Electrochemical Impedance Spectroscopy on 2D Nanomaterial MXene Modified Interfaces: Application as a Characterization and Transducing Tool

Surface-Initiated Reversible Addition-Fragmentation Chain Transfer Polymerization (SI-RAFT) to Produce Molecularly Imprinted Polymers on Graphene Oxide for Electrochemical Sensing of Methylparathion

A nonenzymatic redox-responsive sensor was put forward for the detection of methylparathion (MP) by designing globular nanostructures of molecularly imprinted polymers on graphene oxide (GO@MIPs) via surface-initiated reversible addition-fragmentation chain transfer polymerization (SI-RAFT). Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and small-angle X-ray scattering (SAXS) studies have confirmed the successful formation of receptor layers of MIPs on RAFT agent-functionalized GO sheets. The electrochemical signal with an amplified current response was attained because of the enhanced diffusion rate of ions at the interface provided by widening the pore size of the MIP film. The analytical response of GO@MIPs, validated by recording square-wave anodic stripping voltammetry (SWASV) at varying MP concentrations, followed the linear response between 0.2 and 200 ng/mL. Under optimized conditions, the sensor exhibited a limit of detection of 4.25 ng/mL with high selectivity over other interfering ions or molecules. The anti-interfering ability and good recovery (%) in food samples directed the use of the proposed sensor toward real-time monitoring and also toward future mimicking of surfaces.

Electric-Field-Assisted Synthesis of Cu/MoS2 Nanostructures for Efficient Hydrogen Evolution Reaction

Molybdenum sulfide-oxide (MoS2, MS) emerges as the prime electrocatalyst candidate demonstrating hydrogen evolution reaction (HER) activity comparable to platinum (Pt). This study presents a facile electrochemical approach for fabricating a hybrid copper (Cu)/MoS2 (CMS) nanostructure thin-film electrocatalyst directly onto nickel foam (NF) without a binder or template. The synthesized CMS nanostructures were characterized utilizing energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical methods. The XRD result revealed that the Cu metal coating on MS results in the creation of an extremely crystalline CMS nanostructure with a well-defined interface. The hybrid nanostructures demonstrated higher hydrogen production, attributed to the synergistic interplay of morphology and electron distribution at the interface. The nanostructures displayed a significantly low overpotential of -149 mV at 10 mA cm-2 and a Tafel slope of 117 mV dec-1, indicating enhanced catalytic activity compared to pristine MoS2.This research underscores the significant enhancement of the HER performance and conductivity achieved by CMS, showcasing its potential applications in renewable energy.

MXene-based electrochemical devices applied for healthcare applications

The initial part of the review provides an extensive overview about MXenes as novel and exciting 2D nanomaterials describing their basic physico-chemical features, methods of their synthesis, and possible interfacial modifications and techniques, which could be applied to the characterization of MXenes. Unique physico-chemical parameters of MXenes make them attractive for many practical applications, which are shortly discussed. Use of MXenes for healthcare applications is a hot scientific discipline which is discussed in detail. The article focuses on determination of low molecular weight analytes (metabolites), high molecular weight analytes (DNA/RNA and proteins), or even cells, exosomes, and viruses detected using electrochemical sensors and biosensors. Separate chapters are provided to show the potential of MXene-based devices for determination of cancer biomarkers and as wearable sensors and biosensors for monitoring of a wide range of human activities.

A multifunctional sensor for real-time monitoring and pro-healing of frostbite wounds

