Characterization of the Electrochemical Profiles of Lycoris Seeds for Species Identification and Infrageneric Relationships

Feasibility Study of a Non-Contact Differentiation of Cannabidiol Concentrations Using Interdigital Electrodes

This feasibility study presents a novel noncontact method for differentiating standard cannabidiol (CBD) concentrations using optimized interdigital electrodes. The electrode design, with a 100 mm2 sensing area on a 64 mm × 77 mm FR-4 substrate, was improved through finite element analysis. Methanol-CBD solutions (25-1000 ppm) in 2 mL glass vials were analyzed using a vector network analyzer connected via a high-frequency SMA connector, focusing on scattering parameter (S-parameter) changes. The method demonstrated high effectiveness in CBD concentration differentiation, achieving a concentration resolution of 145 MHz/50 ppm based on resonant frequency shift, with an error of 0.17% of the reading, and 0.5 dB/50 ppm using S11 amplitude measurement. The proposed method offers a promising, linear, and precise technique for noncontact CBD standard analysis, with potential applications in future research. In addition, impedance measurements can be applied to enhance concentration differentiation further.

Analysis of Electrochemically Active Substances in Malvaceae Leaves via Electroanalytical Sensing Technology for Species Identification

Electrochemical analysis has become a new method for plant analysis in recent years. It can not only collect signals of electrochemically active substances in plant tissues, but can also be used to identify plant species. At the same time, the signals of electrochemically active substances in plant tissues can also be used to investigate plant phylogeny. In this work, we collected electrochemical finger patterns in Malvaceae leaves based on the established methodological strategy. After the second derivative treatment, the collected electrochemical fingerprints can show more obvious differences. Three different recognition models were used to attempt electrochemical fingerprinting. The results show that linear support vector classification can be used to identify species with high accuracy by combining the electrochemical fingerprint signals collected in the phosphoric acid buffer solution and acetic acid buffer solution. In addition, the fingerprint information collected by the electrochemical sensor is further used for phylogenetic investigation. The 18 species were divided into three clusters. Species of the same genus have been clustered together. Dendrogram obtained by electrochemical fingerprinting was used to compare previously reported results deduced from morphological and complete chloroplast genomes.

Changes in and Recognition of Electrochemical Fingerprints of Acer spp. in Different Seasons

Electroanalytical chemistry is a metrological analysis technique that provides information feedback by measuring the voltammetric signal that changes when a molecule is involved in an electrochemical reaction. There is variability in the type and content of electrochemically active substances among different plants, and the signal differences presented by such differences in electrochemical reactions can be used for plant identification and physiological monitoring. This work used electroanalytical chemistry to monitor the growth of three Acer spp. This work explores the feasibility of the electrochemical analysis technique for the physiological monitoring of highly differentiated plants within the genus and further validates the technique. Changes in the electrochemical fingerprints of A. cinnamomifolium, A. sinopurpurascens and A. palmatum 'Matsumurae' were recorded during the one-year developmental cycle. The results show that the differences in the electrochemical fingerprint profiles of Acer spp. can be used to distinguish different species and identify the growth status in each season. This work also concludes with an identification flowchart based on electrochemical fingerprinting.

Electrochemical fingerprinting sensor for plant phylogenetic investigation: A case of sclerophyllous oak

Electrochemical fingerprinting can collect the electrochemical behavior of electrochemically active molecules in plant tissues, so it is regarded as a new plant analysis technology. Because the signal of electrochemical fingerprinting is positively correlated with the amount and type of electrochemically active molecules in plant tissues, it can also be used to reflect genetic differences between different species. Previous electrochemical fingerprinting techniques have been frequently used in phylogenetic studies of herbaceous plants. In this work, 19 Quercus species (17 evergreen or semi evergreen species and 2 deciduous species) were selected for investigation. The results indicated the electrochemical fingerprint of some species share similar features but can be distinguished after changing the recording condition (extraction solvent and electrolyte). The two sets of electrochemical fingerprint data can be used to construct different pattern recognition technology, which further speeds up the recognition efficiency. These electrochemical fingerprints were further used in phylogenetic investigations. The phylogenetic results deduced from electrochemical fingerprinting were divided mainly into three clusters. These can provide evidence for some of these arguments as well as new results.

