Effect of synthesis time on morphology of CeO2 nanoparticles and Au/CeO2 and their activity in oxidative steam reforming of methanol

Non-invasive ultra-sensitive detection of breast cancer biomarker using cerium nanoparticle functionalized graphene oxide enabled impedimetric aptasensor

Epidermal growth factor receptor (EGFR) is a transmembrane protein and a key biomarker implicated in the pathogenesis of breast cancer. Early and precise detection of EGFR is crucial for effective diagnosis, prognosis, and therapeutic intervention. However, conventional EGFR detection techniques, such as biopsy and immunohistochemistry, are often invasive, time-consuming, and limited in sensitivity, highlighting the demand for non-invasive, highly sensitive detection methods. In this study, we fabricated a cerium oxide (CeO₂) and graphene oxide (GO) nanocomposite-based aptasensor for the non-invasive detection of EGFR using electrochemical impedance spectroscopy (EIS). The CeO₂-GO nanocomposite was synthesized via the sol-gel method and characterized through UV-Vis spectroscopy, FTIR, TEM, and XRD, confirming the crystalline structure of hexagonal CeO₂ nanoparticles on amorphous GO sheets. The nanocomposite was functionalized with aptamers specific to EGFR using covalent coupling reactions. The EIS analysis of the fabricated aptasensor (GCE/CeO₂-GO/EGFR-Apt/BSA) demonstrated a wide linear detection range from 10 fg mL-1 to 100 ng mL-1, with an ultralow detection limit of 1.87 fg mL-1 in PBS, 3.16 fg mL-1 in serum, 5.31 fg mL-1 in sweat, and 6.14 fg mL-1 in saliva samples. These results highlight the aptasensor's high sensitivity, specificity, and potential for real-time, non-invasive EGFR monitoring in clinical samples such as serum, sweat, and saliva. This approach would facilitate early detection of cancer and personalized diagnostics in point-of-care settings.

Strain Effects on the Adsorption of Water on Cerium Dioxide Surfaces and Nanoparticles: A Modeling Outlook

Nanocrystalline ceria exhibits significant redox activity and oxygen storage capacity. Any factor affecting its morphology can tune such activities. Strain is a promising method for controlling particle morphology, whether as core@shell structures, supported nanoparticles, or nanograins in nanocrystalline ceria. A key challenge is to define routes of controlling strain to enhance the expression of more active morphologies and to maintain their shape during the lifespan of the particle. Here, we demonstrate a computational route to gain insights into the strain effects on particle morphology. We use density functional theory to predict surface composition and particle morphology of strained ceria surfaces, as a function of environmental conditions of temperature and partial pressure of water. We find that adsorbed molecular water is not sufficient to shift stability and as such under all compressive and tensile strains studied, the most stable particle is of octahedral shape, similarly to the unstrained case. When dissociative water is involved at the surfaces of the particle, then the most stable particle morphology changes under high water coverage and tensile strain to cuboidal or truncated cuboidal shapes. This shift in shape is due to strain effects that affect the strength of water adsorption.

A review study on methanol steam reforming catalysts: Evaluation of the catalytic performance, characterizations, and operational parameters

Conventional fossil-based energy sources have numerous environmental demerits; sustainable and renewable sources are attracting the undivided attention of researchers owing to their valuable physical and chemical features. Several industrial-scale technologies are employing hydrogen as a green energy source as the most preferential source. Not only is hydrogen a potent energy carrier but also it is not detrimental to the environment. Among many other hydrogen production processes, steam reforming of methanol (SRM) is deemed a practical method due to its low energy consumption. Cu, Ni, noble metals, etc., are the salient catalysts in SRM. Many researchers have conducted thorough studies incorporating improvement of the catalysts’ activity, mechanism predictions, and the impacts of operational parameters and reformers. This review concentrates on the SRM catalysts, supports, promoters, and the effect of the operational parameters on the process efficiency and H2 production yield. In this regard, the methanol conversion, H2 and CO selectivity, and operating parameters are notably contingent on the surface characterization and chemistry of the catalysts. Herein, Cu-, Ni-, and noble metal-based catalysts on various metal oxide supports, such as Al2O3 and ZnO, are assessed meticulously in the SRM process from the standpoint of mechanism and catalyst characterization. Most of the peer-reviewed studies had encountered agglomeration, metal particle sintering at high temperatures, coke formation, and deactivation of catalysts as the prevalent barriers. Hence, the novel methods of conquering the above-mentioned obstacles are evaluated in this review. Employment of diverse synthetic methods, bimetallic catalysts, distinct catalyst promoters, and unconventional supports, such as metal–organic frameworks, carbon nanotubes, and zeolites, are the salient routes to overcome the metal dispersion and thermal stability issues. In addition, the influence of operational parameters (temperature of the process, steam/carbon ratio, and feed flow rate) has been weighed painstakingly, along with introducing the research gap and future perspectives in the territory of SRM catalysts.

