Papers by Gabriela Porcal
Journal of Photochemistry and Photobiology A-chemistry, 2008
Journal of Photochemistry and Photobiology A-chemistry, Sep 1, 2017
Highlights The photophysics of thionine was investigated in reverse micelles (RMs) of AOT and B... more Highlights The photophysics of thionine was investigated in reverse micelles (RMs) of AOT and BHDC. The dye molecules remain at the interface sensing a less polar medium in both RMs. Apparent triplet quenching rate constants by tri-ethanolamine (TEOA) and tri-butylamine (TBA) were determined in RMs. Triplet quenching by TEOA leads to a non-exponential decay in the RMs. The triplet state is efficiently quenched by hydrophilic TEOA.
Journal of Photochemistry and Photobiology A-chemistry, Mar 1, 2011
The photodeoxygenation of the synthetic dye resazurin in the presence of triethanolamine was inve... more The photodeoxygenation of the synthetic dye resazurin in the presence of triethanolamine was investigated in water, CTAC and SDS direct micelles, AOT and BHDC reverse micelles, and soybean lecithin microemulsions (LEC). In all cases the only product observed was the deoxygenated dye resorufin. Triplet and reaction quantum yields were determined in all media. The photoreaction proceeds more efficiently in the microheterogenous systems with positive interface, CTAC and BHDC, while the lower yield is observed in AOT, SDS and LEC. The initial step in the mechanism is the interaction of the triplet state of the dye with the amine, and the effect of the interface is interpreted by a decrease of the recombination rate of the radicals formed in the initial electron transfer step. Negative and zwitterionic interfaces have no effect on the quantum yield.
Colloid and Polymer Science, Nov 21, 2014
This work shows the feasibility of using the photoinitiating system composed by the xanthene dye ... more This work shows the feasibility of using the photoinitiating system composed by the xanthene dye Eosin-Y and triethanolamine on the polymerization of acrylamide in benzyl-hexadecyl-dimethylammonium chloride (BHDC) reverse micelles. Molecular weights of polyacrylamide (MW PAA) in the order of 10 5 and conversions up to 90 % are obtained. The size of the latex particles is in the range of the nanometers (d<50 nm). The effect of water content and concentrations of surfactant, amine, dye, and monomer on the particle size and MW PAA are examined. Only the amine and monomer concentrations affect the MW PAA. These results are interpreted on the basis of an exchange mechanism between micelles. Practically no effect on hydrodynamic diameters is observed when the value of MW PAA is doubled. This is ascribed to a supercoiled structure of PAA inside of micelles. Our results also suggest that the polymer properties can be modulated by appropriate combination of the dye/surfactant electrical charges.
Journal of Photochemistry and Photobiology A-chemistry, Dec 1, 2011
ABSTRACT The photophysics of safranine-O (3,7-diamino-2,8-dimethyl-5 phenyl phenazinium chloride,... more ABSTRACT The photophysics of safranine-O (3,7-diamino-2,8-dimethyl-5 phenyl phenazinium chloride, SF) and phenosafranine (3,7-diamino-5-phenyl phenazinium chloride, PSF) was investigated in reverse micelles (RMs) of the cationic surfactant benzyl hexadecyl dimethylammonium chloride (BHDC). The excited singlet state properties were measured by absorption and fluorescence spectroscopy. All the measurements indicate that both dyes are localized in the interface, sensing a medium of lower polarity than water. Stokes’ shift increases and fluorescence quantum yield decreases with increasing the water content, but never reach the values or pure water. The triplet state properties of the dyes in RMs were investigated by laser flash photolysis. The maximum of the T–T absorption spectra in RMs confirms that, in spite of their positive charge, the dyes remain at the interface co-micellizing with BHDC. The triplet lifetime is much longer in the RMs than in homogeneous organic solvents. The two dyes present a different dependence of their photophysical properties with the water content. The two methyl groups in the ring of SF produce a stronger preference of the dye for a hydrophobic environment, and consequently a deeper location in the interface closer to the organic phase. A remarkable difference is observed in the triplet quenching by aliphatic amines. While the quenching by hydrophobic tributylamine is much lower in BHDC/benzene RMs than in a homogeneous solvent, the hydro soluble triethanolamine is near two orders of magnitude more effective in the RMs than in homogeneous solution. This is explained by the different local concentration of the amines in the interface.
