Electrocatalytic Reduction Of H2O2 Research Articles

Selecting effective eletrocatalyst from Cu single-atoms and nanoparticles for realizing highly sensitive electrochemical sensing of glucose and H2O2.

Which is more suitable as a sensing material between metal single-atoms and nanoparticles? Herein, electrocatalytic behaviors of copper single-atoms (Cu SAs) and copper nanoparticles (CuNPs) toward H2O2 reduction and glucose oxidation were studied. Surprisingly, the electrocatalytic activity of Cu SAs and CuNPs showed significant differences in H2O2 reduction and glucose oxidation. Compared with CuNPs, Cu SAs exhibit outstanding activity in the electrocatalytic reduction of H2O2 but exhibit weak activity in the electrocatalytic oxidation of glucose. On the contrary, CuNPs exhibit excellent activity in the electrochemical oxidation of glucose but have very weak electrocatalytic activity towards H2O2 reduction. DFT results show that H2O2 reduction is more favourable with Cu SAs; however, the electrochemical oxidation of glucose with CuNPs requires overcoming much lower energy barriers than that with Cu SAs. This study proves that both metal single-atoms and nanoparticles are not omnipotent, which provides ideas for constructing highly active sensing materials.

Structural Phase Transition of Mo2C for Enhancing Electrochemical Sensing of Hydrogen Peroxide

Regulating the electrocatalytic activity of metal carbides is the key to achieving highly sensitive electrochemical sensing. Molybdenum carbide (Mo2C) nanoparticles were anchored on the surface of nitrogen doped carbon nanomaterials (NC) through polymerization and calcination. By adjusting the calcination conditions, the crystal phase structure of Mo2C nanoparticles was successfully regulated, and two kinds of Mo2C nanoparticles with different crystal phase structure were obtained. The effect of the crystal structure of Mo2C on the electrocatalytic reduction of H2O2 was investigated. The results show that Mo2C with the hexagonal structure (H-Mo2C) has higher electrocatalytic activity for H2O2 reduction reaction, and the sensor based on H-Mo2C/NC could detect H2O2 in a wide linear range from 0.02 mM to 7.1 mM with a high sensitivity of 282.9 μA·mM−1·cm−2 and a low detection limit of 0.45 μM (S/N = 3). Moreover, the sensor can also accurately determine the content of H2O2 in disinfectant and milk samples. This study demonstrated Mo2C with the hexagonal structure as an effective sensing material for H2O2.

Two new Keggin-based copper-organic complexes constructed from pyrazole derivatives: Syntheses, structures and catalytic properties

By regulating the initial reactant molar ratio, two new Keggin-based copper-organic complexes formulated as [Cu2(H2O)(L)2(HL)2](HPMo12O40)·2H2O (1) and [Cu4L4(H2O)2](H3PMo12O40) (2) (HL = 1-(4-carboxylbenzyl)-3-(pyrazine-2-yl)]pyrazole) have been synthesized triumphantly under hydrothermal conditions. Single crystal X-ray diffraction analyses show that compound 1 is a 3D supramolecular structure constructed by 1D metal–organic chains [Cu2(H2O)(L)2(HL)2]n2n+ and PMo12 anions via hydrogen bonds. Compound 2 is a 2D [Cu2L2(H2O)]n coordination polymeric network containing left and right helical chains. By hydrogen bonding interactions between adjacent [Cu2L2(H2O)]n networks and PMo12 anions, the 2D network extends to a 3D supramolecular structure. The two compounds can not only photocatalytic degrade methylene blue and Rhodamine B, but also have electrocatalytic reduction of H2O2, BrO3- and NO2– and oxidation of ascorbic acid. Moreover, their electrochemical sensing properties have also been studied. These results suggest compounds 1 and 2 can be used as multifunctional materials.

Ultrasensitive Nonenzymatic Real-Time Hydrogen Peroxide Monitoring Using Gold Nanoparticle-Decorated Titanium Dioxide Nanotube Electrodes.

