Browsing by Author "Deepak, Francis Leonard"
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- Carbon-Coated Magnetic Catalysts for Enhanced Degradation of Nitrophenols: Stability and Efficiency in Catalytic Wet Peroxide OxidationPublication . Baldo, Arthur P.; Bezerra, Ana J.B.; Silva, Adriano S.; Silva, Ana P. F.; Roman, Fernanda; Çaha, Ihsan; Bañobre-López, Manuel; Deepak, Francis Leonard; Gomes, HelderNitrophenols are persistent organic pollutants that pose serious environmental and health risks due to their toxic and lipophilic nature. Their persistence arises from strong aromatic stability and resistance to biodegradation, while their lipophilicity facilitates bioaccumulation, exacerbating ecological and human health concerns. To address this challenge, this study focuses on the synthesis and characterization of two different types of hybrid multi-core magnetic catalysts: (i) cobalt ferrite (Co-Fe2O4), which exhibits ferrimagnetic properties, and (ii) magnetite (Fe3O4), which demonstrates close superparamagnetic behavior and is coated with a novel and less hazardous phloroglucinol–glyoxal-derived resin. This approach aims to enhance catalytic efficiency while reducing the environmental impact, offering a sustainable solution for the degradation of nitrophenols in aqueous matrices. Transmission electron microscopy (TEM) images revealed the formation of a multi-core shell structure, with carbon layer sizes of 6.6 ± 0.7 nm for cobalt ferrite and 4.2 ± 0.2 nm for magnetite. The catalysts were designed to enhance the stability and performance in catalytic wet peroxide oxidation (CWPO) processes using sol–gel and solution combustion synthesis methods, respectively. In experiments of single-component degradation, the carbon-coated cobalt ferrite (CoFe@C) catalyst achieved 90% removal of 2-nitrophenol (2-NP) and 96% of 4-nitrophenol (4-NP), while carbon-coated magnetite (Fe3O4@C) demonstrated similar efficiency, with 86% removal of 2-NP and 94% of 4-NP. In the multi-component system, CoFe@C exhibited the highest catalytic activity, reaching 96% removal of 2-NP, 99% of 4-NP, and 91% decomposition of H2O2. No leaching of iron was detected in the coated catalysts, whereas the uncoated materials exhibited similar and significant leaching (CoFe: 5.66 mg/L, Fe3O4: 12 mg/L) in the single- and multi-component system. This study underscores the potential of hybrid magnetic catalysts for sustainable environmental remediation, demonstrating a dual-function mechanism that enhances catalytic activity and structural stability.
- Doxorubicin delivery performance of superparamagnetic carbon multi-core shell nanoparticles: pH dependence, stability and kinetic insightPublication . Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Sayuri Berberich, Thais; Inglez, Simone Delezuk; Bertão, Ana Raquel; Çaha, Ihsan; Deepak, Francis Leonard; Bañobre-López, Manuel; Gomes, HelderIn the past decade, magnetic nanoparticles (MNPs) have been among the most attractive nanomaterials used in different fields, such as environmental and biomedical applications. The possibility of designing nanoparticles with different functionalities allows for advancing the biomedical applications of these materials. Additionally, the magnetic characteristics of the nanoparticles enable the use of magnetic fields to drive the nanoparticles to the desired sites of delivery. In this context, the development of new MNPs in new approaches for drug delivery systems (DDSs) for cancer treatment has increased. However, the synthesis of nanoparticles with high colloidal stability triggered drug delivery, and good biocompatibility remains a challenge. Herein, multi-core shell MNPs functionalized with Pluronic ® F-127 were prepared and thoroughly characterized as drug carriers for doxorubicin delivery. The functionalized nanoparticles have an average size of 17.71 ± 4.2 nm, high water colloidal stability, and superparamagnetic behavior. In addition, the nanoparticles were able to load 936 μg of DOX per mg of functionalized nanomaterial. Drug release studies at different pH values evidenced a pH-triggered DOX release effect. An increase of 62% in cumulative drug release was observed at pH simulating tumor endosome/lysosome microenvironments (pH 4.5) compared to physiological conditions (pH 7.4). In addition, an innovative dynamic drug delivery study was performed as a function of pH. The results from this test confirmed the pH-induced doxorubicin release capability of carbon multi-core shell MNPs. The validity of traditional kinetic models to fit dynamic pH-dependent drug release was also studied for predictive purposes.
