Sensitive Glucose Sensor Research Articles

Highly Sensitive Glucose Sensors Based on Gated Graphene Microwave Waveguides

AbstractA novel approach is demonstrated to identify glucose concentration in aqueous solutions based on the combined effect of its frequency‐dependent interaction with microwaves propagating in graphene channels and the modification of graphene radio frequency (RF) conductivity caused by physisorbed molecules. This approach combines broadband microwave sensing and chemical field effect transistor sensing in a single device, leading to information‐rich, multidimensional datasets in the form of scattering parameters. A sensitivity of 7.30 dB(mg/L)−1 is achieved, significantly higher than metallic state‐of‐the‐art RF sensors. Different machine learning methods are applied to the raw, multidimensional datasets to infer concentrations of the analyte, without the need for parasitic effect removals via de‐embedding or circuit modeling, and a classification accuracy of 100% is achieved for aqueous glucose solutions with a concentration variation of 0.09 mgL−1.

Development of Highly Sensitive and Selective Electrochemical Glucose Sensors Based on the Modification of the Surface, Structural, and Morphological Properties of ZnO Using Vitamin-B Complexes

Non-enzymatic electrochemical glucose sensors are particularly advantageous because of their simplicity, low cost, efficiency, and long storage life. ZnO structures were modified with water-soluble vitamin B12, B9, and B6 complexes in alkaline 0.1 M NaOH solutions to enhance glucose sensing. ZnO samples were hydrothermally synthesized using 5 mg fixed masses of B12, B9, and B6 complexes. X-ray diffraction, scanning electron microscopy, UV-visible spectrometry, and Fourier transform infrared spectroscopy were used to determine crystalline properties, morphology, and optical band gap. Zinc oxide obtained from vitamin B complexes had a hexagonal structure similar to wurtzite, modified nanorods on its surface, and a reduced optical band gap. The molecular weight, size, and number of functional groups vitamins also influenced surface and structural characteristics of ZnO. Zinc oxide from the B12 complex proved excellent for non-enzymatic glucose sensing in alkaline conditions. B12-derived ZnO glucose sensors have a linear range of 0.1 to 10 mM with a detection limit of 0.005 mM. In the glucose sensing process, a satisfactory level of stability, reproducibility, and selectivity was observed. Furthermore, it was found that ZnO derived from B12 had a high electrical conductivity, which facilitated electron transfer during glucose oxidation.

Gold nanourchin on multiple-point dielectrode for glucose biosensing by current-potential measurement.

Gestational diabetes (GD) is a condition characterized by elevated blood sugar levels during pregnancy. GD poses various health risks, such as serious birth injuries, the need for cesarean delivery, and the necessity of newborn care. Monitoring glucose levels is essential for ensuring safe delivery and reducing the risks to both the mother and fetus. Various sensors are readily available for monitoring glucose levels, and researchers are continually working to develop highly sensitive glucose sensors. This research aimed to develop a gold nanourchin (AuNU)-hybrid biosensor for quantifying glucose on a multi-point electrode sensor. Glucose oxidase (GOx) was attached to the AuNU and seeded on the sensing surface using an amine linker. The current-potential (1-2V at 0.1V sweep) was recorded for the GOx-glucose interaction, with a limit of detection of 560μM and a regression coefficient (R2) of 0.9743 [y = 0.9106x - 0.9953] on the linear curve. The sensitivity was estimated to be 3.5mAcm-2M-1. Furthermore, control experiments with galactose, sucrose, and fructose did not yield an increase in current-potential, confirming specific glucose detection. This experiment helps in monitoring glucose levels to manage conditions associated with GD.