Social Science Research Network, 2023
Photochemical & Photobiological Sciences
The effect of Riboflavin-5′-phosphate (RFPO 4) sensitization on photocatalytic properties of TiO ... more The effect of Riboflavin-5′-phosphate (RFPO 4) sensitization on photocatalytic properties of TiO 2 film was studied. RFPO 4 was adsorbed on film surface to investigate the photophysical properties of TiO 2 upon blue-light photoexcitation. The film was characterized through scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and diffuse reflectance spectroscopy. The efficiency of the TiO 2 /RFPO 4 film was tested for pollutant elimination in aqueous media in a visible-light-driven system. The phenol paradigmatic model was employed in an aqueous solution as a contaminant target. TiO 2 /RFPO 4 sensitized photodegradation of phenol, which produces catechol, hydroquinone, and benzophenone, was monitored by absorption spectroscopy and HPLC. The results indicated that phenol degradation with TiO 2 /RFPO 4 film was due to the photogeneration of two reactive oxygen species, singlet molecular oxygen (O 2 (1 Δ g)) and superoxide radical anion (O 2 •-) identified through specific detection techniques. The presence of O 2 (1 Δ g) is reported here for the first time as generated from a sensitized TiO 2 film upon visible-light photoirradiation. Based on the photophysical determinations, a photocatalytic mechanism for TiO 2 /RFPO 4 was established.
Este trabajo fue realizado en el marco del Programa Nexos: articulación entre escuelas secundaria... more Este trabajo fue realizado en el marco del Programa Nexos: articulación entre escuelas secundarias y la universidad, convocado por el área de los Centros Regionales de Planificación de la Educación Superior (CPRES) de la Secretaría de Políticas Universitarias (SPU) del Ministerio de Educación de la Nación; extendido desde Octubre de 2017 a Octubre de 2018. Implicó la participación conjunta del Ministerio de Educación de la Provincia de Córdoba y la Universidad Nacional de Río Cuarto, ambas instituciones a través de los profesores de escuelas de nivel secundario de Río Cuarto y su región y profesores de diferentes carreras de grado de esta universidad. El eje del Programa se centró en la articulación entendida como una tarea compartida entre los profesores de nivel secundario y de nivel universitario en torno a tres líneas de acción: a- Reconocimiento de las diferentes opciones institucionales y propuestas de formación de educación universitaria y estrategias de aproximación a la vid...
New Journal of Chemistry, 2019
This work investigates CdS nanocrystal synthesis by applying chemometric tools. Very good reprodu... more This work investigates CdS nanocrystal synthesis by applying chemometric tools. Very good reproducibility of nanocrystals of CdS was obtained.
Analytical Chemistry, 2001
An electrochemical immunosensor for direct detection of the 15.5-kDa protein interferon-gamma (IF... more An electrochemical immunosensor for direct detection of the 15.5-kDa protein interferon-gamma (IFN-gamma) at attomolar level has been developed. Self-assembled monolayers (SAMs) of cysteine or acetylcysteine are formed on electropolished polycrystalline Au electrodes. IFN-gamma adsorbs physically to each of these SAMs. With injections of 100 mM KCl, IFN-gamma can be removed in the flow without damaging the acetylcysteine SAM. However, the cysteine SAM is affected by these KCl injections. In an on-line procedure in the flow, a specific antibody (MD-2) against IFN-gamma is covalently attached following carbodiimide/succinimide activation of the SAM. The activation of the carboxylic groups, attachment of MD-2, and deactivation of the remaining succinimide groups with ethanolamine are monitored impedimetrically at a frequency of 113 Hz, a potential of +0.2 V versus SCE, and an ac modulation amplitude of 10 mV. Plots of the real (Z') and imaginary (Z") component of the impedance versus time provide the information to control these processes. In the thermostated setup (23.0 degrees C), samples of unlabeled IFN-gamma (in phosphate buffer pH 7.4) are injected and the binding with immobilized MD-2 is monitored with ac impedance or potential-step methods. While the chronoamperometric results are rather poor, the ac impedance approach provides unsurpassed detection limits, as low as 0.02 fg mL-1 (approximately 1 aM) IFN-gamma. From a calibration curve (i.e. Z" versus the amount injected), recorded by multiple 50-microL injections of 2 pg mL(-1) of IFN-gamma, a dynamic range of 0-12 pg mL(-1) could be derived. However, when nonspecific adsorption is taken into account, which has been found to be largely reduced through injections of 100 mM KCl, a much smaller dynamic range of 0-0.14 fg mL(-1) remains. The immunosensor can be regenerated by using a sequence of potential pulses in the flow by which the SAM with attached MD-2 and bound IFN-gamma is completely removed. When the developed procedures described above are repeated, the response of the immunosensor is reproducible within 10%.
