Functionalization of Carbon Nanofibers with an Aromatic Diamine: Toward a Simple Electrochemical-Based Sensing Platform for the Selective Sensing of Glucose

Despite a variety of glucose sensors being available today, the development of nonenzymatic devices for the determination of this biologically relevant analyte is still of particular interest in several applicative sectors. Here, we report the development of an impedimetric, enzyme-free electrochemical glucose sensor based on carbon nanofibers (CNFs) functionalized with an aromatic diamine via a simple wet chemistry functionalization. The electrochemical performance of the chemically modified carbon-based screen-printed electrodes (SPCEs) was evaluated by electrical impedance spectroscopy (EIS), demonstrating a high selectivity of the sensor for glucose with respect to other sugars, such as fructose and sucrose. The sensing parameters to obtain a reliable calibration curve and the selective glucose sensing mechanism are discussed here, highlighting the performance of this novel electrochemical sensor for the selective sensing of this important analyte. Two linear trends were noted, one at low concentrations (0-1200 μM) and the other from 1200 to 5000 μM. The limit of detection (LOD), calculated as the (standard error/slope)*3.3, was 18.64 μM. The results of this study highlight the performance of the developed novel electrochemical sensor for the selective sensing of glucose.

Green Synthesis of PtPdNiFeCu High-Entropy Alloy Nanoparticles for Glucose Detection

High-entropy alloys have long been used as a new type of alloy material and have attracted widespread concern because of their excellent performance, including their stable microstructure and particular catalytic properties. To design a safer preparation method, we report a novel approach targeting green synthesis, using tea polyphenols to prepare PtPdNiFeCu high-entropy alloy nanoparticles for glucose detection. The fabricated sensors were characterized by transmission electron microscopy and electrochemical experiments. Physical characterization showed that the nanoparticle has better dispersibility, and the average particle size is 7.5 nm. The electrochemical results showed that Tp-PtPdNiFeCu HEA-NPs had a high sensitivity of 1.264 μA mM-1 cm-2, a low detection limit of 4.503 μM, and a wide detection range of 0 - 10 mM. In addition, the sensor has better stability and selectivity for glucose detection.

Direct decoration of commercial cotton fabrics by binary nickel-cobalt metal-organic frameworks for flexible glucose sensing in next-generation wearable sensors

Having a prime significance in diagonsing and predicting the dangerous symptoms of chronic diseases in the early stages, special attention has been drawn by wearable glucose-sensing platforms in recent years. Herein, modified commercial cotton fabrics, decorated with binary Ni-Co metal-organic frameworks (NC-MOFs) through a one-pot scalable hydrothermal route, were directly utilized as flexible electrodes for non-enzymatic glucose amperometric sensing. Glucose sensitivities of 105.2 μA mM^-1 cm^-2 and 23 μA mM^-1 cm^-2 were acheived within two distinct linear dynamic ranges of 0.04-3.13 mM and 3.63-8.28 mM, respectively. Receiving benefits from a remarkable glucose sensitivity behavior in co-existence of iso-structures and interferences, rapid response (4.2 s), and remarkable reproducibility and repeatability, NC-MOF-modified cotton fabric electrodes are imensilly promising for developing high-performance wearable glucose sensing platfroms. The sensing performance of fabricated electrodes was further investigated in human blood serum and saliva.

Construction of a binder-free non-enzymatic glucose sensor based on Cu@Ni core-shell nanoparticles anchored on 3D chiral carbon nanocoils-nickel foam hierarchical scaffold

Bimetallic nanostructures composited with carbonaceous materials are the potential contenders for quantitative glucose measurement owing to their unique nanostructures, high biomimetic activity, synergistic effects, good conductivity and chemical stability. In the present work, chemical vapors deposition technique has been employed to grow 3D carbon nanocoils (CNCs) with a chiral morphology on hierarchical macroporous nickel foam (NF) to get a CNCs/NF scaffold. Following, bimetallic Cu@Ni core-shell nanoparticles (CSNPs) are effectively coupled with this scaffold through a facile solvothermal route in order to fabricate a binder-free novel Cu@Ni CSNPs/CNCs/NF hybrid nanostructure. The constructed free-standing 3D hierarchical composite electrode guarantees highly efficient glucose redox activity due to core-shell synergistic effects, enhanced electrochemical active surface area, excellent electrochemical stability, improved conductivity with better ion diffusivity and accelerated reaction kinetics. Being a non-enzymatic glucose sensor, this electrode achieves highly swift response time of 0.1 s, ultra-high sensitivity of 6905 μA mM^-1 cm^-2, low limit of detection of 0.03 μM along with potential selectivity and good storage stability. Moreover, the proposed sensor is also tested successfully for the determination of glucose concentration in human serum samples under good recovery ranging from 96.6 to 102.1 %. The 3D Cu@Ni CSNPs/CNCs/NF composite electrode with unprecedented catalytic performance can be utilized as an ideal biomimetic catalyst in the field of non-enzymatic glucose sensing.

Non-Enzymatic Glucose Sensors Involving Copper: An Electrochemical Perspective

Non-enzymatic glucose sensors based on the use of copper and its oxides have emerged as promising candidates to replace enzymatic glucose sensors owing to their stability, ease of fabrication, and superior sensitivity. This review explains the theories of the mechanism of glucose oxidation on copper transition metal electrodes. It also presents an overview on the development of among the best non-enzymatic copper-based glucose sensors in the past 10 years. A brief description of methods, interesting findings, and important performance parameters are provided to inspire the reader and researcher to create new improvements in sensor design. Finally, several important considerations that pertain to the nano-structuring of the electrode surface is provided.