A scientometric study on application of electrochemical sensors for detection of pesticide using graphene-based electrode modifiers

Pesticide testing is an important topic in environmental protection and food safety. The development of green, accurate and reliable pesticide residue detection methods is an important technical support for implementing of agricultural quality supervision. Electrochemical sensors are a very promising analytical method for pesticide detection due to their high sensitivity, speed, low cost and portability. Performance enhancement of electrochemical sensors is often accompanied by research advances in materials science. Among them, carbon material is a very important electrode material for the fabrication of electrochemical sensors. The discovery of graphene makes it the most promising candidate among carbon materials for sensor performance enhancement. The topic of this review is the use of graphene-modified electrochemical sensors for pesticide detection in the last decade. Traditional literature summaries and bibliometric analyses were used for an in-depth analysis of this topic. In addition to the introduction of different sensor types and performance comparisons, this review also parses the authors' country, keywords and publication frequency. The related research experienced rapid growth several years ago and has now reached a relatively stable stage. We also discuss the perspectives on this topic.

Graphene-based electrochemical sensors for antibiotic detection in water, food and soil: A scientometric analysis in CiteSpace (2011-2021)

The residues of antibiotics in the environment pose a potential health hazard, so highly sensitive detection of antibiotics has always appealed to analytical chemists. With the widespread use of new low-dimensional materials, graphene-modified electrochemical sensors have emerged as an excellent candidate for highly sensitive detection of antibiotics. Graphene, its derivatives and its composites have been used in this field of exploration in the last decade. In this review, we have not only described the field using traditional summaries, but also used bibliometrics to quantify the development of the field. The literature between 2011 and 2021 was included in the analysis. Also, the sensing performance and detection targets of different sensors were compared. We were able to trace not only the flow of research themes, but also the future areas of development. Graphene is a material that has a high potential to be used on a large scale in the preparation of electrochemical sensors. How to design a sensor with selectivity and low cost is the key to bring this material from the laboratory to practical applications.

Preparation of highly sensitive electrochemical sensor for detection of nitrite in drinking water samples

Nitrite is both an environmental contaminant and a food additive. Excessive intake of nitrites not only causes blood diseases, but also has the potential risk of causing cancer. Therefore, rapid detection of nitrite in water is necessary. In this work, we propose an electrochemical sensor for the sensing of nitrite. Glassy carbon electrodes modified with noble metal nanomaterials have been widely used in the preparation of sensors, but the surface properties of noble metals largely affect the sensing performance. This work proposes the biosynthesis of Au nanoparticles using the pollen extract of Lycoris radiata as a reducing agent. Flavonoids rich in pollen can be used as weak reducing agents for the reduction of chloroauric acid, and slowly synthesize uniformly dispersed Au nanoparticles. These Au nanoparticles do not agglomerate because they contain small biological molecules on the surface and can form a homogeneous sensing interface on the electrode surface. The electrochemical sensor assembled with biosynthesized Au nanoparticles provides linear detection of nitrite between 0.01 and 3.8 mM. The sensor also has excellent immunity to interference. In addition, the proposed sensor was also successfully used for the detection of nitrite in drinking water.

Construction of Electrochemical Aptamer Sensor Based on Pt-Coordinated Titanium-Based Porphyrin MOF for Thrombin Detection

In this work, a Pt-coordinated titanium-based porphyrin metal organic framework (Ti-MOF-Pt) was prepared by embedding single-atom Pt through strong interactions between the four pyrrole nitrogen atoms in the rigid backbone of the porphyrin. The synthesized Ti-MOF-Pt was characterized by TEM, XRD, FTIR and BET. Then, the Ti-MOF-Pt has been used for glassy carbon electrode surface modification and consequently used for construction of a thrombin aptamer sensor. The high surface area provides by MOF and excellent electrochemical property provided by Pt enhance the sensing performance. After optimization of amount of aptamer, hybridization time and specific reaction time, the fabricated aptamer sensor exhibited a linear relationship with the logarithm of the thrombin concentration in the range of 4 pM to 0.2 μM. The detection limit can be calculated as 1.3 pM.

