A highly sensitive hydrogen peroxide amperometric sensor based on MnO2-modified vertically aligned multiwalled carbon nanotubes

Rapid measurement of bacterial contamination in water: A catalase responsive-electrochemical sensor

The present study describes the development of a potentiometric sensor for microbial monitoring in water based on catalase activity. The sensor comprises a MnO2-modified electrode that responds linearly to hydrogen peroxide (H2O2) from 0.16 M to 3.26 M. The electrode potential drops when the H2O2 solution is spiked with catalase or catalase-producing microorganisms that decompose H2O2. The sensor is responsive to different bacteria and their catalase activities. The electrochemical sensor exhibits a lower limit of detection (LOD) for Escherichia coli at 11 CFU/ml, Citrobacter youngae at 12 CFU/ml, and Pseudomonas aeruginosa at 23 CFU/ml. The sensor shows high sensitivity at 3.49, 3.02, and 4.24 mV/cm2dec for E. coli, C. youngae, and P. aeruginosa, respectively. The abiotic sensing electrode can be used multiple times without changing the response potential (up to 100 readings) with a shelf-life of over six months. The response time is a few seconds, with a total test time of 5 min. Additionally, the sensor effectively tested actual samples (drinking and grey water), which makes it a quick and reliable sensing tool. Therefore, the study offers a promising water monitoring tool with high sensitivity, stability, good detection limit, and minimum interference from other water contaminants.

Facile preparation of MnO2-TiO2 nanotube arrays composite electrode for electrochemical detection of hydrogen peroxide

The MnO₂-TNTA composite electrodes were obtained through depositing MnO₂ into TiO₂ nanotube arrays (TNTA) by successive ionic layer adsorption reaction (SILAR) and subsequent hydrothermal method. The MnO₂-TNTA nanocomposites were used as electrochemical sensors for the detection of hydrogen peroxide (H₂O₂). The preparation conditions of MnO₂-TNTA electrodes and test conditions affect the electrochemical detection performance significantly. The optimal conditions are listed as follows: the number of SILAR cycles, 6 times; KMnO₄ solution temperature, 50 °C; supporting electrolyte, 0.5 M NaOH. Under these conditions, the MnO₂-TNTA electrode exhibits the best performance for detecting H₂O₂. The optimized MnO₂-TNTA electrode has a minimum detection limit of 0.6 μM (S/N = 3) and a linear range of 5 μM ∼ 13 mM, which is much superior to the previously-reported electrodes. Moreover, the optimized MnO₂-TNTA electrode possesses high selectivity, excellent stability and good reproducibility in the detection of H₂O₂. When used in the determination of H₂O₂ content in actual samples including disinfectant and milk, it also shows good accuracy, ideal recovery (96.00% ∼ 102.67%) and high precision (RSD < 4.0%).

Vertically Aligned Carbon Nanotubes as a Unique Material for Biomedical Applications

Vertically aligned carbon nanotubes (VACNTs), a unique classification of CNT, highly oriented and normal to the respective substrate, have been heavily researched over the last two decades. Unlike randomly oriented CNT, VACNTs have demonstrated numerous advantages making it an extremely desirable nanomaterial for many biomedical applications. These advantages include better spatial uniformity, increased surface area, greater susceptibility to functionalization, improved electrocatalytic activity, faster electron transfer, higher resolution in sensing, and more. This Review discusses VACNT and its utilization in biomedical applications particularly for sensing, biomolecule filtration systems, cell stimulation, regenerative medicine, drug delivery, and bacteria inhibition. Furthermore, comparisons are made between VACNT and its traditionally nonaligned, randomly oriented counterpart. Thus, we aim to provide a better understanding of VACNT and its potential applications within the community and encourage its utilization in the future.

A novel MnO-CrN nanocomposite based non-enzymatic hydrogen peroxide sensor

A MnO–CrN composite was obtained via the ammonolysis of the low-cost nitride precursors Cr(NO₃)₃·9H₂O and Mn(NO₃)₂·4H₂O at 800 °C for 8 h using a sol–gel method. The specific surface area of the synthesized powder was measured via BET analysis and it was found to be 262 m² g⁻¹. Regarding its application, the electrochemical sensing performance toward hydrogen peroxide (H₂O₂) was studied via applying cyclic voltammetry (CV) and amperometry (i–t) analysis. The linear response range was 0.33–15 000 μM with a correlation coefficient (R²) value of 0.995. Excellent performance toward H₂O₂ was observed with a limit of detection of 0.059 μM, a limit of quantification of 0.199 μM, and sensitivity of 2156.25 μA mM⁻¹ cm⁻². A short response time of within 2 s was achieved. Hence, we develop and offer an efficient approach for synthesizing a new cost-efficient material for H₂O₂ sensing.

