Detection of Glucose Based on Bimetallic PtCu Nanochains Modified Electrodes

A bimetallic PtAu-modified carbon fiber electrochemical sensor for simultaneous and highly sensitive detection of catechol and hydroquinone in environmental water

In this study, we report the development of a novel electrochemical sensor capable of the simultaneous detection of catechol (CC) and hydroquinone (HQ) through differential pulse voltammetry. The sensor is constructed using carbon fiber (CF) that has been intricately modified with bimetallic PtAu nanoparticles. The fabrication process involves subjecting CF to ultrasound treatment in an acidic mixture, resulting in the formation of activated carbon fiber (ACF). This activation step not only enhances surface roughness but also facilitates subsequent modification, ensuring the stability of the material. Bimetallic PtAu nanoparticles are then uniformly deposited onto the ACF surface through co-deposition from a metal precursor solution. The modified ACF, adorned with bimetallic PtAu nanoparticles, exhibits excellent conductivity and efficiently catalyzes both CC and HQ in a 10 mM phosphate-buffered saline solution at pH 7.0, thereby enabling their simultaneous detection. Under optimized experimental conditions, this electrochemical sensor achieves impressive detection limits of 0.019 μM for CC and 0.28 μM for HQ within the same concentration range of 0.5-50 μM, respectively. The practicality of the sensor is further demonstrated through recovery experiments using real water samples. This electrochemical sensor, with its superior performance and versatility, shows great potential for applications in analytical chemistry and environmental monitoring.

Hierarchical N-doped porous carbon scaffold Cu/Co-oxide with enhanced electrochemical sensing properties for the detection of glucose in beverages and ascorbic acid in vitamin C tablets

This research focuses on the development of a highly efficient electrocatalyst, CuxO/NPC@Co3O4/NPC-10-7, for detecting glucose and ascorbic acid. In a 0.1 M NaOH solution, the modified electrode exhibits a sensitivity of 3314.29 μA mM-1 cm-2 for glucose detection. The linear range for ascorbic acid sensing is 0.5 μM - 23.332 mM, with a detection limit as low as 0.24 μM. In a 0.1 M PBS solution, the linear range for ascorbic acid detection extends to 43.328 mM, which represents the best performance reported to date by chronoamperometry. Moreover, the electrode demonstrates high accuracy, with a recovery rate of 96.80 % - 103.60 % for glucose detection and a recovery rate of 95.25 % - 104.83 % for ascorbic acid detection. These results suggest that the CuxO/NPC@Co3O4/NPC-10-7 modified electrode shows significant potential for practical applications in food detection.

Highly Fluorescent ZnO Composite of N-doped Carbon Dots From Dregea Volubilis for Fluorometric Determination of Glucose in Biological Samples

A nano-sensor based on N-doped carbon dots (NCDs)@ZnO (NCZ) composite was fabricated and efficacy for detecting glucose from human blood and urine samples in a straightforward manner was examined. The composite was prepared following a green hydrothermal method under ambient condition using a novel plant material, Dregea volubilis fruit and structural and optical properties were evaluated using standard techniques. The composite exhibited excellent characteristics including good photostability, biocompatibility, low toxicity, and strong fluorescence, with a decent quantum yield of up to 59%. The NCZ composite has been very sensitive and could selectively detect glucose in urine and blood samples. Selective glucose quenching was efficacious at different concentrations of glucose (1-6 mM) and in the pH range of 7-8, limit of detection was 0.25 mM. The potential uses of carbon-based materials have grown, thanks to the excellent sensing/detection capabilities of the NCZ composite as well as the capacity to prevent nanoparticle aggregation, opening up new possibilities for the development of environmentally benign nano-sensors.

