Nanoporous spongelike Au–Ag films for electrochemical epinephrine sensing

Portable electrochemical sensor for adrenaline detection using CoNi-MOF-based CS-PAM hydrogel

The development of a portable smartphone-based electrochemical sensor for analyzing adrenaline levels in real samples can make a great contribution to the research community worldwide. In order to achieve this goal, the key challenge is to build sensing interfaces with excellent electrocatalytic properties. In this work, microspherical bimetallic metal-organic frameworks (CoNi-MOF) consisting of nanoclusters were first synthesized using a hydrothermal method. On this basis, the catalytic activity of pure chitosan-polyacrylamide hydrogel (CS-PAM) was modulated by adding different amounts of CoNi-MOF during the in-situ synthesis of CS-PAM. Finally, a portable electrochemical detection system based on CS-PAM was established for the detection of adrenaline. A series of resulting composite hydrogels with a large specific surface area, abundant active sites, and unique network structure facilitate the enrichment and catalysis of adrenaline molecules. Under optimal conditions, the analytical platform constructed by using CoNi-MOF-based CS-PAM has the advantages of a wide detection range (0.5-10 and 10-2500 μM), a low detection limit (0.167 μM), and high sensitivity (0.182 and 0.133 μA·μM·cm-2). In addition, the sensor maintains selective detection of the target in the presence of many different types of interferences, and the current response is not significantly reduced even after 60 cycles of testing. We strongly believe that the designed smart portable sensing can realize the accurate determination of adrenaline in complex systems, and this study can provide new ideas for the research of MOFs-based hydrogels in electrochemical analysis.

High performance boron doped peroxidase-like nanozyme Cu/B-NC for detection of epinephrine and catalase

Herein, a novel peroxidase-like (POD-like) nanozyme Cu/B-NC was synthesized. The Cu and B co-doped nanozyme Cu/B-NC has competitive POD-like activity but negligible oxidase-like (OXD-like) activity, which is proved to partly benefit from the doping of boron atom. The catalytic activity of Cu/B-NC is high with great affinity for TMB and H2O2 and high reaction velocity. Cu/B-NC was utilized to catalyze the condensation of phenolic substance epinephrine (EP) and 4-aminoantipyrine (4-AAP) to form colored quinone imine in the presence of H2O2. UV-vis absorbance of quinone imine at 492 nm was used for EP determination. Catalase (CAT) could decompose H2O2, so CAT could also be quantified through absorbance variation. The linear ranges of colorimetric detection for EP and CAT were 2-100 μM and 1-30 U mL-1, respectively. The limits of detection (LODs) for EP and CAT were 0.97 μM and 0.57 U mL-1, respectively. The practicability of this sensing platform was further validated by successful application in actual samples.

Voltammetric analysis of epinephrine using glassy carbon electrode modified with nanocomposite prepared from Co-Nd bimetallic nanoparticles, alumina nanoparticles and functionalized multiwalled carbon nanotubes

Herein, we investigated the electrochemical behaviour of fMWCNTs decorated with Co-Nd bimetallic nanoparticles and alumina nanoparticles (Co-Nd/Al2O3@fMWCNTs). The nanocomposites were synthesised using simple mechanical mixing and characterised by FT-IR, XRD, UV-visible studies, SEM, TEM and EDAX. Moreover, the crystalline size of the synthesised nanoparticles was also calculated using XRD data (Debye-Scherer formula) and was found in the nm range. The electrochemical behaviour of epinephrine (EP) was examined in the presence of Co-Nd/Al2O3@fMWCNTs nanocomposite modified glassy carbon electrode (GCE) using various electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronocoulometry. Among all the above-mentioned techniques, the DPV response of the modified Co-Nd/Al2O3@fMWCNTs/GCE under optimal circumstances revealed a dual linear range (0.2 to 4000 µM and 4000 to 14,000 µM) and LOD of 0.015 µM (S/N = 3). The sensitivities were determined to be 0.00323 µAµM-1 and 0.0004 µAµM-1 in 0.2 to 4000 µM and 4000 to 14,000 µM concentration ranges. Using chronocoulometry, the surface coverage of Co-Nd/Al2O3@fMWCNTs/GCE was calculated to be 1.37 × 10-8 mol cm-2. The fabricated Co-Nd/Al2O3@fMWCNTs/GCE demonstrated remarkable repeatability, with an RSD of 0.09%, and storage stability of 3 weeks, with 89.6% current retention. Lastly, it was found that Co-Nd/Al2O3@fMWCNTs/GCE worked well for EP analysis in a variety of biological fluids.

Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry

Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.

Facile synthesis of Pt/polyoxometalate/hollow carbon sphere tri-component nanoparticles via a "double gain strategy" for high-performance electrochemical sensing of adrenaline

In this study, we designed and successfully synthesized the Pt/polyoxometalate/hollow carbon sphere (Pt/POM/HCS) tri-component nanoparticles (NPs) by a pollution-free, efficient, and convenient method. HCSs with outstanding chemical stability and conductivity are self-generated by acid etching and calcination of silica spheres synthesized by a hard template method. HCSs have a hollow internal structure that provides specific three-dimensional storage space, and can increase the surface area. The mesoporous system is beneficial to providing numerous mass transfer passageways and immobilizing NPs. In addition, we introduced a "double gain strategy", by taking advantage of POMs as reducing and bridging agents, to achieve the loading of ultrafine Pt NPs on the surface of HCSs. Pt NPs have excellent stability and unique electrocatalytic activity. As a result of the synergistic effect of HCSs and ultrafine Pt NPs, the electrochemical sensing of adrenaline exhibits high-performance catalytic activity, sensitivity, suitable linearity range (0.16 μM-1.195 mM), and low limit of detection (57.5 nM, S/N = 3), excellent stability, and reproducibility. The developed platform is a sensitive and effective adrenaline electrical sensing platform with broad practical application prospects.

Electrochemistry at Krakowian research institutions

The electrochemistry research team activity from Poland is marked by significant increase in the last 20 years. The joining of European Community in 2004 gives an impulse for the development of Polish science. The development of electrochemistry has been stimulated by cooperation with industry and the establishment of technology transfer centers, technology parks, business incubators, etc. and the mostly by simplified international collaborations. Five research institutions from Krakow reports work in the field of electrochemistry. The achievements of all teams are briefly described.

Recent advances in metal-based nanoporous materials for sensing environmentally-related biomolecules

Highly sensitive, stable, selective, efficient, and short reaction time sensors play a substantial role in daily life/industry and are the need of the day. Due to the rising environmental issues, nanoporous carbon and metal-based materials have attracted significant attention in environmental analysis owing to their intriguing and multifunctional properties and cost-effective and rapid detection of different analytes by sensing applications. Environmental-related issues such as pollution have been a significant threat to the world. Therefore, it is necessary to fabricate highly promising performance-based sensor materials with excellent reliability, selectivity and good sensitivity for monitoring various analytes. In this regard, different methods have been employed to fabricate these sensors comprising metal, metal oxides, metal oxide carbon composites and MOFs leading to the formation of nanoporous metal and carbon composites. These composites have exceptional properties such as large surface area, distinctive porosity, and high conductivity, making them promising candidates for several versatile sensing applications. This review covers recent advances and significant studies in the sensing field of various nanoporous metal and carbon composites. Key challenges and future opportunities in this exciting field are also part of this review.

