HERRAMIENTAS DE AUTORÍA PARA EL DISEÑO DE GUÍAS DE ESTUDIO EN LA CARRERA DE AGRONOMÍA EN LA UNICA

La necesidad de apoyar a los docentes en el perfeccionamiento de la guía de estudio de las asignaturas del Plan D, conllevó al desarrollo del trabajo en el Departamento de Ciencias Básicas y Básicas Específicas de la Facultad de Ciencias Agropecuarias. Se muestran los casos de las asignaturas Química general, Química orgánica y Metodología de la investigación, teniendo como objetivo diseñar guías de estudio, apoyadas en un conjunto de herramientas virtuales de autoría para desarrollar la independencia cognoscitiva de los estudiantes en los primeros años de la carrera de Agronomía. En las guías se elaboraron actividades variadas con un lenguaje adecuado y se combinaron diferentes mediadores didácticos, con el uso del Editor XHTML de Exelearning (eXe), Mapas Conceptuales (CmapTools 4.18), Utilidad de captura de pantalla (SnagIt 7.1.0), Sintetizador de voz (Sodelscot 3.812), siendo un entorno de autoría (creación y edición de contenido multimedia) basado en Web integrado al modelo pedagógico establecido en diferentes formas de enseñanza. En Química General las herramientas virtuales se articularon con la guía para familiarizar a los estudiantes con los equipos y utensilios de uso más frecuente en las prácticas de laboratorio. En Química Orgánica se usó como modelo la clase práctica sobre lípidos para el desarrollo de habilidades en los estudiantes. En Metodología de la Investigación se elaboró las unidades didácticas de las conferencias para orientar a los estudiantes los contenidos correspondientes a la revisión de literatura, la idea y el problema de la investigación

Zinc phthalocyanine absorbance in the near-infrared with application for transparent and colorless dye-sensitized solar cells

Transparent and colorless solar cells are attractive new photovoltaic devices as they could bring new opportunities to harness sunlight energy and particularly for their integration in windows. In this work, a new zinc phthalocyanine was synthesized and investigated as sensitizer in dye-sensitized solar cell (DSSC) for this purpose. The zinc phthalocyanine features a benzoic acid anchoring group and six thio(4-tertbutylphenyl) substituents in ${\alpha }$ position of the phtalocyanine. The dye was characterized by absorption and emission spectroscopy and by electrochemistry. The physico-chemical properties show that the dye fulfills the criteria for such an application. A detailed computational study indicates that the electronic communication with $\mathrm{TiO}_{2}$ conduction is weak owing to the absence of overlapping of the wavefunctions of the dye with those of the $\mathrm{TiO}_{2}$ semiconductor. The photovoltaic performances of the zinc phthalocyanine were measured in $\mathrm{TiO}_{2}$-based DSSC that revealed inefficient electron injection, which certainly can be explained by the weak electronic coupling of the dye with $\mathrm{TiO}_{2}$ that limits electron injection efficiency. A strategy is proposed to make better-performing sensitizers

Insights into the selective sensing mechanism of a luminescent Cd(II)-based MOF chemosensor toward NACs: roles of the host-guest interactions and PET processes

The structural and photophysical properties of the [Cd-2(H2L)(2)(H2O)(5)].5H(2)O (where H4L is the ligand 5,5'-((thiophene-2,5-dicarbonyl)bis(azanediyl))diisophthalic acid labeled as Cd-MOF), as well as the elucidation of the selective turn-off luminescent sensing mechanism toward 4-nitroaniline (pNA) were addressed, using quantum chemical methods. To reach this aim, the structures of the ground state (S-0) and first excited state (S-1) Cd-MOF/analyte system were assessed. We found that after the interaction a photoinduced electron transfer (PET) from the Cd-MOF to pNA is responsible for the fluorescence quenching in this system. For this purpose, a study was performed based on TD-DFT and multireference calculations to corroborate that an excited state exists with the adequate electronic configuration for PET process in the interacting system Cd-MOF/analyte. Intermolecular interaction between the Cd-MOF and analyte was studied by means of Morokuma-Ziegler energy decomposition analysis, natural orbitals of chemical valence, ab initio molecular dynamics (AIMD) calculations and non-covalent interactions (NCI) index. These results showed that intermolecular interactions via hydrogen bond are considerably strengthened in the excited state for the Cd-MOF/pNA, which favor the non-radiative deactivation channels of the chemosensor. In addition, the overlap of absorption spectra of Cd-MOF and pNA indicates that the loss of fluorescence is also due to internal filter effect (IFE). The most noteworthy aspect of this methodology is to consider the relative energies of the S-0 and S-1 states of MOF/analyte system to explaining the experimental behavior of Cd-MOF toward 4-nitroaniline, proving to be a robust tool in the accurate elucidation of the sensing mechanism in the MOF chemosensor

