2018 |
Diaz, C; Valenzuela, M L; Segovia, M; Correa, K; Campa, De La R; Soto, A P Solution, Solid-State Two Step Synthesis and Optical Properties of Zno and Sno2 Nanoparticles and Their Nanocomposites with Sio2 Artículo de revista Journal of Cluster Science, 29 (2), pp. 251-266, 2018, ISSN: 1040-7278. Resumen | Enlaces | BibTeX | Etiquetas: center chitin, chitosan, crystal-structure, dot fine-structure, kinetics, mechanisms, nanostructures, photoluminescence, sio2, size sno2 solid-state synthesis, zinc-oxide, zno @article{RN395, title = {Solution, Solid-State Two Step Synthesis and Optical Properties of Zno and Sno2 Nanoparticles and Their Nanocomposites with Sio2}, author = { C. Diaz and M.L. Valenzuela and M. Segovia and K. Correa and R. De La Campa and A.P. Soto}, url = {/brokenurl#<Go to ISI>://WOS:000425608200006}, doi = {10.1007/s10876-017-1324-8}, issn = {1040-7278}, year = {2018}, date = {2018-01-01}, journal = {Journal of Cluster Science}, volume = {29}, number = {2}, pages = {251-266}, abstract = {Nanostructure luminescent ZnO and SnO2 materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl2 center dot Chitosan and SnCl2 center dot Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 A degrees C. The pyrolytic ZnO and SnO2 nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl2 center dot Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO2 shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO2 was successfully incorporated into SiO2 structure (SnO2//SiO2) by pyrolysis of solid-state mixtures of the precursors SnCl2 center dot Chitosan in the presence of SiO2, the same reaction carried out with ZnCl2 center dot Chitosan precursors led to a mixture of Zn2SiO4 and SiO2. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO2, suitable for optoelectronic and sensor solid-state devices.}, keywords = {center chitin, chitosan, crystal-structure, dot fine-structure, kinetics, mechanisms, nanostructures, photoluminescence, sio2, size sno2 solid-state synthesis, zinc-oxide, zno}, pubstate = {published}, tppubtype = {article} } Nanostructure luminescent ZnO and SnO2 materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl2 center dot Chitosan and SnCl2 center dot Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 A degrees C. The pyrolytic ZnO and SnO2 nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl2 center dot Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO2 shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO2 was successfully incorporated into SiO2 structure (SnO2//SiO2) by pyrolysis of solid-state mixtures of the precursors SnCl2 center dot Chitosan in the presence of SiO2, the same reaction carried out with ZnCl2 center dot Chitosan precursors led to a mixture of Zn2SiO4 and SiO2. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO2, suitable for optoelectronic and sensor solid-state devices. |
2015 |
Mendizabal, F; Miranda-Rojas, S; Barrientos-Poblete, L A Comparative Study between Post-Hartree-Fock Methods and Density Functional Theory in Closed-Shell Aurophilic Attraction Artículo de revista Computational and Theoretical Chemistry, 1057 , pp. 74-79, 2015, ISSN: 2210-271x. Resumen | Enlaces | BibTeX | Etiquetas: attraction, au, aurophilic chemistry, clusters, complexes, correction, crystal-structures, cu dft, dimers, dispersion gold interaction, kinetics, metallophilic theoretical thermochemical @article{RN254, title = {A Comparative Study between Post-Hartree-Fock Methods and Density Functional Theory in Closed-Shell Aurophilic Attraction}, author = { F. Mendizabal and S. Miranda-Rojas and L. Barrientos-Poblete}, url = {/brokenurl#<Go to ISI>://WOS:000352042300010}, doi = {10.1016/j.comptc.2015.01.021}, issn = {2210-271x}, year = {2015}, date = {2015-01-01}, journal = {Computational and Theoretical Chemistry}, volume = {1057}, pages = {74-79}, publisher = {2015 Elsevier B.V.}, abstract = {The inter- and intramolecular aurophilic [ClAuPH3](2), [S(AuPH3)(2)] and [AuPH3](4)(2+) interactions were studied using ab initio post-Hartree-Fock and DFT methodologies. The post-Hartree-Fock methods provide results closer to the experimental data than DFT-based methods. It is possible to highlight the results obtained by the SCS-MP2 and CCSD(T) methods. In the classic [ClAuPH3](2) dimer, the aurophilic interaction is driven by the induction and dispersion terms. When DFT is used, the best results of geometry and interaction energy are obtained with the PW91 level. We find -D3 Grimme correction, M06HF, M06L, M06 M062X, M052X, CAM-B3LYP and LC-omega PBE provided results of similar accuracy as MP2.}, keywords = {attraction, au, aurophilic chemistry, clusters, complexes, correction, crystal-structures, cu dft, dimers, dispersion gold interaction, kinetics, metallophilic theoretical thermochemical}, pubstate = {published}, tppubtype = {article} } The inter- and intramolecular aurophilic [ClAuPH3](2), [S(AuPH3)(2)] and [AuPH3](4)(2+) interactions were studied using ab initio post-Hartree-Fock and DFT methodologies. The post-Hartree-Fock methods provide results closer to the experimental data than DFT-based methods. It is possible to highlight the results obtained by the SCS-MP2 and CCSD(T) methods. In the classic [ClAuPH3](2) dimer, the aurophilic interaction is driven by the induction and dispersion terms. When DFT is used, the best results of geometry and interaction energy are obtained with the PW91 level. We find -D3 Grimme correction, M06HF, M06L, M06 M062X, M052X, CAM-B3LYP and LC-omega PBE provided results of similar accuracy as MP2. |
