NIMP| Mirela VADUVA, Author at NIMP

Education

2014-2018-Phd in Physics, Faculty of Physics, University of Bucharest, Romania, Department of Optics-Spectroscopy- Plasma and Lasers

2010-2012-Master in Chemistry, Faculty of Chemistry, University of Bucharest, Romania, Department of Chemical pollution of the environment

2007-2010-Graduate of Chemistry, University of Bucharest, Romania, Department of Environmental Chemistry

Positions

2007-2012-student at Faculty of Chemistry, University of Bucharest

Pathways for preparation and characterization methods of semiconductors, such as TiO2, improved with transition and noble metals, used in photocatalysis, in photo-production of hydrogen energy

09.2012-05.2014-trainee research assistant at National Institute of Materials Physics, laboratory of Optical Processes in Nanostructured Materials

• Synthesis of conjugated polymers like poly (para-phenylene vinylene) and its derrivatives, synthesis of composite materials based on PPV and carbon nanoparticles as carbon nanotubes and graphene; investigation of optical properties of this type of polymers and composite materials using Raman, IR, UV-Vis spectroscopy together with luminescence and photoconductive studies

• Synthesis of carbon nanotubes and graphene using CVD method

05.2014-01.2019-research assistant at National Institute of Materials Physics, laboratory of Optical Processes in Nanostructured Materials

• Synthesis and characterization of materials composites such as PPV/(M+S)-SWNTs, PPV/M-SWNTs, PPV/S-SWNTs, where (M+S)-SWNTs are a mixture of metallic (33% ) and semi-conducting nanotubes (66%), M-SWNTs and S-SWNTs represent the carbon nanotubes highly separated in metallic tubes and semi-conducting tubes, respectively.

• Synthesis and investigation of optical properties of PPV/RGO composites

01.2019-at present-scientific researcher at National Institute of Materials Physics, laboratory of Optical Processes in Nanostructured Materials

• Synthesis of conjugated polymers and composite materials

• Investigation of optical properties of nanostructured materials

• Review writing about composites based on conducting polymers (PANI, PEDOT, PPy) and graphene derivates used for electrod modification with application in sensors for uric acid electrochemical detection (functionalization between components inside composite, chemical, electrochemical and vibrational properties, parameters that describe the sensor performance and the influence of synthesis method and interaction between components over the selectivity and sensitivity of the sensors)

• Documentaries and review writing about composites based on conducting polymers (PANI, PEDOT, PPy) and carbon nanostructures (carbon nanotubes, graphene and graphene derivates) used as counter electrode material in Dye sensitized solar cells (DSSCs) (functionalization between components inside composite, chemical, electrochemical and vibrational properties, parameters that describe the CE and DSSCs performance and the influence of synthesis method and interaction between components over the DSSCs performance)

Expertize

- Synthesis of photocatalyst based on TiO₂ and TiO₂-SiO₂dopped with metals and non-metals, tested in hydrogen production from waste water;

- Test and characterization of photocatalyst using characterization techniques such as absorption spectroscopy in infrared field (IR), ultraviolet-visible (UV-Vis) absorption spectroscopy, Raman spectroscopy, gas chromatography coupled with mass spectrometer (GC-MS);

- Chemical synthesis of conducting polymers such as poly(para-phenylenevinylene) and its derrivates

- Synthesis using Catalytic Vapour Deposition (CVD) of multiwall carbon nanotubes and graphene;

- Investigation of optical properties of conducting polymers (CPs) and composites based on CPs and graphene, respectively graphene derrivates and carbon nanotubes using UV-Vis-NIR, Raman and FTIR spectroscopy, luminescence and photoconductive studies

Books

Book chapter

- Recent progress in the photoluminescence properties of composites based on conjugated polymers and carbon nanoparticles, Baibarac M., Ilie M., Matea A., Dăescu M., Lefrant S., 2018, Photoluminescence : Advances in Research and Applications, pp.133-166

