Exsolution reactions enable the synthesis of oxide-supported metal nanoparticles, which are desirable as catalysts in green energy conversion technologies. It is crucial to precisely tailor the nanoparticle characteristics to optimize the catalysts’ functionality, and to maintain the catalytic performance under operation conditions. We use chemical (co)-doping to modify the defect chemistry of exsolution-active perovskite oxides and examine its influence on the mass transfer kinetics of Ni dopants towards the oxide surface and on the subsequent coalescence behavior of the exsolved nanoparticles during a continuous thermal reduction treatment. Nanoparticles that exsolve at the surface of the acceptor-type fast-oxygen-ion-conductor SrTi_0.95Ni_0.05O_3−δ (STNi) show a high surface mobility leading to a very low thermal stability compared to nanoparticles that exsolve at the surface of donor-type SrTi_0.9Nb_0.05Ni_0.05O_3−δ (STNNi). Our analysis indicates that the low thermal stability of exsolved nanoparticles at the acceptor-doped perovskite surface is linked to a high oxygen vacancy concentration at the nanoparticle-oxide interface. For catalysts that require fast oxygen exchange kinetics, exsolution synthesis routes in dry hydrogen conditions may hence lead to accelerated degradation, while humid reaction conditions may mitigate this failure mechanism.

Transition metal (TM) sulfides belong to the class of 2D materials with a wide application range. Various methods, including solvothermal, hydrothermal, chemical vapor deposition, and quartz ampoule-based approaches, have been employed for the synthesis of TM sulfides. Some of them face limitations due to the low stability of TM sulfides and their susceptibility to oxidation, and others require more sophisticated equipment or complex and rare precursors or are not scalable. In this work, we propose an alternative approach for the synthesis of 2D TM sulfides by sulfurization of corresponding metal oxides in the vapor of CS2 at elevated temperature. Subsequent treatment in liquid nitrogen allows exfoliation of created sulfides to a 2D structure. A proposed approach was successfully applied to nine transition metals: Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The resulting materials were extensively characterized using various analytical techniques with a focus on their crystalline structure and 2D nature. Our approach offers several advantages including the use of simple precursors (CS2 and metal oxides), universality (in all cases, the sulfides were obtained), equipment simplicity (tube furnace and quartz reactor), short preparation time (3 h), and the ability of morphology and phase tuning (in particular cases) of the created materials by adjusting the temperature. In addition, gram-scale bulk materials can be obtained in the entry-level laboratories using the proposed approach.

In this study, we designed a point-of-care (POC) testing electrochemical biosensor using an integrated biosensing assay based on hollow-like nitrogen-doped carbon nanostructures combined with cobalt nanoparticles (Co@HNCNs, Co3O4@HNCNs, and CoP@HNCNs). These are functionalized with Anti-Exendin-4 Antibodies (Anti-Ex-4-Abs) and Bovine Serum Albumin (BSA) to create sensitive probes (Co@HNCNs/Anti-Ex-4-Abs/BSA, Co3O4@HNCNs/Anti-Ex-4-Abs/BSA, and CoP@HNCNs/Anti-Ex-4-Abs/BSA) for the ultrasensitive detection of exendin-4 (Ex-4), a peptide agonist used in the treatment of type 2 diabetes mellitus (T2DM). Among the cobaltbased carbon nanostructures, the Co3O4@HNCNs/Anti-Ex-4-Abs/BSA nanoprobe demonstrated superior ability to specifically recognize Ex-4. This was indicated by a significant decrease in the chronoamperometric (CA) i-t current response, facilitating low-level detection of Ex-4. The nanoprobe was capable of detecting Ex-4 concentrations ranging from 1.0 to 90.0 pM, with a sensitivity of 0.60 mu A/pM and a limit of detection (LOD) of 0.46 pM (S/N = 3). Furthermore, the Co3O4@HNCNs/Anti-Ex-4-Abs/BSA nanoprobes demonstrated the ability to detect nanomolar levels of Ex-4 in blood serum and urine samples, achieving satisfactory recovery rates of 96-104%. The proposed electrostatic interaction chemistry approach establishes a remarkable platform for constructing a peptide agonist biosensor that is effective for detecting Ex-4 in real human serum and urine samples.

Exsolution reactions enable the synthesis of oxide-supported metal nanoparticles, desir- able as catalysts in green energy conversion technologies. It is crucial to precisely tai- lor the nanoparticle characteristics to tune the catalysts’ functionality, and to maintain the catalytic performance under operation conditions. We use chemical (co)-doping to modify the defect chemistry of exsolution-active perovskite oxides and we examine the Ni exsolu- tion behavior at atomically smooth surfaces of p-type SrTi0.95Ni0.05O3−δ (STNi) and n-type SrTi0.9Nb0.05Ni0.05O3−δ (STNNi) with identical (001) surface orientation. We identify dis- tinct differences in the mass transfer kinetics of Ni dopants towards the oxide surface and in the subsequent coalescence behavior of the exsolved nanoparticles at the perovskite surface during a continuous thermal reduction treatment. Nanoparticles that exsolve at the surface of the p-type fast-oxygen-ion-conductor STNi show a high surface mobility and thus a very low thermal stability compared to nanoparticles that exsolve at the surface of n-type STNNi. Our analysis indicates that the low thermal stability of exsolved nanoparticles at the acceptor-doped perovskite surface is associated to a large oxygen vacancy concentration at the nanoparticle-oxide interface, hampering the applicability of the exsolution synthesis route for catalysts that require a fast oxygen exchange kinetics.