2

II Jornada Franco-Brasileira Francisco Tourinho

15th and 16th March 2018 Brasília - Distrito Federal, Brazil

Auditorium - CDT/UnB Universidade de Brasília

Invited Speakers

Régine Perzynski (PHENIX, UPMC, Paris, France) Souad Ammar (ITODYS Université Paris Diderot, Paris, France)

Julian Geshev (UFRGS, Brazil) Gustavo Azevedo (LNLS/ UFRGS, Brazil)

Demétrio Antonio da Silva Filho (Instituto de Física, UnB, Brasília, Brazil) Jerome Depeyrot (Instituto de Física, UnB, Brasília, Brazil)

Jorlandio Felix (Instituto de Física, UnB, Brasília, Brazil) Mauro Pinheiro (FUP, UnB, Brasília, Brazil)

Oral Contributions

Franciscarlos da Silva (FUP, UnB, Brasília, Brazil) Rafael Gomes (Instituto de Física, UnB, Brasília, Brazil)

Guilherme Gomide (Instituto de Física, UnB, Brasília, Brazil) Thiago Fiuza (Instituto de Física, UnB, Brasília, Brazil)

Coordination

Alex Fabiano Cortez Campos (FUP, UnB, Brasília, Brazil)

Organizing Committee

Renata Aquino (FUP, UnB, Brasília, Brazil) Fábio Paula (Instituto de Física, UnB, Brasília, Brazil)

Leonardo Castro (Instituto de Física, UnB, Brasília, Brazil) Priscilla Coppola (FUP, UnB, Brasília, Brazil)

Cynara Kern (FUP, UnB, Brasília, Brazil) Rogelma Ferreira (UFRB, Bahia, Brazil)

Rachel Bezerra (Instituto de Física, UnB, Brasília, Brazil)

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CONTENTS

PREFÁCIO .................................................................................................................................... 4

PRÉFACE ...................................................................................................................................... 5

TIMETABLE ................................................................................................................................... 6

PROGRAM .................................................................................................................................... 7

INVITED TALKS ............................................................................................................................ 9

THERMODIFFUSION OF AQUEOUS FERROFLUIDS BASED ON CITRATE-COATED

NANOPARTICLES AND ITS ANISOTROPY UNDER A MAGNETIC FIELD (R. Perzynski) 10

SIRIUS, THE NEW BRAZILIAN SYNCHROTRON LIGHT SOURCE (G. Azevedo) ............. 11

GRAPHENE OXIDE AND ITS COMPOSITES AS FILMS AND OLFACTION APPLICATIONS

(M. F. P. da Silva) ................................................................................................................... 12

THE ROLE OF PINNED AND ROTATABLE SPINS ON THE EXCHANGE ANISOTROPY

FIELDS MEASURED IN CORE/SHELL FERRITE NANOPARTICLES (J. Depeyrot) ........... 13

ORGANIC SEMICONDUCTORS: NEW MATERIALS FOR A CHEAPER AND GREENER

ELECTRONICS (D. A. da Silva Filho) ................................................................................... 14

NEW PERSPECTIVES IN THE USE OF REMANENCE PLOTS TO DISTINGUISH BETWEEN

TYPES OF EXCHANGE COUPLING AND TO QUANTIFY SPIN DISORDER IN MAGNETIC

NANOSTRUCTURES (J. Geshev) ......................................................................................... 15

FACILE SHAPE-CONTROLLED FABRICATION OF NANOSTRUCTURES ON GLASSES:

SYNTHESIS, CHARACTERIZATION, AND APPLICATIONS (J. Felix) ................................. 16

IRONS OXIDE AND GOLD BASED MAGNETO-PLASMONIC CORE-SHELL

NANOPARTICLES. SYNTHESIS OPTIMIZATION, CHARACTERIZATION AND BIOMEDICAL

APPLICATIONS (S. Ammar) .................................................................................................. 17

ORAL CONTRIBUTIONS ............................................................................................................ 18

pH-DEPENDENT SURFACE PROPERTIES OF CARBON DOTS AQUEOUS DISPERSIONS

(T. Fiuza) ................................................................................................................................. 19

IS IT REALLY POSSIBLE TO CONTROL THE MAGNETIC PROPERTIES OF

NANOPARTICLES BY CHEMICAL COMPOSITION? (R. C. Gomes) ................................... 20

THERMAL DEPENDENCE OF MAGNETIC ANISOTROPY IN NONINTERACTIVE CORE-

SHELL CoFe2O4@-Fe2O3 NP ASSEMBLIES (G. Gomide) .................................................. 21

MAGNETIC PROPERTIES OF CoFe2O4/Fe2O3 AND NiFe2O4/Fe2O3 CORE/SHELL

PARTICLES (F. G. da Silva) .................................................................................................. 22

POSTERS ................................................................................................................................... 23

4

PREFÁCIO

Francisco Augusto Tourinho nasceu no estado de Minas Gerais no dia 10 de março de

1957. Iniciou seus estudos superiores na Universidade de Brasília onde fez bacharelado

(1978) e mestrado (1982) em Química. No ano de 1983, mudou-se para Paris na França

onde fez doutorado, tornando-se Docteur d’État ès Sciences Physiques pela Université

Pierre et Marie Curie – Paris 6 em 1988. Após seu retorno da França, iniciou sua carreira

acadêmica em 1989, como Professor Doutor do Instituto de Física da Universidade de

São Paulo e em seguida, em 1991, veio para o Instituto de Química da UnB. Fundou o

Grupo de Fluidos Complexos dessa universidade e sugeriu a realização periódica da

Conferência Internacional de Nanociência, Nanotecnologia e Nanobiotecnologia

(3NANO), cuja quarta edição foi realizada em Paris de 10 a 14 de dezembro de 2017,

após três edições na UnB. Foi ele quem introduziu a pesquisa de Ferrofluidos (líquidos

magnéticos) no Brasil. Foi também pioneiro da Cooperação bilateral entre a UnB e a

