History of Electroanalytical Methods

Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform

The properties of electrodes play a crucial role in the processes occurring on them. Therefore, a variety of materials have been tried as electrodes. Carbon composite materials are among the most admired ones. Use of composites as electrode material dates back to the mid of the last century when polymer-carbon composites were tried as general-purpose electrode platforms and epoxy impregnated graphite paste/ solid electrodes were tried in polarography. Later the composite electrodes have seen several phases of development. Plastic Chip Electrode (PCE) is a class of polymer composite electrode developed by our group. This monographic review gives a bird's eye account of polymer composite electrodes and appurtenant work, followed by elaborating on various aspects and state-of-the-art plastic chip electrodes.

SEI growth on Lithium metal anodes in solid-state batteries quantified with coulometric titration time analysis

Lithium-metal batteries with a solid electrolyte separator are promising for advanced battery applications, however, most electrolytes show parasitic side reactions at the low potential of lithium metal. Therefore, it is essential to understand how much (and how fast) charge is consumed in these parasitic reactions. In this study, a new electrochemical method is presented for the characterization of electrolyte side reactions occurring on active metal electrode surfaces. The viability of this new method is demonstrated in a so-called anode-free stainless steel ∣ Li6PS5Cl ∣ Li cell. The method also holds promise for investigating dendritic lithium growth (and dead lithium formation), as well as for analyzing various electrolytes and current collectors. The experimental setup allows easy electrode removal for post-mortem analysis, and the SEI's heterogeneous/layered microstructure is revealed through complementary analytical techniques. We expect this method to become a valuable tool in the future for solid-state lithium metal batteries and potentially other cell chemistries.

Recent Progress of Covalent Organic Frameworks Applied in Electrochemical Sensors

As an emerging porous crystalline organic material, the covalent organic frameworks (COFs) are given more and more attention in many fields, such as gas storage and separation, catalysis, energy storage and conversion, luminescent devices, drug delivery, pollutant adsorption and removal, analysis and detection due to their special advantages of high crystallinity, flexible designability, controllable porosities and topologies, intrinsic chemical and thermal stability. In recent years, the COFs are applied in analytical chemistry, for instance, chromatography, solid-phase microextraction, luminescent and colorimetric sensing, surface-enhanced Raman scattering and electroanalytical chemistry. The COFs decorated electrodes show high performance for detecting trace substances with remarkable selectivity and sensitivity, such as heavy metal ions, glucose, hydrogen peroxide, drugs, antibiotics, explosives, phenolic compounds, pesticides, disease metabolites and so on. This review mainly summarized the application of COF based electrochemical sensor according to different target analytes.

Significance of an Electrochemical Sensor and Nanocomposites: Toward the Electrocatalytic Detection of Neurotransmitters and Their Importance within the Physiological System

A prominent neurotransmitter (NT), dopamine (DA), is a chemical messenger that transmits signals between one neuron to the next to pass on a signal to and from the central nervous system (CNS). The imbalanced concentration of DA may cause numerous neurological sicknesses and syndromes, for example, Parkinson's disease (PD) and schizophrenia. There are many types of NTs in the brain, including epinephrine, norepinephrine (NE), serotonin, and glutamate. Electrochemical sensors have offered a creative direction to biomedical analysis and testing. Researches are in progress to improve the performance of sensors and develop new protocols for sensor design. This review article focuses on the area of sensor growth to discover the applicability of polymers and metallic particles and composite materials as tools in electrochemical sensor surface incorporation. Electrochemical sensors have attracted the attention of researchers as they possess high sensitivity, quick reaction rate, good controllability, and instantaneous detection. Efficient complex materials provide considerable benefits for biological detection as they have exclusive chemical and physical properties. Due to distinctive electrocatalytic characteristics, metallic nanoparticles add fascinating traits to materials that depend on the material's morphology and size. Herein, we have collected much information on NTs and their importance within the physiological system. Furthermore, the electrochemical sensors and corresponding techniques (such as voltammetric, amperometry, impedance, and chronoamperometry) and the different types of electrodes' roles in the analysis of NTs are discussed. Furthermore, other methods for detecting NTs include optical and microdialysis methods. Finally, we show the advantages and disadvantages of different techniques and conclude remarks with future perspectives.

