Carbon black (CB) is a nanostructured material widely used in several industrial processes. This nanomaterial features a set of remarkable properties including high surface area, high thermal and electrical conductivity, and very low cost. Several studies have explored the applicability of CB in electrochemical fields. Recent data showed that modified electrodes based on CB present fast charge transfer and high electroactive surface area, comparable to carbon nanotubes and graphene. These characteristics make CB a promising candidate for the design of electrochemical sensors and biosensors. In this review, we highlight recent advances in the use of CB as a template for biosensing. As will be seen, we discuss the main biosensing strategies adopted for enzymatic catalysis for several target analytes, such as glucose, hydrogen peroxide, and environmental contaminants. Recent applications of CB on DNA-based biosensors are also described. Finally, future challenges and trends of CB use in bioanalytical chemistry are discussed.

Lipase B from Candida antarctica (CAL-B) is largely employed as a biocatalyst for hydrolysis, esterification, and transesterification reactions. CAL-B is a good model enzyme to study factors affecting the enzymatic structure, activity and/or stability after an immobilization process. In this study, we analyzed the immobilization of CAL-B enzyme on different magnetic nanoparticles, synthesized by the coprecipitation method inside inverse micelles made of zwitterionic surfactants, with distinct carbon chain length: 4 (ImS4), 10 (ImS10) and 18 (ImS18) carbons. Magnetic nanoparticles ImS4 and ImS10 were shown to cross-link to CAL-B enzyme via a Michael-type addition, whereas particles with ImS18 were bond via pyridine formation after glutaraldehyde cross-coupling. Interestingly, the Michael-type cross-linking generated less stable immobilized CAL-B, revealing the influence of a cross-linking mode on the resulting biocatalyst behavior. Curiously, a direct correlation between nanoparticle agglomerate sizes and CAL-B enzyme reuse stability was observed. Moreover, free CAL-B enzyme was not able to catalyze transesterification due to the high methanol concentration; however, the immobilized CAL-B enzyme reached yields from 79.7 to 90% at the same conditions. In addition, the transesterification of lipids isolated from oleaginous yeasts achieved 89% yield, which confirmed the potential of immobilized CAL-B enzyme in microbial production of biodiesel.

The simultaneous electrochemical detection of mood disorder related substances, such as amitriptyline, melatonin and tryptophan, was successfully achieved by using a novel nano-magnetic electrochemical sensor design, encompassing Fe₃O₄ nanoparticles decorated with carbon quantum dots (MagNPs/Cdots). The magnetic composite was characterized using HR-TEM microscopy, XRD and Raman spectroscopy, and was applied onto a glassy carbon electrode using a miniature neodymium magnet. The determination of amitriptyline, melatonin and tryptophan was performed by monitoring oxidation promoted by MagNPs/Cdots in BR-buffer at pH 3.0, which proceeded according to well-defined differential pulse voltammetry peaks, with detection limits of 5.9, 4.4 and 4.2 nmol L⁻¹, respectively. No significant interference was seen from biological interferents such as uric acid, ascorbic acid, dopamine, estriol and 17β-estradiol. The magnetic hybrid material was highly stable in solution, opening exciting opportunities for the development of low cost and practical electrochemical sensors for the determination of mood disorder related substances in real clinical samples.

The present work reports the degradation of 4-nitrophenol using BiVO₄/CuO hybrid material synthesized by the precipitation of BiVO₄ in the presence of CuO. Morphological and structural characterizations were performed using X-ray diffraction and scanning electronic microscopy coupled to energy dispersive X-ray spectroscopy. Through the calculation of the Kubelka–Munk function applied to diffuse reflectance spectrophotometry data, the hybrid material presented absorption edge of 1.85 eV. The formation of p-n heterojunction between BiVO₄ and CuO renders the hybrid material suitable for the construction of a photoanode employed in hydroxyl radical generation. UV–vis spectrophotometry and high-performance liquid chromatography experiments were performed in order to monitor the degradation of 4-nitrophenol and the formation of secondary products. Additional information regarding the hybrid material was obtained through ion chromatography and total organic carbon analyses. The application of BiVO₄/CuO-based photocatalyzer led to a 50.2% decrease in total organic carbon after the degradation of 4-nitrophenol. Based on the results obtained in the study, BiVO₄/CuO has proved to be a promising material suitable for the removal of recalcitrant compounds in water treatment plants.

The present study reports the synthesis and characterization of hydrophobic deep eutectic solvents (HDES) based on fatty acids and tetrabutylammonium bromide (TBAB) or 1-octanol using Fourier transform infrared spectroscopy, and the analysis of the physicochemical properties (viscosity, density, electrical conductivity, and water content) of these solvents. A carbon paste electrode modified with 6.0% (m/m) decanoic acid and TBAB-based HDES was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The oxidation peak currents of the proposed electrode were enhanced by its high electrochemical activity, fast electron transfer rate, and high surface area, while a remarkable decrease was observed in the peak potential separation. The electrochemical determination of hydroquinone (H₂Q) was carried out using square-wave adsorptive anodic stripping voltammetry (SWAdASV). The electrode response was found to be linear in the H₂Q concentration range of 2.5 × 10⁻⁶–3.0 × 10⁻³ mol L⁻¹, with the limit of detection (LOD) of 7.7 × 10⁻⁷ mol L⁻¹. The method was successfully applied for H₂Q determination in dermatological creams.