Patents

- Procedee de preparare si utilizare ale noilor forme cristaline ale 6-(3-metil-5-nitroimidazol-4-il)sulfanil-9H-purinei (Processes for preparation and employment of new crystalline shapes of 6-(3-methyl-5-nitroimidazole-4-yl) sulphanyl-9H-purine) Manta Corina-Mihaela;Samohvalov Dumitru; Gherca Daniel; Baibarac Mihaela; Lungan Maria-Andrea; Smaranda Ion; Barbatu Adrian; Buhalteanu Lucian;Udrescu Adelina; Daescu Monica; Ilie Mirela; Toulbe N’Ghaya, BNA, No. A00516/28.08.2019, Derwent Primary Accession Number: 2020-27603U

Publications

1. Functionalization of Graphene Derivatives with Conducting Polymers and Their Applications in Uric Acid Detection

Authors: Vaduva, M; Baibarac, M; Cramariuc, O

Published: JAN 2023, MOLECULES, 28, 135, DOI: 10.3390/molecules28010135

In this article, we review recent progress concerning the development of sensorial platforms based on graphene derivatives and conducting polymers (CPs), alternatively deposited or co-deposited on the working electrode (usually a glassy carbon electrode; GCE) using a simple potentiostatic method (often cyclic voltammetry; CV), possibly followed by the deposition of metallic nanoparticles (NPs) on the electrode surface (ES). These materials have been successfully used to detect an extended range of biomolecules of clinical interest, such as uric acid (UA), dopamine (DA), ascorbic acid (AA), adenine, guanine, and others. The most common method is electrochemical synthesis. In the composites, which are often combined with metallic NPs, the interaction between the graphene derivatives-including graphene oxide (GO), reduced graphene oxide (RGO), or graphene quantum dots (GQDs)-and the CPs is usually governed by non-covalent functionalization through pi-pi interactions, hydrogen bonds, and van der Waals (VW) forces. The functionalization of GO, RGO, or GQDs with CPs has been shown to speed up electron transfer during the oxidation process, thus improving the electrochemical response of the resulting sensor. The oxidation mechanism behind the electrochemical response of the sensor seems to involve a partial charge transfer (CT) from the analytes to graphene derivatives, due to the overlapping of pi orbitals.

2. Photoconductive Behavior of the PPV/RGO Composites: Insights of Charge Transfer Process

Authors: Ilie, M; Dragoman, D; Baibarac, M

Published: JUL 2019, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 256, DOI: 10.1002/pssb.201800392

The paper deals with a study of composites based on poly(p-phenylenevinylene) (PPV) and reduced graphene oxide (RGO) in terms of photoconductivity and photocurrent (PC) dynamics in charge-discharge cyclic processes. The explanation for the photoconductive behavior is built with the support of DeVore and Onsager theories. Scanning samples in both directions involves charge transport, to and from, available energy states called defect centers. The existence of these centers is confirmed by a decrease in the composite bandgap caused by the RGO localized states which are situated slightly above the first HOMO level in the PPV bandgap. The contribution of RGO to the photoconductive properties of PPV is revealed through a photocurrent value with two orders of magnitude higher than for PPV.

3. The spectrochemical behavior of composites based on poly (para-phenylenevinylene), reduced graphene oxide and pyrene

Authors: Ilie, M; Baibarac, M

Published: OCT 2017, OPTICAL MATERIALS, 72, 146, DOI: 10.1016/j.optmat.2017.06.002

A new composite material based on poly (para-phenylenevinylene) (PPV), pyrene (Py) and reduced graphene oxide (RGO) is synthesized using thermal conversion route. The properties of this material are investigated by Raman scattering, photoluminescence (PL), infrared (IR) and ultraviolet visible (UV-Vis) spectroscopy. Adding Py at PPV precursor solution (PPV PS) containing RGO, yields to important modifications in both vibrational and electronic properties of these composites. The presence of Py into PPV matrix determines a blue shift of PPV PL. According to Raman and IR studies, PPV is non-covalently functionalized with Py which interacts forward with RGO through pi-pi interactions causing an important modification into the polymer chains conjugation length. (C) 2017 Elsevier B.V. All rights reserved.

