Monitoring the Behavior of Na Ions and Solid Electrolyte Interphase Formation at an Aluminum/Ionic Liquid Electrode/Electrolyte Interface via Operando Electrochemical X-ray Photoelectron Spectroscopy.

In electrochemical energy storage devices, the interface between the electrode and the electrolyte plays a crucial role. A solid electrolyte interphase (SEI) is formed on the electrode surface due to spontaneous decomposition of the electrolyte, which in turn controls the dynamics of ion migration during charge and discharge cycles. However, the dynamic nature of the SEI means that its chemical structure evolves over time and as a function of the applied bias; thus, a true operando study is extremely valuable. X-ray photoelectron spectroscopy (XPS) is a widely used technique to understand the surface electronic and chemical properties, but the use of ultrahigh vacuum in standard instruments is a major hurdle for their utilization in measuring wet electrochemical processes. Herein, we introduce a 3-electrode electrochemical cell to probe the behavior of Na ions and the formation of SEI at the interface of an ionic liquid (IL) electrolyte and an aluminum electrode under operando conditions. A system containing 0.5 molar NaTFSI dissolved in the IL [BMIM][TFSI] was investigated using an Al working electrode and Pt counter and reference electrodes. By optimizing the scan rate of both XPS and cyclic voltammetry (CV) techniques, we captured the formation and evolution of SEI chemistry using real-time spectra acquisition techniques. A CV scan rate of 2 mVs-1 was coupled with XPS snapshot spectra collected at 10 s per core level. The technique demonstrated here provides a platform for the chemical analysis of materials beyond batteries.

Antibacterial activity of Cu-based nanoparticles synthesized on the cotton fabrics modified with polycarboxylic acids.

The fabrication of antimicrobial textile nanocomposite by in situ synthesis of Cu-based nanoparticles on cotton fabrics modified with different polycarboxylic acids was discussed in this study. In order to evaluate the influence of carboxyl group content on Cu2+-ions adsorption, their subsequent reduction with sodium borohydride and formation of Cu-based nanoparticles, cotton fabrics were modified with succinic, citric and 1,2,3,4-butanetetracarboxylic acids. It was shown that the larger the number of carboxyl groups in applied acid, the larger the content of free carboxyl groups on the fibers and consequently, the larger the Cu2+-ions uptake and total amounts of Cu-based nanoparticles. On the basis of the XPS and XRD measurements, it was suggested that synthesized nanoparticles were mixture of Cu2O and CuO. Fabricated nanocomposites provided maximum reduction of Gram-negative bacterium E. coli and Gram-positive bacterium S. aureus and controlled release of Cu2+-ions in physiological saline solution which are necessary prerequisites for infection prevention.

Versailles Project on Advanced Materials and Standards Interlaboratory Study on Measuring the Thickness and Chemistry of Nanoparticle Coatings Using XPS and LEIS.

We report the results of a VAMAS (Versailles Project on Advanced Materials and Standards) inter-laboratory study on the measurement of the shell thickness and chemistry of nanoparticle coatings. Peptide-coated gold particles were supplied to laboratories in two forms: a colloidal suspension in pure water and; particles dried onto a silicon wafer. Participants prepared and analyzed these samples using either X-ray photoelectron spectroscopy (XPS) or low energy ion scattering (LEIS). Careful data analysis revealed some significant sources of discrepancy, particularly for XPS. Degradation during transportation, storage or sample preparation resulted in a variability in thickness of 53 %. The calculation method chosen by XPS participants contributed a variability of 67 %. However, variability of 12 % was achieved for the samples deposited using a single method and by choosing photoelectron peaks that were not adversely affected by instrumental transmission effects. The study identified a need for more consistency in instrumental transmission functions and relative sensitivity factors, since this contributed a variability of 33 %. The results from the LEIS participants were more consistent, with variability of less than 10 % in thickness and this is mostly due to a common method of data analysis. The calculation was performed using a model developed for uniform, flat films and some participants employed a correction factor to account for the sample geometry, which appears warranted based upon a simulation of LEIS data from one of the participants and comparison to the XPS results.