Relationship between hydrothermal temperatures and structural properties of CeO2 and enhanced catalytic activity of propene/toluene/CO oxidation by Au/CeO2 catalysts

A simple hydrothermal synthesis of CeO₂ was implemented to obtain a series of CeO₂-supported gold (Au) catalysts, used for the total oxidation of propene/toluene/CO gas mixtures and the oxidation of CO. CeO₂ preparation started from a cerium hydrogen carbonate precursor using a range of different hydrothermal temperatures (HT) from 120 to 180°C. High-resolution transmission electron microscopy, X-ray diffraction, and H₂-temperature-programmed reduction data indicated that CeO₂ morphology varied with the HT, and was composed of the more active (200) surface. Following Au deposition onto the CeO₂ support, this active crystal plane resulted in the most widely dispersed Au nanoparticles on the CeO₂ support. The catalytic performance of the CeO₂-supported Au catalysts for both oxidation reactions improved as the reducibility increased to generate lattice oxygen vacancies and the number of adsorbed peroxide species on the CeO₂ support increased due to addition of Au. The Au catalyst on the CeO₂ support prepared at 120°C was the most active in both propene/toluene/CO oxidation and independent CO oxidation.

Synthesis and defect characterization of hybrid ceria nanostructures as a possible novel therapeutic material towards COVID-19 mitigation

This study reports the synthesis of hybrid nanostructures composed of cerium dioxide and microcrystalline cellulose prepared by the microwave-assisted hydrothermal route under distinct temperature and pH values. Their structural, morphological and spectroscopic behaviors were investigated by X-Rays Diffraction, Field Emission Gun Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, and Fourier-Transform Infrared, Ultraviolet-Visible, Raman and Positron Annihilation Lifetime spectroscopies to evaluate the presence of structural defects and their correlation with the underlying mechanism regarding the biocide activity of the studied material. The samples showed mean crystallite sizes around 10 nm, characterizing the formation of quantum dots unevenly distributed along the cellulose surface with a certain agglomeration degree. The samples presented the characteristic Ce-O vibration close to 450 cm-1 and a second-order mode around 1050 cm-1, which is indicative of distribution of localized energetic levels originated from defective species, essential in the scavenging of reactive oxygen species. Positron spectroscopic studies showed first and second lifetime components ranging between 202-223 ps and 360-373 ps, respectively, revealing the presence of two distinct defective oxygen species, in addition to an increment in the concentration of Ce3+-oxygen vacancy associates as a function of temperature. Therefore, we have successfully synthesized hybrid nanoceria structures with potential multifunctional therapeutic properties to be further evaluated against the COVID-19.

Catalytic Conversion of n-C7 Asphaltenes and Resins II into Hydrogen Using CeO2-Based Nanocatalysts

This study focuses on evaluating the volumetric hydrogen content in the gaseous mixture released from the steam catalytic gasification of n-C₇ asphaltenes and resins II at low temperatures (<230 °C). For this purpose, four nanocatalysts were selected: CeO₂, CeO₂ functionalized with Ni-Pd, Fe-Pd, and Co-Pd. The catalytic capacity was measured by non-isothermal (from 100 to 600 °C) and isothermal (220 °C) thermogravimetric analyses. The samples show the main decomposition peak between 200 and 230 °C for bi-elemental nanocatalysts and 300 °C for the CeO₂ support, leading to reductions up to 50% in comparison with the samples in the absence of nanoparticles. At 220 °C, the conversion of both fractions increases in the order CeO₂ < Fe-Pd < Co-Pd < Ni-Pd. Hydrogen release was quantified for the isothermal tests. The hydrogen production agrees with each material’s catalytic activity for decomposing both fractions at the evaluated conditions. CeNi1Pd1 showed the highest performance among the other three samples and led to the highest hydrogen production in the effluent gas with values of ~44 vol%. When the samples were heated at higher temperatures (i.e., 230 °C), H₂ production increased up to 55 vol% during catalyzed n-C₇ asphaltene and resin conversion, indicating an increase of up to 70% in comparison with the non-catalyzed systems at the same temperature conditions.

Anticoagulation and antibacterial properties of heparinized nanosilver with different morphologies

Synthesis and characterization of nanoparticles with different morphologies coupled to minimal chemical interventions for sustainable applications is one of the contemporary topics in the field of nanotechnology. In the current study, heparinized silver nanoparticles were synthesized using a chemical reduction method. Different concentrations of heparin were used to investigate its role in the stability and morphological properties of silver nanoparticles. Interestingly, it has been observed that the concentration of the stabilizing agent heparin plays a pivotal role in dictating the size and shape of the nanosilver. As visualized under a transmission electron microscope, nanosilver with different morphological states such as triangles, truncated triangles, hexagon, and spheres has been experimentally trapped. Such modular property of heparin coated nanosilver has also exhibited substantial differences in their anticoagulation and antimicrobial activities.