A highly sensitive nonenzymatic glucose sensor based on multi-walled carbon nanotubes decorated with nickel and copper nanoparticles

Effect of Carbon Layer Thickness on the Electrocatalytic Oxidation of Glucose in a Ni/BDD Composite Electrode

High-performance non-enzymatic glucose sensor composite electrodes were prepared by loading Ni onto a boron-doped diamond (BDD) film surface through a thermal catalytic etching method. A carbon precipitate with a desired thickness could be formed on the Ni/BDD composite electrode surface by tuning the processing conditions. A systematic study regarding the influence of the precipitated carbon layer thickness on the electrocatalytic oxidation of glucose was conducted. While an oxygen plasma was used to etch the precipitated carbon, Ni/BDD-based composite electrodes with the precipitated carbon layers of different thicknesses could be obtained by controlling the oxygen plasma power. These Ni/BDD electrodes were characterized by SEM microscopies, Raman and XPS spectroscopies, and electrochemical tests. The results showed that the carbon layer thickness exerted a significant impact on the resulting electrocatalytic performance. The electrode etched under 200 W power exhibited the best performance, followed by the untreated electrode and the electrode etched under 400 W power with the worst performance. Specifically, the electrode etched under 200 W was demonstrated to possess the highest sensitivity of 1443.75 μA cm-2 mM-1 and the lowest detection limit of 0.5 μM.

Cu and Ni Co-sputtered heteroatomic thin film for enhanced nonenzymatic glucose detection

In this work, we report a wafer-scale and chemical-free fabrication of nickel (Ni) and copper (Cu) heteroatomic Cu–Ni thin films using RF magnetron sputtering technique for non-enzymatic glucose sensing application. The as-prepared wafer-scale Cu–Ni thin films exhibits excellent electrocatalytic activity toward glucose oxidation with a 1.86 μM detection limit in the range of 0.01 mM to 20 mM range. The Cu–Ni film shows 1.3- and 5.4-times higher glucose oxidation activity in comparison to the Cu and Ni electrodes, respectively. The improved electrocatalytic activity is attributed to the synergistic effect of the bimetallic catalyst and high density of grain boundaries. The Cu–Ni electrodes also possessed excellent anti-interference characteristics. These results indicate that Cu–Ni heteroatomic thin film can be a potential candidate for the development of non-enzymatic glucose biosensor because of its chemical free synthesis, excellent reproducibility, reusability, and long-term stability.

Recent advances in the potential applications of luminescence-based, SPR-based, and carbon-based biosensors

Abstract

The need for biosensors has evolved in the detection of molecules, diseases, and pollution from various sources. This requirement has headed to the development of accurate and powerful equipment for analysis using biological sensing component as a biosensor. Biosensors have the advantage of rapid detection that can beat the conventional methods for the detection of the same molecules. Bio-chemiluminescence-based sensors are very sensitive during use in biological immune assay systems. Optical biosensors are emerging with time as they have the advantage that they act with a change in the refractive index. Carbon nanotube-based sensors are another area that has an important role in the biosensor field. Bioluminescence gives much higher quantum yields than classical chemiluminescence. Electro-generated bioluminescence has the advantage of miniature size and can produce a high signal-to-noise ratio and the controlled emission. Recent advances in biological techniques and instrumentation involving fluorescence tag to nanomaterials have increased the sensitivity limit of biosensors. Integrated approaches provided a better perspective for developing specific and sensitive biosensors with high regenerative potentials. This paper mainly focuses on sensors that are important for the detection of multiple molecules related to clinical and environmental applications.

Key points

• The review focusses on the applications of luminescence-based, surface plasmon resonance-based, carbon nanotube-based, and graphene-based biosensors

• Potential clinical, environmental, agricultural, and food industry applications/uses of biosensors have been critically reviewed

• The current limitations in this field are discussed, as well as the prospects for future advancement

Glucose determination using amperometric non-enzymatic sensor based on electroactive poly(caffeic acid)@MWCNT decorated with CuO nanoparticles

