Teaching nuclear magnetic resonance (NMR) spectroscopy in undergraduate chemistry poses challenges, particularly in developing skills of the student in spectral interpretation and structural analysis. Many curricula present NMR in a fragmented way, limiting the ability of the student to connect theoretical concepts with practical data. This study proposes a didactic, integrated approach that emphasizes active learning through experimental practice and critical analysis. Techniques such as 1H, 13C, and heteronuclear multiple bond correlation (HMBC) NMR are used to explore chemical shifts, coupling constants, and molecular structure. To support this methodology, lapachol, a secondary metabolite from Tabebuia species, was extracted and used in intramolecular cyclization reactions to synthesize β-lapachone and 3-sulfonic-acid-β-lapachone. These compounds enabled comparative structural analysis and discussion of spectral changes. The inclusion of 2D NMR spectra deepened student understanding of long-range heteronuclear couplings and their relation to structural differences. This practice-oriented strategy fosters critical thinking and improves the teaching of NMR, making it more accessible and meaningful in undergraduate chemistry and related programs.
Life cycle assessment (LCA) is a tool that can identify potential environmental impacts of a system, quantify energy consumption, and detail all aspects, from raw material extraction to the recovery and/or disposal (or reuse) of materials. Life cycle impact assessment (LCIA) reports, such as ReCiPe, provide methods for calculating life cycle impact category indicators for scenarios ranging from medium to long term. However, there is a lack of studies evaluating the environmental performance of photocatalytic hydrogen production. This study assesses the environmental performance of photocatalysts across both production and operational phases, identifies the critical points in the system, and determines the conditions for optimal performance. Here, we conducted an LCA of a classical photocatalytic hydrogen-production system using Pt-CdS, considering multiple scenarios. The major environmental impacts are concentrated in the categories TETP (terrestrial ecotoxicity), HTPnc (human toxicity: non-carcinogenic), and GWP100 (global warming potential). The carbon footprint was 4.17 kg CO2 eq kg-1 H2 in the best scenario, lower than that associated with conventional routes. However, noble metals as cocatalysts, along with the low stability of the photocatalyst, pose major challenges for scale-up. These results will help guide more sustainable choices aligned with the concept of low-carbon hydrogen production, in compliance with Brazil legal framework.
To address the challenge of providing accessible hands-on experiences in advanced materials science, this study reports the design, construction, and operation of a low-cost dip-coater. Built from inexpensive mechanical and electronic components, including recycled parts from a computer digital versatile disc (DVD) drive, a step motor, a liquid crystal display (LCD), and an Arduino platform, this instrument offers a practical platform for fundamental concepts in nanomaterial fabrication, self-assembly, and spectroscopic analysis. The dip coater operates over a wide speed range of 0.44-2.4 cm min-1 and features a user-friendly HTML page through a Wi-Fi connection. It was demonstrated its application by fabricating reproducible layer-by-layer nanocomposites based on the self-assembly of Au nanoparticles on poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) thin films. Characterization using UV-Vis spectroscopy, surface-enhanced Raman spectroscopy (SERS), and atomic force microscopy (AFM) allows students to investigate critical material properties and validate the assembly processes.
This study aimed to investigate how Experimental Physical Chemistry is taught in Chemistry programs at leading Brazilian higher education institutions. To this end, 49 course syllabi publicly available online were analyzed and characterized. Data exploration revealed considerable temporal and structural disparities among these documents. At the same time, individual analysis of their components indicated limited variability in terms of content, bibliography, methodology, and assessment, even when Chemistry programs with different emphases and from different institutions were examined. Chemical kinetics and chemical equilibrium stand out as the most recurrent topics, and the recommended bibliography consists primarily of textbooks. To develop the course content, experimentation sometimes is combined with pre- and post-laboratory activities such as lectures, pre-tests, seminars, and written reports. The latter three algo serve as assessment tools for undergraduate students. Activities that deviated from this pattern were identified and discussed. Overall, the scenario suggests limited alignment between the courses investigated and the proposals found in the specialized literature on Chemistry education in general, and on Physical Chemistry education in particular.
