Electrochemical sensor amplified with cellulose nanofibers/Fe3O4 composite to the monitoring of hydrazine as a pollutant in water and wastewater samples

Advances and Challenges in Molecularly Imprinted Electrochemical Sensors for Application in Environmental, Biomedicine, and Food Safety

Molecularly imprinted electrochemical sensors (MIECSs) are a specialized class of sensors based on molecularly imprinted derivative materials (MIDPs), which have been extensively applied in environmental monitoring, biomedicine, and food safety, allowing for high selectivity and sensitivity in detecting target molecules. This review provides an in-depth exploration of the most innovative and successful nanomaterials employed for modifying imprinted polymers, highlighting their crucial role in enhancing sensor performance, including carbon-based nanomaterials, meal derivatives, magnetic nanomaterials, polymeric and composite nanomaterials. In addition to reviewing advances in derivative materials design, this article delves into the current challenges facing molecularly imprinted sensors, such as issues related to template removal, nonspecific binding, and fabrication reproducibility. These challenges limit the practical application of MIECSs, particularly in complex real-world environments. The review also discusses representative applications of these sensors, including environmental monitoring, biomedicine and food safety, which demonstrate their versatility and potential. Finally, the review outlines future research directions aimed at overcoming these challenges. This includes strategies for improving the stability and reusability of MIECSs, enhancing their selectivity and sensitivity, and developing novel imprinting techniques. By addressing these issues, researchers can pave the way for the next generation of electrochemical sensors, which will be more robust, reliable, and suitable for a wide range of industrial and clinical applications.

Unveiling the Redox Characteristics of Rutin Trihydrate-Canvas-Based Sensor for Hydrazine Sensing in Water Samples

The inclusion of redox mediators into electrocatalytic systems facilitates rapid electron shuttling kinetics and boosts the overall catalytic performance of the electrode. This approach overcomes the sluggish reaction dynamics associated with direct electron transfer, which may be impeded by restricted analyte access to the electrode's active sites. In contrast to conventional synthetic redox mediators, naturally sourced phytomolecule rutin trihydrate (RT), extracted from apple juice, offers potential ecological advantages. This bands with green chemistry principles and sustainability in electroanalytical approaches. The current work presents an eco-friendly and direct electrochemical approach to fabricate a redox-active RT-immobilized MWCNT-infused PEDOT hybrid material-modified glassy carbon electrode (GCE/MWCNT + PEDOT@RT). The developed electrode showcased a sharp and stable redox signal at E0 = 0.63 V vs Ag/AgCl with no surface-fouling characteristics. The efficacious functionalization of RT onto MWCNT + PEDOT was corroborated by a remarkable increase in the surface characteristics, enhanced electrochemical current responses, and low charge transfer resistance. The GCE/MWCNT + PEDOT@RT exhibited highly selective and sensitive sensing responses toward the toxic and potentially carcinogenic hydrazine (HZ) via cyclic voltammetry and differential pulse voltammetry techniques, yielding a low detection limit (DL) of 1.02 μM and a sensitivity of 0.032 μA μM-1 in a linear dynamic range between 0 and 1350 μM. In addition, the method was highly efficient for HZ detection in real samples of tanker, tap, and wastewater samples, producing a good recovery of ∼98%.

Sensitive electrochemical detection of methimazole based on a unique copper and exfoliated graphene oxide nanocomposite

Herein, we report the creation of a novel sensitive electrochemical sensing platform based on a copper and exfoliated graphene oxide (Cu-eGO) nanocomposite using a facile synthesis technique, which simultaneously removes the sodium ions that result from the exfoliation process to generate eGO from graphite. This novel Cu-eGO nanocomposite was characterized via SEM, EDX, Raman and XPS. The Cu-eGO/GCE exhibited much greater activity for the electrochemical oxidation of methimazole than the eGO/GCE or bare GCE. The electrochemical properties and kinetics involved in the oxidation of methimazole at the Cu-eGO were examined using voltammetry and electrochemical impedance spectroscopy (EIS). This Cu-eGO based sensing platform demonstrated high sensitivity at 1.32 μAμM-1cm-2, a low limit of detection at 0.06 μM, robust stability, and strong anti-interference against potential interferents that may exist in biological systems for the detection of methimazole. The developed electrochemical sensor was successfully employed in blood serum samples that mimicked real biological environments, showing its high applicability.

Unveiling carcinogenic pollutant levels in environmental water samples through facile fabrication of gold nanoparticles on sulfur-doped graphitic carbon nitride

Extensive utilization of pesticides and herbicides to boost agricultural production increased the environmental health risks, which can be mitigate with the aid of highly sensitive detection systems. In this study, an electrochemical sensor for monitoring the carcinogenic pesticides in the environmental samples has been developed based on sulfur-doped graphitic-carbon nitride-gold nanoparticles (SCN-AuNPs) nanohybrid. Thermal polycondensation of melamine with thiourea followed by solvent exfoliation via ultrasonication leads to SCN formation and electroless deposition of AuNPs on SCN leads to SCN-AuNPs nanohybrid synthesis. The chemical composition, S-doping, and the morphology of the nanohybrid were confirmed by various microscopic and spectroscopic tools. The as-synthesized nanohybrid was fabricated with glassy carbon (GC) electrode for determining the carcinogenic hydrazine (HZ) and atrazine (ATZ) in field water samples. The present sensor exhibited superior electrocatalytic activity than GC/SCN and GC/AuNPs electrodes due to the synergism between SCN and AuNPs and the amperometric studies showed the good linear range of detection of 20 nM-0.5 mM and 500 nM-0.5 mM with the limit of detection of 0.22 and 69 nM (S/N = 3) and excellent sensitivity of 1173.5 and 13.96 μA mM-1 cm-2 towards HZ and ATZ, respectively. Ultimately, the present sensor is exploited in environmental samples for monitoring HZ and ATZ and the obtained results are validated with high-performance liquid chromatography (HPLC) technique. The excellent recovery percentage and close agreement with the results of HPLC analysis proved the practicability of the present sensor. In addition, the as-prepared materials were utilized for the photocatalytic degradation of ATZ and the SCN-AuNPs nanohybrid exhibited higher photocatalytic activity with the removal efficiency of 93.6% at 90 min. Finally, the degradation mechanism was investigated and discussed.

