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Highlights • Non-enzymatic electrochemical glucose sensor based on bronze which was installed on a smart toothbrush. • Good selectivity and high sensitivity towards glucose oxidation in the presence of interfering species. • This sensor can be regenerated simply by mechanically polishing for long-term uses. Abstract Bronze is one of copper alloy materials that have been widely used not only in the Bronze Age, but also nowadays because they are hard, easy to cast and resistant against corrosion. For bronze, tin is commonly used as the major non-copper ingredient of bronze because of many highly desirable characteristics including the fact that metallic tin is not toxic. We find that the tin bronze is a suitable electrode material for non-enzymatic electrochemical glucose sensing in saliva. For electrocatalytic oxidation of glucose on the bronze electrode, a negative potential is applied for proton reduction which creates a temporary alkaline condition. The sensor has a linear range from 0 to 320 μM with the regression equation: i = 11 + 0.015 C (i is the current in μA and C is the concentration in μM) with a correlation coefficient of 0.994. The sensitivity is found to be 480 μA mM−1 cm-2, and the detection limit is 6.6 μM with a signal-to-noise ratio of 3. The electrode is found to be highly selective towards glucose oxidation in the presence of interfering species such as ascorbic acid and uric acid. The electrochemical senor is integrated into a smart toothbrush for monitoring of saliva glucose, which is potentially useful for non-invasive screening of diabetes. Compared with other electrochemical glucose sensors, a naked bronze electrode is used as the working electrode to ensure the robustness of the sensor. No additional reagent is involved for the electrochemical determination of saliva glucose and the electrode can be regenerated simply by mechanically polishing for long-term uses. [ABSTRACT FROM AUTHOR]

Electrochemically reduced graphene oxide (ERGO) based voltammetric sensors have drawn considerable attentions due to their simple preparation process and outstanding electrochemical properties. While quite a lot of work suffers from problems in terms of sensitivity and cycling stability. Here, we demonstrate that the reduction extent of ERGO displays a crucial role in enhancing sensitivity and preventing electrode fouling. To illustrate this, partially reduced and relatively complete reduced ERGO films were prepared via the electrochemical method. The reduction extent was controlled by performing cyclic voltammetry with varieties of reduction cycle numbers. Results indicated that partially reduced ERGO film with 5 reduction cycle numbers (ERGO 5 ) showed the highest sensitivity towards electrochemical oxidation of isoniazid (INZ) among all the ERGO films with different reduction extents, and acquired better electrode stability as compared with ERGO 15 . Under the optimal conditions, the peak currents on ERGO 5 modified electrode increased linearly with the concentrations of INZ in the range of 0.09–100 μM. The detection limit of INZ reached 15 nM (S/N = 3). The present work has a guidance meaning in developing ERGO based sensors for detecting other electroactive analytes. [ABSTRACT FROM AUTHOR]

Herein, a sensitive voltammetric method for the determination of diethylstilbestrol (DES), illegally used as a growth promoter in animal husbandry, was developed using electrochemically reduced graphene oxide–multiwalled carbon nanotubes (ERGO–MWCNTs) modified electrode. The incorporated multiwalled carbon nanotubes (MWCNTs) served as electrical conducting wires, which could facilitate the electrochemical reduction of graphene oxide (GO). Compared to either electrochemically reduced graphene oxide (ERGO) or MWCNTs, integrating these nanostructures resulted in a strong synergistic effect between the two materials consequently leading to a superior hybrid material with higher activity for the electro-oxidation of DES. The electron transfer coefficient ( α ), the standard rate constant ( k s ), electrochemically effective surface area ( A ) and the saturating absorption capacity ( Г s ) were calculated. Under the optimized conditions, ERGO–MWCNTs modified electrode exhibited better linearity than either ERGO or MWCNTs over ranges from 0.01 to 40 μM with the detection limit of 3 nM ( S / N = 3). Moreover, the proposed method was successfully applied to determine DES in real sample and satisfactory results were obtained. The results showed that the modified electrode exhibits an excellent catalytic activity, good sensitivity and reproducibility. [ABSTRACT FROM AUTHOR]

Herein, an electrochemical sensor was developed for detecting heavy metal ions by using a carboimidazole grafted reduced graphene oxide (reduced graphene oxide-NH-carboimidazole, abbreviated as RGO-NH-Ci) modified electrode. The morphology of RGO-NH-Ci material was characterized by scanning electron microscopy (SEM). The electrochemical behaviors of the RGO-NH-Ci modified electrode toward heavy metal ions, including Hg 2 + and Pb 2 + , were investigated with differential pulse anodic stripping voltammetry (DPASV). Compared with pure reduced graphene oxide (RGO), RGO-NH-Ci modified electrode showed improved analytical performance in detecting the two metal ions owing to the strong complexing capacity of Ci and the presence of the amino groups. The detection limits were estimated to be 0.2 nM and 3.0 nM for Hg 2 + and Pb 2 + , respectively, under the optimized conditions. The developed method was also employed to detect the Hg 2 + and Pb 2 + in real water samples, and satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

