Report on the outcomes of a Short-Term Scientific Mission

Action number: CA21101

Applicant name: POP NICOLINA

Details of the STSM

Title: Electronic and cation excitation processes in plasma hydrogenation of inorganic nanoparticles

Start and end date: 12/06/2023 to 19/06/2023

Description of the work carried out during the STSM

Using theoretical methods based on the Multichannel Quantum Defect Theory (MQDT) and numerical tools, we have been able to provide cross sections and rate coefficients for electron/molecular cation collisions, processes relying on superexcited molecular states and their Rydberg-valence or non-adiabatic interactions. The ions we have studied are H2+ and HD+, strongly contributing to the kinetics of various reactive gases and the plasma excitation process. H2+ molecular cations interact with WS2 nanoparticles and result in the enhancement of hydrogen adsorption and intercalation processes. We tried to establish which additional parameters are required to perform the necessary simulations. The H2 adsorption on the surface is favourable and on the topmost layer induces a widening of the distance between the topmost and the 2nd WS2 layers.

Based on the detailed explanation of the research facilities in the host laboratory and experimental setup, it has been proposed which plasma/ion beam parameters have to be adjusted to enhance hydrogen adsorption and ion implantation processes, yet avoiding cause a damage to the materials structure.

Various hydrogenation methods allow achieving different concentration of adsorbed hydrogen: low temperatures and plasma activation result in significant enhancement of hydrogen absorption rate. Diffusion of the H2 molecule on the surface of WS2 from one W atom to a neighbour W atom is easy, with small activation barriers. The magnitude of these barriers serves to rationalize the experimental results for the observed dependence of hydrogen concentration with temperature.

Description of the STSM main achievements and planned follow-up activities

Direct STSM achievement is devoted to extend the collision energies of electrons until 8eV taking into account the required plasma parameters to enhance hydrogen adsorption. The data obtained for Maxwell rate coefficients are relevant for describe the interaction of plasma-excited ions and electrons with hydrogen gas.

The extensive discussion with Dr. Alex Laikhtman, Vice Dean of Sciences Department, Holon Institute of Technology (HIT)had a significant contribution to establishing the optimal parameters for the interaction between hydrogen/deuterium plasma and inorganic nanotubes (INT) and inorganic fullerene-like (IF) nanoparticles of WS2.

Diffusion of the H2 molecule on the surface of WS2 from one W atom to a neighbour W atom is easy, with small activation barriers. The magnitude of these barriers serves to rationalize the experimental results for the observed dependence of hydrogen concentration with temperature.

Intercalating H2 molecules between adjacent planar WS2 layers is an endothermic process, although the main energy cost occurs for low H2 concentration, and the intercalation energy per H2 molecule decreases as the concentration of intercalated molecules increases.

Two-dimensional materials, such as an ultrathin tungsten disulphide (WS2) based photovoltaic cell, are strong candidates for space photovoltaics as they are very lightweight, flexible and resilient to ionizing radiation, with performance improvement from enhanced absorption. At radiation levels common for satellite altitudes up to geostationary orbit, no changes in the characteristics of the 2D materials are observed. By studying the effects

of hydrogen/deuterium plasmas and γ-irradiation in different atmospheres, WS2 monolayers exhibit significant change in its optical emission under excessive γ-irradiation.

Usefully and an opportunity was the attendence to the international event hosted by HIT, namely: “Nanotechnology From Academia to Industry”, to section which presented interest.

By this mobility was achieved one important goal of WG5: Confined Systems in Astrochemistry: Gas- and Condensed-Phase Spectroscopy and Reactivity. That is the development of methods in investigating molecular properties and chemical reactions in the gas and condensed phase molecular problems with applications in astrochemistry.

Theoretical MQDT method used by the grantee during the STSM based on ab initio calculations of intermolecular potentials, provides by computational tools, the cross sections and rate coefficients, very useful data for experimentalists Therefore, objective 5.3 of WG5 mentioned in the MoU is achieved.

STSM contributions to the Action MoU objectives and deliverables:

-Encourage and expand collaborations among various scientific communities (molecular physicists, theoretical chemists, astronomers, engineers)

-Publish and present results in high impact journals and interdisciplinary conferences.

Fig.1. Storage (Y’),Loss Modulus(Y’’),Loss factor (tan d) vs. Temperature for the PAN, Fe2O3/PAN, MnZnFerrite /PAN Nanofiber (Above DMA experiment of Fe2O3/PAN NF, before and after )

SEM results showing homogeneous nanofiber formation and nanoparticle and partially cluster distribution(Fig.2) , especially high magnification indicate that the sample is well-dispersed and has a uniform nanofiber morphology. This is a desirable outcome for many nanofiber-based applications, such as filtration, drug delivery, and tissue engineering.

Iron oxide nanoparticles in small sizes exhibit supermagnetic properties. The magnetic moment of iron oxide nanoparticles can be increased and the surface of ferrite nanoparticles can be modified by  polymers to increase their stability in solution.

Fig.2. SEM images of PAN (a), Fe2O3/PAN (b), MnZnFerrite/PAN Nanofibers

The scientific goals of the STSM will contribute to both the general goals of COSY and the specific objectives for this grant period. The study will especially contribute to COSY WG3 “Confined Metal and Metal-Oxide Nanoparticles” through the synthesis and characterization of nanofibers of magnetic metal oxide nanoparticles with biocompatible polyacrylonitrile nanofibers. This STSM study investigated the thermomechanical properties of magnetic nanoparticle-embedded polyacrylonitrile (MNPs-PAN) nanofibers across a wide temperature range in a magnetic field. Additional spectroscopic(XPS, Raman), electrochemical(CV, EIS), and morphological characterizations will be performed to elucidate the molecular interactions and properties of MNPs-PAN nanofibers.

We will disseminate the research results to the public through international peer-reviewed publications with acknowledgment of COST COSY. We have planned efforts among ITU and Univ. Vienna, integrate experimental and theoretical knowledge in further collaborations.

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