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2a Oficina de Trabalho do Instituto Nacional de Eletrônica Orgânica

2nd Workshop of the National Institute for Organic Electronics

INEO 2010

Atibaia, March – April 2010



Monday 29.03 / Segunda-Feira 29.03


08:00

Registration/Inscrições


08:30-09:20

Opening / Abertura


09:20-10:10

Raman scattering and SERS: basic concepts and applications

Carlos José Leopoldo Constantino, Faculdade de Ciências e Tecnologia, UNESP – Presidente Prudente




10:10-10:35

“Planar Waveguides and Wavelenghth Converters”

Francisco E. G. Guimarães, Instituto de Física de São Carlos, USP



10:35-10:50


Coffee Break / Café




10:50-11:40

“Studies using spectroscopy on the correlation between morphology and performance for light emmiting devices: some experimental results and challenges”

Teresa D. Z. Atvars, Instituto de Química, Unicamp




11:40-12:00

“Nonlinear vibrational spectroscopy of interfaces: the interplay between experiments and simulations”

Paulo B. Miranda, Instituto de Física de São Carlos, USP




12:00-12:30

“Lifetime and degradation effects in luminescent polymers”,

Giovana Ribeiro Ferreira, Instituto de Ciências Exatas e Biológicas, UFOP



12:30-14:00


Lunch / Almoço




14:00-17:00

Free discussion of projects and collaborations/Discussão livre de projetos e colaborações


17:00-19:00

Posters / Painéis

Scientific contributions; experimental and computational facilities / Trabalhos científicos e apresentação das facilitiesem cada grupo ou laboratório



20:00

Dinner / Jantar




Tuesday 30.03 / Terça-Feira 30.3


08:30-09:20

Reformulated space-charge limited current model and its application to disordered organic materials

José Arruda de Oliveira Freire, Departamento de Física, UFPR




09:20-09:40

“Application of ultrafast spectroscopy to the study of energy transfer processes in conjugated polymers”,

René Nome, Instituto de Química, Unicamp




09:40-10:00

“Investigation on titanium dioxide thin layer influence electrochemically synthetized polythiophene based organic photovoltaic devices”

Rogério Valaski, INMETRO




10:00-10:20

“Molecular modeling of organic systems”

Melissa F. S. Pinto, Instituto de Física de São Carlos, USP



10:20-10:50


Coffee Break / Café




10:50-11:10

“Identification of sites for Oxygen Incorporation due to wet oxidation on Hydrogenated Si(100) Surfaces through STM images – a powerful tool”

Regina Lélis-Sousa, Instituto de Física, USP




11:10-12:00

“LaPPS and INEO: Partnerships and Advances in the 2009-2010 Period”

Leni Akcelrud, Departamento de Química, Centro Politécnico, UFPR




12:00-13:00

Palestra Rede Namitec

Antonio Luis Pacheco Rotondaro – CTI/MCT



13:00-14:00


Lunch / Almoço




14:00-17:00

Free discussion of projects and collaborations / Discussão livre de projetos e colaborações


17:00-19:00

Posters / Painéis

Scientific contributions; experimental and computational facilities / Trabalhos científicos e apresentação das facilitiesem cada grupo ou laboratório



20:00

Dinner / Jantar



Wednesday 31.03 / Quarta-Feira 31.03


08:30-09:20

Molecular recognition and other possible interactions in biosystems

Osvaldo N. Oliveira Jr., Instituto de Física de São Carlos, USP




09:20-09:40

Theoretical study of copper complexes

Marcos B. Gonçalves, Instituto de Física, USP




09:40-10:00

“Organic Photovoltaic Devices: Study of Active Layers and Electrodes”,

Carla Daniele Canestraro, Departamento de Física, UFPR




10:00-10:20

Electroluminescence of multi-layer devices using a new terbium β-diketonate complex as emitting layer”,

Ivan H. Bechtold, Departamento de Física, UFSC



10:20-10:50


Coffee Break / Café




10:50-11:10

Titanium dioxide in hybrid photovoltaic solar cells

Klaus Krambrock, Departamento de Física, UFMG




11:10-11:35

Comparative Study of MDMO-PPV Thin-Film Transistors

Marco R. Cavallari, Escola Politécnica, USP

“ OLEDs: terms, definitions and standards”

Elvo C. Burini Jr, Instituto Eletrotécnico e Energia – USP




11:35-11:50

Penicillin biosensor based on field-effect devices functionalized with layer-by-layer assembly of carbon-nanotubes

José Roberto Siqueira Jr., Instituto de Física de São Carlos, USP




11:50-12:40

“Magnetic and Hyperfine Properties in metal complexes”

Helena M. Petrilli, Instituto de Física, USP



12:40

Lunch / Almoço


14:00-17:00

Free discussion of projects and collaborations / Discussão livre de projetos e colaborações


17:00-18:00

Closing session/ Sessão de encerramento

20:00

Dinner / Jantar


Abstracts / Resumos




Raman scattering and SERS: basic concepts and applications

Carlos José Leopoldo Constantino (1)

