We report the electrochemical detection of estriol using carbon black nanoballs (CNB) decorated with silver nanoparticles (AgNP) as electrode material. Homogeneous, porous films on glassy carbon electrodes (GCE) were obtained, with diameters of 20 - 25nm for CNB and 5 - 6nm for AgNP. CNB/AgNP electrodes had increased conductivity and electroactive area in comparison with bare GCE and GCE/CNB, according to cyclic voltammetry and electrochemical impedance spectroscopy. The oxidation potential peak was also down shifted by 93mV, compared to the bare GC electrode. Differential pulse voltammetry data were obtained in 0.1molL PBS (pH 7.0) to detect estriol without the purification step, in the linear range between 0.2 and 3.0µmolL with detection and quantification limits of 0.16 and 0.5µmolL (0.04 and 0.16mgL), respectively. The sensor was used to detect estriol in a creek water sample with the same performance as in the official methodology based on high performance liquid chromatography.

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–1 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–1, 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.

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