Francisco Contini Barreto

Carbon-based nanomaterials, particularly multi-walled carbon nanotubes (MWCNTs), are widely used in electrochemical sensors due to their high conductivity and large surface area. However, their poor dispersion often requires synthetic surfactants. Biopolymers such as cellulose have emerged as promising sustainable dispersing agents. In this context, bacterial nanocellulose (BNC) produced from waste offers a green alternative with potential to stabilize and disperse MWCNTs in aqueous media. Herein, a surfactant-free nanocomposite based on BNC produced from beer waste and MWCNTs modified with silver nanoparticles (AgNPs) was engineered to modify electrochemical sensors for pharmaceutical detection of furosemide. The morphology, composition, and electrochemical properties of the nanocomposite were characterized by scanning electron microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV). Furosemide oxidation was evaluated in aqueous medium and synthetic urine using a glassy carbon electrode modified with the MWCNTs/BNC-AgNPs film, and voltammetric parameters were optimized to enhance the analytical response. The sensor presented a linear range from 5.0 to 65.0 µmol L⁻¹, with limits of detection and quantification of 0.19 and 0.64 µmol L⁻¹, respectively. These findings demonstrate the high sensitivity and practical applicability of the MWCNTs/BNC-AgNPs-modified electrode for reliable furosemide determination in urine samples.

The global prevalence of counterfeit and low-quality pharmaceuticals poses significant health risks and challenges in medical treatments, creating a need for rapid and reliable drug screening technologies. This study introduces a cost-effective electrochemical paper-based device (ePAD) modified with functionalized bamboo-derived biochar (BCF) for the detection of paracetamol in substandard medicines. The sensor was fabricated using a custom 3D-printed stencil in PLA, designed for efficient production, and a 60:40 (m/m) graphite (GR) and glass varnish (GV) conductive ink, resulting in a robust and sensitive platform. The electroactive area of the ePAD/BCF sensor was determined as 0.37 cm². Characterization via SEM and cyclic voltammetry (CV) verified its structural and electrochemical stability. The sensor demonstrated linear detection of paracetamol from 5.0 to 60.0 µmol L⁻¹ with a detection limit of 3.50 µmol L⁻¹. Interference studies showed high selectivity, with recoveries of over 90%, and the sensor successfully quantified paracetamol in commercial analgesic and anti-flu samples. This sustainable, bamboo-based ePAD offers a promising solution for rapid on-site pharmaceutical quality control, with significant potential to enhance drug screening accuracy.

Escitalopram (ESC) is commonly prescribed as an antidepressant to enhance serotonin levels in the brain, effectively addressing conditions such as depression and anxiety. The COVID-19 pandemic, along with ongoing mental health crises, has exacerbated the prevalence of these disorders, largely due to factors such as social isolation, fear of the virus, and financial difficulties. This study presents the enhancement of a glassy carbon electrode (GC) through the incorporation of hydrochar (HDC) derived from spent coffee grounds and copper nanoparticles (CuNPs) for the detection of ESC in synthetic urine. Characterization of the nanocomposite was conducted using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and cyclic voltammetry (CV). The analytical parameters were systematically optimized, and a sensing platform was utilized for the quantification of ESC via square-wave voltammetry (SWV). The established linear range was found to be between 1.0 µmol L⁻¹ and 50.0 µmol L⁻¹, with a limit of detection (LOD) of 0.23 µmol L⁻¹. Finally, an electrochemical sensor was employed to measure ESC levels in synthetic urine, yielding recovery rates ranging from 91.7% to 94.3%. Consequently, the HDC-CuNPs composite emerged as a promising, sustainable, and cost-effective alternative for electroanalytical applications.

This research describes the modification of a glassy carbon electrode with spent coffee grounds hydrochar (HDC) and copper nanoparticles (CuNPs) for the simultaneous determination of hydroxychloroquine sulfate (HCS) and bisphenol A (BPA). Scanning electron microscopy, EDS and cyclic voltammetry were used to characterize the nanocomposite. The analytical parameters were optimized and the sensing platform was applied for the determination of HCS and BPA using square-wave voltammetry (SWV). For HCS, the linear range was from 1.0 μmol L⁻¹ to 50 μmol L⁻¹, with an LOD and LOQ of 0.46 and 1.53 μmol L⁻¹, respectively. For BPA, the linear range was from 0.5 μmol L⁻¹ to 10 μmol L⁻¹, with an LOD and LOQ of 0.31 μmol L⁻¹ and 1.06 μmol L⁻¹, respectively. Finally, the developed electrochemical sensor was applied for the quantification of the emerging contaminants in natural water, with recoveries between 94.8% and 106.8% for HCS and 99.6% and 105.2% for BPA. Therefore, HDC-CuNPs demonstrated themselves to be a good alternative as a sustainable and cheaper material for application in electroanalyses.