  1. Univ Estadual Paulista, UNESP – Presidente Prudente, SP, Brazil.

The Raman effect is defined as the inelastic scattering of light, i.e. scattering with change in the frequency of the incident radiation passing through a substance. It was discovered in 1928 by the Indian physicist Chandrasekhara Venkata Raman (Nobel Prize in 1930), who started publishing a series of related articles in 1922. In 1974 Fleischmann et al. observed a surprising enhancement of the Raman signal of pyridine on a rough Ag electrode. In 1977 the groups of Jeanmaire and Van Duyne and Albrecht and Creighton solved the puzzle in an independent way. They found that the effect was due to the enhancement of the electromagnetic field of the incoming light by the Ag nanoparticles (AgNPs). This is the called surface-enhanced Raman scattering (SERS). The improvement of the laser and detector technologies and the understanding of the SERS mechanism itself led to the SERS technique being applied even in detecting single molecules, which is the ultimate limit in terms of chemical analysis. In addition to single molecule detection, the SERS technique has been applied to characterize a wide range of materials, now including biological systems, as in the identification and classification of virus or cancer cells, biochemical diagnostics and pharmaceutical drugs. The SERS enhancement can reach 106 in average, but under regime of single molecule detection it may reach 1014 as estimated by Kneipp et al. and Nie et al. or 109-1011 as reported by Blackie et al.. Various types of enhancers have been used, such as metallic nanoparticles (usually Ag and Au) in different forms such as colloid, large nanoparticles (probably aggregates) and thermally evaporated thin films. Because it is known that higher enhancement factors are obtained with aggregates or clusters, different strategies have been developed to produce highly SERS-active substrates. Recently, we reported the use of AgNPs trapped within a phospholipid matrix grown in the form of layer-by-layer (LbL) films to achieve the SERS effect, which can be applied as a proof-of-principle to investigate interactions between guest molecules and phospholipids in membrane mimetic systems. The basic concepts related to Raman scattering and SERS and their applications are going to present on this talk.






Planar Waveguides and Wavelength Converters for Photovoltaic and Optical Sensing Applications
M. M. do Vale1, H. A. Guerreiro1, F. Trivinho-Strixino2, Ernesto C. Pereira3, L. Akcelrud4 and F. E. G. Guimarães1

1Instituto de Física de São Carlos, Universidade de São Paulo, 2Universidade Federal de São Carlos/Campus Sorocaba, 1Universidade Federal de São Carlos – Departamento de Química – LIEC/CMDMC, 4Laboratório de Polímeros Paulo Scarpa (LaPPS) UFPR,
This presentation describes the fabrication of multipolymeric optical waveguides based on poly(methyl methacrylate) and porous anodic alumina (PAA) matrixes. These planar luminescent waveguides present the unique characteristic of emitting very narrow (5nm) orthogonal guide modes. The spectral position, shape and polarization effect of the narrow waveguide modes is described. The emission wavelength can be completely tunable by changing the waveguide geometry and the effective diffraction index or by controlling the optical process between the constituent emitting molecules. Here, we have used five polymers having emission and absorption in the range from 300 nm to 600 nm. The waveguide can also be used as wavelength converter, since all absorbed incident light is converted to a single narrow emission displaced to the red as a result of multiple emissions and reabsorptions along the guide. We demonstrate that anodic alumina exhibits efficient near-UV and visible luminescence at room temperature. In particular, active waveguide based on PAA luminescence can be tuned with luminescent polymers embedded in their pores. We propose that these findings make self-emitting porous alumina waveguides a promising template for optical sensor applications. Analytical tests with a commercial pesticide (chloropyriphos) and different gases were performed showing the advantages of this system for sensor application.




Studies using spectroscopy on the correlation between morphology and performance for light emmiting devices: some experimental results and challenges / Estudos espectroscópicos das correlações entre morfologia e desempenho de dispositivos eletroluminescentes: alguns resultados experimentais e alguns desafios.
T.D. Z. Atvars

Instituto de Química, Departamento de Físico-Química, Universidade Estadual de Campinas, Caixa Postal 6154, Campinas 13084-971, SP.

e-mail: brunabonon@yahoo.com.br
In this presentation we will show some of the results obtained using photoluminescence techniques and the correlation of these data with the morphology of polymer blends using electroluminescent materials. We will also show some advantages of using polymer blends to improve the electroluminescence in devices, and some possible explanations for this improvement based on the morphology of the thin films [1,2]. Description of the morphology of thin films is a complex issue and limitations of some technique will be also discussed.

Further, we will describe the conditions of the Photochemistry and Photophysics Laboratory in IQ-Unicamp, what we can do in terms of the correlation between morphology and device performance and the major challenges that we considered relevant for the INEO in the photoluminescence field.


[1] B. R. Nowacki, E. Iamazaki, A. Cirpan, F. Karasz, T. D. Z. Atvars, L. Akcelrud, Polymer. 50, 6057 (2009).

[2] R. F. Cossiello, A. Cirpan, F. E. Karasz, L. Akcelrud, T. D. Z. Atvars, Synth. Met. 158, 219 (2008).






Nonlinear vibrational spectroscopy of interfaces: the interplay between experiments and simulations
Paulo B. Miranda

Instituto de Física de São Carlos – USP, Brazil
The behavior of molecules at interfaces may be very different from that in bulk materials due to interactions in an asymmetric environment, leading to different molecular arrangements and reactivities, for example. In this talk I will briefly describe an experimental technique known as sum-frequency generation (SFG) spectroscopy, which is based on nonlinear optics and can be used to obtain the vibrational spectrum of molecules at interfaces. From the SFG spectrum it is possible to deduce information about the molecular arrangement and interactions at the interface, but this task can be greatly facilitated with the help of computer simulations. A few applications of SFG spectroscopy to investigate water and organic molecules at interfaces will be discussed, emphasizing the role of simulations in the interpretation of the experimental results.





