Repositório Digital da Produção Técnico Científica do IPEN

Submissões Recentes

Nickel-doped graphene films on stainless steel as efficient hydrogen recombination catalysts
2025 - RIOS, L.M.; DE MICHELI, L.; SILVESTRIN, G.; DURAZZO, M.; CARVALHO, E.F.U. de; SOUZA, R.F.B. de; GIOVEDI, C.; ANTOLINI, E.; OLIVEIRA NETO, A.
Nickel-doped catalysts supported on graphene-coated porous 304L stainless steel substrates were synthesized and evaluated for hydrogen recombination applications. The substrates, with a pore size of 50 μm, were doped with nickel loadings of 0.25, 0.50, 1.0, and 2.0 wt%. SEM analysis revealed that low nickel contents (0.25–0.50 wt%) resulted in a cracked, graphene-dominated surface and high BET surface area (up to 5.28 m2/g for 0.5 wt% Ni), whereas higher loadings (1.0–2.0 wt%) promoted the formation of dispersed metallic and nickel particles, reducing the measured surface area. XRD patterns confirmed the coexistence of austenitic and martensitic phases, spinel-type oxides, graphene-related carbon phases, and nickel-containing phases (metallic Ni, NiO, Ni (OH) 2). Raman spectroscopy revealed a five-band model (D, G, D2, D3, D4), with characteristic modifications in defect density (decreasing ID/IG ratio) and distinct features near 500 cm􀀀 1 assigned to NiO, confirming the presence of metallic and oxidized nickel phases. No signals related to iron oxides or spurious nickel oxide were observed beyond these assignments. Water contact angle measurements demonstrated strong hydrophobicity (above 120◦) for all samples, with a slight decrease at higher nickel loadings due to partial masking of graphene surfaces. Hydrogen recombination tests showed that catalytic performance improved with increasing nickel content, achieving approximately 63 % hydrogen removal with only 1.0 wt% Ni. The combined effects of high surface area (BET), well-dispersed nickel nanoparticles, and the graphene coating contributed to enhanced catalytic activity, efficient gas diffusion, and high surface hydrophobicity. These findings highlight nickel-based graphene-supported catalysts as an effective and economically viable alternative to platinum or palladium for hydrogen recombination in gas-phase applications.
Isotope-informed water sources and recharge mechanisms in a tropical karst environment of the Talgua River Basin, Honduras
2026 - CARDONA-HERNANDEZ, JORGE; ESQUIVEL-HERNANDEZ, GERMAIN; MONTEIRO, LUCILENA R.; SANCHEZ-MURILLO, RICARDO; COTRIM, MARYCEL E.B.; SANCHEZ-GUTIERREZ, ROLANDO; BIRKEL, CHRISTIAN; PENA-PAZ, TANIA; BENEGAS-NEGRI, LAURA
Understanding groundwater recharge mechanisms in karst zones is critical for preserving water supply, establishing water-use policies, and monitoring water pollution. In this study, we analyzed the isotope composition (δ2H and δ18O) of rainfall, surface water, and groundwater in the Talgua River basin in northeastern Honduras between August 2019 and December 2023. The main goal was to study the relationship between rainfall inputs and recharge mechanisms in a complex karstic environment, characterized by high rainfall seasonality and variable land use. The δ18O and δ2H relationship in rainfall resulted in a significant local meteoric water line of δ2H = 7.68 ± 0.08⋅δ18O + 9.47 ± 0.42 (N = 223, r2 = 0.97, p < 0.001). HYSPLIT air mass trajectory and cluster analysis using δ18O and deuterium excess (d-excess) revealed that moisture sources in the Talgua River basin originated mainly from the Caribbean Sea (89 %) with minimal contributions from the Pacific Ocean and the Gulf of Mexico (11 %). Recharge is mainly driven by heavy, isotopically depleted rainfall during the May–November (wet season), as indicated by the rainfall to groundwater (P/GW) 18O/16O ratios. d-excess and the lineconditioned excess (LC-excess) values indicate substantial meteoric inputs during the wet season, reflecting a recycled-moisture signal that contributes to recharge, with only minor evapoconcentration effects. This study systematically provides essential insights into rainfall, surface water, and groundwater interactions in the poorly understood karstic regions of Central America. It advances our understanding of tropical karst hydrological processes, such as moisture transport and recharge mechanisms, and provides valuable information for water resource evaluation and management.
