Koiti Araki | Universidade de São Paulo (original) (raw)
Papers by Koiti Araki
Analytica Chimica Acta, 2002
The modification of a glassy carbon surface by coating with an electrostatically assembled film o... more The modification of a glassy carbon surface by coating with an electrostatically assembled film of tetraruthenated cobalt porphyrin/(meso-tetra(4-sulphonatephenyl)porphyrinate zinc(II) yields an indicator electrode that allows the determination of nitrite to be performed with a limit of detection of 0.1 M in a flow injection configuration. The dynamic range extends up to 1000 M and the repeatability of the measurements was evaluated to be 1.5% with a throughput of 50 samples per hour. The efficiency of the bilayered film to mediate the electron transfer allows the determinations to be performed at a less positive potential (+0.75 V) with enhanced sensitivity. The coating also prevents the surface poisoning and its stability is maintained over several weeks. The same detector was used for determination of nitrate after reduction to nitrite in a reductor column containing copperised cadmium. This method was used for the determination of nitrate and nitrite in mineral water, saliva and cured meats, the results being in agreement with certified values and those obtained by using recommended procedures.
International Journal of Pharmaceutics, 2009
ChemElectroChem, Jun 8, 2021
The possibility of fast, reliable, and sensitive (μmol L À 1) quantification of acetaminophen (AA... more The possibility of fast, reliable, and sensitive (μmol L À 1) quantification of acetaminophen (AAP) directly in saliva and sweat was demonstrated in the pH range of 4 to 7 using a new userfriendly and cost-effective graphite screen-printed electrode (SPE) modified with 2-3 nm diameter alpha-nickel-cerium hydroxide nanoparticles. The nanoparticles (NPs) were fully characterized by transmission electron microscopy (TEM, HRTEM and STEM), XRD, and the electrochemical conditions for AAP analysis optimized, pushing down the limit of detection with good selectivity. The possibility of real-time measurements of AAP was demonstrated by carrying out experiments directly in biofluids, without significant interference from species such as lactate, glucose, ascorbic and uric acid usually present in this kind of samples. This is the first report combining the catalytic properties and easy incorporation of alpha-nickel-cerium hydroxide nanoparticles into graphite ink to prepare an SPE for AAP electrochemical detection in secreting body fluids. The α-Ni 0.9 Ce 0.1 (OH) 2 SPE features good accuracy and selectivity, fast response, good accuracy and selectivity, as well as low reagent consumption for determination of AAP in real saliva and sweat samples.
Analytica Chimica Acta, 2002
The modification of a glassy carbon surface by coating with an electrostatically assembled film o... more The modification of a glassy carbon surface by coating with an electrostatically assembled film of tetraruthenated cobalt porphyrin/(meso-tetra(4-sulphonatephenyl)porphyrinate zinc(II) yields an indicator electrode that allows the determination of nitrite to be performed with a limit of detection of 0.1 M in a flow injection configuration. The dynamic range extends up to 1000 M and the repeatability of the measurements was evaluated to be 1.5% with a throughput of 50 samples per hour. The efficiency of the bilayered film to mediate the electron transfer allows the determinations to be performed at a less positive potential (+0.75 V) with enhanced sensitivity. The coating also prevents the surface poisoning and its stability is maintained over several weeks. The same detector was used for determination of nitrate after reduction to nitrite in a reductor column containing copperised cadmium. This method was used for the determination of nitrate and nitrite in mineral water, saliva and cured meats, the results being in agreement with certified values and those obtained by using recommended procedures.
International journal of nanomedicine, 2017
Metastatic melanoma is an aggressive cancer with increasing incidence and limited therapies in ad... more Metastatic melanoma is an aggressive cancer with increasing incidence and limited therapies in advanced stages. Systemic neutrophilia or abundant neutrophils in the tumor contribute toward its worst prognosis, and the interplay of cancer and the immune system has been shown in tumor development and metastasis. We recently showed the in vivo efficacy of poly(ε-caprolactone) lipid-core nanocapsule (LNC) or LNC loaded with acetyleugenol (AcE-LNC) to treat B16F10-induced melanoma in mice. In this study, we investigated whether LNC or AcE-LNC toxicity could involve modifications on crosstalk of melanoma cells and neutrophils. Therefore, melanoma cells (B16F10) were pretreated with vehicle, LNC, AcE or AcE-LNC for 24 h, washed and, further, cocultured for 18 h with peritoneal neutrophils obtained from C57Bl/6 mice. Melanoma cells were able to internalize the LNC or AcE-LNC after 2 h of incubation. LNC or AcE-LNC pretreatments did not cause melanoma cells death, but led melanoma cells to b...