Lifetime and Degradation Effects in Luminescent Polymers
G. R. Ferreira (1), B. F. Nowacki (2), T. Schimitberger (1), M. M. Silva (1), R. A. Domingues (3), E. R. deAzevedo (4), T. D. Z. Atvars (3), L. C. Akcelrud (2), R. F. Bianchi (1)

(1) Universidade de Ouro Preto, (2) Universidade Federal do Paraná, (3) Universidade Estadual de Campinas, (4) Instituto de Física de São Carlos/ Universidade de São Paulo

e-mail: giovanaribeiro@iceb.ufop.br
Optical properties of luminescent polymers have been studied since the first report of electroluminescence in poly (p-phenylenevinylene) in 1990. However, the performance of the devices made from them is limited by high vulnerability to degradation processes which dramatically change the emission color and reduce the quantum efficiency and durability of their devices. The change in emission color and the reduction in photoluminescence and absorbance intensity, characteristic from these processes, caused by visible radiation, show the possibility to design dosimeters where the effects of these phenomena on the optical properties of conjugated polymers are more important than improving the durability of devices made from them. Several studies have identified oxygen as the main contributor for the degradation of polymer, specially attributing the presence of oxygen as quenching centers for singlet exciton or nonradioactive polaron pairs. A recent study indicated that the photodegradation process depends not only of the environmental conditions but also of the polymer preparation. In this work we investigated the changes on the optical behavior of luminescent polymers under the effect of blue-light radiation. We studied the variation of absorption and fluorescence spectra of PPV-derived films and solutions in (i) toluene, (ii) chloroform and (iii) chloroform in presence of presence of free radical scavengers. The optical properties of this system were investigated by photoluminescence, UV-Vis absorption spectroscopy and fluorescence microscopy. The changes in chemical structure of PPV due blue-light irradiation have been investigated by FTIR, 1H NMR and 13C NMR spectroscopy. These results show that the radiation exposure causes the decrease of the polymer conjugation length probably due the oxidation of the vinylic bonds to give carbonyl groups (C=O) or the backbone scission and increase in conformational disorder of the polymer. All these effects may be responsible for the blue-shift observed in absorption and photoluminescence spectra after blue-ligth radiation exposure. The present work was sponsored by FAPEMIG, CNPq, CNPq/INEO and Capes.




Reformulated space-charge limited current model and its application to disordered organic materials
José Arruda de Oliveira Freire

Departamento de Física, Universidade Federal do Paraná
We reformulate the traditional model used to describe space-charge effects in the current-voltage characteristics of a material sandwiched between planar electrodes. The new formulation is based on the concept of the quasi-electrochemical potential. The material density-of-states and variable mobility enter explicitly in the formulation as well as the electrodes work-functions. The main advantages of the formulation are: (i) the I(V) characteristic is obtained over the full range of bias, covering the diffusion limited, the space-charge limited and the injection limited current regimes; (ii) no assumption about the nature of the contact need to be made; (iii) no distinction between conduction and traps states need to be made. The mobility dependence on the quasi-electrochemical potential is necessary and we obtained this quantity for a Gaussianly disordered organic. Our results show the effect of the disorder on the transition voltage between the three current regimes and on the exponent I ~ Vn in the space-charge limited current regime.




Application of ultrafast spectroscopy to the study of energy transfer processes in conjugated polymers / Aplicações da espectroscopia ultrarápida ao estudo de processos de transferência de energia em polímeros conjugados

René Nome and Teresa Atvars



Instituto de Química, Unicamp, Campinas, SP, CEP 13084-375, Brazil
Studying energy transfer mechanisms in conjugated polymers may provide a pathway to control the destiny of the excited state energy, thereby allowing the production of more efficient opto-electronic devices. The disorder that characterizes conjugated polymers in condensed phases leads to the formation of partially delocalized excitonic states which are considerably affected by the surrounding environment. Recently, ultrafast spectroscopic studies have revealed coherent intrachain energy transfer in MEH-PPV in solution at room temperature. The goal of the present seminar is to discuss this mechanism based on coupling between vibrational and electronic coherences, together with a presentation of the design and construction of an ultrafast spectroscopy lab at IQ - Unicamp.




Investigation on titanium dioxide thin Layer influence eletrochemically synthesized polythiophene based organic photovoltaic devices
R. Valaski (1), W. G. Quirino (1), C. Legnani (1), N. A. D. Yamamoto (2), C. D. e Canestraro (2), L. S. Roman (2), R. M. Q. Mello (3), L. Micaroni (3), M. Cremona (4,1).