Three-Phases Interface Induced Local Alkalinity Generation Enables Electrocatalytic Glucose Oxidation in Neutral Electrolyte

Electrocatalytic glucose oxidation is crucial to the development of non-enzymatic sensors, an attractive alternative for enzymatic biosensors. However, due to OH^- consumption during the catalytic process, non-enzymatic detection generally requires electrolytes having an alkaline pH value, limiting its practical application since biofluids are neutral. Herein, via interfacial microenvironment design, we addressed this limitation by developing a non-enzymatic sensor with an air-solid-liquid triphase interface electrodes that synergistically integrates the functions of local alkalinity generation and electrocatalytic glucose oxidation. A sufficiently high local pH value was achieved via oxygen reduction reaction at the triphase interface, which consequently enabled the electrochemical oxidation (detection) of glucose in neutral solution. Moreover, we found that the linear detection range and sensitivity of triphase non-enzymatic sensor can be tuned by changing the electrocatalysts of the detection electrode. The triphase electrode architecture provides a new platform for further exploration and promotes practical application of non-enzymatic sensors.

Porous Carbon Substrate Improving the Sensing Performance of Copper Nanoparticles Toward Glucose

An accurate sensor to rapidly determine the glucose concentration is of significant importance for the human body health, as diabetes has become a very high incidence around the world. In this work, copper nanoparticles accommodated in porous carbon substrates (Cu NP@PC), synthesized by calcinating the filter papers impregnated with copper ions at high temperature, were designed as the electrode active materials for electrochemical sensing of glucose. During the formation of porous carbon, the copper nanoparticles spontaneously accommodated into the formed voids and constituted the half-covered composites. For the electrochemical glucose oxidation, the prepared Cu NP@PC composites exhibit much superior catalytic activity with the current density of 0.31 mA/cm2 at the potential of 0.55 V in the presence of 0.2 mM glucose. Based on the high electrochemical oxidation activity, the present Cu NP@PC composites also exhibit a superior glucose sensing performance. The sensitivity is determined to be 84.5 μA /(mmol.L) with a linear range of 0.01 ~ 1.1 mM and a low detection limit (LOD) of 2.1 μmol/L. Compared to that of non-porous carbon supported copper nanoparticles (Cu NP/C), this can be reasonable by the improved mass transfer and strengthened synergistic effect between copper nanoparticles and porous carbon substrates.

Glucose oxidase decorated fluorescent metal-organic frameworks as biomimetic cascade nanozymes for glucose detection through the inner filter effect

Metal-organic frameworks (MOFs) as a peroxidase mimic have been integrated with glucose oxidase (GOx) to achieve one-step glucose detection. However, limited by the loading amount of GOx, the performances of the developed glucose sensing assays still remain to be further improved to meet sensing requirements in diverse biological samples. Herein, with Fe3+ as the metal ion and 2-amino-benzenedicarboxylic acid as a ligand, a fluorescent Fe-based organic framework (NH2-MIL-101) with peroxidase-like activity was synthesized. Due to the large specific surface area (791.75 m2 g-1), 68 μg mg-1 GOx could be immobilized through the amidation coupling reaction, and the product was designated GOx@NH2-MIL-101. With OPD as the substrate, Gox@NH2-MIL-101 achieved highly efficient biomimetic cascade catalysis for one-step glucose detection through an inner filter effect: upon reacting with glucose, GOx@NH2-MIL-101 catalytically oxidized glucose using dissolved O2, and the produced H2O2 concurrently oxidized o-phenylenediamine (OPD) to oxidized OPD (oxOPD), accompanied by the fluorescence of GOx@NH2-MIL-101 at 456 nm being quenched and that of oxOPD at 565 nm being enhanced. With the fluorescent ratio F565/F456 used as a readout signal, a wide linear range of 0.1-600 μM was obtained, and the detection limit was 0.0428 μM. Based on the excellent selectivity and high stability of GOx@NH2-MIL-101, the developed assay was successfully applied to glucose detection in human serum and saliva, presenting potential applications in diverse biological samples and even medical diagnosis.