Université Pierre et Marie Curie (Sorbonne Universités – Paris/França), que se

consolidou por meio do programa de tese de Doutorado em cotutela. Hoje, na UnB, a

pesquisa em Líquidos Magnéticos permeia cinco Programas de Pós-Graduação e reúne

mais de 150 pesquisadores, professores doutores, alunos de Doutorado, Mestrado e

Iniciação Científica. Ainda, o Grupo que ele fundou (Grupo 3NANO – Laboratório de

Fluidos Complexos) integra o Instituto Nacional de Ciência e Tecnologia de Fluidos

Complexos (INCT-FCx) sediado na Universidade de São Paulo. Para nós,

indubitavelmente, sua partida que ocorreu no dia 17 de setembro de 2015 deixou uma

importante lacuna, mas seu legado está servindo de grande fonte de inspiração para a

continuação do progresso da pesquisa na área de Líquidos Magnéticos no Brasil e na

UnB. Nesse sentido, iniciamos em 2017 uma jornada científica a ser realizada na UnB,

próximo à data de seu aniversário, de maneira a prestigiar e honrar sua memória. Trata-

se da Jornada Franco-Brasileira Francisco Tourinho cuja segunda edição será realizada

nos dias 15 e 16 de março de 2018 no auditório do Centro de Apoio ao Desenvolvimento

Tecnológico - CDT/UnB. A finalidade do Evento é reunir em forma de Escola Avançada

alguns dos mais ativos e renomados pesquisadores Franceses e Brasileiros,

especialistas em Nanopartículas Magnéticas, suas dispersões coloidais em ferrofluidos,

bem como de forma mais ampla os nanomateriais avançados, num fórum de discussão

e de apresentação dos mais recentes resultados na área.

5

PRÉFACE

Francisco Augusto Tourinho est né dans l’état de Minas Gerais, le 10 Mars 1957. Il

poursuivit ses études supérieures à l’Université de Brasilia, tout d’abord en maitrise

(1978) puis master (1982) de Chimie. En 1983, il commença son doctorat à Paris et

obtint le titre de Docteur d’État ès Sciences Physiques de l’Université Pierre et Marie

Curie - Paris 6 en 1988. Après son retour de France, il débuta sa carrière universitaire

en 1989 à l’Institut de Physique de l’Université de São Paulo, puis intégra en 1991

l’Institut de Chimie de l’UnB. Il y fondit le Groupe de Fluides complexes de cette

université et suggéra la tenue périodique de la Conférence internationale des

nanosciences, nanotechnologies et nanobiotechnologie (3NANO), dont la quatrième

édition s’est tenue à Paris du 10 au 14 Décembre 2017 après trois éditions précédentes

à l’UnB. C’est lui qui introduisit au Brésil la recherche sur les ferrofluides (liquides

magnétiques) au début des années 90. Il fut le pionnier de la coopération bilatérale entre

l’UnB et l’Université Pierre et Marie Curie (Sorbonne Universités - Paris / France) en la

consolidant par le programme de doctorat de thèse en cotutelle. Aujourd’hui, à l’UnB, la

recherche sur les fluides magnétiques s’étend sur cinq écoles doctorales et rassemble

plus de 150 chercheurs, professeurs, doctorants, étudiants de masters et licence. De

plus, le groupe qu’il a fondé (3NANO Group - Laboratoire de Fluides Complexes) integre

aujourd’hui l’Institut National des Sciences et Technologies de Fluides Complexes

(INCT-FCx) basé à l’Université de São Paulo. Pour nous tous du Groupe 3NANO, son

décès survenu le 17 Septembre 2015 est une immense perte mais l’héritage qu’il nous

a laissé constitue une grande source d’inspiration pour impulser de nouveaux progrès

dans la recherche et l’innovation sur les Fluides magnétiques au Brésil et à l’UnB. C’est

pourquoi nous proposons d’organiser périodiquement des Journées Scientifiques

biennales à l’UNB, toujours au mois de Mars à l’occasion de son anniversaire afin

d’honorer sa mémoire. Ce sont les Journées Franco-Brésiliennes Francisco Tourinho.

La deuxième édition aura lieu les 15 et 16 Mars 2018 au Centre de Développement

Technologique - CDT / UnB. Ces Journées ont pour objectif de réunir, sous la forme

d’une école de formation avancée, chercheurs, jeunes docteurs et étudiants de Masters

et Doctorats, d’établissements d’enseignement supérieur, d’instituts et centres de

recherche et de développement du Brésil et de la France, qui coopèrent autour des

thématiques réunissant les nanoparticules magnétiques, leurs dispersions colloïdales en

ferrofluides ainsi que plus généralement les nanomatériaux avancés.

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TIMETABLE

THURSDAY 15/03 FRIDAY 16/03

14:00 OPENING SESSION

9:30 SILVA FILHO

10:00 GOMIDE

10:15 GOMES DA SILVA

14:30 PERZYNSKI

15:00 AZEVEDO

15:30 FIUZA

15:45 GOMES

16:00 PINHEIRO DA SILVA

16:30 DEPEYROT

17:00 COFFEE BREAK 10:30 COFFEE BREAK

17:00 – 18:00

POSTER SESSION

11:00 GESHEV

11:30 FELIX

12:00 AMMAR

12:30 CLOSING SESSION

12:30 LUNCH

7

PROGRAM

Thursday, March 15th, 2018

14:00 – 14:30 OPENING SESSION

14:30 – 15:00 Chair: J. Depeyrot

IT1 THERMODIFFUSION OF AQUEOUS FERROFLUIDS BASED ON CITRATE-COATED NANOPARTICLES AND ITS ANISOTROPY UNDER A MAGNETIC FIELD R. Perzynski