An amperometric enzyme-free hydrogen peroxide (H2O2) sensor was developed by catalytically stabilizing active gold nanoparticles (Au NPs) of 4-5 nm on a porous titanium dioxide nanotube (TiO2 NTs) electrode. The Au NPs were homogeneously distributed on anatase TiO2 NTs with an outer diameter of ~102 nm, an inner diameter of ~60 nm, and a wall of thickness of ~40 nm. The cyclic voltammogram of the composite electrode showed a pair of redox peaks characterizing the electrocatalytic reduction of H2O2. The entrapping of Au NPs on TiO2 NTs prevented aggregation and facilitated good electrical conductivity and electron transfer rate, thus generating a wide linear range, a low detection limit of ~104 nM, and high sensitivity of ~519 µA/mM, as well as excellent selectivity, reproducibility, repeatability, and stability over 60 days. Furthermore, excellent recovery and relative standard deviation (RSD) were achieved in real samples, which were tap water, milk, and Lactobacillus plantarum bacteria, thereby verifying the accuracy and potentiality of the developed nonenzymatic sensor.

Proton-Conductive and Electrochemical-Sensitive Sensing Behavior of a New Mn(II) Chain Coordination Polymer

In this work, a novel Mn(II) chain coordination polymer (Mn-CP), {[Mn(iip)(2bbpum)0.5(H2O)3]·2H2O}n [H2iip = 5-iodoisophthalic acid, 2bbpum = N,N′-bis(2-pyridinemethyl)oxamide] was synthesized under ambient conditions. Mn-CP further assembles into a 3D supramolecular architecture through hydrogen bonds, halogen bonds, and ππ stacking interactions. The composite Mn-CP/nafion membrane has low activation energy for proton transfer, which results in its temperature-insensitive proton conductivity. The cyclic voltammetry demonstrates that the Mn-CP electrode (Mn-CP/GCE) shows quite different redox properties in 0.1 M H2SO4 and 0.1 M PBS aqueous solutions. The Mn-CP/GCE exhibits a couple of irreversible redox peaks with an oxidation peak potential suitable for the nitrite oxidation in 0.1 M H2SO4. Quite differently, in the PBS aqueous buffer solution, the Mn-CP electrode has a couple of irreversible redox peaks. The reduction peak potential is appropriate for the H2O2 reduction. So, the Mn-CP/GCE can be used not only in the electrocatalytic oxidation of NO2– but also in the electrocatalytic reduction of H2O2. The amperometric response reveals that the Mn-CP/GCE exhibits high-selective and extremely sensitive oxidation sensing of NO2– and reduction sensing of H2O2. The exponential detection range is 0.01–20 mM for NO2– and 0.01–10.5 mM for H2O2. The linear detection range for both H2O2 and NO2– is 0.01–0.10 mM. The detection limit is 1.865 μM for NO2– and 8.57 μM for H2O2. The Mn-CP/GCE exhibits high electrochemical stability and fine reproducibility. Moreover, the strategy can be translated to a portable screen-printed electrode (SPE). The Mn-CP/SPE shows more sensitive sensing to NO2– and H2O2 than Mn-CP/GCE. Moreover, it can detect NO2– and H2O2 efficiently in the real-world samples. So, Mn-CP may be a potential dual nonenzymatic electrochemical sensory material for NO2–via oxidation sensing and H2O2via reduction sensing.

Preparation, characterization, and electrochemical sensing performance of a novel pristine Cd-MOF and its composite with carbon nanotubes.

A novel Cd(II)-organic framework (Cd-MOF) {[Cd(isba)(bbtz)2(H2O)]·H2O}n (1) and its composite with CNTs (Cd-MOF@CNTs), [H2isba = 2-iodo-4-sulfobenzoicacid; bbtz = 1, 4-bis(1,2,4-triazolyl-1-methyl)benzene], were synthesized successfully under ambient conditions. The Cd-MOF is a 2D (4, 4) topological framework, further extending into a two-fold interpenetrated 3D supramolecular network via hydrogen bonding. The activation energy for proton transfer in the composite Cd-MOF@CNT/Nafion membrane is lower than that in pristine Cd-MOF/Nafion, leading to its more temperature-insensitive proton conductivity. Hence, the proton conduction of the composite Cd-MOF@CNT/Nafion membrane was greatly improved. Cyclic voltammograms indicate that the Cd-MOF/GCE only has an oxidation peak with the peak potential suitable for the oxidation of glucose in 0.1 M NaOH. The i-t current response demonstrates that the Cd-MOF/GCE exhibits sensitive and selective oxidative sensing of glucose in the linear range of 0-5 mM with a limit of detection (LOD) of 9.64 μM. Different from the pristine Cd-MOF, Cd-MOF@CNTs shows a pair of irreversible redox peaks with an anodic peak potential appropriate for the glucose oxidation and a cathodic peak potential suitable for the hydrogen peroxide reduction in 0.1 M NaOH. So, the Cd-MOF@CNTs/GCE can be used not only for the electrocatalytic oxidation of glucose, but also for the electrocatalytic reduction of H2O2. The current-time response curve demonstrates that the Cd-MOF@CNTs/GCE exhibits more sensitive and selective oxidative sensing for glucose exponentially in the 0-18.5 mM range with a lower LOD down to 2.63 μM. The reductive sensing of H2O2 increases linearly in the range of 0-14.0 mM (LOD = 33.70 μM). Moreover, the Cd-MOF@CNTs/GCE can detect glucose and H2O2 efficiently in real-world samples. Cd-MOF@CNTs may act as a dual non-enzymatic electrochemical sensory material for glucose and H2O2.