High rate fabrication of copper and copper-gold electrodes by laser-induced selective electroless plating for enzyme-free glucose sensing

In the current study, the method of Selective Surface Activation Induced by Laser (SSAIL) was used for the fabrication of metallic and bimetallic structures based on copper and gold on the surface of glass and glass-ceramics. It was shown that the fabricated electrodes are suitable for non-enzymatic detection of biologically essential analytes such as glucose. The implemented approach allows performing high-rate metallization of various dielectrics. Voltammetric methods were applied to evaluate the electrocatalytic activity of the obtained structures, which were used as working electrodes. The most promising results were revealed by copper–gold electrode structures manufactured on glass-ceramics. For these structures, sensitivity towards glucose sensing was 3060 μA mM⁻¹ cm⁻². The linear range of glucose detection varied between 0.3 and 1000 μM. Besides, the manufactured electrodes exhibited high selectivity and long-term stability.

In the current study, the method of Selective Surface Activation Induced by Laser (SSAIL) was used for the fabrication of metallic and bimetallic structures based on copper and gold on the surface of glass and glass-ceramics.

Synthesis of Au–Cu Alloy Nanoparticles as Peroxidase Mimetics for H2O2 and Glucose Colorimetric Detection

The detection of hydrogen peroxide (H2O2) is essential in many research fields, including medical diagnosis, food safety, and environmental monitoring. In this context, Au-based bimetallic alloy nanomaterials have attracted increasing attention as an alternative to enzymes due to their superior catalytic activity. In this study, we report a coreduction synthesis of gold–copper (Au–Cu) alloy nanoparticles in aqueous phase. By controlling the amount of Au and Cu precursors, the Au/Cu molar ratio of the nanoparticles can be tuned from 1/0.1 to 1/2. The synthesized Au–Cu alloy nanoparticles show good peroxidase-like catalytic activity and high selectivity for the H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB, colorless) to TMB oxide (blue). The Au–Cu nanoparticles with an Au/Cu molar ratio of 1/2 exhibit high catalytic activity in the H2O2 colorimetric detection, with a limit of detection of 0.141 μM in the linear range of 1–10 μM and a correlation coefficient R2 = 0.991. Furthermore, the Au–Cu alloy nanoparticles can also efficiently detect glucose in the presence of glucose oxidase (GOx), and the detection limit is as low as 0.26 μM.

A Non-Enzymatic Sensor Based on Fc-CHIT/CNT@Cu Nanohybrids for Electrochemical Detection of Glucose

Herein, a composite structure, consisting of Cu nanoparticles (NPs) deposited onto carbon nanotubes and modified with ferrocene-branched chitosan, was prepared in order to develop a nonenzymatic electrochemical glucose biosensor ferrocene-chitosan/carbon nanotube@ Cu (Fc-CHIT/CNT@Cu). The elemental composition of the carbon nanohybrids, morphology and structure were characterized by various techniques. Electrochemical impedance spectroscopy (EIS) was used to study the interfacial properties of the electrodes. Cyclic voltammetry (CV) and chronoamperometry methods in alkaline solution were used to determine glucose biosensing properties. The synergy effect of Cu NPs and Fc on current responses of the developed electrode resulted in good glucose sensitivity, including broad linear detection between 0.2 mM and 22 mM, a low detection limit of 13.52 μM and sensitivity of 1.256 μA mM⁻¹cm⁻². Moreover, the modified electrode possessed long-term stability and good selectivity in the presence of ascorbic acid, dopamine and uric acid. The results indicated that this inexpensive electrode had potential application for non-enzymatic electrochemical glucose detection.

Electrochemical glucose sensors in diabetes management: an updated review (2010-2020)