Hierarchical CoWO4/NixFeyS microspheres bearing crystalline-amorphous interface as a multifunctional platform for outperformed water splitting and sensitive hydrazine sensing

Highly efficient and multifunctional electrocatalysts are of high value in energy transformation and electrochemical sensing. Herein, hierarchically architectured cobalt tungstate/nickel iron sulfide (CoWO4/NixFeyS) microspheres with a crystalline-amorphous interface have been prepared on bimetallic substrate of nickel-iron foam (NIF) by a two-step hydrothermal method. Electrochemical characterization shows that CoWO4/NixFeyS microspheres can boost the electrocatalytic activity effectively through the synergistic effect on the crystalline-amorphous interface. When the CoWO4/NixFeyS is applied as the electrocatalysts for oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), the overpotentials at a high current density of 500 mA cm-2 are only 322.8 mV and 306.5 mV, respectively. The overall water splitting device composed of CoWO4/NixFeyS/NIF couple only needs a cell voltage of 1.80 V to reach a current density of 100 mA cm-2, and 2.19 V to reach 500 mA cm-2. The CoWO4/NixFeyS/NIF can be also utilized as an effective electrochemical platform for the sensing of toxic hydrazine in a wide range from 50 μM to 17.3 mM, with a detection limit of 46.4 μM. All these results display that the CoWO4/NixFeyS/NIF can be a high-performance multifunctional material for energy transformation and environmental pollutant monitoring.

Surface-engineered natural fibers: Emerging alternative substrates for chemical sensor applications: A review

Natural fiber has become one of the most widely used alternative materials for chemical sensor fabrication due to its advantages, such as biocompatibility, flexibility, and self-microfluidic properties. Enhanced natural fiber surface has been used as a substrate in colorimetric and electrochemical sensors. This review focuses on improving the natural fiber properties for preparation as a substrate for chemical sensors. Various methods for natural fiber extraction are discussed and compared. Bleaching and decolorization is important for preparation of colorimetric sensors, while carbonization and nanoparticle doping are favorable for increasing their electrical conductivity for electrochemical sensor fabrication. Also, example fabrications and applications of natural fiber-based chemical sensors for chemical and biomarker detection are discussed. The selectivity of the sensors can be introduced and improved by surface modification of natural fiber, such as enzyme immobilization and biorecognition element functionalization, illustrating the adaptability of natural fiber as a smart sensing device, e.g., wearable and portable sensors. Ultimately, the high performances of natural fiber-based chemical sensors indicate the potential uses of natural fiber as a renewable and eco-friendly substrate material in the field of chemical sensors and biosensors for clinical diagnosis and environmental monitoring.

Electrodeposition of CoFeS nanoflakes on Cu2O nanospheres as an ultrasensitive sensing platform for measurement of the hydrazine and hydrogen peroxide in seawater sample

Nanoarchitectured design of the metal sulfides with highly available surface and abundant electroactive centers and using them as electrocatalyst for fabricate the electrochemical sensors for the detection of hydrazine (N2H4) and hydrogen peroxide (H2O2) is challenging and desirable. Herein, Cu2O nanospheres powder is firstly prepared using chemical reduction of copper chloride and then drop-casted on the glassy carbon electrode (GCE) surface. In the next step, CoFeS nanoflakes are electrodeposited on Cu2O nanospheres by cyclic voltammetry method to form CoFeS/Cu2O nanocomposite as a detection platform for measuring N2H4 and H2O2. Accordingly, Cu2O nanospheres are not only used as substrate, but also guided the CoFeS nanoflakes to adhere to the electrode surface without need to any binder or conductive additive, which enhances the electrical conductivity of the sensing active materials. As the hydrazine sensor, the CoFeS/Cu2O/GCE displayed wide linear ranges (0.0001-0.021 mM and 0.021-1.771 mM), low detection limit (0.12 μM), very high sensitivities (103.33 and 21.23 mA mM-1 cm-2), and excellent selectivity. The as-made nanocomposite also exhibited low detection limit of 1.26 μM for H2O2 sensing with very high sensitivities (12.31 and 3.96 mA mM-1 cm-2) for linear ranges of 0.001-0.03 mM and 0.03-2.03 mM, respectively, and negligible response against interfering substances. The superior analytical performance of the CoFeS/Cu2O for N2H4 electro-oxidation and H2O2 electro-reduction can be attributed to structure stability, high electroactive surface area, and good availability to analyte species and electrolyte diffusion. Moreover, to examine the potency of the prepared nanocomposite in real applications, the seawater sample was analyzed and results display that the CoFeS/Cu2O/GCE can be utilized as a reliable and applicable platform for measuring N2H4 and H2O2.