(General Student Poster Award Winner - 1st Place) Nitrogen-Doped and Phosphorus-Doped Carbon Fiber Ultramicroelectrodes As Electrochemical Sensors for Detection of Hydrogen Peroxide

Ultramicroelectrodes (UMEs) are generally defined as electrodes with sizes ≤25 µm. UMEs can be prepared by several methods including by sealing a conductive filament like thin metal wire or a single carbon fiber in a glass capillary. The small size of UMEs makes them useful as probes for measuring electroactive species in confined spaces (for example, inside living cells, etc.), and also enables very effective mass transport, resulting in rapid achievement of steady-state response and facilitating measurement of fast electrochemical reactions. Application of UMEs often requires modification of the electrode surface to improve the selectivity and the sensitivity towards the target analyte. Surface modification methods are time-consuming and may require expensive equipment. Previous research in our group demonstrated that a simple soft nitriding method could be employed to introduce surface nitrogen on carbon fiber (CF). The technique improved electrochemical response of CF-UMEs towards hydrogen peroxide (a reactive oxygen species that has been related to various malignancies and disorders) and, in separate experiments, also enabled deposition of electroactive metal nanoparticles on the UME surface. Since the presence of phosphorus heteroatoms on carbon electrodes has been shown to impart similar benefits, here we investigate a simple phosphorus doping strategy to make P-doped CF-UMEs. We compare their properties towards the electrocatalytic reduction of H2O2 to both N-doped CF-UMEs and unmodified CF-UMEs.

(Invited, Digital Presentation) In-Situ Prussian Blue Formation on Intrinsic Iron-Containing MWCNT As a Template and Its Scanning Electrochemical Microscopic Interrogation and Hydrogen Peroxide Electrocatalysis