Journal of Electroanalytical Chemistry, 1991
Progress in Inorganic Chemistry, Vol 56, 2009
... 5. Exploring the Supramolecular Coordination Chemistry-Based Approach for Nanotechnology. Ken... more ... 5. Exploring the Supramolecular Coordination Chemistry-Based Approach for Nanotechnology. Kenneth D. Karlin. Henrique E. Toma,; Koiti Araki. ... Author Information. Instituto de Quimica, Universidade de São Paulo CEP 05513-970 São Paulo, Brazil. Publication History. ...
Spectroscopy Letters, 1998
Abstract Tetra (3-pyridyl) porphyrazine is soluble in trifluoroethanol yielding intense blue solu... more Abstract Tetra (3-pyridyl) porphyrazine is soluble in trifluoroethanol yielding intense blue solutions. The electronic spectra exhibit the characteristic Soret and Q bands around 330 and 610 nm, respectively; however, the absorption profile is strongly dependent on the ...
Organic & Biomolecular Chemistry, 2012
Langmuir, 1996
... In the case of a rodlike nematic mesogenic porphyrin phase, Bard and co-workers reported that... more ... In the case of a rodlike nematic mesogenic porphyrin phase, Bard and co-workers reported that the value increases to about 4 Å. ... Fan, FF; Bard, AJ J. Am. Chem. Soc. 1980, 102, 5138. [ACS Full Text ACS Full Text ]. (3) Kampas, FJ; Yamashita, K.; Fajer, J. Nature 1980, 284, 40. ...
Journal of Applied Polymer Science, 2012
The relative amounts of amorphous and crystalline cand a-phases in polyamide-6 nanocomposites, es... more The relative amounts of amorphous and crystalline cand a-phases in polyamide-6 nanocomposites, estimated from the deconvolution of X-ray diffraction peaks using Gaussian functions, correlates with their mechanical, thermomechanical, and barrier properties. The incorporation of organoclay platelets (Cloisite 15A and 30B) induced the crystallization of the polymer in the c form at expense of the amorphous phase, such that 1-2 wt % of Cloisite is enough to enhance the mechanical and the thermomechanical properties. However, higher nanofiller loads were necessary to achieve good barrier effects, because this property is mainly dependent on the tortuous path permeation mechanism of the gas molecules through the nanocomposite films. V
Inorganica Chimica Acta, 2013
ABSTRACT The light-to-electricity conversion efficiencies of the new (Bu4N)3[Ru(dcbpy)2(tmtH2)], ... more ABSTRACT The light-to-electricity conversion efficiencies of the new (Bu4N)3[Ru(dcbpy)2(tmtH2)], (Bu4N)4[Ru(dcbpy)2(tmtH)] and (Bu4N)5[Ru(dcbpy)2(tmt)] complexes, where dcbpy = 2,2′-bipyridyl-4,4′-dicarboxylate and tmt = 2,4,6-trimercapto-1,3,5-triazine, were comparable with those obtained with the N719 dye. Furthermore, the contribution of two MLCT and a LMCT charge-transfer band to the energy conversion process was revealed by deconvolution of the photoaction spectra, indicating that they are the first ruthenium dyes presenting long distance photo-injection from a ligand-to-metal charge-transfer excited state.