Electrochemical Sensors and Biosensors for the Analysis of Tea Components: A Bibliometric Review

Tea is a popular beverage all around the world. Tea composition, quality monitoring, and tea identification have all been the subject of extensive research due to concerns about the nutritional value and safety of tea intake. In the last 2 decades, research into tea employing electrochemical biosensing technologies has received a lot of interest. Despite the fact that electrochemical biosensing is not yet the most widely utilized approach for tea analysis, it has emerged as a promising technology due to its high sensitivity, speed, and low cost. Through bibliometric analysis, we give a systematic survey of the literature on electrochemical analysis of tea from 1994 to 2021 in this study. Electrochemical analysis in the study of tea can be split into three distinct stages, according to the bibliometric analysis. After chromatographic separation of materials, electrochemical techniques were initially used only as a detection tool. Many key components of tea, including as tea polyphenols, gallic acid, caffeic acid, and others, have electrochemical activity, and their electrochemical behavior is being investigated. High-performance electrochemical sensors have steadily become a hot research issue as materials science, particularly nanomaterials, and has progressed. This review not only highlights these processes, but also analyzes and contrasts the relevant literature. This evaluation also provides future views in this area based on the bibliometric findings.

The Application of Electrochemical Oscillation Methods for Identification of Traditional Chinese Medicine Materials

Electrochemical oscillation reflects the overall characteristics of the system under test in terms of redox activity. It has proven to be advantageous in analyzing and processing complex components of herbal systems, such as polysaccharides and proteins. Therefore, it is widely used in the quantitative or qualitative tests of traditional Chinese medicines (TCMs) for identification and quality control. Electrochemical oscillation has several advantages such as high sensitivity, stability and micro sample requirement. Compared with other traditional methods, the interaction of multi-component in the TCMs was taken into account, which provides new ideas for the search of TCMs. Here, we presented a brief introduction on the progress on the topic, which promoted the development of electrochemical oscillation and the standardization of TCMs in the last twenty years. Electrochemical oscillation method is cheap, sensitive, fast, stable and convenient for the identification and quality control of TCMs. Reaction systems and the visualization of the fingerprints can be improved in the future.

Point-of-Care Based Electrochemical Immunoassay for Epstein-Barr Virus Detection

This work describes a label-free electrochemical immunosensor for the sensing of Epstein-Barr virus (EBV) with high sensitivity. First, a monolayer of 1,6-hexanedithiol (HDT) was fabricated on the screen-printed electrode surface by the interaction between sulfur atoms and SPE. AuNPs can be modified on the electrode by the Au-S bond formed between the HDT-free group and Au atom in AuNPs. Protein A is then adsorbed onto AuNPs. Several parameters were optimized. The optimum concentration of protein A is 0.6 mg/mL. The optimum immobilization time for protein A is 90 min. The optimum concentration of antibody is 80 μg/mL. The optimum immobilization time for antibody is 90 min. Directional immobilization of EBV antibody is achieved by high affinity binding of protein A to the Fc segment of antibody. When antigen specifically binds to antibody, the formation of immune complexes blocks electron transfer of [Fe(CN)6]^4-/3- and is reflected in the detection of cyclic voltammetry/electrochemical impedance spectroscopy. The detection range is 1 pg/mL-l00 ng/mL with a LOD of 0.1 pg/mL. In addition, the proposed sensor exhibited an excellent antiinterference property.

Can Electrochemical Sensors Be Used for Identification and Phylogenetic Studies in Lamiaceae?

Electrochemical sensors have shown potential in recent years for plant species identification and phylogenetic studies. These works have been used to investigate the affinities of different species in many genera. However, the ability of electrochemical sensors to study relationships between different genera within a family has not been investigated. In this work, we selected 31 species in the Labiatae and 5 exotaxa as subjects to investigate the feasibility of electrochemical sensors at the genus level. The results show that electrochemical sensors are still very effective for the identification of these plants. Different pattern recognition techniques can make the identification more efficient. Also, the fingerprint profiles collected by the sensors can be used for phylogenetic studies of Labiatae. The phylogram divides all the species into five clusters, where the exotaxa are in one cluster. Species in the Labiatae are mainly distributed in four other clusters. Importantly, the different genera of species all showed close affinities, representing that electrochemical fingerprinting can well distinguish the affinities between the different genera. The results of this work demonstrate the great potential of electrochemical sensors in the study of plant phylogeny. Its application is not limited to the study at the species level, but can be extended to the genus level.