15:00 – 15:30 IT2 SIRIUS, THE NEW BRAZILIAN SYNCHROTRON LIGHT SOURCE G. Azevedo

15:30 – 15:45 OC1 pH-DEPENDENT SURFACE PROPERTIES OF CARBON DOTS AQUEOUS DISPERSIONS T. Fiuza

15:45 – 16:00 Chair: A. Campos

OC2 IS IT REALLY POSSIBLE TO CONTROL THE MAGNETIC PROPERTIES OF NANOPARTICLES BY CHEMICAL COMPOSITION? R. C. Gomes

16:00 – 16:30 IT3 GRAPHENE OXIDE AND ITS COMPOSITES AS FILMS AND OLFACTION APPLICATIONS M. F. P. da Silva

16:30 – 17:00 IT4 THE ROLE OF PINNED AND ROTATABLE SPINS ON THE EXCHANGE ANISOTROPY FIELDS MEASURED IN CORE/SHELL FERRITE NANOPARTICLES J. Depeyrot

17:00 COFFEE BREAK

17:00 – 18:00 Chair: C. Kern and P. Coppola

POSTER SESSION

8

Friday, March 16th, 2018

9:30 – 10:00 Chair: R. Perzynski

IT5 ORGANIC SEMICONDUCTORS: NEW MATERIALS FOR A CHEAPER AND GREENER ELECTRONICS D. A. da Silva Filho

10:00 – 10:15 OC3 THERMAL DEPENDENCE OF MAGNETIC ANISOTROPY IN

NONINTERACTIVE CORE-SHELL CoFe2O4@-Fe2O3 NP ASSEMBLIES G. Gomide

10:15 – 10:30 OC4 MAGNETIC PROPERTIES OF CoFe2O4/Fe2O3 AND NiFe2O4/Fe2O3 CORE/SHELL PARTICLES F. G. da Silva

10:30 – 11:00 COFFEE BREAK

11:00 – 11:30 Chair: R. Aquino

IT6 NEW PERSPECTIVES IN THE USE OF REMANENCE PLOTS TO DISTINGUISH BETWEEN TYPES OF EXCHANGE COUPLING AND TO QUANTIFY SPIN DISORDER IN MAGNETIC NANOSTRUCTURES J. Geshev

11:30 – 12:00 IT7 FACILE SHAPE-CONTROLLED FABRICATION OF NANOSTRUCTURES ON GLASSES: SYNTHESIS, CHARACTERIZATION, AND APPLICATIONS J. Felix

12:00 – 12:30 IT8 IRONS OXIDE AND GOLD BASED MAGNETO-PLASMONIC CORE-SHELL NANOPARTICLES. SYNTHESIS OPTIMIZATION, CHARACTERIZATION AND BIOMEDICAL APPLICATIONS S. Ammar

12:30 CLOSING SESSION

12:30 LUNCH

9

INVITED TALKS

10

IT1

THERMODIFFUSION OF AQUEOUS FERROFLUIDS BASED ON CITRATE-COATED NANOPARTICLES AND ITS ANISOTROPY UNDER A MAGNETIC FIELD

M. Kouyaté 1, C.L. Filomeno 1,2, G. Demouchy 1,3, G. Mériguet 1, S. Nakamae 4, V. Peyre 1, M. Roger 4, A. Cebers 5, J. Depeyrot 1, E. Dubois 1, R. Perzynski 1 1 Sorbonne Université - CNRS UMR 8234 - laboratoire PHENIX, Paris, France

2 Complex Fluids Group – Inst. de Física & Inst. de Química – Univ. de Brasília, Brasília, Brazil 3 Dpt. de Physique, Univ. Cergy Pontoise, Cergy-Pontoise, France

4 SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette Cedex, France 5University of Latvia, Chair of Theoretical Physics, Riga, Latvia

It has been shown experimentally in [1,2] that, under a temperature gradient, the direction

of thermo-diffusion of ionic -Fe2O3 nanoparticles (NPs), citrate-coated and dispersed in aqueous medium at pH=7, depends on the nature of the counter-ions which are present in the dispersion. The sign of the Soret coefficient ST, as measured by a Forced Rayleigh Scattering method [1], can then be tuned by the choice of these counter-ions. Indeed the entropy of transfer of all the ionic species which are present (NPs, co- and counter-ions), enters in the Seebeck contribution to ST [1,3]. We fix here the ionic strength in finely tuned and characterized dispersions [2], and

we explore the effect of the NP volume fraction on ST, for the following counter-ions lithium (Li+), sodium (Na+), tetramethyl ammonium (TMA+) and tetrabutyl ammonium (TBuA+) (see Fig.a).

The adjustment of ST() with the model described in [1] allows a determination of the NP entropy of transfer, whose sign and value depend on the counter-ions in the dispersion. An applied magnetic field introduces an anisotropy in the thermo-diffusion of the magnetic dispersions [4], and also renders anisotropic the Soret coefficient measured under an applied-field. We probe here two kinds of dispersions with either Na+ or TBuA+ as counter-ions (see Fig. b and c), corresponding respectively to a negative and a positive Soret coefficient in zero applied field. A model developed to describe the under-field anisotropy of the Soret coefficient ST [5] satisfactorily fits the results.

Figure caption: ST() for the dispersions with various counter-ions (a) Anisotropy of ST() for Na+ (b) and TBuA+ (c) counter-ions measured either with the magnetic field parallel or perpendicular to the temperature gradient.

We acknowledge funding from French Agence Nationale de la Recherche (ANR-TE-FLIC Grant no ANR-12-PRGE-0011-01, Horizon 2020 FET-PROACTIVE project, MAGENTA, associated with the Grant n° 731976, prog. CAPES-COFECUB no 714/11 and PHC OSMOSE 2018 n° 40033SJ. [1] C.L. Filomeno, M. Kouyaté, F. Cousin, G. Demouchy, E. Dubois, L. Michot, G. Mériguet, R. Perzynski, V. Peyre, J. Sirieix-Plénet, F.A. Tourinho, J. Magn. Magn. Mat. 431, 2 (2017) [2] C.L. Filomeno, M. Kouyaté, V. Peyre, G. Demouchy, A.F.C. Campos, R. Perzynski, F.A. Tourinho, E. Dubois J. Phys. Chem. C 121, 5539 (2017) [3] T.J. Salez, B.T. Huang, M. Rietjens, M. Bonetti, C. Wiertel-Gasquet, M. Roger, C.L. Filomeno, E. Dubois, R. Perzynski, S. Nakamae Phys. Chem. Chem. Phys. 19, 9409 (2017) [4] J.C. Bacri, A. Cebers, A. Bourdon, G. Demouchy, B.M. Heegaard, R. Perzynski Phys. Rev. Lett. 74, 5032 (1995) [5] T.J. Salez, A. Cebers, G. Demouchy, S. Nakamae, R. Perzynski, M. Roger (to be published)