Electrochimica Acta, 2009
In the present work we describe the investigation of interfacial and superficial processes on tet... more In the present work we describe the investigation of interfacial and superficial processes on tetraruthenated zinc porphyrin (ZnTRP) films immobilized on gold electrode surface. In situ and real time measurements employing electrochemical surface plasmon resonance (ESPR) and electrochemical quartz crystal microbalance (EQCM) have given new insights into the electrochemical oxidation of ferrocyanide and phenolic compounds (acetaminophen, dopamine, and catechol) on ZnTRP modified electrodes. The decrease of diode like behavior in the presence of such phenolic species in contrast with ferrocyanide was clearly assigned to the inclusion of those species in the porphyrin film, creating new conduction pathways connecting the gold electrode surface with the film/solution interface. In fact, there are evidences that they can intercalate in the film (catechol > dopamine > acetaminophen), whereas ferrocyanide is completely excluded. Accordingly, the molecular size may play a fundamental role in such a process.
Analytical Chemistry, 2010
Traditional Feigl&amp... more Traditional Feigl's spot tests can be greatly improved with the aid of gold nanoparticles and Raman probes, by monitoring the changes in the surface enhanced Raman scattering (SERS) of the analytes directly applied on a filter paper previously impregnated with the selective organic reagent. As a proof of concept, diphenylthiocarbazone (dithizone) was treated with citrate stabilized gold nanoparticles and employed in paper spot tests for a variety of transition and heavy metal ions. Below 10(-5) mol L(-1), only mercury(II) ions were able to displace the dithizone molecules from the "coordination shell" of the gold nanoparticles, leading to a systematic decay of the Raman signals. Because of the huge enhancement of the dithizone vibrational peaks, the SERS spot tests allowed the detection of picograms of Hg(2+) ions.
![Research paper thumbnail of Spectroelectrochemical and kinetic behaviour of the [Ru(edta)-(diethyldithiocarbamate)] complex](https://attachments.academia-assets.com/75207954/thumbnails/1.jpg)
](Transition Metal Chemistry, 1992
The [Ru(edta)(ddtc)]2− complex, where ddtc− represents a bidentate diethyldithiocarbamate ligand,... more The [Ru(edta)(ddtc)]2− complex, where ddtc− represents a bidentate diethyldithiocarbamate ligand, has been characterized in one solid state and in solution. Reversible electrochemical and spectroelectrochemical behavour has been observed for the complex, with E0(RuIII/RuII) = −0.22V versus S.H.E. A formation mechanism starting from [RuIII(edta)(H2O)]− and ddtc− is proposed, involying a monodendate binding step, with kf = 17 M−1 s−1, followed by rapid ring closure.
ABSTRACT In this paper, a new composite sensor for e-nose application is described. A modificatio... more ABSTRACT In this paper, a new composite sensor for e-nose application is described. A modification in the regular pair conductive polymer/Lewis acid dopant is proposed, replacing the acid by free-base or metallated porphyrins. Sensors doped with different porphyrin species, using the same conductive polymer, led to a huge variation in response to selected analytes. Two different arrays (doped with free-base and metallated porphyrins) using these sensors were able to identify four organic solvents, used as standard analytes: propanone, ethyl acetate, ethanol and toluene. Both of them could distinguish the tested vapours.
Journal of coordination chemistry, 1991
... Clieni. SOC. Japan, 55, 797 (1982). HE Toma, PS Santos, MPD Mattioli and LA Oliveira, Polyhed... more ... Clieni. SOC. Japan, 55, 797 (1982). HE Toma, PS Santos, MPD Mattioli and LA Oliveira, Polyhedron. 6, 603 (1987). AA Diamantis and JV Dubrawski, Iriorg. ClIenz.. 20, 1142 (1981). MM Taqui Khan, A. Hussain, G. Ramachandraiah and MA hloiz, Inorg. Cheni.. 25,3023 (1986). ...
Nanoscale, 2010
Magnetic AFM probes known as MAClevers® were employed for sensing picogram amounts of magnetic na... more Magnetic AFM probes known as MAClevers® were employed for sensing picogram amounts of magnetic nanoparticles, based on the cantilever frequency shifts resulting from the magnetically induced adsorption of mass. By using organothiol functionalized magnetic nanoparticles, this analytical strategy was successfully extended to the detection of gold nanoparticles, as confirmed by confocal Raman microscopy.
Inorganic Chemistry, 2004
Modification of wide band gap semiconductor surfaces by a new generation of supramolecular sensit... more Modification of wide band gap semiconductor surfaces by a new generation of supramolecular sensitizers combining porphyrin and ruthenium−polypyridyl complexes leads to versatile molecular interfaces, allowing the exploitation of photoinduced charge transfer in photoelectrochemical devices.
