Simultaneous voltammetric determination of Adrenaline and Tyrosine in real samples by neodymium oxide nanoparticles grafted graphene

Oatmeal-derived carbon loaded with Pt nanoparticles using a "two-fold benefit approach" for sensitive detection of the biomolecule adrenaline

In this study, we innovatively synthesized nitrogen-doped carbon microspheres (NCS) derived from oatmeal. By utilizing polyoxometalates (POM) as both reducing and linking agents, we achieved uniform loading of platinum nanoparticles (Pt NPs) onto the surface of the NCS. The composite nanoparticles constructed from Pt/polyoxometalate/nitrogen-doped carbon microspheres (Pt/POM/NCS) fully exploit the synergistic catalytic effect, demonstrating superior performance in adrenaline detection. The method has a linear range of 2.59 to 1109.59 μM, a detection limit as low as 0.25 μM (S/N = 3), and a sensitivity of 0.74 μA μM-1 cm-2. Additionally, it exhibits high stability and strong anti-interference ability. The recoveries in human serum were 98.51 % to 101.25 %.

Label-Free Mode Based on Ferrocene/PEDOT:PSS-PPy for Molecularly Imprinted Electrochemically Ultrasensitive Detection of Amino Acids

Generally, molecularly imprinted (MIP) electrochemical sensors for amino acids operate in a "label-like" mode. That is, after an amino acid is specifically recognized by an imprinted cavity at the sensing interface, the amino acid itself provides the sensing signal for quantitative detection. However, poorly electroactive amino acids impede electron transfer at the sensing interface and require high potentials to drive the reaction; thus, more interfering reactions tend to be triggered in practical applications, causing enhanced background noise in the detection. To address these issues, a "label-free" mode of the MIP sensor based on the ferrocene (Fc)/PEDOT:PSS-polypyrrole (PPy) composite was designed for the first time. The Fc/PEDOT:PSS-PPy is drop coated on the electrode surface as a substrate, and MIP polymers with specific recognition ability are immobilized on the substrate via electrostatic adsorption. As a proof of concept, l-tyrosine (l-Tyr) was selected as a model analyte and the "label-free" mode MIP/Fc/PEDOT:PSS-PPy sensor was constructed. The limit of detection (LOD) and linearity range of the MIP/Fc/PEDOT:PSS-PPy sensor were 2.31 × 10-11 M and from 100 pM to 5 mM, respectively. Compared with the label-like mode, the LOD was three orders of magnitude lower, the linear range was increased by three orders of magnitude, and the sensitivity was improved by more than four times. This work provides a universal and effective concept for MIP electrochemical sensing of amino acids.

Construction of an electrochemical sensing platform for the sensitive determination of chlorogenic acid in locally consumed bitter coffee known as Mirra

The demand for foods with high antioxidant capacity has increased and research on food analysis continues to increase. Chlorogenic acid is a potent antioxidant molecule and can exhibit various physiological activities. This study aims to analyze Mirra coffee for the determination of chlorogenic acid using an adsorptive voltammetric method. The method is based on the strong synergistic effect between carbon nanotubes and nanoparticles of gadolinium oxide and tungsten, providing sensitive determination of chlorogenic acid. The proposed method yielded a dynamic linear range of 2.5 × 10^-9 ∼ 1.6 × 10^-6 M with a detection limit of 1.08 × 10^-9 M for chlorogenic acid. The amount of chlorogenic acid in Mirra coffee was found to be 46.1 ± 0.69 mg/L by the proposed electrochemical platform.

Nanomaterial-based electrochemical sensors for detection of amino acids

Amino acids are the building blocks of proteins and muscle tissue. They also play a significant role in physiological processes related to energy, recovery, mood, muscle and brain function, fat burning and stimulating growth hormone or insulin secretion. Accurate determination of amino acids in biological fluids is necessary because any changes in their normal ranges in the body warn diseases like kidney disease, liver disease, type 2 diabetes and cancer. To date, many methods such as liquid chromatography, fluorescence mass spectrometry, etc. have been used for the determination of amino acids. Compared with the above techniques, electrochemical systems using modified electrodes offer a rapid, accurate, cheap, real-time analytical path through simple operations with high selectivity and sensitivity. Nanomaterials have found many interests to create smart electrochemical sensors in different application fields e.g. biomedical, environmental, and food analysis because of their exceptional properties. This review summarizes recent advances in the development of nanomaterial-based electrochemical sensors in 2017-2022 for the detection of amino acids in various matrices such as serum, urine, blood and pharmaceuticals.

A highly efficient metal oxide incorporated metal organic framework [Nd2O3-MIL(Fe)-88A] for the electrochemical detection of dichlorvos

In this study, a Nd₂O₃@MIL(Fe)-88A composite was prepared through a hydrothermal method and used to detect dichlorvos. The XRD result demonstrated that the prepared sensor is highly crystalline in nature. The affinity of metal oxide and MIL(Fe)-88A could be utilised to overcome low stability and sensitivity owing to their synergistic and electronic effects. Differential pulse voltammetry (DPV) exhibits the electrocatalytic behaviour of Nd₂O₃@MIL(Fe)-88A; it functions at a lower potential at -0.5 to 0.8 V and has a wide linear range of 1-250 nM. It shows a very low detection limit of 0.92 nM with good sensitivity (4.42 mA nM^-1) and selectivity. The developed Nd₂O₃@MIL(Fe)-88A sensor was successfully applied to detect dichlorvos in real analysis. The recovery range calculated for cabbage and orange extracts was 96-97% and 99.5-103.4%, respectively, and RSD% calculated for cabbage and orange extracts was from 1.40 to 3.39% and from 0.64 to 2.26%, respectively.

