Resumo em Inglês:

N,N-Dimethyltryptamine (DMT) is a serotonergic psychedelic that, when combined with monoamine oxidase enzyme inhibitors in the hallucinogenic beverage commonly known as ayahuasca, surpasses most common orally administered psychoactive drugs. There is a growing interest in the therapeutic potential of DMT due to recent clinical data showing the improvement of cognitive deficits associated with depression and Alzheimer’s disease. The development of analytical methodology for the monitoring of concentrations of DMT molecules to control the appropriate dosage for their use is essential for the treatment of patients. For this, we propose a novel flexible inkjet-printed paper substrate based on Au nanostars as proof of concept for DMT detection by surface-enhanced Raman scattering (SERS). The substrate was applied to detect DMT in water as a first approach to more complex matrices like ayahuasca beverages or blood samples. The optimization and performance of SERS substrates with different print cycles indicate that one print is enough to achieve the great performance of the flexible paper substrates. The SERS analyses for DMT in different concentrations, 10-3 to 10-10 mol L-1, reveal a high sensitivity of the sensors with a silhouette coefficient of 0.84 obtained by principal component analysis (PCA) statistical projections.

Resumo em Inglês:

Metallic nanoparticles remain the focus of diverse studies across various fields due to their exceptional properties and applications in biology, sensing, energy, and (electro)catalysis. Typical syntheses of metallic nanoparticles are solution-based and require the use of stabilizing agents. Although these surface agents prevent agglomeration, they also hinder access to active sites on the nanoparticle surface. A promising alternative is mechanochemical synthesis, offering a solvent and surfactant-free approach, which yields uniform nanoparticles with clean surfaces. Here, we employ ball milling as a mechanochemical method to prepare metallic bismuth nanoparticles in a single step, using BiVO4 semiconductor both as a bismuth source and a support. Our results demonstrate that, in addition to the formation of nanoparticles by the partial reduction of BiVO4, there is an increase in charge carriers in the semiconductor structure as probed by electrochemical experiments. The final properties of Bi@BiVO4 material make it a relevant candidate for (electro)catalysis.

Resumo em Inglês:

Surface tension (SFT) can shape the behavior of liquids in industrial chemical processes, influencing variables such as flow rate and separation efficiency. This property is commonly measured with experimental approaches such as Du Noüy ring and Wilhelmy plate methods. Here, we present machine learning (ML) methodologies that can predict the SFT of hydrocarbons. A comparative analysis encompassing k-nearest neighbors, random forest, and XGBoost (extreme gradient boosting) methods was done. Results from our study reveal that XGBoost is the most accurate in predicting hydrocarbon SFT, with a mean squared error (MSE) of 4.65 mN2 m-2 and a coefficient of determination (R2) score of 0.89. The feature importance was evaluated with the permutation feature importance method and Shapley analysis. Enthalpy of vaporization, density, molecular weight and hydrogen content are key factors in accurately predicting SFT. The successful integration of these methodologies holds the potential to impact efficiency in different industry processes.

Resumo em Inglês:

Developing new non-noble metal electrocatalysts for oxygen reduction reaction (ORR) is an essential challenge in electrochemical device research. Among these, we highlight the metal Schiff-base complexes, which can be used as modified carbon paste electrodes (CPE). Herein, we present a facile one-pot method for preparing a new family of cobalt(II) complexes with Schiffbase ligands obtained from glycine and para-substituted aldehydes. Complexes were characterized by different techniques, and the effects of para-substituents on the electronic properties of the complexes were confirmed by ultraviolet-visible spectroscopy and cyclic voltammetry (CV). The CV was also used to evaluate the ORR behavior of metal complex-modified CPE in an alkaline medium. The three complex-modified CPE were found to be highly effective for ORR, and the electron-withdrawing character of para-substituent affects the electrochemical reactivity. Density functional theory (DFT) calculations were used to complement the study and correlate the electrochemical activity, the redox potentials, and the Hammett parameter (σp) with the singly occupied molecular orbital (SOMO) energy of the complexes. DFT data were also able to shed light on the likely ORR mechanism. In summary, electronic tuning of the ligand affects the electronic properties of the metal center and allows for systematic oxygen reduction-catalytic control.