(1)Instituto Nacional de Metrologia, Normalização e Qualidade Industria INMETRO, (2) Departamento de Física da Universidade Federal do Paraná, (3) Departamento de Química - Universidade Federal do Paraná, (4) Departamento de Física - Pontifícia Universidade Católica do Rio de Janeiro
The polythiophene (PT) is one promising organic semiconductor to be used as active layer in organic photovoltaic devices. It has good stability in environmental conditions and high absorption coefficient in the visible range of electromagnetic spectrum. Among the different methods for the production of the organic active layer, the electrochemical methods stand out by their feasible features. The electrochemically synthesized device presents efficiency higher than that obtained by the similar ones in which the active layers are produced by other methods [1]. However, high efficiency devices are achieved only when p-n junctions (donor-acceptor) are used either as a bi-layer device or bulk heterojunction in which it is possible to obtain high exciton dissociation rates. Organic semiconductors are the donors while fullerenes, carbon nanotubes or TiO2 are the acceptors, just to cite a few. In this work, the p-n junction is formed by a bi-layer with PT as the donor, TiO2 as the acceptor sandwiched between fluorine doped tin oxide (FTO) and Al electrodes. The results of fabrication and characterization of TiO2 and PT neat films and devices based on neat PT and TiO2(40nm)/PT(300nm) bi-layer are presented. The TiO2 films were produced by sol-gel method [2] and PT films were electrochemically synthesized onto FTO and FTO/TiO2 with an average thickness that is larger than the ideal value (40nm). The polymer films synthesized onto TiO2 are uniform and continuous only at that thickness, nevertheless the monochromatic external quantum efficiency (IPCE) increased when TiO2 layer was added to the device. Moreover, morphological analyses through AFM techniques show high roughness values for the electrodeposited PT on FTO/TiO2 producing regions with lower PT thickness. These regions can be preferential paths for free charge carries as well for exciton generated in PT layer towards the TiO2 interface (exciton dissociation site) improving the device efficiency in comparison with the devices without TiO2 layer. Furthermore, the FTO/TiO2 and TiO2/PT interfaces effects can be compensate by the increase of the series electrical resistance since the TiO2 resistivity is more than FTO one.
[1] – R. Valaski, C. D. Canestraro, L. Micaroni, R. M.Q. Mello, L. S. Roman, Sol. Energy. Mat. Sol. Cells 91, 684 (2007)

[2] - A. C. Arango, L. R. Johnson, V. N. Blizyuk, Z. Schlesinger, S. A. Carter, H. H. Hörhold, Adv. Mat. 22, 1689 (2000)






Modelagem molecular de sistemas orgânicos.

Molecular modeling of organic systems.

M. F. S. Pinto (1), R. Ramos (2), M. J. Caldas (2), R. M. Faria (1)

(1) Instituto de Física de São Carlos, Departamento de Física e Ciência dos Materiais, Universidade de São Paulo, São Carlos, SP - Brasil.

(2) Instituto de Física, Departamento de Física dos Materiais e Mecânica, Universidade de São Paulo, São Paulo - Brasil.

e-mail: melissa.fsp@gmail.com
Molecular modeling of complex systems has been recognized as an important branch of material science, being progressively used together with experimental researches for prediction and interpretation of physicochemical phenomena. The choice of adequate theoretical methods for each purpose is extremely important, and to model a real system is not an easy task. Specifically concerning to organic systems as active materials for technological applications, e.g. light emitting diodes, photovoltaic devices and field-effect transistors, the combination of experimental measurements and molecular simulation methods is essential for better understanding of fundamental properties particular effects observed on organic systems [1]. In this talk, we present some quantum and semi-classical methodologies such as Molecular Dynamics, Monte Carlo, Molecular Mechanics as well as hybrid methods. Conformational and spectroscopic results calculated for oligofluorenes by means of Quantum Mechanics approaches will be discussed and compared to results obtained by experimental groups of INEO. In addition, we are using Molecular Mechanics to study morphological effects of disordered poly(p-phenylene vinylene) PPV films induced by uniaxial stretching. This last study is motivated to explain polarized emission in oriented PPV films that was observed by Cazati et al. [2,3], i. e., to understand in the atomistic point of view the morphological properties of this system and its correlation with the polarization of the emitted light.
We acknowledge the financial support from the CAPES, INEO, FAPESP and computational facilities of LCCA-USP.
[1] T. A. Skotheim and J. R. Reynolds eds., Handbook of conducting polymers. Conjugated (CRC Press, Boca Raton, 2007).

[2] T. Cazati, F. E. G. Guimaraes, and R. M. Faria. In 12th International Symposium on Electrets, 2005, p. 309.

[3] A. Marletta, R. H. Miwa, T. Cazati, F. E. G. Guimaraes, R. M. Faria, and M. Verissimo-Alves, App. Phys. Lett. 86 (2005).




Identification of sites for Oxygen Incorporation due to wet oxidation on Hydrogenated Si(100) Surfaces through STM images – a powerful tool /

Identificação de sítios de incorporação de oxigênio devido a processos de oxidação molhada em superfícies Si(100)(2x1):H utilizando imagens de STM – uma ferramenta poderosa
R. Lelis-Sousa and M. J. Caldas (1)

(1) Institiuto de Física, Departamento de Materiais e Mecânica IFUSP-DFMT – Universidade de São Paulo.

e-mail: rlsouza@romeo.if.usp.br
Silicon and its interfaces are important materials in the microelectronics industry and there are new developments in nano-electronics and hybrid electronics: in this last case, for many applications wet chemistry preparation processes are relevant. However very little is known, either theoretically or experimentally, about the mechanisms and primary products which originate from the reaction between water and the Si surface. Experimental probes are most of the time indirect (vibrational spectroscopy [1]) and can lead to controversial issues. The purpose of this presentation is to show, with our study of the water molecule dissociation on the Si(100)(2x1):H surface, how powerful is the STM (Scanning Tunneling Microscopy) tool to provide identification of surface reactions, that can be difficult with other techniques.

Our results were obtained within the Density Functional Theory (DFT), and the reaction pathways for the water molecule decomposition on the surface have been studied with a CI-NEB (Climbing Image - Nudging Elastic Band) methodology [2, 3]. We analyse different oxidation routes, and also simulate [4] the pattern that would be visible experimentally from STM. It is seen that oxygen inclusion in the silicon back-bonds produces a clearly asymmetric STM pattern, which is a simple condition to discriminate between inclusion of O atoms on-dimer or in the back-bond.