While over half a century has passed since the introduction of enzyme glucose biosensors by Clark and Lyons, this important field has continued to be the focus of immense research activity. Extensive efforts during the past decade have led to major scientific and technological innovations towards tight monitoring of diabetes. Such continued progress toward advanced continuous glucose monitoring platforms, either minimal- or non-invasive, holds considerable promise for addressing the limitations of finger-prick blood testing toward tracking glucose trends over time, optimal therapeutic interventions, and improving the life of diabetes patients. However, despite these major developments, the field of glucose biosensors is still facing major challenges. The scope of this review is to present the key scientific and technological advances in electrochemical glucose biosensing over the past decade (2010-present), along with current obstacles and prospects towards the ultimate goal of highly stable and reliable real-time minimally-invasive or non-invasive glucose monitoring. After an introduction to electrochemical glucose biosensors, we highlight recent progress based on using advanced nanomaterials at the electrode-enzyme interface of three generations of glucose sensors. Subsequently, we cover recent activity and challenges towards next-generation wearable non-invasive glucose monitoring devices based on innovative sensing principles, alternative body fluids, advanced flexible materials, and novel platforms. This is followed by highlighting the latest progress in the field of minimally-invasive continuous glucose monitoring (CGM) which offers real-time information about interstitial glucose levels, by focusing on the challenges toward developing biocompatible membrane coatings to protect electrochemical glucose sensors against surface biofouling. Subsequent sections cover new analytical concepts of self-powered glucose sensors, paper-based glucose sensing and multiplexed detection of diabetes-related biomarkers. Finally, we will cover the latest advances in commercially available devices along with the upcoming future technologies.

Facile preparation of Ni nanoparticle embedded on mesoporous carbon nanorods for non-enzymatic glucose detection

Transition metal doped carbon materials are recognized as promising sensing platforms for glucose detection. Herein, a simple strategy involving crystallinity, nanostructure engineering, and pyrolysis was developed for constructing well-defined Ni nanoparticle embedded on nanoporous carbon nanorods (Ni/NCNs). A three-dimensional nickel-based metal-organic framework (Ni-MOF) was used as both a self-sacrificing template and precursor. Due to the synergistic effects between the uniformly dispersed Ni nanoparticles and the nanoporous carbon matrix, the as-prepared Ni/NCNs exhibited remarkable electrochemical activity. The fabricated Ni/NCNs glucose sensor showed excellent electrocatalytic performance with ultra-low limit of detection, wide linear detection ranges, fast response times (within 1.6 s), superior stability, and anti-interference characteristics. Moreover, the Ni/NCNs sensing platform was successfully applied to analyze glucose concentrations in human blood samples. These results showed that Ni/NCNs hold potential applications in developing enzyme-free glucose sensors.

An Electrochemical Non-Enzymatic Glucose Sensor Based on Ultrathin PdAg Single-Crystalline Nanowires

Electrochemical non-enzymatic sensors have great potential for prompt and efficient detection of glucose. Herein, a novel, highly efficient electrochemical non-enzymatic glucose sensor is reported that is based on ultrathin PdAg single-crystalline nanowires (NWs). Ultrathin PdAg NWs are fabricated by a facile one-pot aqueous synthesis through an in situ growth strategy with an amphiphilic surfactant as the template. A comparison of the activities of PdAg NWs with different compositional ratios and nanostructures shows that ultrathin Pd₂ Ag₁ NWs hold the best performance toward electrochemical detection of glucose with an operable sensitivity of 11.6 μA mM^-1  cm^-2 and a linear response range of 0.1-8 mM. Structural and compositional features of the Pd₂ Ag₁ NWs allow an excellent selectivity, rapid response, and good long-term stability for electrochemical glucose sensor. This work thus provides a new possibility for the rational design and synthesis of noble-metal-based nanomaterials for non-enzymatic sensors.

Cobalt-copper bimetallic nanostructures prepared by glancing angle deposition for non-enzymatic voltammetric determination of glucose

A bimetallic nanostructure of Co/Cu for the non-enzymatic determination of glucose is presented. The heterostructure includes cobalt thin film on a porous array of Cu nanocolumns. Glancing angle deposition (GLAD) method was used to grow Cu nanocolumns directly on a fluorine-doped tin oxide (FTO) substrate. Then a thin film of cobalt was electrodeposited on the Cu nanostructures. Various characterization studies were performed in order to define the optimum nanostructure for the determination of glucose. The results showed remarkable boosting of the electrocatalytic activity of Co/Cu bimetallic structure compare to the responses achieved by the monometallic structures of Co or Cu. The sensor showed two linear response ranges for the determination of glucose at 0.55 V in 0.1 M NaOH, from 5 μM-1 mM and 2-9 mM. The sensitivity was 1741 (μA mM^-1 cm^-2) and 626 (μA mM^-1 cm^-2), respectively, while the detection limit for a signal-to-noise ratio of 3 was found to be 0.4 μM. The sensor exhibited excellent selectivity and was successfully applied to the determination of glucose in real human blood serum samples. Graphical Abstract Schematic representation of fabrication process of the glucose sensor of Co (Cobalt)/Cu (Copper) on Fluorine doped Tin Oxide (FTO). The current voltage plots show higher electrooxidation activity of the bimetallic nanostructure of Co/Cu/FTO relative to the bare Co/FTO.

