A novel method to construct a 3D FeWO4 microsphere-array electrode as a non-enzymatic glucose sensor

Multilevel resistive switching in hydrothermally synthesized FeWO4 thin film-based memristive device for non-volatile memory application

The memristors offer significant advantages as a key element in non-volatile and brain-inspired neuromorphic systems because of their salient features such as remarkable endurance, ability to store multiple bits, fast operation speed, and extremely low energy usage. This work reports the resistive switching (RS) characteristics of the hydrothermally synthesized iron tungstate (FeWO4) based thin film memristive device. The detailed physicochemical analysis was investigated using Rietveld's refinement, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques. The fabricated Ag/FWO/FTO memristive device exhibits bipolar resistive switching (BRS) behavior. In addition, the devices exhibit negative differential resistance (NDR) at both positive and negative bias. The charge-flux relation portrayed the non-ideal or memristive nature of the devices. The reliability in the RS process was analyzed in detail using Weibull distribution and time series analysis techniques. The device exhibits stable and multilevel endurance and retention characteristics which demonstrates the suitability of the device for the high-density non-volatile memory application. The current conduction of the device was dominated by Ohmic and trap controlled-space charge limited current (TC-SCLC) mechanisms and filamentary RS process responsible for the BRS in the device. In a nutshell, the present investigations reveal the potential use of the iron tungstate for the fabrication of memristive devices for the non-volatile memory application.

The Fabrication of Halogen-Doped FeWO4 Heterostructure Anchored over Graphene Oxide Nanosheets for the Sunlight-Driven Photocatalytic Degradation of Methylene Blue Dye

Rapid industrialization and urbanization are the two significant issues causing environmental pollution. The polluted water from various industries contains refractory organic materials such as dyes. Heterogeneous photocatalysis using semiconductor metal oxides is an effective remediation technique for wastewater treatment. In this research, we used a co-precipitation-assisted hydrothermal method to synthesize a novel I-FeWO4/GO sunlight-active nanocomposite. Introducing dopant reductive iodine species improved the catalytic activity of FeWO4/GO. I- ions improved the catalytic performance of H2O2 by doping into FeWO4/GO composite. Due to I- doping and the introduction of graphene as a support medium, enhanced charge separation and transfer were observed, which is crucial for efficient heterogeneous surface reactions. Various techniques, like FTIR, SEM-EDX, XRD, and UV-Vis spectroscopy, were used to characterize composites. The Tauc plot method was used to calculate pristine and iodine-doped FeWO4/GO bandgap. Iodine doping reduced the bandgap from 2.8 eV to 2.6 eV. The degradation of methylene blue (MB) was evaluated by optimizing various parameters like catalyst concentration, oxidant dose, pH, and time. The optimum conditions for photocatalysts where maximum degradation occurred were pH = 7 for both FeWO4/GO and I-FeWO4/GO; oxidant dose = 9 mM and 7 mM for FeWO4/GO and I-FeWO4/GO; and catalyst concentration = 30 mg and 35 mg/100 mL for FeWO4/GO and I-FeWO4/GO; the optimum time was 120 min. Under these optimum conditions, FeWO4/GO and I-FeWO4/GO showed 92.0% and 97.0% degradation of MB dye.

Glucose biosensors in clinical practice: principles, limits and perspectives of currently used devices

The demand of glucose monitoring devices and even of updated guidelines for the management of diabetic patients is dramatically increasing due to the progressive rise in the prevalence of diabetes mellitus and the need to prevent its complications. Even though the introduction of the first glucose sensor occurred decades ago, important advances both from the technological and clinical point of view have contributed to a substantial improvement in quality healthcare. This review aims to bring together purely technological and clinical aspects of interest in the field of glucose devices by proposing a roadmap in glucose monitoring and management of patients with diabetes. Also, it prospects other biological fluids to be examined as further options in diabetes care, and suggests, throughout the technology innovation process, future directions to improve the follow-up, treatment, and clinical outcomes of patients.