Influence of formulation parameters on Chitosan- Gum Arabic microcapsules for aloe vera oil delivery
2025 - WEBER, RODRIGO H.; CASTRO, DIONE P. de; ARAGAO, LARISSA K.; SANCHES, MARIELE P.; SILVA, LEONARDO G. de A. e; VALLE, JOSE A.B.; ARIAS, MANUEL J.L.; VALLE, RITA de C.S.C.
This study focused on the production of Aloe vera oil (AEO) microcapsules using chitosan (Ch) and arabic gum (AG) as biopolymers to produce microcapsules. The variation of the components, such as the type of surfactant (Tween 20 or Span 80) and the molecular mass of chitosan, resulted in different characteristics in the final particles. Microcapsules produced with Tween 20 showed larger size and lower uniformity than those produced with Span 80. High molecular mass chitosan resulted in smaller microcapsules. Optical microscopy confirmed the formation of the microcapsules, and the stability of the microcapsules was influenced by particle size and zeta potential, with an inverse relationship between these properties. Fourier Transform Infrared Analysis (FTIR) analyses confirmed the functionalization of the microcapsules in 100% cotton half-mesh fabrics, and scanning electron microscopy (SEM), evidenced the formation of covalent bonds between the microcapsules and the cotton fibers. This bond ensures greater stability and encapsulation efficiency. The controlled release of the encapsulated AEO in the cotton fabric was influenced by the type of crosslinking agent and the molecular mass of chitosan. Microcapsules crosslinked with 1,2,3,4-butanetetracarboxylic acid (BTCA) showed a more consistent release, while those crosslinked with glutaraldehyde provided a slower and more controlled release, ideal for applications that require the gradual release of the active ingredient. This study demonstrated the feasibility of producing AEO microcapsules using chitosan and gum arabic. The properties of the microcapsules can be adjusted by varying the formulation components, allowing the development of controlled release systems with applications in various segments, such as the textile industry.
First record of microplastic contamination in adult endemic amazonian anuran species
2025 - SOUZA-FERREIRA, MARIA L.C. e; REIS, ADRIAN J.O. dos; FERREIRA, ERIKSON B.L.; DIPOLD, JESSICA; FREITAS, ANDERSON Z.; WETTER, NIKLAUS U.; OLIVEIRA-BAHIA, VERÔNICA R.L. de; VIEIRA, THIAGO B.
The microplastics (MPs), due to their high dispersion and bioaccumulation rates, have been identified in various animal groups, such as anuran amphibians during both larval and adult stages. However, current studies on adult anuran amphibians focus on assessing only one exposure route, the digestive system, while other routes remain underestimated. Therefore, this present study aimed to evaluate the degree of contamination in the digestive, respiratory, and integumentary systems, in situ, of two endemic Amazonian adult anuran species (Physalaemus ephippifer and Boana multifasciata). From this, we identified and characterized microplastic particles for each exposure route, assessed the effects of morphometric measures on the total MP contamination level and in the gastrointestinal tract (GIT). Additionally, we determined different contamination indices and how they vary according to species and systems. Based on our data, the digestive and integumentary exposure routes showed the highest contamination levels for both species. Additionally, variations in MP contamination levels indicated that P. ephippifer had a higher level of MP contamination. Thus, this study provides the first evidence of microplastic exposure through respiratory and integumentary routes in adult anurans in situ, and it is the first to identify MP contamination in terrestrial biomonitors in the Amazon.

Submissões Recentes

Nickel-doped graphene films on stainless steel as efficient hydrogen recombination catalysts

Isotope-informed water sources and recharge mechanisms in a tropical karst environment of the Talgua River Basin, Honduras

Influence of formulation parameters on Chitosan- Gum Arabic microcapsules for aloe vera oil delivery

First record of microplastic contamination in adult endemic amazonian anuran species