One-step cascade detection of glucose at neutral pH based on oxidase-integrated copper(ii) metal–organic framework composites

An integrated system was fabricated from a copper(ii) metal–organic framework (Cu-MOF) and glucose oxidase (GOx) for one-step cascade determination of glucose at neutral pH (pH = 7.0).

A comparative study of electrocatalytic oxidation of glucose on conductive Ni-MOF nanosheet arrays with different ligands

A glucose sensor based on conductive Ni-MOF nanosheet arrays/CC exhibits a fast response time, a low detection limit, a high sensitivity, and it can also be applied for the detection of glucose in human serum samples.

Electrochemical non-enzymatic glucose sensors: recent progress and perspectives

This review summarizes recent advances in the development of electrocatalysts for non-enzymatic glucose detection. The sensing mechanism and influencing factors are discussed, and the perspectives and challenges are also addressed.

Preparation of co-Co3 O4 /carbon nanotube/carbon foam for glucose sensor

Co-Co₃ O₄ /carbon nanotube/carbon foam (Co-Co₃ O₄ /CNT/CF) nanocomposites were prepared by soaking melamine foam into a solution of Co(NO₃ )₂ ·6H₂ O, followed by calcination in N₂ and air in sequence. The obtained Co-Co₃ O₄ /CNT/CF nanocomposites were characterized with scanning electron microscopy and cyclic voltammetry. It was found that Co₃ O₄ nanoparticles were grown on the external of CF successfully, while CNTs were grown on the surfaces of CF in a large amount, which further improved the electrical conductivity of the. The prepared Co-Co₃ O₄ /CNT/CF nanocomposites were then used to construct nonenzymatic sensor to detect glucose in alkaline solution. The sensor showed detection range from 1.2 μM to 2.29 mM with a detection limit of 0.4 μM (S/N =3) and a high sensitivity of 637.5 μA^-1 cm^-2 . The developed sensor also showed an instant response, favorable reproducibility, and high selectivity. The results attest that Co-Co₃ O₄ /CNT/CF composites have great potential in the development of nonenzymatic sensors for glucose.

Ultrafine PtCuRh nanowire catalysts with alleviated poisoning effect for efficient ethanol oxidation

As a green power source, direct ethanol fuel cells (DEFCs) have broad application prospects. However, most catalysts of DEFCs still exhibit defects, such as the difficulty of C-C bond cleavage, serious CO poisoning and limited catalytic activity. Here, we report ultrafine PtCuRh nanowires (NWs) with outstanding anti-CO-poisoning properties and enhanced activity. The average diameter of the ultrafine PtCuRh NWs is about 1.49 nm, effectively improving the atomic utilization efficiency (UE) of platinum. Owing to the combination of an ultrafine nanostructure, good electronic interaction and the high UE of Pt atoms, the optimized ultrafine PtCuRh NWs/C display superior electrocatalytic activity and stability compared with commercial Pt/C for the ethanol oxidation reaction (EOR). More importantly, further electrochemical results demonstrate that the incorporation of Rh is beneficial for enhancing the antipoisoning capability for some CO-like intermediates. Meanwhile, the synthetic method in this report is robust and universal, and can also be applied to the synthesis of ultrafine trimetallic PtCuPd and PtCuIr nanowires.

