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    A novel, extreme simple modification of low-cost pencil graphite electrode (PGE) by single-walled carbon nanotube/pyrenebutyric acid (SWCNT/PBA) nanostructure for sensitive and selective detection of adrenaline
    (Springer, 2025) Mahmoudi, Ghodrat; Hosseinifard, Mojtaba; Moghadam, Ahmad Jamali; Gargari, Masoumeh Servati; Alizadeh, Vali
    The electrochemical carbon nanotube (CNT)-based sensors may provide an effective answer to the growing need for qualitative and quantitative determination of biomolecules. However employing CNTs as interface nanomaterials in various electrode matrices has been challenging for researchers. The most important issues are uniform dispersion of CNTs due to their agglomeration and their interfacial connection with electrode matrices. The superiority of this work lies in its ability to overcome these shortcomings by simple and rapid procedures while remaining negligible sensor surface fouling, but also provides high sensitive, inexpensive, and selective determination of AD molecule. Our work presents the non-covalent functionalization of Single Wall Carbon Nanotubes (SWCNTs) by Pyrenebutyric Acid (PBA) through simple pi-stacking interaction for preserving their electronic structure and preventing their agglomeration in the dispersion step to develop a novel disposable sensor with many attractive analytical performance characteristics for Adrenaline (AD) determination. SWCNTs/PBA hybrid film on a low-cost PGE support have been developed involving soaking of greatly simplified solvent-treated GPE without any further pretreatment step into successfully dispersed SWCNTs/PBA in ethanol, which is a green solvent. The surface morphology of the SWCNTs/PBA nanostructured films were evaluated using Field-emission scanning electron microscopy (FE-SEM), being correlated with the electrochemical characteristics observed by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. The heterogeneous electron transfer rate constant (ks) values 0.09, 0.15 and 0.40 s-1 were obtained for Bare PGE, PGE/SWCNT, and PGE/SWCNT/PBA electrodes, respectively. The obtained ks values have been shown that modification of SWCNTs with PBA improves the analytical properties of the sensor more than those obtained at bare PGE and SWCNTs/PGE due to synergistic effects. The analytical performance of SWCNTs/PBA/PGE was evaluated for AD oxidation in optimum pH 7.0 of phosphate buffer solution in the presence of an excess amount of interfering compounds by DPV technique. The fabricated sensor showed good response with high sensitivity, low detection limit (40 nM), wide linear range (0.25-9 mu M), and excellent reproducibility and repeatability. Also, the simultaneous analyses of AD and Uric Acid (UA) reveal that the fabricated sensor could separate the electrooxidation peaks of these two mixtures and good response with low detection limit (95nM) was also obtained for UA detection. The practical applicability of the fabricated sensor has been successfully tested for the determination of AD in human serum and injection ampoule samples with 98-110% recoveries.
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    Modification of flame etched carbon-fiber microelectrode (FE-CFME) by single walled carbon nanotube/pyreneacetic acid (SWCNT/PAA) nanocomposite for sensitive and selective detection of dopamine
    (Elsevier B.V., 2025) Alizadeh, Vali; Mahmoudi, Ghodrat; Hosseinifard, Mojtaba; Jamali Moghadam, Ahmad; Servati Gargari, Masoumeh
    An inexpensive, simple and fast methode of sensor construction as well as negligible sensor surface fouling, along with the high sensitivity and selectivity has always been a challenge in the fabrication of electrochemical sensors. In this study, to achieve this goal, carbon fiber microelectrode (CFME) was pretreated by applying fast flame etching and then simply modifed by pyrene acetic acid (PAA) decorated single walled carbon nanotube (SWCNT) nanocomposite for highly sensitive and selective dopamine (DA) detection. The results show that, although the CFME became active upon flame etching due to introduces nanometer-scale roughness features on it, surface modification by SWCNT-PAA further increases its sensitivity due to synergistic effects. Attaching PAA onto SWCNTs can effectively inhibit the π-stacking of the SWCNTs to prevent their agglomeration and offer a large surface area of electrode, as well as enhancing the diffusion of positively charged DA by its anionic carboxylate moieties. This is the first report on applying PAA/SWCNT nanocomposite for surface modification of flame etched carbon fiber microelectrode (FE-CFME). The surface morphology of the Bare-CFME, FE-CFME, and FE-CFME/SWCNT-PAA electrodes were evaluated using Field-emission scanning electron microscopy (FE-SEM), being correlated with the electrochemical characteristics observed by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. As expected, the fabricated sensor showed improved electrochemical response with high sensitivity and selectivity. Under optimum conditions, this sensor exhibited high performance toward DA determination with good linearity in a broad linear range of 0.5 to 22 μM with the detection limit of 12.9 nM, and excellent reproducibility and repeatability. The practical applicability of the fabricated sensor has been successfully tested for the determination of DA in human serum and injection ampoule samples with recovery rates ranging from 98 % to 105 % and relative standard deviations below 3.1 %. © 2025 Elsevier B.V.