Prussian blue (PB; iron (III) hexacyanoferrate), is a mixed-valent polynuclear complex widely used in electrochromic display, biosensors, ion-selective electrodes, electrocatalysis and energy storage systems like batteries and fuel cells [1,2]. For the PB preparation, an electrochemical deposition using an equimolar concentration of Fe2+ and Fe(CN)6 3- in 0.1 M KCl-electrolyte condition was reported. In another case, a template approach, wherein either Fe2+ (or ironic species) or Fe[(CN)6]3- immobilized on the electrode surface followed by interaction with counter ion were reported [3]. For instance, a deliberately added ironic species (>20 wt.%) into a multiwalled carbon nanotube (MWCNT) modified electrode has been utilized as a template for the PB functionalized MWCNT preparation by potential cycling of the precursor electrode with Fe[(CN)6]3- [3]. Meanwhile, an intrinsic iron species that originated from its catalytic source has been referred an influencing parameter in altering the electronic conductivity of the MWCNT (MWCNT-Fe*, Fe*-Instrinsic iron) [4]. Our group has utilized the pristine MWCNT as a template for in-situ preparation MWCNT@Fe*(bpy)3 2+ and as an electro-Fenton catalyst for electroanalytical applications [5]. However, the in-situ derivation of iron impurity (2-4 wt.%) into the Prussian blue complex has not been explored yet. The inaccessibility of the iron and its low concentrations are the likely reason for the limitation. This report demonstrates an in-situ electrochemical PB formation using MWCNT-Fe* modified glassy carbon electrode as a template and Fe(CN)6 3- as a counter ionic species. This modified electrode (GCE/MWCNT-Fe@PB) showed a characteristic redox peak for the high-spin ironic state of PB at about 0.2 V vs Ag/AgCl in addition with a post-peak at 0.3 V vs Ag/AgCl [Figure 1A]. The nickel impurity in the pristine MWCNT is suspected to be involved in the complexation with Fe(CN)6 3- ion along with the ironic species.In-situ formation of PB on MWCNT-Fe* was probed using the scanning electrochemical microscope technique (SECM). In a typical experiment, MWCNT-Fe* modified GCE was taken as a base-electrode along with 5 mM Fe(CN)6 3- in pH 2 KCl-HCl electrolyte and the potentials were set as 0.1 V and 0.5 V vs Ag/AgCl accordingly to reduce FeIII(CN)6 3- + e-® FeII(CN)6 4- and parallely reoxidize it as FeII(CN)6 4- ® FeIII(CN)6 3- + e- on the Pt-tip surface (Figure 1B). The FeII(CN)6 4- ion formed as an intermediate species interacts chemically with Fe2+ ion that might be stripped out from the MWCNT-Fe* on the interface for the in-situ PB formation [Figure 1C]. An island-like morphology with average particle size, few micrometers of PB crystallites on the MWCNT-Fe* surface was noticed. Typical SECM surface imaging of a controlled carbon, carbon nanofiber (CNF), which doesn’t have any metal impurity, was displayed in Figure 1D. A feature-less surface morphology was noticed under the identical imaging condition. Physico-electrochemical characterization of GCE/MWCNT-PB modified electrode using Raman, FT-IR, UV visible spectroscopy and Field emission scanning electron microscopy (FESEM) supported the formation of a hybrid complex on MWCNT-Fe* electrode surface. It has been confirmed that intrinsic iron content was responsible for the PB-formation. As an independent electroanalytical study, the selective electrocatalytic reduction of H2O2 was carried out using a newly developed MWCNT-PB system [Figure 1B]. As an electroanalytical application, amperometric i-t sensing of H2O2 was carried out, which showed a calibration plot wth linearity upto ~5mM of H2O2 at an operating potential, 0.1 V vs Ag/AgCl in pH 2 solution. There is no interference by common biochemical such as ascorbic acid (AA), uric acid (UA), dopamine (DA), cysteine (CySH), nitrite, nitrate and glucose etc.In conclusion, we have prepared a Prussian blue functionalized MWCNT modified glassy carbon electrode using an intrinsic iron-containing MWCNT as a template in an acidic solution. The in-situ formation of PB on the MWCNT-Fe* has been probed and imaged using the scanning electrochemical microscope technique. The selective electrocatalytic and electroanalytical applications of the GCE/MWCNT-Fe@PB towards H2O2 have been demonstrated. This study will provide unique info about the intrinsic iron in the MWCNT and its in-situ derivatization process. Acknowledgement The authors acknowledge the Department of Science and Technology – Science and Engineering Research Board and Technology Development Program, DST-SERB-EMR/2016/002818, IDP/MED/04/2017 and CRG/2021/001048 Schemes for the funding. References A.A. Karyakin, Electroanalysis, 13, 813 (2001).J. Chen, L. Wei, A. Mahmood, Z. Pei, Z. Zhou, X. Chen and Y. Chen, Energy Storage Mater., 25, 585 (2020).R. Shanmugam, P. Barathi and A.S. Kumar, Colloids Surf. A: Physicochem. Eng. Aspects, 452, 129 (2014).C.E.Banks, A.Crossley, C.Salter, S.J.Wilkins, R.G.Compton, R. Angew. Chem., Int. Ed. 45, 2533 (2006)P. Mayuri and A.S. Kumar, Langmuir, 31, 5945 (2015). Figure 1

The [CuI4Cl4] cluster of a coordination complex based on polypyridyl ligand for heterogeneous Fenton-like MB degradation without illumination and electrocatalytic reduction of H2O2 and K2Cr2O7

