Topics in Catalysis最新文献

A highly sensitive electrochemical immunosensor for the detection of CYFRA21-1, a biomarker for esophageal cancer, was developed using bimetallic nanoparticle-catalyzed methylene blue as a signal amplification strategy. Au@Rh dendritic nanocrystals (DNCs) were employed as the sensing platform, while PtPd nanoparticles on polydopamine-modified hollow carbon spheres (PtPd/PDA/HCSs) were used as the signal probe. The immunosensor exhibited a wide linear range of 0.05 to 50 ng/mL, with a low detection limit of 0.01 ng/mL. It also demonstrated good specificity, reproducibility, and accuracy, with recoveries ranging from 96.8 to 104.5% in human serum samples. The presence of interfering substances commonly found in human serum did not significantly affect the immunosensor’s performance, with a relative error of less than 5%. The proposed immunosensor’s analytical performance surpasses other reported methods, making it a promising tool for early diagnosis and monitoring of esophageal cancer in clinical applications.

MnO_X-CeO₂ catalysts with different Mn and Ce content were prepared to evaluate the effect of metal content on catalytic properties and activity in the simultaneous NO reduction and o-DCB oxidation, in order to elucidate the most active species for the process. Catalytic properties were evaluated by ICP-AES, XRD, skeletal FTIR, STEM-HAADF, XPS, N₂-physisorption, H₂-TPR, NH₃-TPD and pyridine-FTIR. Catalysts with 85%Mn and 15%Ce molar content have been found to be the most active. Their excellent catalytic performance is related to the coexistence of Mn in different phases, i.e., Mn species strongly interacting with Ce and segregated Mn species. The effect of the preparation methods has also been deeply investigated: Co-precipitation method (CP) leads to Mn segregation as Mn₂O₃, whereas sol-gel preparation method (SG) promotes the formation of an amorphous powder. The synergy between segregated Mn₂O₃ species and Mn species in high interaction with Ce (resulting in a mixed oxide phase) leads to the presence of Mn with different oxidation states. This effect, together with the high oxygen mobility caused by structural defects, enhances redox, acidic and oxidative properties. The improvement of catalytic properties with Mn content also favors NO reduction side-reactions, with N₂O and NO₂ being the most important by-products, whereas it limits the production of chlorinated organic by-products in o-DCB oxidation.

In the present work, a series of supports with varying compositions (ranging from pure CeO₂ to pure PrO_2-y) was designed to investigate their ability to release oxygen (with the concomitant formation of oxygen vacancies) under diverse reducing atmospheres: hydrogen (H₂), helium (He), and in the presence of a carbonaceous substance that mimics eventual carbon deposits formed under practical reaction conditions (DRM). Oxygen vacancies were generated effectively in all three atmospheres (following the order He < H₂ < carbon material). With regard to the influence of the composition, the capability to generate oxygen vacancies clearly increased with the Pr content, for whatever the conditions tested. Notably, the non-stoichiometry obtained with the support of pure praseodymia in both inert and reducing atmospheres is very remarkable, as it approaches the maximum non-stoichiometry value of the well-established theoretical Bevan cluster. This leads to consider this formulation as a very promising support for applications in catalysis and other fields where oxygen vacancies play a crucial role. Dry Reforming of Methane requires catalytic supports that possess highly mobile oxygen, enabling it to actively participate in the reactions step involved or potentially gasify undesirable carbon deposits generated during parallel reactions. Consequently, designing and elucidating the behavior of ceria-praseodymium-based supports with high reducibility and generation of oxygen vacancies (oxygen storage and release capacity) holds particular relevance in this context. Actually, the very preliminary results comparing two counterpart formulations (5%Ni/PrO_2-y versus 5%Ni/Al₂O₃) already confirm the suitability of the choice of pure praseodymia in terms of activity, stability and very high selectivity towards H₂ and CO, reaching a very close value to the ideal H₂/CO ratio of 1.