Conductive Hydrogel-Based Electrochemical Sensor: A Soft Platform for Capturing Analyte

Electrode modifications for electrochemical sensors attract a lot of attention every year. Among them, hydrogels are a relatively special class of electrode modifier. Since hydrogels often contain polymers, even though they are conductive polymers, they are not ideal electrode modifiers because of their poor conductivity. However, the micro-aqueous environment and the three-dimensional structure of hydrogels are an excellent platform for immobilizing bioactive molecules and maintaining their activity. This gives the hydrogel-modified electrochemical sensor the potential to perform specific recognition. At the same time, the rapid development of nanomaterials also makes the composite hydrogel have good electrical conductivity. This has led many scientists to become interested in hydrogel-based electrochemical sensors. In this review, we summarize the development process of hydrogel-based electrochemical sensors, starting from 2000. Hydrogel-based electrochemical sensors were initially used only as a carrier for biomolecules, mostly for loading enzymes and for specific recognition. With the widespread use of noble metal nanoparticles and carbon materials, hydrogels can now be used to prepare enzyme-free sensors. Although there are some sporadic studies on the use of hydrogels for practical applications, the vast majority of reports are still limited to the detection of common model molecules, such as glucose and H2O2. In the review, we classify hydrogels according to their different conducting strategies, and present the current status of the application of different hydrogels in electrochemical sensors. We also summarize the advantages and shortcomings of hydrogel-based electrochemical sensors. In addition, future prospects regarding hydrogel for electrochemical sensor use have been provided at the end.

Quantification of Silicon in Rice Based on an Electrochemical Sensor via an Amplified Electrocatalytic Strategy

Silicon plays a very important role in the growth of rice. The study of the relationship between rice and silicon has become a hot area in the last decade. Currently, the silica-molybdenum blue spectrophotometric method is mostly used for the determination of silicon content in rice. However, the results of this method vary greatly due to the different choices of reducing agents, measurement wavelengths and color development times. In this work, we present for the first time an electrochemical sensor for the detection of silicon content in rice. This electrochemical analysis technique not only provides an alternative detection strategy, but also, due to the rapid detection by electrochemical methods and the miniaturization of the instrument, it is suitable for field testing. Methodological construction using electrochemical techniques is a key objective. The silicon in rice was extracted by HF and becomes silica after pH adjustment. The silica was then immobilized onto the glassy carbon surface. These silica nanoparticles provided additional specific surface area for adsorption of sodium borohydride and Ag ions, which in turn formed Ag nanoparticles to fabricate an electrochemical sensor. The proposed electrochemical sensor can be used for indirect measurements of 10-400 mg/L of SiO₂, and thus, the method can measure 4.67-186.8 mg/g of silicon. The electrochemical sensor can be used to be comparable with the conventional silicon-molybdenum blue spectrophotometric method. The RSD of the current value was only 3.4% for five sensors. In practical use, 200 samples of glume, leaf, leaf sheath and culm were tested. The results showed that glume had the highest silicon content and culm had the lowest silicon content. The linear correlation coefficients for glume, leaf, leaf sheath and culm were 0.9841, 0.9907, 0.9894 and 0.993, respectively.

Evaluation of Peroxidase in Herbal Medicines Based on an Electrochemical Sensor

Peroxidases are species-specific. Differences in peroxidase can objectively reflect the genetics among species. The use of peroxidase to assist in species identification is relatively simple and effective. In this work, we proposed a graphene-modified electrode. This electrode can amplify the signal of electrocatalytic reduction of hydrogen peroxide. Since peroxidase can catalyze the reduction of hydrogen peroxide, this signal can be used as an indicator to demonstrate the content of peroxidase in different plant tissues. Twelve herbal medicines were selected for our study. The results show that this electrochemical-based detection technique was comparable to colorimetric method in terms of accuracy.