A MnO–CrN composite was obtained via the ammonolysis of the low-cost nitride precursors Cr(NO₃)₃·9H₂O and Mn(NO₃)₂·4H₂O at 800 °C for 8 h using a sol–gel method.

Voltage-Switchable Biosensor with Gold Nanoparticles on TiO2 Nanotubes Decorated with CdS Quantum Dots for the Detection of Cholesterol and H2O2

A thin layer of gold nanoparticles (Au NPs) sputtered on cadmium sulfide quantum dots (CdS QDs) decorated anodic titanium dioxide nanotubes (TNTs) (Au/CdS QDs/TNTs) was fabricated and explored for the nonenzymatic detection of cholesterol and hydrogen peroxide (H₂O₂). Morphological studies of the sensor revealed the formation of uniform nanotubes decorated with a homogeneously dispersed CdS QDs and Au NPs layer. The electrochemical measurements showed an enhanced electrocatalytic performance with a fast electron transfer (∼2 s) between the redox centers of each analyte and electrode surface. The hybrid nanostructure (Au/CdS QDs/TNTs) electrode exhibited about a 6-fold increase in sensitivity for both cholesterol (10,790 μA mM^-1 cm^-2) and H₂O₂ (78,833 μA mM^-1 cm^-2) in analyses compared to the pristine samples. The hybrid electrode utilized different operational potentials for both analytes, which may lead to a voltage-switchable dual-analyte biosensor with a higher selectivity. The biosensor also demonstrated a good reproducibility, thermal stability, and increased shelf life. In addition, the clinical significance of the biosensor was tested for cholesterol and H₂O₂ in real blood samples, which showed maximum relative standard deviations of 1.8 and 2.3%, respectively. These results indicate that a Au/CdS QDs/TNTs-based hybrid nanostructure is a promising choice for an enzyme-free biosensor due to its suitable band gap alignment and higher electrocatalytic activities.

Smart materials-integrated sensor technologies for COVID-19 diagnosis

After the first case has appeared in China, the COVID-19 pandemic continues to pose an omnipresent threat to global health, affecting more than 70 million patients and leading to around 1.6 million deaths. To implement rapid and effective clinical management, early diagnosis is the mainstay. Today, real-time reverse transcriptase (RT)-PCR test is the major diagnostic practice as a gold standard method for accurate diagnosis of this disease. On the other side, serological assays are easy to be implemented for the disease screening. Considering the limitations of today's tests including lengthy assay time, cost, the need for skilled personnel, and specialized infrastructure, both strategies, however, have impediments to be applied to the resource-scarce settings. Therefore, there is an urgent need to democratize all these practices to be applicable across the globe, specifically to the locations comprising of very limited infrastructure. In this regard, sensor systems have been utilized in clinical diagnostics largely, holding great potential to have pivotal roles as an alternative or complementary options to these current tests, providing crucial fashions such as being suitable for point-of-care settings, cost-effective, and having short turnover time. In particular, the integration of smart materials into sensor technologies leverages their analytical performances, including sensitivity, linear dynamic range, and specificity. Herein, we comprehensively review major smart materials such as nanomaterials, photosensitive materials, electrically sensitive materials, their integration with sensor platforms, and applications as wearable tools within the scope of the COVID-19 diagnosis.

A Robust Flow-Through Platform for Organic Contaminant Removal

Achieving the greatest cleanup efficiency with minimal footprint remains a paramount goal of the water treatment industry. Toxic organic compounds threaten drinking water safety and require effective pretreatment. Hydroxyl radicals produced by the Fenton process (Fe2+/H2O2) destroy organic contaminants based on their strong oxidation potential. An upgraded reaction using solid catalysts, referred to as the Fenton-like process, was recently adopted to avoid the ferric sludge generation during the conventional Fenton process. However, most heterogeneous Fenton-like catalysts operate optimally at pH 3-5 and quite weakly in near-neutral water bodies. Here, we evaluate the feasibility of an electrolytically localized acid compartment (referred to as the Ella process) produced by electrochemical water splitting under flow-through conditions to facilitate the Fenton-like process. The Ella process boosts the activity of an immobilized iron oxychloride catalyst >10-fold, decomposing organic pollutants at a high flow rate. The robust performance in complex water bodies further highlights the promise of this platform.

