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Surface charge engineering of nanosized CuS via acidic amino acid modification is proved to be an efficient strategy to realize high peroxidase-mimicking catalytic activity at neutral pH. As a proof-of-concept application, one-pot high-performance colorimetric sensing of glucose by coupling the engineered nanozyme with glucose oxidase is realized.

Enzyme-free electrochemical detection of glucose in alkaline media with favorable properties has been acquired by fabricating a robust and large-surface sensing platform, which is composed of anneal-shrinked Cu 2 O dendrites grown on porous Cu foam. On the one hand, the good compatibility of electrodeposited Cu 2 O architectures and Cu foam substrate, together with a post-deposition anneal at 200°C, offers a mechanically stable interface for glucose determination. On the other hand, the macropores of Cu foam that is decorated with unique Cu 2 O dendrites provide large active surface for electrocatalytic reaction and mass transport. As a result, selective sensing of glucose in the linear concentration range of 0.001-1.4mM was achieved on the fabricated sensor, with a sensitivity of as high as 5.04mAcm -2 mM -1 and a detection limit of 0.13μM. Desired long-term performance stability was obtained, partially due to the strong adhesion of Cu 2 O microstructures to the Cu foam support after annealing. Practical monitoring of glucose in serum samples was also demonstrated on the proposed sensor., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Nanosized materials acting as substitutes of natural enzymes are currently attracting significant research due to their stable enzyme-like characteristics, but some flaws of these nanozymes, including their limited catalytic rate and efficiency, need to be remedied to enable their wider applications. In this work, we verify for the first time the catalytic behavior of uncapped nanobranch-based CuS clews as a peroxidase mimic. XRD, XPS, SEM, and TEM proofs demonstrate that high-purity CuS clews composed of intertwined wires with abundant nanodendrites outside are successfully produced via a facile one-pot hydrothermal synthesis approach, with thiourea as both the sulfion source and the structure-directing agent. The synthesized CuS can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H 2 O 2 to trigger a visible color reaction with rapid response (reaching a maximum change within 5 min). The proposed CuS nanozyme exhibits preferable catalytic kinetics over natural horseradish peroxidase (HRP). This outstanding activity primarily results from the large surface area and rich sites exposed by the uncapped unique structure. Under optimized conditions, the fabricated sensing system provides linear absorbance (652 nm) changes in the H 2 O 2 concentration range of 0.2˜130 μM, with a detection limit of as low as 63 nM. When coupled with glucose oxidase (GOD), the system is demonstrated to be capable of monitoring glucose in blood samples with excellent performance., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The investigation of highly efficient catalysts for the electrochemical oxidation of glucose is the most critical challenge to commercialize nonenzymatic glucose sensors, which display a few attractive superiorities including the sufficient stability of their properties and the desired reproducibility of results over enzyme electrodes. Herein we propose a new and very promising catalyst: Pt cubes well-dispersed on the porous Cu foam, for the the electrochemical oxidation reaction of glucose in neutral media. The catalyst is fabricated in situ on a homemade screen-printed carbon electrode (SPCE) substrate through initially synthesizing the three-dimensional (3D) porous Cu foam using a hydrogen evolution assisted electrodeposition strategy, followed by electrochemically reducing the platinic precursor simply and conveniently. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) proofs demonstrate that Pt cubes, with an average size (the distance of opposite faces) of 185.1 nm, highly dispersed on the macro/nanopore integrated Cu foam support can be reproducibly obtained. The results of electrochemical tests indicate that the cubic Pt-based catalyst exhibits significant enhancement on the catalytic activity towards the electrooxidation of glucose in the presence of chloride ions, providing a specific activity 6.7 times and a mass activity 5.3 times those of commercial Pt/C catalysts at -0.4 V (vs. Ag/AgCl). In addition, the proposed catalyst shows excellent stability of performance, with only a 2.8% loss of electrocatalytic activity after 100 repetitive measurements., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The sluggish kinetic-controlled glucose oxidation reaction on Pt electrodes is well recognized as the most critical issue that blocks the development and commercialization of enzyme-free glucose sensors, and increasing attention is being focused on improving the analytical performances of these nonenzymatic sensors through exploring new Pt-based catalysts. In the present research, we synthesized novel Pt-Pd nanoflakes (Pt-Pd NFs) with three-dimensional architectures on a homemade screen-printed gold film electrode (SPGFE) substrate using a facile electrochemical deposition without any template, and further investigated the properties of the as-fabricated Pt-Pd NFs/SPGFE for enzymeless glucose detection. The results reveal that the proposed Pt-Pd nanostructure can provide preeminent electrocatalytic activity and excellent selectivity for enzyme-free glucose sensing under simulative physiological conditions, mainly attributing to its attractive structure, large active surface and appropriate applied potential. The resulting Pt-Pd NFs/SPGFE offers linear current responses for glucose with the concentration upper limit to 16 mM. The obtained sensitivity is calculated to be as high as 48.0 μA cm(-2) mM(-1) in the presence of 0.15 M chlorides ions, and practical applications for blood sample analysis are also demonstrated. The proposed Pt-Pd structure is considered as a great potential building block for the fabrication of nonenzymatic electrochemical glucose sensors., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Novel snowflake-like Pt-Pd bimetallic nanoclusters (Pt-PdBNC) were synthesized on a screen-printed gold nanofilm electrode (SPGFE) substrate by electrochemically reducing precursors with a new constant potential/multi-potential step deposition strategy. The electrocatalytic behavior of the modified electrode (SPGFE/Pt-PdBNC) towards H(2)O(2) was investigated. The results indicate that the as-prepared Pt-PdBNC significantly enhances the electrochemical reduction of H(2)O(2) in neutral media, exhibiting preferable electrocatalytic performance compared to Pt and Pd monometallic nanoclusters. Under optimum conditions, SPGFE/Pt-PdBNC offers linear responses for H(2)O(2) in the concentration range from 0.005 to 6 mM with an ultrahigh sensitivity of 804 mA M(-1) cm(-2) and excellent selectivity. Furthermore, glucose oxidase was immobilized on the Pt-PdBNC structure, and the fabricated biosensor presents favorable properties for glucose sensing., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Abstract: In this work, a metal‐organic frameworks‐based porous carbon was explored for glucose oxidase immobilization and glucose sensing. ZIF‐67 was chosen as the precursors for the calcination treatment. The formed Co nanoparticles induced the graphitization of the carbon during the carbonization, resulting in a good conductivity. The followed HCl treatment partly removed the formed Co nanoparticles to give a larger specific surface area of the porous carbon due to the generated space voids from the dissolved Co nanoparticles. The resulting MOFs‐derived porous carbon show an improved loading performance toward glucose oxidase, and fast electron transfer was also demonstrated. This work proves the MOFs‐derived porous carbon as a novel and outstanding platform for the enzymatic electrocatalysis for the sensors and energy conversion devices. [ABSTRACT FROM AUTHOR]

