This work describes the development of a platform based on bismuth oxyiodide (BiOI), sulfur-doped graphitic carbon nitride (S-g-C3N4), and bismuth-doped sodium tantalate perovskite (Bi-NaTaO3) for zero-biased photoelectrochemical immunosensing of cardiac troponin I (cTnI) biomarker. The spectroscopic, structural, morphological, and compositional characteristics of the photoelectrochemical (PEC) materials were evaluated by Raman and Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical impedance (EI) measurements were performed under the incidence and absence of light to investigate the effects of photons on the charge transfer resistance of the photoelectrochemical platform. The influence of the cTnI biomarker on the photoelectrochemical response of the anti-cTnI antibody-modified photoelectrochemical platform (anti-cTnI/BiOI/S-g-C3N/Bi-NaTaO3/FTO) was evaluated by measuring the photocurrent of the system. The immunosensor presented a linear response range from 1 pg mL 1 to 50 ng mL 1, mean recovery percentage between 95.98 and 99.78% in real human serum samples, and selectivity for the cTnI biomarker.

The present work is based on the development and application of a photoelectrochemical method for the amperometric determination of 3,4,5-trihydroxybenzoic acid in different samples. The method is based on the use of a photoelectrochemical platform based on a glass slide coated with fluorine-doped tin oxide, which has been modified with cadmium sulfide and poly(D-glucosamine) and subjected to a light-emitting diode (LED) lamp. The photoelectrochemical platform was sensitive to the increase of the concentration of the antioxidant 3,4,5-trihydroxybenzoic acid in the solution. Under the optimized experimental conditions, the photoelectrochemical method presented a linear response for a 3,4,5-trihydroxybenzoic acid concentration ranging from 0.2 up to 500 µmol L-1. The method was applied to 3,4,5-trihydroxybenzoic acid determination in samples of wines and teas with recoveries between 95.88 and 101.72%. The results obtained suggest that the developed platform is a promising tool for quantifying the 3,4,5-trihydroxybenzoic acid.

This work describes the development of a photoelectrochemical sensor for glucose quantification exploiting a light assisted-batch injection analysis (BIA) cell. A light-emitting diode (LED) lamp was employed to control the incidence of light on the p-Cu2O/n-Cu2O/fluorine-doped tin oxide (FTO) photoactive platform in BIA cell. The p-Cu2O/n-Cu2O/FTO platform was constructed by electrodepositing n-Cu2O and p-Cu2O and the characteristics of electrodeposited Cu2O films were investigated by X-ray diffraction (XRD), Raman spectroscopy, and electrochemical impedance spectroscopy. The light assisted-batch injection analysis of glucose based on the illuminated p-Cu2O/n-Cu2O/FTO photoelectrode presented a linear response of 10 μmol L-1-1 mmol L-1, a limit of detection of 4.0 μmol L-1, and sensitivity of 0.768 ± 0.011 μA L μmol-1 cm-2. The system presented an average recovery value of 96% when applied to the determination of glucose in an artificial saliva sample, which indicates that the incidence of light on photoelectroactive platforms is a promising approach for the determination and quantification of glucose.

In this study, a photoelectroanalytical sensor for determination of adrenaline based on deoxyribonucleic acid (DNA) and anatase titanium dioxide (TiO2) nanoparticles sensitized with bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) was developed, which we henceforward call BEDT-TTF/DNA/TiO2/ITO. The photoelectroanalytical sensor showed high photocurrent to adrenaline under visible light emitting diode (LED) light irradiation in comparison to each component of the composite material. Under optimized conditions, the BEDT-TTF/DNA/TiO2/ITO sensor shows a linear response range from 10 nmol L-1 up to 100 µmol L-1 with a sensitivity of 8.1 nA L µmol-1 and limit of detection of 1 nmol L-1 for the detection of adrenaline. The photoelectrochemical sensor showed high photocurrent to adrenaline in comparison to photocurrent response to ascorbic acid and uric acid. The BEDT-TTF/DNA/TiO2/ITO photoelectrochemical sensor was successfully applied to urine samples, with recovery values between 96 and 106%.

This work describes the electrochemical performance of a novel composite based on nickel tetrasulfonated phthalocyanine (NiTsPc), deoxyribonucleic acid from calf thymus (CT-DNA) and reduced graphene oxide (rGO) for the electroanalysis of reduced β-nicotinamide adenine dinucleotide (NADH), through electrocatalytic oxidation. The modified electrode was denoted as CT-DNA/NiTsPc/rGO. Fourier transform infrared and ultraviolet-visible spectroscopies were performed to characterize the composite material. The electrochemical performance of the composite for NADH oxidation was investigated by cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). The CT-DNA/NiTsPc/rGO modified glassy carbon electrode (GCE) showed an excellent electrocatalytic activity for NADH oxidation with apparent electrocatalytic rate constant (kobs) of 7.35 × 105 L mol-1 s-1 and linear response range for NADH from 1 up to 1350 µmol L-1 for n = 12 (r = 0.999). The proposed sensor shows sensitivity, detection limit and quantification limit of 0.014 µA L mol-1, 0.3 and 1 µmol L-1, respectively. The prepared sensor was further tested for the determination of NADH in artificial human urine samples, showing promising biomedical applications.

Descreve-se, no presente trabalho, o desenvolvimento de um sensor voltamétrico altamente sensível para a oncocalixona A, utilizando-se eletrodo de carbono vítreo modificado com uma bi-camada de ftalocianina tetrassulfonada de ferro(II) (FeTSPc) e tetra-(N-metil-4-piridil)-porfirina de ferro(III) (FeT4MPyP). O eletrodo modificado apresentou alta atividade catalítica e estabilidade em relação à redução da oncocalixona, proporcionando deslocamento anódico de ca. de 30 mV e amplificação da corrente de pico, em relação a iguais parâmetros obtidos em eletrodo de carbono vítreo não modificado. Um ampla faixa linear de resposta entre 0.005-1.2 µmol L-1, com sensibilidade de 8.11 µA L µmol-1 e limites de detecção (LOD) e quantificação (LOQ) de 1.5 e 5 nmol L-1 foram obtidos, com o uso desse sensor.

The development of a highly sensitive voltammetric sensor for oncocalyxone A using a glassy carbon electrode modified with a bilayer iron(II) tetrasulfonated phthalocyanine (FeTSPc) and iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) is described. The modified electrode showed high catalytic activity and stability for the oncocalyxone A reduction, provoking the anodic shift of the reduction peak potentials of ca. 30 mV and presenting much higher peak currents than those obtained on the bare GC electrode. A wide linear response range between 0.005-1.2 µmol L-1, with a sensitivity of 8.11 µA L µmol-1 and limits of detection (LOD) and quantification (LOQ) of 1.5 and 5 nmol L-1 were obtained with this sensor.