Salt-Templated Platinum-Copper Porous Macrobeams for Ethanol Oxidation

Platinum nanomaterials provide an excellent catalytic activity for diverse applications and given its high cost, platinum alloys and bi-metallic nanomaterials with transition metals are appealing for low cost and catalytic specificity. Here the synthesis of hierarchically porous Pt–Cu macrobeams and macrotubes templated from Magnus’s salt derivative needles is demonstrated. The metal composition was controlled through the combination of [PtCl4]2− with [Pt(NH3)4]2+ and [Cu(NH3)4]2+ ions in different ratios to form salt needle templates. Polycrystalline Pt–Cu porous macrotubes and macrobeams 10’ s–100’ s μm long with square cross-sections were formed through chemical reduction with dimethylamine borane (DMAB) and NaBH4, respectively. Specific capacitance as high as 20.7 F/g was demonstrated with cyclic voltammetry. For macrotubes and macrobeams synthesized from Pt2−:Pt2+:Cu2+ salt ratios of 1:1:0, 2:1:1, 3:1:2, and 1:0:1, DMAB reduced 3:1:2 macrotubes demonstrated the highest ethanol oxidation peak currents of 12.0 A/g at 0.5 mV/s and is attributed to the combination of a highly porous structure and platinum enriched surface. Salt templates with electrochemical reduction are suggested as a rapid, scalable, and tunable platform to achieve a wide range of 3-dimensional porous metal, alloy, and multi-metallic nanomaterials for catalysis, sensor, and energy storage applications.

Highly sensitive colorimetric detection of glucose through glucose oxidase and Cu2+-catalyzed 3,3',5,5'-tetramethylbenzidine oxidation

We develop a glucose oxidase (GOx)-mediated strategy for detecting glucose based on oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB), which is generated from Cu²⁺-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ reaction, as colorimetric readout. The sensing system involves two processes: generation of H₂O₂ from GOx-catalyzed oxidation of glucose, and H₂O₂-induced the oxidization of TMB via the catalysis of Cu²⁺. The H₂O₂ formed by GOx-catalyzed oxidation of glucose oxidizes colorless TMB to blue oxTMB, thus enhancing the absorbance intensity at 670 nm. Therefore, we draw a conclusion that the enhancement in colorimetric signal relies directly on H₂O₂ concentration, which, in turn, depends on glucose concentration. This color change can be used not only for visual detection of glucose by naked eyes but for reliable glucose quantification in the range from 1 to 100 nM with a detection limit of 0.21 nM. The method possesses the following advantages: simple design, low experimental cost, and no any additional experimental equipment for heating, illuminating, or bubbling.

Engineering FeCo alloy@N-doped carbon layers by directly pyrolyzing Prussian blue analogue: new peroxidase mimetic for chemiluminescence glucose biosensing

Direct pyrolysis of a Prussian blue analogue produced FeCo@NC with high and stable peroxidase-like activity, which catalyzes luminol oxidation by H₂O₂ to generate strong CL emission, and this finding results in a new CL biosensor for glucose.

Reduced graphene oxide doping with nanometer-sized ferrocene moieties - New active material for glucose redox sensors

Herein, we present that the reduced graphene oxide (rGO) doped with nanometer-sized ferrocene moieties is a new, excellent active material for redox sensors. Two distinct approaches were utilized for the modification of rGO. The first method was based on the covalent decoration of rGO via the addition of azomethine ylide generated from the ferrocenecarboxaldehyde oxime. The second approach utilized the adsorption of 1,1'-ferrocenedicarboxylic acid on the graphene sheet via the π-π stacking. The morphology of the synthesized graphene materials was studied by application of microscopic techniques, whereas the Raman data allowed the characteristics of the tested materials in terms of their structural properties. The tested graphene materials doped with ferrocene moieties were used as a bioactive platform for glucose oxidase (GOx) immobilization. The enzyme was immobilized onto the rGO materials in two ways: (i) using a crosslinking agent - glutaraldehyde (GA) and (ii) by formation of the amide bonds between carboxylic groups of rGO-Fc(COOH)₂ and amine groups from enzyme. Ferrocene moieties present at the graphene surface play the role of mediator in the electron transfer between the redox center of GOx and the electrode surface. The functionality of the constructed biosensors has been tested on real samples. The results of the recovery rates showed a satisfying degree of accuracy toward determination of glucose concentration. Examination of the potential interfering species has demonstrated favorable sensitivity and selectivity of the designed biosensor for the detection of glucose.