Analytica Chimica Acta, 2002
The modification of a glassy carbon surface by coating with an electrostatically assembled film o... more The modification of a glassy carbon surface by coating with an electrostatically assembled film of tetraruthenated cobalt porphyrin/(meso-tetra(4-sulphonatephenyl)porphyrinate zinc(II) yields an indicator electrode that allows the determination of nitrite to be performed with a limit of detection of 0.1 M in a flow injection configuration. The dynamic range extends up to 1000 M and the repeatability of the measurements was evaluated to be 1.5% with a throughput of 50 samples per hour. The efficiency of the bilayered film to mediate the electron transfer allows the determinations to be performed at a less positive potential (+0.75 V) with enhanced sensitivity. The coating also prevents the surface poisoning and its stability is maintained over several weeks. The same detector was used for determination of nitrate after reduction to nitrite in a reductor column containing copperised cadmium. This method was used for the determination of nitrate and nitrite in mineral water, saliva and cured meats, the results being in agreement with certified values and those obtained by using recommended procedures.
International Journal of Pharmaceutics, 2009
ChemElectroChem, Jun 8, 2021
The possibility of fast, reliable, and sensitive (μmol L À 1) quantification of acetaminophen (AA... more The possibility of fast, reliable, and sensitive (μmol L À 1) quantification of acetaminophen (AAP) directly in saliva and sweat was demonstrated in the pH range of 4 to 7 using a new userfriendly and cost-effective graphite screen-printed electrode (SPE) modified with 2-3 nm diameter alpha-nickel-cerium hydroxide nanoparticles. The nanoparticles (NPs) were fully characterized by transmission electron microscopy (TEM, HRTEM and STEM), XRD, and the electrochemical conditions for AAP analysis optimized, pushing down the limit of detection with good selectivity. The possibility of real-time measurements of AAP was demonstrated by carrying out experiments directly in biofluids, without significant interference from species such as lactate, glucose, ascorbic and uric acid usually present in this kind of samples. This is the first report combining the catalytic properties and easy incorporation of alpha-nickel-cerium hydroxide nanoparticles into graphite ink to prepare an SPE for AAP electrochemical detection in secreting body fluids. The α-Ni 0.9 Ce 0.1 (OH) 2 SPE features good accuracy and selectivity, fast response, good accuracy and selectivity, as well as low reagent consumption for determination of AAP in real saliva and sweat samples.
Analytica Chimica Acta, 2002
The modification of a glassy carbon surface by coating with an electrostatically assembled film o... more The modification of a glassy carbon surface by coating with an electrostatically assembled film of tetraruthenated cobalt porphyrin/(meso-tetra(4-sulphonatephenyl)porphyrinate zinc(II) yields an indicator electrode that allows the determination of nitrite to be performed with a limit of detection of 0.1 M in a flow injection configuration. The dynamic range extends up to 1000 M and the repeatability of the measurements was evaluated to be 1.5% with a throughput of 50 samples per hour. The efficiency of the bilayered film to mediate the electron transfer allows the determinations to be performed at a less positive potential (+0.75 V) with enhanced sensitivity. The coating also prevents the surface poisoning and its stability is maintained over several weeks. The same detector was used for determination of nitrate after reduction to nitrite in a reductor column containing copperised cadmium. This method was used for the determination of nitrate and nitrite in mineral water, saliva and cured meats, the results being in agreement with certified values and those obtained by using recommended procedures.
International journal of nanomedicine, 2017
Metastatic melanoma is an aggressive cancer with increasing incidence and limited therapies in ad... more Metastatic melanoma is an aggressive cancer with increasing incidence and limited therapies in advanced stages. Systemic neutrophilia or abundant neutrophils in the tumor contribute toward its worst prognosis, and the interplay of cancer and the immune system has been shown in tumor development and metastasis. We recently showed the in vivo efficacy of poly(ε-caprolactone) lipid-core nanocapsule (LNC) or LNC loaded with acetyleugenol (AcE-LNC) to treat B16F10-induced melanoma in mice. In this study, we investigated whether LNC or AcE-LNC toxicity could involve modifications on crosstalk of melanoma cells and neutrophils. Therefore, melanoma cells (B16F10) were pretreated with vehicle, LNC, AcE or AcE-LNC for 24 h, washed and, further, cocultured for 18 h with peritoneal neutrophils obtained from C57Bl/6 mice. Melanoma cells were able to internalize the LNC or AcE-LNC after 2 h of incubation. LNC or AcE-LNC pretreatments did not cause melanoma cells death, but led melanoma cells to b...
