This tutorial provides the theoretical background, the principles, and applications of Electrochemical Impedance Spectroscopy (EIS) in various research and technological sectors. The text has been ...organized in 17 sections starting with basic knowledge on sinusoidal signals, complex numbers, phasor notation, and transfer functions, continuing with the definition of impedance in electrical circuits, the principles of EIS, the validation of the experimental data, their simulation to equivalent electrical circuits, and ending with practical considerations and selected examples on the utility of EIS to corrosion, energy related applications, and biosensing. A user interactive excel file showing the Nyquist and Bode plots of some model circuits is provided in the Supporting Information. This tutorial aspires to provide the essential background to graduate students working on EIS, as well as to endow the knowledge of senior researchers on various fields where EIS is involved. We also believe that the content of this tutorial will be a useful educational tool for EIS instructors.
This review outlines the theoretical background of impedimetric biosensors and presents different types of impedimetric immunosensors along with the instrumental approaches that have been so far ...proposed in the literature for the evaluation of their performance. The electrode assemblies have been classified in four main categories with respect to the electrode material, the type of the insulating layer and the immobilization platform that have been used for their construction. Additionally, some selected works on recent developments in immunosensors, which are based on polymer degradation phenomena, magnetic nanobeads, etc. as well as strategies for the amplification of the measuring signals, are also presented.
We present in detail the most known and commonly used methods for the calculation of electrode electroactive area (
A
) and heterogeneous electron transfer rate constants (
k
0
). The correct ...procedure for the calculation of these parameters is often disregarded due to either lack of a minimum theoretical background or oversimplification of each method’s limitations and prerequisites. The aim of this work is to provide the theoretical background as well as a detailed guide for the implementation of these measurements by impressing upon the electrochemists the parameters that need to be considered so that the obtained results are safe and useful. Using graphite screen-printed electrodes,
A
, and
k
0
were calculated with different methods and techniques. Data are compared and discussed.
Graphical Abstract
•“Linear” mode 2D-sparking process: Green, liquid free, and fast.•Uniform modification of the whole electrode surface in less than 20 s.•Outstanding resistance to interference by 1000-fold excess of ...dopamine, AA, and UA.•Complete removal of UA facilitates the determination of a few nM 8-OHdG in urine.
The development of sensors for diagnostic purposes is of immense importance. Despite the number of proposed sensors showing attractive detection capabilities, the widespread use of these sensors is mainly hindered by selectivity issues and the elaborate tailoring of the sensing surface that eventually increases both the cost of the final sensor and the individual analysis cost. Herein, we report on the development of an advanced sensor for 8−hydroxy−2ˊ−deoxyguanosine (8−OHdG), an important biomarker for DNA oxidative damage. The sensor was developed on a low-cost graphite screen-printed electrode (SPE) by employing for the first time, an extremely fast SPE-to-graphite “linear” mode sparking process that enables the uniform modification of the whole electrode surface in less than 20 s. Graphite-sparked SPEs exhibited a linear relationship with the concentration of 8−OHdG over the range 2–50 nM, while the limit of detection (3σ) was 0.35 nM. The sensors showed a notable resistance to interference by 1000-fold excess of dopamine and ascorbic acid, and 100-fold excess of uric acid. A simple treatment of the samples, based on uricase, that eliminates the interference caused by uric acid under real-world conditions (>1000-fold excess) was optimized and proposed. The method was successfully applied to the determination of 8−OHdG in synthetic urine samples. Recovery was 95%.
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•Liquid exfoliated Sbene nanosheets and electrochemical passivation of Sbene/SPE.•Cathodic measurements with passivated Sbene/SPE in non-deoxygenated solutions.•In-situ preparation of Sbene ...oxide/PEDOT:PSS nanocomposite via tip sonication.•Advanced detection capabilities of Sbene oxide/PEDOT:PSS/SPE to 4-NT in real samples.
