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In this work, nickel oxide nanoparticles‐modified multi‐walled carbon nanotubes (CNTs) were prepared and used for H2O2 sensing application. Firstly, ex situ NiO nanoparticles (NPs) were prepared and further used to decorate polyethylenimine (PEI)‐modified carboxylated CNTs. The obtained nanocomposite and its precursors were identified by using X‐ray diffraction, thermal analysis, Raman spectroscopy and SEM and TEM images, N2 adsorption‐desorption isotherms, and electrochemical techniques. The sensing properties of the NiO‐modified nanocomposite toward H2O2 were studied by electrochemical techniques using glassy carbon electrodes (GCEs) as support material. After optimizing the sensor construction, the sensor sensitivity was about of 0.83±0.01 A M−1 cm−2 with a LOD of about 1.0 μM. In addition, it showed excellent anti‐interference properties, reproducibility, and stability (over 4 months). Finally, such sensors were coupled to a flow injection device and the H2O2 concentration of some commercial antiseptic solutions were successfully obtained (with recovery ratios between 96.3–102.4 %).

The present work describes novel copper oxide thin film-modified indium tin oxide electrodes prepared by magnetron sputtering and their application for glucose sensing. Copper oxide-modified sensors were characterized by electrochemical techniques, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The deposited thin film (of about 400 nm of thickness) consisted of Cu2O/CuO nanocolumns of ca. 80 nm in diameter. After optimizing the main experimental parameters, the electrodes showed noteworthy electrocatalytic properties for glucose detection (sensitivity ca. 2.89 A M−1 cm−2 and limit of detection ca. 0.29 μM (S/N = 3)). The sensor showed negligible response against common electroactive species and other sugars. Finally, recovery experiments in commercial soda drinks and the determination of glucose content in different commercial drinks, such as soda, tea, fruit juices, and sports drinks, are described.

Biosensors are analytical devices that utilize biological interactions to detect and quantify clinical biomarkers, contaminants, allergens, and microorganisms. They combine different disciplines including analytical chemistry, molecular biology, and electrical engineering. Biosensors operate by coupling a bioreceptor, such as nucleic acid or proteins, with a transducer that converts the biological interaction into an electrical signal. Electrochemical and optical transduction are commonly used approaches due to their high detection capability and compatibility with miniaturization. Biosensors provide both high specificity and sensitivity and can be integrated into low-cost microfluidic platforms for rapid and point-of-care applications. These attributes make these devices valuable tools in analytical chemistry, particularly for early diagnostic applications. However, conventional biosensors face challenges related to the immobilization of biorecognition elements on the transducer surface, leading to issues like lost of sensitivity and selectivity. To address these problems, the introduction of nanomaterials, particularly magnetic nanoparticles (MNPs) and magnetic beads (MBs), has been implemented. MNPs combine their magnetic properties with other interesting characteristics such as small size, high surface-to-volume ratio, and excellent biocompatibility. They can be tailored for specific applications and have been extensively used in various fields, including biosensing and clinical diagnosis. Furthermore, MNPs simplify sample preparation by isolating target analytes through magnetic separation, thus improving sensitivity, and reducing analysis time and interference phenomena. The synthesis and modification of MNPs play a crucial role in adjusting their properties for different applications. This review presents an overview of the synthesis and surface modifications of magnetic nanoparticles, their role in the development of biosensors and bioassays, and their applications across various scientific areas.