Resumo em Inglês:

Silver nanowires thin films have gained attention due to their excellent optical and electrical properties, being a potential material to be applied in optoelectronic devices as transparent conductive films, deposited on a substrate in a such way that forms a percolated network. We report the synthesis of silver nanowires with average length of 9.5 ± 0.4 µm and diameter of 75 ± 3 nm by a modified polyol method and fabrication of transparent and conductive thin films using a simple and low-cost technique as drop-casting. Additionally, we examined the influence of the drop-casting method in function of number of deposition cycles on the optical and electrical properties of the films through optical absorption and electrical resistance measurements using the two-point methodology. Increasing the number of silver nanowire deposition layers, the optical transmittance decreased from 97 (for one layer) to 60% (for five layers), and electrical resistance decreased from 940 ± 0.35 Ω for the 2-layer film to 32 ± 0.02 Ω, for the 5-layer film. Due to the electrical conductivity range of the produced silver nanowires films, we suggested their application in low-voltage circuits.

Resumo em Inglês:

Intercalation of deprotonated folic acid (FA; vitamin B9) is of great interest for nutraceutical and cosmeceutical purposes. Although some studies have already reported the intercalation of divalent (HFol2−) or trivalent (Fol3−) folate anions into layered double hydroxides (LDH), the structure, spectroscopic, and thermal behavior of such hybrid materials still need to be better understood. This work revisited the synthesis of LDH constituted by M2+/Al3+ (M2+ = Mg or Zn) intercalated with HFol2− or Fol3−. Insights concerning how the physicochemical properties of the materials are tuneable according to the synthetic approach (slow or fast coprecipitation) and pH value (7.5 or 9.0/9.5) of synthesis were pointed out. Materials synthesized at pH above 9.0 (Fol3−) presented larger particles and lower loading capacity than the ones synthesized at pH 7.5 (HFol2−). The fast coprecipitation approach led to the formation of materials with smaller particles. This work could address the following research concerning LDH-FA applications.

Resumo em Inglês:

Cadmium silicates are materials of interest due to their stability and possible application as phosphors. There are three stable forms: cadmium metasilicate, CdSiO3, cadmium orthosilicate, Cd2SiO4 and cadmium oxyorthosilicate, Cd3SiO5. Of these, oxyorthosilicate is particularly challenging to obtain, leading to fewer studies. We have successfully prepared Cd3SiO5 using a sol-gel approach, employing cadmium acetate and tetraethylorthosilicate as precursors in a stoichiometric proportion of 2:1. Additionally, cetyltrimethylammonium bromide served as a template for creating a mesoporous structure. Adjusting the pH to 3 and subjecting the material to calcination at 800 °C for 6 h, we achieved the formation of cadmium oxyorthosilicate compound, identified by X-ray diffraction. Electron diffractometry and energy dispersive X-ray spectrometry confirm the phase purity. Characterization via nitrogen adsorption analysis and transmission microscopy shows aggregates of nanoparticles with a surface area of 6 m2 g 1 and a narrow pore diameter distribution centered at 5 nm.

Resumo em Inglês:

The catalytic performance of γ-Fe2O3 nanopowder was investigated in the acetone hydrodeoxygenation (HDO) reaction, an essential catalytic reaction in biomass valorization. Sequential reduction/oxidation thermal pre-treatments of the γ-Fe2O3 nanopowder induced significant structural and electronic modifications that directly impacted its catalytic performance. The co-existence of Fe3+/Fe2+/Fe0 sites led to different reaction pathways (C-C coupling, hydrogenolysis, hydrogenation, and (hydro)deoxygenation) that formed a wide range of products. The correlation of the catalytic and structural data provided a better understanding of C-O, C-C, and C-H bond activation under the HDO reactional stream in the presence of metallic and oxidized phases of iron. This study demonstrates the tunability of FeOx catalysts in the acetone HDO reaction to favor different reaction pathways and the formation of products. It highlights that tailoring active sites is crucial for developing selective and optimized catalysts for the HDO reaction.