11

IT2

SIRIUS, THE NEW BRAZILIAN SYNCHROTRON LIGHT SOURCE

Gustavo Azevedo1,,2

1LNLS-Campinas-SP, Brazil 2UFRGS-Porto Alegre, Brazil I will present an overview of the history and current development of Synchrotron Light Technology in Brazil. I will discuss the limitations of our current source (UVX) under the perspective of current scientific challenges in important areas such as infectious and plant diseases (structural molecular biology), catalysis and petroleum industry, energy generation from "green" sources, geochemistry, Environmental Sciences and Materials Science. Next, I will approach the conceptual guidelines of the SIRIUS project, comparing expected performance parameters with existing and planned facilities around the world. I will detail the current stage of project development, including construction completion costs and schedule. Finally, I will show some of the new possibilities opened with the new source, with examples of experiments in high resolution X-ray spectroscopy, X-ray scattering, time resolution experiments, experiments under extreme conditions and coherent X-ray imaging.

12

IT3 GRAPHENE OXIDE AND ITS COMPOSITES AS FILMS AND OLFACTION APPLICATIONS

M. F. P. da Silva Universidade de Brasília - Campus Planaltina, Área Universitária, 01, Vila Nossa Senhora de Fátima - Planaltina, DF, 73345-010 This presentation will show the synthesis, characterization and depositions of films of graphene oxide and its composites with ceramic semiconductor materials (GO-MO). Applications of these materials as impedimetric sensor array for volatile organic vapors detections in electronic olfaction systems (e-nose and e-tongue) for non-invasive diagnoses of human diseases will be emphasized as well. Robust GO-MO sensors could be prepared at room condition using a visible light-photo-assisted procedure. The results support a simple and accurate model complementary based on transition metal oxides. Beyond that, were obtained operational sensors with good sensitivity and comparable selectivity of the bare metal oxide sensors, working at room temperature. [1] M.F.P. Da Silva, L.S. Soeira, K.R.P.. Journal of Thermal Analysis and Calorimetry 102 (3), 907-913. [2] M.F.P. da Silva, M.J. Politi, P.C. Isolani et al. Journal of thermal analysis and calorimetry, 2012. [3] M.F.P da Silva, D.R. de Oliveira, M.R. Cavallari, L.G. Paterno. Materials Chemistry and Physics 165, 125-133. [4] M. R. CAVALLARI, M.F.P. da Silva, G. S. Braga L.G. Paterno. Sensors 14971, 1-8, 2016. [5] M.A. Gross, M.J.A. Sales, M.A.G. Soler, M.A. Pereira-da-Silva, M.F.P. da Silva, L.G. Paterno. et al. Rsc Advances 4 (34), 17917-17924. [6] P.P. Peregrino, M.J.A .Sales, M.F.P. da Silva, L.G Paterno. Carbohydrate polymers 106, 305-311.

13

IT4

THE ROLE OF PINNED AND ROTATABLE SPINS ON THE EXCHANGE ANISOTROPY FIELDS MEASURED IN CORE/SHELL FERRITE NANOPARTICLES

R. C Leite1, F. G. Silva1,2, R. Cabreira-Gomes1, G. Gomide1, V. Pilati1, P. Coppola2

R. Aquino2, G. Goya3, R. Perzynski3, J. Depeyrot1 1Complex Fluids Group, Instituto de Física, Universidade de Brasília, Brazil

2Laboratório de Nanociência Ambiental e Aplicada, FUP, Universidade de Brasília, Brazil 3InA, Universidad de Zaragoza, Spain

4Laboratoire PHENIX, UPMC Sorbonne Universités, Paris, France

Magnetic core/shell nanoparticles (NPs) combine different physical and chemical properties in a unique object and may contribute to the improvement of the whole of their performances in catalysis, magnetic data recording and biomedicine. In magnetic hyperthermia assays, the design of core/shell NPs with a high contrast of anisotropy between shell and core provides a remarkable enhancement of the power loss efficiency, probably due to the interfacial exchange coupling between magnetically soft and hard phases. In this context, the purpose of this talk is to discuss the exchange couplings that we recently measured in core/shell ferrite NPs (typically 3.5 nm sized) of ferrofluids. We investigated magnetic nanocolloids based on MnFe2O4@γ-Fe2O3 and CoFe2O4@γ-Fe2O3 NPs (~ 3 nm). After cooling under field, the hysteresis loops of the samples shift along H axes indicating the existence of a coupling between the spin-ordered core and the disordered surface layer. A comparison with the disordered powder allows us to distinguish the influence of intra- and inter-particle interactions on the exchange bias [1]. The dipolar interparticle interaction plays a demagnetizing role and reduces the exchange bias field in dispersions. The interparticle exchange, which dominates in powder samples, enhances Hex. The bias field is larger for CoFe2O4@γ-Fe2O3 NPs when compared to MnFe2O4@γ-Fe2O3 as a consequence of larger anisotropy of the core material [2]. The magnetodynamics of the cores is probed by Ferromagnetic Resonance measurements, pointing out the NP’s uniaxial magnetic anisotropy. These measurements also reveal the existence of two fields, the anisotropy (Hani) and rotatable (Hrot) fields (Fig. 1). Hani seems to originate in the core/shell interface and it is related to the exchange interactions between them. Its value is confirmed by a simple theoretical model and also by first magnetization measurements. Hrot is associated to a uniaxial anisotropy parallel to the applied field direction, measured at 9 GHz under field (264 kA/m). Two kinds of spins are then evidenced in the surface layer: one component, which follows the FI core (the applied field) with rotatable anisotropy, and another fixed (pinned) with non-rotatable anisotropy. The training behavior (see Fig. 2) is well described by a model considering frozen (pinned) and rotatable components with different relaxation rates at the interface [3]. The results point to interfaces between highly frustrated surface spins that rearrange up to one order of magnitude times more slowly than more inner reversible spins corresponding to better coordinated atoms.

