Janaina Gomes - Academia.edu (original) (raw)

Papers by Janaina Gomes

The Angle Orthodontist, 2007

To evaluate in vitro the surface of elastomeric chains of different manufacturers to verify the p... more To evaluate in vitro the surface of elastomeric chains of different manufacturers to verify the presence of pathogenic microorganisms at the moment of unpacking and analyze a possible inhibitory effect of the elastomeric chain when exposed to microorganisms of the oral cavity, for example, Streptococcus mutans, Lactobacillus casei, and Candida albicans. Elastomeric chains from Ortho-Organizers Inc, 3M Unitek, and Dental Morelli were placed in petri plates with brain heart infusion agar medium and in sterile test tubes with brain heart infusion broth. The samples were incubated at 37 degrees C and analyzed at 24 hours, 48 hours, 3 days, and 7 days. In addition, elastomeric chains from the three manufacturers were placed in dishes, inoculated with microorganisms, incubated at 37 degrees C, and analyzed after 24 and 72 hours. No microorganism growth was detected after all incubation periods. No inhibition zones were identified surrounding the elastomeric chain. The results suggest that the fabrication of elastomeric chain is in accordance with biohazard concepts. However, careful manipulation is necessary to avoid colonization of pathogenic microorganisms since the composition of the elastomeric chains analyzed do not include antimicrobial agents.

Revista Brasileira de Fruticultura, 2009

Several fruits of native species of semi-arid region have great potential for commercialization, ... more Several fruits of native species of semi-arid region have great potential for commercialization, and among them there is the Spondias tuberosa. However, commercial cultivation of this species is limited by the difficulty of obtaining seedlings mainly depending on the dormancy of its seeds. Thus, the purpose of this study was to evaluate the seeds overcoming dormancy methods of Spondias Tuberosa to promote an increase in the rates of germination, uniformity and vigor of the seedlings. Two experiments were independently conducted. The treatments of the first experiments were: test, immersion of the seeds in water for 24 hours, immersion of the seeds in solution of gibberellic acid 1000 mg / L for 24 hours, scarification of seeds with sulfuric acid PA for 10 minutes and mechanical scarification of seeds. In the second experiment, the treatments consisted of planting the seeds with 0, 30, 60, 90, 120, 150, 180 and 210 days of storage in paper bags under laboratory conditions, at an average temperature of 22.5° C and relative humidity of 65%. In the first study it was found that there was a significant effect of the methods to seeds overcoming dormancy, concluding that the mechanical scarification is the best treatment, with an average germination rate in 60 days after planting 26.6%. In the second experiment, storage positively influenced the germination of seeds and seedlings vigor. The best results for uniformity and germination percentage (83%) were obtained between 120 and 210 days of seeds storage, while for the length and fresh weight of root, between 120 and 150 days.

We investigated the electrochemical oxidation of glycerol on low-index Pt single crystals in acid... more We investigated the electrochemical oxidation of glycerol on low-index Pt single crystals in acidic media (H 2 SO 4 and HClO 4 ) by cyclic voltammetry and Fourier Transform Infrared (FTIR) spectroscopy and we verified that this is a surface sensitive reaction. Pt(1 0 0) and Pt(1 1 0) surface structures favor the breaking of the C C C bond at low potentials (say 0.05 V), as seen by the formation of CO, one of the adsorbed residues of the glycerol dissociation, which poisons these surfaces even at high potentials. Pt(1 1 1) surface structure does not favor the C C C bond breaking at potentials as low as 0.05 V. However, Pt(1 1 1) is less poisoned by residues of glycerol dissociation and, for this reason, it is more active for glycerol oxidation than Pt(1 0 0) and Pt(1 1 0) at low potentials. Carbonyl containing compounds and CO 2 were detected as reaction products of the glycerol oxidation on all investigated single-crystal Pt surfaces. The ratio between CO 2 and carbonyl containing compounds is clearly much higher for Pt(1 0 0) and Pt(1 1 0) than for Pt(1 1 1).