In situ laser-induced codeposition of copper and different metals for fabrication of microcomposite sensor-active materials

We report one-step in situ laser-induced synthesis of the conductive copper microstructures doped with iron, zinc, nickel, and cobalt with highly developed surface area. It was observed that the presence of chlorides of the aforementioned metals in the solutions used in our experiments increases the deposition rate and the amount of copper in the resulting deposits; it also leads to the deposit miniaturization. The laser deposition from solutions containing cobalt (II) chloride of concentration more than 0.003 M results in fabrication of copper microelectrode with better electrochemical properties than those deposited from solutions containing chlorides of other metals of the same concentration. Moreover, copper microelectrode doped with cobalt has demonstrated good reproducibility and long-run stability as well as sensitivity and selectivity towards determination of hydrogen peroxide (limit of detection-0.2 μM) and d-glucose (limit of detection-2.2 μM). Thus, in this article we have shown the opportunity to manufacture two-phase microcomposite materials with good electrical conductivity and electrochemical characteristics using in situ laser-induced metal deposition technique. These materials might be quite useful in development of new perspective sensors for non-enzymatic detection of such important analytes as hydrogen peroxide and glucose.

Formation of porous Cu hydroxy double salt nanoflowers derived from metal-organic frameworks with efficient peroxidase-like activity for label-free detection of glucose

Currently, nanomaterials with peroxidase activity have become an important colorimetric tool for biomolecular detection. However, compared with natural enzymes, the efficiency of most nanozymes is still lower. Here, with a leaf-like metal-organic-framework-5 as both a precursor and a template and copper acetate as a second precursor, hierarchical Cu hydroxy double salt (HDS) nanoflowers have been prepared and used as a label-free glucose colorimetric detection platform. We have demonstrated a scalable and facile synthesis of hierarchical Cu HDS nanoflowers, and density functional theory (DFT) calculations confirmed that there exists a hydrogen bond between the terephthalate anions and the layer OH group. The composition of Cu hydroxyl double salt is [Cu4(OH)6][BDC]·2H2O. Importantly, for the first time, the as-prepared Cu HDSs were demonstrated as peroxidase mimics to catalyze the oxidation of the enzyme substrate, 3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, which accompanies a color change from colorless to blue and followed classic Michaelis-Menten models. Based on these findings, a colorimetric method based on Cu HDSs that is highly sensitive and selective for the detection of glucose was developed, with a low detection limit of 0.5 μM. The clinical applicability of the sensor is also proven to be suitable for sensing glucose in blood, suggesting that Cu HDSs could be used in the construction of portable sensors for point-of-care diagnosis and on-site tests.

Recent advances in electrochemical non-enzymatic glucose sensors - A review

This review encompasses the mechanisms of electrochemical glucose detection and recent advances in non-enzymatic glucose sensors based on a variety of materials ranging from platinum, gold, metal alloys/adatom, non-precious transition metal/metal oxides to glucose-specific organic materials. It shows that the discovery of new materials based on unique nanostructures have not only provided the detailed insight into non-enzymatic glucose oxidation, but also demonstrated the possibility of direct detection in whole blood or interstitial fluids. We critically evaluate various aspects of non-enzymatic electrochemical glucose sensors in terms of significance as well as performance. Beyond laboratory tests, the prospect of commercialization of non-enzymatic glucose sensors is discussed.

