Elidiane Rangel
From
Technological Plasma Laboratory, São Paulo State University - BR
In residence at
Research Group in the Energetics of Ionized Media (GREMI) / CNRS, University of Orléans - FR
Host scientist
Eric Robert
BIOGRAPHY
Elidiane C. Rangel is an Associate Professor at the Science and Technology Institute of Sorocaba, UNESP, Brazil. With a degree in Physics, from Paulista State University (1992), and a Ph.D. in Science, from Campinas State University (1999), she instructs physics classes in the Control and Automation Engineering course as well as disciplines related to Material Science and Technology in the Material Science and Technology Graduate Program, both at UNESP. Besides being a regular member of this program since 2006, she acted as its vice-coordinator from 2014 to 2017. She integrates the Laboratory of Technological Plasma at the Sorocaba unity of UNESP and the Plasma and Materials group, registered in the CNPq Brazilian agency. Her research interests encompass the processing of materials and the deposition of thin films using plasma techniques, including PECVD, PIII, PIIID, sputtering and etching. A significant focus of her work lies in the comprehensive characterization of these materials, delving into their compositional, structural, mechanical, tribological, optical, electrochemical, and thermodynamic surface properties. To achieve this, techniques such as FTIR, XPS, RBS, nanoindentation, scratching tests, UV-visible spectroscopy, contact angle measurements, and EIS are employed.
PROJECT
Antimicrobial and Catalytic Activity of Multi-metallic Nanoparticles Synthesized by Cathodic Sputtering in Liquids
The synthesis of metallic nanoparticles is carried out by means of physical and chemical methods. Current physical methods, based on material removal (top-down), include laser ablation, physical vapor deposition (PVD), pyrolysis, and electro-sputtering (JAMKHANDE, 2019). On the other hand, chemical methods (bottom-up) rely on the formation of colloidal suspensions by reducing a metallic precursor in a solution containing reducing and stabilizing agents (POLTE, 2015). Whereas physical methods provide limited amounts of material with high energy costs, chemical methods often generate residuous and leave traces of the compounds used in the nanoparticles, which may negatively affect their properties. A physico-chemical methodology recently devised for producing nanoparticles (NPs) involves cathodic sputtering using liquids as substrates, a process known as SoL (Sputtering onto Liquids) (WENDER, 2013; SERGIEVSKAYA, 2022; NGUYEN, 2018). In this method, a mono-, di-, or multi-metallic, ceramic, or composite target is bombarded in a reduced-pressure atmosphere by heavy ions such as argon. Energy deposition from inelastic collisions of the fast ions with the target induces, under specific conditions, the ejection of atoms and/or fragments. These particles are released with energies that enable their movement through the rarefied atmosphere until they reach the surface of a liquid (with reduced vapor pressure) positioned below the target. The released material penetrates the liquid surface, creating a region with a high concentration of the particulates, leading to nucleation and subsequently to the growth of nanoparticles, NPs. Although still under investigation, it is understood that the nucleation and growth of NPs are constrained by interactions with the fluid. That is, it is possible to control the dimensions of the particles, their size distribution functions, compositions, and the stability of the colloidal suspension, which is essential for preventing particulate material from coagulating, agglomerating, or oxidizing. Control is achieved by adjusting the sputtering parameters (current, voltage, power, time, pressure, plasma atmosphere composition) and the colloidal matrix parameters (viscosity, temperature, surface tension, volume/thickness of the fluid layer, and composition). There are numerous combinations of process parameters to control the properties of NPs. This diversity is evident in literature reports, often hindering direct comparisons between results obtained by different groups and conclusions about the effect of a given parameter. In this regard, the field is still relatively new, and further knowledge about synthesis mechanisms is needed. Hence, it is proposed the synthesis of multi-metallic NPs by sputtering noble metals (Pd, Au, Pt) targets onto different colloidal suspensions, and the investigation on the effect of the fluid used as support on the physicochemical properties, catalytic activity, and antimicrobial properties of the NPs. The hypotheses to be tested are whether: i) multi-metallic particles demonstrate heightened catalytic and antimicrobial capabilities compared to monometallic counterparts; ii) the colloidal matrix affects these and the other NPs properties; it is possible to anchor such particles onto nylon suture threads previously activated in cold plasma torches of N2/O2 mixtures; iii) the thread decorated with metallic nanoparticles has bacteriostatic/bactericidal effects and iv) the decorated thread, when used in hernioplasty surgery sutures, improves wound healing compared to untreated threads.
The synthesis of the NPs will be carried out in a commercial system installed at GREMI using the SoL method and Pd, Au, and Pt targets. The colloidal matrix will be accommodated in a Petri dish and positioned on the lower electrode of the reactor. Argon will be introduced (2.0 x 10⁻² Torr) and the plasma will be generated by DC signal (100 W) applied to target containing electrode. The process will be maintained for 20 minutes. The effect of colloidal suspension type, including glycerol (C₃H₈O₃), [BMI][BF₄] (1-butyl-3-methylimidazolium tetrafluoroborate, C₈H₁₅BF₄N₂), carvacrol (C₁₀H₁₄O), and PEMP (pentaerythritol tetrakis(3-mercaptopropionate), C₁₇H₂₈O₈S₄), on the properties of the NPs will be evaluated. The characteristics of the nanoparticles will be assessed by SAXS (Small Angle X-ray Scattering), TEM (Transmission Electron Microscopy), and HRTEM (High Resolution Transmission Electron Microscopy). A quartz microbalance will be used to determine the particle arrival rate in the colloidal suspension. To determine the catalytic efficiency of the NPs, a suspension containing carbon black will be decorated with them; the carbon black will be extracted by centrifugation to produce an ink that will be deposited on the working electrode of a potentiostat. The bactericidal and bacteriostatic effects of the NPs will be evaluated by in vivo microbiological tests using Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. In these tests, commercial nylon suture wires will be used as scaffolds for the multi-metallic NPs. For this purpose, the wires will be activated by a plasma torch with N₂ and O₂ mixtures and immediately after, immersed in the prepared colloidal suspensions. The wires thus prepared will be brought to Brazil for the in vivo tests, which will be conducted in cooperation with Professor Moema Hausen from PUC Sorocaba.