Bi-defect sites are highly effective for CO2 reduction (CO2RR) to formic acid, yet most catalytic surfaces predominantly feature inert, non-defective Bi sites. To overcome this limitation, herein, tensile strain is introduced on wholescale non-defective Bi sites. Under rapid thermal shock, the Bi-based metal-organic framework (Bi-MOF-TS) shows weakened Bi-O bonds and produced tiny Bi clusters. During electrochemical reduction, these clusters create numerous continuous vacancies, inducing weak tensile strain over a large range of surrounding non-defective Bi sites. This strain enhances *OHCO intermediates adsorption and substantially lowers the reaction barrier. As a result, Bi-MOF-TS achieves a faradaic efficiency above 90% across 800 mV potential range, with an impressive formate partial current density of -995 ± 93 mA cm-2. Notably, Bi-MOF-TS exhibits a high HCOOH faradaic efficiency of 96 ± 0.64% at 400 mA cm-2 in acidic electrolyte and a high single-pass carbon conversion efficiency (SPCE) of 62.0%. Additionally, a Zn-CO2 battery with Bi-MOF-TS as the cathode demonstrates a peak power density of 21.4 mW cm-2 and maintains stability over 300 cycles.

• Publikační typ
• časopisecké články MeSH

Variations in the composition and structure of ZnO nanoparticle interfaces have a key influence on the materials' optoelectronic properties and are responsible for high number of discrepant results reported for ZnO-based nanomaterials. Here, we conduct a systematic study of the room-temperature photoluminescence of anhydrous ZnO nanocrystals, as synthesized in the gas phase and processed in water-free atmosphere, and of their colloidal derivatives in aqueous dispersions with varying amounts of organic salt admixtures. A free exciton band at hν = 3.3 eV is essentially absent in the anhydrous ZnO nanocrystal powders measured in vacuum or in oxygen atmosphere. Surface hydration of the nanoparticles during colloid formation leads to the emergence of the free exciton band at hν = 3.3 eV and induces a small but significant release in lattice strain as detected by X-ray diffraction. Most importantly, admixture of acetate or citrate ions to the aqueous colloidal dispersions not only allows for the control of the ζ-potential but also affects the intensity of the free exciton emission in a correlated manner. The buildup of negative charge at the solid-liquid interface, as produced by citrate adsorption, increases the free exciton emission. This effect is attributed to the suppression of electron trapping in the near-surface region, which counteracts nonradiative exciton recombination. Using well-defined ZnO nanoparticles as model systems for interface chemistry studies, our findings highlight water-induced key effects that depend on the composition of the aqueous solution shell around the semiconducting metal oxide nanoparticles.

• Publikační typ
• časopisecké články MeSH

Silver (AgNPs) and maghemite, i.e., superparamagnetic iron oxide nanoparticles (SPIONs) are promising candidates for new medical applications, which implies the need for strict information regarding their physicochemical characteristics and behavior in a biological environment. The currently developed AgNPs and SPIONs encompass a myriad of sizes and surface coatings, which affect NPs properties and may improve their biocompatibility. This study is aimed to evaluate the effects of surface coating on colloidal stability and behavior of AgNPs and SPIONs in modelled biological environments using dynamic and electrophoretic light scattering techniques, as well as transmission electron microscopy to visualize the behavior of the NP. Three dispersion media were investigated: ultrapure water (UW), biological cell culture medium without addition of protein (BM), and BM supplemented with common serum protein (BMP). The obtained results showed that different coating agents on AgNPs and SPIONs produced different stabilities in the same biological media. The combination of negative charge and high adsorption strength of coating agents proved to be important for achieving good stability of metallic NPs in electrolyte-rich fluids. Most importantly, the presence of proteins provided colloidal stabilization to metallic NPs in biological fluids regardless of their chemical composition, surface structure and surface charge. In addition, an assessment of AgNP and SPION behavior in real biological fluids, rat whole blood (WhBl) and blood plasma (BlPl), revealed that the composition of a biological medium is crucial for the colloidal stability and type of metallic NP transformation. Our results highlight the importance of physicochemical characterization and stability evaluation of metallic NPs in a variety of biological systems including as many NP properties as possible.

• Klíčová slova
• biological fluids, colloidal stability, maghemite, nanoparticles, protein interaction, silver, surface coating,
• Publikační typ
• časopisecké články MeSH