Colorimetric detection of glucose based on ficin with peroxidase-like activity

In this work, we developed a colorimetric biosensing system for glucose detection by coupling the peroxidase-like of ficin and the glucose oxidase (GOx). GOx can catalyze the oxidation of glucose to produce H₂O₂, then, ficin catalyzes the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce a blue color reaction. The present sensing system showed a linear response toward glucose detection over range of 2.0-100μM with a detection limit of 0.5μM. This system is simple, low cost, highly sensitive and selective for glucose detection, and was also applied to measuring glucose in human serum. Furthermore, in order to expand the application of ficin in biological sensing, we immobilized ficin onto the SiO₂@Fe₃O₄ NPs, which exhibited the merits of recycling as well as allowing the repeated detection of glucose. Thus it may provide great potential applications in biomedicine, biotechnology and environmental chemistry.

Monolithic copper selenide submicron particulate film/copper foam anode catalyst for ultrasensitive electrochemical glucose sensing in human blood serum

A copper selenide submicron particulate film on Cu foam, synthesized by a facile hydrothermal process, shows superior glucose sensing performance.

Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials

An overview (with 376 refs.) is given here on the current state of methods for electrochemical sensing of glucose based on the use of advanced nanomaterials. An introduction into the field covers aspects of enzyme based sensing versus nonenzymatic sensing using nanomaterials. The next chapter cover the most commonly used nanomaterials for use in such sensors, with sections on uses of noble metals, transition metals, metal oxides, metal hydroxides, and metal sulfides, on bimetallic nanoparticles and alloys, and on other composites. A further section treats electrodes based on the use of carbon nanomaterials (with subsections on carbon nanotubes, on graphene, graphene oxide and carbon dots, and on other carbonaceous nanomaterials. The mechanisms for electro-catalysis are also discussed, and several Tables are given where the performance of sensors is being compared. Finally, the review addresses merits and limitations (such as the frequent need for working in strongly etching alkaline solutions and the need for diluting samples because sensors often have analytical ranges that are far below the glucose levels found in blood). We also address market/technology gaps in comparison to commercially available enzymatic sensors. Graphical Abstract Schematic representation of electrochemical nonenzymatic glucose sensing on the nanomaterials modified electrodes. At an applied potential, the nanomaterial-modified electrodes exhibit excellent electrocatalytic activity for direct oxidation of glucose oxidation.

Palladium-copper nanowires-based biosensor for the ultrasensitive detection of organophosphate pesticides

A highly sensitive acetylcholinesterase (AChE) electrochemical biosensor for the quantitative determination of organophosphate pesticides (OPs) in vegetables and fruits based on palladium-copper nanowires (Pd-Cu NWs) was reported. AChE immobilized on the modified electrode could catalyze hydrolysis of acetylthiocholine chloride (ATCl), generating an irreversible oxidation peak. When exposed to the OPs, the activity of the AChE was inhibited and the current significantly decreased. The detection mechanism is based on the inhibition of AChE. The Pd-Cu NWs not only provide a large active surface area (0.268 ± 0.01) cm² for the immobilization of AChE, which was approximately 3.8 times higher than the bare glass carbon electrode, but also exhibit excellent electro-catalytic activity and remarkable electron mobility. The biosensor modified with Pd-Cu NWs displayed a good affinity to ATCl and catalyzed hydrolysis of ATCl, with a low Michaelis-Menten constant (K_M) of 50.56 μM. Under optimized conditions, the AChE-Cs/Pd-Cu NWs/GCE biosensor detected malathion with wide linear ranges of 5-1000 ppt and 500-3000 ppb, and the low detection limit was 1.5 ppt (4.5 pM). In addition, the OPs biosensor has been applied to the analysis of malathion in commercial vegetable and fruit samples, with excellent recoveries in the range of 98.5%-113.5%. This work provides a simple, sensitive and effective platform for biosensors and exhibits future potential in practical application for the OPs assay.

Rational design of porous binary Pt-based nanodendrites as efficient catalysts for direct glucose fuel cells over a wide pH range

Porous binary PtPd, AuPt, PtCu, and PtNi nanodendrites prepared by a facile one-step reduction under ultrasonic irradiation at room temperature, exhibited a substantial catalytic activity towards glucose oxidation reaction at different pH values relative to a commercial Pt/C catalyst.