ICPAM-15 & PAMS-6 (EGYPT)

20 noiembrie 2023 pnrrcf23.ro

T16-I1: Recent advances in metal-doped ZnO-based nanostructures as photocatalysts for the removal of organic pollutants

P. Pascariu1,2,3, C. Romanitan3 , M. Suchea2,3, Emmanuel Koudoumas2,3

Petru Poni Institute of Macromolecular Chemistry, Iasi, Romania
Center of Materials Technology and Photonics, School of Engineering, Hellenic Mediterranean University, Heraklion, Greece 3National Institute for Research and Development in Microtechnologies -IMT Bucharest, Bucharest, Romania

During the last few decades, industrialization and urbanization have caused serious environmental problems that have become worse every year, especially the pollution of aquatic environments that threaten life on Earth. Numerous organic compounds, which cannot be completely metabolized, find their way into aquatic ecosystems, the residual pollutants in them causing significant biological toxicity to the aquatic environment. Residual pollutants like dyes, antibiotics, and pesticides present in the water can harm liver and kidney functions, suppress the immune system, and cause health problems. This work summarizes the recent advances in photocatalysis involving various metals (Er, Sm, La, Nd, Ce, etc.) doped ZnO semiconducting materials developed by the electrospinning-calcination method for the removal of organic pollutants [1-3]. Specific details regarding the synthesis, characterization, application, and mechanism of action of these semiconducting catalysts are highlighted. It will be proven how the photocatalytic performances of these materials can be improved by doping with different transition metals (lanthanides). In many studies, the metal-doped ZnO semiconductor materials were tested as photocatalysts for the degradation of various pollutants (methylene blue (MB), 44 Congo red (CR), ciprofloxacin (CIP), etc.) under UV/visible light irradiation. This work will also bring understanding regarding the kinetics involved in the photodegradation of the pollutants. Accordingly, the doping technique with lanthanides proved to be very useful since the photocatalytic activities revealed rate constants of the order of 10-2 min-1 . Through this work, it was also highlighted the synergistic effect of the most important factors such as the initial concentration of pollutants (mg/L) and the dose of catalysts (% w/v) on the photodegradation performance. Moreover, the presence of a small amount of lanthanide dopants induced pollutant removal efficiency up to 100%. It has to be mentioned that, all photocatalysts displayed excellent reusability even after 5 cycles of use under identical conditions.

Acknowledgment. This research was partially supported by CF23/ 14 11 2022 financed by the Ministry of Research, Innovation and Digitalization in Development of a program to attract highly specialized human resources from abroad in research, development, and innovation activities within the – PNRR-III-C9- 2022 – I8 PNRR/2022/Component 9/investment 8. HMU contribution to this work was partially supported by NATO Science for Peace and Security Programme, grant G5868.

T3-O1: A homogenisation technique describing the radiofrequency behavior of rare-earth doped ZnO/graphene nanocomposites

T. Sandu1 , M. Gologanu1 , M. Suchea1,3, O. T. Nedelcu1 , P. Pascariu1,2,3, E. Koudoumas1,3,4

National Institute for Research and Development in Microtechnologies – IMT Bucharest, Voluntari-Bucharest, Romania
Petru Poni Institute of Macromolecular Chemistry, Iaşi, Romania
Center of Materials Technology and Photonics, School of Engineering, Hellenic Mediterranean University, Heraklion, Greece
Department of Electrical and Computer Engineering, School of Engineering, Hellenic Mediterranean University, Heraklion, Greece