Developing novel materials for elimination of organic pollutants in wastewater has become one of the most imperious demands for human environment. Herein, a [CuI4Cl4]-containing complex [Cu4(DNP)Cl4)] (1) (DNP = 2,6-di(1,8-naphthyridine-2-yl)pyridine) based on π-conjugated polypyridyl ligand has been solvothermally synthesized, exhibiting a three-dimensional structure via C–H⋯Cl hydrogen bonds and π···π interactions between pyridine rings. Complex 1 displays good Fenton-like degradation efficiency toward methylene blue (MB) with the rate of 71.9% in 120 min under dark condition, in which the interactions between CuI centers and DNP are of extraordinary importance for enhanced degradation efficiency. The degradation products are identified by liquid chromatography-mass spectrometry (LC-MS) and two MB degradation pathways have been proposed. In addition, complex 1 demonstrates good electrocatalytic activity for reduction of H2O2 and K2Cr2O7 via redox of CuII/CuI. This work presents an effective strategy for the rational design of coordination complexes for Fenton-like catalysis and electrocatalytic reduction.

Supramolecular Host-Guest Interaction-Driven Electrochemical Recognition for Pyrophosphate and Alkaline Phosphatase Analysis.

We report an electrochemical biosensor based on the supramolecular host-guest recognition between cucurbit[7]uril (CB[7]) and L-phenylalanine-Cu(II) complex for pyrophosphate (PPi) and alkaline phosphatase (ALP) analysis. First, L-Phe-Cu(II) complex is simply synthesized by the complexation of Cu(II) (metal node) with L-Phe (bioorganic ligand), which can be immobilized onto CB[7] modified electrode via host-guest interaction of CB[7] and L-Phe. In this process, the signal of the complex-triggered electro-catalytic reduction of H2 O2 can be captured. Next, due to the strong chelation between PPi and Cu(II), a biosensing system of the model "PPi and Cu(II) premixing, then adding L-Phe" was designed and the platform was applied to PPi analysis by hampering the formation of L-Phe-Cu(II) complex. Along with ALP introduction, PPi can be hydrolyzed to orthophosphate (Pi), where abundant Cu(II) ions are released to form L-Phe-Cu(II) complex, which gives rise to the catalytic reaction of complex to H2 O2 reduction. The quantitative analysis of H2 O2 , PPi and ALP activity was achieved successfully and the detection of limits are 0.067 μM, 0.42 μM and 0.09 mU/mL (S/N=3), respectively. With its high sensitivity and selectivity, cost-effectiveness, and simplicity, our analytical system has great potential to for use in diagnosis and treatment of ALP-related diseases.

Non-enzymatic electrocatalytic detection of hydrogen peroxide using Tungsten disulphide nanosheets modified electrodes

Herein, we report the facile synthesis of WS2 nanosheets and the development of WS2 nanosheets modified glassy carbon electrodes for the non-enzymatic voltammetric detection and quantification of H2O2. Cyclic voltammetric studies were conducted to evaluate the sensor performances. The good electrical conductivity of WS2 nanosheets and the availability of surface-active reaction sites promoted the electrocatalytic reduction of H2O2 through a 2-electron transfer process. Moreover, the reduction of H2O2 on WS2/GCE was found to be an irreversible adsorption-controlled process. The proposed sensor advertised linearity in the detection of H2O2 from 10 to 90 µM, with a limit of detection (LOD) and sensitivity of 0.88 µM and 0.303 µA µM−1 cm−2 respectively. The fabricated sensor also displayed a remarkable selectivity. The present study also demonstrated the practical utility of the proposed WS2/GCE sensor for H2O2 probing.

Unveiling the effect of gas treatment on the electronic structure of carbon nanotube-supported Pd catalysts for electroreduction of H2O2 and Heck reaction

This study explored the impact of gas treatments on the structures of multi-walled carbon nanotubes supported Pd (CNT-Pd) catalysts used for electrocatalytic H2O2 reduction and the Heck cross-coupling reaction. The CNT-Pd catalyst was prepared by anchoring Pd nanoparticles on thiolated CNTs. XPS was conducted to examine the surface composition and electronic structure changes of the CNT-Pd catalyst before and after gas treatment. The XPS results revealed that as-prepared CNT-Pd contains at least two different oxidation states on the surface, whereon their proportions depend on the gas used for treatment. Treatment with H2 leads to Pd(0) enrichment near the surface, while O2 treatment causes Pd(Ⅱ) enrichment of CNT-Pd. All catalysts containing both Pd(0) and Pd(Ⅱ) were active toward H2O2 reduction, and the Heck cross-coupling reaction of n-butyl acrylate and 4-iodotoluene; increased proportion of metallic Pd(0) boosted the catalytic reaction. However, the catalyst stability increased as the amount of Pd(II) increased.