Flexible epidermal sensors based on conductive hydrogels hold great promise for various applications, such as wearable electronics and personal healthcare monitoring. However, the integration of conductive hydrogel epidermal sensors into multiple applications remains challenging. In this study, a multifunctional PAAm/PEG/hydrolyzed keratin (Hereinafter referred to as HK)/MXene conductive hydrogel (PPHM hydrogel) was designed as a high-performance therapeutic all-in-one epidermal sensor. This sensor not only accelerates wound healing but also provides wearable human-computer interaction. The developed sensor possesses highly sensitive sensing properties (Gauge Factor = 4.82 at high strain), strong mechanical tensile properties (capable of achieving a maximum elongation at break of 600 %), rapid self-healing capability, stable self-adhesive capability, biocompatibility, freeze resistance at -20 °C, and adjustable photo-thermal conversion capability. This therapeutic all-in-one sensor can sensitively monitor human movements, enabling the detection of small electrophysiological signals for diagnosing relevant activities and diseases. Furthermore, using a rat frostbite model, we demonstrated that the composite hydrogel sensor can serve as an effective wound dressing to accelerate the healing process. This study serves as a valuable reference for the development of multifunctional flexible epidermal sensors for personal smart health monitoring. STATEMENT OF SIGNIFICANCE: Accelerated wound healing reduces the risk of wound infection, and conductive hydrogel-based sensors can monitor physiological signals. The multifunctional application of conductive hydrogel sensors combined with wound diagnostic and therapeutic capabilities can meet personalized medical requirements for wound healing and sensor monitoring. The aim of this study is to develop a multifunctional hydrogel patch. The multifunctional hydrogel can be assembled into a flexible wearable high-performance diagnostic and therapeutic integrated sensor that can effectively accelerate the healing of frostbite wounds and satisfy the real-time monitoring of multi-application scenarios. We expect that this study will inform efforts to integrate wound therapy and sensor monitoring.

A comparative study regarding the adulteration detection of honey: Physicochemical parameters vs. impedimetric data

Honey adulteration is a major issue for European Union and its members because of an unfair practice of different producers and beekeepers, many adulterations involve the addition of sweet, concentrated syrups which may appear like honey. In our study we analysed the influence of adulteration of tilia honey with different syrups (such as corn, rice, inverted sugar, agave, maple syrups) in different percentages (5%, 10%, and 20% respectively) on physicochemical parameters (moisture content, L*, hab,cab, pH, free acidity, electrical conductivity (EC), 5-hydroxymetilfurfural (HMF), fructose, glucose, sucrose, turanose, trehalose, melesitose and raffinose) and impedimetric properties using electrochemical impedance spectroscopy. The impedimetric sensing was made using an electrochemical cell composed of two gold electrodes, and the frequency ranged between 0.1 kHz and 100 kHz. The impedimetric parameters (Z', Z″ and phase) and Randal circuit parameters can distinguish the authentic honeys from the adulterated ones (based on the adulteration agent and adulteration percentage, respectively). The partial least squares - discriminant analysis (PLS-DA) and support vector machines (SVM) were used in a binary mode to separate the authentic honeys from the adulterated ones, and the SVM proved to separate much better than PLS-DA.

Multinary nanocomposite of GO@SrO@CoCrO3@FeCr2O4@SnO2@SiO2 for superior electrochemical performance and water purification applications

Novel multinary nanocomposite using solvothermal method synthesized and studied for their use in supercapacitors and photocatalysis to degrade pollutants using characterization techniques XRD, SEM, EDX, FTIR, Raman, UV-Vis, Zeta potential and photoluminescence spectroscopy whereas electrochemical testing via EIS, CV and GCD analysis. Average crystalline size of 20.81 nm measured from XRD whereas EDX confirms GO suppression within nanocomposite. Mixed matrix like morphology is observable from SEM micrographs. The composite exhibited a band gap of 2.78 eV that could degrade MB dye at 94 % under direct sunlight consistent with first-order kinetics. Multiple distinctive peaks in FTIR spectra indicates various functional groups exsistence in the material alongwith zeta potential value of -17.9 mV. Raman spectra reveals D-band shifting to value 1361 cm-1 while the G-band shifts to 1598 cm-1 relative to GO. Furthermore electrochemical performance evaluated revealing electron transfer rate value 4.88 × 10-9 cms-1 with maximum capacitance about 7182 Fg-1 at a scan rate of 10 mVs-1 respectively. Power density ranges from 3591.18 to 2163 W/kg and energy density from 299 to 120 Wh/Kg as measured from GCD analysis. These findings indicates that novel multinary nanocomposite holds potential as an electrode material in supercapacitors and as a sunlight-driven photocatalyst for the degradation of water-borne organic pollutants.