Improving the electrocatalytic activity of Pt-based catalysts is of great importance for the development of heterogeneous catalysis, fuel cells, and analytical sensors. Herein, we achieve significant enhancement of the catalytic activity of Pt-Pd bimetallic materials towards glucose electrooxidation by introducing porous architectures with three-dimensional dendritic microstructures, which were fabricated in situ on desired substrates through electrochemically reducing precursors along with periodic bubbling caused by the intermittent liberation of hydrogen. The synthesized Pt-Pd materials were characterized by SEM, nitrogen adsorption/desorption, energy dispersive spectroscopy, XRD, inductively coupled plasma optical emission spectrometry, and electrochemical techniques. Encouragingly, an extra-large active surface area of up to 80.8 m2 g−1 was obtained for the porous Pt-Pd nanostructures, almost 3.8 times that of the Pt-Pd alloys prepared by standard electrodeposition techniques. As a result, the synthesized Pt-Pd with porous frameworks exhibited remarkably improved electrocatalytic properties for glucose oxidation in neutral media, with 1.5 times the mass activity compared to the conventional Pt-Pd structure. In addition, the porous Pt-Pd catalysts could be reused at least 100 times in the presence of chloride ions, with negligible loss of activity. [ABSTRACT FROM AUTHOR]

In this work, we applied metal-organic frameworks (MOFs) as a porous matrix to encapsulate Cu nanoparticles (NPs) for nonenzymatic glucose sensing in alkaline media. SEM and TEM confirmed that the size of the encapsulated Cu NPs ranges from 2.5 to 5 nm. The hybrid of Cu NPs encapsulated in ZIF-8 (Cu-in-ZIF-8) was further modified onto screen-printed electrodes for nonenzymatic sensing of glucose in alkaline medium. The porous structure of ZIF-8 are beneficial for the unimpeded diffusion of glucose and reaction product. And as a matrix for encapsulating Cu NPs, ZIF-8 also protect the Cu NPs from dissolution and agglomeration during the electrocatalytic process. For comparison, the electrochemical performance of Cu NPs loaded on ZIF-8 (Cu-on-ZIF-8) was also investigated and it is found that Cu-in-ZIF-8 exhibited higher activity and better stability for cyclic test toward the oxidation of glucose in alkaline media. Additionally, Cu-in-ZIF-8 based glucose sensor also shows a favorable sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