Emerging electrochemical sensing and biosensing approaches for detection of Fumonisins in food samples

Fumonisins (FBs) can be found extensively in feedstuffs, foodstuffs, and crops. The consumption of the fumonisin-contaminated corn can result in esophageal cancer. In addition, the secondary metabolites of fungi termed mycotoxins may have some adverse effects on animals and humans such as estrogenicity, immunotoxicity, teratogenicity, mutagenicity, and carcinogenicity. Hence, developing sensitivity techniques for mycotoxins determination is of great importance. This paper reports the latest developments of nanomaterial-based electrochemical biosensing, apta-sensing, sensing, and immunosensing analyses to detect fumonisins. A concise study of the occurrence, legislations, toxicity, and distribution of FBs in levels monitoring was done. The techniques, different detection matrices, and approaches to highly selective and sensitive sensing methods were reviewed. The review also summarizes the salient features and the necessity of biosensing assessments in FBs detection, and diverse immobilization techniques. Furthermore, this review defined the performance of various electrochemical sensors using different detection elements couples with nanomaterials fabricated applying different detection elements coupled with nanomaterials (metal oxide nanoparticles (NPs), metal NPs, CNT, and graphene), the factors limiting progress, and the upcoming tasks in successful aptasensor fabrication with the functionalized nanomaterials.

A Methylene Blue Assisted Electrochemical Sensor for Determination of Drug Resistance of Escherichia coli

Due to the abuse of antibiotics in clinical, animal husbandry, and aquaculture, drug-resistant pathogens are produced, which poses a great threat to human and the public health. At present, a rapid and effective drug sensitivity test method is urgently needed to effectively control the spread of drug-resistant bacteria. Using methylene blue as a redox probe, the electrochemical signals of methylene blue in drug-resistant Escherichia coli strains were analyzed by a CV method. Graphene ink has been used for enhancing the electrochemical signal. Compared with the results of the traditional drug sensitivity test, we proposed a rapid electrochemical drug sensitivity test method which can effectively identify the drug sensitivity of Escherichia coli. The sensitivity of four E. coli isolates to ciprofloxacin, gentamicin, and ampicillin was tested by an electrochemical drug sensitivity test. The respiratory activity value %RA was used as an indicator of bacterial resistance by electrochemical method.

Electrochemical Fingerprint Biosensor for Natural Indigo Dye Yielding Plants Analysis

Indigo is a plant dye that has been used as an important dye by various ancient civilizations throughout history. Today, due to environmental and health concerns, plant indigo is re-entering the market. Strobilanthes cusia (Nees) Kuntze is the most widely used species in China for indigo preparation. However, other species under Strobilanthes have a similar feature. In this work, 12 Strobilanthes spp. were analyzed using electrochemical fingerprinting technology. Depending on their electrochemically active molecules, they can be quickly identified by fingerprinting. In addition, the fingerprint obtained under different conditions can be used to produce scattered patter and heatmap. These patterns make plant identification more convenient. Since the electrochemically active components in plants reflect the differences at the gene level to some extent, the obtained electrochemical fingerprints are further used for the discussion of phylogenetics.

A Novel Graphene-Based Nanomaterial Modified Electrochemical Sensor for the Detection of Cardiac Troponin I

Acute myocardial infarction has a high clinical mortality rate. The initial exclusion or diagnosis is important for the timely treatment of patients with acute myocardial infarction. As a marker, cardiac troponin I (cTnI) has a high specificity, high sensitivity to myocardial injury and a long diagnostic window. Therefore, its diagnostic value is better than previous markers of myocardial injury. In this work, we propose a novel aptamer electrochemical sensor. This sensor consists of silver nanoparticles/MoS₂/reduced graphene oxide. The combination of these three materials can provide a synergistic effect for the stable immobilization of aptamer. Our proposed aptamer electrochemical sensor can detect cTnl with high sensitivity. After optimizing the parameters, the sensor can provide linear detection of cTnl in the range of 0.3 pg/ml to 0.2 ng/ml. In addition, the sensor is resistant to multiple interferents including urea, glucose, myoglobin, dopamine and hemoglobin.

