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Papers by LUIZA MARIA FERREIRA DANTAS
International Journal of Electrochemical Science
In this work, we present an investigation on the thickness of the eroded enamel layer in tooth sa... more In this work, we present an investigation on the thickness of the eroded enamel layer in tooth samples after exposure to citric and hydrochloric acid by using Scanning Electrochemical Microscopy (SECM). Approaching curves with typical negative feedback behavior were obtained in enamel samples for evaluation of topographic changes. In a control experiment, SECM images showed no significant difference in the current monitored during the scan, implying that enamel demineralization did not occur in mineral water medium. Topographic SECM images obtained after contact with citric and hydrochloric acid for different periods of time showed a significant increase in the current relative to a previously protected surface, indicating the structural loss of enamel. The thickness of the enamel layer eroded after contact with hydrochloric acid was significantly higher when compared to the one obtained with citric acid. Hence, our results showed that the enamel acid erosion is a relatively fast process, which is strongly dependent on parameters such as pH, time, acid strength and acid concentration.
Monatshefte für Chemie - Chemical Monthly
In this paper, a composite based on chitosan and cobalt phthalocyanine immobilized onto a glassy ... more In this paper, a composite based on chitosan and cobalt phthalocyanine immobilized onto a glassy carbon electrode is presented for the sensitive determination of sulfanilamide in pharmaceutical and urine samples. The modification performed on the electrode surface, by the deposition of this composite, exhibits an irreversible anodic peak at 0.97 V vs. Ag/AgCl, KClsat in phosphate buffer at pH 7.00 for sulfanilamide. Results show that peak potential is influenced linearly by the pH of the supporting electrolyte, exhibiting a slope of 0.054 V/pH. Using differential pulse voltammetry, detection of sulfanilamide was possible in a linear range from 1.00 to 53.00 μmol dm−3 with a detection limit and quantification limit of 0.27 and 0.91 μmol dm−3, respectively. Importantly, the sensor showed practical applications as an analytical tool for the quantification of sulfanilamide in pharmaceutical formulations and urine samples. The electrochemical approach detailed here has been validated to drug samples using a spectrophotometric method. The method proposed presents good linearity, low quantification and detection limits being of excellent applicability in pharmaceutical and urine samples.
Journal of Electroanalytical Chemistry
Journal of Materials Science
Controlling the sensitivity, quantification, and detection limits of electrochemical sensors is a... more Controlling the sensitivity, quantification, and detection limits of electrochemical sensors is an ongoing challenge. The properties of thin modified gold-film electrodes under varying potentials have been studied to improve such analytical validation parameters; however, most international literature on the subject tends to analyze the role of synthesis lonely without deep evaluating surface properties throughout every step of a modification process. Herein, we aimed to link materials science with sensing analytical application, revisiting a nanoporous gold-film electrochemical synthesis, and explain its performance using SEM, AFM, and XPS analyses. Also, we used the neglected emerging contaminant 2,6-dichloro-1,4-benzoquinone (DCBQ) for our analytical issues assessment. We were able to show the electrocatalytic effect of the prepared electrode, commonly mistreated in such field; also, we evaluated the sensor's modification for a possible explanation for the system's reproducibility (10 times without loss of activity, RSD inferior to 5%). Although the modification time presented an effect on the nanoporous electrode response, we could confirm that it was not an area augmentation effect only based on the electrochemical characterizations. We believe we took a step forward to understand the effect of the electrochemical modification performed, which can be carried out in other systems, helping a more rational design of sensors. Graphical abstract
Microchemical Journal, 2021
Measurement, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Journal of Electroanalytical Chemistry, 2016
A novel bio-electrochemical immunosensor for sensitive and selective detection of anti-peptide an... more A novel bio-electrochemical immunosensor for sensitive and selective detection of anti-peptide antibodies of HPV was fabricated by immobilization of a peptide (SPINNTKPHEAR) (1) linked to a 6-aminohexanoic (Ahx) residue and ferrocene (Fc) on a gold electrode surface, used as sensing interface. The Fc-Ahx-peptide (Fc-Ahx-SPINNTKPHEAR) (1AFc) was obtained by solid phase peptide synthesis by using the Fmoc/tBu strategy. Peptides were purified by preparative HPLC, characterized by MS, MALDI-TOF, and Circular Dichroism and their purity was evaluated by using analytical HPLC. The electrochemical behavior of the modified electrode was examined by cyclic voltammetry in phosphate buffer solution (PBS) in order to evaluate the redox behavior of the ferrocene moiety. The influence of anti-peptide antibodies on the voltammetric response of the modified electrode was investigated by comparing results obtained with pre-immune (control) and post immune serum samples at similar dilution factor. Changes in such behavior upon addition of the serum samples to PBS suggested that the fabricated bioelectrochemical sensor was able to recognize the interaction between anti-peptide antibodies and the immobilized peptide (1AFc) with high selectivity and sensitivity. Such influence increased as the dilution decreased, but the effect was less pronounced at relatively high concentrated solutions owing to the effect of the sample matrix. Notwithstanding, the proposed biosensor can clearly detect the target anti-peptide antibodies at a significant large concentration range.