The unregulated industrializations has poses serious threat to entire ecosystem by releasing untreated effluents containing hazardous dyes to fresh water. In the forefront polycationic ferrite (ternary ferrite)-chitosan microspheres were used to address the issue of synthetic dyes, contaminating water bodies. In the current study, visible light assisted ternary ferrite Fe₂Ni_0.5Cu_0.5O₄ (CNF-NPs) photocatalyst along with their binary ferrite photocatalysts Fe₂CuO₄ (CF-NPs) and Fe₂NiO₄ (NF-NPs) were prepared by a facile approach to compare the efficiency of ternary and binary ferrites photocatalysts for degradation of dye. Additionally, chitosan was used to support ferrites, and different chitosan-supported ternary ferrite microspheres (CNF-CM) and binary ferrite microspheres (CF-CM and NF-CM), were tailored respectively. FTIR analysis of CNF-CM composites shows presence of all the characteristics peaks of chitosan and CNF NPs confirming its synthesis. The calculated average crystallite size (18 nm) were obtained from Scherrer's equation applied to XRD data. The composition of CNF-NPs was confirmed by EDX analysis. The CNF-CM has 860 μm microsphere size with a smooth surface as shown in SEM images. The calculated optical band gap of the synthesized photocattalyst lies in visible region (2.01) obtained from Tauc’s plot. The photocatalyst CNF-CM showed 93% degradation efficiency for hazardous methylene blue (MB) and 90% efficiency for rhodamine b (RB) dyes within 140 min of sunlight irradiation at optimum conditions. Inorder to validate the photocatalytic efficiency of the CNF-CM, the experimental conditions were also optimized by statistical optimization methods (RSM, ANN). The ANOVA adequate precision (AP) value of 17.83 (> 4) for MB and 16.91 for RB suggests that the projected output variable range is relatively larger compared to the average standard error, further affirming the competence of the quadratic model.

This study explores the transformative potential of Pillared InterLayered Clays (PILC) derived from non-conventional aluminum sources as catalytic supports in the synthesis of TiO₂/catalysts for the efficient photodegradation of organic pollutants in water. Montmorillonite (Mt) and three alumina-pillared montmorillonite (PILC) synthesized using various aluminum sources, were impregnated with titanium to synthesize TiO₂/catalysts. The successful synthesis of these materials was confirmed through several characterization techniques such as X-ray diffraction (XRD), N₂ adsorption-desorption at -196 ºC, morphological analysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and Energy-Dispersive X-ray Spectrometry (EDX). The photolysis, adsorption, and catalytic behavior of the TiO₂/catalysts were studied for the degradation of triclosan (TCS), 2,6-dichlorophenol (2,6-DCP), and bisphenol A (BPA). All synthesized catalysts surpassed the efficacy of commercial anatase, with TiO₂/Al-PILC exhibiting superior performance in comparison to TiO₂/Mt. Photodegradation was most effective under UV radiation, with TCS demonstrating the highest degradation (approximately 70%). Notably, Al-PILC samples, particularly those synthesized from saline slags, displayed enhanced properties. Among them, TiO₂/Al-PILC_AE exhibited the highest degradation rates under both UV and visible light, underlining the remarkable potential of saline slags as precursors for Al-PILC synthesis. This study provides valuable insights into the design and development of efficient catalysts for water treatment applications, paving the way for sustainable and effective solutions in the realm of environmental remediation.

This work evaluates the catalytic activity of gel-type and macroreticular sulfonic styrene-divinylbenzene ion-exchange resins (IERs) incorporating metallic Pd or Cu nanoparticles for the synthesis of methyl isobutyl ketone (MIBK) from acetone following a one-pot synthesis approach. The effects of reaction time, temperature, and metal loading on the catalytic activity are studied, along with reusability (batch) and stability (fixed-bed) tests, highlighting the industrial potential of the most active catalyst prepared consisting of Pd-embedded particles within a strongly acidic gel-type IER support. Pd-based catalysts are more active than Cu ones, reaching 100% selectivity to MIBK and yields to MIBK of 36%, similar to the commercial benchmark also tested for comparison, i.e. Amberlyst™CH28. The highest yield to MIBK (54%) is obtained at 120 °C, 30 bar of H₂, 300 rpm, a catalyst load of 5 wt% and a Pd loading of 1 wt% after 24 h, with margin to improvement since the catalytic activity is found to increase with temperature up to 130 °C without detectable by-products formation. The extensive characterization by several techniques (ICP-MS, SEM–EDS, N₂ physisorption, ISEC, TEM/HRTEM, and XRD) enabled to draw crucial conclusions to understand the role of IER morphology and metal used on the catalytic activity. Sintering of both Pd and Cu nanoparticles depends on the structural type of the resin support, being magnified for macroreticular resins due to an enhanced propensity towards particle coalescence in comparison to gel-type supports. The different extent of leaching observed for the Pd- or Cu- containing IERs is explained on a basis of the behavior of the corresponding metallic nanoparticles within the resins structure. The active metallic Pd or Cu phases have been identified by HRTEM, confirming the presence of metal oxide species.