Electrocatalysis, 2011

The electro-oxidation of glycerol on Au and Pt was studied in acid and alkaline media. The reacti... more The electro-oxidation of glycerol on Au and Pt was studied in acid and alkaline media. The reaction intermediates and products formed were determined by in situ Fourier transform infrared (FTIR) spectroscopy.

Electrocatalysis, 2012

In this paper we report a simple and environmentally friendly synthesis of silver nanoparticles (... more In this paper we report a simple and environmentally friendly synthesis of silver nanoparticles (AgNps) and their activities towards the oxygen reduction reaction (ORR). Ultraviolet spectroscopy (UV-vis) and transmission electron microscopy confirmed the formation of poly(vinyl pyrrolidone)-protected colloidal AgNps through direct reduction of Ag + by glycerol in alkaline medium at room temperature. For the ORR tests, the AgNps were directly produced onto carbon to yield the Ag/C catalyst. Levich plots revealed the process to occur via 2.7 electrons, suggesting that the carbon support contributes to the ORR. We discuss here possibilities of improving the catalytic properties of the Ag/C for ORR by optimizing the parameters of the synthesis.

Eclética Química, 2002

... Janaína Gomes; Osvaldo Antonio Serra; Ana Maria Pires ... 1 DANIELSON, E.; DEVENNEY, M.; GIAQ... more ... Janaína Gomes; Osvaldo Antonio Serra; Ana Maria Pires ... 1 DANIELSON, E.; DEVENNEY, M.; GIAQUINTA, D.; M.GOLDEN, JH; HAUSHALTER, R. C.; MCFARLAND, EW; POOJARY, DM; REAVES, CM; WEINBERG, WH; WU, X. D. X-ray powder structure of Sr2CeO4: a new ...

The Journal of Physical Chemistry B, 2006

Ethanol in an acidic solution-Pt(110) interface was studied by SFG spectroscopy (between 1820 and... more Ethanol in an acidic solution-Pt(110) interface was studied by SFG spectroscopy (between 1820 and 2325 cm -1 ) to explore primarily the effects of the alcohol concentration. Stretching bands of H-Pt (ca. 1970 or 2050 cm -1 ) and CO (ca. 1980 and 2040 cm -1 ) species, produced by the ethanol oxidation, were detected during the adsorption and oxidation of 0-1 mol L -1 ethanol in a 0.1 mol L -1 HClO 4 solution on the electrode surface. Hydrogen and CO coadsorb stably on Pt(110) between 0.05 and 0.15 V in ethanol-containing solutions. In this potential range, the blue shift of the hydrogen resonance (ca. 80 cm -1 ) reveals a weakening of the hydrogen bonding between adsorbed hydrogen and water molecules in the double layer. After the hydrogen desorption (0.15 V), the formation of compact CO islands, depending on the ethanol concentration, lifts the Pt(110) surface reconstruction. In ethanol-free solution, the surface remains reconstructed. The lower-frequency CO band is assigned to the CO species adsorbed on (1 × 2) reconstructed Pt(110) domains, having smaller local coverages, while the higher-frequency CO band is attributed to the close-packed CO species adsorbed on (1 × 1) patches. The reaction pathway forming CO 2 is less favored with increasing ethanol concentration.

Química Nova, 2004

Morphological and spectroscopic studies of Sr 2 CeO 4 blue phosphor in the form of fine particles... more Morphological and spectroscopic studies of Sr 2 CeO 4 blue phosphor in the form of fine particles prepared from a powdered multi-component precursor, via a combustion method, are reported. Samples were also prepared through a solid-state reaction and from a ...