The rising popularity of herbal medicine as a weight loss remedy, fueled by misleading propaganda, raises concerns about the manufacturing processes and potential inclusion of controlled substances such as fluoxetine (FLU). The objective of this work is to develop and evaluate the performance of an electrochemical device by modifying a glassy carbon electrode (GC) with a nanocomposite based on reduced graphene oxide (rGO) and copper nanoparticles (CuNPs) for detecting FLU in manipulated herbal medicines. Scanning electron microscopy (FEG-SEM) and cyclic voltammetry (CV) were applied for morphological and electrochemical characterization and analysis of the composite’s electrochemical behavior. Under optimized conditions, the proposed sensor successfully detected FLU within the range of 0.6 to 1.6 µmol L⁻¹, showing a limit of detection (LOD) of 0.14 µmol L⁻¹. To determine the presence of FLU in herbal samples, known amounts of the analytical standard were added to the sample, and the analyses were performed using the standard addition method, yielding recoveries between −2.13 and 2.0%.

This study describes the use of copper nanoparticles (CuNPs) and reduced graphene oxide (rGO) as an electrode modifier for the determination of chloroquine phosphate (CQP). The synthetized rGO-CuNPs composite was morphologically characterized using scanning electron microscopy and electrochemically characterized using cyclic voltammetry. The parameters were optimized and the developed electrochemical sensor was applied in the determination of CQP using square-wave voltammetry (SWV). The analytical range for the determination of CQP was 0.5 to 110 μmol L⁻¹ (one of the highest linear ranges for CQP considering electrochemical sensors), with limits of detection and quantification of 0.23 and 0.78 μmol L⁻¹, respectively. Finally, the glassy carbon (GC) electrode modified with rGO-CuNPs was used for quantification of CQP in tap water; a study was carried out with interferents using SWV and obtained great results. The use of rGO-CuNP material as an electrode modifier was thus shown to be a good alternative for the development of low-cost devices for CQP analysis.

This paper describes for the first time the surface modification of glassy carbon (GC) electrodes with bamboo-based renewable carbon (RC) and antimony nanoparticles (SbNPs) for the determination of methylparaben (MePa) in personal care products (PCPs). The synthesized RC-SbNP material was successfully characterized by scanning electron microcopy, energy-dispersive X-ray spectroscopy and cyclic voltammetry. The proposed sensor was applied in the detection of MePa using the optimized parameters by differential pulse voltammetry (DPV). The analytical range for detection of MePa was 0.2 to 9.0 µmol L⁻¹, with limits of detection and quantification of 0.05 µmol L⁻¹ and 0.16 µmol L⁻¹, respectively. The determination of MePa in real PCP samples was performed using the proposed GC/RC-SbNP sensor by DPV and UV-vis spectrophotometry as comparative methodology. The use of RC-SbNP material for the development of electrochemical sensors brings a fresh approach to low-cost devices for MePa analysis.

Water contamination from endocrine disruptors has become a major problem for health issues. Estriol is a hormone often detected in several aquatic matrices, due to the inefficient removal of such compounds through conventional water treatment methods. Therefore, there is a continuous need to develop new, efficient, and low-cost treatment methods for this hormone removal, as well as analytical devices able to detect estriol at low concentrations. In this present study, we report the use of the Eichhornia crassipes (water hyacinth) as a phytoremediation agent for estriol removal from aqueous matrices, in addition to a newly developed electrochemical sensor based on reduced graphene oxide and copper nanoparticles as a quantification and monitoring tool of the hormone. The developed sensor presented a linear detection region from 0.5 to 3.0 μmol L⁻¹, with detection and quantification limits of 0.17 μmol L⁻¹ and 0.56 μmol L⁻¹, respectively. Phytoremediation experiments were conducted in 2 L beakers and the reducing levels of the hormone were studied. Water hyacinth was able to reduce contaminant levels by approximately 80.5% in 7 days and below detection limits in less than 9 days, which is a good alternative for water decontamination with this endocrine disruptor. Due to the hydrophobicity of estriol, the probable mechanism involved in the bioremediation process is rhizodegradation, and the decrease in pH in the beakers that contained the plants indicated a possible formation of biofilms on the roots.