We acknowledge support from CAPES, INEO, CNPQ, FAPESP and computational facilities of LCCA-USP.
[1] G. Ranga Rao et al, Surf. Sci. 570, 178 (2004), Z-H. Wang et al, Surf. Sci. 575, 330 (2005).

[2] G. Henkelman and H. Jonsson, J. Chem. Phys. 22, 9978 (2000)

[3] P. Giannozzi et al, J. Phys.: Condens. Matter 21, 395502 (2009).

[4] J. Tersoff and D. R. Hamann, Phys. Rev. B. 31, 805 (1985).






LaPPS and INEO : Partnerships and Advances in the 2009-2010 Period
Leni Akcelrud

Laboratório de Polímeros Paulo Scarpa, Departamento de Química, Setor de Ciências Exatas, Usina Piloto A - Centro Politécnico da UFPR, Jardim das Américas, Curitiba-Pr, CEP: 81.531-990
The Paulo Scarpa Polymer Lab (Laboratorio de Polímeros Paulo Scarpa, LaPPS) has been created in August 2002 with the specific purpose of synthesizing advanced polymeric materials to provide the necessary raw materials to the associated groups of the Millenium Institute (IMMP). In this presentation we wish to disclose the main achievements in the last period, already in the Institute of Organic Electronics. During its eight years of existence, LaPPS has developed 41 polymer systems, including modifications of conventional materials, blends, and more importantly new structures, specially designed for organic electronics. The presentation will describe the groups that have used LaPPS polymers for various purposes in their specific projects, with emphasis in those that have had a closer exchange of ideas, students, and joint projects, experimental and/or theoretical. Apart from mere description, the aim of this presentation is to stimulate future work together with other groups and give the students a perspective of what can be done when efforts are shared for the science we need in our Country.




Molecular recognition and other possible interactions in biosystems
Osvaldo N. Oliveira Jr.

(1) Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil
An overview will be presented of research activities within INEO focusing on molecular-level interactions in various systems. Langmuir monolayers of phospholipids, for instance, have been used to mimic cell membranes and investigate the interaction with various molecules, including drugs, proteins, peptides and chitosans. Examples will be provided of the role of electrostatic interactions and of removal of a protein from the membrane. The molecular recognition capability of biomolecules is exploited in biosensors, with different platforms. Significantly, for sensors based on impedance spectroscopy, relaxation processes may depend on nonspecific interactions in a way that sensing units made with ultrathin films of polyelectrolytes may exhibit higher sensitivity than units containing enzymes that were supposedly capable of molecular recognition. Finally, novel methods using projection techniques will be discussed with regard to their use in sensing and biosensing.




Theoretical study of copper complexes
Marcos Brown Gonçalves (1), G.F. Caramori(2), A.M.D.C. Ferreira (2), H.M.Petrilli (1)

(1) Instituto de Física, Departamento de Física de Materiais e Mecânica, USP-SP,

(2) Instituto de Química, Departamento de Química Fundamental, USP-SP

e-mail: browngon@if.usp.br
Schiff bases are compounds with two imine groups that form very stable transition metal complexes. Schiff base–copper complexes have been intensively studied as mimics of copper proteins [1], potential metallodrugs [2] and self assembled materials to be applied as biosensor [3]. These copper complexes show diversity of geometric configurations, electronic structures and very good catalytic activity in reactions involving molecular oxygen. Here we study a series of Schiff base–copper complexes using electronic structure calculations in the framework of the Density Functional Theory (DFT). Our theoretical results for structural and electronic properties are compared with experimental data. As an important example, we investigate the binding energies in a series of copper complexes and the insertion of copper ion at the N-terminal binding site of the human serum albumin (HSA).
[1] AMDC Ferreira et al Inorg. Chem. Com. 6 (2003) 294

[2] AMDC Ferreira et al J Inorg Biochem 102 (2008) 1090

[3] AMDC Ferreira et al Eur. J. Inorg. Chem. 15, (2009) 2219




Organic Photovoltaic Devices: Study of Active Layers and Electrodes /

Dispositivos Fotovoltaicos Orgânicos: Estudo de Camadas Ativas e Eletrodos
Carla Daniele Canestraro , Lucimara Stolz Roman (Supervisor) (1)

(1) Programa de Pós-Graduação em Engenharia e Ciência dos Materiais, Departamento de Física – Universidade Federal do Paraná

e-mail: canestraro@ufpr.br
In this work, we present studies of electrodes and active layers in the development of organic solar cells. The tin oxide (SnO2) presents interesting features for application as transparent electrode: when deposited on a glass substrate to form thin film, presents semi-transparent to visible light spectrum and is capable of conducting electricity. The optimization of electrical characteristics is made by doping the oxide with fluorine. We present experimental results and theoretical characterization of the oxides without doping, moderate doping and high doping of fluorine.