Physical Chemistry Chemical Physics, 2013

Glycerol is at present abundantly co-produced in the biodiesel fabrication and can be used as fue... more Glycerol is at present abundantly co-produced in the biodiesel fabrication and can be used as fuel in Direct Glycerol Fuel Cells (DGFC) for cogeneration of electricity, value-added chemicals and heat. With this motivation, in the present work, we investigated at a fundamental level the oxidation of glycerol over glassy carbon (GC) supported Au nanoparticles in alkaline medium using cyclic voltammetry. By controlling the Au deposition time, we varied the GC supported Au coverage from 0.4% to 30% maintaining a regular particle size distribution with a mean particle size of about 200 nm. An influence of the carbon support on the activity of the GC-supported Au nanoparticles was evidenced. Results from studies on the oxidation of glycerol and ethylene glycol on Au and Pt nanoparticles supported on a glassy carbon, highly ordered pyrolytic graphite and dimensionally stable anode under different pH conditions indicate that the carbon support participates actively in the oxidation of glycerol and other alcohols. We propose that active oxygenated species are gradually formed on the glassy carbon by potential cycling (up to the saturation of the carbon area) and these oxygenated species are additional oxygen suppliers for the oxidation of glycerol residues adsorbed on the Au particles, following a mechanism consisting of the synergism of two active elements: gold and carbon.

Journal of Fluorescence, 2006

This work reports on the preparation of a luminescent blue-emitting rare earth (RE) Tm-doped oxid... more This work reports on the preparation of a luminescent blue-emitting rare earth (RE) Tm-doped oxide phosphor. Nanocrystalline RE2O3:Tm3+ particles were prepared via the combustion method using citric acid, glycine, or urea as fuels. Samples were doped with different percentages of the activator Tm3+. The post-annealing treatment was performed in air for all the samples, at temperatures ranging from 800 to 1100 degrees C, for 4 h. The samples were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL) and scanning electron and transmission microscopies (SEM and TEM) in order to determine the best synthetic procedure. The post-annealed powders showed blue emission with maximum at 452 nm characteristics for Tm3+ transition 1D2 --> 3H4 (under UV excitation at 360 nm). Samples, presented a tri-dimensional porous structure (50-200 nm) formed of spheroid particles with a diameter between 20 and 60 nm. The best luminescent material was obtained when urea was used to prepare nanoparticles of Gd2O3 doped with 0.5% Tm3+, and 1100 degrees C was used as the post-annealing temperature.

Journal of Electroanalytical Chemistry, 2011

In the present paper we investigated the electrochemical behavior of PVP on polycrystalline and s... more In the present paper we investigated the electrochemical behavior of PVP on polycrystalline and singlecrystal Pt electrodes. PVP hampered the characteristic hydrogen UPD and anion adsorption on all investigated surfaces. Several oxidation processes appeared in the anodic sweep with Pt(1 1 1) and Pt(1 0 0) being the most active for the oxidation processes. Repetitive cycling of the PVP ads -modified Pt(1 1 1) or Pt(1 0 0) electrodes in PVP-free aqueous H 2 SO 4 solution leads to a continuous suppression of the characteristic hydrogen UPD and anion adsorption as a consequence of PVP oxidation. However no PVP oxidation was observed when cycling the PVP ads -modified Pt(1 1 0) electrode in PVP-free aqueous H 2 SO 4 solution.

Electrochimica Acta, 2008

We have investigated the adsorbed intermediates of ethanol electro-oxidation at Pt(1 1 1), Pt(1 0... more We have investigated the adsorbed intermediates of ethanol electro-oxidation at Pt(1 1 1), Pt(1 0 0) and Pt(1 1 0) using FTIR and SFG spectroscopies. Mainly, we focus on the CO formation. The aim of the present work is to compare the responses coming from two different surface probes: FTIR spectroscopy and SFG spectroscopy. Between 1800 cm −1 and 2300 cm −1 , our FTIR and SFG results are in good agreement. Specifically in the case of the ethanol/Pt interface, the SFG spectroscopy presents higher sensibility to the interface response compared to the FTIR spectroscopy. (1 1 1); Pt(1 0 0); Pt(1 1 0); FTIR spectroscopy and SFG spectroscopy 0013-4686/$ -see front matter

