An electrochemical sensor for caffeine at a carbon nanofiber modified glassy carbon electrode

An electrochemical bio-electronic tongue based on borophene/PPy@ITO hybrid for selective caffeine identification

Caffeine is a natural stimulant found in various plants. Some individuals are particularly sensitive to caffeine and may experience adverse effects even with minimal intake. In order to address the potential health risks associated with high caffeine use, it is imperative to establish a precise, straightforward, efficient, and cost-efficient approach for measuring caffeine levels in regularly consumed items. This article explores electrochemical techniques for monitoring bitterness induced by caffeine. The fabricated bio-electronic tongue (Bio-ET) comprised a modified electrode made of borophene/PPy@ITO, created by electropolymerizing polypyrrole (PPy) onto indium tin oxide (ITO) and subsequently decorating it with borophene sheets. Cyclic voltammetry (CV) was used to investigate the electrochemical characteristics of caffeine on borophene/PPy@ITO. The findings revealed that the Bio-ET exhibited strong electro-oxidation and reduction activity towards caffeine, indicated by the presence of distinct redox peaks. The Bio-ET demonstrated a linear range from 0.5 to 700 μM with a limit of detection (LOD) of 0.177 μM. The Bio-ET electrode was successfully employed for caffeine quantification in real samples, including coffee, black tea, and regular tea, yielding excellent electrocatalytic performance. Furthermore, the potential of the Bio-ET system could lead to the development of portable, user-friendly devices for on-site analysis, facilitating rapid testing in various settings, such as beverages and pharmaceuticals, and presenting a promising direction for both research and commercial applications.

Direct Redox Sensing of Caffeine Utilizing Zinc-Doped Tin Oxide Nanoparticles as an Electrocatalyst

Objective: In addition to its positive benefits, caffeine also has harmful consequences. Therefore, it is essential to ascertain its content in various substances. Impact Statement: The present study emphasizes a novel way of quantification of caffeine in real as well as laboratory samples based on a nanomaterial-assisted electrochemical technique. Introduction: Electrochemical sensing is a prominent analytical technique because of its efficiency, speed, and simple preparation and observations. Due to its low chemical potential, SnO2 (tin oxide) demonstrates rapid redox reactions when used as an electrode. The presence of shielded 4f levels contributes to its distinctive optical, catalytic, and electrochemical capabilities. Methods: An efficient coprecipitation approach, which is simple and rapid and operates at low temperatures, is utilized to produce zinc-doped tin oxide nanoparticles (Zn-SnO2 nanoparticles). Zinc doping is used to modify the optoelectronic characteristics of tin oxide nanoparticles, rendering them very efficient as electrochemical sensors. Results: The crystal structure of samples was analyzed using x-ray diffraction, electronic transitions were calculated using ultraviolet-visible spectroscopy, and surface morphology was analyzed using field emission scanning electron microscopy. The x-ray diffraction investigation revealed that the produced Zn-doped SnO2 nanoparticles exhibit tetragonal phases, and the average size of their crystallites reduces upon doping Zn with SnO2. The bandgap energy calculated using the Tauc plot was found to be 3.77 eV. Conclusion: The fabricated caffeine sensor exhibits a sensitivity of 0.605 μA μM -1 cm-2, and its limit of detection was found to be 3 μM.

Optimizing the Construction and Activation of 3D-Printed Electrochemical Sensors: An Experimental Design Approach for Simultaneous Electroanalysis of Paracetamol and Caffeine

This work presents an optimization of the construction, treatment, and activation of 3D-printed electrochemical sensors (E-3D). For this, was used a 23-full factorial design examining three key variables at two levels: electrode height, electrode diameter, and printing speed. Moreover, it evaluates various physical, chemical, and electrochemical methods to treat and activate the E-3D surface. The techniques of electrochemical impedance spectroscopy and cyclic voltammetry (CV) shows that the sequential physical, chemical, and electrochemical treatments lead to the highest treatment efficiency and activation. Raman spectroscopy and atomic force microscopy characterize untreated and treated E-3D sensor surfaces. The optimal treatment and activation methodology was applied to the electroanalysis of paracetamol (PAR) and caffeine (CAF) simultaneously using CV and differential pulse anodic stripping voltammetry (DPASV). DPASV measurements reveal limits of detection of 0.44 and 0.58 μmol L-1 in a 0.5 mol L-1 H2SO4 medium for PAR and CAF, respectively, with the treated and activated E-3D sensor. The principal achievement of this work was emphasizing the critical role of surface treatment and activation in enhancing the performance of the developed electrodes, thereby advancing technological applications of 3D-printed electrochemical sensors.

