In an extensive study, Jeffrey C. Everts and Miha Ravnik from the Faculty of Mathematics and Physics at University of Ljubljana and the Department F5 of Jožef Stefan Institute examined the details of the coupling of ions and singular topological defects in complex nematic fluids (Phys. Rev. X 2021). The authors showed that topological defects in nematic electrolytes could perform as areas for local separation of electric charge, forming electrically charged cores of defect and in selected geometries also electrical multi-layers. These charge distribution are generalizations of electrical double layers known in isotropic electrolytes. In particular, they show that ions couple very efficiently with the defect cores through the mechanism of ionic solubility, and with the surrounding orientation field deformations through the mechanism of flexoelectricity. The work is a significant contribution towards understanding the electrostatic mechanisms in complex soft matter.
The colleagues from Department for Gaseous Electronics of JOžef Stefan Institute and their partners within the H2020 FET-Open project “Pegasus” developed and demonstrated a novel and green approach in process engineering of graphene nanostructures used for green systems in energy storage. The researchers report one of the fastest methods for synthesizing nitrogen-doped graphene and incorporating metal oxide /sulfide nanoparticles into graphene layers simultaneously using a microwave plasma system. The authors revealed that produced graphene hybrids have higher quality and low production costs than commercially available graphene. The production method does not involve any complex chemical treatments and is an environmentally benign process. The reported plasma-driven environmental-benign approach could open many opportunities for different applications, especially for next-generation energy materials. The scientific article N-Graphene-Metal-oxide(sulfide) Hybrid Nanostructures: Single-Step Plasma-Enabled Approach for Energy Storage Applications was published in Chemical Engineering Journal, whereas the process was protected.
The physical behavior of anisotropic charged colloidal particles in nematic solvents is determined by their dielectric anisotropy. Together with the experimental group of Professor Ivan Smalyukh at University of Colorado Boulder the authors Jeffrey C. Everts and Miha Ravnik from the Faculty of Mathematics and Physics at University of Ljubljana and the Department F5 of Jozef Stefan Institute demonstrated anisotropic electrostatic screening for charged colloidal particles in nematic electrolytes. The electrostatic potential and pair interactions decay with an anisotropic Debye screening length, contrasting constant screening length for isotropic electrolytes. Charged dumpling-shaped near-spherical colloidal particles in nematic media are used as model systems, demonstrating competing anisotropic elastic and electrostatic effective pair interactions for colloidal surface charges tunable from neutral to high, yielding particle-separated metastable states (Science Advances 2021, DOI: 10.1126/sciadv.abd0662). The work was published in Science Advances and contributes to the understanding of electrostatic screening in nematic media.
The colleagues from Department for Gaseous Electronics of Jožef Stefan Institute have recently published their scientific achievements titled Label-Free Mycotoxin Raman Identification by High-Performing Plasmonic Vertical Carbon Nanostructures in top-ranked journal SMALL focused on highly important results applied at the nano- and microscale research. Targeting to improve sensing performance of vibrational-related detectors, they successfully designed a novel nanoplasmonic sensor possessing superior optical response, flexibility and robustness. Based on gold-decorated carbon nanotubes structures grown by plasma-assisted synthesis on top of a catalytic Ni foil, the reported sensor was able to provide a ppb-level Raman detection of highly hazardous mycotoxins. These secondary produced metabolites are known for their cancerogenic effect and world-wide abundance, especially in various cereals. The article reveals that mycotoxin type can be not only precisely indicated at ultralow quantities, but also accurately recognized by spectroscopic features, allowing to advance significantly the investigation of health-harmful chemical toxins.