2014 |
Gazitua, M; Tapia, R A; Contreras, R; Campodonico, P R Mechanistic Pathways of Aromatic Nucleophilic Substitution in Conventional Solvents and Ionic Liquids Artículo de revista New Journal of Chemistry, 38 (6), pp. 2611-2618, 2014, ISSN: 1144-0546. Resumen | Enlaces | BibTeX | Etiquetas: aminolysis aryl azides, benzenesulfonates, kinetics, rationalization, regioselectivity, secondary-amines, solvation @article{RN224, title = {Mechanistic Pathways of Aromatic Nucleophilic Substitution in Conventional Solvents and Ionic Liquids}, author = { M. Gazitua and R.A. Tapia and R. Contreras and P.R. Campodonico}, url = {/brokenurl#<Go to ISI>://WOS:000336821000059}, doi = {10.1039/c4nj00130c}, issn = {1144-0546}, year = {2014}, date = {2014-01-01}, journal = {New Journal of Chemistry}, volume = {38}, number = {6}, pages = {2611-2618}, abstract = {Solvation effects on the reaction mechanism of the title reactions have been kinetically evaluated in 21 conventional solvents and 17 ionic liquids. Solvent polarity affects the catalyzed and non-catalyzed SNAr pathways differently. The ambiphilic character of water and formamide, which act as a hydrogen bond donor/acceptor, induces nucleophilic activation at the nitrogen center of the nucleophile. The ionic liquid EMIMDCN appears to be the best solvent for the SNAr route probably due to the high polarizability of the dicyanamide anion.}, keywords = {aminolysis aryl azides, benzenesulfonates, kinetics, rationalization, regioselectivity, secondary-amines, solvation}, pubstate = {published}, tppubtype = {article} } Solvation effects on the reaction mechanism of the title reactions have been kinetically evaluated in 21 conventional solvents and 17 ionic liquids. Solvent polarity affects the catalyzed and non-catalyzed SNAr pathways differently. The ambiphilic character of water and formamide, which act as a hydrogen bond donor/acceptor, induces nucleophilic activation at the nitrogen center of the nucleophile. The ionic liquid EMIMDCN appears to be the best solvent for the SNAr route probably due to the high polarizability of the dicyanamide anion. |
2013 |
Ormazabal-Toledo, R; Santos, J G; Rios, P; Castro, E A; Campodonico, P R; Contreras, R Hydrogen Bond Contribution to Preferential Solvation in Snar Reactions Artículo de revista Journal of Physical Chemistry B, 117 (19), pp. 5908-5915, 2013, ISSN: 1520-6106. Resumen | Enlaces | BibTeX | Etiquetas: amines aromatic behavior, binary chemical ether, kinetics, mixtures, molecules, nucleophilic-substitution, piperidine, probes, solvent @article{RN163, title = {Hydrogen Bond Contribution to Preferential Solvation in Snar Reactions}, author = { R. Ormazabal-Toledo and J.G. Santos and P. Rios and E.A. Castro and P.R. Campodonico and R. Contreras}, url = {/brokenurl#<Go to ISI>://WOS:000319649800012}, doi = {10.1021/jp4005295}, issn = {1520-6106}, year = {2013}, date = {2013-01-01}, journal = {Journal of Physical Chemistry B}, volume = {117}, number = {19}, pages = {5908-5915}, abstract = {Preferential solvation in aromatic nucleophilic substitution reactions is discussed using a kinetic study complemented with quantum chemical calculations. The model system is the reaction of a series of secondary alicyclic amines toward phenyl 2,4,6-trinitrophenyl ether in aqueous ethanol mixtures of different compositions. From solvent effect studies, it is found that only piperidine is sensitive to solvation effects, a result that may be traced to the polarity of the solvent composition in the ethanol/water mixture, which points to a specific electrophilic solvation in the aqueous phase.}, keywords = {amines aromatic behavior, binary chemical ether, kinetics, mixtures, molecules, nucleophilic-substitution, piperidine, probes, solvent}, pubstate = {published}, tppubtype = {article} } Preferential solvation in aromatic nucleophilic substitution reactions is discussed using a kinetic study complemented with quantum chemical calculations. The model system is the reaction of a series of secondary alicyclic amines toward phenyl 2,4,6-trinitrophenyl ether in aqueous ethanol mixtures of different compositions. From solvent effect studies, it is found that only piperidine is sensitive to solvation effects, a result that may be traced to the polarity of the solvent composition in the ethanol/water mixture, which points to a specific electrophilic solvation in the aqueous phase. |
2018 |
Solution, Solid-State Two Step Synthesis and Optical Properties of Zno and Sno2 Nanoparticles and Their Nanocomposites with Sio2 Artículo de revista Journal of Cluster Science, 29 (2), pp. 251-266, 2018, ISSN: 1040-7278. |
2015 |
A Comparative Study between Post-Hartree-Fock Methods and Density Functional Theory in Closed-Shell Aurophilic Attraction Artículo de revista Computational and Theoretical Chemistry, 1057 , pp. 74-79, 2015, ISSN: 2210-271x. |
2014 |
Mechanistic Pathways of Aromatic Nucleophilic Substitution in Conventional Solvents and Ionic Liquids Artículo de revista New Journal of Chemistry, 38 (6), pp. 2611-2618, 2014, ISSN: 1144-0546. |
2013 |
Hydrogen Bond Contribution to Preferential Solvation in Snar Reactions Artículo de revista Journal of Physical Chemistry B, 117 (19), pp. 5908-5915, 2013, ISSN: 1520-6106. |