Sensors and Actuators B: Chemical, 2014
This work describes the fabrication and application of a disposable copper random microarray (DCR... more This work describes the fabrication and application of a disposable copper random microarray (DCRM) of electrodes. The DCRM was fabricated by deposition of two toner pattern masks on a copper substrate. In the first step, the mask layers were drawn using a graphical software and then printed on waxed papers. The first toner mask delimited the disc area (2 mm diameter) and the second toner mask (with 90% of black toner) defined the irregular distribution of the generated microelectrodes. The toner masks were heat-transferred to the copper substrate (with a diameter of 10 mm and a width of 25 mm) for 600 s in a thermal press heated at 120 • C. The proposed electrochemical sensor was applied for the amperometric determination of two analytes: hydrogen peroxide in real samples (oral antiseptic and dental whitening) at −0.2 V in phosphate buffer (pH 7.0) solution and acetylsalicylic acid (ASA) in pharmaceutical formulations at 0.6 V in 0.10 mol L −1 NaOH solution. The good results obtained with the DCRM demonstrated the successful application of this new sensor. The main advantages of the proposed manufacturing procedure are the simplicity, low cost of equipment and the high speed of production of microelectrode arrays on different substrates.
European Journal of Inorganic Chemistry, 2014
This paper describes the development of a facile and environmentally friendly strategy for suppor... more This paper describes the development of a facile and environmentally friendly strategy for supporting palladium nanoparticles (Pd NPs) on multiwalled carbon nanotubes (MWCNTs) with ethanol as the solvent/reducing agent, potassium tetrachloropalladate(II) (K 2 PdCl 4) as the Pd precursor, and polyvinylpyrrolidone (PVP) as the surface modifier. More specifically, our approach was based on the nonbonding interaction between MWCNTs and PVP, which is a cheap, nontoxic, and commercial polymer. As PVP can serve not only as a surface modifier but also as a stabilizing agent for Pd NPs, the utilization of additional functionalization steps, reducing agents, and stabilizers was not required to achieve uniform Pd deposition over the MWCNTs. Our results demonstrate that Pd NPs below 5 nm in diameter can
Journal of Solid State Electrochemistry, 2020
Rapid methods using batch injection analysis (BIA) with amperometric detection were developed for... more Rapid methods using batch injection analysis (BIA) with amperometric detection were developed for the determination of quercetin extracted from the Brazilian plants Brunfelsia uniflora (BU), Vismia guianensis (VG), and Arrabidaea brachypoda (AB). One method was based on a glassy carbon electrode (GCE) and pulsed amperometry (BIA-PA), while the other employed a screen-printed carbon electrode (SPCE) and conventional amperometry (BIA-CA). Both proposed methods required minimal sample manipulation (only dilution in the carrier electrolyte), and the determination was performed with a single injection of 100 μL of sample solution. The BIA-PA method was highly accurate ( RSD = 0.7%, n = 30), fast (120 injections h −1 ), and presented low limits of detection (0.004 μmol L −1 ) and quantification (0.015 μmol L −1 ). The BIA-CA method was also accurate ( RSD = 1.1%, n = 30), fast (120 injections h −1 ), and presented low limits of detection (0.027 μmol L −1 ) and quantification (0.091 μmol L −1 ). The application of the proposed methods for the determination of quercetin in the plant extracts provided results similar to those obtained by high-performance liquid chromatography (HPLC) at a confidence level of 95%.