Electrochemical sensor for the detection of adrenaline at poly(crystal violet) modified electrode: optimization and voltammetric studies

Herein, we report the electropolymerization of crystal violet (CRV) on a bare glassy carbon electrode (GCE) for the detection of adrenaline (AD). Electropolymerization parameters such as electrolyte pH, scan rate and monomer concentrations were optimized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The characterization of CRV and poly(crystal violet) (PCV) was done using FT-IR, UV-visible spectroscopy and EIS. More importantly, the charge transfer resistance (R_ct) and other EIS data recorded from the EIS of various forms of the poly(crystal violet) (PCV) modified glassy carbon electrode (GCE) in AD were used for identifying the best PCV modified electrode. Subsequent application of the electrode prepared at optimum conditions (PGCE) for AD detection using the square wave voltammetry (SWV) gave a limit of detection (LOD) of 2.86 μM over a linear range of 10.3-102.7 μM. This sensor also showed considerable stability, good AD recovery from the real sample (98.9%), and excellent reproducibility, making it a suitable analytical tool for AD detection at the micromolar level.

Promotion Effect of Palladium on BiVO4 Sensing Material for Epinephrine Detection

In this study, the Pd/BiVO4 composite was prepared by hydrothermal method as an electrochemical sensing material for epinephrine. X-ray diffraction, scanning electron microscopy, and a transmission electron microscope were used to characterize the samples. In the electrochemical detection system, cyclic voltammetry and differential pulse voltammetry were applied to measure the concentration of the epinephrine solution (0.9–27.5 µM) with the Pd/BiVO4-coated glassy carbon electrode. As a result, the oxidation peak current of Pd/BiVO4/GCE demonstrated good linearity with the epinephrine concentration. The detection limit of the epinephrine concentration by cyclic voltammetry and differential pulse voltammetry were 0.262 µM and 0.154 µM, respectively. Additionally, the proposed sensing material exhibited good reproducibility, stability, and selectivity. A plausible sensing mechanism was proposed.

A Multifunctional Electrochemical Sensor for the Simultaneous Detection of Ascorbic Acid, Dopamine, Uric Acid, and Nitrite

BACKGROUND

Ascorbic acid (AA), dopamine (DA), uric acid (UA), and nitrite (NO2-) are essential biomarkers for human metabolism and can be used to indicate some chronic diseases and metabolic disorders, including scurvy, Parkinson's disease, hyperuricemia, and kidney disease.

OBJECTIVE

A multifunctional electrochemical sensor that can integrate the detection of these species was constructed using nanoporous gold (NPG) as a recognition element to modify glassy carbon electrode (GCE).

METHODS

The electrochemical performance of the multifunctional electrochemical sensor was investigated toward AA, DA, UA, and NO2- in citrate buffer solution (CBS, 100 mM, pH 4.0) and human serum using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods.

RESULTS

In the quaternary mixture detection, the resulting NPG/GCE electrode displayed four independent oxidation peaks with wide peak separations. Further, the NPG/GCE electrode showed good linear responses with the sensitivities of 32, 1103, 71, and 147 μA/mM/cm2 and the detection limits of 1.58, 0.17, 0.37, and 0.36 μM for AA, DA UA, and NO2-, respectively. Additionally, the NPG/GCE electrode exhibited great anti-interference and was successfully applied in human serum samples.

CONCLUSIONS

These results indicate that the NPG/GCE electrode can simultaneously and selectively detect AA, DA, UA, and NO2-, which has the potential for application and diagnosis in the screening and diagnosis of chronic diseases and metabolic disorders.

HIGHLIGHTS

A multianalyte electrochemical sensor was fabricated for human metabolites detection. The sensor displayed good performance in the simultaneous detection of AA, DA, UA, and NO2- and applied to human serum samples.