A novel disposable ultrasensitive sensor based on nanosized ceria uniformly loaded carbon nanofiber nanoceramic film wrapped on pencil graphite rods for electrocatalytic monitoring of a tyrosine kinase inhibitor capmatinib

For the first time, we introduce a novel disposable and ultrasensitive sensing electrode made up of nanosized ceria uniformly loaded carbon nanofibers (CeNPs@CNF) sol-gel nanoceramic film (CF) wrapped on eco-friendly and inexpensive pencil graphite rods (PGRs) to explore their electro-catalytic detection of the anticancer drug capmatinib (CMB). The as-prepared CeNPs@CNF hybrid nanocomposite was described by XRD, SEM, TEM, HRTEM, and EDX analysis. The CV study clearly demonstrated that, the disposable CeNPs@CNF-CF/PGRE sensor exhibited excellent redox activities in the ideal probe [Fe(CN)6]3-/4-. Due to the outstanding electrochemical properties, larger electrochemically active surface area, and tremendous electro-catalytic activity of CeNPs@CNF, the reduction current of CMB on the CeNPs@CNF-CF/PGRE sensor is considerably higher than that of bare PGRE. The detection conditions, such as supporting electrolyte, pH of the buffer solution, amount of modifier, adsorption potential, and time, were studied and optimized. The sensing platform demonstrated high sensitivity (1.2 μA nM-1 cm-2), an ultralow detection limit (0.6 nM), and a wide linear range of 2.0 nM-400 nM of CMB compared to the bare PGRE. Additionally, the CeNPs@CNF-CF/PGRE sensor showed high selectivity, stability, and simple operation, which provided a promising alternative tool for fast detection of CMB in human body fluids with good recoveries.

Electrochemiluminescent determination of sphingomyelin in milk based on polyaniline hydrogel coupled with enzyme-functionalized Au nanoparticles

In this paper, sphingomyelin (SM) is detected by a polyaniline hydrogel and Au nanoparticles with enzyme modified electrode (GCE/PAniH/AuNPs@enzyme). After a battery of enzymic degradation, SM can generate H2O2 and enhance the electrochemiluminescence (ECL) response of luminol, which endows the sensor with good sensitivity, specifiity and repeatability. Additionally, the proposed ECL biosensor displays good analytical performances with a wide range from 10.0 μg·mL-1 to 250.0 μg·mL-1 as well as a low detection limit of 3.50 μg·mL-1 (S/N = 3). When the ECL biosensor is used in the detection of SM in milk samples, satisfactory results are obtained, indicating that PAniH/AuNPs@enzyme will serve as a promising ECL material in the applications of H2O2-related bioassay in the future.

Electrochemical Sensing Platform Based on Carbon Dots for the Simultaneous Determination of Theophylline and Caffeine in Tea

A simple and selective method for the determination of caffeine (CAF) and theophylline (THEO) has been developed for a glassy carbon electrode (GCE) modified with a composite including carbon dots (CDs) and chitosan (CS). To our knowledge, there are no previous studies that analyze a CDs-modified GCE for the presence of CAF and THEO. The electrochemical behavior of a GCE modified with a CDs-CS composite was studied in acidic medium by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Considering the sensor analytical parameters, the same linear concentrations range was found for CAF and THEO ranging from 1 × 10-5 to 5 × 10-3 mol L-1 with the same detection limit (LOD) of 1 × 10-6 mol L-1. The reproducibility and repeatability data were satisfactory in terms of RSD%. Moreover, the storage stability was evaluated, evidencing good results whatever the experimental conditions used. The developed sensor was applied for the simultaneous determination of CAF and THEO in tea and drug, and results were compared with those obtained with HPLC-ESI-MS in SIR mode as an independent method optimized on purpose. The electrochemical sensor presents the undoubled advantages in terms of cheapness, portability, and ease of use, since it does not require skilled personnel.