A novel non-enzymatic glucose sensor based on poly(caffeic acid)@multi-walled carbon nanotubes decorated with CuO nanoparticles (PCA@MWCNT-CuO) was developed. The described approach involves the complexation/accumulation of Cu(II) on PCA@MWCNT followed by electrochemical CuO deposition in an alkaline electrolyte. The morphology and surface characteristics of the nanomaterial were determined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), Raman spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). A hybrid-support sensor device was then developed to assess the glucose concentration in different solutions. The sensitivity of the electrode is 2412 μA mM^-1 cm^-2. The electrode exhibited a broad linear range of 2 µM to 9 mM and a low limit of detection (LOD) of 0.43 µM (relative standard deviation, RSD = 2.3%) at + 0.45 V vs Ag/AgCl. The excellent properties obtained for glucose detection were most likely due to the synergistic effect of the combination of individual components: poly(caffeic acid), MWCNTs, and CuO. Good accuracy and high precision were demonstrated for quantifying glucose concentrations in human serum and blood samples (the recovery ranged from 95.0 to 99.5%). The GC/PCA@MWCNT-CuO sensor represents a novel, simple, and low-cost approach to the fabrication of devices for amperometric sensing of glucose.

Non-Enzymatic Detection of Glucose in Neutral Solution Using PBS-Treated Electrodeposited Copper-Nickel Electrodes

Transition metals have been explored extensively for non-enzymatic electrochemical detection of glucose. However, to enable glucose oxidation, the majority of reports require highly alkaline electrolytes which can be damaging to the sensors and hazardous to handle. In this work, we developed a non-enzymatic sensor for detection of glucose in near-neutral solution based on copper-nickel electrodes which are electrochemically modified in phosphate-buffered saline (PBS). Nickel and copper were deposited using chronopotentiometry, followed by a two-step annealing process in air (Step 1: at room temperature and Step 2: at 150 °C) and electrochemical stabilization in PBS. Morphology and chemical composition of the electrodes were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cyclic voltammetry was used to measure oxidation reaction of glucose in sodium sulfate (100 mM, pH 6.4). The PBS-Cu-Ni working electrodes enabled detection of glucose with a limit of detection (LOD) of 4.2 nM, a dynamic response from 5 nM to 20 mM, and sensitivity of 5.47 ± 0.45 μA cm-2/log10(mole.L-1) at an applied potential of 0.2 V. In addition to the ultralow LOD, the sensors are selective toward glucose in the presence of physiologically relevant concentrations of ascorbic acid and uric acid spiked in artificial saliva. The optimized PBS-Cu-Ni electrodes demonstrate better stability after seven days storage in ambient compared to the Cu-Ni electrodes without PBS treatment.

A Highly Sensitive Electrochemical Glucose Sensor Based on Room Temperature Exfoliated Graphite-Derived Film Decorated with Dendritic Copper

An ultrasensitive enzyme-free glucose sensor was facilely prepared by electrodepositing three-dimensional dendritic Cu on a room temperature exfoliated graphite-derived film (RTEG-F). An excellent electrocatalytic performance was demonstrated for glucose by using Cu/RTEG-F as an electrode. In terms of the high conductivity of RTEG-F and the good catalytic activity of the dendritic Cu structures, the sensor demonstrates high sensitivities of 23.237 mA/mM/cm², R² = 0.990, and 10.098 mA/mM/cm², R² = 0.999, corresponding to the concentration of glucose ranging from 0.025 mM to 1.0 mM and 1.0 mM to 2.7 mM, respectively, and the detection limit is 0.68 μM. In addition, the Cu/RTEG-F electrode demonstrates excellent anti-interference to interfering species and a high stability. Our work provides a new idea for the preparation of high-performance electrochemical enzyme-free glucose sensor.

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.

Facile synthesis of Cu/Co-ZIF nanoarrays for non-enzymatic glucose detection

Cu/Co-ZIF nanoflake arrays on carbon cloth are fabricated by controlling the introducing of Cu²⁺ions during the growth of Co-ZIF. The Cu/Co-ZIF-20 electrode prepared with 20 mM Cu²⁺possesses large electrochemically active surface area and bimetallic active sites, which can be revealed by cyclic voltammetry tests. The amperometrici-tmeasurements demonstrate that the Cu/Co-ZIF-20 electrode displays a wide linear range from 0.05 mM to 6.0 mM, and a high sensitivity of 1.03 mA mM^-1cm^-2. Good selectivity, repeatability and practical applicability indicate its promising application in enzyme-free glucose sensing.

Micro–nanoarchitectures of electrodeposited Ni–ITO nanocomposites on copper foil as electrocatalysts for the oxygen evolution reaction

A simple conventional three electrodes system was used for the preparation of Ni and Ni–ITO nanocomposites as an electrocatalyst for oxygen evolution reaction.