Investigation on the role of the free radicals and the controlled degradation of chitosan under solution plasma process based on radical scavengers

This study investigated the role of various active species (OH, O, and H₂O₂) under solution plasma process (SPP) degradation based on the influence of different radical scavengers on the degradation effect and ESR spectra. The structures of oligochitosan with different radical scavengers were characterized by FT-IR, ¹H NMR, and XRD analysis. The results indicated that OH, O, and H₂O₂ played important roles in SPP degradation. The degradation effect of the O was even higher than that of the OH. The physical effects (e.g. UV light and shockwaves) of SPP method or Fenton's reaction might contribute to the degradation treatment. Furthermore, the different scavengers could adjust the degradation effect of the corresponding free radicals. FT-IR, ¹H NMR, and XRD analysis revealed that the primary chemical structure of chitosan was not changed by the scavengers. This study found that the controlled degradation by addition of a radical scavenger is feasible. Therefore, this study provided a straightforward analysis of the role of the free radicals and the controlled degradation of chitosan under SPP treatment, which will be beneficial to further develop SPP techniques for chitosan degradation.

Gold nanoparticles plated porous silicon nanopowder for nonenzymatic voltammetric detection of hydrogen peroxide

A voltammetric approach was developed for the selective and sensitive determination of hydrogen peroxide using Au plated porous silicon (PSi) nanopowder modified glassy carbon electrode (GCE). The AuNPs-PSi hybrid structure was synthesized via stain etching procedure followed by an immersion plating method to deposit AuNPs onto PSi via a simple galvanic displacement reaction with no external reducing agent to convert Au³⁺ to Au⁰. The as-fabricated AuNPs-PSi catalyst was successfully characterized by XRD, Raman, FTIR, XPS, SEM, TEM and EDS techniques. Well crystalline nature of the as-fabricated hybrid structure with AuNPs size ranging from 5 to 40 nm was observed. The specific surface area and total pore volume for both PSi and AuNPs plated PSi were evaluated using N₂ adsorption isotherm technique. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were applied to investigate the catalytic efficiency of AuNPs-PSi modified electrode compared to pure PSi/GCE and unmodified GCE. The sensing performance of the active material modified GCE was thoroughly examined with linear sweep voltammetry (LSV) and square wave voltammetry (SWV) techniques. The AuNPs-PSi/GCE exhibited a remarkable linear dynamic range between 2.0 and 13.81 mM (for LSV) and 0.5-6.91 mM for (SWV) with high sensitivity and low detection limit of 10.65 μAmM^-1cm^-2 and 14.84 μM for LSV, whereas 10.41 μAmM^-1cm^-2 and 15.16 μM using SWV techniques, respectively. The fabricated sensor electrode showed excellent anti-interfering ability in the presence of several common biomolecules as well as demonstrated good operational stability and reproducibility with low relative standard deviation. Moreover, the modified electrode showed acceptable recovery of H₂O₂ in a real sample analysis. Thus, the developed AuNPs-PSi hybrid nanomaterial represents an excellent electrocatalyst for the efficient detection and quantification of H₂O₂ by the electrochemical approach.

A sensitive non-enzymatic electrochemical sensor based on acicular manganese dioxide modified graphene nanosheets composite for hydrogen peroxide detection

In this work, a novel manganese dioxide-graphene nanosheets (MnO₂-GNSs) composite was synthesized by a facile one-step hydrothermal method, in which manganese dioxide (MnO₂) was fabricated by hydrothermal reduction of KMnO₄ with GNSs. The structure and morphology of MnO₂-GNSs composite were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). A sensitive non-enzymatic electrochemical sensor based on MnO₂-GNSs composite for the detection of low concentration hydrogen peroxide (H₂O₂) was fabricated. The electrochemical properties of MnO₂-GNSs composite modified glassy carbon electrode (MnO₂-GNSs/GCE) were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometry. The observations confirmed that the fabricated sensor exhibited high electrocatalytic activity for oxidation of H₂O₂ owing to the catalytic ability of MnO₂ particles and the conductivity of GNSs. Under the optimum conditions, the calibration curve was linear for the amperometric response versus H₂O₂ concentration over the range 0.5-350 μM with a low detection limit of 0.19 μM (S/N = 3) and high sensitivity of 422.10 μA mM^-1 cm^-2. The determination and quantitative analysis of H₂O₂ in antiseptic solution on MnO₂-GNSs/GCE exhibited percent recovery of 96.50%-101.22% with relative standard deviation (RSD) of 1.48%-4.47%. The developed MnO₂-GNSs/GCE might be a promising platform for the practical detection of H₂O₂ due to its prominent properties including excellent reproducibility, good anti-interference and repeatability.