Fabrication of flexible glucose sensor based on heterostructure ZnO nanosheets decorated PU/Chitosan-PANI hybrid nanofiber

Designing and fabrication of immensely accurate, affordable, sensitive, and portable glucose sensors is rapidly increasing in clinical applications. However, commercialization of wearable sensors has been impeded by inadequate conductivity, insufficient durability, poor flexibility, and enzyme immobilization. Herein, a scalable approach for fabricating a nanofiber-based highly electroactive, flexible, and disposable (PUC-PANI-ZnO@GOx) sensor that can assess glucose stimuli with sufficient liquid permeability by anchoring ZnO nanosheets over polyaniline (PANI) coated polyurethane-chitosan (PU-Chitosan; PUC) fibrous mat followed by glucose oxidase (GOx) immobilization is described. Regarding the electrocatalytic performance, PUC-PANI-ZnO@GOx sensor showed a high sensitivity (∼998.72 µA mM−1 cm−2) and a low detection limit (∼7.31 µM) for a broad linear range of 0.01 – 9.48 mM with acceptable stability and reproducibility. The fabricated sensor was highly selective towards glucose in the presence of exogenous and endogenous interfering species. To the best of our knowledge, this novel polymer-based nanocomposite adorned on nanofiber substrate was utilized for the first time for the fabrication of a flexible glucose sensor. It can be used for producing a large-scale, cost-effective, and high-performing sensor. Hence, this sustainable and eco-friendly approach can lead to new techniques for designing next-generation wearable and implantable glucose sensors.

Surface engineered metal-organic framework-based electrochemical biosensors for enzyme-mimic ultrasensitive detection of glucose: recent advancements and future perspectives.

Metal-Organic Frameworks (MOFs) have garnered significant attention in the development of electrochemical glucose sensors due to their unique and advantageous properties. The highly tunable pore channels of MOFs facilitate optimal diffusion of glucose molecules, while their large specific surface area provides abundant active sites for electrochemical reactions. Furthermore, the well-dispersed metallic active sites within MOFs enhance electrocatalytic activity, thereby improving the sensitivity and selectivity of glucose detection. These features make MOF-based nanoarchitectures promising candidates for the development of efficient and sensitive glucose sensors, which are crucial for diabetes management and monitoring. The integration of enzymatic biosensors with nanotechnology continues to drive advancements in glucose monitoring, offering the potential for more accurate, convenient, and user-friendly tools for diabetes management. Current research explores non-invasive glucose monitoring methods, such as using sweat, saliva, or interstitial fluid instead of blood, aiming to reduce the discomfort and inconvenience associated with frequent blood sampling. A review of the advancements and applications of MOF-based enzyme-mimic electrochemical sensors for glucose monitoring can provide valuable insights for young researchers, inspiring future research in biomedical device fabrication. Such reviews not only offer a comprehensive understanding of the current state of the art but also highlight existing challenges and future opportunities in the field of enzyme-less glucose sensing, particularly in the surface modification techniques of highly porous MOFs. This fosters innovation and new research directions. By understanding the advantages, challenges, and opportunities, researchers can contribute to the development of more effective and innovative enzyme-mimic glucose sensing transducers, which are essential for advancing biomedical devices.

Selective and sensitive non-enzymatic detection of glucose by Cu(ii)–Ni(ii)/SBA-15

Monitoring blood glucose levels in diabetic patients is vital, pressing the need for sensitive and affordable glucose sensors.

From small changes to big gains: pyridinium-based tetralactam macrocycle for enhanced sugar recognition in water.

The complex distribution of functional groups in carbohydrates, coupled with their strong solvation in water, makes them challenging targets for synthetic receptors. Despite extensive research into various molecular frameworks, most synthetic carbohydrate receptors have exhibited low affinities, and their interactions with sugars in aqueous environments remain poorly understood. In this work, we present a simple pyridinium-based hydrogen-bonding receptor derived from a subtle structural modification of a well-known tetralactam macrocycle. This small structural change resulted in a dramatic enhancement of glucose binding affinity, increasing from 56 M-1 to 3001 M-1. Remarkably, the performance of our synthetic lectin surpasses that of the natural lectin, concanavalin A, by over fivefold. X-ray crystallography of the macrocycle-glucose complex reveals a distinctive hydrogen bonding pattern, which allows for a larger surface overlap between the receptor and glucose, contributing to the enhanced affinity. Furthermore, this receptor possesses allosteric binding sites, which involve chloride binding and trigger receptor aggregation. This unique allosteric process reveals the critical role of structural flexibility in this hydrogen-bonding receptor for the effective recognition of sugars. We also demonstrate the potential of this synthetic lectin as a highly sensitive glucose sensor in aqueous solutions.