Fig. 1 : Thermal dependence of Hiso field Fig. 2 : Exchange bias field versus loop number

[1] F. G. Gomes et al, J. Phys. D: Appl. Phys. 46, 285003 (2013). [2] R. Cabreira Gomes et al, J. Magn. Magn. Mater 368 (2014) 409. [3] T. Maity et al, Phys. Rev. Lett. 110, 107201 (2013).

1 2 3 4 5 6 7140

160

180

200

220

240 Ferrofluid

Radu Model

= 0.18%

HE

X(O

e)

Number Loops (n)

14

IT5

ORGANIC SEMICONDUCTORS: NEW MATERIALS FOR A CHEAPER AND GREENER ELECTRONICS

Demetrio Filho Institute of Physics - University of Brasilia - Brasilia - Brazil

Organic semiconductors are a new class of materials composed of organic molecules and polymers that have been increasingly used in electronic devices around us. Nowadays, most of the modern cellphones have displays made of organic molecules. Photovoltaic panels made of organic semiconductors promise to be lightweight, flexible and even transparent. Tall buildings will be able to generate energy not only from the roof but also from their entire facades. The use of organic compounds to build electronic devices will allow for new-to-the-world applications, such as cheaper RFID tags, that will replace the current bar-codes in merchandise that we buy in the supermarket, drastically reducing the time we spend to pay for our purchases. And these new devices will be not only cheaper, using less energy to be built, but also greener, as the main building blocks of the devices will be organic compounds. In this talk we will discuss about the origin of the organic semiconductors and how they will revolutionize the World around us.

15

IT6 NEW PERSPECTIVES IN THE USE OF REMANENCE PLOTS TO DISTINGUISH BETWEEN TYPES OF EXCHANGE COUPLING AND TO QUANTIFY SPIN DISORDER IN MAGNETIC

NANOSTRUCTURES

Julian Geshev

Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil

The most-used method for estimation of magnetic interactions in both thin-film and particulate media is that of the magnetic-field-dependent remanence plots, namely Henkel and

M plots, which result from combinations of the isothermal remanence magnetization (IRM) and dc demagnetization (DCD) curves. The technique has been originally developed to characterize interactions in monophase either uniaxial or cubic anisotropy systems [1,2] and has recently been

extended to exchange-biased ones [4]. Until recently, positive M values have been ascribed to interactions promoting the magnetized state whereas negative values indicate interactions stabilizing the demagnetized state. Correspondingly, it seemed well-established that uniaxial anisotropy systems with Henkel plots that lie above the straight line are easier to magnetize than

to demagnetize. One should also have in mind that the M plots for non-interacting cubic-anisotropy systems should intrinsically by positive [2].

Model calculations on exchange-coupled ferromagnetic/antiferromagnetic (FM/AF) bilayers showed that both positive and negative deviations could be obtained simultaneously in

Henkel or M plots considering exchange coupling only, indicating that the interpretation of remanence plots of exchange-coupled systems is not necessarily the conventional one [3]. A very

recent work has demonstrated that M plots may be misleading when nanoparticles, e.g., γ-Fe2O3 nanograins isolated by thick SiO2 shells, do not have a homogeneous internal magnetic configuration [4]. For this system it has been shown that it is the surface structural (and spin) disorder of the nanoparticles that has a pronounced effect on the remanence plots, leading to features remarkably similar to those produced by dipolar interactions. This talk will present a discussion on the above findings which, together with those reported for FM/AF bilayers, constitute a cautionary tale on the widespread utility of remanence plots to assess magnetic interactions. Nevertheless, new perspectives for the use of Henkel and

M plots appear. In case dipolar interactions can be ruled out, M plots can be employed to sensitively detect and possibly quantify intraparticle exchange coupling in magnetically-nonuniform nanoparticles. In FM/AF bilayers, the remanence plots may distinguish between exchange interactions within the FM layer and those occurring at the FM/AF interface [5]. [1] E. P. Wohlfarth, J. Appl. Phys. 29, 595 (1958); O. Henkel, Phys. Status Solidi 7, 919 (1964) [2] J. Geshev and M. Mikhov, J. Magn. Magn. Mater. 104–107, 1569 (1992) [3] A. Harres et al., J. Appl. Phys. 114, 043902 (2013) [4] J. A. De Toro et al., Chem. Mat. 29, 8258 (2017) [5] R. Cichelero et al., J. Phys.: Cond. Matter 25, 426001 (2013)

Remanence plots for γ-Fe2O3 nanoparticles coated by thick SiO2 shells [4] (left), and for a model FM/AF bilayer [5] (right).

16

IT7

FACILE SHAPE-CONTROLLED FABRICATION OF NANOSTRUCTURES ON GLASSES: SYNTHESIS, CHARACTERIZATION, AND APPLICATIONS

Anderson J. Pereira1, Ricardo Schneider2, Juliano Alexandre Chaker3, Paulo Eduardo Narciso4 , Jorlandio F. Felix4

1Department of Physics, Universidade Federal de Vicosa-UFV, Vicosa, MG, Brazil 2Departament of Chemistry, Universidade Tecnologica Federal do Parana, Toledo, PR, Brazil

3Institute of Chemistry, Universidade de Brasília, Brasília, DF, Brazil 4Institute of Physics, Universidade de Brasília, Brasília, DF, Brazil