The organic photovoltaics have been characterized based on two conjugated polymers: the polythiophene (PT) and a new derivative of thiophene, the poly (9,9 '-dioctyl-2 ,7-fluorenedyilvinylene-co-5, 5'-(benzo [ 1,2,5] thiadiazole-4, 7dyil) dithiophene) (PFTBT). The deposition of the active layer of the first polymer is made by electrochemistry and the devices were made in monolayer structure, showing good results for external quantum efficiency. The fabrication of fotodetectors devices allowed the application of technological devices in arrays of positional detection. The active layers generated by the second polymer were obtained by chemical deposition. Photovoltaic results are presented in three different structures: monolayer, bilayer and bulk heterojunction. Bilayer devices appear more efficient than the bulk heterojunction. One of the findings of this difference is the estimate for the rate of excitons generated in the active layer: this value is larger for the heterojunction case, however, the probability to exciton dissociation in free charges is lower when compared to bilayer devices.

Nanocomposites were also studied for application in photovoltaics: mixtures of conjugated polymer with carbon nanotubes and mixtures of conjugated polymer with gold nanoparticles. Two polymers were studied in the first case, the commercial Poly (3-hexyl thiophene) (P3HT) and non-commercial poly (9,9-di-hexilfluorenodiil-vinylene-alt-1 ,4-phenylenevinylene) (PDHFPPV). The interaction between different polymers and carbon nanotubes are presented in terms of optical and electrical characterization. The insertion of gold nanoparticles in a polymer matrix P3HT show the decrease in efficiency of photo-conversion when these materials are studied as active layers in photovoltaic devices. This may be associated with difficulty in transferring charges from nanoparticles to the polymer, due to the passivating layer capping the nanoparticles.





Electroluminescence of multi-layer devices using a new terbium

β-diketonate complex as emitting layer
A. Pereira(1), G. Conte(2), H. Gallardo(2), W.G. Quirino(3), C. Legnani(3), M. Cremona(3,4) and I.H. Bechtold(1)

(1) Departamento de Física and (2) Departamento de Química, UFSC, Florianópolis, Brasil.

(3) LADOR – Laboratório de Dispositivos Orgânicos, Dimat, Inmetro, Duque de Caxias, RJ, Brasil.

(4) LOEM – Laboratório de Optoeletrônica Molecular, Depto. de Física, PUC, Rio de Janeiro, RJ,Brasil.

e-mail: bechtold@fsc.ufsc.br
Organic light-emitting diodes (OLEDs) have attracted great interest due to their potential applications in the development of new optoelectronic components such as full-color and flat panel displays [1–3]. Nowadays, there is a range of available luminescent materials that can be applied for OLEDs technology, such that by selecting an appropriate emitting compound it is possible to obtain the electroluminescence (EL) in the entire visible spectrum. Rare earth (RE) ions have spectroscopic characteristics to emit light in narrow lines, which makes RE complexes with organic ligands candidates for full color OLED application. In particular, Betha-diketone rare earth (RE3+) complexes show high fluorescence emission efficiency due to the high absorption coefficient of the Betha-diketone. Energy transfer can be achieved efficiently when appropriate organic ligands are selected, which is known as antenna effect.

The aim of this work was to present the electroluminescent properties of devices containing multiple layers OLEDs using a new Terbium(Tb) Betha-diketonate complex, ([1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline) Tb (acetilacetona-ACAC), as electron emitting layer. The device were fabricated with the following structure ITO/CuPc/NPB/CBP:Tb/BCP/Al. All the films were deposited by thermal evaporation carried out in a high vacuum system attached to glove boxes for sample manipulation in a controlled environment. The fabricated devices show a typical diode behavior with a low threshold bias voltage. The OLEDs based on this complex presented photoluminescence and electroluminescence due to the atomic transitions characteristic of the Tb3+, with typical green emission as a sharp band at 546 nm. This terbium complex seems to be a promising material for OLED applications.


[1] J. Kido, Y. Okamoto, Chem. Rev. 102, 2537 (2002).

[2] C. Adachi, M.A. Baldo, S.R. Forrest, J. Appl. Phys. 87, 8049 (2000).

[3] W.G. Quirino, C. Legnani, R. dos Santos, K. Teixeira, M. Cremona, M. Guedes, H.F. Brito, Thin Solid Films 1096, 517 (2008).




Titanium dioxide in hybrid photovoltaic solar cells
F.D. Brandão (1), B.C.Ricci (1), A.P.L.Cota (1), A.P.Ibaldo (2), M.V.B. Pinheiro (1), L. A. Cury (1), K.Krambrock (1)

(1) Universidade Federal de Minas Gerais, Departamento de Física (2) Universidade de São Paulo, Instituto de Física de São Carlos.
In the last 20 years, a growing interest has been observed in the study of inorganic/organic hybrid devices, combing the good optical properties of semiconducting polymers with the peculiarities of inorganic nanoparticles. Solar cells based on thin films of such compounds have been attractive due to the potential technology for the manufacture of low-cost devices. The aim of the present work is to study the application of nanostructured titanium dioxide, TiO2, in hybrid photovoltaic devices. For these applications the important structural phase of TiO2 is the anatase phase, which has an energy gap of about 3.2 eV and can be produced by low-cost chemical methods with the sol-gel or co-precipitation processes. TiO2 is non-stoichiometric which leads to n-type conductivity due to the incorporation of oxygen-deficient defects. For applications in hybrid solar cells, the most important parameters of TiO2 are the high surface area (up to 300 m2/g), relative good electron mobility (10-4 m2/Vs) and the high work function (5.1eV), which makes the material a good electron acceptor (~ 10-15 s).

In this talk we present some of our studies related to the characterization of nanoparticles and nanostructured TiO2 thin films in both, the anatase and the rutile phase. For the characterization X-ray diffraction, SEM, AFM, BET, UV-VIS, electron paramagnetic resonance (EPR) and electrical measurements were applied. Hybrid solar cells of type ITO/TiO2/polymer(P3HTorBDMO-PPV)/Au were also produced and characterized.