ZnO is of real interest due to its low-cost synthesis and its potential aplications not only in photochemical processes but also in optoelectronics and photovolaics [1]. Having a direct but wide band gap (around 3.4 eV) and a large quantum efficiency, it posseses real challenges when it comes to ambipolar doping: easy n-doping, but challenging p-doping [2]. In this respect we were able to synthesize novel ZnO materials doped with rare earth dopants: Er, La, Sm [3]. Furthermore, in order to increase electrical conductivity, the new compounds were mixed with graphene (vol. 1%) to obtain nanocomposites for EMI shielding applications. The radiofrequency behavior of these nanocomposites was probe in frequency and temperature between 1 Hz and 1 MHz and between -150º C and 200º C, respectively. Employing a two-stage homogenization procedure like those used in Refs. 4,5,6 we find the electric properties of both the doped ZnO and graphene. Our analysis has shown us that although all three dopants (Er, La, Sm) increase the electrical conductivity of ZnO, they induce deep level impurity states in the band gap of ZnO. In addition, the graphene filler does not reach the percolation threshold, such that the EMI shielding 57 for these materials is efficient below 1MHz and is made only by reflection.

Acknowledgments. IMT contribution was partially financed by the Romanian Ministry of Research, Innovation and Digitization through “MICRO-NANO-SIS PLUS” core Programme and partially supported by PNRR/2022/C9/MCID/I8 CF23/14 11 2022 contract 760101/23.05.2023 financed by the Ministry of Research, Innovation and Digitalization in “Development of a program to attract highly specialized human resources from abroad in research, development, and innovation activities” within the – PNRR-IIIC9-2022 – I8 PNRR/2022/Component 9/investment 8.

T3-O2: Nanocomposite RE:ZnO/Graphene with enhanced electrical and dielectric properties

C. Pachiu1 , P. Pascariu1,2,3 , 1C. Romanitan, 1O. N. Ionescu, 1T. Sandu, 1M. Gologanu, 1 I. V. Tudose, 1,2M.P. Suchea, 1,2E. Koudoumas 1

National Institute for Research and Development in Microtechnologies – IMT Bucharest, Voluntari-Bucharest, ROMANIA
University of Bucharest, Faculty of Physics, Magurele, Romania.
Petru Poni Institute of Macromolecular Chemistry, Iaşi, Romania
Center of Materials Technology and Photonics, School of Engineering, Hellenic Mediterranean University, Heraklion, Greece;
Department of Electrical and Computer Engineering, School of Engineering, Hellenic Mediterranean University, Heraklion, Greece 6Chemistry Department, University of Crete, Heraklion, Greece

Novel RE:ZnO /Graphene (RE: Er, La, Sm) nanocomposite materials obtained using a two stages method: electrospinning of precursor solutions followed by calcination at 600 o C (for 2 hours in N2 medium). The detailed morphologic, structural, and compositional analysis of samples revealed that this kind of doping have a strong effect in all materials parameters. The dielectric properties of ZnO:RE/Graphene (RE: Er, La, Sm) nanocomposite materials were analyzed in the frequency range of 1 Hz to 106 Hz and temperature between -150 o C and +200 o C and their specific parameters were determined. It was observed that the newly developed materials ZEG, ZLG, ZSG present a quite interesting behavior regarding their conductivity versus frequency variations: the measurements presented a considerable increase in conductivity for higher frequencies and temperatures.

Fig. 1. High entropy alloys: a) SEM microstructure; b) particle size distribution.

Acknowledgments. This research was partially supported by CF23/ 14 11 2022 financed by the Ministry of Research, Innovation and Digitalization in Development of a program to attract highly specialized human resources from abroad in research, development, and innovation activities within the – PNRR-III-C9-2022 – I8 PNRR/2022/Component 9/investment 8.

T7-SO10: Pure and La doped ZnO-graphene nanocomposite materials for EM shielding applications

M. Suchea1,2, P. Pascariu1,2,3, C. Romanitan1 , O. Brincoveanu1 , C. Pachiu1 , I. Mihalache1, D. Manica 1 , M. Stoian1 , R. Gavrila1 , A. Dinescu1 , R. Muller1 , O. N. Ionescu1, E. Koudoumas1,2

National Institute for Research and Development in Microtechnologies-IMT Bucharest, Bucharest, Romania
Center of Materials Technology and Photonics, School of Engineering, Hellenic Mediterranean University, Heraklion, Greece
Petru Poni Insititute of Macromolescular Chemsitry, Iasi, Romania

