemistry C, 116 (29), pp. 15329-15341, 2012, ISSN: 1932-7447. |