Synthesis of a three-dimensional porous Co3O4 network interconnected by MWCNTs and decorated with Au nanoparticles for enhanced nonenzymatic glucose sensing

A review of zeolitic imidazolate frameworks (ZIFs) as electrochemical sensors for important small biomolecules in human body fluids

Small biomolecules play a critical role in the fundamental processes that sustain life and are essential for the proper functioning of the human body. The detection of small biomolecules has garnered significant interest in various fields, including disease diagnosis and medicine. Electrochemical techniques are commonly employed in the detection of critical biomolecules through the principle of redox reactions. It is also a very convenient, cheap, simple, fast, and accurate measurement method in analytical chemistry. Zeolitic imidazolate frameworks (ZIFs) are a unique type of metal-organic framework (MOF) composed of porous crystals with extended three-dimensional structures. These frameworks are made up of metal ions and imidazolate linkers, which form a highly porous and stable structure. In addition to their many advantages in other applications, ZIFs have emerged as promising candidates for electrochemical sensors. Their large surface area, pore diameter, and stability make them ideal for use in sensing applications, particularly in the detection of small molecules and ions. This review summarizes the critical role of small biomolecules in the human body, the standard features of electrochemical analysis, and the utilization of various types of ZIF materials (including carbon composites, metal-based composites, ZIF polymer materials, and ZIF-derived materials) for the detection of important small biomolecules in human body fluids. Lastly, we provide an overview of the current status, challenges, and future outlook for research on ZIF materials.

Growth of nanostructured Cu3Al alloy films by magnetron sputtering for non-enzymatic glucose-sensing applications

Enzymatic glucose sensors usually exhibit excellent sensitivity and selectivity but suffer from poor stability due to the negative influence of temperature and humidity on enzyme molecules. As compared to enzymatic glucose sensors, non-enzymatic counterparts are generally more stable but are facing challenges in concurrently improving both sensitivity and selectivity of a trace amount of glucose molecules in physiological samples such as saliva and sweat. Here, a novel non-enzymatic glucose sensor based on nanostructured Cu₃Al alloy films has been fabricated by a facile magnetron-sputtering followed by controllable electrochemical etching approach. Since the metal Al is more reductive than Cu, by selectively etching aluminum in the Cu₃Al alloys, nanostructured alloy films were obtained with increased surface contact area and electrocatalytic active sites which resulted in enhanced glucose-sensing performance. Thus, non-enzymatic glucose sensors based on nanostructured Cu₃Al alloy films not only exhibited a high sensitivity of 1680 μA mM^-1 cm^-2 but also achieved a reliable selectivity to glucose without interference by other species in physiological samples. Consequently, this study sparked the potential for the development of non-enzymatic biosensors for the continuous monitoring of blood glucose levels with high sensitivity and impressive selectivity for glucose molecules.

3D-Structured Au(NiMo)/Ti Catalysts for the Electrooxidation of Glucose

In this study, 3D-structured NiMo coatings have been constructed via the widely used electrodeposition method on a Ti surface and decorated with very small Au crystallites by galvanic displacement (Au(NiMo)/Ti). The catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma optical emission spectroscopy. Different Au(NiMo)/Ti catalysts, which had Au loadings of 1.8, 2.3, and 3.9 µgAu cm−2, were prepared. The electrocatalytic activity of the Au(NiMo)/Ti catalysts was examined with respect to the oxidation of glucose in alkaline media by cyclic voltammetry. It was found that the Au(NiMo)/Ti catalysts with Au loadings in the range of 1.8 up to 3.9 µgAu cm−2 had a higher activity compared to that of NiMo/Ti. A direct glucose-hydrogen peroxide (C6H12O6-H2O2) single fuel cell was constructed with the different Au-loading-containing Au(NiMo)/Ti catalysts as the anode and Pt as the cathode. The fuel cells exhibited an open circuit voltage of ca. 1.0 V and peak power densities up to 8.75 mW cm−2 at 25 °C. The highest specific peak power densities of 2.24 mW µgAu−1 at 25 °C were attained using the Au(NiMo)/Ti catalyst with the Au loading of 3.9 µg cm−2 as the anode.

Green Fabrication of Nonenzymatic Glucose Sensor Using Multi-Walled Carbon Nanotubes Decorated with Copper (II) Oxide Nanoparticles for Tear Fluid Analysis

In this report, a green, simple, inexpensive, and effective nonenzymatic electrochemical glucose sensor was fabricated using multi-walled carbon nanotubes (MWCNT) decorated with copper (II) oxide nanoparticles (CuO NPs). Basil seed mucilage (BSM) was served as reducing, capping, and stabilizing agents in the synthesis of CuO NPs.The prepared MWCNT/CuO nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and electrochemical methods. The FTIR results indicated that the nanocomposite surface was covered by BSM. The FESEM results show that the CuO NPs with an average particle size lower than 10 nm have been well distributed on the walls of the MWCNT. The electrochemical behavior of the nanocomposite was explored by studying the electrocatalytic behavior of the screen-printed carbon electrode (SPCE) modified by the nanocomposite (SPCE-MWCNT/CuO) toward the glucose oxidation. In the optimum conditions, the electrode indicated a wide linear response from 5.0 to 620.0 μM with regression coefficients of 0.992, the sensitivity of 1050 μA mM^-1 cm^-2, a limit of detection (LOD) of 1.7 μM, and a reproducibility with relative standard deviation (RSD) variations from 3.5 to 11% for three measurements at each point. The obtained results also showed good selectivity to glucose against interfering species such as lactate (LA), L-ascorbic acid (AA), and urea (U) due to the use of the negatively charged BSM in the form of a coating on the nanocomposite surface. The applicability of the sensor was successfully verified by the determination of glucose concentration in artificial tears with a certain amount of glucose.

Constructing epitaxially grown heterointerface of metal nanoparticles and manganese dioxide anode for high-capacity and high-rate lithium-ion batteries

Low ion migration rate and irreversible change in the valence state in transition-metal oxides limit their application as anode materials in Li-ion batteries (LIBs). Interfacial optimization by loading metal particles on semiconductor can change the band structure and thus tune the inherent electrical nature of transition-metal oxide anode materials for energy applications. In this work, Au nanoparticles are epitaxially grown on MnO₂ nanoroads (MnO₂-Au). Interestingly, the MnO₂-Au anode shows excellent electrochemical activity. It delivers high reversible capacity (about 2-3 fold compared to MnO₂) and high rate capability (740 mA h g^-1 at 1 A g^-1). The electron holography and density functional theory (DFT) results demonstrate that the Au particles on the surface of MnO₂ can form a negative charge accumulation area, which not only improves the Li ion migration rate but also catalyzes the transition of MnO_x to Mn⁰. This study provides a direction to heterointerface fabrication for transition-metal oxide anode materials with desired properties for high-performance LIBs and future energy applications.