A simple enzyme-free SERS sensor for the rapid and sensitive detection of hydrogen peroxide in food

A simple enzyme-free method based on surface-enhanced Raman scattering (SERS) was developed for the first time to detect H₂O₂ in food by etching a self-assembled film of silver nanoparticles (Ag NPs) on a glass substrate.

Self-Supported and Flexible Sulfur Cathode Enabled via Synergistic Confinement for High-Energy-Density Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the "shuttle effect" of the sulfur cathode, resulting in poor cyclic performance, is a big barrier for the development of Li-S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal-organic framework (MOF)-derived N-doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm^-2 ) and exhibit large specific capacities at different C-rates. Specially, an outstanding long-term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high-energy-density Li-S batteries.

Wireless bipotentiostat circuit for glucose and H2O2 interrogation

Here we present a cost-effective point-of-use wireless platform for the electrochemical detection of low concentrations of glucose and hydrogen peroxide (H₂O₂), simultaneously. The electrochemical system utilizes a dual sensor integrated with a portable bipotentiostat. The bipotentiostat hardware implements a basic designed that reduces the cost of construction and increase the affordability of the instrument, while providing similar functionality as the more expensive bench-top potentiostats. The bipotentiostat utilizes inexpensive components and common Ag/AgCl reference and platinum counter electrodes and two working electrodes, and it is designed to detect currents within the range of 20 uA - 7 mA. Additionally, the bipotentiostat is integrate with wireless module ESP8266 that interfaces with a smartphone to enable real-time monitoring and visualization of the analyte concentration levels. The results show that the selfdesigned bipotentiostat is capable of performing chronoamperometry and demonstrate an electrochemical detection system that is a portable alternative system for laboratory and point-of-use testing.

Electrospun CuO-ZnO nanohybrid: Tuning the nanostructure for improved amperometric detection of hydrogen peroxide as a non-enzymatic sensor

Hydrogen peroxide (H₂O₂) is a by-product of some biochemical processes which is catalyzed by enzymes such as glucose oxidase (GOx), cholesterol oxidase (ChoOx), etc and its overproduction in living cells can trigger cancer growth and various diseases. Therefore, H₂O₂ sensing is of great importance in the determination of diseases as well as industries and environmental health plans. We produced ZnO-CuO nanofibers by electrospinning method for non-enzymatic electrochemical H₂O₂ sensing. The sensing properties of the carbon paste electrode (CPE) modified with ZnO (0.3 wt%)/CuO (0.7 wt%) nanofibers (named as ZnO3-CuO7) for detection of H₂O₂ were explored in phosphate-buffered saline (PBS) at pH ∼ 7.4 solution. The ZnO3-CuO7 nanofiber exhibited the lowest charge transfer resistance and the highest electrocatalytic performance among other modified electrodes for detection of H₂O₂ and considered as an optimized sample. The effect of scan rate and H₂O₂ concentration in the reduction process were also investigated by cyclic voltammetry (CV) and the mechanism for the electrochemical reaction of H₂O₂ at the surface of the optimized electrode was studied. The diffusion coefficient of H₂O₂ and the catalytic rate constant were evaluated by chronoamperometry as 1.65 × 10^-5 cm² s^-1 and 6 × 10³ cm³ mol^-1 s^-1, respectively. Furthermore, amperometric detection of H₂O₂ with a low detection limit of 2.4 µM and a wide linear range of 3 to 530 µM were obtained. Meanwhile, the optimized electrode displayed no recognizable response towards some biomolecules such as ascorbic acid, uric acid, dopamine and glucose. The obtained results confirmed that the modified electrode shows high sensitivity and selectivity as a H₂O₂ biosensor with improved reproducibility and stability.