4. Infrared dichroism studies and anisotropic photoluminescence properties of poly(para-phenylene vinylene) functionalized reduced graphene oxide

Authors: Baibarac, M; Ilie, M; Baltog, I; Lefrant, S; Humbert, B

Published: 2017, RSC ADVANCES, 7, 6942, DOI: 10.1039/c6ra26445j

Two methods were used for the synthesis of composites based on reduced graphene oxide (RGO) and poly(para-phenylene vinylene) (PPV) in un-doped and doped state, respectively, i.e. the annealing conversion (AC) of the PPV precursor solution (PS) at 300 degrees C and the electropolymerization (E) of alpha, alpha, alpha', alpha'-tetrabromo-p-xylene. In the case of the E method, a decrease in the distyrylbenzene (DSB) weight onto the RGO sheet surface in favor of PPV in doped state is demonstrated by the s and p polarized IR spectroscopy. The change of the orientation angle of the transition dipole moment vector for the IR bands at 835 and 964 cm(-1), in the case of the AC of the PPV PS, is a result of the p-p* interactions between the phenyl groups of PPV and the RGO sheets. The photoluminescence (PL) bands at 2.42 and 2.26 eV indicate the formation of PPV macromolecular chains (MCs) with lengths of 5 and 710 repeating units (RUs), respectively. The anisotropic PL studies performed on the composites RGO/PPV in un-doped and doped state, respectively, highlight an increase of the wrapping angle of RGO sheets with PPV MCs with lengths of 5 RUs, when graphene concentration increases.

5. Optical properties of single-walled carbon nanotubes functionalized with copolymer poly(3,4-ethylenedioxythiophene-co-pyrene)

Authors: Baltog, I; Baibarac, M; Smaranda, I; Matea, A; Ilie, M; Mevellec, JY; Lefrant, S

Published: DEC 2016, OPTICAL MATERIALS, 62, 611, DOI: 10.1016/j.optmat.2016.11.005

Optical properties are reported for composites based on single-walled carbon nanotubes (SWNT5) and copolymer poly(3,4-ethylenedioxythiophene-co-pyrene) (PEDOT-Py) prepared by chemical polymerization of two monomers in the presence of carbon nanotubes. A charge transfer between SWNT5 and the PEDOT-Py copolymer was demonstrated by Raman scattering. The increase in the relative intensity of the Raman lines peaked at 440-577 cm(-1), which were assigned to the ethylenedioxy ring vibrational modes, indicated a significant hindrance steric in the case of the composites based on the PEDOT-Py copolymer and metallic SWNTs. The increase in the absorbance of IR band peaked at 984 cm(-1) occurred simultaneously with the disappearance of the IR band at 1639 cm(-1). This finding was a consequence of the formation of new covalent bonds between SWNTs and the thiophene and benzene rings of the repeating units of the PEDOT-Py copolymer. The photoluminescence (PL) quenching process of the PEDOT-Py copolymer was induced by semiconducting SWNTs. The PL quenching of PEDOT-Py copolymer in the presence of SWNT5 was. demonstrated based on the energy level diagrams of the two constituents of the PEDOT-Py/SWNTs composite material. (C) 2016 Elsevier B.V. All rights reserved.

