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This contribution describes the preparation, coupled with detailed characterization, of Nb2O5 nanofibers and their application in lithium–sulfur batteries for the improvement of electrochemical performance. The utilization of reactive needle-less electrospinning allowed us to obtain, in a single step, amorphous pre-ceramic composite PAN/Nb2O5 fibers, which were transformed into porous ceramic Nb2O5 nanofibers via calcination. Thermogravimetric studies defined that calcination at 600 °C results in crystalline ceramic fibers without carbon residues. The fibrous morphology and mean diameter (614 ± 100 nm) of the ceramic nanofibers were analyzed via scanning and transmission electron microscopy. A surface area of 7.472 m2/g was determined through nitrogen adsorption measurements, while a combination of X-ray diffraction and Raman spectroscopy was used to show the crystallinity and composition of the fibers after calcination—single T-phase Nb2O5. Its performance in the cathode of lithium–sulfur batteries was defined through electrochemical tests, and the obtained results were compared to a similar blank electrode. The initial discharge capacity of 0.5 C reached a value of 570 mAh∙g−1, while the reversible capacity of 406 mAh∙g−1 was retained after 200 cycles, representing a capacity retention of 71.3%. The presence of Nb2O5 nanofibers in the carbon cathode inhibits the shuttle effect through polysulphide confinement, which originates from porosity and chemical trapping.

Abstract With the rising demand for electricity storage devices, the performance requirements for such equipment have become increasingly stringent. Lithium-sulfur (Li-S) batteries are poised to be among the next generation of energy storage systems. However, before they can be commercially viable, several challenges must be addressed, including low sulfur conductivity and the shuttle effect. Herein, polypyrrole based sulfur composite was prepared by simple method in hydrothermal teflon lined autoclave for Li-S battery. The S/SP/ppy/PVDF electrode exhibited the initial discharge capacity of 662 mAh g− 1 at 0.5 C and 637 mAh g− 1 after 100 cycles. The Coulombic efficiency was 96% all along charge/discharge cycling. Moreover, Li-S coin cells were assembled and tested to demonstrate the potential application and scale-up of the polypyrrole-sulfur composite.

Abstract In this study, a highly sensitive, fast, and selective enzyme-free electrochemical sensor based on the deposition of Ni cavities on conductive glass was proposed for insulin detection. Considering the growing prevalence of diabetes mellitus, an electrochemical sensor for the determination of insulin was proposed for the effective diagnosis of the disease. Colloidal lithography enabled deposition of nanostructured layer (substrate) with homogeneous distribution of Ni cavities on the electrode surface with a large active surface area. The morphology and structure of conductive indium tin oxide glass modified with Ni cavities (Ni-c-ITO) were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The diameter of the resulting cavities was approximately 500 nm, while their depth was calculated at 190 ± 4 nm and 188 ± 18 nm using AFM and SEM, respectively. The insulin assay performance was evaluated by cyclic voltammetry. Ni-c-ITO exhibited excellent analytical characteristics, including high sensitivity (1.032 µA µmol−1 dm3), a low detection limit (156 µmol dm−3), and a wide dynamic range (500 nmol dm−3 to 10 µmol dm−3). Finally, the determination of insulin in buffer with interferents and in real blood serum samples revealed high specificity and demonstrated the practical potential of the method.

In this work, solution-annealed AISI 316H grade austenitic stainless steel was studied in terms of investigating the electrolytic hydrogen charging effects on the resulting Charpy impact toughness and dry sliding tribological behavior. Conventional Charpy impact bending tests were employed to study the mechanical response of the investigated material to dynamic loading conditions, whereas dry linear sliding tribological tests were used to study material friction and wear behavior. The obtained mechanical and tribological properties were correlated with corresponding fracture and tribological mechanisms, which were determined from morphological observations of fracture surfaces and tribological tracks. The applied testing procedures were individually carried out for the non-hydrogenated, hydrogen-charged, and dehydrogenated material conditions. The observed changes in individual properties due to applied hydrogen charging were rather small, which indicated the good resistance of solution-annealed AISI 316H steel against material degradation in currently used electrolytic hydrogenation conditions.

Natural zeolite clinoptilolite was modified with ammonium chloride to prepare a novel controlled release fertilizer. Zeolite as a carrier of fertilizing medium forms a “barrier” to the spontaneous release of the fertilizer into soil. Two particle size fractions of zeolites in interval up to 50 ​μm and interval up to 200 ​μm were used. Ammonium chloride solution, in varying concentrations, was then added to the dried and treated zeolite to bond with NH4+. This bonding process happens as ion-exchange. Ideal conditions for creating a zeolite fertilizer were studied using both adsorption isotherms and kinetics models. The main characteristic of the controlled release fertilizer, its release speed or rate, was studied by the diffusion process. Molecular dynamics was used to study the diffusion of water, NH4+ and combination of both through zeolite pores. It was confirmed that water enters zeolite and pushes NH4+ out. Diffusion coefficients were obtained using inner-particle diffusion model (IPD). Diffusion coefficients of real samples were obtained from slopes of change of electrical conductivity of solution over time. Diffusion coefficients, represented by slopes, were compared with different conventional controlled or slow release fertilizers. Best overall result was achieved when bonding and release slowing agent (paraffin) was used.

The article introduces a possible chemical separation of a mixture of two compounds on the metal nanorods surface. A silver nanorods surface has been prepared by controlled electrochemical deposition in anodic alumina oxide (AAO) template. Rhodamine 6G and 4-aminothiophenol have been directly applied to the sampling point on a silver nanorods surface in an aliquot mixture. The position of the resolved compounds was analysed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) which measured the fragments and the molecular ions of the two compounds separated on the silver nanorods surface. Rhodamine 6G has been preconcentrated as 1.5 mm radial from the sampling point while 4-aminothiophenol formed a continuous self-assembled monolayer on the silver nanorods surface with a maximum molecular ion intensity at a distance of 0.5 mm from the sampling point. The separation of the single chemical components from the two-component mixture over the examined silver nanostructured films could clearly be shown. A fast separation on the mentioned nanotextured films was observed (within 50 s). This procedure can be easily integrated into the micro/nanofluidic systems or chips and different detection systems can be applied.