Escalating water contamination and scarcity concerns have fueled the drive for efficient waste remediation technologies. Conventional approaches, though effective, still come with limitations such as low efficacy, high costs, and generation of secondary contaminants. Various novel nanomaterials such as MXenes, (2D materials with the general formula of M_n+1X_n, M being an early transition metal, and X being carbon or nitrogen) and magnetic nanoparticles have emerged as promising candidates to combat these issues. Among them, magnetic NPs/MXenes nanohybrids stand out for their enhanced features and prospective applications in photocatalytic contaminant removal from industrial wastewater. This is attributed to their adeptness in addressing the intrinsic constraints of MXenes encompassing challenges like aggregation, toxicity, limited recyclability, and high costs. By utilizing the synergistic effects of magnetic nanoparticles and MXenes, these nanohybrids demonstrate improved conductivity, a wide surface area, and greater light absorption, contributing to efficient pollutant degradation. These materials generally have an impressive degradation efficiency exceeding 90% against textile dyes and various pollutants, showcasing remarkable reusability over multiple cycles (> 3X). Various magnetic NPs/MXenes nanohybrids, including those based on iron, cobalt, nickel, ferrites, and perovskites, are thoroughly discussed in this paper, along with their efficacy in degrading pollutants. This paper is mainly focused on fulfilling the knowledge gap on NPs/MXenes in terms of synthesis, unique features, and photocatalytic potential. This review accentuates the potential of magnetic NPs/MXenes nanohybrids as a novel approach in the realm of water remediation by compiling the existing knowledge. Besides, this work suggests future research should be focused on the diversification of composite components and expansion of these photocatalysts for degradation of a wide variety of contaminants, including organic vapors in the air.

In this study, in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to analyze the surface reactivity during the dehydration of tetrahydrofurfuryl alcohol (THFA) to 3,4-dihydro-2H-pyran (DHP). The dehydration reaction of THFA is carried out in the gas phase at 648 K using activated γ-Al₂O₃ as catalyst. Under these conditions, a yield of 84% DHP is obtained in a fixed-bed reactor and the catalyst shows no signs of deactivation after 70 h. The information obtained with DRIFT in situ spectroscopy depends on the reaction conditions, with the concentration of THFA in the gas phase being a critical variable. The temperature and time on stream have also been studied. This technique has allowed to identify DHP, the product of interest, two products with carbonyl group (C = O) formed in the surface of the catalyst during the reaction, and also the formation of carboxylates from the reaction of surface species with the oxygens of the oxide catalyst. This is of considerable significance, as an understanding of the molecular processes occurring at the surface during the reaction would permit the rational design of catalysts to enhance their catalytic properties. Therefore, in situ DRIFT spectroscopy is a valuable tool for studying active catalysts in the THFA dehydration reaction.

The discharge of industrial, agricultural, and domestic waste into water bodies has raised significant environmental concerns, necessitating effective water treatment techniques. Among the various strategies employed for pollutant removal, adsorption has emerged as a promising approach for the removal of various inorganic and organic pollutants. Chitosan, a biopolymer derived from chitin, has garnered considerable attention for removing a variety of harmful environmental contaminants due to its unique characteristics and active adsorption sites. This review provides a comprehensive analysis of utilizing chitosan-based adsorbents and catalytic materials for mitigation of various emerging contaminants in wastewater treatment. A particular emphasis is given on removing contaminants such as heavy metals, pharmaceutical compounds, organic dyes, phenolic compounds, pesticides, and the photocatalytic degradation of organic pollutants. The study also encompasses various factors influencing adsorption effectiveness, including electrostatic attraction, ion exchange, coordination, complexation, hydrogen bonding, and hydrophobic interactions. In addition, the effect of pH, contact time, initial concentration, and adsorbent dosage on adsorption capacity was also described. Furthermore, this comprehensive study explores the underlying physical and chemical interactions governing pollutant removal for a sustainable water treatment.

A new highly sensitive and powerful electroanalytical tool fabricated by two fold amplification of paste electrode (PE) with Pt/graphene nanocomposite (Pt/Gr-NC) and room temperature ionic liquid (1-Hexyl-3-methylimidazolium hexafluorophosphate (1H3MTIHFP) in this case) (Pt/Gr-NC/1H3MTIHFP/PE) for detection and determination of vitamin B₆ in environmental and food samples. The modification with a synergistic effect in the designed sensor has caused the vitamin B₆ signal to increase greatly, and the conditions for designing an ultra-sensitive sensor for the measurement with linear range 0.004–250 µM and the detection limit 0.5 nM created. On the other hand, this synergistic effect (1H3MTIHFP and Pt/Gr-NC) due to presence of has caused the vitamin B₆ oxidation signal to improve about 4.9 times and its oxidation potential to decrease by 140 mV, which means creating a sensor with high selectivity and suitable detection limit. Finally, Pt/Gr-NC/1H3MTIHFP/PE was used as a perfect analytical tool in monitoring of real samples such as fruit juices and water. Results was completely confirm ability of Pt/Gr-NC/1H3MTIHFP/PE in sensing vitamin B₆.