Based on circular economy principles, sustainable biochar materials were produced from residues generated during the consumption of Brazilian-pine seeds (Araucaria angustifolia). Pristine and ZnCl2 modified biochar were prepared via thermochemical conversion and characterized. The applicability of these materials was evaluated using Cr species at low concentrations, targeting their use in analytical strategies, as green extraction and preconcentration. Batch adsorption experiments evaluated the influence of pH, contact time, and concentration. Adsorption efficiencies above 75% were achieved using a biochar dosage of 3 g L-1 and an equilibrium time of 3 h. The pristine biochar showed adsorption of CrIII at pH 4-5, whereas the modified biochar exhibited enhanced affinity toward CrVI with the pH range of 4-8. The adsorption behavior was influenced by chromium speciation and the characteristics of the biochar. Adsorption kinetics analyses indicated that chromium-biochar interactions involved both chemisorption and physisorption mechanisms. The equilibrium data were adequately described by Langmuir and Freundlich models. The maximum adsorption capacities reached 0.87 mg g-1 for CrIII on pristine biochar and 1.9 mg g-1 for CrVI on modified biochar. Overall, the results highlight the potential of these biochars as green solid-phase materials for chromium speciation, with promising applications in analytical preconcentration.
Tangential flow filtration (TFF) is widely used for high-ratio virus enrichment in wastewater, but the inhibitory effects caused by co-concentrated chemical inhibitors in wastewater concentrates on quantitative polymerase chain reaction (qPCR) quantification remain unclear. In this study, cyanophage PP, bacteriophage phi6, and pepper mild mottle virus (pMMoV) were used to evaluate qPCR inhibition in highly concentrated wastewater produced by TFF. Concentration factors obtained by plaque assay were compared with those measured by quantitative polymerase chain reaction/reverse transcription-quantitative polymerase chain reaction (qPCR/RT-qPCR), and serial dilution regression was applied to assess inhibition. At an approximately 1250-fold volume concentration, the concentration factors measured by qPCR were on average 11.2-fold lower than those measured by plaque assay. When the dilution factor exceeded 16, cycle threshold (Ct) values showed significant linear relationships with dilution, indicating that dilution effectively reduced the inhibitory effects caused by co-concentrated chemical inhibitors in the wastewater concentrate. The concentration factors of PP, Phi6, and pMMoV were further estimated to be underestimated by 5.3-fold, 72.1-fold, and 2.6-fold, respectively, with Phi6 showing the strongest inhibition. These results demonstrate that high-ratio TFF can markedly amplify qPCR inhibition in wastewater, thereby causing virus-dependent underestimation. This study quantitatively reveals this bias in highly TFF-concentrated wastewater and provides a basis for process optimization and result correction in wastewater-based epidemiology
This study analyzes the historical, epistemological, and symbolic evolution of the abstract concept of oxidation as a socio-scientific issue, with the aim of enriching the teaching and learning of chemistry from a critical and reflective perspective. Using an interpretive-hermeneutic design grounded in documentary, historical, and discursive analysis, and linked to theories of modeling and didactic transposition, an epistemological sequence was developed that highlights the paradigm shifts from the phlogiston theory to the modern electronic-level interpretation. Initially, four key moments were identified in the symbolic modeling of oxidation: oxygenic, anoxic, electronic, and algorithmic, which constitute the paradigmatic transition from qualitative macroscopic interpretations to quantitative submicroscopic experimentation. It is further argued that the redefinition of oxidation is intrinsically shaped by sociocultural factors and the symbolic complexity of each era. In the pedagogical field, the relevance of using historical models to enhance understanding, modeling, and critical examination of its teaching is emphasized. It is concluded that by integrating the historical-epistemological perspectives, contextualized and critical learning, and scientific thinking with innovative technological strategies from a social-constructivist perspective, it is possible to overcome conceptual obstacles and guide pedagogical practice toward a deeper, humanized, and meaningful scientific education.
