Although using supported noble-metal catalysts for CO₂ hydrogenation is an effective solution due to their excellent catalytic properties, metal oxide supports themselves can exhibit good activity being more economically feasible. This work focuses on investigating the complexity of the Co₃O₄ system during the CO₂ methanation reaction, which is usually accompanied by the formation of unstable dispersions of cobalt oxide and metallic Co. Herein, we have tested different types of Co₃O₄: synthetically prepared mesoporous m-Co₃O₄ (BET surface area, 95 m²/g) and commercial c-Co₃O₄ (BET surface area, 15 m²/g; purchased from Merck) in the CO₂ methanation reaction under different reduction temperatures (273–673 K). The reduction temperature was adjusted to 573 K for both the catalysts to reach the optimal Co/cobalt oxide ratio and consequently the best catalytic performance. m-Co₃O₄ is more active (CO₂ conversion 95%) and stable at higher temperatures compared to c-Co₃O₄ (CO₂ conversion 63%) due to its morphology-induced ∼66 times higher surface basicity. DRIFTS results showed differences in the detected surface species: formate was observed on m-Co₃O₄ and was proven to contribute to the total methane formation. It was revealed that in CO₂ methanation reaction, both bulk and surface properties such as morphology, cobalt oxidation states, acid–base properties, and presence of defect sites directly affect the catalytic performance and reaction mechanism. Furthermore, 1% 5 nm Pt nanoparticles were loaded onto the Co₃O₄s to check the competitiveness of the catalysts. This study evidences on a cheap noble-metal-free catalyst for CO₂ methanation consisting of m-Co₃O₄ with competitive activity and ∼100% CH₄ selectivity.

Previous theoretical reports have described the oxidation of few-layer black phosphorus and its effects on the electronic properties. Theoretically, native oxide layers bring opportunities for band gap engineering, but the detection of the different types of oxides is still a challenge at the experimental level. In this work, we uncover a correlation between thermal processes and Raman shift for the A_g¹, B_2g, and A_g² vibrational modes. The thermal expansion coefficients (temperature range, 290–485 K) for the A_g¹, B_2g, and A_g² were −0.015, −0.027, and −0.028 cm^–1 K^–1, respectively. Differential scanning calorimetry analysis shows an endothermic process centered at 528 K, and it was related with a mass increase according to thermogravimetric analysis. Raman shift temperature dependence was correlated to theoretical lattice thermal expansion, and a significant deviation was detected in the stacking direction at 500 K.

Catalytic systems prepared by controlled processes play an important role in the utilization of CO₂ via catalytic hydrogenation to produce useful C1 chemicals (such as CO, CH₄, and CH₃OH), which will be vital for forthcoming applications in energy conversion and storage. Size-controlled Pt nanoparticles were prepared by a polyol method and deposited on H-ZSM-5 (SiO₂/Al₂O₃ = 30, 80, and 280) zeolite supports. The prepared catalysts were tested for the CO₂ hydrogenation in the temperature range of T = 473–873 K and ambient pressure, with CO₂/H₂ = 1:4. Size-controlled Pt nanoparticles boosted the catalytic activity of the pure H-ZSM-5 zeolites resulted in ~16 times higher CO₂ consumption rate. The activity were ~4 times higher and CH₄ selectivity at 873 K was ~12 times higher over 0.5% Pt/H-ZSM-5 (SiO₂/Al₂O₃ = 30) compared to 0.5% Pt/H-ZSM-5 (SiO₂/Al₂O₃ = 280). In-situ DRIFTS studies assuming the presence of a surface complex in which the CO is perturbed by hydrogen and adsorbes via C-end on Pt but the oxygen tilts to the protons of the zeolite support.

Investigating the molecular composition of small extracellular vesicles (sEVs) for tumor diagnostic purposes is becoming increasingly popular, especially for diseases for which diagnosis is challenging, such as central nervous system (CNS) malignancies. Thorough examination of the molecular content of sEVs by Raman spectroscopy is a promising but hitherto barely explored approach for these tumor types. We attempt to reveal the potential role of serum-derived sEVs in diagnosing CNS tumors through Raman spectroscopic analyses using a relevant number of clinical samples. A total of 138 serum samples were obtained from four patient groups (glioblastoma multiforme, non-small-cell lung cancer brain metastasis, meningioma and lumbar disc herniation as control). After isolation, characterization and Raman spectroscopic assessment of sEVs, the Principal Component Analysis–Support Vector Machine (PCA–SVM) algorithm was performed on the Raman spectra for pairwise classifications. Classification accuracy (CA), sensitivity, specificity and the Area Under the Curve (AUC) value derived from Receiver Operating Characteristic (ROC) analyses were used to evaluate the performance of classification. The groups compared were distinguishable with 82.9–92.5% CA, 80–95% sensitivity and 80–90% specificity. AUC scores in the range of 0.82–0.9 suggest excellent and outstanding classification performance. Our results support that Raman spectroscopic analysis of sEV-enriched isolates from serum is a promising method that could be further developed in order to be applicable in the diagnosis of CNS tumors.

In the present study, NiO modified ZnAl₂O₄ and ZnO modified NiAl₂O₄ spinel along with pure Al₂O₃, ZnAl₂O₄ and NiAl₂O₄ for comparison in the CO₂ hydrogenation reaction have been investigated. It was found that NiAl₂O₄, NiO/ZnAl₂O₄ and ZnO/NiAl₂O₄ catalysts exhibited outstanding activity and selectivity towards methane even at high temperature compared to similar spinel structures reported in the literature. NiO/ZnAl₂O₄ catalyst showed CO₂ consumption rate of ~ 19 μmol/g·s at 600 °C and ~ 85% as well as ~ 50% of methane selectivity at 450 °C and 600 °C, respectively. The high activity and selectivity of methane can be attributed to the presence of metallic Ni and Ni/NiO/ZnAl₂O₄ interface under the reaction conditions as evidenced by the XRD results. Graphic High performance Ni–Zn–Al-based oxide/spinel nanostructures is synthesized and NiO/ZnAl₂O₄ catalyst exhibited higher catalytic activity in the CO₂ hydrogenation reaction due to the presence of metal support interaction between Ni and ZnAl₂O₄ support.