Journal of Photochemistry and Photobiology A: Chemistry
Nanomedicine (London, England), Mar 29, 2018
Assess biocompatibility, uptake and photodynamic therapy (PDT) mechanism of metallated porphyrin... more Assess biocompatibility, uptake and photodynamic therapy (PDT) mechanism of metallated porphyrin doped conjugated polymer nanoparticles (CPNs) in human brain and colorectal tumor cells and macrophages. CPNs were developed employing 9,9-dioctylfluorene-alt-benzothiadiazole, an amphiphilic polymer (PS-PEG-COOH), and platinum octaethylporphyrin. T98G, SW480 and RAW 264.7 cell lines were exposed to CPNs to assess uptake and intracellular localization. Additionally, a PDT protocol using CPNs was employed for the in vitro killing of cancer and macrophage cell lines. CPNs were well incorporated into glioblastoma and macrophage cells with localization in lysosomes. SW480 cells were less efficient incorporating CPNs with localization in the plasma membrane. In all cell lines PDT treatment was efficient inducing oxidative stress that triggered apoptosis.
Journal of Photochemistry and Photobiology A: Chemistry, 2017
Colloid and Polymer Science, 2014
Physical Chemistry Chemical Physics, 2003
Journal of Photochemistry and Photobiology A: Chemistry, 2008
Journal of Photochemistry and Photobiology A: Chemistry, 2013
ABSTRACT The photopolymerization of acrylamide (AA) in reverse micelles (RMs) of benzyl hexadecyl... more ABSTRACT The photopolymerization of acrylamide (AA) in reverse micelles (RMs) of benzyl hexadecyl dimethylammonium chloride (BHDC) was investigated. The polymerization was performed by irradiation in the 500 nm region of the spectrum, employing as photoinitiating system the synthetic dye safranine-O and triethanolamine (TEOA) as co-initiator. The characterization of the nanoparticles of polyacrylamide was done by dynamic light scattering. Molecular weight determinations were carried out by viscosimetry. Small nanoparticles of polyacrylamide are formed with a low polydispersity and a molecular weight close to 106. The results were compared with those in AOT (sodium bis(2-ethylhexyl) sulfosuccinate) RMs. Laser flash photolysis was used to investigate the photoinitiating mechanism. The maximum of the T–T absorption spectra in RMs confirms that, in spite of its positive charge, the dyes remain at the interface co-micellizing with BHDC. The triplet lifetime is much longer in the RMs than in homogeneous organic solvents. The triplet quenching by TEOA was very much more effective in the RMs than in a homogeneous solvent. The quantum yield of formation of active radicals was evaluated from the transient absorption spectra. It was concluded that they are generated by an intermicellar electron transfer process followed by an intramicellar proton transfer reaction. The quantum yield was found to be 0.2 ± 0.02. A similar radical yield in a homogeneous solvent requires an amine concentration near 50 times higher.
Journal of Photochemistry and Photobiology A: Chemistry, 2011
The photodeoxygenation of the synthetic dye resazurin in the presence of triethanolamine was inve... more The photodeoxygenation of the synthetic dye resazurin in the presence of triethanolamine was investigated in water, CTAC and SDS direct micelles, AOT and BHDC reverse micelles, and soybean lecithin microemulsions (LEC). In all cases the only product observed was the deoxygenated dye resorufin. Triplet and reaction quantum yields were determined in all media. The photoreaction proceeds more efficiently in the microheterogenous systems with positive interface, CTAC and BHDC, while the lower yield is observed in AOT, SDS and LEC. The initial step in the mechanism is the interaction of the triplet state of the dye with the amine, and the effect of the interface is interpreted by a decrease of the recombination rate of the radicals formed in the initial electron transfer step. Negative and zwitterionic interfaces have no effect on the quantum yield.
Dyes and Pigments, 2011
Photophysical properties of resazurin and resorufin were investigated in a homogeneous solution o... more Photophysical properties of resazurin and resorufin were investigated in a homogeneous solution of binary solvent mixtures (isooctane/1-propanol) and in soybean lecithin microemulsions. Resorufin does not show any important changes in the position of either absorption or fluorescence bands when lecithin is added to the mixture isooctane-1-propanol; when microemulsions are formed by the addition of water, a new band appears in
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Papers by Gabriela Porcal