Water/seawater electrolysis is considered a pivotal technological route toward scalable and eco-friendly hydrogen generation and is recognized as a promising renewable alternative to conventional fossil fuels. Herein, high-entropy NiFeCoCuW layered double hydroxide (LDH) flower-like microspheres are fabricated via a facile one-pot hydrothermal strategy as efficient and stable oxygen evolution catalyst. An overpotential of only 118 mV is required for the as-prepared NiFeCoCuW-LDH catalyst to achieve a current density of 10 mA cm-2 in alkaline water, highlighting its exceptional oxygen evolution reaction (OER) performance. In alkaline seawater (1 M KOH + seawater), the catalyst achieves an OER overpotential of 122 mV at 10 mA cm-2, while retaining satisfactory electrocatalytic activity. The NiFeCoCuW-LDH catalyst fabricated in this work not only possesses the superior catalytic activity and low cost of transition metal-based catalysts, but also exhibits the flexible electronic regulation capability and multimetal synergistic effects of high-entropy materials, which endows the catalyst with exceptional electrocatalytic performance.
Fertilizer pellets were prepared, derived from mixtures of biochar (obtained from pruning waste) and NPK (derived from a mixture of urea, phosphate rock and potassium chloride) in different proportions. The mixtures were characterized by Brunauer-Emmet-Teller (BET) method, pH, electrical conductivity, water absorption, near-infrared (NIR) spectroscopy and X-ray fluorescence (XRF). A completely randomized experimental design using one-way analysis of variance (ANOVA) was performed to determine the effect of biochar on NO3- (N), NH4+ (N), PO43- (P) and K+ (K) leaching using soil columns and Dunnett and Tukey’s methods were used to identify variations between treatments. The results showed that the higher biochar content in the fertilizer pellet resulted in the lower leaching of NH4+ (N), PO43- (P) and K+ (K), due to the improvement in surface area and the high calcium content found in biochar. The addition of biochar does not have a significant effect on the leaching of NO3- (N). Whitin the mixtures studied of NPK:biochar, the formulation with 1:2 ratio is the one that presents the lowest leaching of nutrients. In addition, this fertilizer pellet has a basic pH, low electrical conductivity and high-water absorption capacity, making it a good alternative for the use in agricultural production.
This study quantified Cd, Cu, Fe, Mn, and Zn in ten commercial cow’s and buffalo milk cheese using flame atomic absorption spectrometry (FAAS) after microwave-assisted digestion with nitric acid and hydrogen peroxide. The analytical procedure was designed under the principles of green chemistry, employing reduced volumes of reagents, efficient microwave-assisted digestion, and minimal waste generation. Method accuracy was confirmed by recovery tests (80.1-120.0%), with limits of detection and quantification ranging from 0.2-3.0 and 0.6-9.0 mg kg-1, respectively. In cow’s milk cheese, Cd (0.55 0.67 mg kg-1), Cu (6.92 7.53 mg kg-1), Mn (0.74 mg kg-1), and Zn (12.71-66.63 mg kg-1) were detected, while buffalo cheeses contained Cd (0.34 0.37 mg kg-1), Cu (2.75 mg kg-1), and Zn (8.14-49.33 mg kg-1). Iron was below limit of detections in all samples. Notably, Cd concentrations in three cow’s milk cheese exceeded ANVISA’s (Brazilian Health Regulatory Agency) maximum permissible levels. However, risk assessment indicated that estimated daily intakes (EDI) for all metals were below provisional maximum tolerable daily intake (PMTDI), and hazard quotients (HQ) were < 1, indicating the absence of non-carcinogenic risks. These findings highlight the importance of monitoring Cd contamination in dairy products, while also demonstrating that environmentally friendly analytical strategies can ensure reliable results with reduced ecological impact.
A Schiff base ligand (L) copper complex (LCu) is synthesized and examined using ultraviolet-visible (UV-Vis), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), and mass spectrometry. Chemical computational modelling was carried out utilizing the density functional theory (DFT)/Coulomb-attenuated method (CAM) at the Becke’s 3-parameter Lee-Yang-Parr (B3LYP) functional with a 6-31+G(d’,p’) basis set to optimize the geometry and molecular structure of the LCu. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy parameters with non-linear optical (NLO) characteristics are calculated. The findings showed that the prepared LCu exhibited optical properties as the experimental and theoretical results are in good agreement. The LCu displayed diffraction patterns (DPs) when exposed to a 473 nm continuous wave (CW) laser beam and strong self-defocusing (SDF) in a Z-scan experiment. The magnitude of the non-linear refractive index (NLRI) of the LCu, estimated using the former and latter techniques, was found to be 4.82 × 10–7 and 0.17 × ١٠–7 cm2 W–1, respectively. Two laser beams are employed to study the all-optical switching (AOS) behavior of the LCu compound.