Detection of Imatinib Based on Electrochemical Sensor Constructed Using Biosynthesized Graphene-Silver Nanocomposite

The establishment of a monitoring technique for imatinib is necessary in clinical and environmental toxicology. Leaf extracts of Lycoris longituba were used as reducing agent for the one-step synthesis of reduced graphene oxide-Ag nanocomposites. This nanocomposite was characterized by TEM, FTIR, XRD, and other instruments. Then, the graphene/Ag nanocomposite was used as a modifier to be cemented on the surface of the glassy carbon electrode. This electrode exhibited excellent electrochemical sensing performance. Under the optimal conditions, the proposed electrode could detect imatinib at 10 nM−0.28 mM with a low limit of detection. This electrochemical sensor also has excellent anti-interference performance and reproducibility.

Preparation of Graphene Oxide-Embedded Hydrogel as a Novel Sensor Platform for Antioxidant Activity Evaluation of Scutellaria baicalensis

Antioxidation is very important in medicine and food. The current evaluation technologies often have many shortcomings. In this work, an improved electrochemical sensing platform for the evaluation of antioxidant activity has been proposed. A hydrogel was prepared based on graphene oxide, zinc ions, and chitosan. Zinc ions play the role of crosslinking agents in hydrogels. The structure of chitosan can be destroyed by injecting hydrogen peroxide into the hydrogel, and the free zinc ions can diffuse to the surface of the electrode to participate in the electrochemical reaction. This electrochemical sensor can evaluate the antioxidant activity by comparing the current difference of zinc reduction before and after adding the antioxidant. With the help of graphene oxide, this hydrogel can greatly enhance the sensing effect. We conducted tests on 10 real samples. This proposed electrochemical platform has been successfully applied for evaluating the antioxidant activity of Scutellaria baicalensis, and the results were compared to those obtained from the 2,2-diphenyl-1-picrylhydrazyl-based traditional analysis technique.

Investigation of the spectroelectrochemical behavior of quercetin isolated from Zanthoxylum bungeanum

Flavonoids are common bioactive components in plants. Quercetin is the most abundant flavonoid in the human diet, accounting for more than half of the total daily consumption of flavonoids. In this study, adsorption and electrocatalytic activities of quercetin isolated from Zanthoxylum bungeanum on an electrode was studied via homemade electrodes. An in situ UV-Visible thin-layer spectroelectrochemical method was used to study the electrochemical behavior of quercetin in detail and to explore its electrochemical reaction mechanism. This experiment proves that UV-Vis thin-layer spectroelectrochemistry is a feasible way for studying the electrochemical reaction mechanism of flavonoids in plants.

Polyethylene Terephthalate-Based Materials for Lithium-Ion Battery Separator Applications: A Review Based on Knowledge Domain Analysis

As the key material of lithium battery, separator plays an important role in isolating electrons, preventing direct contact between anode and cathode, and allowing free passage of lithium ions in the electrolyte. Polyethylene terephthalate (PET) has excellent mechanical, thermodynamic, and electrical insulation properties. This review aims to identify the research progress and development trends of PET-based material for separator application. We retrieved published papers (2004–2019) from the Scientific Citation Index Expanded (SCIE) database of the WoS with a topic search related to PET-based material for separator application. The research progress and development trends were analyzed based on the CiteSpace software of text mining and visualization.

Horseradish Peroxidase Labelled-Sandwich Electrochemical Sensor Based on Ionic Liquid-Gold Nanoparticles for Lactobacillus brevis

Lactobacillus brevis is the most common bacteria that causes beer spoilage. In this work, a novel electrochemical immunosensor was fabricated for ultra-sensitive determination of L. brevis. Gold nanoparticles (AuNPs) were firstly electro-deposited on the electrode surface for enhancing the electro-conductivity and specific surface area. Ionic liquid was used for improving the immobilization performance of the immunosensor. After optimization, a linear regression equation can be observed between the ∆current and concentration of L. brevis from 104 CFU/mL to 109 CFU/mL. The limit of detection can be estimated to be 103 CFU/mL.