Bio-Electrocatalytic Reduction of Hydrogen Peroxide by Peroxidase from Guinea Grass (Panicum Maximum) Immobilized on Graphene and Graphene Oxide Screen-Printed Electrodes

Objective: In this article a comparison was made between graphene (SPGE) and graphene oxide screen-printed electrodes (SPGOE) to study the bio-electrocatalytic reduction of hydrogen peroxide (H2O2) by guinea grass peroxidase (GGP). Methods and materials: GGP was immobilized onto SPGE and SPGOE by a drop-casting procedure. Electrochemical techniques were carried out to monitor the electrochemical behavior of GGP and the efficiency of electrocatalytic reduction of H2O2. Results and discussion: GGP adsorbed on both electrodes exhibited a couple of well-defined redox peaks at 120 mV/10.5 mV and 184 mV/59 mV for anodic and cathodic peaks, respectively. Linearity between scan rates root and oxidation and reduction peak currents for both electrodes suggest a surface-controlled process. The GGP-modified electrodes exhibited a good electrocatalytic activity to H2O2 reduction at a redox potential of -0.6 V and -0.5 V for SPEG and SPEGO, respectively. Conclusions: SPGE and SPGOE electrodes modified with GGP showed excellent analytical performance towards different concentrations of hydrogen peroxide. This is a preliminary step to developing a bio-analytical portable system based on GGP for the detection of H2O2 in real environmental samples.

Three-dimensional graphene-like homogeneous carbon architecture loaded with gold-platinum for the electrochemical detection of circulating tumor DNA

The analysis of circulating tumor DNA (ctDNA) turns out to be increasingly significant considering its potential value in the clinical diagnosis of cancer. Herein, a ctDNA electrochemical biosensor was developed with a low detection limit and high selectivity by using three-dimensional graphene-like homogeneous carbon architecture (3D-GHC600) loaded with gold-platinum (AuPt). The 3D-GHC600 was derived from the annealing process of copper-based metal-organic framework (denoted as Cu-BTC) at the optimal temperature (600 °C), which includes the merits of large area, rich mesopores, homogeneous size and morphology, and 3D structure. AuPt was formed on the 3D-GHC600 surface via an in-situ reduction reaction. Characterizations demonstrated that the resultant composite catalyst (AuPt/3D-GHC600) was prepared successfully and exhibited remarkable electrochemical properties. Further, the catalyst was used as a label of signal probes (SPs) to form SPs-label. The hybridization reactions were completed by layer-by-layer recognition of capture probes (CPs), target DNA (tDNA), and SPs-label on the electrode, thus forming a sandwich-like structure. The current signals of the SPs-label toward the electrocatalytic reduction of H2O2 were recorded in all tests for tDNA analysis. Accordingly, this recommended biosensor of tDNA showed good performance including a wide linear range of 10−8 M − 10−17 M with a detection limit of 2.25 × 10−18 M (S/N = 3), excellent selectivity for the recognition of different interferences, satisfying reproducibility, good stability, and outstanding recovery. These results demonstrated the promising application of the biosensor in the detection of ctDNA.

Hybrid PANI@dialdehyde carboxymethyl cellulose/ZnO nanocomposite modified glassy carbon electrode as a highly sensitive electrochemical sensor

In this research, a highly sensitive voltammetric sensor for hydrogen peroxide (H2O2) detection has been examined using a new hybrid material based polyaniline, dialdyhayed carboxmethyl cellouse and in the presence of ZnO nanoparticles abbreviated as (PANI/D-CMC/ZnO). Various approaches such as cyclic voltammetry (CV), and differential pulse voltammetry were used to investigate the electrocatalytic reduction of H2O2 (DPV). After preparation, (SEM) scanning electron microscopy, (XRD) X-ray diffraction, and (FTIR) Fourier transform infrared techniques were used to characterize and analyze the obtained PANI/D-CMC/ZnO material. Furthermore, as a suitable for determining hydrogen peroxide (H2O2), a high conductivity platform based on PANI/D-CMC/ZnO electrode modified nanocomposite was created. The modified PANI/D-CMC/ZnO, electrode indicated a good linear range and a low detection limit (LOD) of 0.45 M for hydrogen peroxide determination under optimal conditions (pH 5.7). The peak current of differential pulse voltammetry (DPV) method of hydrogen peroxide increased linearly with its concentration. The concentration has been linear from in the ranges of 0.50 to 5 μM and 10 to 50 μM. The sensor was successfully used to test for hydrogen peroxide in real samples like milk.