Many studies have been dedicated to the borophosphate-based glasses due to their unique features which enable applications from medicine to photonics materials. These classes of glasses are transparent in the UV−mid-IR region of the electromagnetic spectrum and have low dispersion, low refractive indices, and improved chemical stability compared to pure phosphate or borate glasses [1,2]. This study explores borophosphate melts to form an active nanoparticles-doped glass substrate for supported nanostructures growth using a bottom-up process. Additionally, single-step synthesis and immobilization of nanoparticles are desired characteristics in some materials because they do not result in additional costs and surface contamination [3]. Therefore, the developments of active materials that enable the single-step synthesis are very attractive for production on an industrial scale [3, 4 and 5]. Furthermore, we show that this innovative simple method can control the dimensions of the nanoparticles (NPs) as a function of the annealing time. The sample characterization was performed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and optical absorption (OA). Finally, the presence some species ions have been studied and confirmed from electron paramagnetic resonance (EPR). NPs-doped glasses were applied as active SERS substrates showing enhancement factors of 10⁸ for rhodamine B molecule. Furthermore, doped glasses were applied as a glass catalyst for alcohol oxidation, synthesis of bis(indolyl)methanes and catalytic reduction of dyes. [1]ElBatal, F.; Ibrahim, S.; Abdelghany, A. J. Mol. Struct. 2012, 1030, 107−112. [2] Kumar, B.; Sankarappa, T.; Kumar, M. P.; Kumar, S. J. Non-Cryst. Solids 2009, 355, 229−234. [3] A. Pereira, et al. J. Phys. Chem. C, 2016, 120 (22), 12265–12272. [4]Schneider R, Felix JF, Moura LG, Morais PC, J. Mater. Chem., 2014, C 2(42):9021–9027 [5] Lenz, G.F., Bini, R.A., Bueno, T.P. , J. F. Felix, et al. J Mater Sci, 2017, 52: 6635.

17

IT8

IRONS OXIDE AND GOLD BASED MAGNETO-PLASMONIC CORE-SHELL NANOPARTICLES. SYNTHESIS OPTIMIZATION, CHARACTERIZATION AND BIOMEDICAL

APPLICATIONS

T. T. Nguyen, 1,2 F. Mammeri 1 and S. Ammar1,* 1 ITODYS lab., Paris Diderot University, Sorbonne Paris Cité (SPS), CNRS UMR-7086, Paris, France 2 Department of Advanced Materials Science and Nanotechnology (AMSN), University of Science and Technology of Hanoï (USTH), Vietnam Academy of Science and Technology (VAST), Hanoi, Vietnam Nanobiotechnologies involve the design, the characterization, and the application of nanostructures, controlling their size and shape at nanoscale. The advances in nanomaterial fabrication have produced a variety of functional nanoparticles (NPs), with different morphologies, giving them unique electronic, magnetic and/or optical properties. Recent synthesis advances allowed integrating different components, like magnetic and plamonic ones, in a same material making it multifunctional and valuable for various biomedical applications. In this context, using the polyol process and seed mediated growth processing we succeeded to prepare iron oxide nanoclusters (NCs) and polycrystals (PCs) coated by nanostar shaped gold layer. By optimizing the synthesis conditions we obtained multimodal NCs-based platforms (Fig. 1 left) valuable for photothermia and magnetic resonance imaging (MRI) and PCs-based substrates (Fig. 1 right) valuable for surface enhanced Raman spectroscopy (SERS) based biosensors.

Figure 1. Core-shell star-shaped magneto-plasmonic nanoparticles based on an iron oxide nanocluster core (left) and polycrystal (right) core coated by a more or less continuous gold

layer.

100nm 100nm

NCsPCs

100nm 100nm

18

ORAL CONTRIBUTIONS

19

OC1 pH-DEPENDENT SURFACE PROPERTIES OF CARBON DOTS AQUEOUS DISPERSIONS

T. Fiuza1, G. Gomide1, A. F. C. Campos2, R. Aquino2, F. Messina3, J. Depeyrot1 1 Complex Fluids Group, Instituto de Física, UnB, Brasília (DF), Brazil.

2 Laboratório de Nanociência Ambiental e Aplicada, FUP, UnB, Brasília (DF), Brazil. 3 Università degli Studi di Palermo, Dipartimento di Fisica e Chimica – UNIPA, Palermo, Italy.

Carbon dots (CDs) are an emerging class of carbon-based nanomaterials with exceptional photoluminescent properties. These easily synthesized nanostructured materials are also of great interest due to their appealing biophysical-chemical characteristics, such as biocompatibility, high sensitivity to metal ions in solution, photocatalytic properties, low toxicity [1]. The CDs investigated here were synthesized by thermally induced decomposition of organic precursors. They present

an inner core constituted of a -C3N4 crystalline structure surrounded by a disordered surface shell containing a variety of polar functional groups [2]. Their size (approximately 3 nm) and structure were checked by combined analysis of XRD and FTIR measurements performed on powder samples. In order to investigate the pH-dependence of the surface charge behavior, the powder samples were dispersed in different precursor aqueous solutions from pH 2.0 to 12.0, acidified by HNO3 and alkalinized by NaOH. The diluted colloidal dispersions were prepared in two different mass concentrations (0.05 g/L and 0.15 g/L) and also at controlled ionic strength by the addition of NaNO3 as a background electrolyte. Images of the prepared dispersions are presented in Fig. 1 (left). Under white light, the dispersion changes in color with increasing pH. We also note that some precipitate is present in all samples, except the one with pH 11.8. Under UV light, we can qualitatively observe a blueshift of the fluorescence with increasing pH. The Zeta potential (ζ) of each dispersion was determined by the measurement of the electrophoretic mobility at room temperature for each pH condition in both concentrations. The negative charge density increases with pH, in good agreement with the visual observations of long term colloidal stability in pH 12. No significant difference was observed in the Zeta potential for concentrations investigated here. In attempt to obtain the pK value of the nanoparticles and determine the surface charge density, a potentiometric and conductimetric titration approach [3] was applied. The data indicates that the titration curve behavior from acidic to alkaline differs drastically from the reverse route, suggesting an alteration of the nanoparticles surface composition by pH-induced conversion of surface groups. These novel results enlighten the importance of investigating the effects of the pH variations on CDs dispersions.