The Angle Orthodontist, 2007

To evaluate in vitro the surface of elastomeric chains of different manufacturers to verify the p... more To evaluate in vitro the surface of elastomeric chains of different manufacturers to verify the presence of pathogenic microorganisms at the moment of unpacking and analyze a possible inhibitory effect of the elastomeric chain when exposed to microorganisms of the oral cavity, for example, Streptococcus mutans, Lactobacillus casei, and Candida albicans. Elastomeric chains from Ortho-Organizers Inc, 3M Unitek, and Dental Morelli were placed in petri plates with brain heart infusion agar medium and in sterile test tubes with brain heart infusion broth. The samples were incubated at 37 degrees C and analyzed at 24 hours, 48 hours, 3 days, and 7 days. In addition, elastomeric chains from the three manufacturers were placed in dishes, inoculated with microorganisms, incubated at 37 degrees C, and analyzed after 24 and 72 hours. No microorganism growth was detected after all incubation periods. No inhibition zones were identified surrounding the elastomeric chain. The results suggest that the fabrication of elastomeric chain is in accordance with biohazard concepts. However, careful manipulation is necessary to avoid colonization of pathogenic microorganisms since the composition of the elastomeric chains analyzed do not include antimicrobial agents.

Revista Brasileira de Fruticultura, 2009

Several fruits of native species of semi-arid region have great potential for commercialization, ... more Several fruits of native species of semi-arid region have great potential for commercialization, and among them there is the Spondias tuberosa. However, commercial cultivation of this species is limited by the difficulty of obtaining seedlings mainly depending on the dormancy of its seeds. Thus, the purpose of this study was to evaluate the seeds overcoming dormancy methods of Spondias Tuberosa to promote an increase in the rates of germination, uniformity and vigor of the seedlings. Two experiments were independently conducted. The treatments of the first experiments were: test, immersion of the seeds in water for 24 hours, immersion of the seeds in solution of gibberellic acid 1000 mg / L for 24 hours, scarification of seeds with sulfuric acid PA for 10 minutes and mechanical scarification of seeds. In the second experiment, the treatments consisted of planting the seeds with 0, 30, 60, 90, 120, 150, 180 and 210 days of storage in paper bags under laboratory conditions, at an average temperature of 22.5° C and relative humidity of 65%. In the first study it was found that there was a significant effect of the methods to seeds overcoming dormancy, concluding that the mechanical scarification is the best treatment, with an average germination rate in 60 days after planting 26.6%. In the second experiment, storage positively influenced the germination of seeds and seedlings vigor. The best results for uniformity and germination percentage (83%) were obtained between 120 and 210 days of seeds storage, while for the length and fresh weight of root, between 120 and 150 days.

We investigated the electrochemical oxidation of glycerol on low-index Pt single crystals in acid... more We investigated the electrochemical oxidation of glycerol on low-index Pt single crystals in acidic media (H 2 SO 4 and HClO 4 ) by cyclic voltammetry and Fourier Transform Infrared (FTIR) spectroscopy and we verified that this is a surface sensitive reaction. Pt(1 0 0) and Pt(1 1 0) surface structures favor the breaking of the C C C bond at low potentials (say 0.05 V), as seen by the formation of CO, one of the adsorbed residues of the glycerol dissociation, which poisons these surfaces even at high potentials. Pt(1 1 1) surface structure does not favor the C C C bond breaking at potentials as low as 0.05 V. However, Pt(1 1 1) is less poisoned by residues of glycerol dissociation and, for this reason, it is more active for glycerol oxidation than Pt(1 0 0) and Pt(1 1 0) at low potentials. Carbonyl containing compounds and CO 2 were detected as reaction products of the glycerol oxidation on all investigated single-crystal Pt surfaces. The ratio between CO 2 and carbonyl containing compounds is clearly much higher for Pt(1 0 0) and Pt(1 1 0) than for Pt(1 1 1).