International Journal of Electrochemical Science
In this work, we present an investigation on the thickness of the eroded enamel layer in tooth sa... more In this work, we present an investigation on the thickness of the eroded enamel layer in tooth samples after exposure to citric and hydrochloric acid by using Scanning Electrochemical Microscopy (SECM). Approaching curves with typical negative feedback behavior were obtained in enamel samples for evaluation of topographic changes. In a control experiment, SECM images showed no significant difference in the current monitored during the scan, implying that enamel demineralization did not occur in mineral water medium. Topographic SECM images obtained after contact with citric and hydrochloric acid for different periods of time showed a significant increase in the current relative to a previously protected surface, indicating the structural loss of enamel. The thickness of the enamel layer eroded after contact with hydrochloric acid was significantly higher when compared to the one obtained with citric acid. Hence, our results showed that the enamel acid erosion is a relatively fast process, which is strongly dependent on parameters such as pH, time, acid strength and acid concentration.
Monatshefte für Chemie - Chemical Monthly
In this paper, a composite based on chitosan and cobalt phthalocyanine immobilized onto a glassy ... more In this paper, a composite based on chitosan and cobalt phthalocyanine immobilized onto a glassy carbon electrode is presented for the sensitive determination of sulfanilamide in pharmaceutical and urine samples. The modification performed on the electrode surface, by the deposition of this composite, exhibits an irreversible anodic peak at 0.97 V vs. Ag/AgCl, KClsat in phosphate buffer at pH 7.00 for sulfanilamide. Results show that peak potential is influenced linearly by the pH of the supporting electrolyte, exhibiting a slope of 0.054 V/pH. Using differential pulse voltammetry, detection of sulfanilamide was possible in a linear range from 1.00 to 53.00 μmol dm−3 with a detection limit and quantification limit of 0.27 and 0.91 μmol dm−3, respectively. Importantly, the sensor showed practical applications as an analytical tool for the quantification of sulfanilamide in pharmaceutical formulations and urine samples. The electrochemical approach detailed here has been validated to drug samples using a spectrophotometric method. The method proposed presents good linearity, low quantification and detection limits being of excellent applicability in pharmaceutical and urine samples.
Journal of Electroanalytical Chemistry
Journal of Materials Science
Controlling the sensitivity, quantification, and detection limits of electrochemical sensors is a... more Controlling the sensitivity, quantification, and detection limits of electrochemical sensors is an ongoing challenge. The properties of thin modified gold-film electrodes under varying potentials have been studied to improve such analytical validation parameters; however, most international literature on the subject tends to analyze the role of synthesis lonely without deep evaluating surface properties throughout every step of a modification process. Herein, we aimed to link materials science with sensing analytical application, revisiting a nanoporous gold-film electrochemical synthesis, and explain its performance using SEM, AFM, and XPS analyses. Also, we used the neglected emerging contaminant 2,6-dichloro-1,4-benzoquinone (DCBQ) for our analytical issues assessment. We were able to show the electrocatalytic effect of the prepared electrode, commonly mistreated in such field; also, we evaluated the sensor's modification for a possible explanation for the system's reproducibility (10 times without loss of activity, RSD inferior to 5%). Although the modification time presented an effect on the nanoporous electrode response, we could confirm that it was not an area augmentation effect only based on the electrochemical characterizations. We believe we took a step forward to understand the effect of the electrochemical modification performed, which can be carried out in other systems, helping a more rational design of sensors. Graphical abstract
Microchemical Journal, 2021
Measurement, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Journal of Electroanalytical Chemistry, 2016
A novel bio-electrochemical immunosensor for sensitive and selective detection of anti-peptide an... more A novel bio-electrochemical immunosensor for sensitive and selective detection of anti-peptide antibodies of HPV was fabricated by immobilization of a peptide (SPINNTKPHEAR) (1) linked to a 6-aminohexanoic (Ahx) residue and ferrocene (Fc) on a gold electrode surface, used as sensing interface. The Fc-Ahx-peptide (Fc-Ahx-SPINNTKPHEAR) (1AFc) was obtained by solid phase peptide synthesis by using the Fmoc/tBu strategy. Peptides were purified by preparative HPLC, characterized by MS, MALDI-TOF, and Circular Dichroism and their purity was evaluated by using analytical HPLC. The electrochemical behavior of the modified electrode was examined by cyclic voltammetry in phosphate buffer solution (PBS) in order to evaluate the redox behavior of the ferrocene moiety. The influence of anti-peptide antibodies on the voltammetric response of the modified electrode was investigated by comparing results obtained with pre-immune (control) and post immune serum samples at similar dilution factor. Changes in such behavior upon addition of the serum samples to PBS suggested that the fabricated bioelectrochemical sensor was able to recognize the interaction between anti-peptide antibodies and the immobilized peptide (1AFc) with high selectivity and sensitivity. Such influence increased as the dilution decreased, but the effect was less pronounced at relatively high concentrated solutions owing to the effect of the sample matrix. Notwithstanding, the proposed biosensor can clearly detect the target anti-peptide antibodies at a significant large concentration range.