Fabrication of impedimetric sensor based on metallic nanoparticle for the determination of mesna anticancer drug

Electrochemical impedance spectroscopy (EIS) is a highly effective technique for studying the surface of electrodes in great detail. EIS-based electrochemical sensors have been widely reported, which measure the charge transfer resistance (Rct) of redox probes on electrode surfaces to monitor the binding of target molecules. One of the protective drugs against hemorrhagic cystitis caused by oxazaphosphorine chemotherapy drugs such as ifosfamide, cyclophosphamide and trophosphamide is Mesna (sodium salt of 2-mercaptoethanesulfonate). The increase in the use of Mesna due to the high consumption of anti-cancer drugs, the determination of this drug in biological samples is of particular importance. So far, no electrochemical method has been reported to measure Mesna. In this research, a novel impedimetric sensor based on a glassy carbon electrode (GCE) modified with oxidized multiwalled carbon nanotubes (MWCNTs)/gold nanoparticle (AuNPs) (denoted as Au NPs/MWCNTs/GCE) for impedimetric determination of Mesna anticancer drug was developed. The modified electrode materials were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and EIS. The electrochemical behavior of Mesna at the surface of Au NPs/MWCNTs/GCE was studied by an impedimetric method. The detection mechanism of Mesna using the proposed impedimetric sensor relied on the increase in the Rct value of [Fe (CN)6]3-/4- as an electrochemical probe in the presence of Mesna compared to the absence of Mesna as the analyte. Under the optimum condition, which covered two linear dynamic ranges from 0.06 nmol L-1 to 1.0 nmol L-1 and 1.0 nmol L-1 to 130.0 µmol L-1, respectively. The detection limit was 0.02 nmol L-1. Finally, the performance of the proposed sensor was investigated for Mesna electrochemical detection in biological samples.

Research trends in biomedical applications of two-dimensional nanomaterials over the last decade - A bibliometric analysis

Two-dimensional (2D) nanomaterials with versatile properties have been widely applied in the field of biomedicine. Despite various studies having reviewed the development of biomedical 2D nanomaterials, there is a lack of a study that objectively summarizes and analyzes the research trend of this important field. Here, we employ a series of bibliometric methods to identify the development of the 2D nanomaterial-related biomedical field during the past 10 years from a holistic point of view. First, the annual publication/citation growth, country/institute/author distribution, referenced sources, and research hotspots are identified. Thereafter, based on the objectively identified research hotspots, the contributions of 2D nanomaterials to the various biomedical subfields, including those of biosensing, imaging/therapy, antibacterial treatment, and tissue engineering are carefully explored, by considering the intrinsic properties of the nanomaterials. Finally, prospects and challenges have been discussed to shed light on the future development and clinical translation of 2D nanomaterials. This review provides a novel perspective to identify and further promote the development of 2D nanomaterials in biomedical research.

Reducing the resistance for the use of electrochemical impedance spectroscopy analysis in materials chemistry

Electrochemical impedance spectroscopy (EIS) is a highly applicable electrochemical, analytical, and non-invasive technique for materials characterization, which allows the user to evaluate the impact, efficiency, and magnitude of different components within an electrical circuit at a higher resolution than other common electrochemical techniques such as cyclic voltammetry (CV) or chronoamperometry. EIS can be used to study mechanisms of surface reactions, evaluate kinetics and mass transport, and study the level of corrosion on conductive materials, just to name a few. Therefore, this review demonstrates the scope of physical properties of the materials that can be studied using EIS, such as for characterization of supercapacitors, dye-sensitized solar cells (DSSCs), conductive coatings, sensors, self-assembled monolayers (SAMs), and other materials. This guide was created to support beginner and intermediate level researchers in EIS studies to inspire a wider application of this technique for materials characterization. In this work, we provide a summary of the essential background theory of EIS, including experimental design, signal responses, and instrumentation. Then, we discuss the main graphical representations for EIS data, including a scope of the foundation principles of Nyquist, Bode phase angle, Bode magnitude, capacitance and Randles plots, followed by detailed step-by-step explanations of the corresponding calculations that evolve from these graphs and direct examples from the literature highlighting practical applications of EIS for characterization of different types of materials. In addition, we discuss various applications of EIS technique for materials research.