Project leader: Dr. Nicoleta Preda
Post-doctoral researcher: Dr. Andreea Costas
Post-doctoral researcher: Dr. Alexandru Evanghelidis
Post-doctoral researcher: Dr. Marcela Socol
Post-doctoral researcher: Dr. Irina Zgura
Experienced researcher: Dr. Monica Enculescu
Doctoral student: Drd. Daciana Botta

The project is focused on designing bio-inspired semiconducting fibers using natural polymers as bio-templates, further these semiconducting webs being integrated as fiber networks or as single fibers in field effect transistors (FETs) devices which can be applied in chemical sensing area. Thus, using eggshell membranes (ESM) and electrospun egg albumen (EA) as bio-templates,
semiconducting fibers based on metal oxides or/and metal sulfides (as monocomponents or as composites) will be prepared by immersion, electrospinning and calcination techniques. The obtained bio-inspired semiconducting fibers will be characterized by morphological, structural and optical point of view. Further, FETs based on semiconducting fiber networks and FETs based on single semiconducting fibers will be fabricated by combining physical deposition techniques (radio frequency magnetron sputtering, thermal vacuum evaporation) and lithography techniques (photolithography, electron beam lithography). Finally, the electrical performance of the FETs will be investigated after their exposure to various chemical vapours for evaluating the potential
applications of these devices in the chemical sensing field. The strategy used in the preparation of the bio-inspired semiconducting fibers can be regarded as a bio-inspired solution for fabricating electronic devices from renewable sources.

Stage I

The objective of the first stage - designing bio-inspired semiconducting fibers with specific properties involved the following experimental activities: i) obtaining EA webs with fiber structure by electrospinning and their characterization; ii) preparing semiconducting fibers using ESM and electrospun EA as bio-templates; iii) complex characterization of semiconducting fibers. The FESEM images evidenced that only few fiber structures were formed by electrospinning of egg albumen. In order to optimize the electrospinning process for achieving fiber webs, the solutions were prepared using polymers, which favour the formation of fiber-type structures and commercial albumin powder from eggs. The XRD, FTIR, TG, DTA and DSC investigations emphasized that the eggshell membranes, the powder obtained by drying the egg albumen and albumin powder from eggs have similar structural, vibrational and thermal properties. The influence of the experimental parameters (polymer type, solvent type, polymer concentration, protein concentration, humidity from the electrospinning chamber) on the morphological and structural properties of the electrospun protein fibers were evaluated by FESEM and FTIR measurements. Also, the influence of the bio-template origin on the replication process was analysed by using eggshell membrane (collagen) and flax fibers (cellulose) in obtaining an anorganic one based on zinc oxide fibers. The FESEM images and the XRD patterns showed that the specific architecture of each organic template was perfectly replicated in an anorganic one based on zinc oxide fibers. Further, the preparation of webs based on semiconductor fibers was achieved by: i) immersing the membranes in precursor solutions containing metal salts and further their calcination and ii) electrospinning the solutions containing polymer, albumin and metal salts and further their calcination. The thermal treatments were carried in different atmospheres (air, nitrogen, argon). The influence of the experimental parameters (bio-template type, metal salt type, calcination atmosphere) on the morphological, compositional and structural properties of the obtained inorganic webs was assessed by FESEM, EDX and XRD. Thus, the FESEM and the EDX images revealed a fiber-web morphology with an uniform distribution of component elements while the XRD patterns evidenced the formation of compounds such as semiconductor, metal:semiconductor or metal. In addition, the possibility to transform a metal oxide (zinc oxide) into metal sulfide (zinc sulphide) through a chemical reaction was evaluated, the XRD data proving the viability of this approach. The scientific results were disseminated in 1 article published in ISI journal (Q1) and 2 scientific communications (poster type) at international conferences.

Stage II

The objective of the second stage - fabricating FETs based on bio-inspired semiconducting fibers networks involved the following experimental activities: i) optimizing the experimental parameters involved in the electrospinning, immersion and calcination steps processes for obtaining semiconducting fibers with specific properties; ii) dispersing the prepared semiconducting fiber networks in isopropyl alcohol by ultrasonication in order to deposit them as layers based on fiber networks on Si/SiO2 substrates by spin-coating; iii) depositing different metallic electrodes on the semiconducting fiber networks through a shadow mask with various geometries by radio frequency magnetron sputtering or thermal vacuum evaporation in order to obtain adequate and optimized Ohmic metallic contacts; iv) electrical characterization of FETs based on the fiber networks for determining the FETs key parameters. Hence, the influence of some experimental parameters such as the concentration and type of the precursor salt, electrospinning time, calcination time or calcination temperature on the morphological properties of the semiconducting fibers was investigated by FESEM. In addition, the structural and optical properties of the oxide fibers were analyzed by XRD, R and PL. The transformation of the fibers based on metal oxide (zinc oxide or copper oxide) into metal sulfide (zinc sulfide or copper sulfide) through a chemical reaction with a sulfur precursor was also tested. In order to evaluate the influence of the morphology and size of the zinc oxide structures, properties controlled through the preparation method, a comparative study was carried out, structures obtained by different methods: fibers (immersion and calcination), particles (chemical precipitation), flowers (burdock extract bio-assisted chemical precipitation) and wire (thermal oxidation in air) being investigated. The XRD diffractograms of the samples showed that the transformation of zinc oxide into zinc sulfide can be partial or total, this depending to the size of the structures and the temperature involved in their preparation methods. In the case of the copper oxide fibers, the reaction with the sulf precursor results in the transformation of the copper oxide into copper sulfide. In order to deposit the semiconducting fibers on Si/SiO₂ wafers, the powders containing the fiber webs were dispersed by ultrasonication in isopropyl alcohol, the FESEM images of the obtained samples showing the appearance of a fragmentation effect leading to the break of the webs. Taking into account that the FESEM images evidenced that, regardless of the bio-template type - natural membrane or electrospun web, semiconductor fiber networks can be obtained in the form of the adherent layers to the Si/SiO₂ substrates. In order to perform the electrical measurements, the fiber networks were obtained directly on Si/SiO₂ wafers containing interdigitated metallic electrodes. The major advantage of using this type of substrate consists in the fact that the transport of the charge carriers takes place by percolating through the junctions formed by the semiconductor fibers on the surface of the system of interdigitated metallic electrodes, the electrical circuit being closed without a need for additional contacting steps. Thus, field effect transistors based on semiconducting networks formed by bio-inspired metal oxide fibers were developed. The scientific results were disseminated in 3 articles published in ISI journal (Q1/Q2) and 6 scientific communications (4 oral and 2 poster) at international conferences and 1 patent request completed at State Office for Inventions and Trademarks.

