Luciano da Silva

This study evaluates the flame retardant efficiency of hybrid systems based on natural cellulose extracted from agricultural wastes (pecan nutshell and guayule), combined with azodicarbonamide (ADA), porous silicon dioxide (SiO₂) scaffolds, and ammonium polyphosphate (APP), incorporated into low-density polyethylene (LDPE). The waste-derived cellulose fractions were isolated via alkaline extraction and steam explosion, yielding microfibrils that preserved native lignin fractions. Porous SiO₂ particles were modified through the adsorption of ADA and APP, which in turn decorated the surface of the cellulose particles. Hybrid LDPE composites containing 20 wt% of total additives were melt-compounded and characterized. Thermogravimetric analysis (TGA) revealed an early intumescent activation that promoted robust charring, achieving final char residue yields up to 9.5 wt% for the pecan nutshell composite. Horizontal UL-94 and cone calorimeter tests demonstrated the complete elimination of hazardous flaming melt-dripping across all formulated hybrid systems, accompanied by a significant reduction in the burning rate to 18.3 mm/min and a 45% reduction in PHRR for the pecan nutshell-derived compound, consistent with a protective contribution of the multifunctional particles in the condensed phase, significantly outperforming its commercial nanocellulose counterparts. Cone calorimetry highlighted a drastic flattening of the peak heat release rate (PHRR) kinetics of composites. FTIR, TEM and TGA analyses confirmed the formation of a APP-ADA-loaded SiO₂ particle scaffold (“grenade-like” morphology), with combustion-residue FTIR and SEM/EDS supporting a protective contribution in the condensed phase.

La contaminación del agua por contaminantes emergentes, específicamente por residuos farmacéuticos, que son excretados, vertidos o filtrados en ríos, mantos acuíferos y lagos, constituye un desafío ambiental debido a su baja eliminación mediante tratamientos convencionales y a sus potenciales efectos ecotoxicológicos. Por lo tanto, es de suma importancia encontrar nuevos materiales que permitan la remediación de agua contaminada con fármacos. En este contexto, la fotocatálisis heterogénea basada en perovskitas ha emergido como una estrategia prometedora debido a la versatilidad composicional y electrónica de estos materiales. Esta revisión analiza los avances recientes en el empleo de perovskitas modificadas para la degradación fotocatalítica de fármacos en el agua, con énfasis en la relación entre estructura, composición, energía de banda, separación de portadores de carga y generación de especies reactivas de oxígeno. Se comparan estrategias de dopaje, ingeniería de defectos y formación de heteroestructuras, así como su influencia sobre la actividad fotocatalítica y los mecanismos de degradación. Asimismo, se discute el uso de captadores de especies reactivas como herramientas para la elucidación mecanicista. A pesar de las elevadas eficiencias de degradación reportadas bajo condiciones controladas, persisten desafíos relacionados con la mineralización completa, formación de intermediarios, estabilidad química, lixiviación, reciclabilidad, interferencia de matrices acuosas reales y escalamiento del proceso. En este sentido, el desarrollo futuro de estos materiales deberá orientarse hacia sistemas activos bajo luz solar, estables, recuperables y evaluados en aguas residuales reales para favorecer su transición hacia aplicaciones de tratamiento de agua a escala tecnológica.

Metal-halide perovskite solar cells combine high photovoltaic efficiency with low-temperature solution processing, but their performance and durability remain sensitive to precursor coordination, nucleation, drying, grain-boundary formation, and interfacial degradation. This critical narrative review evaluates plant-derived secondary metabolites as process-active additives rather than assuming that biological origin alone confers sustainability or passivation. Evidence is organized for alkaloids and xanthines, polyphenols and phenolic acids, and terpenoids and carotenoids, with explicit separation of experimentally demonstrated mechanisms, computational support, molecular analogy, and design hypotheses. Carbonyl-mediated coordination provides the clearest mechanistic basis for caffeine and related xanthines, whereas selected phenolic compounds have been associated, in separate studies, with coordination, crystallization control, and suppression of Sn²⁺ oxidation. Direct photovoltaic evidence now includes selected monoterpenoids, the sesquiterpene lactone artemisinin, and carotenoids, although the results remain molecule- and process-specific and do not justify class-wide generalization. The review maps molecular descriptors onto precursor chemistry, coating and crystallization variables, film structure, recombination, ion migration, device performance, and stability. Translation beyond laboratory spin coating will require specification-controlled additives, standardized stability protocols, process-compatible formulations, and iterative computational–experimental screening. This evidence-based framework identifies secondary-metabolite scaffolds as a promising but molecule-specific platform for perovskite process engineering, whose sustainability benefit remains to be established through life-cycle assessment.