6. Influence of Single-Walled Carbon Nanotubes Enriched in Semiconducting and Metallic Tubes on the Vibrational and Photoluminescence Properties of Poly(para-phenylenevinylene)

Authors: Baibarac, M; Baltog, I; Ilie, M; Humbert, B; Lefrant, S; Negrila, C

Published: MAR 17 2016, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 5705, DOI: 10.1021/acs.jpcc.5b11198

A new synthesis method based on the electrochemical reduction of alpha,alpha,alpha',alpha'-tetrabromo-p-xylene in the presence of single-walled carbon nanotubes (SWNTs) is used to obtain composites of carbon nanotubes (CNTs) functionalized with poly(para-phenyl-enevinylene) (PPV). To separate the effects of metallic and semiconducting CNTs on their interaction with PPV, the experiments are carried out with SWNTs enriched in semiconducting (S, 99%) and metallic (M, 98%) tubes. Significant changes in the relative intensity and shift of the radial breathing vibrational mode are reported in the Raman spectra of the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) entities and SWNTs enriched in M tubes (98%) that result from the electrofunctionalization with PPV. This different behavior originates in the noncovalent and covalent functionalization of SWNTs enriched in M and S SWNTs tubes with PPV, respectively. A gradual decrease in the absorption of the infrared (IR) bands of PPV situated in the spectral range of 750-1000 cm(-1) as a result of the increase of the polymer weight on the blank Au support is reported. The electrofunctionalization of the as-prepared SWNTs induces position changes of the PPV IR absorption bands. In the presence of S-enriched SWNTs, a significant increase in the absorbance of the two IR bands peaked at 1452 and 1471 cm(-1), which are assigned to the vibrational modes of the phenyl ring stretching and the quinoid structure of the PPV, respectively, is reported. This results from the covalent bonding of the PPV macromolecular chains onto the surface of the SWNTs enriched in S tubes. Our results also demonstrate that the photoluminescence quenching effect reported for the PPV/SWNTs composites is due to the metallic nanotubes.

7. Anti-Stokes Raman spectroscopy as a method to identify metallic and mixed metallic/semiconducting configurations of multi-walled carbon nanotubes

Authors: Baibarac, M; Matea, A; Ilie, M; Baltog, I; Magrez, A

Published: 2015, ANALYTICAL METHODS, 7, 6230, DOI: 10.1039/c5ay01281c

SERS studies were performed on films of two families of multi-wall carbon nanotubes (MWCNTs) under an excitation light of 514.5 nm and 647.1 nm. These included Aldrich-MWCNTs, which alternate semiconducting and metallic tubes and M-MWCNTs that contain only metallic tubes obtained by water assisted catalytic chemical vapour deposition (CCVD). The two families of MWCNTs reveal similar spectra in the Stokes branch, which feature an increasing Raman intensity when the glass substrate is replaced with an Au or Ag substrate, indicating a (surface enhanced Raman scattering) SERS mechanism. In the anti-Stokes branch, despite an enhancement of approximately 100 times compared to the predictions of the Boltzmann law, only Aldrich-MWCNTs exhibit a Raman spectrum with an intensity that increases as a result of the change in the glass substrate to Au or Ag, a fact that is revealed by the signature of the SERS process. The invariance of the Raman intensity in the anti-Stokes branch as a result of the change of the substrate is characteristic of M-MWCNTs and results from a Raman light scattering process that takes place only within the skin depth of the metallic structure.

8. Optical Properties of Single-Walled Carbon Nanotubes Functionalized with Poly(2,2 '-bithiophene-co-pyrene) Copolymer

Authors: Smaranda, I; Baibarac, M; Ilie, M; Matea, A; Baltog, I; Lefrant, S

Published: 2015, CURRENT ORGANIC CHEMISTRY, 19, 661, DOI: 10.2174/1385272819666150311231454

The photoluminescent (PL) properties of composites based on single-walled carbon nanotubes (SWNTs) and poly(2,2'-bithiophene-co-pyrene) (PBTh-Py), prepared by in situ chemical polymerization of the two monomers in the presence of carbon nanotubes, are reported. We demonstrate that the functionalization of SWNTs with PBTh-Py copolymer is revealed through a gradual quenching process of PL with the increase of SWNT content (semiconducting component) in the composite mass. FTIR spectroscopy indicates the existence of several steric hindrance effects that originate in the covalent functionalization of SWNTs with PBTh-Py copolymer. The film deposition of PBTh-Py copolymer and PBTh-Py/SWNTs composite onto rough Au supports induces changes in the FTIR spectrum, which originate in an adsorption mechanism caused by the preferential orientation of molecules on the metallic support. Surface-enhanced Raman scattering (SERS) spectroscopy reveals the side-wall functionalization of SWNTs with PBTh-Py copolymer by changes in the shapes, peak position and relative intensities of different Raman lines.