[1] A. Sciortino, E. Marino, B. Dam et al., J. Phys. Chem. Letters, 7, 3419 (2016) [2] F. Messina, L. Sciortino, R. Popescu et al., J. Mater. Chem. C, 4, 2598 (2016) [3] A. F. C. Campos, R. Aquino, F. A. Tourinho, et al., Eur. Phys. J. E, 36, 42 (2013)

Figure 1 - Left: Picture of 0.15 g/L samples in different pH's under white light (top) and UV (bottom). Right: pH dependency of the Zeta Potential for the dispersions in both concentrations.

5 10-60

-40

-20 0.05g/l

0.15g/l

ZP

(m

V)

pH

20

OC2

IS IT REALLY POSSIBLE TO CONTROL THE MAGNETIC PROPERTIES OF NANOPARTICLES BY CHEMICAL COMPOSITION?

R. Cabreira Gomes1,2, V. Pilati1, F. H. Martins1,2, F.L.O de Paula1, P. Coppola3, R. Aquino3, J. Depeyrot1, R. Perzynski2

1Instituto de Física, Universidade de Brasília, Brasília, Brazil 2Université Pierre et Marie Curie - Paris VI, Paris, France

3Fundação Universidade Planaltina, Universidade de Brasília, Brasília, Brazil

It has been known that mixed ferrites are promising materials for heat exchange applications and theranostic ones [1]–[3]. Recently we have studied the magnetic fluids based on this materials composed by Zn and Mn with different stoichiometric proportions and we have paid attention basically to the magnetically induced properties [4]. Furthermore, we have seen a coherently behavior of both magnetic properties and optical ones dependent to Mn-proportion and we have put ourselves the title question. However, to answer that and other questions it is imperative to understand the materials from a fundamental point of view, i.e. how it is formed and structured. To perform this study, two classes of core@shell nanoparticles and their ferrofluids were synthesized. They are leading made of “pure ferrites” (MnFe2O4@γ-Fe2O3 and ZnFe2O4@γ-Fe2O3) and “mixed” ones nominally composed by ZnXMn(1-X)Fe2O4@γ-Fe2O3, where X = 0.3, 0.6 and 0.9 [4]. Magnetic and magneto-optical properties of these two classes of nanomaterials are compared. The answer to the title question is found into the material’s crystalline structure [5], [6]. Rietveld refinement of neutron diffraction measurements shows that the ionic distribution within the crystalline structure is the key source of magnetic properties of the materials.

References [1] J.-H. Lee et al.,Nat. Nanotechnol., vol. 6, no. 7, pp. 418–422, Jul. 2011. [2] Q. Zhang et al.,Chem. Mater., vol. 27, no. 21, pp. 7380–7387, Nov. 2015. [3] S. H. Noh et al.,Nano Lett., vol. 12, no. 7, pp. 3716–3721, 2012. [4] V. Pilati et al., J. Phys. Chem. C, vol. 122, no. 5, pp. 3028–3038, Feb. 2018. [5] F. H. Martins et al., J. Phys. Chem. C, vol. 121, no. 16, pp. 8982–8991, Apr. 2017. [6] J. A. Gomes et al., J. Phys. Chem. C, vol. 116, no. 45, pp. 24281–24291, Nov. 2012.

21

OC3

THERMAL DEPENDENCE OF MAGNETIC ANISOTROPY IN NONINTERACTIVE CORE-

SHELL CoFe2O4@-Fe2O3 NP ASSEMBLIES

G. Gomide1, R. C. Gomes1, R, Perzynski2, R. Aquino3, J. Depeyrot1 1Complex Fluids Group, Instituto de Física, UnB, Brasília (DF), Brazil

2 Lab. PHENIX, UPMC Univ. Paris 6, Sorbonne Universités, Paris, France 3Laboratório de Nanociência Ambiental e Aplicada, Faculdade UnB Planaltina, Brasília (DF), Brazil

Core-shell magnetic nanoparticles (NPs) are widely investigated nanomaterials with numerous applications, from biomedicine to energy harvesting. In this work, we investigate the thermal dependence of coercivity for two ferrofluid samples composed of differently sized core-shell CoFe2O4@γ-Fe2O3 NPs. These NPs were obtained by hydrothermal coprecipitation in alkaline medium and NP size was controlled by the pH of the synthesis medium [1]. A subsequent hydrothermal surface treatment with Fe(NO3)3 produces the maghemite shell. The synthesized NPs have their chemical, structure and morphological properties characterized by Atomic Absorption Spectroscopy, X-Ray Diffraction and Transmission Electron Microscopy. The coercive field is measured from zero field cooled hysteresis loops and analyzed in the framework of the Stoner-Wohlfarth model. Our analysis also considers the size distribution and how it affects the thermally activated transition from the blocked to the superparamagnetic (SPM) state. Indeed, for polydisperse assemblies of NPs, an increase of the SPM population leads to smaller coercivity [2]. However, this is not sufficient to account for our experimental data. We have, then, furthered this investigation by also considering the thermal dependence of two key parameters: saturation magnetization and magnetic anisotropy energy density. The saturation magnetization (MS) only works as a multiplicative term in the anisotropy field 𝐻𝑘 = 2𝐾𝑒𝑓 𝜇0𝑀𝑠⁄ , and has a thermal

dependency accounted for by using Bloch’s law (Fig. 1.a). On the contrary, the effective anisotropy constant (Kef), besides working as a scale factor, has a deep impact on the ratio of blocked and SPM populations. We account for the anisotropy’s thermal dependence applying a single-ion anisotropy model [3] commonly used in oxide magnets (Inset of Fig. 2.b). The generalized model we propose adjusts the experimental data very well (Fig. 1.b), showing that the thermal dependency of both magnetization and anisotropy constants has significant effects in the overall behavior of the coercive field depending on the size distribution of the analyzed NPs.

Figure 2 - a) Temperature dependence of saturation magnetization for 6 nm and 3 nm cobalt ferrite core-shell nanoparticles. Solid lines are the best fit using Bloch's Law. b) Temperature dependence of coercivity for both samples showing the best fits with the proposed model (solid lines). Inset depicts the calculated thermal dependence of the anisotropy constant.