Journal of Electroanalytical Chemistry, 1991
Progress in Inorganic Chemistry, Vol 56, 2009
... 5. Exploring the Supramolecular Coordination Chemistry-Based Approach for Nanotechnology. Ken... more ... 5. Exploring the Supramolecular Coordination Chemistry-Based Approach for Nanotechnology. Kenneth D. Karlin. Henrique E. Toma,; Koiti Araki. ... Author Information. Instituto de Quimica, Universidade de São Paulo CEP 05513-970 São Paulo, Brazil. Publication History. ...
Spectroscopy Letters, 1998
Abstract Tetra (3-pyridyl) porphyrazine is soluble in trifluoroethanol yielding intense blue solu... more Abstract Tetra (3-pyridyl) porphyrazine is soluble in trifluoroethanol yielding intense blue solutions. The electronic spectra exhibit the characteristic Soret and Q bands around 330 and 610 nm, respectively; however, the absorption profile is strongly dependent on the ...
Organic & Biomolecular Chemistry, 2012
Langmuir, 1996
... In the case of a rodlike nematic mesogenic porphyrin phase, Bard and co-workers reported that... more ... In the case of a rodlike nematic mesogenic porphyrin phase, Bard and co-workers reported that the value increases to about 4 Å. ... Fan, FF; Bard, AJ J. Am. Chem. Soc. 1980, 102, 5138. [ACS Full Text ACS Full Text ]. (3) Kampas, FJ; Yamashita, K.; Fajer, J. Nature 1980, 284, 40. ...
Journal of Applied Polymer Science, 2012
The relative amounts of amorphous and crystalline cand a-phases in polyamide-6 nanocomposites, es... more The relative amounts of amorphous and crystalline cand a-phases in polyamide-6 nanocomposites, estimated from the deconvolution of X-ray diffraction peaks using Gaussian functions, correlates with their mechanical, thermomechanical, and barrier properties. The incorporation of organoclay platelets (Cloisite 15A and 30B) induced the crystallization of the polymer in the c form at expense of the amorphous phase, such that 1-2 wt % of Cloisite is enough to enhance the mechanical and the thermomechanical properties. However, higher nanofiller loads were necessary to achieve good barrier effects, because this property is mainly dependent on the tortuous path permeation mechanism of the gas molecules through the nanocomposite films. V
Inorganica Chimica Acta, 2013
ABSTRACT The light-to-electricity conversion efficiencies of the new (Bu4N)3[Ru(dcbpy)2(tmtH2)], ... more ABSTRACT The light-to-electricity conversion efficiencies of the new (Bu4N)3[Ru(dcbpy)2(tmtH2)], (Bu4N)4[Ru(dcbpy)2(tmtH)] and (Bu4N)5[Ru(dcbpy)2(tmt)] complexes, where dcbpy = 2,2′-bipyridyl-4,4′-dicarboxylate and tmt = 2,4,6-trimercapto-1,3,5-triazine, were comparable with those obtained with the N719 dye. Furthermore, the contribution of two MLCT and a LMCT charge-transfer band to the energy conversion process was revealed by deconvolution of the photoaction spectra, indicating that they are the first ruthenium dyes presenting long distance photo-injection from a ligand-to-metal charge-transfer excited state.