Non-enzymatic glucose electrochemical sensor based on nitrogen-doped graphene modified with polyaniline and Fe3O4@MIL-101-NH2 nano framework

In this study, a novel highly sensitive and selective non-enzymatic glucose sensor was fabricated by coating simple and cheap graphite sheet (GS) electrodes with a proper conductive nanocomposite containing nitrogen-doped functionalized graphene (NFG), conductive polyaniline (PANI), and core–shell nanoparticles (Fe3O4@MIL-101-NH2). The results revealed that the core centers of iron oxide nanoparticles shelled by MIL-101-NH2 enhanced the electron transfer and led to more conductivity, also their existence caused the limitation of the MOF’s low conductivity. In addition, using Fe3O4@MIL-101-NH2 in the nanocomposite structure led to more sensitivity and selectivity at glucose monitoring due to its amine groups and unique structure. The results showed that NFG/PANI/Fe3O4@MIL-101-NH2 nanocomposite provided a large surface area besides enhanced electron transfer and catalytic properties that lead to proper oxidation of glucose with two linear ranges of 0.5 – 10 µM and 100 µM – 25 mM and a low detection limit of 0.3 µM (S/N = 3). Furthermore, the relative standard deviation (RSD%) in all detection processes was lower than 9 %. Finally, the performance of fabricated non-enzymatic sensor (GS/NFG/PANI/Fe3O4@MIL-101-NH2) in human fluids real samples including serum and plasma was acceptable which significantly indicates that it is toward monitoring of glucose in clinical applications.

Ni/NiO/carbon derived from covalent organic frameworks for enzymatic-free electrochemical glucose sensor

An electrochemical enzyme-free glucose sensor based on a novel material with high catalytic performance was constructed. Specifically, a covalent-organic framework (COFBD) with abundant O,N,O′-metal chelating sites was firstly grown on the surface of SiO2 sacrificial template and then coordinated with Ni2+. Finally, Ni/NiO/cellular carbon foam (Ni/NiO/NC) nanocomposite was obtained by carbonizing the above material and removing the SiO2 template through NaOH etching. The electrocatalytic performance of Ni/NiO/NC could be adjusted by cavity size of NC and size of Ni/NiO nanoparticles. The enzyme-free glucose sensor based on Ni/NiO/NC showed a low detection limit of 0.2 μM, a wide detection range of 0.6 μM–8.6 mM and a high sensitivity of 76.03 μA mM−1 cm−2. Moreover, the paper-based wearable glucose sensor was also implemented and the results exhibited that the detection limit was 0.4 μM, the linear range was 1.1 μM–5.2 mM and the sensitivity was 42.38 μA mM−1 cm−2. The electrochemical enzyme-free glucose sensor also showed outstanding practical application performance for detection of glucose in real samples of juice, human serum and sweat. The works provided a method to construct novel material with good catalytic performance for sensitive glucose sensor.

A sensitive, selective non-enzymatic electrochemical detection and kinetic study of glucose over Pt nanoparticles/SWCNTs/NiO ternary nanocomposite