Herein, we present the production of antimonene nanosheets and the in-situ preparation of antimonene oxide/PEDOT:PSS nanocomposite via tip sonication of bulk β-phase antimony in water and aqueous PEDOT:PSS, respectively. Nanomaterials were characterized via SEM, EDX, XRD, FT-IR, electrochemical impedance spectroscopy and cyclic voltammetry, while the resulting modified graphite screen-printed electrodes (Sbene/SPE and Sbene oxide/PEDOT:PSS/SPE, respectively) were evaluated in the cathodic determination of 4-nitrotoluene (4-NT), which was used as a model compound, in the presence of dissolved oxygen and in deoxygenated environments. Data document the electrochemical passivation of Sbene/SPE, which, on the one hand, demonstrate a beneficial poor activity towards the oxygen reduction reaction, and on the other hand, enhanced detection capabilities, thus allowing the determination of 4-NT at the micromolar concentration level at non-deoxygenated solutions. As a result, passivated Sbene/SPE show great promise in sensing applications outside of the laboratory where the deoxygenation of the samples is a big obstacle. Moreover, data demonstrate enhanced detection capabilities for Nafion membrane protected Sbene oxide/PEDOT:PSS/SPE, in deoxygenated solutions, which exhibit a detection range from 50 to 5000 nM 4-NT, while achieving an LOD of 16.7 nM (S/N 3). Nafion membrane is essential for the reusability of the electrodes. Sbene oxide/PEDOT:PSS/SPE was also used to the analysis of a spiked river water sample. Recovery was 97.9%.
This review (with 178 references) focuses on inorganic layered materials (ILMs) and the use of their two-dimensional nanosheets in the development of novel electrochemical (bio)sensors, analytical ...devices, and gas-phase sensing applications. The text is organized in three main sections including the presentation of the most important families of ILMs, a comprehensive outline of various “bottom-up”, “top-down,” and hydro(solvo)thermal methods that have been used for the production of ILM nanosheets, and finally an evaluative survey on their utility for the determination of analytes with interest in different sectors of contemporary analysis. Critical discussion on the effect of the production method on their electronic properties, the suitability of each nanomaterial in different sensing technologies along with an assessment of the performance of the (bio)sensors and devices that have been proposed within the last 5 years, is enclosed. The perspectives of further improving the utility of 2D inorganic nanosheets in sensing applications, in real-world samples, are also discussed.
Graphical abstract
The modification of graphite screen-printed electrodes (SPEs) is reported using an eco-friendly and extremely fast method based on the direct cobalt pin electrode-to-SPE spark discharge at ambient ...conditions. This approach does not utilize any liquids or chemical templates, does not produce any waste, and allows the
in-situ
generation of Co
x
O
y
nanoparticles onto the electrode surface and the development of efficient electrocatalytic sensing surfaces for the determination of H
2
O
2
. Co-spark SPEs were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy (XPS), revealing the formation of surface confined Co
x
O
y
nanoparticles and the diverse oxidation states of cobalt species. Co-spark SPEs were also characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Redox transitions of the surface confined electrocatalysts are demonstrated by electrochemical polarization studies, showing the formation of different oxides (Co
x
O
y
), varying the XPS results. Amperometric measurements at 0.3 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of H
2
O
2
over the range 1 − 102 μM, achieving a limit of detection (3σ/m) of 0.6 μM. The interference effect of various electroactive species was effectively addressed by employing dual measurements in the absence and presence of the enzyme catalase. The analytical utility of the method was evaluated in antioxidant rich real-world samples, such as energy drinks, demonstrating sufficient recovery.
Graphical Abstract
Medical diagnostic sector is relying on affordable, handheld devices integrating smart biosensing and transducing interfaces that enable clinical analysis with minimal end-user intervention and ...resource requirements. In response, we propose here, a SIM card-type pH responsive polymer-modified paper-based biosensing device, coupled to a smartphone, for the determination of urinary creatinine. A vertical microfluidic channel was fabricated on a paper strip by wax printing. The hydrophilic area was coated by a poly(methylmethacrylate)/poly(methacrylic acid) random copolymer, PMMA-co-PMAA, and on top of it, creatinine deiminase (CD) was immobilized. Data demonstrated, on the one hand, zero vertical flow of urine through the enzyme-free PMMA-co-PMAA-modified paper strip, i.e., a high selectivity against the components of the matrix, and on the other hand, in the presence of CD, a creatinine -concentration dependent commence of sample’s downward flow due to the selective, creatinine-triggered degradation of the copolymer by the enzymatically produced ammonia. This CD/PMMA-co-PMAA paper-based biosensing smart assembly is coupled with three conductive strips, which enable the automatic on/off (sample addition/measurement end) measurement of the copolymer degradation time, through electric resistance measurements. It also features an in-built sample well and wireless communication support through the integration of a Bluetooth® microprocessor incorporated with time and resistance measuring circuits. Using newly synthesized pH responsive PMMA-co-PMAA at different molecular weights and volume fraction ratios offering tunable dissolution properties, the detection range was adjusted over 3–30 mM creatinine to overspread the normal range of creatinine in urine. The device was successfully applied to the determination of urinary creatinine.
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