A Journey from the Drops of Mercury to the Mysterious Shores of the Brain: The 100-Year Adventure of Voltammetry

Voltammetry, which is at the core of electroanalytical chemistry, is an analytical method that investigates and evaluates the current-potential relationship obtained at a given working electrode. If it is used dropping mercury as working electrode, the method is called as polarography. The current year 2022 marks the 100th anniversary of the discovery of polarography by Czech Jaroslav Heyrovský. He received the Nobel Prize in Chemistry in 1959 for this discovery and his contribution to the scientific world. A hundred years, within the endless existence of the universe is maybe nothing. A hundred years, in the history of mankind is a line, maybe a short paragraph. But, in science, a hundred years can lead to very significant advances in a field and often to the birth and establishment of an entirely new scientific discipline. Indeed, in the last hundred years, the design and use of new electrochemical devices, depending on the progress in microelectronics and computer technologies, has almost revolutionized voltammetry. Besides these developments, due to the fact that the redox (oxidation/reduction) process is very basic for living organisms; the voltammetry, especially with the beginning of the 21st century, has started to be used as a very powerful tool in neuroscience to solve the mystery of the brain (the basic problems of biomolecules with physiological and genetic importance in brain tissue). This review article is an overview of the 100-year history and fascinating development of voltammetry from Heyrovský to the present.

A new voltammetric platform for reliable determination of the sport performance-enhancing stimulant synephrine in dietary supplements using a boron-doped diamond electrode

For the first time, we propose a new modification-free voltammetric platform for simple, fast and reliable quantification of the sport performance-enhancing stimulant synephrine (SYN) based on the usage of a commercial screen-printed boron-doped diamond (BDD) electrochemical sensor. Applying cyclic voltammetry, SYN exhibited one well-shaped, irreversible and diffusion-driven oxidation peak at a peak potential of +1.45 V (vs. the silver pseudoreference electrode) in the presence of 2 M HClO₄. Under the selected experimental conditions, the following analytical parameters for determination of SYN were obtained: linear concentration ranges from 19.6 up to 1000 μM and from 9.9 up to 1000 μM for differential pulse (DPV) and square-wave voltammetry (SWV), respectively, detection limits at micromolar concentration levels and intra-day repeatability with a relative standard deviation below 4% for both pulse techniques. The interference study revealed fair selectivity when considering the target dietary supplements. The feasibility of the developed voltammetric platform was verified in the analysis of commercially available dietary supplements and reasonable recovery values were achieved by DPV and SWV, respectively. In addition, the method can be performed directly without higher consumption of chemicals, waste generation, complex sample extraction and higher instrumentation cost. The advanced BDD electrochemical sensor has appeared to be a suitable competitor for efficient applications in food quality control analysis.

Phthalocyanine Modified Electrodes in Electrochemical Analysis

Phthalocyanines are aromatic or macrocyclic organic compounds and attract great attention due to their numerous properties. They have many high-tech applications in different areas of the industry such as dyestuffs, thermal printing screens, photovoltaic solar cells, membrane catalytic reactors, semiconductor materials and gas sensors. In the last decade, electrochemical sensor studies have accelerated with the catalytic lighting. It plays a dominant role in the development and implementation of new generation sensors. The aim of this study is to review the electrochemical methods based on electrode modification with phthalocyanines and to shed light on new application areas of phthalocyanines. The focal point was based on the sensor applications of phthalocyanines in the determination of drugs, pesticides, organic materials and metals etc. by electrochemical methods. Experimental conditions and some validation parameters of the sensor applications such as metal phthalocyanine types, indicator electrodes, selectivity, working ranges, detection limits, and analytical applications were discussed. Consequently, this is the first review dealing with the applications of phthalocyanines in electrochemical sensors for the sensitive determination of analytes in a variety of matrices.