Simple sonochemical synthesis of novel grass-like vanadium disulfide: A viable non-enzymatic electrochemical sensor for the detection of hydrogen peroxide

Design and fabrication of novel inorganic nanomaterials for the low-level detection of food preservative chemicals significant is of interest to the researchers. In the present work, we have developed a novel grass-like vanadium disulfide (GL-VS₂) through a simple sonochemical method without surfactants or templates. As-prepared VS₂ was used as an electrocatalyst for reduction of hydrogen peroxide (H₂O₂). The crystalline nature, surface morphology, elemental compositions and binding energy of the as-prepared VS₂ were analyzed by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The electrochemical studies show that the GL-VS₂ modified glassy carbon electrode (GL-VS₂/GCE) has a superior electrocatalytic activity and lower-reduction potential than the response observed for unmodified GCE. Furthermore, the GL-VS₂/GCE displayed a wide linear response range (0.1-260 μM), high sensitivity (0.23 μA μM^-1 cm^-2), lower detection limit (26 nM) and excellent selectivity for detection of H₂O₂. The fabricated GL-VS₂/GCE showed excellent practical ability for detection of H₂O₂ in milk and urine samples, revealing the real-time practical applicability of the sensor in food contaminants.

Low-cost and disposable sensors for the simultaneous determination of coenzyme Q10 and α-lipoic acid using manganese (IV) oxide-modified screen-printed graphene electrodes

In this work, for the first time, manganese (IV) oxide-modified screen-printed graphene electrodes (MnO₂/SPGEs) were developed for the simultaneous electrochemical detection of coenzyme Q10 (CoQ10) and α-lipoic acid (ALA). This sensor exhibits attractive benefits such as simplicity, low production costs, and disposability. Cyclic voltammetry (CV) was used to characterize the electrochemical behavior of the analyte and investigate the capacitance and electroactive surface area of the unmodified and modified electrode surfaces. The electrochemical behavior of CoQ10 and ALA on MnO₂/SPGEs was also discussed. Additionally, square wave anodic stripping voltammetry (SWASV) was used for the quantitative determination of CoQ10 and ALA. Under optimal conditions, the obtained signals are linear in the concentration range from 2.0 to 75.0 μg mL^-1 for CoQ10 and 0.3-25.0 μg mL^-1 for ALA. The low limits of detection (LODs) were found to be 0.56 μg mL^-1 and 0.088 μg mL^-1 for CoQ10 and ALA, respectively. Moreover, we demonstrated the utility and applicability of the MnO₂/SPGE sensor through simultaneous measurements of CoQ10 and ALA in dietary supplements. The sensor provides high accuracy measurements, exhibiting its high potential for practical applications.

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.

A novel and simple cell-based electrochemical biosensor for evaluating the antioxidant capacity of Lactobacillus plantarum strains isolated from Chinese dry-cured ham

The analysis of antioxidants in foodstuffs has become an active area of research, leading to the recent development of numerous methods for assessing antioxidant capacity. Here we described the fabrication and validation of a novel and simple cell-based electrochemical biosensor for this purpose. The biosensor is used to assess the antioxidant capacity of cell-free extracts from Lactobacillus plantarum strains isolated from Chinese dry-cured ham. The biosensor relies on the determination of cellular reactive oxygen species (ROS) (the flux of H₂O₂ released from RAW 264.7 macrophage cells) to indirectly assess changes in intracellular oxidative stress level as influenced by L. plantarum strains. A one-step acidified manganese dioxide (a-MnO₂) modified gold electrode (GE) was used to immobilize RAW 264.7 macrophage cells, which were then encapsulated in a 3D cell culture system consisting of alginate/ graphene oxide (NaAlg/GO). The biosensor exhibited a rapid and sensitive response for the detection of H₂O₂ released from RAW264.7 cells. The detection limit was 0.02μM with a linear response from 0.05μM to 0.85μM and the biosensor was shown to have good stability and outstanding repeatability. This technique was then used for evaluating the antioxidant ability of extracts from L. plantarum NJAU-01. According to the electrochemical investigations and assays of SEM, TEM, and ROS, these cell-free extracts effectively reduced the oxidative stress levels in RAW264.7 cells under external stimulation. Extracts from L. plantarum strains at a dose of 10¹⁰CFU/mL showed the highest antioxidant activities with a relative antioxidant capacity (RAC) rate of 88.94%. Hence, this work provides a simple and efficient electrochemical biosensing platform based on RAW264.7 cells for fast, sensitive and quantitative assessment of antioxidant capacity of L. plantarum strains. The method demonstrates its potential for rapid screening for evaluating antioxidant properties of samples.