Metal sulfide quantum dots (QDs) have gained remarkable attention in recent years owing to their broad optical tunability, high photochemical stability, and potential to replace toxic cadmium-based systems. These semiconductor nanocrystals exhibit sizeand compositiondependent electronic structures, enabling precise control of their absorption and emission across the visible and near-infrared regions. The transition from binary systems such as ZnS and CdS to more complex ternary and quaternary compositions, including CuInS2, AgInS2, and ZnCuInS/ZnS, has significantly expanded the versatility of these materials. Through compositional engineering and surface modification, it has become possible to optimize parameters such as photoluminescence quantum yield, defect density, and environmental compatibility. Consequently, metal sulfide QDs have emerged as promising candidates for diverse applications, including fluorescence bioimaging, photocatalytic degradation of organic pollutants, and solar energy conversion in next-generation photovoltaic devices. This review provides an integrated perspective on recent advances in the synthesis and compositional design of binary, ternary, and quaternary metal sulfide QDs, emphasizing the relationship between synthetic strategies, composition, and optical properties, particularly in green chemistry approaches. Key challenges are also highlighted, including control over growth mechanisms, surface chemistry, stability, and toxicity, which remain critical for their practical application in sustainable technologies.
Premature birth accounts for nearly half of perinatal deaths worldwide, making its prevention a major public health priority. Although vaginal administration of natural progesterone is an effective prophylactic strategy, its daily use is often associated with irritation and low patient adherence. In this context, biodegradable, biocompatible, and mucoadhesive polymers such as chitosan and gelatin emerge as promising materials for controlled drug delivery systems. This study aimed to develop and characterize progesterone-loaded ovules based on chitosan and gelatin for the prevention of premature birth. The formulations were produced by lyophilization and evaluated in terms of morphology, chemical structure, thermal stability, swelling behavior, biodegradation, and cytotoxicity. Fourier transform infrared spectroscopy (FTIR) analysis indicated successful incorporation of progesterone into the polymeric matrix. Swelling and biodegradation assays provided insight into the degradation profile of the system, suggesting that the matrix may support modulated progesterone diffusion. Thermal analysis (TGA) showed that pure chitosan presented greater thermal stability, while the addition of gelatin and progesterone slightly reduced this property. Cytotoxicity results confirmed the biocompatibility of the developed formulations. Overall, the findings suggest that these ovules are a promising platform for progesterone delivery and may contribute to innovative biomaterial-based approaches for the prevention of preterm birth.
This work presents a loading-dependent free-volume geometric framework for CO2 adsorption in NaX zeolite (FAU-type) based on the structural function interpreted as free pore volume within α-cavity. Unlike classical approaches, it is loading-dependent, enabling a continuous and purely analytical description of the geometric evolution of the molecular packing trajectory. Structural descriptors are derived considering the initial free pore volume and the average free volume consumed along the path and ψ is the cumulative molecular packing fraction. For two representative extreme conditions, ηVmax = 3.57 mmol g-1 (348 K, 1 bar) and ηVmax = 7.26 mmol g-1 (298 K, 10 bar), these descriptors show marked differences: low-loading condition leads to reduced initial free-pore volume (~ 157 Å3 molecule-1), and ψ = 0.64 mmol g-1, indicating weak molecular rearrangement within the adsorption pore. In contrast, the high-loading condition preserves higher F0 and ψ values, reflecting a larger structural rearrangement of the confined adsorbed phase. These descriptors provide a robust measure of the geometric severity of molecular reorganization required to NaX-CO2 reaches the saturation inside the confined α-cavity. This framework can be interpreted as a loading-dependent extension, adapted to confined adsorption systems, of the classical free-volume theory, establishing a bridge between macroscopic adsorption data and nanoscale structural interpretation.