Design and fabrication of new anticancer sensor for monitoring of daunorubicin using 1-methyl-3-octylimidazolinium chloride and tin oxide/nitrogen-doped graphene quantum dot nanocomposite electrochemical sensor

In this study, a novel tin oxide/nitrogen-doped graphene quantum dot nanocomposite (SnO₂-NDGQD) and 1-methyl-3-octylimidazolinium chloride (1M3OICl) ionic liquid amplified carbon paste electrode (CPE) was fabricated as an efficient and fast-response sensor to determine daunorubicin, an anticancer drug. The electrochemical characteristics of daunorubicin at the surface of the 1M3OICl/SnO₂-NDGQD/CPE was explored via various voltammetric methods. The high-resolution transmission electron microscope (HR-TEM) images were recorded to examine the morphological structure of the as-synthesized nanocomposites. The 1M3OICl/SnO₂-NDGQD/CPE offered a wide linear concentration of 0.001-280.0 μM with a low detection limit of 0.40 nM at the optimized experimental conditions using square wave voltammetric (SWV) method. In a nutshell, the developed electrode illustrated outstanding selectivity in the presence of interfering agents and long-term stability. The1M3OICl/SnO₂-NDGQD/CPE was used as new and powerful analytical tool for determination of daunorubicin in real samples with recovery range 98.75%-104.8%.

Recent Advances in Electrochemical Sensors for Caffeine Determination

The determination of target analytes at very low concentrations is important for various fields such as the pharmaceutical industry, environmental protection, and the food industry. Caffeine, as a natural alkaloid, is widely consumed in various beverages and medicines. Apart from the beneficial effects for which it is used, caffeine also has negative effects, and for these reasons it is very important to determine its concentration in different mediums. Among numerous analytical techniques, electrochemical methods with appropriate sensors occupy a special place since they are efficient, fast, and entail relatively easy preparation and measurements. Electrochemical sensors based on carbon materials are very common in this type of research because they are cost-effective, have a wide potential range, and possess relative electrochemical inertness and electrocatalytic activity in various redox reactions. Additionally, these types of sensors could be modified to improve their analytical performances. The data available in the literature on the development and modification of electrochemical sensors for the determination of caffeine are summarized and discussed in this review.

Assessment of the Antioxidant Activity of Catechin in Nutraceuticals: Comparison between a Newly Developed Electrochemical Method and Spectrophotometric Methods

The analysis of antioxidants in different foodstuffs has become an active area of research, which has led to many recently developed antioxidant assays. Many antioxidants exhibit inherent electroactivity, and, therefore, the use of electrochemical methods could be a viable approach for evaluating the overall antioxidant activity of a matrix of nutraceuticals without the need for adding reactive species. Green tea is believed to be a healthy beverage due to a number of therapeutic benefits. Catechin, one of its constituents, is an important antioxidant and possesses free radical scavenging abilities. The present paper describes the electrochemical properties of three screen-printed electrodes (SPEs), the first one based on carbon nanotubes (CNTs), the second one based on gold nanoparticles (GNPs) and the third one based on carbon nanotubes and gold nanoparticles (CNTs-GNPs). All three electrodes were modified with the laccase (Lac) enzyme, using glutaraldehyde as a cross-linking agent between the amino groups on the laccase and aldehyde groups of the reticulation agent. As this enzyme is a thermostable catalyst, the performance of the biosensors has been greatly improved. Electro-oxidative properties of catechin were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), and these demonstrated that the association of CNTs with GNPs significantly improved the sensitivity and selectivity of the biosensor. The corresponding limit of detection (LOD) was estimated to be 5.6 × 10⁻⁸ M catechin at the CNT-Lac/SPE, 1.3 × 10⁻⁷ M at the GNP-Lac/SPE and 4.9 × 10⁻⁸ M at the CNT-GNP-Lac/SPE. The biosensors were subjected to nutraceutical formulations containing green tea in order to study their catechin content, using CNT-GNP-Lac/SPE, through DPV. Using a paired t-test, the catechin content estimated was in agreement with the manufacturer’s specification. In addition, the relationship between the CNT-GNP-Lac/SPE response at a specific potential and the antioxidant activity of nutraceuticals, as determined by conventional spectrophotometric methods (DPPH, galvinoxyl and ABTS), is discussed in the context of developing a fast biosensor for the relative antioxidant activity quantification.

Electrospinning-Based Carbon Nanofibers for Energy and Sensor Applications

Carbon nanofibers (CNFs) are the most basic structure of one-dimensional nanometer-scale sp2 carbon. The CNF’s structure provides fast current transfer and a large surface area and it is widely used as an energy storage material and as a sensor electrode material. Electrospinning is a well-known technology that enables the production of a large number of uniform nanofibers and it is the easiest way to mass-produce CNFs of a specific diameter. In this review article, we introduce an electrospinning method capable of manufacturing CNFs using a polymer precursor, thereafter, we present the technologies for manufacturing CNFs that have a porous and hollow structure by modifying existing electrospinning technology. This paper also discusses research on the applications of CNFs with various structures that have recently been developed for sensor electrode materials and energy storage materials.