Sandwich-type electrochemical aptasensor based on hollow mesoporous carbon spheres loaded with porous dendritic Pd@Pt nanoparticles as signal amplifier for ultrasensitive detection of cardiac troponin I

Signal amplification is crucial to improve the sensitivity for the electrochemical detection of cardiac troponin I (cTnI), one of the ideal biomarkers for early acute myocardial infarction (AMI) diagnosis. Herein, we developed a novel signal amplification strategy to construct a sandwich-type electrochemical aptasensor for the detection of cTnI. Core-shell Pd@Pt dendritic bimetallic nanoparticles loaded on melamine modified hollow mesoporous carbon spheres (Pd@Pt DNs/NH2-HMCS) was prepared as labels to conjugate with thiol-modification DNA aptamers probe for signal amplification. While introducing numerous amino groups, the melamine functionalized hollow mesoporous carbon spheres (NH2-HMCS) retained the edge-plane-like defective sites for the adhesion and electrocatalytic reduction of H2O2. With the unique characteristics of NH2-HMCS, it not only enhanced the dispersity and loading capacity of core-shell Pd@Pt dendritic bimetallic nanoparticles (Pd@Pt DNs), but also improved the stability of bonding by the affinity interaction between Pd@Pt DNs and amino groups of melamine. Meanwhile, the synergistic catalysis effect between Pd@Pt DNs and NH2-HMCS significantly enhanced the electrocatalytic reduction of H2O2 and further amplified the signal. Under optimal conditions, this recommended aptasensor for cTnI detection displayed a wide dynamic range from 0.1 pg/mL to 100.0 ng/mL and a low detection limit of 15.4 fg/mL (S/N = 3). The sensor also successfully realized the analysis of cTnI-spiked human serum samples, meaning potential applications in AMI diagnosis.

Unveiling microbiologically influenced corrosion engineering to transfigure damages into benefits: A textile sensor for H2O2 detection in clinical cancer tissues

With the ongoing increasing research interests in economical electrocatalysts, transforming damages into benefits to prepare useful electrode materials is an ideal strategy to achieve the goals. Corrosion engineering converts harmful corrosion processes into high performance catalyst nanostructures. In this work, we develop an inexpensive, scaled-up corrosion engineering strategy for value-added transformation of low-cost iron substrates into highly efficient Cu-Fe(OH)2-FeS deposited on polyester cloth fabric (PCF) flexible electrode by a process of electroless plating combined with microbes assisted corrosion product. The anaerobic sulfate reducing bacteria (SRB) converting sulfate to sulfide play vital role to carry out the construction of Cu-Fe(OH)2-FeS/PCF electrode which reveals high electrochemical sensing performance for H2O2 with broad linear range and low detection limit of 0.2 nM (S/N = 3). The enhanced activity arises from densely deposited nanosheets of transition metals oxides/hydroxides, plethora of surface active sites and synergistic effect between Cu-Fe(OH)2 and FeS species. More importantly, the S2− ions serving as co-catalyst have been found to continuously fuel electrons during the reduction of Fe(III) and Cu(II) which accelerate the redox cycles of Fe(III)/Fe(II) and Cu(II)/Cu(I) further enhancing electrocatalytic H2O2 reduction. With high sensitivity achieved, the Cu-Fe(OH)2-FeS/PCF electrode has also been practically applied in real-time in vitro tracking of H2O2 excreted from different normal and human brain cancer cell lines as well as in situ sensitive detection of H2O2 released from human brain tumor tissues. This work presents a good way to bridge up the gap between annoying traditional corrosion engineering and emerging electrochemical technologies.

Biocompatible MXene (Ti3C2Tx) Immobilized with Flavin Adenine Dinucleotide as an Electrochemical Transducer for Hydrogen Peroxide Detection in Ovarian Cancer Cell Lines.