The main propose of our work is to improve the superficial and interfacial area between TiO2 and polymer and the electrical conductivity inside the TiO2 layer. Our thin nanostructured TiO2 films show good optical homogeneity, however, the superficial area with 10 m2/g is low, and the resistivities are high, showing potential barrier of about 0.7eV. Nowadays, we are working on enhancement of the superficial area, the pore diameter and the morphology of TiO2 nanoparticle film by different thermal treatments or by using latex spheres as a template. The latter is done in collaboration with the group of Professor Maria Luísa Sartorelli of Federal University of Santa Catarina (UFSC). Furthermore, we are working on the improvement of the electrical conductivity by the reduction of the nanoparticle during synthesis without affecting the crystallization. In addition, in order to enhance the capture of electrons from the polymer and to reduce recombination of photo-excited carriers at the interface polymer/metaloxide, we are trying to control intrinsic defects in the TiO2 film and to dope the TiO2 with nitrogen, which is an acceptor. As an example for the characterization of intrinsic defects in reduced and oxidized bulk and nanostructured TiO2, we present our recent EPR results on Ti interstitials and the oxygen vacancy [1, 2].
[1] F. Brandão, Dissertação de mestrado, UFMG, Brazil (2008).

[2] F. D. Brandão, M.V.B. Pinheiro, G.M. Ribeiro, G. Medeiros-Ribeiro, K. Krambrock, Phys. Rev. B 80, 235204 (2009).






Comparative Study of MDMO-PPV Thin-Film Transistors
M.R. Cavallari (1), K.F. Albertin (1), G. Santos (1), C.A.S. Ramos (1), I. Pereyra (1), F.J. Fonseca (1), A.M. Andrade (2)

(1) EPUSP. (2) IEE-USP

e-mail: rcavallari@lme.usp.br, fernando.fonseca@poli.usp.br
Flexible displays and sensors in the field of organic or plastic electronics research have experienced dramatic increase in the current decade, involving many academic and industrial research efforts [1]. Conjugated polymers as poly[2-methoxy-5-(3’,7’-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) are solution processed and, for this reason, excellent candidates for low-cost and large-area electronics. Particularly due to the emerging necessity of non-conventional energy supply, MDMO-PPV has been thoroughly studied in solar cells [2], but this polymer can also be used in light-emitting diodes (LED) [3] and transistors for active-matrix organic displays (AMOLED) [4].

In this context, MDMO-PPV thin-film transistors, utilizing thermally grown SiO2 (250–500 nm) and PECVD SiOxNy (100–500 nm) as gate dielectric layer, were studied. Thermally grown silicon dioxide on highly-doped silicon substrate was utilized for comparative purposes. Insulators properties were controlled by ellipsometry, profilometry and by characterization of MOS capacitors. Whenever it was possible, devices with different insulators shared the same fabrication processes, being this condition essential to enable any comparison, as performance is intrinsically correlated to process parameters. Finally, SiOxNy was applied on glass-ITO substrates (Delta, unpolished, 30–60 /sq.) and resultant TFT performance was then compared to the previous ones on Si wafers.

Our results demonstrate that SiOxNy can replace SiO2 in OTFTs and could be used on ITO-covered glass or even flexible substrates, since they can be obtained at low deposition temperatures. Charge carrier mobility – h ≈ 1.1×10-4 cm2/Vs – was at least two times higher for PECVD silicon oxynitride on p+-Si substrate than silicon dioxide, probably due to the higher dielectric constant and higher charge concentration in the channel. MDMO-PPV OTFTs obtained could integrate LEDs for AMOLED displays, but also logic circuits due to the ambipolar behavior of this polymer. For future studies, contact resistance should be studied by choosing a more appropriate model, but also the variation of OTFT parameters with time, temperature and electric field. Characteristics of the TFTs used in backplanes must be reliably predictable. Obtaining lower carrier concentrations in the channel but at the same time attaining high currents for controlling a LED may need a further look too.
[1] Th.B.Singh and N.S.Sariciftci, Annu. Rev. Mater. Res. 36, 199 (2006).

[2] A.Pivrikas et al., Prog. Photovolt: Res. Appl. 15, 677 (2007).

[3] A.L.Alvarez et al., IEEE Trans. Elect. Dev. 55, 674 (2008).

[4] C.Tanase et al., Phys. Rev. Lett. 91, 216601 (2003).


OLEDs: terms, definitions and standards
E. C. Burini Junior (1), E. R. Santos (3), G. Santos (2), M. R. Cavallari (2), F. J. Fonseca (2), A. M. Andrade (1)

