Topics in Catalysis最新文献

Quercetin (QCT), as an important flavonoid, has different properties including neuroprotective, anti-hyperlipidemia, decreasing blood pressure and neuroprotective effects. Hence precise determination of quercetin is noteworthy. Herein, a fast, simple, highly sensitive, and new fluorescent sensor was prepared based on Achillea Millefolium extract carbon dots stabilized on sodium alginate structure (CD/Na-Al). For confirm the reliability of synthesized sensor some characterization analysis were performed such as FT-IR and TEM. The CD/Na-Al was applied for the accurate recognition and measurement of QCT molecule. The operation mechanism for the analytical procedure was based on ‘‘turn-off’’ the fluorescence emission signal in 440 nm. The dynamic linear range was obtained in the range of 1–25 and 25–110 µM, with detection of limits equal to 0.32 and 3.9 µM respectively. The observations confirmed that the present method was able to detect trace amounts of quercetin in black tea and sur cherry with satisfy results.

In this work, CuFe₂O₄ nanoparticles (NPs) were created using a hydrothermal process. The form and size of the obtained CuFe₂O₄ NPs were characterized using XRD and TEM techniques. The Scherrer equation and XRD measurements revealed that the crystal size of nanoparticles was 10.79 nm. The TEM study of nanoparticles with an average size of 7.673.75 nm revealed a distinctive core–shell structure. The methanolysis on NaBH₄ at various parameters was used to assess the catalytic activity of NPs. The results showed that CuFe₂O₄ NPs are an effective catalyst for the methanolysis of NaBH₄ in alkaline solutions, as demonstrated by the activation energy of 33.31 kJ/mol and turnover frequency (TOF), which was estimated as 2774.61 min⁻¹ under ambient circumstances. These obtained NPs also showed an excellent (92%) reusability. A deep neural network architecture was determined using a neuro-evolutive approach based on a genetic algorithm to model the process and predict the catalyst performance in changing operating conditions. The determined models had a correlation > 0.9 and a mean squared error in the testing phase < 7.5%, indicating their capacity to capture the process dynamic effectively.

Abstract

Non-precious metal catalysts with enhanced low-temperature activity and improved water resistance are highly demanded for emission control. CuO-based catalysts are promising alternatives to precious metal catalysts due to their acceptable activity and cost-effectiveness. However, there is an urgent need to further enhance their low-temperature activity and water resistance for industrial applications. Herein, CuO catalysts supported by various SiO₂-TiO₂ supports were prepared and evaluated for CO oxidation and NO reduction by CO reactions under the testing conditions with and without water. Among the studied catalysts with different SiO₂ contents, CuO/5SiO₂-TiO₂, in which CuO was supported by SiO₂-TiO₂ with 5 wt.% SiO₂, exhibited the best performance for CO oxidation. Compared with CuO/TiO₂ and CuO/SiO₂ reference catalysts, the CuO/5SiO₂-TiO₂ catalyst showed enhanced catalytic activity in both CO oxidation and NO reduction by CO under dry and wet conditions. Comprehensive characterizations revealed that the presence of SiO₂ in TiO₂ support facilitated the CuO/5SiO₂-TiO₂ catalyst with a high dispersion and reduced oxidation states of CuO_x species. This not only improved the low-temperature reducibility but also enhanced the adsorption of reactive CO species. As a result, the CuO/5SiO₂-TiO₂ catalyst demonstrated superior catalytic activity. Furthermore, the inclusion of SiO₂ in the catalyst inhibited H₂O adsorption, contributing to the enhanced water resistance on CuO/5SiO₂-TiO₂ catalyst. These advantages in catalytic activity and water resistance make CuO/5SiO₂-TiO₂ a promising candidate for applications in emission control.

Abstract

Metallic nanoparticles have attracted great attention in catalytic, medical diagnosis, and treatment research in recent years. The formation of palladium nanoparticles using rosemary (Rosmarinus officinalis L.) extract was carried out using the green synthesis method. The plant was extracted using 70% ethanol by microwave techniques. The novelty of this study is the investigation of the biological activities of green synthesis of Pd nanoparticles, such as DNA cleavage activity, antimicrobial activity, DPPH scavenging activity, and its electro-catalytic performance in alcohol oxidation. Additionally, photocatalytic activities were also evaluated. The characterization of synthesized palladium nanoparticles (Pd NPs) was performed by UV-spectrometry, XRD, FTIR, and TEM. According to TEM results, Pd nanoparticles were observed to have a spherical shape and an average particle size of 4.91 nm. The Pd NPs showed the photodegradation of MB solution by up to 79.9% at 120 min. The newly synthesized plant-mediated green synthesized Pd NPs showed the max and the min antimicrobial activity at 16 µg/mL and 256 µg/mL against L. pneumophila and C. albicans, respectively. The current density ratio of 48.22 mA/cm² obtained in the study indicates that the obtained materials may be of interest in different applications. According to the results obtained, a direct relationship of extract use is observed in the synthesis of Pd nanoparticles and is a good way to reduce and stabilize metal salts. It has been determined that green Pd NPs have potential for use in energy production from alcohol oxidation and in medical applications.