BackgroundThe coupling of inorganic metal nanoparticles, semiconductor-based metal oxide nanostructures, and carbon nanomaterials is a promising strategy to fabricate efficient electrochemical sensors. Herein, we successfully designed a sensitive and selective electrochemical glucose sensor using Pt nanoparticles (PtNPs) decorated single-wall carbon nanotubes (SWCNTs) and nickel oxide (NiO) nanostructure-based composite materials. MethodsThe nanocomposite was synthesized without applying any dispersant or stabilizer using simple ultrasonication and photo-reduction techniques. Significant findingsThe morphology of nanocomposite reveals a homogenous dispersion of CNTs and PtNPs over the NiO nanostructure. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that the ternary nanocomposite-modified glassy carbon electrode (Pt@CNTs/NiO/GCE) displayed enhanced catalytic activity compared to CNTs/NiO/GCE, NiO/GCE or bare GGE electrodes. Kinetics studies indicated that the glucose electrooxidation using Pt@CNTs/NiO modified GCE followed irreversible diffusion-controlled kinetics with a transfer co-efficient value (α) ≈ 0.50. Amperometric sensing investigation revealed excellent sensitivity (149.36 µA mM−1 cm−2) and a lower limit of detection value (2.16 µM). The currently fabricated sensor electrode showed appropriate selectivity in the presence of various organic and inorganic species with outstanding repeatability, reproducibility, and sensor stability. The newly fabricated nanocomposite can represent a promising electro-catalyst for the efficient sensing of glucose and other biomolecules by the electrochemical approach.

Mn incorporation boosted NiO nanosheets as highly efficient anode for sensitive glucose detection in beverage

NiO was one of the most utilized anode materials in glucose sensing, however, it suffers from inherent poor electronic conductivity and associated limited catalytic performance. In this paper, Mn-doped NiO nanosheets supported on carbon cloth (Mn–NiO NSs/CC) was prepared via annealing NiMn-layered double hydroxide (NiMn LDH) under air condition. As 3D integrated electrode, Mn–NiO NSs/CC shows superior catalytic activity towards glucose oxidation, and holds great potential in glucose sensitive sensing. Mn–NiO NSs/CC displays high performance, with a wide linear range from 2.0 μM to 2.14 mM, a high sensitivity of 3.53 mA mM−1 cm−2, and a low detection limit of 0.6 μM (S/N = 3). Additional, Mn–NiO NSs/CC shows excellent selectivity and reliability for glucose detection in sports beverages. This work provides a simple method for boosting NiO catalytic activity in glucose sensing, and builds a sensitive glucose sensor for food analysis.

Pd–Ni–P metallic glass nanoparticles for nonenzymatic glucose sensing

Metallic glass nanoparticles hold great promise as nonenzymatic glucose sensors due to their rich low-coordinated active sites and high biocompatibility. However, their non-periodic atomic structure and unclear structure-property relationship pose significant challenges for realizing and optimizing their sensing performance. In this work, Pd–Ni–P metallic glass nanoparticles with variable compositions were successfully prepared as nonenzymatic glucose sensors via a laser-evaporated inert-gas condensation method. The electrochemical tests show that the sensor based on Pd41·25Ni41·25P17.5 nanoparticles shows a wide linear detection range (0.003–1.31 ​mM), high sensitivity (516 ​μA ​mM−1 ​cm−2), and high stability (∼97.8% current retention after 1000 cycles). Local structural investigations using synchrotron pair distribution function and high-resolution microscopic techniques reveal a strong structural correlation within short-to medium-range orders in the Pd41·25Ni41·25P17.5 nanoparticles, which can be well retained after electrochemical cycling. These atomic-scale structural characteristics might be responsible for the high sensing performance. This study demonstrates the high applicability of Pd–Ni–P metallic glass nanoparticles as sensitive and stable non-enzymatic glucose sensors.

A review of electrochemical glucose sensing based on transition metal phosphides

The alarming situation of the growing number of diabetic patients has called for a simple, sensitive, and selective glucose sensor that is also stable and user-friendly. In this report, we have reviewed the latest electrochemical sensing technology based on transition metal phosphides (TMPs) for glucose detection. Apart from the oxides, sulfides, nitrides, chalcogenides, etc., transition metal phosphides are less explored and have emerged as potential candidates for non-enzymatic glucose sensing applications. This review will help scientists and researchers to exploit relevant properties for glucose sensing applications, identify the best synthesis approaches to prepare transition metal phosphides, and provide information on the factors influencing glucose sensing and parameters to improve the performance and theoretical insights into the mechanism involved. Therefore, this review emphasizes a few methods adopted for tuning the properties of TMPs to achieve a stable glucose-sensing device. Finally, we propose our perspectives on potential directions for TMP-based material development in enzymeless electrochemical glucose sensing applications.