A bibliometric analysis of graphene in acetaminophen detection: Current status, development, and future directions

Acetaminophen is a widely used analgesic throughout the world. Detection of acetaminophen has particular value in pharmacy and clinics. Electrochemical sensors assembled with advanced materials are an effective method for the rapid detection of acetaminophen. Graphene-based carbon nanomaterials have been extensively investigated for potential analytical applications in the last decade. In this article, we selected papers containing both graphene and acetaminophen. Bibliometrics was used to analyze the relationships and trends among these papers. The results show that the topic has grown at a high rate since 2009. Among them, the detection of acetaminophen by an electrochemical sensor based on graphene is the most important direction. Graphene has moved from being a primary sensing material to a substrate for immobilization of other active ingredients. In addition, the degradation of acetaminophen using graphene-modified electrodes is also an important direction. We analyzed the research history and current status of this topic through bibliometrics. Authors, institutions, countries, and key literature were discussed. We also proposed perspectives for this topic.

Strategies, advances, and challenges associated with the use of graphene-based nanocomposites for electrochemical biosensors

Graphene is an intriguing two-dimensional honeycomb-like carbon material with a unique basal plane structure, charge carrier mobility, thermal conductivity, wide electrochemical spectrum, and unusual physicochemical properties. Therefore, it has attracted considerable scientific interest in the field of nanoscience and bionanotechnology. The high specific surface area of graphene allows it to support high biomolecule loading for good detection sensitivity. As such, graphene, graphene oxide (GO), and reduced GO are excellent materials for the fabrication of new nanocomposites and electrochemical sensors. Graphene has been widely used as a chemical building block and/or scaffold with various materials to create highly sensitive and selective electrochemical sensing microdevices. Over the past decade, significant advancements have been made by utilizing graphene and graphene-based nanocomposites to design electrochemical sensors with enhanced analytical performance. This review focus on the synthetic strategies, as well as the structure-to-function studies of graphene, electrochemistry, novel multi nanocomposites combining graphene, limit of detection, stability, sensitivity, assay time. Finally, the review describes the challenges, strategies and outlook on the future development of graphene sensors technology that would be usable for the internet of things are also highlighted.

Ti3C2TxMXene/nitrogen-doped reduced graphene oxide composite: a high-performance electrochemical sensing platform for adrenaline detection

Herein, Ti₃C₂T_xMXene/N-doped reduced graphene oxide (MXene/N-rGO) composite was employed as the electrocatalyst to construct a new electrochemical sensing platform for the determination of adrenaline (AD). The MXene/N-rGO was synthesized via a facile one-step hydrothermal method, where ethylenediamine acted as a reducing agent and N source. The doped N in rGO served as a bridge between MXene and rGO through tight hydrogen bonds. Scanning electron microscopy showed that large numbers of MXenes with accordion-like morphology were distributed on the surface of the N-rGO. The MXene/N-rGO composite displayed a synergetic catalytic effect for oxidizing AD, originating from the unique catalytic activity of N-rGO and the large surface area and satisfactory conductivity of MXene. These characteristics of composite material led to a remarkable effect on signal amplification for the detection of AD, with a wide linear range from 10.0 nM to 90.0μM and a low detection limit of 3.0 nM based on a signal to noise ratio of 3. Moreover, the MXene/N-rGO electrode displayed good stability, repeatability, and reproducibility. Additionally, the proposed sensor was successfully applied for voltammetric sensing of AD in urine with recoveries from 97.75% to 103.0%.

Nano-sized Metal and Metal Oxide Modified Electrodes for Pharmaceuticals Analysis

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The electrochemical analysis offers a number of important advantages such as providing information on pharmaceuticals analysis and their in vivo redox processes and pharmacological activity. The interest in developing electrochemical sensing devices for use in clinical assays is growing rapidly. Metallic nanoparticles can be synthesized and modified with various chemical functional groups, which allow them to be conjugated with antibodies, ligands, and drugs of interest.

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In this article, the novel developments to enhance the performance of sensor modified with metal nanoparticles of pharmaceuticals were reviewed. A discussion of the properties of metal nanostructures and their application in drug analysis is presented. Their application as a modifier agent in determining low levels of drugs in pharmaceutical dosage forms and biological samples is discussed. It has been found that the electrocatalytic effect of the electrode, sensitivity and selectivity were increased using various working electrodes modified with nano-sized metal, metal oxide and metal/metal oxide particles.

Electrochemical determination of chloramphenicol and metronidazole by using a glassy carbon electrode modified with iron, nitrogen co-doped nanoporous carbon derived from a metal-organic framework (type Fe/ZIF-8)

In this study, an iron-doped metal-organic framework (MOF) Fe/ZIF-8 was synthesized from ZIF-8 at room temperature. Direct carbonization of Fe/ZIF-8 under a nitrogen atmosphere produced nanoporous nitrogen doped carbon nanoparticles decorated with Fe component (Fe/NC). The Fe/NC exhibited a large surface area (1221.185 m² g^-1) and narrow pore-size distribution (3-5 nm). The nanoporous Fe/NC components along with Nafion were used to modify a glassy carbon electrode for the electrochemical determination of chloramphenicol and metronidazole via linear sweep voltammetry. Under optimal conditions, the reduction peak currents (observed at -0.237 V and -0.071 V vs. Ag/AgCl) of these analytes increased linearly with increasing chloramphenicol and metronidazole concentrations in the range of 0.1-100 μM and 0.5-30 μM, with the detection limits estimated to be 31 nM and 165 nM, respectively. This result was attributed to the large surface area, porous structure, high nitrogen content, and as well as the electrocatalytic effect of Fe atoms embeded in the carbon support. The proposed sensor was used for chloramphenicol and metronidazole analysis in samples, providing satisfactory results.