Papers published in ISI journals:

1. Hierarchical flax fibers by ZnO electroless deposition: tailoring the natural fibers/synthetic matrix interphase in composites
N. Preda*, A. Costas*, F. Sbardella, M. C. Seghini, F. Touchard, L. Chocinski-Arnault, J. Tirillo, F. Sarasini
Nanomaterials, 12, 2765-15, 2022

2. Macrocyclic compounds:metal oxide particles nanocomposite thin films deposited by MAPLE
M. Socol*, N. Preda*, C. Breazu, A. Costas*, O. Rasoga, G. Petre, G. Popescu-Pelin, S. Iftimie, A. Stochioiu, G. Socol, A. Stanculescu
Materials, 16, 2480-17, 2023

3. Burdock-derived composites based on biogenic gold, silver chloride and zinc oxide particles as green multifunctional platforms for biomedical applications and environmental protection
I. Zgura*, N. Badea, M. Enculescu*, V.-A. Maraloiu, C. Ungureanu, M.-E. Barbinta-Patrascu
Materials, 16, 1153-24, 2023

4. Silver nanoparticles decorated ZnO–CuO core–shell nanowire arrays with low water adhesion and high antibacterial activity
A. Costas*, N. Preda*, I. Zgura*, A. Kuncser, N. Apostol, C. Curutiu, I. Enculescu
Scientific Reports, 13, 10698-15, 2023

Scientific communications at international conferences:

1. Bio-templated synthesis of interwoven fibers based on ZnO and ZnS by replicating eggshell membranes
A. Costas*, N. Preda*, M. Socol*, I. Zgura*, I. Enculescu
RICCCE 22 – 22nd Romanian International Conference on Chemistry and Chemical Engineering, 7-9 September 2022, Sinaia, Romania
Poster (abstract no. 36)

2. Bio-inspired fiber webs based on metal oxides by replicating eggshell membranes
A. Costas*, N. Preda*, A. Evanghelidis*, M. Enculescu*, I. Enculescu
12th International Advances in Applied Physics & Materials Science Congress & Exhibition (APMAS), 13-19 October 2022, Oludeniz, Turcia
Poster (abstract no. 2144)

3. Synthesis of 3D metal oxide fiber networks using polymer-egg protein electrospun fibers as templates
A. Evanghelidis*, N. Preda*, A. Costas*, M. Socol*, I. Zgura*
40th E-MRS Spring Meeting, 29 May-2 June 2023, Strasbourg, Franta
Oral (abstract no. 1707)

4. Three-dimensional fibrous structures based on polymers as templates for copper oxide fiber webs
I. Zgura*, N. Preda*, A. Evanghelidis*, A. Costas*, M. Socol*, D. Botta*
3rd International Conference on Bioengineering and Polymer Science (BPC), 7-10 June 2023, Bucuresti, Romania
Poster (abstract no. 23)

5. Natural templates-assisted synthesis of ZnO fibrous architectures
I. Zgura*, N. Preda*, A. Costas*, M. Socol*, D. Botta*
21st International Balkan Workshop on Applied Physics and Materials Science (IBWAP), 11-14 July 2023, Constanta, Romania
Poster (abstract no. S1-P3)

6. Hierarchical semiconducting fiber networks by a straightforward bio-templating approach
A. Evanghelidis*, N. Preda*, A. Costas*, I. Zgura*, M. Socol*
20th International Conference on Advanced Nanomaterials (ANM), 26-28 July 2023, Aveiro, Portugalia
Oral (abstract no. 11)

7. Designing electrospun polymer fiber mat as templates for developing hierarchical inorganic architectures
A. Evanghelidis*, N. Preda*, A. Costas*, M. Socol*, I. Zgura*
15th International Conference on Physics of Advanced Materials (ICPAM), 19-26 November 2023, Sharm El-Sheikh, Egipt
Oral (abstract no. T9-O1)

8. Bio-mediated synthesis approach for designing inorganic 3D structures based on zinc oxide and gold nanoparticles
I. Zgura*, N. Preda*, M. Socol*, A. Costas*, M.E. Barbinta-Patrascu, A. Evanghelidis*, M. Enculescu*
15th International Conference on Physics of Advanced Materials (ICPAM), 19-26 November 2023, Sharm El-Sheikh, Egipt
Oral (abstract no. T5-SO1)

OSIM patent request:

1. Procedeu de obtinere a unor retele fibroase tridimensionale formate din nanoparticule pe baza de aur si oxid de zinc utilizand bio-sabloane de tip membrana naturala extrasa din coji de ou
N. Preda*, A. Costas*, M. Socol*, I. Zgura*, A. Evanghelidis*
no. A/00471, 2023

^*project team members