With respect to a nonenzymatic electrochemical sensor for detection of small biomolecules like glucose, it is well recognized that an interface with highly electrocatalytic properties is desired. Our previous studies have demonstrated that porous Cu foams from hydrogen evolution assisted electrodeposition could provide beneficial structures for large active surface and mass transfer in glucose sensing ( Biosens. Bioelectron. , 2014, 51: 22-28), and decoration of micro-scale Pt cubes on this multiaperture substrate through manipulative deposition offered exciting activity and stability for electro-catalyzing glucose in neutral media ( Chem. Eur. J. , 2013, 19: 9534-9541). On the basis of these results here we further cover the porous Cu frameworks with a Pt monolayer through the galvanic replacement reaction, and fabricate a new electrochemical interface for high-performance determination of glucose. The sensing surface was facilely assembled by firstly electrodepositing porous Cu architectures with hydrogen evolution and then galvanically replacing the surface layer with Pt, and was well characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and energy dispersive spectroscopy. It was found that the unilaminar Pt-replaced Cu frameworks, with the profitable reaction surface derived from porous skeletons and the underlying activity of Pt-support composites, could supply the highly electrocatalytic oxidation of glucose in phosphate buffer solution (pH 7.4). As a result, the prepared enzymeless sensor provided linear amperometric responses for glucose in the concentration scope of 1∼11 mM, with a high sensitivity of 9.62 μA cm −2 mM −1 . [ABSTRACT FROM AUTHOR]

Abstract: It is widely thought in electro-biochemical analysis that the sensing interfaces play a key role in the enzymeless detection of biomolecules like glucose, ascorbic acid, dopamine and uric acid. On the way to maximize the anti-poisoning sensitivity of nonenzymatic electrochemical glucose sensors as well as achieve favorable selectivity, we propose here a porous interface fabricated by a facile but effective approach for glucose monitoring in alkaline media containing dissolved oxygen. The sensing interface based on porous Cu foams is directly formed on a homemade disposable screen-printed carbon electrode (SPCE) substrate by electrodeposition assisted with hydrogen evolution simultaneously, and its porosity can be easily tailored through adjusting deposition conditions for the optimal electrocatalytic oxidation of glucose molecules. SEM and BET studies show that the generated Cu foam possesses robust hierarchical porous architectures with greatly enhanced surface area and pore volume, beneficial for the unimpeded mobility of glucose and reaction products. Cyclic voltammetric tests indicate that a diffusion-controlled glucose electro-oxidation reaction occurs at the Cu foam electrode at around +0.35V vs. Ag/AgCl in 0.1M NaOH. Chronoamperometric results obtained under optimized conditions reveal that the proposed sensor exhibits desired poison resistance ability in the presence of chloride ions and significant selectivity to glucose, providing fascinating sensitivities of 2.57 and 1.81mAcm−2 mM−1 for glucose in the linear concentration ranges of 2–80μM and 0.1–5mM, respectively. The limit of detection is calculated to be as low as 0.98μM according to the signal-to-noise ratio of three. In addition, the fabricated sensing interface shows attractive reproducibility (RSD of 5.1% and 7.0% for 15 repeated measurements on a sensor and for measurements on 15 prepared sensors, respectively) and outstanding long-term stability (less than 5% loss in sensitivity over 1 month) for glucose detection. The application of the Cu foam based sensor for monitoring glucose in practical samples is also successfully demonstrated. [Copyright &y& Elsevier]

Abstract: Novel snowflake-like Pt–Pd bimetallic nanoclusters (Pt–PdBNC) were synthesized on a screen-printed gold nanofilm electrode (SPGFE) substrate by electrochemically reducing precursors with a new constant potential/multi-potential step deposition strategy. The electrocatalytic behavior of the modified electrode (SPGFE/Pt–PdBNC) towards H2O2 was investigated. The results indicate that the as-prepared Pt–PdBNC significantly enhances the electrochemical reduction of H2O2 in neutral media, exhibiting preferable electrocatalytic performance compared to Pt and Pd monometallic nanoclusters. Under optimum conditions, SPGFE/Pt–PdBNC offers linear responses for H2O2 in the concentration range from 0.005 to 6mM with an ultrahigh sensitivity of 804mAM−1 cm−2 and excellent selectivity. Furthermore, glucose oxidase was immobilized on the Pt–PdBNC structure, and the fabricated biosensor presents favorable properties for glucose sensing. [Copyright &y& Elsevier]

Abstract: A one-step enzyme immobilization process with silica sol–gel/polyvinyl alcohol was described to achieve direct electrochemistry of glucose oxidase on screen-printed electrodes. The immobilized glucose oxidase displays a couple of stable and well-defined redox peaks with an electron transfer rate constant of 8.38s−1 and a formal potential of −460mV (versus SCE) in phosphate buffer (0.05M, pH 7.0) at a scan rate of 300mVs−1. The results suggested that conformation and bioactivity of glucose oxidase could be retained efficiently using the proposed immobilization method and the porous structure of screen-printed electrode surface was helpful for electron communication of glucose oxidase and the electrode. Furthermore, the modified electrode was used as a glucose biosensor, exhibiting a linear response to glucose concentration ranging from 0 to 4.13mM and a sensitivity of 3.47μAmM−1 cm−2 at an applied potential of −0.5V. The detection limit of the biosensor is 9.8μM, based on a signal-to-noise ratio of 3. The present work provided a promising strategy for fabricating a novel and disposable mediatorless glucose biosensor, which could be mass-produced through further development. [Copyright &y& Elsevier]