Electrochemical Non-Enzymatic Detection of Glucose Based on 3D Electroformed Copper on Ni Foam Nanostructures

Despite the fact that the electrochemical biosensors based on glucose oxidase represent the golden standard for the management of diabetes, the elaboration of nonenzymatic sensors became extensively studied as an out-of-the-box concept that aims to simplify the existing approach. An important point of view is represented by the low price of the sensing device that has positive effects for both end-users and healthcare systems. The enzyme-free sensors based on low-cost materials such as transition metals have similar analytical properties to the commercial ones while eliminating the issues associated with the presence of the enzyme, such as the stability issues and limited shelf-life. The development of nanoporous nanomaterials for biomedical applications and electrocatalysis was referred to as an alternative to the conventional methods due to their enlarged area, electrical properties, ease of functionalization and not least to their low cost. Herein, we report the development of an electrochemical nonenzymatic sensor for glucose based on 3D copper nanostructures with Ni foams as promotor of the enhanced nanoporous morphology. The sensors were successfully tested in the presence of the designated target, even in the presence of common interference agents found in biological samples.

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.

A Cu2O/Cu/carbon cloth as a binder-free electrode for non-enzymatic glucose sensors with high performance

An electrode prepared via potentiostatic electrochemical deposition exhibits a 60 nM detection limit and a 1 linear range of 1 to 1555 μM.

Nickel oxide decorated MoS2nanosheet-based non-enzymatic sensor for the selective detection of glucose

Understanding blood glucose levels in our body can be a key part in identifying and diagnosing prediabetes. Herein, nickel oxide (NiO) decorated molybdenum disulfide (MoS₂) nanosheets have been synthesized via a hydrothermal process to develop a non-enzymatic sensor for the detection of glucose. The surface morphology of the NiO/MoS₂ nanocomposite was comprehensively investigated by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis. The electro-catalytic activity of the as-prepared NiO/MoS₂ nanocomposite towards glucose oxidation was investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and amperometry in 0.1 M NaOH. The NiO/MoS₂ nanocomposite-based sensor showed outstanding electrocatalytic activity for the direct electro-oxidation of glucose due to it having more catalytic active sites, good conductivity, excellent electron transport and high specific surface area. Meanwhile, the NiO/MoS₂ modified glassy carbon electrode (GCE) showed a linear range of glucose detection from 0.01 to 10 mM by amperometry at 0.55 V. The effect of other common interferent molecules on the electrode response was also tested using alanine, l-cysteine, fructose, hydrogen peroxide, lactose, uric acid, dopamine and ascorbic acid. These molecules did not interfere in the detection of glucose. Moreover, this NiO/MoS₂/GCE sensor offered rapid response (2 s) and a wide linear range with a detection limit of 1.62 μM for glucose. The reproducibility, repeatability and stability of the sensor were also evaluated. The real application of the sensor was tested in a blood serum sample in the absence and presence of spiked glucose and its recovery values (96.1 to 99.8%) indicated that this method can be successfully applied to detect glucose in real samples.

This study reported that NiO/MoS₂ based nanocomposite can be used as an electrocatalytic material to detect glucose with high selectivity in a blood serum.

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.

Carbon Nanotube Chemical Sensors

Carbon nanotubes (CNTs) promise to advance a number of real-world technologies. Of these applications, they are particularly attractive for uses in chemical sensors for environmental and health monitoring. However, chemical sensors based on CNTs are often lacking in selectivity, and the elucidation of their sensing mechanisms remains challenging. This review is a comprehensive description of the parameters that give rise to the sensing capabilities of CNT-based sensors and the application of CNT-based devices in chemical sensing. This review begins with the discussion of the sensing mechanisms in CNT-based devices, the chemical methods of CNT functionalization, architectures of sensors, performance parameters, and theoretical models used to describe CNT sensors. It then discusses the expansive applications of CNT-based sensors to multiple areas including environmental monitoring, food and agriculture applications, biological sensors, and national security. The discussion of each analyte focuses on the strategies used to impart selectivity and the molecular interactions between the selector and the analyte. Finally, the review concludes with a brief outlook over future developments in the field of chemical sensors and their prospects for commercialization.

