A sensitive electrochemical sensor based on aluminium doped copper selenide nanoparticles-modified screen printed carbon electrode for determination of L-tyrosine in pharmaceutical samples

Sensing the invisible: Ultra-low-level electrochemical detection of the microbe (Pseudomonas aeruginosa) on cobalt ferrite-doped silver nanocomposite (CoFe2O4/AgNPs) surfaces

This study introduces an efficient electrochemical method for rapidly identifying the pathogen Pseudomonas aeruginosa (P. aeruginosa), which poses threats to individuals with compromised immune systems and cystic fibrosis. Unlike conventional techniques such as polymerase chain reaction, which fails to detect modifications in the resistant properties of microbes due to environmental stress, our proposed electrochemical approach offers a promising alternative. The characterisation analyses, involving microscopic and spectroscopic methods, reveal that the nanocomposite exhibits a crystalline structure, specific atomic vibrational patterns, a cubic surface shape, and distinct elemental compositions. This sensor demonstrates exceptional detection capabilities for P. aeruginosa, with a linear range of 1-23 CFU mL-1 and a low detection limit of 4.0 × 10-3 CFU mL-1. This research not only explores novel electrochemical techniques and the CoFe2O4/AgNPs nanocomposite but also their practical implications in food science, highlighting their relevance across various food samples, water, and soil.

Electrochemical L-Tyrosine Sensor Based on a Glassy Carbon Electrode Modified with Exfoliated Graphene

In this study, a graphene sample (EGr) was synthesized by electrochemical exfoliation of graphite rods in electrolyte solution containing 0.1 M ammonia and 0.1 M ammonium thiocyanate. The morphology of the powder deposited onto a solid substrate was investigated by the scanning electron microscopy (SEM) technique. The SEM micrographs evidenced large and smooth areas corresponding to the basal plane of graphene as well as white lines (edges) where graphene layers fold-up. The high porosity of the material brings a major advantage, such as the increase of the active area of the modified electrode (EGr/GC) in comparison with that of bare glassy carbon (GC). The graphene modified electrode was successfully tested for L-tyrosine detection and the results were compared with those of bare GC. For EGr/GC, the oxidation peak of L-tyrosine had high intensity (1.69 × 10^-5 A) and appeared at lower potential (+0.64 V) comparing with that of bare GC (+0.84 V). In addition, the graphene-modified electrode had a considerably larger sensitivity (0.0124 A/M) and lower detection limit (1.81 × 10^-6 M), proving the advantages of employing graphene in electrochemical sensing.

Rapid Sample Screening Method for Authenticity Controlling of Vanilla Flavours Using Liquid Chromatography with Electrochemical Detection Using Aluminium-Doped Zirconia Nanoparticles-Modified Electrode

A rapid and sensitive technique for frauds determination in vanilla flavors was developed. The method comprises separation by liquid chromatography followed by an electrochemical detection using a homemade screen-printed carbon electrode modified with aluminium-doped zirconia nanoparticles (Al-ZrO₂-NPs/SPCE). The prepared nanomaterials (Al-ZrO₂-NPs) were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). This method allows for the determination of six phenolic compounds of vanilla flavors, namely, vanillin, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillyl alcohol, vanillic acid and ethyl vanillin in a linear range between 0.5 and 25 µg g^-1, with relative standard deviation values from 2.89 to 4.76%. Meanwhile, the limits of detection and quantification were in the range of 0.10 to 0.14 µg g^-1 and 0.33 to 0.48 µg g^-1, respectively. In addition, the Al-ZrO₂-NPs/SPCE method displayed a good reproducibility, high sensitivity, and good selectivity towards the determination of the vanilla phenolic compounds, making it suitable for the determination of vanilla phenolic compounds in vanilla real extracts products.

Electrochemical Sensor Based on ZnFe2O4/RGO Nanocomposite for Ultrasensitive Detection of Hydrazine in Real Samples

We have developed a highly sensitive sensor of ZnFe₂O₄/reduced graphene oxide (ZnFe₂O₄/RGO) nanocomposite for electrochemical detection of hydrazine, fabricated by a simple hydrothermal protocol. Subsequently, a screen-printed electrode (SPE) surface was modified with the proposed nanocomposite (ZnFe₂O₄/RGO/SPE), and revealed an admirable electrocatalytic capacity for hydrazine oxidation. The ZnFe₂O₄/RGO/SPE sensor could selectively determine micromolar hydrazine concentrations. The as-produced sensor demonstrated excellent ability to detect hydrazine due to the synergistic impacts of the unique electrocatalytic capacity of ZnFe₂O₄ plus the potent physicochemical features of RGO such as manifold catalytic sites, great area-normalized edge-plane structures, high conductivity, and large surface area. The hydrazine detection using differential pulse voltammetry exhibited a broad linear dynamic range (0.03–610.0 µM) with a low limit of detection (0.01 µM).

Surface Polymers on Multiwalled Carbon Nanotubes for Selective Extraction and Electrochemical Determination of Rhodamine B in Food Samples

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO₂NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO₂) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.

Highly sensitive determination of doxorubicin hydrochloride antitumor agent via a carbon nanotube/gold nanoparticle based nanocomposite biosensor

A glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs) decorated with gold nanoparticles has been investigated for the first time as an ultrasensitive electrochemical sensor for the determination of doxorubicin hydrochloride (DOX), an efficient antitumor agent. The developed nanocomposite has been characterized by scanning electron microscopy (SEM), besides cyclic and linear sweep voltammetry electrochemical techniques. An efficient catalytic activity for the reduction of DOX has been demonstrated, leading to a significant increase in peak current density and a remarkable decrease in reduction over-potential. Under the optimal condition, a wide linear DOX concentration range from 1×10^-11 to 1×10^-6 M with a very low detection limit of 6.5 pM was achieved with the modified electrode. Meanwhile, the functionalized MWCNTs/gold nanoparticles indicated an appropriate selectivity, reproducibility, and repeatability as well as long-term stability. The promising outcomes of this research approved the applicability of the developed nanocomposite sensor towards trace amounts of DOX in pharmaceutical and clinical preparations.