Magnetic RuCo aerogels with enhanced peroxidase-like activity by regulation of boron and oxygen vacancies for colorimetric biosensing applications.

Metallic aerogels (MAs) are self-supported porous nanomaterials with excellent catalytic activity, which could be a promising candidate for high-performance nanozymes. The interface regulation by heteroatom and vacancies is an effective strategy for boosting the enzyme-mimicking activity. Herein, magnetic RuCo aerogels with doping of boron and oxygen vacancies were prepared by a one-pot spontaneous NaBH4 gelation method under a low temperature. The three-dimensional network structure with high specific surface area and interlinked pores of RuCo aerogels afford abundant active sites to facilitate the interaction with substrates. Moreover, the monolithic structure avoided conventional aggregation, thus enhancing stability during catalysis. Introducing elemtalboron and oxygen vacancies adjusted the electronic structure of RuCo aerogels to achieve enhanced enzyme-like performances. It is found that the RuCo aerogel nanozyme can mimic nature peroxidase, demonstrating their viable applications in the bioassay of H2O2 and glucose. The constructed glucose sensor possesses acceptable sensitivity and stability with a linear range of 0.002 ~ 5mM and a low detection limit (1.66μM). This work provides insights into the rational design of advanced nanozymes and paves the avenue for the applications of metallic aerogels in the bioassay field. A boron-doped RuCo bimetallic aerogel with rich oxygen vacancies was prepared by a facile self-assembly method under an ice bath. The unique physical and electronic structure of RuCo aerogel results in the improvement of the intrinsic peroxidaselike activity, and thus, a sensitive and robust colorimetric glucose sensor could be developed.

Cavitation regulated sonochemical synthesis of flexible self-supported CuO@PDA/CC electrode for highly sensitive glucose sensor

Sonochemical synthesis is recognized as a promising high-efficiency method for fabricating transition metal oxides (TMOs) based flexible self-supported electrodes as nonenzymatic glucose sensor. However, it is still a challenge to obtain TMOs self-supported electrodes with well-controlled TMOs nanostructure and desirable interfacial properties via a sonochemical approach because of the uncontrollability of transient cavitation. In this study, CuO@polydopamine (PDA) nanoparticles (NPs) are in situ grown onto carbon cloth (CC) to fabricate CuO@PDA/CC self-supported electrode via a sonochemical process. The sonochemically synthesized PDA not only stabilized the transient cavitation intensity, but also regulated the growth of CuO due to the strong chelating ability between Cu2+ and catechol groups from PDA. It is determined that the mean size of CuO@PDA NPs on the CuO@PDA/CC electrode is less than 100 nm with a narrow size distribution. Attributed to high electrochemical active surface area (4.61 mF cm−2) and low interface resistance (2.35 Ω), CuO@PDA/CC electrode displays excellent electrochemical performance as a glucose sensor with high sensitivity of 1.843 μA cm−2 mM−1 in a wide linear range up to 4.985 mM and excellent stability. This work provides a facile approach to fabricating the flexible self-supported electrodes with well-controlled nanostructure and desirable interfacial properties for high-performance electrochemical sensors via regulating the transient cavitation intensity in the sonochemical process.