Expanding the Knowledge of the Selective-Sensing Mechanism of Nitro Compounds by Luminescent Terbium Metal-Organic Frameworks through Multiconfigurational ab Initio Calculations

The current research shows that the excited-state dynamics of the antenna ligand, both in the interacting system sensor/analyte and in the sensor without analyte, is a safe tool for elucidating the detection principle of the luminescent lanthanide-based metal-organic framework sensors. In this report the detection principle of the luminescence quenching mechanism in two Tbbased MOFs sensors is elucidated. The first system is a luminescent Tb-MOF [Tb(BTTA)1.5(H2O)4.5]n (H2BTTA = 2,5-bis(1H-1,2,4triazol-1-yl) terephthalic acid) selective to nitrobenzene (NB), labeled as Tb-1. The second system is {[Tb(DPYT)(BPDC)1/2(NO3)]center dot H2O}n (DPYT = 2,5-di(pyridin-4-yl) terephthalic acid, BPDC = biphenyl-4,4 '-dicarboxylic acid), reported as a selective chemical sensor to nitromethane (NM) in situ, labeled as Tb-2. The luminescence quenching of the MOFs is promoted by intermolecular interactions with the analytes that induce destabilization of the T1 electronic state of the linker 'antenna', altering thus the sensitization pathways of the Tb atoms. This study demonstrates the value of host-guest interaction simulations and the rate constants of the radiative and nonradiative processes in understanding and elucidating the sensing mechanism in Ln-MOF sensors

New Sensitive and Selective Chemical Sensors for Ni2+ and Cu2+ Ions: Insights into the Sensing Mechanism through DFT Methods

We report the synthesis and theoretical study of two new colorimetric chemosensors with special selectivity and sensitivity to Ni2+ and Cu2+ ions over other metal cations in the CH3CN/H2O solution. Compounds (E)-4-((2-nitrophenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl)aniline (A) and (E)-4-((3-nitrophenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl)aniline (B) exhibited a drastic color change from yellow to colorless, which allows the detection of the mentioned metal cations through different techniques. The interaction of sensors with these metal ions induced a new absorption band with a hypsochromic shift to the characteristic signal of the free sensors. A theoretical study via time-dependent density functional theory (TD-DFT) was performed. This method has enabled us to reproduce the hypsochromic shift in the maximum UV–vis absorption band and explain the selective sensing of the ions. For all of the systems studied, the absorption band is characterized by a π → π* transition centered in the ligand. Instead of Ni2+ and Cu2+ ions, the transition is set toward the σ* molecular orbital with a strong contribution of the 3dx2-y2 transition (π → 3dx2-y2). These absorptions imply a ligand-to-metal charge transfer (LMCT) mechanism that results in the hypsochromic shift in the absorption band of these systems.This work was supported by CONICYT-Chile under FONDECYT-Chile project nos. 1201880, 1180565, and 1180017; PIA CCTEAFB170007; and FONDEQUIP EQM 160070. This work was also supported by ANID/FONDAP/15110019, and the Millennium Science Initiative of the Ministry of Economy, Development and Tourism, Chile, grant Nuclei on Catalytic Processes towards Sustainable Chemistry (CSC). SEV2015-0496.Peer reviewe