Recently, signifcant progress have been made in EM shielding applications of carbon materials, mainly due to their high conductivity and permittivity, including carbon black, carbon nanotubes, carbon fibers, porous carbon, and graphene. However, the high refective characteristics hamper their performance for effective electromagnetic (EM) waves absorption. Composite materials structure can effectively adjust the relative complex permittivity of those materials to realize relatively low e’ and intermediate e’’, which are necessary for better impedance match and higher dielectric loss [1-4]. Nanosized zinc oxide (ZnO) with low dielectric constants are also promising for EM waves attenuation due to their small crystal size and corresponding increase in specific surface area, which stand up for more polarization effects. Furthermore, the dielectric properties of composites extremely depend on the interface interaction between absorbing phases. Therefore, compared to simple hybrid structures, structured nanocomposites based on carbon allotropes and nanosized pure and doped ZnO could be considered as an effective strategy to adjust impedance match and enhance EM wave attenuation by adequately tunning the nanocomposite semiconductor bandgap. The present work 218 presents preliminary results of fabrication of pure and La doped nano ZnO/graphene nanocomposites materials by electrospinning-calcination method for EM shieling applications. SEM, XRD, EDX, SPM, UV_VIS and Raman spectroscopy methods were used for characterization of structure and morphology as well as optical and electrical properties of grown materials. Further studies of their EM shielding performance are ongoing.

Acknowledgements. This research was partially supported by CF23/ 14 11 2022 financed by the Ministry of Research, Innovation and Digitalization in Development of a program to attract highly specialized human resources from abroad in research, development, and innovation activities within the – PNRR-III-C9-2022 – I8 PNRR/2022/Component 9/investment 8.

PAMS-SO14: Doped ZnO thin films for sensing applications

M. Manica1,2, S. Antohe2 , I. V. Tudose3 , P. Pascariu1,4, C. Pachiu1 , C. Romanitan1 , O. Brincoveanu1 , R. Gavrila1 , E. Koudoumas1,3 and M.P. Suchea 1,3*

National Institute for Research and Development in Microtechnologies (IMTBucharest), Bucharest, Romania
University of Bucharest, Faculty of Physics, Magurele, Romania
Center of Materials Technology and Photonics, Hellenic Mediterranean University, Heraklion, Greece
Petru Poni Institute of Macromolecular Chemistry, Iaşi, Romania

Transparent oxide materials have attracted increased attention due to the wide spectrum of applications. One of the most requested semiconductors, in this sense, is zinc oxide (ZnO), because it can be obtained by various methods at a relatively low cost and has a wide field of applications in electronics, optoelectronics, and medicine. Many studies have been based on the doping of ZnO with different metal ions (Cr, La, Sm, Fe, Al) to improve different properties among which we mention here: the electrical conductivity, the optical, magnetically, and photocatalytic properties, etc, [1, 2, 3-6]. Zinc oxide thin films doped with Al, Fe, Cr, Sm, and La were deposited using the spray pyrolysis method. The structural and optical properties were characterized by X-ray diffraction (XRD), scanning electron micrography (SEM), Raman characterization, UV-Vis spectroscopy, and photoluminescence spectroscopy. It was observed that with the increase in the concentration of the dopant material, the crystallite sizes determined by the Scherrer and Williams Hall methods vary considerably. Also, a high optical transparency of 88-98% was observed in the visible range of the electromagnetic spectrum, the highest value being recorded for iron, this parameter depends on the dopant concentration. The structural and 258 electrical properties can be varied and controlled by doping the oxide with various metals, depending on the properties one wants to obtain. The visible emission of ZnO, which usually arises from anionic vacancies, is very sensitive to hole scavengers. The emission is quantitatively quenched by hole scavengers such as iodide ions [3-6].

PAMS-SO15: Contributions to the study of materials component for photovoltaic cells based on AIIBVI compounds.