9. Spectroelectrochemical properties of the poly[(2,5-bisoctyloxy)-1,4-phenylenevinylene]/single-walled carbon nanotube composite

Authors: Baibarac, M; Baltog, I; Srnaranda, I; Ilie, M; Scocioreanu, M; Mevellec, JY; Lefrant, S

Published: SEP 2014, SYNTHETIC METALS, 195, 285, DOI: 10.1016/j.synthmet.2014.06.010

Using surface-enhanced Raman scattering (SERS) and photoluminescence (PL) studies, new data concerning the electrochemical oxidation both of poly[(2,5-bisoctyloxy)-1,4-phenylene-vinylene] (BO-PPV) and the BO-PPV/HIPCO single-walled carbon nanotubes (SWNTs) composite are presented in this paper. The SERS studies performed at the excitation wavelengths of 752 nm and 532 nm of the BO-PPV/SWNTs composite that ensure the resonant excitation of the semiconductor and metallic nanotubes, respectively, reveal that the mixing of the two constituents results, on the one hand, in an isolation of semiconducting nanotubes from the bundles containing both metallic and semiconducting tubes and, on the other hand, in a functionalization of metallic SWNTs with BO-PPV. The isolation of semiconducting SWNTs is demonstrated by the narrowing of the G band and the change of the ratio between the intensities of the Raman lines situated in the low-frequency range that are assigned to the radial breathing vibrational modes. An additional isolation of the semiconducting nanotubes from the SWNTs bundles is reported when an electro-oxidation of the BO-PPV/SWNTs composite was performed in the potential range of (0; +2) V vs. Ag/AgCl. According to the Fourier transformed infra-red (FTIR) spectra and the SERS studies performed at an excitation wavelength of 1064 nm, the chemical interaction of BO-PPV with HIPCO SWNTs reveals a charge transfer between the two constituents that leads to the formation of BO-PPV covalently functionalized SWNTs. The BO-PPV luminescence quenching effect induced by the presence of SWNTs that consists of a change in the relative intensities of the three PL bands of the polymer peaked at 1.73 eV, 1.9 eV and 2.07 eV is due to the metallic tubes. The appearance of a new emission band at 2.32 eV was regularly observed when electrochemical oxidation of the BO-PPV/SWNTs composite was performed in the potential range of (0; +2) V. The PL band at 2.32 eV corresponds to ClO4- ions, which compensates the positive charges of BO-PPV generated during the electrochemical doping process. (C) 2014 Elsevier B.V. All rights reserved.

10. Improving TiO2 activity in photo-production of hydrogen from sugar industry wastewaters

Authors: M. Ilie, B. Cojocaru, B V.I. Parvulescu, H. Garcia

Published: DEC 2011, International Journal of Hydrogen Energy, 36, DOI: 10.1016/j.ijhydene.2011.09.029

A series of TiO2 photocatalysts dispersed on SiO2, modified with metals (Mn, Cr, V) or nonmetals (N or S) or covered with Au nanoparticles were prepared by incipient wetness impregnation, impregnation with urea or thiourea, and deposition-precipitation, respectively. The photocatalysts where characterized by chemical analysis, X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DR-UV-Vis) and Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity was checked in the photo-generation of hydrogen from sugar solutions. The nature of the modifying species was found to influence the photoactivity and N and S led to more effective catalysts than metals. This behavior was attributed to the fact the N and S are less effective in forming recombination centers compared with the metals. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Dr. Mirela VADUVA

Scientific Researcher