8 research outputs found
Design and Fabrication of Flexible Copper Sensor Decorated with Bismuth Micro/Nanodentrites to Detect Lead and Cadmium in Noninvasive Samples of Sweat
The use of economic methods to design and fabricate flexible copper sensors decorated with bismuth micro/nanodentrites for the detection of lead and cadmium in sweat is demonstrated. The flexible copper sensors were constructed with simple and cost-effective materials; namely, flexible and adhesive conductive copper tape, adhesive label containing the design of a three-electrode electrochemical system, and nail polish or spray as a protective layer. The flexible copper device consisted of a working electrode decorated with bismuth micro/nanodentrites using an electrodeposition technique, a copper pseudo-reference and copper counter electrodes. Under optimal experimental conditions, the flexible sensing platform showed excellent performance toward the detection of lead and cadmium using differential pulse anodic stripping voltammetry (DPAdSV) in a wide linear range from 2.0 μM to 50 μM with acceptable reproducibility and repeatability, and limits of detection and quantification of 5.36 and 17.9 μM for Cd2+ ions and 0.76 μM and 2.5 for Pb2+ ions. Studies of addition and recovery in spiked artificial sweat sample were performed, with a recovery of 104.6%. The flexible copper device provides a great opportunity for application in wearable perspiration-based healthcare systems or portable sensors to detect toxic metals in biological samples
Use of manganese oxides recovered from spent batteries in electrocatalysis of oxygen reduction reaction in alkaline medium
The oxygen reduction reaction was studied in alkaline media using manganese oxides obtained from spent batteries as electrocatalysts. Three processes were used to recover manganese oxides from spent batteries. The particles obtained were in the range from 8 to 11 nm. The electrochemical experiments indicated a good electrocatalytic activity toward oxygen reduction using the different samples and showing approximately a direct transference of 4 electrons during the process. Even though all the processes were efficient, the best result was observed for the prepared sample using reactants of low cost.FAPESPCNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)UFAB
AFM studies and electrochemical characterization of boron-doped diamond surfaces modified with metal oxides by the Sol-Gel method
Continuing previous investigations, direct surface modifications of boron-doped diamond (BDD) electrodes with metal oxides (PtOx, RuO2, IrO2 and PbO2) and with some mixed composites were carried out by the Sol-Gel technique. The materials were studied by atomic force microscopy (AFM) to determine their surface topologies and by electrochemical techniques to establish the catalytic activity towards the oxygen evolution reaction (OER) and also, for the PtOx and PtOx-RuO2 composites, the ethanol oxidation reactions in acid media. The stability of PtOx coating covered by a Nafion® film was also tested by long-term operation. The AFM results indicated sites of heterogeneous deposition and the electrochemical studies demonstrated that the active surface area changed considerably with the proposed method of modification. The IrO2/BDD electrode showed the best performance to the OER with the onset of the oxidation current at ~1.4 V, a value 200 mV lower than for the PtOx/BDD electrode. The enhanced stability of PtOx/BDD electrodes achieved by the application of a Nafion® film and already reported in acid media was further proved using the ethanol oxidation reaction. Only a small loss of activity (6%) was observed after 4-hours electrolysis while one-thousand voltammetric cycles left the surface practically unchanged. In addition, preliminary studies for the same reaction on PtOx/BDD and PtOx-RuO2/BDD electrodes demonstrated the excellent activity of these mixed Sol-Gel coatings on the BDD surface and the possibility of further investigations for practical applications
Ethanol Oxidation Reaction on IrPtSn/C Electrocatalysts with low Pt Content
In this work, the ethanol oxidation reaction (EOR) was investigated using ternary nanostructured materials composed of IrPtSn/C in mass proportions of Ir:Pt:Sn at 60:30:10, 60:20:20 and 60:10:30, prepared with a polymeric precursor method and compared with commercial electrocatalyst PtSn/C E-TEK. X-ray diffractometry was used to obtain information about the structure of the material. The transmission electron microscopy showed particle sizes of 5-7 nm. The electrocatalytic activity was investigated using chronoamperometry experiments at 0.5 V vs. RHE and by in situ Fourier transform infrared spectroscopy by attenuated total reflectance (FTIR-ATR) experiments. From in situ FTIR-ATR experiments, it can be seen that using the best material IrPtSn/C 60:20:20, the acetaldehyde was produced at high intensities and CO2 at lower intensities. The use of IrPtSn/C 60:20:20 materials became possible to diminish the Pt fraction to ca. 73% in comparison to the PtSn/C E-TEK electrocatalyst, with an improvement of ca. 282% in the current density of the chronoamperometric experiments
Size Control of Carbon Spherical Shells for Sensitive Detection of Paracetamol in Sweat, Saliva, and Urine
We report on a facile strategy for
separating carbon spherical
shells (CSS) using centrifugation, with which shells were produced
with diameter varying from 400 to 500 nm according to scanning and
transmission electron microscopies. The shells were made of 79% carbon
and 21% oxygen, and their surface was functionalized with carbonyl
and hydroxyl groups. The CSS could form a homogeneous film on a glassy
carbon (GC) electrode surface and be used in a sensing platform. In
electroanalytical experiments, the sensitivity of the GC/CSS electrode
for paracetamol increased with decreasing size of CSS. For 400 nm
CSS, the sensitivity was 0.02 μA μmol<sup>–1</sup> L, and the limit of detection and quantification in sweat, saliva,
and urine samples was 120 and 400, 286 and 470, and 584 and 530 nmol
L<sup>–1</sup>, respectively, which represents the highest
performance among carbon-based sensors found in the literature. The
GC/CSS electrodes were stable, robust against typical interferents,
and allowed detection of paracetamol in sweat, saliva, and urine samples
with a performance indistinguishable from conventional high-performance
liquid chromatography