D. Manica, 2L. Ion, 2V.-A. Antohe , 2S. Iftimite, 1,2 M. Manica, 2,3S. Antohe

National Institute for Research and Development in Microtechnologies – IMT Bucharest, Voluntari, Romania
University of Bucharest, Faculty of Physics, Magurele, Ilfov, Romania.
Academy of Romanian Scientists, Bucharest, Romania.

One of the major problems of mankind is the supply of energy, causing the intensification of research in the direction of the development of renewable and non-toxic energy sources. The 2nd generation of solar cells remains in the spotlight, with thin-film structures achieving efficiencies comparable to those of 1st generation structures and offering the advantage of large-area, lightweight structures with fabrication flexibility on different substrates and being more suitable in applications spatial. Zinc oxide (ZnO) is a binary AIIBVI compound that exhibits specific semiconducting characteristics. Group III materials such as aluminium, gallium and indium are frequently used as dopants to improve both the electrical and optical behavior [1] of zinc oxide. Indiumdoped zinc oxide (IZO) thin films are used in various modern technologies, depending on the growth conditions, can be used as a window layer and help facilitate electrical charge transfer, and can be used directly in multilayer solar cells [2]. The use of ZnS, ZnSe as replacement materials for classical CdS-n-type window layers in the preparation of CdTe-based solar cells has also shown great promise [3]. Thin layers of zinc telluride (ZnTe) are used in various modern technologies, due to its characteristics obtained in the deposition process, such as: low resistivity, high transparency in the visible spectrum, etc. [4]. It can be used as a p-type intermediate material in 260 CdTe type II solar cells [5] in multilayer devices. The protection of the structures can be achieved by using an Al2O3 layer, which is useful for passivating the photovoltaic cells and improving their performance. The aim of this research was to develop alternative materials that are environmentally friendly and combine low cost, durability, ease of production and efficiency for photovoltaics with applications in various fields.

PAMS-SO16: Vanadium pentoxide thin films for potential use in gas sensors

A. G. M. Popescu1,2 , I. V. Tudose3 , C. Pachiu 1 , C. Romanitan1 , O. Brincoveanu1 , R. Gavrila1 , I. Mihalache1 , E. Koudoumas1 , M.P. Suchea1,3

National Institute for Research and Development in Microtechnologies-IMTBucharest, Bucharest, Romania
National University of Science and Technology POLITEHNICA Bucharest, Bucharest, Romania;
Center of Materials Technology and Photonics, Hellenic Mediterranean University, Heraklion, Greece

Vanadium pentoxide (V2O5) thin films are highly regarded in gas sensing technology due to their exceptional properties. With rapid response, excellent recovery times, and stability, they lead in meeting the increasing need for efficient gas detection across diverse environments [1]. Spray pyrolysis involves the deposition of a precursor solution containing V2O5 onto a heated substrate by precisely controlling parameters like precursor concentration and spray rate. This method allows the deposition of thin films with excellent sensitivity suitable for use in gas sensors for detecting trace gases in complex environments [2]. V2O5 thin films are versatile, detecting a wide range of gases vital for environmental monitoring and workplace safety, including volatile organic compounds (VOCs), ammonia (NH3), nitrogen dioxide (NO2), and ozone (O3). Their structure allows rapid, accurate detection even at low concentrations, essential for early warnings and pollution control. Integrated into gas sensors, these films offer exceptional stability, enabling continuous, reliable real-time monitoring. In gas sensing applications, characterizing V2O5 thin films is vital for optimizing performance. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to to study the 263 crystalline structure and surface morphology of V2O5 thin films grown by spray pyrolysis onto glass and ITO coated substrates from sodium metavanadate precursor solutions. An example of a serie of films grown form 6, 9 and 10 ml precurisor solution, therefore having different thickness, surface morphology is shown in figure 1.

Figure 1. a-c. SEM images of a serie of films grown form a)6ml, b)9ml, and c) 10-ml precursor solution.