Iron-/Nitrogen-Doped Electrocatalytically Active Carbons for the Oxygen Reduction Reaction with Low Amounts of Cobalt.

Transition-metal-doped carbon catalysts are promising Pt-free alternatives for low-temperature fuel cells. They are frequently obtained from sacrificial N-rich zeolitic imidazolate frameworks (ZIFs) doped with Co and Fe. The optimal low loading of metals has to be achieved to guarantee the competitive efficiency and facilitate an inquiry into the mechanism of their catalytic activity. We report on microwave-assisted solvothermal synthesis of Zn,Co-ZIFs with a relatively low (1-15 mol %) Co loading, which were further enriched with Fe(II). Materials were pyrolyzed at 700 °C to form catalytically active carbons bearing metal nanoparticles confined in structured carbon. The electrochemistry test of carbons for the oxygen reduction reaction (ORR) in perchloric acid demonstrated their high efficiency even at low cobalt contents. The initial loading of 10 mol % was found efficient, leading to the production of catalytically active carbons allowing for four-electron path of ORR.

Sustainable Utilization of Biomass Refinery Wastes for Accessing Activated Carbons and Supercapacitor Electrode Materials.

Biomass processing wastes (humins) are anticipated to become a large-tonnage solid waste in the near future, owing to the accelerated development of renewable technologies based on utilization of carbohydrates. In this work, the utility of humins as a feedstock for the production of activated carbon by various methods (pyrolysis, physical and chemical activation, or combined approaches) was evaluated. The obtained activated carbons were tested as potential electrode materials for supercapacitor applications and demonstrated combined micro- and mesoporous structures with a good capacitance of 370 F g-1 (at a current density of 0.5 A g-1 ) and good cycling stability with a capacitance retention of 92 % after 10 000 charge/discharge cycles (at 10 A g-1 in 6 m aqueous KOH electrolyte). The applicability of the developed activated carbon for practical usage as a supercapacitor electrode material was demonstrated by its successful utilization in symmetric two-electrode cells and by powering electric devices. These findings provide a new approach to deal with the problem of sustainable wastes utilization and to advance challenging energy storage applications.

Low toxic maghemite nanoparticles for theranostic applications.

BACKGROUND: Iron oxide nanoparticles have numerous and versatile biological properties, ranging from direct and immediate biochemical effects to prolonged influences on tissues. Most applications have strict requirements with respect to the chemical and physical properties of such agents. Therefore, developing rational design methods of synthesis of iron oxide nanoparticles remains of vital importance in nanobiomedicine. METHODS: Low toxic superparamagnetic iron oxide nanoparticles (SPIONs) for theranostic applications in oncology having spherical shape and maghemite structure were produced using the fast microwave synthesis technique and were fully characterized by several complementary methods (transmission electron microscopy [TEM], X-ray diffraction [XRD], dynamic light scattering [DLS], X-ray photoelectron spectroscopy [XPS], X-ray absorption near edge structure [XANES], Mossbauer spectroscopy, and HeLa cells toxicity testing). RESULTS: TEM showed that the majority of the obtained nanoparticles were almost spherical and did not exceed 20 nm in diameter. The averaged DLS hydrodynamic size was found to be ~33 nm, while that of nanocrystallites estimated by XRD was16 nm. Both XRD and XPS studies evidenced the maghemite (γ-Fe2O3) atomic and electronic structure of the synthesized nanoparticles. The XANES data analysis demonstrated the structure of the nanoparticles being similar to that of macroscopic maghemite. The Mossbauer spectroscopy revealed the γ-Fe2O3 phase of the nanoparticles and vibration magnetometry study showed that reactive oxygen species in HeLa cells are generated both in the cytoplasm and the nucleus. CONCLUSION: Quasispherical Fe3+ SPIONs having the maghemite structure with the average size of 16 nm obtained by using the fast microwave synthesis technique are expected to be of great value for theranostic applications in oncology and multimodal anticancer therapy.