High-performance non-enzymatic glucose sensor by hierarchical flower-like nickel(II)-based MOF/carbon nanotubes composite

A hierarchical three-dimensional flower-like nickel(II)-terephthalic acid (Ni(TPA)) metal-organic framework (MOF) was synthesized through a simple solvothermal method. Then the single-walled carbon nanotubes (SWCNT) were doped with the synthesized Ni(TPA) MOF by the ultrasonic method to improve the chemical stability and the electrochemical activity of the MOF. To explore the potential application of the nanocomposite, the Ni(TPA)-SWCNT modified glassy carbon electrode was prepared and used as a non-enzymatic electrochemical sensor for glucose. The results show that the nanocomposite demonstrates remarkably higher electrochemical response as well as stronger electrocatalytic activity toward glucose oxidation, in comparison with the single-component of Ni(TPA) and SWCNT. The Ni(TPA)-SWCNT modified electrode exhibits outstanding performance including excellent selectivity, wide linear range from 20 μM to 4.4 mM, low detection limit of 4.6 μM, and fast response (<5 s) for glucose detection. For glucose analysis in real serum samples, the developed sensor reveals a good agreement with the automatic biochemical analyzer, with the deviation rate of 0-6.7% and correlation coefficient (r) of 0.9940 (n = 20, P < 0.0001), indicating high accuracy and great potential of the sensor for practical application in fast analysis of glucose.

A CuNi/C Nanosheet Array Based on a Metal-Organic Framework Derivate as a Supersensitive Non-Enzymatic Glucose Sensor

Bimetal catalysts are good alternatives for non-enzymatic glucose sensors owing to their low cost, high activity, good conductivity, and ease of fabrication. In the present study, a self-supported CuNi/C electrode prepared by electrodepositing Cu nanoparticles on a Ni-based metal-organic framework (MOF) derivate was used as a non-enzymatic glucose sensor. The porous construction and carbon scaffold inherited from the Ni-MOF guarantee good kinetics of the electrode process in electrochemical glucose detection. Furthermore, Cu nanoparticles disturb the array structure of MOF derived films and evidently enhance their electrochemical performances in glucose detection. Electrochemical measurements indicate that the CuNi/C electrode possesses a high sensitivity of 17.12 mA mM^-1 cm^-2, a low detection limit of 66.67 nM, and a wider linearity range from 0.20 to 2.72 mM. Additionally, the electrode exhibits good reusability, reproducibility, and stability, thereby catering to the practical use of glucose sensors. Similar values of glucose concentrations in human blood serum samples are detected with our electrode and with the method involving glucose-6-phosphate dehydrogenase; the results further demonstrate the practical feasibility of our electrode.

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.

Cu@Ni core–shell nanoparticles/reduced graphene oxide nanocomposites for nonenzymatic glucose sensor

Cu@Ni core–shell nanoparticle decorated reduced graphene oxide nanocomposites are prepared and further employed as a novel sensing material for fabricating a sensitive nonenzymatic glucose sensor with excellent performance for glucose.

Glucose sensing on graphite screen-printed electrode modified by sparking of copper nickel alloys

Electric spark discharge was employed as a green, fast and extremely facile method to modify disposable graphite screen-printed electrodes (SPEs) with copper, nickel and mixed copper/nickel nanoparticles (NPs) in order to be used as nonenzymatic glucose sensors. Direct SPEs-to-metal (copper, nickel or copper/nickel alloys with 25/75, 50/50 and 75/25wt% compositions) sparking at 1.2kV was conducted in the absence of any solutions under ambient conditions. Morphological characterization of the sparked surfaces was performed by scanning electron microscopy, while the chemical composition of the sparked NPs was evaluated with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The performance of the various sparked SPEs towards the electro oxidation of glucose in alkaline media and the critical role of hydroxyl ions were evaluated with cyclic voltammetry and kinetic studies. Results indicated a mixed charge transfer- and hyroxyl ion transport-limited process. Best performing sensors fabricated by Cu/Ni 50/50wt% alloy showed linear response over the concentration range 2-400μM glucose and they were successfully applied to the amperometric determination of glucose in blood. The detection limit (S/N 3) and the relative standard deviation of the method were 0.6µM and <6% (n=5, 2µM glucose), respectively. Newly devised sparked Cu/Ni graphite SPEs enable glucose sensing with distinct advantages over existing glucose chemical sensors in terms of cost, fabrication simplicity, disposability, and adaptation of green methods in sensor's development.