In this work, a novel idea for obtaining in processes performed in real-world processes (here, the illustrative example is the gas phase hydrogenation of propene) a precise kinetic equation that corresponds to the experimental results was examined. The considerations are based on quasi-steady-state hypothesis and using elements of graph theory. The mathematical basis of the method used was developed by Lazman and Yablonsky [1], further considerations are presented in Yablonski et al. [2], Marin et al. [3]. The exemplary derivations of kinetic equations without simplifications are presented in the aforementioned works. The lack of assumptions allows consideration of all possible interactions between the reagents and the surface species, which is a pro of the method. However, the equation obtained usually has a complex form. Some of the parameters that result from theoretical considerations are simply insignificant for the real-world process. To eliminate this problem, the original procedure, based on statistical and process analysis, was employed. The previously determined kinetic equation, which does not have additional assumptions, was simplified. Statistical analysis helps to find and justify possible simplifications of the kinetic equation by eliminating insignificant parameters present in the kinetic equation and provides strong evidence for the correctness of the approach. The resulting kinetic equation indicates that the new proposed mechanism for the propene hydrogenation process that accepts reactions between adsorbed propene and gaseous hydrogen corresponds to the experiment. The residual sum of squares is significantly lower than those for the equations presented in the literature. The statistical test (the Akaike criterion) also indicates that the new model is better than the others. The results obtained indicate that the commonly applied approach based on the rate-determining step concept has become obsolete, apart from obvious cases. The application of the more advanced mathematical approach gives better results, as was presented.

Three vanadium complexes supported by salophan and salan ligands featuring differences in steric, electronic, and oxidation state (IV vs V) of the metal center have been evaluated for their potential in catalyzing the oxidative cleavage of a simple lignin model compound. All complexes were found to be effective, and under optimized conditions (145 °C, 48 h, in air) produced the cleavage products, phenol and benzoic acid, in good yields (62–69%) and selectivity (69–77%); significant differences in reactivity were not observed except at a lower temperature (125 °C). Complex 3c featuring sterically bulky tert butyl groups at ortho/para positions of the phenol arms, a cyclohexyl backbone and a V(V) center resulted in the highest yields and selectivity at 135 °C over 72 h (69–78% yield; 78–89% selectivity). Longer reaction times as well as reaction temperatures were found to compromise yield and selectivity for both cleavage products. An oxidizing atmosphere was found to be crucial for the observed reactivity as reactions attempted under an inert atmosphere did not result in significant conversion. Preliminary mechanistic investigations suggest that the lignin model compound is oxidized prior to undergoing cleavage, and the vanadium(V) complex is more effective at cleaving the oxidized product in comparison to the vanadium(IV) counterparts. Quite significantly, the oxidative cleavage was achieved in the absence of any basic or acidic additives.

Graphical Abstract

An effective way of monitoring the biomarker is with electrochemical sensor studies. In this work, it was formed using electrochemical deposition of high conductivity gold nanoparticles (AuNPs) and an amine-functional reduced graphene oxide (NH₂-RGO) nanocomposite. This technique not only reduced HAuCl₄ and graphene oxide in situ but also improved the electrocatalytic performance. XRD, SEM, and FTIR analytical methods confirmed the size and structure of the AuNPs/NH₂-RGO nanoparticle. As a result of XRD analysis, AuNPs/NH2-RGO crystal structure was formed. In addition, antibodies (Ab) were immobilized on the modified electrode surface using a self-assembled monolayer. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods were used to evaluate the interaction of Ab with antigen. SHBG detection had a dynamic linear range of 0.6–12 nmol/L and a limit of detection (LOD) of 0.0043 µM in enhanced sensor applications. The AuNPs/NH₂-RGO based sensor has the potential to be a valuable tool in clinical diagnostic applications in the future.