Electrocatalysis, 2011

The electro-oxidation of glycerol on Au and Pt was studied in acid and alkaline media. The reacti... more The electro-oxidation of glycerol on Au and Pt was studied in acid and alkaline media. The reaction intermediates and products formed were determined by in situ Fourier transform infrared (FTIR) spectroscopy.

Electrocatalysis, 2012

In this paper we report a simple and environmentally friendly synthesis of silver nanoparticles (... more In this paper we report a simple and environmentally friendly synthesis of silver nanoparticles (AgNps) and their activities towards the oxygen reduction reaction (ORR). Ultraviolet spectroscopy (UV-vis) and transmission electron microscopy confirmed the formation of poly(vinyl pyrrolidone)-protected colloidal AgNps through direct reduction of Ag + by glycerol in alkaline medium at room temperature. For the ORR tests, the AgNps were directly produced onto carbon to yield the Ag/C catalyst. Levich plots revealed the process to occur via 2.7 electrons, suggesting that the carbon support contributes to the ORR. We discuss here possibilities of improving the catalytic properties of the Ag/C for ORR by optimizing the parameters of the synthesis.

Eclética Química, 2002

... Janaína Gomes; Osvaldo Antonio Serra; Ana Maria Pires ... 1 DANIELSON, E.; DEVENNEY, M.; GIAQ... more ... Janaína Gomes; Osvaldo Antonio Serra; Ana Maria Pires ... 1 DANIELSON, E.; DEVENNEY, M.; GIAQUINTA, D.; M.GOLDEN, JH; HAUSHALTER, R. C.; MCFARLAND, EW; POOJARY, DM; REAVES, CM; WEINBERG, WH; WU, X. D. X-ray powder structure of Sr2CeO4: a new ...

The Journal of Physical Chemistry B, 2006

Ethanol in an acidic solution-Pt(110) interface was studied by SFG spectroscopy (between 1820 and... more Ethanol in an acidic solution-Pt(110) interface was studied by SFG spectroscopy (between 1820 and 2325 cm -1 ) to explore primarily the effects of the alcohol concentration. Stretching bands of H-Pt (ca. 1970 or 2050 cm -1 ) and CO (ca. 1980 and 2040 cm -1 ) species, produced by the ethanol oxidation, were detected during the adsorption and oxidation of 0-1 mol L -1 ethanol in a 0.1 mol L -1 HClO 4 solution on the electrode surface. Hydrogen and CO coadsorb stably on Pt(110) between 0.05 and 0.15 V in ethanol-containing solutions. In this potential range, the blue shift of the hydrogen resonance (ca. 80 cm -1 ) reveals a weakening of the hydrogen bonding between adsorbed hydrogen and water molecules in the double layer. After the hydrogen desorption (0.15 V), the formation of compact CO islands, depending on the ethanol concentration, lifts the Pt(110) surface reconstruction. In ethanol-free solution, the surface remains reconstructed. The lower-frequency CO band is assigned to the CO species adsorbed on (1 × 2) reconstructed Pt(110) domains, having smaller local coverages, while the higher-frequency CO band is attributed to the close-packed CO species adsorbed on (1 × 1) patches. The reaction pathway forming CO 2 is less favored with increasing ethanol concentration.

Química Nova, 2004

Morphological and spectroscopic studies of Sr 2 CeO 4 blue phosphor in the form of fine particles... more Morphological and spectroscopic studies of Sr 2 CeO 4 blue phosphor in the form of fine particles prepared from a powdered multi-component precursor, via a combustion method, are reported. Samples were also prepared through a solid-state reaction and from a ...