A facile synthesis of CoMn2O4 nanosheets on reduced graphene oxide for non-enzymatic glucose sensing

A non-enzymatic sensor nanomaterial which is composed of ultra-thin scaly CoMn₂O₄ nanosheets grown on the surface of reduced graphene oxide sheets (CoMn₂O₄ NSs/rGO) has been successfully synthesized by a simple method for glucose sensing. The morphology and elemental composition of CoMn₂O₄ NSs/rGO are researched by means of x-ray diffraction, field emission scanning electron microscope, and transmission electron microscope. Cyclic voltammetry and amperometry are used to analyse the glucose oxidation characteristics of the material. The test results show that the non-enzymatic glucose sensor based on CoMn₂O₄ NSs/rGO has excellent glucose sensing performance, exhibiting a wide linear range of 0.1-30 mM with high sensitivity of 6830.5 μA mM^-1 cm^-2, which is better than other glucose sensors. In addition, the CoMn₂O₄ NSs/rGO sensor has superior anti-interference and stability. More importantly, the sensor can be applied to the measurement of real sample, which makes it have the potential to become a reliable clinical glucose sensor.

In situ deposition of MOF-74(Cu) nanosheet arrays onto carbon cloth to fabricate a sensitive and selective electrocatalytic biosensor and its application for the determination of glucose in human serum

A new electrocatalytic biosensor (MOF-74(Cu) NS-CC) based on the in situ deposition of MOF-74(Cu) nanosheet on carbon cloth via a bottom-up synthetic approach in a glass tube was developed. The electrocatalytic activity of the deposited MOF-74(Cu) NS was demonstrated in the oxidation of glucose to gluconate under alkaline conditions. The results revealed that the proposed method of in situ formation of MOF-74(Cu) NS onto a carbon cloth surface in a multi-layer solution is capable to generate a stable MOF-74(Cu) NS-CC electrode with excellent sensing performance. When the as-synthesized MOF-74(Cu) NS-CC was applied directly as the working electrode for glucose sensing, it showed much higher conductivity and redox activity than MOF-74(Cu) NS-GCE. With the potential applied at 0.55 V (vs. Ag/AgCl), this new electrocatalytic biosensor exhibits an excellent linear relationship between current density and concentration of glucose. Moreover, a wide linear range of detection (1.0 to 1000 μM) was observed. The limit of detection was found to be 0.41 μM (S/N = 3). The response sensitivity is 3.35 mA mM^-1 cm^-2 when the concentration of glucose is in the range 1-100 μM and 3.81 mA mM^-1 cm^-2 for the 100-1000 μM concentration range. This study provides a low-cost, easy to prepare, and reproducible methodology for the synthesis of highly redox-active nanomaterials based on the in situ formation of two-dimensional MOF-74(Cu) NS for the development of new electrocatalytic biosensors. Graphical abstract.

Nonenzymatic Glucose Sensing and Magnetic Property Based On the Composite Formed by Encapsulating Ag Nanoparticles in Cluster-Based Co-MOF

Utilizing the oxygen-bridged 5,5'-oxidiisophthalic acid (H₄L) linker, one Co(II)-based 3D porous MOF {[Co₅(L)₂(OH)₂(OH₂)₂(H₂O)₄]·2DMF·H₂O}_n (1) with pentanuclear [Co₅(μ₃-OH)₂(μ₂-OH₂)₂]⁸⁺ cluster was prepared. The glassy carbon electrode was modified by 1, and the obtained electrode revealed electrocatalytic performance for glucose oxidation. The porous MOF matrix is beneficial for dispersing Ag nanoparticles evenly in the interior cages or channels, so Ag@1 composite composed of both Ag nanoparticles and MOF was further prepared through deposition-reduction method to enhance electrocatalytic activity. The result demonstrates that the glucose oxidation by Ag@1 was greatly increased with low detection limit (1.32 μM) and good selectivity and sensitivity (0.135 μA μM^-1), which promote the application of MOF-template porous composites as advanced electrochemical sensor materials. Furthermore, 1 shows an interesting magnetic spin-glass slow dynamics for the existing of peculiar pentanuclear Co(II) clusters.

Ni–Fe hybrid nanocubes: an efficient electrocatalyst for non-enzymatic glucose sensing with a wide detection range

A sensor for the determination of glucose is developed based on Ni–Fe hybrid nanocubes, which exhibit excellent sensing performance.