- Growth of Carbon Nanotubes on Co(x)‐Ni(1‐x) Ferrites by Chemical Vapor Deposition and Performance on Catalytic Wet Peroxide OxidationPublication . Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Olias, Lola G.; Çaha, Ihsan; Ferreira, Ana P.; Souza, Renata P. de; Deepak, Francis Leonard; Pereira, Ana I.; Silva, Adrián M. T.; Gomes, HelderUpcycling plastic solid wastes (PSWs) into high-value carbon nanotubes (CNTs) offers a promising approach to sustainable material development. This study explores the synthesis of CNTs via chemical vapor deposition (CVD) using mixed cobalt-nickel-iron oxide catalysts supported on alumina and PSW representative polyolefins as carbon sources. The impact of catalyst composition on the yield, morphology, and textural properties of CNTs was systematically evaluated. Characterization techniques, such as textural properties, transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric analysis (TGA), revealed that increasing cobalt content in the catalyst resulted in thicker CNT walls (9.2-23.6 nm) and different textural properties (SBET = 47-87 m2 g-1). The synthesized CNTs were then tested in catalytic wet peroxide oxidation (CWPO) for the degradation of sulfamethoxazole (SMX) and bisphenol A (BPA) in both single- and multi-component systems. The results indicated that a higher cobalt content in the CNT catalysts enhanced catalytic activity, particularly for BPA degradation, due to improved H2O2 decomposition. However, a higher leaching of Co and Fe was also observed. The CNTs synthesized with a Co/Ni catalyst composition ratio of 7/3 (CNT@Co0.7Ni0.3) exhibited the best balance among the tested materials in terms of CNTs yield, catalytic activity, and stability. These findings provide valuable insights to optimize CNT catalysts derived from waste plastics for environmental remediation applications.
- Hybrid multi-core shell magnetic nanoparticles for wet peroxide oxidation of paracetamol: application in synthetic and real matricesPublication . Silva, Adriano S.; Roman, Fernanda; Dias, Arnaldo; Díaz de Tuesta, Jose Luis; Narcizo, Alexandre; Silva, Ana P. F.; Çaha, Ihsan; Deepak, Francis Leonard; Bañobre-López, Manuel; Ferrari, Ana M.; Gomes, HelderClean water availability is becoming a matter of global concern in the last decades. The responsible entities for wastewater treatment do not have the proper facilities to deal with a wide range of pollutants. Special attention should be given to emerging contaminants, whose presence in water bodies may cause adverse effects on the aquatic ecosystem and human health. Most studies in the literature do not consider the development of their solution in real matrices, which can hinder the applicability of the explored alternative in the real scenario. Therefore, in this work, we demonstrate the applicability of hybrid magnetic nanoparticles for removing paracetamol (PCM) from simulated and real matrices by catalytic wet peroxide oxidation (CWPO). To achieve carbon coating, the nanoparticles were prepared via the traditional route (resorcinol/formaldehyde, CoFe@CRF). A new methodology was also considered for synthesizing thin-layered carbon-coated magnetic nanoparticles (phloroglucinol/ glyoxalic acid, CoFe@CPG). TEM images revealed a multi-core shell structure formation, with an average carbon layer size of 7.8 ± 0.5 and 3.2 ± 0.3 nm for resorcinol/formaldehyde and phloroglucinol/ glyoxalic acid methodology, respectively. Screening the materials’ activity for PCM oxidation by CWPO revealed that the nanoparticle prepared by phloroglucinol/glyoxalic acid methodology has higher performance for the degradation of PCM, achieving 63.5% mineralization after 24 h of reaction, with similar results for more complex matrices. Iron leaching measured at the end of all reactions has proven that the carbon layer protects the core against leaching.