Physical Chemistry Chemical Physics, 2013

Glycerol is at present abundantly co-produced in the biodiesel fabrication and can be used as fue... more Glycerol is at present abundantly co-produced in the biodiesel fabrication and can be used as fuel in Direct Glycerol Fuel Cells (DGFC) for cogeneration of electricity, value-added chemicals and heat. With this motivation, in the present work, we investigated at a fundamental level the oxidation of glycerol over glassy carbon (GC) supported Au nanoparticles in alkaline medium using cyclic voltammetry. By controlling the Au deposition time, we varied the GC supported Au coverage from 0.4% to 30% maintaining a regular particle size distribution with a mean particle size of about 200 nm. An influence of the carbon support on the activity of the GC-supported Au nanoparticles was evidenced. Results from studies on the oxidation of glycerol and ethylene glycol on Au and Pt nanoparticles supported on a glassy carbon, highly ordered pyrolytic graphite and dimensionally stable anode under different pH conditions indicate that the carbon support participates actively in the oxidation of glycerol and other alcohols. We propose that active oxygenated species are gradually formed on the glassy carbon by potential cycling (up to the saturation of the carbon area) and these oxygenated species are additional oxygen suppliers for the oxidation of glycerol residues adsorbed on the Au particles, following a mechanism consisting of the synergism of two active elements: gold and carbon.

Journal of Fluorescence, 2006

This work reports on the preparation of a luminescent blue-emitting rare earth (RE) Tm-doped oxid... more This work reports on the preparation of a luminescent blue-emitting rare earth (RE) Tm-doped oxide phosphor. Nanocrystalline RE2O3:Tm3+ particles were prepared via the combustion method using citric acid, glycine, or urea as fuels. Samples were doped with different percentages of the activator Tm3+. The post-annealing treatment was performed in air for all the samples, at temperatures ranging from 800 to 1100 degrees C, for 4 h. The samples were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL) and scanning electron and transmission microscopies (SEM and TEM) in order to determine the best synthetic procedure. The post-annealed powders showed blue emission with maximum at 452 nm characteristics for Tm3+ transition 1D2 --> 3H4 (under UV excitation at 360 nm). Samples, presented a tri-dimensional porous structure (50-200 nm) formed of spheroid particles with a diameter between 20 and 60 nm. The best luminescent material was obtained when urea was used to prepare nanoparticles of Gd2O3 doped with 0.5% Tm3+, and 1100 degrees C was used as the post-annealing temperature.

Journal of Electroanalytical Chemistry, 2011

In the present paper we investigated the electrochemical behavior of PVP on polycrystalline and s... more In the present paper we investigated the electrochemical behavior of PVP on polycrystalline and singlecrystal Pt electrodes. PVP hampered the characteristic hydrogen UPD and anion adsorption on all investigated surfaces. Several oxidation processes appeared in the anodic sweep with Pt(1 1 1) and Pt(1 0 0) being the most active for the oxidation processes. Repetitive cycling of the PVP ads -modified Pt(1 1 1) or Pt(1 0 0) electrodes in PVP-free aqueous H 2 SO 4 solution leads to a continuous suppression of the characteristic hydrogen UPD and anion adsorption as a consequence of PVP oxidation. However no PVP oxidation was observed when cycling the PVP ads -modified Pt(1 1 0) electrode in PVP-free aqueous H 2 SO 4 solution.

Electrochimica Acta, 2008

We have investigated the adsorbed intermediates of ethanol electro-oxidation at Pt(1 1 1), Pt(1 0... more We have investigated the adsorbed intermediates of ethanol electro-oxidation at Pt(1 1 1), Pt(1 0 0) and Pt(1 1 0) using FTIR and SFG spectroscopies. Mainly, we focus on the CO formation. The aim of the present work is to compare the responses coming from two different surface probes: FTIR spectroscopy and SFG spectroscopy. Between 1800 cm −1 and 2300 cm −1 , our FTIR and SFG results are in good agreement. Specifically in the case of the ethanol/Pt interface, the SFG spectroscopy presents higher sensibility to the interface response compared to the FTIR spectroscopy. (1 1 1); Pt(1 0 0); Pt(1 1 0); FTIR spectroscopy and SFG spectroscopy 0013-4686/$ -see front matter