Electrochimica Acta, 2009
In the present work we describe the investigation of interfacial and superficial processes on tet... more In the present work we describe the investigation of interfacial and superficial processes on tetraruthenated zinc porphyrin (ZnTRP) films immobilized on gold electrode surface. In situ and real time measurements employing electrochemical surface plasmon resonance (ESPR) and electrochemical quartz crystal microbalance (EQCM) have given new insights into the electrochemical oxidation of ferrocyanide and phenolic compounds (acetaminophen, dopamine, and catechol) on ZnTRP modified electrodes. The decrease of diode like behavior in the presence of such phenolic species in contrast with ferrocyanide was clearly assigned to the inclusion of those species in the porphyrin film, creating new conduction pathways connecting the gold electrode surface with the film/solution interface. In fact, there are evidences that they can intercalate in the film (catechol > dopamine > acetaminophen), whereas ferrocyanide is completely excluded. Accordingly, the molecular size may play a fundamental role in such a process.
Analytical Chemistry, 2010
Traditional Feigl&amp... more Traditional Feigl's spot tests can be greatly improved with the aid of gold nanoparticles and Raman probes, by monitoring the changes in the surface enhanced Raman scattering (SERS) of the analytes directly applied on a filter paper previously impregnated with the selective organic reagent. As a proof of concept, diphenylthiocarbazone (dithizone) was treated with citrate stabilized gold nanoparticles and employed in paper spot tests for a variety of transition and heavy metal ions. Below 10(-5) mol L(-1), only mercury(II) ions were able to displace the dithizone molecules from the "coordination shell" of the gold nanoparticles, leading to a systematic decay of the Raman signals. Because of the huge enhancement of the dithizone vibrational peaks, the SERS spot tests allowed the detection of picograms of Hg(2+) ions.
Transition Metal Chemistry, 1992
The [Ru(edta)(ddtc)]2− complex, where ddtc− represents a bidentate diethyldithiocarbamate ligand,... more The [Ru(edta)(ddtc)]2− complex, where ddtc− represents a bidentate diethyldithiocarbamate ligand, has been characterized in one solid state and in solution. Reversible electrochemical and spectroelectrochemical behavour has been observed for the complex, with E0(RuIII/RuII) = −0.22V versus S.H.E. A formation mechanism starting from [RuIII(edta)(H2O)]− and ddtc− is proposed, involying a monodendate binding step, with kf = 17 M−1 s−1, followed by rapid ring closure.
ABSTRACT In this paper, a new composite sensor for e-nose application is described. A modificatio... more ABSTRACT In this paper, a new composite sensor for e-nose application is described. A modification in the regular pair conductive polymer/Lewis acid dopant is proposed, replacing the acid by free-base or metallated porphyrins. Sensors doped with different porphyrin species, using the same conductive polymer, led to a huge variation in response to selected analytes. Two different arrays (doped with free-base and metallated porphyrins) using these sensors were able to identify four organic solvents, used as standard analytes: propanone, ethyl acetate, ethanol and toluene. Both of them could distinguish the tested vapours.
Journal of coordination chemistry, 1991
... Clieni. SOC. Japan, 55, 797 (1982). HE Toma, PS Santos, MPD Mattioli and LA Oliveira, Polyhed... more ... Clieni. SOC. Japan, 55, 797 (1982). HE Toma, PS Santos, MPD Mattioli and LA Oliveira, Polyhedron. 6, 603 (1987). AA Diamantis and JV Dubrawski, Iriorg. ClIenz.. 20, 1142 (1981). MM Taqui Khan, A. Hussain, G. Ramachandraiah and MA hloiz, Inorg. Cheni.. 25,3023 (1986). ...
Nanoscale, 2010
Magnetic AFM probes known as MAClevers® were employed for sensing picogram amounts of magnetic na... more Magnetic AFM probes known as MAClevers® were employed for sensing picogram amounts of magnetic nanoparticles, based on the cantilever frequency shifts resulting from the magnetically induced adsorption of mass. By using organothiol functionalized magnetic nanoparticles, this analytical strategy was successfully extended to the detection of gold nanoparticles, as confirmed by confocal Raman microscopy.
Inorganic Chemistry, 2004
Modification of wide band gap semiconductor surfaces by a new generation of supramolecular sensit... more Modification of wide band gap semiconductor surfaces by a new generation of supramolecular sensitizers combining porphyrin and ruthenium−polypyridyl complexes leads to versatile molecular interfaces, allowing the exploitation of photoinduced charge transfer in photoelectrochemical devices.