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The contingency measures put in place by the government during COVID-19 exposed the students to a new condition to which they must adapt. To understand how the students perceive and cope during the unplanned, changed learning mode, we conducted a study using an evaluation tool which seeks to understand the effect of the contingency measures associated with the emergence of the COVID-19 virus on the students. By assigning a data collection instrument to students who are part of 15 technological universities (TUs) and 7 polytechnic universities (PUs), we determined how they were affected by COVID-19. The questions intended to evaluate the social, economic, academic, emotional, and health effects experienced. A total of 6596 students were assessed in the study representing an appropriate percentage of the Mexican students. The outcome of the study showed that 12% of the students agreed with the online approach to learn adopted because of the contingency. A total of 39% reported that they have a good environmental space for online learning, 32% reported that they mostly take their classes via their mobile phones, and 3% said they lacked access to an internet facility and as such could not take their classes. A total of 14% reported that they have little access to the internet, while 42% reported that they regularly have internet, and both complained that internet fluctuation significantly affects their academic performance. Comparing the different modes of teaching, 52% believe an in-person class is the best approach to learning, but 22% agreed that a hybrid system will be effective. Through a multiple correspondence analysis (MCA) it was determined that, in the effects, there was no significant difference in relation to gender. The effects that most impacted the students were economic, connectivity, and a lack of physical activity. [ABSTRACT FROM AUTHOR]

In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B12H11SH]2− in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B12H11SH]2− in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B12H11SH]2−, cyclic voltammetry response of the probe Fe(CN)63−/Fe(CN)64− showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented Rtc and Cdl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B12H11SH]2− diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B12H11SH]2− and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode–solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B12H11SH]2− were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer. [ABSTRACT FROM AUTHOR]

In this work, we report the electrochemical response of a family of Co(II) complexes, [CoII(L)3]2+ and [CoII(L')2]2+ (L = 2,2'-bipyridine, 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline; L' = terpyridine and 4-chloro-terpyridine), in the presence and absence of CO2 in order to understand the role of the redox potential and molecular structure on the molecular catalysis of CO2 reduction. The tris chelate complexes exhibited three electron transfer processes [CoII(L)3]2+ ⇄ [CoIII(L)3]3+ + 1e−, [CoΙΙ(L)3]2++1e− ⇄ [CoΙ(L)3]+, and [CoΙ(L)3]+ + 2e- ⇄ [CoΙ(L)(L−)2]−. In the case of complexes with 1,10-phen and 2,2-bipy, the third redox process showed a coupled chemical reaction [CoΙ(L)(L−)2]− → [CoΙ(L−)2]− + L. For bis chelate complexes, three electron transfer processes associated with the redox couples [CoΙΙ(L)2]/[CoIII(L)2]3+, [CoΙΙ(L)2]2+/[CoΙ(L)2]+, and [CoΙ(L)2]+/[CoΙ(L)(L−)] were registered, including a coupled chemical reaction only for the complex containing the ligand 4-chloro-terpyridine. Foot to the wave analysis (FOWA) obtained from cyclic voltammetry experiments allowed us to calculate the catalytic rate constant (k) for the molecular catalysis of CO2 reduction. The complex [Co(3,4,7,8-tm-1,10-phen)3]2+ presented a high k value; moreover, the complex [Co(4-Cl-terpy)3]2+ did not show catalytic activity, indicating that the more negative redox potential and the absence of the coupled chemical reaction increased the molecular catalysis. Density functional theory (DFT) calculations for compounds and CO2 were obtained to rationalize the effect of electronic structure on the catalytic rate constant (k) of CO2 reduction. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) is a widely used and well studied photocatalyst synthesized using different methodologies, including sol-gel, which allows one to modify the material in a one-pot step. By using a microwave- and sonochemistry-assisted sol-gel method, x wt.% Au-TiO2 photocatalysts were successfully synthesized. Physicochemical characterization of the photocatalysts shows an average crystallite size of 10.5 nm and an even morphological distribution of spherical particles with the sonochemistry synthesis method. For the microwave method an average value of crystallite size of 8.3 nm was found and it presents an increase with the amount of Au load. The cyclic voltammetric response and Mott-Schottky analysis are consistent with a semiconductor material containing metallic particles and for a heterophase junction of anatase and brookite with oxygen vacancies, respectively. The photocatalytic activity was assessed by paracetamol degradation in an aqueous solution as model. The sonochemistry-synthesized photocatalysts display the most promising results as they have a better paracetamol removal and the amount of gold in the catalyst (0.7 wt.%) was found to be optimal for this process. [ABSTRACT FROM AUTHOR]

• An EC i mechanism is tuned by the π acceptor descriptor pKa. • Spectroelectrochemistry suggest products in the EC i mechanism. • Linear relationships among E° and k i , with the pKa were observed. • k s GOD-mediator is not controlled by E°. In this work we revisit the role of π-acceptor character of polypyridinc ligands in the electrochemical behavior of bis and tris Fe(II) complexes [FeL 3 ]2+ and [FeL′ 2 ]2+ and in the electron transfer with a representative redox enzyme, glucose oxidase GOD; (L = 1,10-phen, 5-chloro-1,10-phen, 5-nitro-1,10-phen, 5-methyl-1,10-phen, 4-methyl-1,10-phen, 5,6-dimethyl-1,10-phen, 4,7-dimethyl-1,10-phen, 2,2′-bipy, 5,5′-dimethyl-2,2′-bipy, 4,4′-dimethyl-2,2′-bipy, L′ = 2,2′6′,6″-terpy and 4-chloro-2,2′:6′,6″-terpy). The compounds presented a reversible electron transfer [Fe(II)L n ]2+ → [Fe(III)L n ]3+ 1e, (n = 1,2) followed by an unexpected coupled chemical reaction, EC i mechanism. It was established that the redox potential (E°) and the rate constant (k f) of couple reaction are tuned by the pKa of non-coordinated ligand (π acceptor character descriptor). Using UV–vis spectroelectrochemistry different products are proposed for the ECi mechanism. DFT calculations, allow us to state that changes in E°, and pKa are related to HOMO energies. Linear relationships among the electrochemical and kinetic values E°, k f , with the pKa of the ligands were obtained. Using Foot of the Wave Analysis (FOWA) the homogenous electron transfer rate constant ( k s ) for GOD mediation was calculated. From data obtained in this work and choosing similar complexes from literature, it was explored the role of redox potential in this redox mediation. [ABSTRACT FROM AUTHOR]