[1] R. Aquino et al, J. Magn. Magn. Mater., 252, 23–25 (2002) [2] W. C. Nunes et al, Physical Review B, 70(1), 14419 (2004) [3] E. Garaio et al, Nanotechnology, 26(1), 15704 (2015)

22

OC4

MAGNETIC PROPERTIES OF CoFe2O4/Fe2O3 AND NiFe2O4/Fe2O3 CORE/SHELL PARTICLES

F. G. Silva1,2,3, P. Coppola2, D. Fiorani1, J. Depeyrot3, R. Aquino2,3, N. Yaacoub4, M. Roland5, R. Perzynski6 and D. Peddis1

1Istituto di Struttura della Materia - CNR, 00015 Monterotondo Scalo (RM), Italy. 2Complex Fluid Group, Laboratório de Nanociência Ambiental e Aplicada, Universidade de Brasília,

Faculdade UnB Planaltina (FUP-UnB), 73345-010 Brasília - DF, Brazil. 3Complex Fluid Group, Instituto de Física, Universidade de Brasília, UnB, 70919-970 Brasília - DF,

Brazil. 4Institut des Molécules et Matériaux du Mans CNRS UMR-6283, Université du Maine, F-72085 Le Mans,

France 5Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden

6Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Lab. PHENIX, 4 Place Jussieu, 75005 Paris, France.

We prepare, by the coprecipitation method, core shell (CS) NPs of different sizes consisting of a CoFe2O4 ferrite core surrounded by a (γ-Fe2O3) (maghemite) shell (CoFe2O4/-Fe2O3). The microstructural properties of these NPs are investigated by XRD and TEM experiments. The mean size diameter, determined by XRD measurements, ranges from 2 to 11 nm. Previous investigations of core/shell NPs prepared by the same method and with same size demonstrated that the inner region has a well-ordered ferrimagnetic structure, surrounded by a surface layer of spins randomly frozen at low temperatures [1]. This disordered surface contribution is evidenced by under-field Mössbauer spectroscopy measurements [2], showing a progressive spin alignment under field along the ferrite core.

In this work we investigated the influence of the size diameter on the magnetic properties and in particular on the exchange bias (EB) effect. Mössbauer spectra recorded 12K under intense magnetic field (8T) shown the presence of the surface spin disorder, as observed previously. This disorder is clearly more evident for NPs of smallest size diameter. The EB field Hex, measured at 5K after cooling under a field of 3 kOe, is present for all the samples and it increases as the size particle of the NPs decreases (11 nm; Hex15 Oe, 5,4 nm; Hex105 Oe ; 2,2 nm; Hex 155 Oe). For the smallest particle size (2 nm) we investigated the effect of changing the composition of the core, comparing the Hex value with that NiFe2O4/-Fe2O3 particles of the same size. The Hex is higher for CoFe2O4/-Fe2O3 (Hex 155 Oe; for NiFe2O4/-Fe2O3,

Hex 95 Oe), indicating the role of the core anisotropy, which is larger for CoFe2O4. [1] R. Aquino, J. Depeyrot, M. H. Sousa, F. A. Tourinho, E. Dubois, and R. Perzynski, Phys. Rev. B - Condens. Matter Mater. Phys. 72, 1 (2005). [2] E. C. Sousa, H. R. Rechenberg, J. Depeyrot, J. A. Gomes, R. Aquino, F. A. Tourinho, V. Dupuis, and R. Perzynski, J. Appl. Phys. 106, 1 (2009)

23

POSTERS

24

ANTHRAQUINONE DYE SORPTIVE REMOVAL FROM AQUEOUS SOLUTIONS BY MAGNETIC NANOCOMPOSITES H. A. L. de Oliveira, A. F. C. Campos

DEVELOPMENT OF AN INTERACTIVE APPLICATION TO FIT MAGNETIZATION

DATA WITH A GENERALIZED LANGEVIN FUNCTION T. S. A. Cassiano, S. G. Santos, L. L. Castro. THERMODYNAMICS OF CHROMIUM (VI) ADSORPTION ON MAGNETIC CORE-SHELL NANOPARTICLES F. N. da Silva, A. F. C. Campos, P. H. M. Brito MAGNETIC NANOPARTICLES SYNTHESIZED AND EMBEDDED IN LAPONITE DISPERSION A. S. Aguiar, R. Aquino, C. Kern, G. J. da Silva PHASE TRANSITION IN THE CORE/SHELL MODEL OF MAGNETIC NANOPARTICLE L. E. de Rezende, P. E. de Brito POTENTIOMETRIC-CONDUCTOMETRIC TITRATIONS IN MAGNETIC COLLOIDS: A MULTIPARAMETRIC FITTING APPROACH C. P da Silva, A. F. C. Campos SPECIFIC EFFECTS OF COUNTER-IONS AND OF THE POLAR-SOLVENT NATURE ON STRUCTURE AND THERMODIFFUSIVE PROPERTIES OF COLLOIDAL DISPERSIONS C. L. Filomeno, M. Kouyaté, V. Peyre, G. Demouchy, A. F. C. Campos, R. Perzynski, E. Dubois SYNTHESIS AND CHARACTERIZATION OF GRAPHENE-BORON OXIDE COMPOSITE AND SENSORIAL ASPECTS L. Nonato, A. F. C. Campos, M. F. P. da Silva THEORETICAL STUDY OF ELECTRONIC PROPERTIES OF ORGANIC SYSTEMS R. A. L. Silva, D. F. S. Machado, V. H. C. Silva, L. Ribeiro, H. C. B. de Oliveira, D. A. S. Filho THERMODYNAMICS OF THE NANOPARTICLE-ELECTROLYTE INTERFACE CHARGING IN MAGNETIC COLLOIDS M. R. B. de Almeida, A. F. C. Campos STUDY OF THE STABILITY OF DISPERSED COLOIDAL NANOSILICATES IN LAMELLAR PHASES G. C. C. Leite, G. J. da Silva, E. A. de Oliveira PREPARATION AND STRUCTURE CHARACTERIZATION OF MONTMORILLONITE BASED ORGANOCLAY D. Liguori, G. J. da Silva, E. A. de Oliveira