RESUMO
Rapid, on-site detection of emerging pollutants is critical for monitoring health threats and the environment, especially if performed through autonomous systems. In this paper, we report on a new design of a complete electrochemical system whose working (WE), auxiliary (AE) and reference (RE) electrodes were obtained on a pen (PEN Sensor) made with graphite:polyurethane (GPUE). Working electrodes were decorated with spherical, ca. 200 nm silver nanoparticles (AgNPs) reduced on graphite using the polyol method. Differential pulse voltammetry (DPV) was used to detect bisphenol-A (BPA) in a linear range from 2.5 to 15 µmol L-1 with detection limit of 0.24 µmol L-1. The PEN Sensor could also detect bisphenol-A in tap and river water samples, with satisfactory reproducibility and repeatability, while common interferents did not affect electrooxidation of bisphenol-A. The high sensitivity and rapid detection are suitable for real-time analysis and in loco monitoring of emerging pollutants. With their robustness and versatility, PEN Sensors such as those fabricated here may be integrated into futuristic smart robotic systems.
Assuntos
Grafite , Nanopartículas Metálicas , Técnicas Eletroquímicas , Eletrodos , Limite de Detecção , Poliuretanos , Reprodutibilidade dos Testes , Rios , Prata , ÁguaRESUMO
The envisaged ubiquitous sensing and biosensing for varied applications has motivated materials development toward low cost, biocompatible platforms. In this paper, we demonstrate that carbon nanodiamonds (NDs) can be combined with potato starch (PS) and be deposited on a glassy carbon electrode (GCE) in the form of a homogeneous, rough film, with electroanalytical performance tuned by varying the relative ND-PS concentration. As a proof of concept, the ND/PS film served as matrix to immobilize tyrosinase (Tyr) and the resulting Tyr-ND-PS/GCE biosensor was suitable to detect catechol using differential pulse voltammetry with detection limit of 3.9â¯×â¯10-7â¯molâ¯L-1 in the range between 5.0â¯×â¯10-6 and 7.4â¯×â¯10-4â¯molâ¯L-1. Catechol could also be detected in river and tap water samples. This high sensitivity, competitive with biosensors made with more sophisticated procedures and materials in the literature, is attributed to the large surface area and conductivity imparted by the small NDs (<5â¯nm). In addition, the ND-PS matrix may have its use extended to immobilize other enzymes and biomolecules, thus representing a potential biocompatible platform for ubiquitous biosensing.
Assuntos
Técnicas Biossensoriais , Técnicas Eletroquímicas , Enzimas Imobilizadas/metabolismo , Monofenol Mono-Oxigenase/metabolismo , Nanodiamantes/química , Fenóis/análise , Solanum tuberosum/química , Amido/químicaRESUMO
A bare composite graphite-polyurethane electrode (EGPU) and two other modified with graphene (EGPU-GR) and functionalized multi-walled carbon nanotubes (EGPU-CNTs) were prepared and compared regarding their voltammetric response to escitalopran (EST). The modifiers were characterized by Raman spectroscopy and the resulting electrode materials by contact angle measurements with a hydrophilicity character in the ascending order for the composites: GPU > GPU-GR > GPU-CNTs and scanning electron microscopy (SEM). The electroactive areas of the EGPU, EGPU-GR, and EGPU-CNTs were 0.065, 0.080, and 0.092cm2, respectively, calculated from the chronocoulometry using K3[Fe(CN)6] as a probe and the Cottrell equation. The cyclic voltammograms obtained for EST indicated irreversible electrochemical behavior, with an anodic peak at ca. +0.80V (νs. SCE). These measurements were carried out with the three electrodes, and comparison of the analytical responses led to the EGPU-GR electrode being selected for use in the subsequent experiments. Under optimal conditions, square wave and differential pulse voltammetry at EGPU-GR presented linear dynamic ranges between 1.5 × 10-6 and 1.2 × 10-5mol L-1, with a detection limit of 2.5 × 10-7molL-1 (SWV) and 1.5 × 10-6 and 1.2 × 10-5molL-1, with a detection limit of 3.2 × 10-7molL-1 (DPV) for EST. The proposed method was applied for the quantification of EST in synthetic urine and cerebrospinal fluid samples, offering advantages including simplicity of fabrication, no requirement for analyte preconcentration and surface renewal, fast response, and selectivity.
Assuntos
Citalopram/análise , Eletroquímica/instrumentação , Grafite/química , Nanotubos de Carbono/química , Poliuretanos/química , Citalopram/líquido cefalorraquidiano , Citalopram/química , Citalopram/urina , Eletrodos , Limite de DetecçãoRESUMO
A new architecture for a biosensor is proposed using a glassy carbon electrode (GCE) modified with hemoglobin (Hb) and silver nanoparticles (AgNPs) encapsulated in poly(amidoamine) dendrimer (PAMAM). The biosensors were characterized using ultraviolet-visible spectroscopy, ζ-potential and cyclic voltammetry to investigate the interactions between Hb, AgNPs and the PAMAM film. The biosensor exhibited a well-defined cathodic peak attributed to reduction of the Fe(3+) present in the heme group in Hb, as revealed by cyclic voltammetry in the presence of O2. An apparent heterogeneous electron transfer rate of 4.1s(-1) was obtained. The Hb-AgNPs-PAMAM/GCE third generation biosensor was applied in the amperometric determination of hydrogen peroxide over the linear range from 6.0 × 10(-6) to 9.1 × 10(-5)mol L(-1) with a detection limit of 4.9 × 1 0(-6)mol L(-1). The proposed method can be extended to immobilize and evaluate the direct electron transfer of other redox enzymes.