Kinetic study of removal heavy metal from aqueous solution using the synthetic aluminum silicate

One of the problems that most affect humanity today is the wastewater discharge into different water bodies. It was estimated that more than 7 million tons of wastewater are generated worldwide and are discharged into rivers, lakes, and reservoirs. Among the most dangerous wastewaters are those from inorganic chemistry research laboratories, mainly due to heavy metals. These problems have become a highly relevant topic, and numerous researchers have tried to design wastewater treatment systems that will deal more efficiently with heavy metals elimination. In this work, the synthesis, characterization, and evaluation of hydrated aluminium silicate were performed as alternative wastewater treatment from chemistry research and teaching laboratories. The compound obtained was Al2O33SiO2H2O, which was characterized by the determination of its physicochemical properties. These revealed a low density, very porous material, with low crystallinity, strong chemical resistance, a large surface area, and a high apparent ionic exchange capacity. Absorption kinetics studies of heavy metals in aqueous solutions, through more widespread models, have demonstrated that Al2O33SiO2H2O has excellent properties as absorbents of this material. The amorphous hydrated aluminium silicate achieves a decrease in the concentration of all the metal ions studied, reducing them to discharge levels permissible

Understanding the Deactivating/Activating Mechanisms in Three Optical Chemosensors Based on Crown Ether with Na+/K+ Selectivity Using Quantum Chemical Tools

The optical properties and transduction mechanisms in three reported optical chemosensors based on crown ether with selectivity turn-on luminescence toward Na+ over K+, were investigated using Density Functional Theory/Time-Dependent Density Functional Theory (DFT/TD-DFT). The analysis of the structural stability of the conformers enables us to understand the optical properties of the sensors and their selectivity toward Na+. The UV-Vis absorption and the radiative channels of the adiabatic S-1 excited state were assessed. In these reported sensors, the Photoinduced Electron Transfer (PET) from the nitrogen and the oxygen (O-atoms of the substituted N-phenylaza group) lone pairs to fluorophore groups lead to a nonradiative deactivation process in the fluorophore to p-conjugated anilino-1,2,3-triazol ionophore. This Intramolecular Charge Transfer (ICT) deactivation produced the luminescence quenching in the free sensors and K+/C1 complexes. The Na+/sensor interaction produced a Chelation Enhanced Fluorescence (CHEF) due to the inhibition of the PET and ICT, which was confirmed via the calculated oscillator strength of the emission process. The K+/sensor interaction displayed the possibility of PET in C3; however, this fact was inconclusive to affirm the quenching of luminescence, the CHEF in C2 and C3 and the selectivity toward Na+ over K+ in these systems. For this reason, simulation of the absorption and emissions spectra (calculated oscillator strength), calculation of the kinetic parameters (in charge transfers and radiative deactivations process), analysis of the metal-ligand interaction character, and the analysis of the structural stability of the conformers were determinant factors to understand the selectivity and the optical properties of these chemosensors. The results suggest that these theoretical tools can also be used to predict the optical properties and Na+/K+ selectivity of optical chemosensors

Computational study on the action of saturated, monounsaturated and polyunsaturated fatty acids against Echinococcus granulosus EgFABP1

The zoonotic infection caused by tapeworms Echinococcus is a neglected tropical disease in poor regions with limited access to suitable sanitary conditions. Hydatid cysts produced by Echinococcus granulosus use fatty-acid-binding proteins (FABP) to obtain the fatty acids and cholesterol necessary for their survival from the host. In this work, we analyzed the behaviour of saturated, monounsaturated, and polyunsaturated fatty acids against EgFABP1. To achieve this goal, we used quantum mechanical analysis by density functional theory, molecular dynamics simulations, and binding free energy estimations by MM/GBSA. This study has allowed to elucidate, among a variety of fatty acids, the promising action of docosahexaenoic acid and eicosapentaenoic acid against EgFABP1. Hence, these results suggest that the action of polyunsaturated fatty acids could play an interesting role in detecting early Echinococcus granulosu