Blood glucose sensing by back gated transistor strips sensitized by CuO hollow spheres and rGO

In this work, a highly sensitive flexible glucose sensor based on a field effect transistor (FET) has been fabricated. It is shown that the proposed flexible transistor can be used as new non-enzymatic blood glucose test strips. CuO hollow-spheres decorated with reduced graphene oxide have been synthesized using the hydrothermal method. The shells of the hollow micro-spheres are formed by nanostructures. The synthesized nanostructured hollow micro-spheres (rGO/CuO–NHS) are deposited on a flexible PET substrate between interdigitated electrodes as the channel of a back gate transistor. The channel concentration and the FET bias are optimized so that the sensor exhibits extremely low limit of detection and high sensitivity. The combination of selective porous CuO hollow spheres and the high surface to volume ratio of their nanostructured shells with the high mobility and high conductivity rGO led to faster and higher charge-transfer capability and superior electro-catalyst activity for glucose oxidation. The glucose-dependent electrical responses of the sensor is measured in both resistive and transistor action modes. The amplification of the current by the induced electric field of the gate in the proposed FET-based biosensor provides advantages such as higher sensitivity and lower limit of detection compared to the resistive sensor. The flexible glucose sensor has a sensitivity of 600 μA μM−1 and a limit of detection of 1 nM with high reproducibility, good stability, and highly selectivity. The high accuracy response of the biosensor towards the real blood serum samples showed that it can be used as a test strip for glucose detection in real blood samples.

Highly efficient non-enzymatic electrochemical glucose sensor based on carbon nanotubes functionalized by molybdenum disulfide and decorated with nickel nanoparticles (GCE/CNT/MoS2/NiNPs)

Glucose detection using sensing materials has lately received interest due to the increased demand for sensitive and selective glucose sensors in pharmaceutical, clinical, and industrial settings. Carbon nanotubes (CNTs) are used intensively as a specific class of effective electrode substances in electrochemical sensing due to their large surface area and interesting physical and electrochemical characteristics. Nickel is an attractive transition metal for glucose electrooxidation with high catalytic activity. In this study, CNT/MoS2/NiNPs nanocomposites with different CNT/MoS2 ratios have been prepared by a hydrothermal reaction. The CNT/MoS2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR), and their morphology and composition were characterized by field emission scanning electron microscopy (FESEM). Electrocatalytic activity of the as-prepared nanomaterials towards glucose oxidation was investigated by cyclic voltammetry and amperometry in alkaline media. An excellent sensitivity value of 1212 μA·mM−1·cm−2 with a wide linear range (0.05–0.65 mM), a low detection threshold of 0.197 μM and a short response time (3 s) were achieved by the hybrid CNT/MoS2/NiNPs sensor. Its superior catalytic activity and low cost make this hybrid very promising for applications in the direct sensing of glucose.

Gold Nanoparticle (Au NP)-Decorated Ionic Liquid (IL) Based Liposome: A Stable, Biocompatible, and Conductive Biomimetic Platform for the Fabrication of an Enzymatic Electrochemical Glucose Biosensor

A novel liposomal nanocomposite with biocompatibility and conductivity, Au@ILs-polysome, was fabricated and first utilized as the electrode material to immobilize the redox enzyme glucose oxidase (GOD) for the sensitive determination of glucose. Ionic liquids (ILs)-based polysome (ILs-polysome) was prepared via the radical polymerization of ILs based liposome (ILs-liposome) and improved by ion exchange with chloroauric acid to prepare Au nanoparticles (Au NPs) modified ILs based polysome (Au@ILs-polysome). The morphology, surface properties, and structure of Au@ILs-polysome were characterized; the results suggest that the nanocomposite exhibited excellent stability on the surface of solid electrodes without fusion. Electrochemical impedance spectroscopy (EIS) demonstrated that the nanocomposite had enhanced conductivity. Cyclic voltammetry (CV) shows that the direct electron transfer of GOD was achieved on the GOD/Au@ILs-polysome/GCE electrode since the Au@ILs-polysome provided a biocompatible microenvironment that made the immobilized enzyme stay natural and active. Differential pulse voltammetry (DPV) demonstrates that the GOD/Au@ILs-polysome/GCE electrode exhibited improved electrocatalytic activity compared with the GOD/ILs-polysome/GCE electrode. The electrochemical sensor exhibited a low detection limit of 0.02 mM, high sensitivity of 32.52 µA mM−1 cm−2, high selectivity toward glucose, and good stability. The practical application of the sensor was verified by the determination of glucose in human serum. The multi-component liposomal nanocomposites possess universal significance in protein-based direct electrochemical devices while offering a facile route to fabricating a highly sensitive glucose sensor for practical clinical diagnosis.