A novel H2O2 biosensor based on three-dimensional micro/nano-biointerfaces

A novel H₂O₂ biosensor was first reported to directly grow living cells on three-dimensional micro/nano-biointerfaces to promote electrochemical performance.

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration.

Genetically Engineered Phage-Templated MnO2 Nanowires: Synthesis and Their Application in Electrochemical Glucose Biosensor Operated at Neutral pH Condition

To conveniently obtain one-dimensional MnO2 nanowires (NWs) with controlled structure and unique properties for electron transfer, the genetically engineered M13 phages were used as templates for precise nucleation and growth of MnO2 crystals in filamentous phage scaffolds, via the spontaneous oxidation of Mn(2+) in alkaline solution. It was found that the morphology of NWs could be tailored by the surface charge of M13 mutants. MnO2 crystals were uniformly distributed on the surface of negatively charged tetraglutamate-fused phage (M13-E4), significantly different from irregular MnO2 agglomeration on the weakly negatively charged wild-type phage and positively charged tetraarginine-fused phage. The as-synthesized M13-E4@MnO2 NWs could catalyze the electro-oxidation of H2O2 at neutral pH. To demonstrate the superiority of the electrocatalytic activity in the solution containing plenty of chloride ions at neutral pH, both glucose oxidase and as-prepared MnO2 NWs were used for fabricating the glucose biosensor. The proposed biosensor showed a wide linear range (5 μM to 2 mM glucose), a low limit of detection of 1.8 μM glucose (S/N = 3), good interassay and intra-assay reproducibility and satisfactory storage stability. Due to the superiorities of synthesis and electrochemical performance, the as-prepared MnO2 NWs are promising for applications in electrocatalysis, electrochemical sensor, and supercapacitor.

Direct growth of MnOOH nanorod arrays on a carbon cloth for high-performance non-enzymatic hydrogen peroxide sensing

Novel MnOOH nanorod arrays directly growing on a flexible carbon cloth substrate (MnOOH/CC) is first synthesized through a facile hydrothermal technique and utilized as an electrocatalyst for non-enzymatic detection of hydrogen peroxide. The as-prepared MnOOH nanorods are uniformly distributed on the carbon cloth with a 3D porous network structure, which provides a high specific surface area and numerous electroactive sites. The electrode based on the carbon cloth-supported MnOOH nanorod arrays exhibits a higher sensitivity (692.42 μA mM(-1) cm(-2)) and a wider linear range (20 μm-9.67 mM) with a detection limit of 3.2 μM (S/N = 3) compared with the electrode based on the rigid graphite substrate supported the random distributed MnOOH nanorods. Further, the MnOOH/CC possesses an outstanding flexibility and can conveniently be assembled into the required shape for a specific use, thus the arc-shaped MnOOH/CC electrodes are fabricated whose electrocatalytic activity toward the hydrogen peroxide reduction remains nearly unchanged in comparison with the unbent state. Due to its excellent sensitivity, reproducibility, anti-interference and stability, the electrode based on the carbon cloth-supported MnOOH nanorod arrays is believed to be promising for applications in high efficiency flexible hydrogen peroxide sensing.

Redox mediated synthesis of hierarchical Bi2O3/MnO2 nanoflowers: a non-enzymatic hydrogen peroxide electrochemical sensor

Redox mediated synthesis of Bi₂O₃/MnO₂ nanoflowers for efficient electrochemical sensing of hydrogen peroxide down to 0.05 μM.

Three-dimensional macro-structures of two-dimensional nanomaterials

This review summarizes the recent progress and efforts in the synthesis, structure, properties, and applications of three-dimensional macro-structures of two-dimensional nanomaterials.

A novel δ-MnO2 with carbon nanotubes nanocomposite as an enzyme-free sensor for hydrogen peroxide electrosensing

We have reported the synthesis and application of carbon nanotubes supported δ-MnO₂ (δ-MnO₂/CNTs) nanocomposite as enzyme-free sensor for the detection of H₂O₂, where δ-MnO₂ serves as the catalytic center and CNTs as the highly conductive base.

Photo-reduction assisted synthesis of MnO2/reduced graphene oxide/P25 for electrochemical detection of hydrogen peroxide

MnO₂/RGO/P25 nanocomposites were synthesized with a photo-reduction approach for electrochemical detection of H₂O₂.