Debora Balogh
Universidade de São Paulo, Physics and Materials Science, Department Member
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Thermal Lens Spectrometry (TLS), as well as all photothermal methods, rely on the determination of the fraction of absorbed energy converted in heat (ϕ), which in turn is related to photoluminescence quantum efficiency (Á). In this study,... more
Thermal Lens Spectrometry (TLS), as well as all photothermal methods, rely on the determination of the fraction of absorbed energy converted in heat (ϕ), which in turn is related to photoluminescence quantum efficiency (Á). In this study, we have used TLS to measure Á of Poly(3-hexylthiophene) (P3HT) dissolved in chloroform as a function of concentration and excitation wavelength. For samples synthesized by oxida-tive polymerization (∼74% HT content), Á = 0.39 ± 0.02 was found to be constant with excitation energy (UV–vis, 335–514 nm) and concentration, from 10 −4 to 0.6 mg/mL. The value of Á was practically the same as that of a commercial regioregular P3HT (>95% HT content), measured under the same conditions. The photodegradation effect was also quantitatively analyzed. Although the average emission wavelength of the photo-degraded sample depends on excitation wavelength, both ϕ and Á are constant in the UV–vis range.
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In this paper the large-scale mass transport mechanism is used to microstructure azopolymeric films, aiming at controllable hydrophobic surfaces. Using an Ar + laser with intensity of 70 mW/cm 2 , we produced egg-crate-like surfaces with... more
In this paper the large-scale mass transport mechanism is used to microstructure azopolymeric films, aiming at controllable hydrophobic surfaces. Using an Ar + laser with intensity of 70 mW/cm 2 , we produced egg-crate-like surfaces with periods from 1.0 to 3.5 µm that present distinct wetting properties. The static contact angle of water was measured on the microstructured surfaces, and the results revealed an increase of approximately 9 for a surface pattern period of 2 µm. Our results indicate the use of the microstructuring method described here for the fabrication of devices with controllable hydrophobicity.
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IntroductionAzoaromatic Compounds: Synthesis, Functionality and Film FabricationApplicationsFinal Remarks and ProspectsAcknowledgementsReferences
In this review, we summarize some of our efforts in parallel with other research groups' studies in designing, assembling, and structurally and functionally characterizing nanostructured materials using optical waveguide spectroscopy... more
In this review, we summarize some of our efforts in parallel with other research groups' studies in designing, assembling, and structurally and functionally characterizing nanostructured materials using optical waveguide spectroscopy (OWS). We focus on the study of porous nanostructures: (i) cylindrical thin films (ii) mesoporous thin films, and (iii) nanorod arrays as optical waveguides for high sensitivity biosensing. We discuss the waveguiding properties of these thin films in the visible wavelengths and theoretical description of nanostructured hybrid optical waveguides by effective medium theory (EMT). We demonstrate how high sensitivity can be achieved by modifying pore walls with small functional groups (i.e. silanes) as well as polypeptide brushes. When using also mesoporous semiconducting materials (TiO2) hybrid architectures, simultaneous measurement of OWS and electrochemistry can be possible with very interesting photophysical properties that can be useful also for s...
The hydrodynamic volume concept can be used effectively with gel-permeation chromatography (GPC) and viscosity data to estimate the molecular weight of a variety of polymers. In this work, the Mark-Houwink coefficients (α and K) for the... more
The hydrodynamic volume concept can be used effectively with gel-permeation chromatography (GPC) and viscosity data to estimate the molecular weight of a variety of polymers. In this work, the Mark-Houwink coefficients (α and K) for the poly[p-(acetoxystyrene)] homopolymers (PASt) were determined by correlating between their weight average molecular weight (M w) values, determined by gel-permeation chromatography (GPC) relative to polystyrene standards, and their measured intrinsic viscosity values ([η]). The viscosity average molecular weight (M v) of any unknown PASt sample may be estimated by first measuring the sample's intrinsic viscosity, and then applying these α and K values in the Mark-Houwink equation.
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Poly(p-phenylene vinylene) (PPV) derivatives are well known for their applications in polymer light emitting diodes (PLEDs). These derivatives are highly susceptible to photooxidation though, which is mainly caused by the scission of the... more
Poly(p-phenylene vinylene) (PPV) derivatives are well known for their applications in polymer light emitting diodes (PLEDs). These derivatives are highly susceptible to photooxidation though, which is mainly caused by the scission of the vinyl double bond on the polymer backbone. In this work, we show that Langmuir-Blodgett (LB) films are less degraded than cast films of a PPV derivative (OC1OC6-PPV).
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The generation of surface anisotropy by photochemical means has been proposed as an attractive method to align liquid crystals. In this paper, we present an experimental study of the alignment induced on a liquid crystal by a polymer film... more
The generation of surface anisotropy by photochemical means has been proposed as an attractive method to align liquid crystals. In this paper, we present an experimental study of the alignment induced on a liquid crystal by a polymer film containing azo-dye groups in the side chain. Optical measurements were performed in nematic liquid crystal cells to determine the azimuthal and zenithal anchoring strengths as a function of the irradiation energy and chromophores concentration. It was observed that the director tends to align perpendicular to the polarization direction of the incident light and the orientation process consists essentially of a rotation of the director in the plane parallel to the boundary surfaces. However, the concentration of azo-dye groups in the polymer film must exceed a minimum value to get a macroscopical effect on the liquid crystal alignment. It is shown that the azimuthal anchoring strength can be varied two orders of magnitude by controlling the irradiat...