Sandwich structure confined gold as highly sensitive and stable electrochemical non-enzymatic glucose sensor with low oxidation potential

• Fe 3 O 4 @Au@CoFe-LDH is prepared through a spontaneous galvanic displacement reaction. • In Fe 3 O 4 @Au@CoFe-LDH, the metallic Au intercalates between Fe 3 O 4 and LDH forming the sandwich structure. • Fe 3 O 4 @Au@CoFe-LDH possesses high sensitivity of 6342 μA mM −1 cm −2 , broad linear detection range of 0.0375 to 15.64 mM and low limit of detection of 12.7 μM, with an extremely low oxidation potential of 0.82 V vs. RHE. • The small quantity of Au laying between LDH and Fe 3 O 4 is the active part of glucose oxidation and the existence of Fe 3 O 4 nanoparticles significantly improves the stability of the electrocatalyst. The preparation of highly sensitive and stable non-enzymatic glucose sensors is critical to the prevention and treatment of diabetes. Fe 3 O 4 @Au@CoFe-LDH is prepared through a spontaneous galvanic displacement reaction. A series of structural characterizations testify the successful formation of Fe 3 O 4 @Au@CoFe-LDH electrocatalyst, with the Au intercalating between Fe 3 O 4 and LDH to form the sandwich structure. Cyclic voltammetry tests indicate that Au is responsible for the electrocatalytic oxidation of glucose. The characterizations of the electrochemical sensor for glucose detection indicate that Fe 3 O 4 @Au@CoFe-LDH possesses high sensitivity of 6342 μA mM −1 cm −2 , with an extremely low oxidation potential of 0.82 V vs. RHE. Even with the high glucose concentration of 15 mM, the sensitivity remains at 4359 μA mM −1 cm −2 . Due to the broad linear detection range (0.0375 to 15.64 mM) and the low limit of detection (12.7 μM), Fe 3 O 4 @Au@CoFe-LDH is applicable towards practical application. Thanks to the sandwich structure, which confines the Au in between Fe 3 O 4 and CoFe-LDH, the Fe 3 O 4 @Au@CoFe-LDH glucose sensor shows high long-term stability and satisfactory selectivity. The successful synthesis of the sandwich-structured Fe 3 O 4 @Au@CoFe-LDH provides a new conception for the design of highly sensitive and stable non-enzymatic glucose electrodes.

A fully handwritten-on-paper copper nanoparticle ink-based electroanalytical sweat glucose biosensor fabricated using dual-step pencil and pen approach

This article reports a facile fabrication of a highly sensitive enzyme-free sweat glucose sensor over Whatman filter paper substrate employing a dual-step pencil and pen approach. Initially, two pencil-drawn electrodes (PDEs) are obtained on the filter paper through the manual abrasion of an 8B graphite pencil. Then, the sensing layer is drawn over one of the PDEs using a custom-made copper (Cu) nanoparticle ink (CuNP-ink) pen to form copper nanoparticle ink decorated PDE (CuNP-ink/PDE) which serves as a working electrode, while the other PDE is drawn with silver conductive ink (Ag-ink) pen to form reference electrode. The developed CuNP-ink/PDE is composed of 43.5% of metallic Cu nanoparticles, inducing a highly crystalline and conductive nature, thus promoting fast electron transfer during glucose electrooxidation. The developed sensor offers a sensitivity of 2691.7 μAmM−1cm−2, a detection limit of 0.5 μM, a linear range of 1.2–40 μM, and a fast response time of ∼ 1.5 s. Besides, the sensor measurements are stable, reproducible, and selective in glucose sensing. Also, the reliability of the sensor is tested by comparing its performance with a UV–Visible spectrophotometer for proving its efficacy in sweat glucose detection. Experimental results evince the effectiveness of the designed sensor for glucose detection in human sweat.