Lead-free titanium halide perovskites with the formula Cs2TiClxBr6−x were integrated into an ethylene–vinyl acetate (EVA) matrix to form hybrid perovskite thin films with tunable optoelectronic properties. Importantly, this work goes beyond compositional tuning by demonstrating that the polymer–perovskite hybrid architecture actively governs interfacial charge transport and polarization phenomena. Structural and optical characterization confirmed the formation of vacancy-ordered double perovskites with visible-light absorption and photoluminescence features associated with defect-mediated electronic relaxation. The electrical and photoinduced responses of the composites were investigated using electrochemical impedance spectroscopy with symmetric fluorine-doped tin oxide (FTO)│EVA│FTO configurations. Upon illumination, the films exhibited a marked decrease in impedance, revealing the halide-dependent modulation of charge transport, interfacial polarization, and pseudocapacitive behavior. Mixed-halide compositions displayed improved electrical uniformity and reduced transport resistance compared to pristine EVA, indicating enhanced photoinduced charge dynamics. Hirshfeld surface analysis was employed as a structural descriptor to quantify halide surface exposure, thereby linking composition-dependent electronic localization to the observed photoelectrical response. As a functional demonstration of these charge dynamics, the hybrid films were also evaluated under photocatalytic conditions, where light-driven formate and hydrogen generation corroborated the effective charge separation inferred from impedance measurements.

Thermoset-like polymer composites based on poly(glycidyl methacrylate) (PGMA) functionalized by post-polymerization CO₂ cycloaddition were synthesized and reinforced with varying contents of pecan nut shell (PNS, 10–30 wt%) as a lignocellulosic filler. The CO₂ fixation step, which converts the pendant epoxide groups of PGMA into pendant five-membered cyclic carbonates, was promoted by a new Ni(bpy)₃-templated hybrid lead bromide of empirical formula [Ni(bpy)₃Pb₃Br₈·(DMF)₂], whose crystal structure was solved by single-crystal X-ray diffraction. The resulting materials were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). FTIR confirmed the partial conversion of epoxide groups into cyclic carbonates (ν =1794 and 1270 cm⁻¹) and the incorporation of the lignocellulosic phase. TGA showed a shift of the maximum decomposition temperature toward higher values (up to 418 °C in PGMA–CO₂–PNS) compared to neat PGMA, consistent with restricted segmental mobility imparted by the cyclic carbonate units and PNS filler. DSC revealed an upward shift of the glass transition and the suppression of melting transitions, supporting the formation of a crosslinked, thermoset-like network. SEM micrographs evidenced effective dispersion of PNS within the matrix and improved interfacial continuity at higher filler loadings. Overall, the combination of CO₂ valorization through cyclic-carbonate functionalization and lignocellulosic reinforcement provides an accessible route to sustainable thermoset-like composites with enhanced thermal stability, suitable for applications with low structural demands.

Sulfonated aromatic polymers (SAPs) are functionalized materials with ion‐transport capabilities, suitable for various electrolytic applications. A common route to their synthesis is direct sulfonation reactions. However, the selection of the sulfonating agent influences the occurrence of side reactions and polymer stability. In this study, commercial HIPS was chemically modified via direct sulfonation using two different sulfonating agents: concentrated sulfuric acid (S‐HIPS) and acetyl sulfate (A‐HIPS). The resulting materials were characterized by Fourier‐Transform infrared spectroscopy (FTIR), nuclear magnetic resonance ( ¹ H and ¹³ C NMR), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). FTIR spectra confirmed sulfonation through the appearance of characteristic bands of the SO ₃ H group, but rubber double bond signals disappeared in S‐HIPS and A‐HIPS. The degree of sulfonation (DS) value varies when calculated from TGA or proton NMR data, suggesting the presence of side reactions during both sulfonation processes. Sulfone‐type and rubber crosslinking processes were detected as side reactions, confirmed by RMN, TGA, and DMA. Acetyl sulfate was a more effective sulfonating agent for HIPS, yielding higher DS, fewer side reactions, and better stability.

Oilfield produced water generated during oil and gas production contains high salinity and significant concentrations of recalcitrant organic compounds, particularly organic acids. This study investigated the ozonation of benzoic acid (BA) and valeric acid (VA) as model compounds in synthetic produced water, evaluating single- and bicomponent systems under different initial pH conditions (8, 10, and 12). Additional bicomponent mixtures with mass ratios of 1:2 and 2:1 were assessed at pH 12 to examine of component interactions on degradation kinetics. Ozonation experiments were performed in a batch reactor, with degradation kinetics monitored via UHPLC–MS. Ozone concentrations in gas and aqueous phases, as well as pH variation, were continuously evaluated. Results showed that degradation efficiency strongly depends on pH and molecular structure. In single-component systems, VA degradation was highly pH-dependent, reaching ~87% at pH 12 due to intensified indirect oxidation, while BA exhibited consistently high removal efficiencies (>88%) across all pH values, reflecting its high intrinsic reactivity toward molecular ozone. In bicomponent systems, competitive effects reduced performance at pH 8 and 10; however, at pH 12 degradation efficiencies exceeded 80% for both compounds, indicating that enhanced hydroxyl radical formation mitigates competition effects. Kinetic data were satisfactorily described by a pseudo-first-order model under most conditions. The integrated evaluation of degradation kinetics, ozone consumption, and pH variation provides mechanistic insights into ozonation processes and supports its application for the treatment of produced water containing structurally diverse organic acids.