Electrochemical Detection of Imidacloprid Using Cu-rGO Composite Nanofibers Modified Glassy Carbon Electrode

The fabrication of electrochemical sensor for the ultra-low-level detection and quantification of Imidacloprid (IMD) in soil is one of the major challenges in real-time analysis. Herein, a three-electrode system for sensing IMD at low levels has been developed using Cu-rGO nanofiber composite modified glassy carbon working electrode, Ag/AgCl reference and platinum wire counter electrodes. In the presence of IMD, a significant enhancement in voltammetric current responses were observed at 0.506, 0.375 and 0.181 V due to [Formula: see text] redox complexes. The developed sensor exhibited sensitivity of 0.325 µA µM^-1 with the limit of detection, quantification and repeatability of 2.511 nM, 7.533 nM and 0.28 RSD% respectively. The fabricated sensor could detect IMD with swift response time of less than 5 s. Further, the fabricated electrode was successfully employed to quantify the levels of IMD in soil samples and the results are reported.

Novel bimetallic Cu/Ni core-shell NPs and nitrogen doped GQDs composites applied in glucose in vitro detection

In present work, a highly sensitive biosensor with high selectivity for glucose monitoring is developed based on novel nano-composites of nitrogen doped graphene quantum dots (N-GQDs) and a novel bimetallic Cu/Ni core-shell nanoparticles (CSNPs) (Cu@Ni CSNPs/N-GQDs NCs). With the tuned electronic properties, N-GQDs helped bimetallic core-shell structure nanomaterials from aggregation, and separate the charges generated at the interface. This novel nano-composites also have the good electrical conductivity of N-GQDs, catalyst property of Cu/Ni bimetallic nano composite, Cu@Ni core-shell structure and the synergistic effect of the interaction between bimetallic nano composite and N-GQDs. While modified the electrode with this novel nano-composites, the sensor' linear range is 0.09 ~ 1 mM, and the limit of detection (LOD) is 1.5 μM (S/N = 3) with a high sensitivity of 660 μA mM-1 cm-2, and rapid response time (3 s). Its' LOD is more than 74 times lower than the traditional Cu@Ni CSNPs modified working electrode. It also has higher sensitivity and wider linear range. This indicates the great potential of applying this kind of nano composites in electrode modification.

Direct Immobilization of Biomolecules through Magnetic Forces on Ni Electrodes via Ni Nanoparticles: Applications in Electrochemical Biosensors

The present work describes a new simple procedure for the direct immobilization of biomolecules on Ni electrodes using magnetic Ni nanoparticles (NiNPs) as biomolecule carriers. Ni electrodes were fabricated by electroplating, and NiNPs were chemically synthesized. The chemical composition, crystallinity, and granular size of Ni electrodes, NiNP, and NiNP-modified Ni electrodes (NiNP/Ni) were determined by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of Ni electrodes by cyclic voltammetry and electrochemical impedance spectroscopy confirmed the existence of nickel oxides, hydroxides, and oxohydroxide films at the surface of Ni. Magnetic characterization and micromagnetic simulations were performed in order to prove that the magnetic force is responsible for the immobilization process. Further, Ni electrodes were employed as amperometric sensors for the detection of hydrogen peroxide because it is an important performance indicator for a material to be applied in biosensing. The working principle for magnetic immobilization of the enzyme-functionalized NiNP, without the use of external magnetic sources, was demonstrated for glucose oxidase (GOx) as a model enzyme. XPS results enabled to identify the presence of GOx attached to the NiNP (GOx-NiNP) on Ni electrodes. Finally, glucose detection and quantification were evaluated with the newly developed GOx-NiNP/Ni biosensor by amperometry at different potentials, and control experiments at different electrode materials in the presence and absence of NiNP demonstrated their importance in the biosensor architecture.

Highly Electrocatalytic, Durable, and Stretchable Nanohybrid Fiber for On-Body Sweat Glucose Detection

A conformal patch biosensor that can detect biomolecules is one promising technology for wearable sweat glucose self-monitoring. However, developing such a patch is challenging because conferring stretchability to its components is difficult. Herein, we demonstrate a platform for a nonenzymatic, electrochemical sensor patch: a wrinkled, stretchable, nanohybrid fiber (WSNF) in which Au nanowrinkles partially cover the reduced graphene oxide (rGO)/polyurethane composite fiber. The WSNF has high electrocatalytic activity because of synergetic effects between the Au nanowrinkles and the oxygen-containing functional groups on the rGO-supporting matrix which promote the dehydrogenation step in glucose oxidation. The WSNF offers stretchability, high sensitivity, low detection limit, high selectivity against interferents, and high ambient-condition stability, and it can detect glucose in neutral conditions. If this WSNF sensor patch were sewn onto a stretchable fabric and attached to the human body, it could continuously measure glucose levels in sweat to accurately reflect blood glucose levels.

A non-enzymatic glucose sensor based on a CoNi2Se4/rGO nanocomposite with ultrahigh sensitivity at low working potential

A CoNi₂Se₄–rGO nanocomposite fabricated on Ni foam shows excellent efficiency for non-enzymatic glucose sensing at low applied potential.