Flavin adenine dinucleotide (FAD) is a coenzyme and acts as a redox cofactor in metabolic process. Owing to such problems as poor electron transfer properties, unfavorable adsorption, and lack of stability on rigid electrodes, the bio-electrochemical applications of FAD have been limited. Herein, a novel fabrication method was developed for the immobilization process using 2D MXene (Ti3C2Tx), which enhanced the redox property of FAD and improved the electro-catalytic reduction of hydrogen peroxide (H2O2) in neutral medium. The FAD-immobilized Ti3C2Tx electrode (FAD/Ti3C2Tx) was studied by UV-Visible and Raman spectroscopies, which confirmed the successful adsorption of FAD on the Ti3C2Tx surface. The surface morphology and the elemental composition of Ti3C2Tx were investigated by high resolution transmission electron microscopy and the energy dispersive X-ray analysis. The redox property of the FAD/Ti3C2Tx modified glassy carbon electrode (FAD/Ti3C2Tx/GCE) was highly dependent on pH and exhibited a stable redox peak at −0.455 V in neutral medium. Higher amounts of FAD molecules were loaded onto the 2D MXene (Ti3C2Tx)-modified electrode, which was two times higher than the values in the reported work, and the surface coverage (ᴦFAD) was 0.8 × 10−10 mol/cm2. The FAD/Ti3C2Tx modified sensor showed the electrocatalytic reduction of H2O2 at −0.47 V, which was 130 mV lower than the bare electrode. The FAD/Ti3C2Tx/GCE sensor showed a linear detection of H2O2 from 5 nM to 2 µM. The optimization of FAD deposition, amount of Ti3C2Tx loading, effect of pH and the interference study with common biochemicals such as glucose, lactose, dopamine (DA), potassium chloride (KCl), ascorbic acid (AA), amino acids, uric acid (UA), oxalic acid (OA), sodium chloride (NaCl) and acetaminophen (PA) have been carried out. The FAD/Ti3C2Tx/GCE showed high selectivity and reproducibility. Finally, the FAD/Ti3C2Tx modified electrode was successfully applied to detect H2O2 in ovarian cancer cell lines.

Enzyme‐free Electrochemical Detection of Hydrogen Peroxide Based on the Three‐Dimensional Flower‐like Cu‐based Metal Organic Frameworks and MXene Nanosheets†

Main observation and conclusionCu‐based metal organic frameworks (MOFs) are regarded as promising sensing materials, which have abundant metal sites, large surface area and simple synthesis processes. In this work, a novel three‐dimensional flower‐like Cu‐MOF was synthesized, which was combined with ultra‐thin MXene nanosheets to construct a novel electrochemical sensor for H2O2. During the electrocatalytic reduction of H2O2, the catalytic activity of Cu‐MOF/MXene/GCE results in the ultra‐sensitive detection of H2O2 owing to the structure properties of MOFs, the nature of Cu‐contained nanomaterials as well as the high electrical conductivity of MXene. The Cu‐MOF/MXene/GCE showed a wide linear range from 1 μmol/L to 6.12 mmol/L using chronoamperometry at the detection potential of –0.35 V, and the detection limit is estimated to be 0.35 μmol/L. The sensor also shows good anti‐interference due to the lower detection potential, specific catalysis of Cu‐MOF to H2O2, which promises the sensor good selectivity in complexed samples. Meanwhile, the electrochemical sensor is capable to detect H2O2 in milk and serum samples with satisfactory recoveries. The ultra‐sensitivity, rapid detection, and easy operation of the proposed sensor present significant prospect for real‐time analysis and monitoring of H2O2 in foods and biological samples.

Voltammetric determination of hydrogen peroxide using MoS2 modified glassy carbon electrodes

We report the facile synthesis of MoS2 microspheres and the construction of MoS2/glassy carbon electrodes (GCE) for the precise detection of hydrogen peroxide (H2O2). The electrochemical performance of MoS2 modified GCE was investigated by using cyclic voltammetry (CV). High surface area and good electrical conductivity of MoS2 microspheres facilitated the superior electrocatalytic reduction of H2O2. MoS2/GCE sensor displayed high sensitivity, linearity in detection from 10 to 100 µM with the lower detection and quantification limits of 1.13 µM and 3.82 µM.