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... Gonçalves2, DT Balogh2 1.FCT-Unesp Presidente Prudente Rua Roberto Simonsen, 305 CP 467 CEP19060-900 Presidente Prudente, SP, Brasil; 2 ... fabricated by spreading a solution of P3HT in chloroform (0.2 mg/ ml) onto ultra pure water... more
... Gonçalves2, DT Balogh2 1.FCT-Unesp Presidente Prudente Rua Roberto Simonsen, 305 CP 467 CEP19060-900 Presidente Prudente, SP, Brasil; 2 ... fabricated by spreading a solution of P3HT in chloroform (0.2 mg/ ml) onto ultra pure water subphase (Millipore Milli-Q system ...
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The characteristics of Langmuir monolayers of lignins isolated via distinct methods, viz. acetone–oxygen–organosolv (termed Lignin-1), Kraft (Lignin-2), acetic acid–organosolv (Lignin-3) and acetone–organosolv (Lignin-4), are investigated... more
The characteristics of Langmuir monolayers of lignins isolated via distinct methods, viz. acetone–oxygen–organosolv (termed Lignin-1), Kraft (Lignin-2), acetic acid–organosolv (Lignin-3) and acetone–organosolv (Lignin-4), are investigated using surface pressure and surface potential measurements. The overall behavior of these lignins is essentially the same, but some differences were observed which are attributed to the relative amount of carbonyl groups in the lignin
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ABSTRACT Schottky diode structures employing chlorine doped MH-PPV (Methoxy-Hexiloxy-P-Phenylene-Vinylene) as active layers were prepared to study the electronic possibilities of this conjugated polymer. MH-PPV films were deposited by... more
ABSTRACT Schottky diode structures employing chlorine doped MH-PPV (Methoxy-Hexiloxy-P-Phenylene-Vinylene) as active layers were prepared to study the electronic possibilities of this conjugated polymer. MH-PPV films were deposited by spin-coating technique on ITO (indium tin oxide) coated glass substrates. Aluminum contact was then vacuum evaporated. Dark conductivity characteristic is that of a rectifier diode. Upon illumination the device shows photovoltaic characteristics. When a voltage is applied, however, the structure shows electroluminescence with a peak at 606nm. In this sense, it is a reversible photonic device.
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ABSTRACT Several studies on polythiophene gas sensors, based mainly on electrochemical and gravimetric principles can be found in the literature. However, other principles of gas detection, such as optical and thermal, are still little... more
ABSTRACT Several studies on polythiophene gas sensors, based mainly on electrochemical and gravimetric principles can be found in the literature. However, other principles of gas detection, such as optical and thermal, are still little studied. Optical sensing is suitable for remote detection and offers great versatility at low cost. Here, we report on the use of thin films of seven polythiophene derivatives as active layer in optical sensors for the detection of six volatile organic compounds (n-hexane, toluene, tetrahydrofuran, chloroform, dichloromethane and methanol) and water vapor, in concentration range of 500–30,000 ppm. The results showed that it is possible to use different polythiophene derivatives to differentiate VOCs by optical sensing. Differentiation can be performed based on the presence or not of response to an analyte and the sensitivity value of the sensors for the analytes. Another important feature is the lack of the effect of humidity on the response of most films, which could be a major drawback in the application of these sensors.
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... Marystela Ferreira a , Corresponding Author Contact Information , E-mail The Corresponding Author , Carlos JL Constantino a , Clarissa A. Olivati a , Débora T. Balogh b , Ricardo F. Aroca c , Roberto M. Faria b and Osvaldo N.... more
... Marystela Ferreira a , Corresponding Author Contact Information , E-mail The Corresponding Author , Carlos JL Constantino a , Clarissa A. Olivati a , Débora T. Balogh b , Ricardo F. Aroca c , Roberto M. Faria b and Osvaldo N. Oliveira, Jr b. ...
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Research Interests: Materials Science, Biomedical Engineering, Atomic Force Microscopy, Refractive Index, Contact angle, and 9 moreEnergy Dispersive X-Ray Analysis, Electrical Properties, Spectroscopic Ellipsometry, Work Function, Surface Energy, Absorption Spectra, Chemical Treatment, Indium tin oxide, and Light Emitting Diode
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ABSTRACT We report the control of Au nanoparticle (NP) formation by using shaped 30 fs pulses, in a solution containing HAuCl4 and chitosan. By using a sinusoidal spectral phase, a periodic train of pulses is generated. When the period of... more
ABSTRACT We report the control of Au nanoparticle (NP) formation by using shaped 30 fs pulses, in a solution containing HAuCl4 and chitosan. By using a sinusoidal spectral phase, a periodic train of pulses is generated. When the period of the pulse train matches certain Raman resonances of chitosan, the reducing agent of the process, an enhancement of the Au NP formation is observed. Theoretical quantum chemical calculations indicate that the outer groups of the chitosan are mostly influenced by low Raman frequencies, which is in reasonably agreement with the experimental data and indicates an enhancement in the Au NP formation as the pulse train period increases (low frequency).
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... Lignin from Sugar Cane Bagasse: Extraction, Fabrication of Nanostructured Films, and Application. AA Pereira, GF Martins, PA Antunes, R. Conrrado, D. Pasquini, AE Job, AAS Curvelo, M. Ferreira, A. Riul, Jr., and CJL Constantino.... more
... Lignin from Sugar Cane Bagasse: Extraction, Fabrication of Nanostructured Films, and Application. AA Pereira, GF Martins, PA Antunes, R. Conrrado, D. Pasquini, AE Job, AAS Curvelo, M. Ferreira, A. Riul, Jr., and CJL Constantino. Langmuir 2007 23 (12), 6652-6659. ...