Sensors and Actuators B: Chemical, 2014
This work describes the fabrication and application of a disposable copper random microarray (DCR... more This work describes the fabrication and application of a disposable copper random microarray (DCRM) of electrodes. The DCRM was fabricated by deposition of two toner pattern masks on a copper substrate. In the first step, the mask layers were drawn using a graphical software and then printed on waxed papers. The first toner mask delimited the disc area (2 mm diameter) and the second toner mask (with 90% of black toner) defined the irregular distribution of the generated microelectrodes. The toner masks were heat-transferred to the copper substrate (with a diameter of 10 mm and a width of 25 mm) for 600 s in a thermal press heated at 120 • C. The proposed electrochemical sensor was applied for the amperometric determination of two analytes: hydrogen peroxide in real samples (oral antiseptic and dental whitening) at −0.2 V in phosphate buffer (pH 7.0) solution and acetylsalicylic acid (ASA) in pharmaceutical formulations at 0.6 V in 0.10 mol L −1 NaOH solution. The good results obtained with the DCRM demonstrated the successful application of this new sensor. The main advantages of the proposed manufacturing procedure are the simplicity, low cost of equipment and the high speed of production of microelectrode arrays on different substrates.
European Journal of Inorganic Chemistry, 2014
This paper describes the development of a facile and environmentally friendly strategy for suppor... more This paper describes the development of a facile and environmentally friendly strategy for supporting palladium nanoparticles (Pd NPs) on multiwalled carbon nanotubes (MWCNTs) with ethanol as the solvent/reducing agent, potassium tetrachloropalladate(II) (K 2 PdCl 4) as the Pd precursor, and polyvinylpyrrolidone (PVP) as the surface modifier. More specifically, our approach was based on the nonbonding interaction between MWCNTs and PVP, which is a cheap, nontoxic, and commercial polymer. As PVP can serve not only as a surface modifier but also as a stabilizing agent for Pd NPs, the utilization of additional functionalization steps, reducing agents, and stabilizers was not required to achieve uniform Pd deposition over the MWCNTs. Our results demonstrate that Pd NPs below 5 nm in diameter can
Journal of Solid State Electrochemistry, 2020
Rapid methods using batch injection analysis (BIA) with amperometric detection were developed for... more Rapid methods using batch injection analysis (BIA) with amperometric detection were developed for the determination of quercetin extracted from the Brazilian plants Brunfelsia uniflora (BU), Vismia guianensis (VG), and Arrabidaea brachypoda (AB). One method was based on a glassy carbon electrode (GCE) and pulsed amperometry (BIA-PA), while the other employed a screen-printed carbon electrode (SPCE) and conventional amperometry (BIA-CA). Both proposed methods required minimal sample manipulation (only dilution in the carrier electrolyte), and the determination was performed with a single injection of 100 μL of sample solution. The BIA-PA method was highly accurate ( RSD = 0.7%, n = 30), fast (120 injections h −1 ), and presented low limits of detection (0.004 μmol L −1 ) and quantification (0.015 μmol L −1 ). The BIA-CA method was also accurate ( RSD = 1.1%, n = 30), fast (120 injections h −1 ), and presented low limits of detection (0.027 μmol L −1 ) and quantification (0.091 μmol L −1 ). The application of the proposed methods for the determination of quercetin in the plant extracts provided results similar to those obtained by high-performance liquid chromatography (HPLC) at a confidence level of 95%.