"Nano": An Emerging Avenue in Electrochemical Detection of Neurotransmitters

The growing importance of nanomaterials toward the detection of neurotransmitter molecules has been chronicled in this review. Neurotransmitters (NTs) are chemicals that serve as messengers in synaptic transmission and are key players in brain functions. Abnormal levels of NTs are associated with numerous psychotic and neurodegenerative diseases. Therefore, their sensitive and robust detection is of great significance in clinical diagnostics. For more than three decades, electrochemical sensors have made a mark toward clinical detection of NTs. The superiority of these electrochemical sensors lies in their ability to enable sensitive, simple, rapid, and selective determination of analyte molecules while remaining relatively inexpensive. Additionally, these sensors are capable of being integrated in robust, portable, and miniaturized devices to establish point-of-care diagnostic platforms. Nanomaterials have emerged as promising materials with significant implications for electrochemical sensing due to their inherent capability to achieve high surface coverage, superior sensitivity, and rapid response in addition to simple device architecture and miniaturization. Considering the enormous significance of the levels of NTs in biological systems and the advances in sensing ushered in with the integration of nanotechnology in electrochemistry, the analysis of NTs by employing nanomaterials as interface materials in various matrices has emerged as an active area of research. This review explores the advancements made in the field of electrochemical sensors for the sensitive and selective determination of NTs which have been described in the past two decades with a distinctive focus on extremely innovative attributes introduced by nanotechnology.

CuO nanorods as a laccase mimicking enzyme for highly sensitive colorimetric and electrochemical dual biosensor: Application in living cell epinephrine analysis

A sensitive colorimetric and electrochemical sensor for measuring of epinephrine (EP) was developed based on CuO nanorods (NRs), and applicability of the sensor for detection of release epinephrine (EP) from living cells was evaluated. The CuO NRs was prepared using a facile and efficient method in low temperature and characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Energy-dispersive X-ray spectroscopy (EDX). The CuO NRs exhibited laccase-like activity and could oxidize epinephrine (EP) to a colored product. No interference from the common interfering agents such as dopamine, ascorbic acid and uric acid was observed. Colorimetric sensor demonstrated a linear range of 0.6-18 μM with detection limit of 0.31 μM. Furthermore, the electrochemical study showed CuO NRs exhibited excellent electrocatalytic activity towards epinephrine oxidation. Differential pulse voltammetry signals increase with increasing of EP concentration in the range 0.04-14 μM, with a detection limit of 20 nM. Finally, the proposed sensor applied to perform real-time monitoring of epinephrine released by PC12 cells, indicating that CuO NRs provide a new platform for developing high-performance sensors in biological applications.

Solar Exfoliated Graphene Oxide: A Platform for Electrochemical Sensing of Epinephrine

Introduction:

In this study, solar exfoliated graphite oxide modified glassy carbon electrode was used for the anodic oxidation of epinephrine in a phosphate buffer medium at pH7. The modified electrode showed fast response and sensitivity towards Epinephrine Molecule (EP). The electrode was characterized electrochemically through Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). Area of the electrode enhanced three times during modification and studies reveal that the oxidation process of EP occurs by an adsorption controlled process involving two electrons. The results showed a detection limit of 0.50 ± 0.01μM with a linear range up to 100 μM. The rate constant calculated for the electron transfer reaction is 1.35 s-1. The electrode was effective for simultaneous detection of EP in the presence of Ascorbic Acid (AA) and Uric Acid (UA) with well-resolved signals. The sensitivity, selectivity and stability of the sensor were also confirmed.

Methods:

Glassy carbon electrode modified by reduced graphene oxide was used for the detection and quantification of epinephrine using cyclic voltammetry and differential pulse voltammetry.

Results:

The results showed an enhancement in the electrocatalytic oxidation of epinephrine due to the increase in the effective surface area of the modified electrode. The anodic transfer coefficient, detection limit and electron transfer rate constant of the reaction were also calculated.

Conclusion:

The paper reports the determination of epinephrine using reduced graphene oxide modified glassy carbon electrode through CV and DPV. The sensor exhibited excellent reproducibility and repeatability for the detection of epinephrine and also its simultaneous detection of ascorbic acid and uric acid, which coexist in the biological system.