Electroanalysis from the past to the twenty-first century: challenges and perspectives

A personal mini-review is presented on the history of electroanalysis and on their present achievements and future challenges. The manuscript is written from the subjective view of two generations of electroanalytical chemists that have witnessed for many years the evolution of this discipline.

Synthesis and characterization of the thermally reduced graphene oxide in argon atmosphere, and its application to construct graphene paste electrode as a naptalam electrochemical sensor

New insight into the preparation of sensitive carbon-based electrochemical electrode is provided by examining the properties of thermally reduced graphene oxide (TRGO). In this paper, TRGO was prepared by thermal reduction of graphene oxide (GO) in argon atmosphere, and characterized by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM). Results showed that thermal reduction in argon was effective to remove oxygen-containing functional groups in GO, and graphene sheets were obtained. Furthermore, TRGO was used to prepare thermally reduced graphene oxide paste electrode (TRGOPE) which showed excellent conductivity and fast electron transfer kinetics confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrode was applied to determination of the pesticide naptalam (Nap) in square-wave voltammetric (SWV) mode. The corresponding current at approx. +1.0 V increased linearly with the Nap concentration within two linear dynamic ranges (LDR) of 0.1-1.0 μmol L^-1 (LDR₁) and 1.0-10.0 μmol L^-1 (LDR₂). The limits of detection (LOD) and quantification (LOQ) for Nap were calculated as 0.015 μmol L^-1 and 0.051 μmol L^-1, respectively. In comparison to the carbon paste electrode (CPE) the results showed that the TRGOPE possesses advantages in terms of linearity, sensitivity and detectability.

Electronic control of DNA-based nanoswitches and nanodevices

Here we demonstrate that we can rationally and finely control the functionality of different DNA-based nanodevices and nanoswitches using electronic inputs. To demonstrate the versatility of our approach we have used here three different model DNA-based nanoswitches triggered by heavy metals and specific DNA sequences and a copper-responsive DNAzyme. To achieve electronic-induced control of these DNA-based nanodevices we have applied different voltage potentials at the surface of an electrode chip. The applied potential promotes an electron-transfer reaction that releases from the electrode surface a molecular input that ultimately triggers the DNA-based nanodevice. The use of electronic inputs as a way to finely activate DNA-based nanodevices appears particularly promising to expand the available toolbox in the field of DNA nanotechnology and to achieve a better hierarchical control of these platforms.

Miniaturization in voltammetry: ultratrace element analysis and speciation with twenty-fold sample size reduction

Voltammetric techniques have emerged as powerful methods for the determination and speciation of trace and ultratrace elements without any preconcentration in several research fields. Nevertheless, large sample volumes are typically required (10 mL), which strongly limits their application and/or the precision of the results. In this work, we report a 20-fold reduction in sample size for trace and ultratrace elemental determination and speciation by conventional voltammetric instrumentation, introducing the lowest amount of sample (0.5 mL) in which ultratrace detection has been performed up to now. This goal was achieved by a careful design of a new sample holder. Reliable, validated results were obtained for the determination of trace/ultratrace elements in rainwater (Cd, Co, Cu, Ni, Pb) and seawater (Cu). Moreover, copper speciation in seawater samples was consistently determined by competitive ligand equilibration-cathodic stripping voltammetry (CLE-CSV). The proposed apparatus showed several advantages: (1) 20-fold reduction in sample volume (the sample size is lowered from 120 to 6 mL for the CLE-CSV procedure); (2) decrease in analysis time due to the reduction in purging time up to 2.5 fold; (3) 20-fold drop in reagent consumption. Moreover, the analytical performances were not affected: similar detection capabilities, precision and accuracy were obtained. Application to sample of limited availability (e.g. porewaters, snow, rainwater, open ocean water, biological samples) and to the description of high resolution temporal trends may be easily foreseen.