(1) IEE-USP (2) PSI EPUSP (3) PMT EPUSP

e-mail: elvo@iee.usp.br
In the early 1970 the devices called Solid State Light Sources - SSLSs were producing monochromatic light only. The anticipation of applications to the future, that could be designed and allocated to the LED, it was restricted to areas of displays and signaling. Especially because the device efficiency conversion from electricity to light was very low, and at that time there was not any potential that could be attributed to them to replace bulbs in general lighting service [1]. In the year 2009 many events took place that marked showed the largest international market penetration of OLED technology [2] and in the middle of this same year conventional LED (not organic) catalog was achieved [3], it indicates the possibility of this new LED to provide level of luminous efficiency greater than T5 fluorescent tubes (100 lm / W), but this new fluorescent technology facilities has not penetrated brazilian market yet. Laboratory facilities are being set at USP for the characterization activities to electroluminescent devices, as part of multidisciplinary interaction of Organic Electronics, and it have indicated the need to establish its own procedure and terminology. This paper presents results that were obtained with focus directed to these issues, mainly with reference at international standards (International Electrotechnical Commission - IEC) to organic electroluminescent devices. With a focus on terminology, a discussion is presented on terms taken from the literature and that are used to indicate the device into conduction condition, and presented the term that is standard in Brazil (tensão de limiar). As the central part of this work results and topics related to international standardization are considered. This comes from the consideration of a version of terminology available to OLED displays (IEC 62341-1-2) [4] and another two documents that consider methods for measuring optical and electro-optical devices parameters [5,6] close the discussion about standard characterization of electroluminescent devices. The establishment of local technical standards, aligned to the international sector for OLEDs is introduced. As the next steps, it is proposed activity that to seek for harmonization in the terminology of OLEDs displays [4], that must be followed by standard methods for parameters of measurement [5].
[1] E.W. Brander, et al, Lighting Res. Technol, v.5, n.3, p.145-155 (1973).

[2] IEC 62341-1-1 Organic light emitting diode (OLED) displays – Part 1-1 (2009).

[3] Catálogo OSRAM (2009).

[4] IEC 62341-1-2 (Ed. 1.0) Organic light emitting diode displays - Part 1-2, 57p., (2007).

[5] IEC 62341-6-1 (TC 110/129/CDV) Organic Light Emitting Diode Displays - Part 6-1: Measuring Methods of Optical and Optoelectrical Parameters. 26p., (2007).

[6] Commission Internationale de L’Éclairage - CIE 127 (2007).






Penicillin biosensor based on field-effect devices functionalized with layer-by-layer assembly of carbon-nanotubes
J. R. Siqueira Jr. (1,2), V. Zucolotto (1), M. J. Schöning (2), O. N. Oliveira Jr. (1)

(1) Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brasil

(2) Institute of Nano- and Biotechnologies, Aachen University of Applied Sciences,

Campus Jülich, Germany
The integration of nanomaterials and biological systems into electrical devices is advantageous for detection of biological species. In this context, carbon nanotubes are promising candidates for a common platform suitable for electronic control and biological sensing. In this study, we describe a strategy for biosensing based on a field-effect transducer functionalized with an organic/inorganic nano-hybrid containing single-walled carbon nanotubes (SWNT) and polyamidoamine (PAMAM) dendrimers, via the layer-by-layer (LbL) technique. The generic approach was demonstrated by realising pH and penicillin sensors using a capacitive EIS (electrolyte-insulator-semiconductor) structure and LAPS (light-addressable potentiometric sensor) as field-effect transducer. The biosensors were prepared by means of adsorptive immobilization of the enzyme penicillinase onto the PAMAM/SWNT film. The incorporation of PAMAM/SWNT LbL films onto the surface of a field-effect device enhanced the sensitivity, stability and response time of the penicillin biosensor. The proposed approaches can be extended to further field-effect biosensors.
[1] J.R. Siqueira Jr., Biosens. Bioelectron. 25, 497 (2009)

[2] J.R. Siqueira Jr., J. Phys. Chem. C 113, 14765 (2009)






Magnetic and Hyperfine Properties in metal complexes
H. M. Petrilli (1), M. Brown Gonçalves(1), F.C.D.A. Lima(1), P.A.D.Petersen(1), R. R. Nascimento(1),R.N.Igarashi(1),N.Sodre(1)

(1) Universidade de São Paulo, Instituto de Física, DFMT, Grupo Nanomol,



e-mail:hmpetril@if.usp.br

I will focus on recent applications, of ab initio electronic structure calculations to study the local magnetism, hyperfine and structural properties of metal complexes. These ab-initio studies are performed in the framework of the Kohn-Sham scheme of the Density Functional Theory (DFT), in our group. Special attention will be given to M-DNA and Cd ( Ag) complexes with Thiocrownethers. The later is discussed in relation to measurements performed using the Perturbed Angular Correlations technique, in the literature.



Palestra Convidada:


NAMITEC – Research in Micro and Nanoelectronics Systems

Antonio Luis Pacheco Rotondaro, PhD

Coordenador Geral de Tecnologias da Informação

Centro de Tecnologia da Informação Renato Archer


RESUMO

O NAMITEC é um Instituto de Ciência e Tecnologia que está estruturado como uma rede de centros de pesquisa. O seu objetivo é desenvolver pesquisa na área de micro e nano sistemas. Atualmente o NAMITEC é composto por 23 centros de pesquisa distribuídos em 13 estados. O projeto NAMITEC foi iniciado em 2001 e está na sua terceira fase com previsão de conclusão para 2014. O NAMITEC possui 5 macro áreas de atuação: a) ‘Systems-On-a-Chip’ e rede de sensores; b) Projeto de circuitos integrados; c) Ferramentas de projeto automatizado de CIs; d) Componentes semicondutores; e) Novos materiais e Técnicas de fabricação. O NAMITEC tem como prioridade a formação de recursos humanos nas suas áreas de atuação e transferência de conhecimento a indústria e a sociedade. O NAMITEC está sediado no Centro de Tecnologia da Informação Renato Archer uma Unidade de Pesquisa do Ministério da Ciência e Tecnologia localizado em Campinas no estado de São Paulo.










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