A Facile In-Situ Development of L-Valine Film onto the Surface of Carbon Paste Electrode Towards the Detection of Environmentally Hazardous 4-Amino Phenol

A small scale of environmentally hazardous 4-aminophenol can show significant impact on human health. Hence, in the present work, we have designed L-Valine film (Vf) modified carbon paste electrode (Vf/CPE) for the determination of 4-aminophenol. Herein, a facile in-situ L-Valine film was developed by electrochemical polymerization method onto the surface of bare carbon paste electrode (BCPE) with the help of cyclic voltammetry (CV) technique. A two-folds of electrochemical peak current enhancement was achieved at Vf/CPE in comparison with BCPE towards the determination of 4-aminophenol in optimum pH 7.0 of phosphate buffer solution (PBS). This was achieved due to the large surface area and conductive nature of Vf/CPE, which was concluded through the techniques of cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The effect of pH of buffer and scan rate studies were successfully studied. Morphological changes of BCPE and Vf/CPE was studied with the help of scanning electron microscopy (SEM). The formation of Vf on CPE was also analyzed by Fourier transform infrared (FTIR) spectra. Under the optimized conditions, the limit of detection (LOD) and limit of quantification (LOQ) values of 4-aminophenol were estimated with the aid of chronoamperometry (CA) technique and was found to be 9.8 μM and 32 μM, respectively. Finally the proposed method was found to have satisfactory repeatability, reproducibility and stability results with low relative standard deviation (RSD) values.

Sonochemical synthesis of bismuth(III) oxide decorated reduced graphene oxide nanocomposite for detection of hormone (epinephrine) in human and rat serum

Herein, we report an efficient electrochemical sensor strategy for determination of epinephrine based on Bi₂O₃ nanoparticle decorated reduced graphene oxide nanocomposite (Bi₂O₃@RGO). The Bi₂O₃@RGO was prepared by simple ultrasonic method and then it's morphological and crystal structure aspects were well characterized by physiological instruments. The electrode-electrolyte interfacial properties were examined to ensure the catalytic ability of composite sensing towards EP. The composite was deposited on the multi-conventional screen-printed electrode and was found to be desirable performance toward EP oxidation. The amperometric EP sensing exhibited good reproducible and sensitive which able to detect as low as concentration of 2.14 nM. Furthermore, good reproducibility, long-term stability and repeatability were obtained from the electrode in experiment. Moreover, the EP sensing method was successfully applied in human and rat blood serum, the recoveries were validated by HPLC method. It indicates the reliability of the method in practical analysis.

Nanomaterials-Based Electrochemical Sensors for In Vitro and In Vivo Analyses of Neurotransmitters

Neurotransmitters are molecules that transfer chemical signals between neurons to convey messages for any action conducted by the nervous system. All neurotransmitters are medically important; the detection and analysis of these molecules play vital roles in the diagnosis and treatment of diseases. Among analytical strategies, electrochemical techniques have been identified as simple, inexpensive, and less time-consuming processes. Electrochemical analysis is based on the redox behaviors of neurotransmitters, as well as their metabolites. A variety of electrochemical techniques are available for the detection of biomolecules. However, the development of a sensing platform with high sensitivity and selectivity is challenging, and it has been found to be a bottleneck step in the analysis of neurotransmitters. Nanomaterials-based sensor platforms are fascinating for researchers because of their ability to perform the electrochemical analysis of neurotransmitters due to their improved detection efficacy, and they have been widely reported on for their sensitive detection of epinephrine, dopamine, serotonin, glutamate, acetylcholine, nitric oxide, and purines. The advancement of electroanalytical technologies and the innovation of functional nanomaterials have been assisting greatly in in vivo and in vitro analyses of neurotransmitters, especially for point-of-care clinical applications. In this review, firstly, we focus on the most commonly employed electrochemical analysis techniques, in conjunction with their working principles and abilities for the detection of neurotransmitters. Subsequently, we concentrate on the fabrication and development of nanomaterials-based electrochemical sensors and their advantages over other detection techniques. Finally, we address the challenges and the future outlook in the development of electrochemical sensors for the efficient detection of neurotransmitters.