Hierarchical nanocomposites of poly(3,4-ethylenedioxythiophene) nanorods array on graphene oxide nanosheets (PEDOT/GO) were synthesized via a liquid–liquid interfacial polymerization method. The synthesized composites were characterized by using Fourier transform infrared (FTIR) and Raman spectroscopic studies, and their morphology was analyzed by transmission electron microscopy (TEM). Characterization and surface morphology results indicated that PEDOT with a nanorods-like structure successfully anchored on the surface of GO sheets, which could enhance the electro-active sites of the nanocomposites. Then the obtained PEDOT/GO nanocomposites were utilized to modify glassy carbon electrode and designed for the trace level sensing of rutin. Electrochemical results revealed that the PEDOT/GO nanocomposites modified electrode exhibited larger oxidation peak currents of rutin than pure PEDOT and GO owing to the synergistic effect of GO and PEDOT nanorods. Under optimized conditions, the anodic peak current was linear to the concentration of rutin in the range from 0.004 to 60 μM with the detection limit of 0.00125 μM. To further validate its possible application, the proposed method was successfully used for the determination of rutin in pharmaceutical formulations with satisfactory results. [ABSTRACT FROM AUTHOR]

This review (with 155 refs.) summarizes the progress made in the past few years in the field of electrochemical sensors based on graphene-derived materials for the determination of heavy metal ions. Following an introduction of this field and a discussion of the various kinds of modified graphenes including graphene oxide and reduced graphene oxide, the review covers graphene based electrodes modified (or doped) with (a) heteroatoms, (b) metal nanoparticles, (c) metal oxides, (d) small organic molecules, (e) polymers, and (f) ternary nanocomposites. Tables are provided that afford an overview of representative methods and materials for fabricating electrochemical sensors. Furthermore, sensing mechanisms are discussed. A concluding section presents new perspectives, opportunities and current challenges.Schematic illustration of electrochemical sensor for heavy metal ion sensing based on heteroatom-doped graphene, metal-modified graphene, metal-oxide-modified graphene, organically modified graphene, polymer-modified graphene, and ternary graphene based nanocomposites. [ABSTRACT FROM AUTHOR]

The development of electrochemical methods for enantioselective recognition is a focus of research in pharmaceuticals and biotechnology. In this study, a pair of water-soluble chiral 3,4-ethylenedioxythiophene (EDOT) derivatives, (R)-2'-hydroxymethyl-3,4-ethylenedioxythiophene ((R)-EDTM) and (S)-2'-hydroxymethyl-3,4-ethylenedioxythiophene ((S)-EDTM), were synthesized and electrodeposited on the surface of a glassy carbon electrode (GCE) via current-time (I-t) polymerization in an aqueous LiClO4 electrolyte. These chiral PEDOT polymers were used to fabricate chiral sensors and to investigate the enantioselective recognition of d-/l-3,4-dihydroxyphenylalanine, d-/l-tryptophan, and (R)-/(S)-propranolol enantiomers, respectively. The results indicated that the (R)-PEDTM/GCE sensor showed a higher peak current response toward the levo or (S) forms of the tested enantiomers, while the opposite phenomenon occurred for (S)-PEDTM/GCE. The mechanism of the stereospecific interaction between these enantiomers and the chiral polymers was determined. Therefore, a model of the chiral recognition by the chiral conducting polymer electrodes and an electrochemical method was proposed. The chirality of the enantiomers was confirmed by two parameters: the chirality of the electrode and the peak current response. These findings pave the way for the application of chiral PEDOT as electrode modification material in the electrochemical chiral recognition field. [ABSTRACT FROM AUTHOR]

Cu nanoparticle/graphene oxide/single walled carbon nanotube (CuNP/GO/SWCNT) composites were prepared by a facile electrodeposition method and used for constructing nonenzymatic glucose sensor. Scanning electron microscopy (SEM) and Raman spectroscopy were employed to characterize the morphology and structures of the samples. The electrocatalytic performance of CuNP/GO/SWCNT composites towards glucose oxidation was studied by cyclic voltammetry (CV) and current–time measurements. Electrochemical results indicated that CuNP/GO/SWCNT electrode exhibited a higher electrocatalytic activity towards the oxidation of glucose than CuNP, CuNP/GO and CuNP/SWCNT electrodes. This was because the GO/SWCNT composite as substrate material not only possessed excellent conductivity, but also provided large surface area for the high loading of the CuNPs. Meanwhile, the good dispersibility, independent and multi-layer structure of CuNP, could enhance the charge-transport properties, and afford more active sites for the catalytic oxidation of glucose. Under the optimized conditions, the sensor showed a high sensitivity of up to 930.07 μA mM − 1 cm − 2 , with a wide linear range of 1 μM to 4.538 mM and a low detection limit of 0.34 μM (S/N = 3). It also exhibited excellent stability, reproducibility, selectivity, and reliable measurement in real human blood samples. All of these excellent properties made the CuNP/GO/SWCNT composite material promising for the development of effective nonenzymatic glucose sensors. [ABSTRACT FROM AUTHOR]

The intrinsically fragile nature and leakage of the enzymes is a major obstacle for the commercial sensor of a continuous glucose monitoring system. Herein, a dual confinement effect is developed in a three dimensional (3D) nanocage-based zeolite imidazole framework (NC-ZIF), during which the high-loading enzymes can be well encapsulated with unusual bioactivity and stability. The shell of NC-ZIF sets the first confinement to prevent enzymes leakage, and the interior nanocage of NC-ZIF provides second confinement to immobilize enzymes and offers a spacious environment to maintain their conformational freedom. Moreover, the mesoporosity of the formed NC-ZIF can be precisely controlled, which can effectively enhance the mass transport. The resulted GOx/Hemin@NC-ZIF multi-enzymes system could not only realize rapid detection of glucose by colorimetric and electrochemical sensors with high catalytic cascade activity (with an 8.3-fold and 16-fold enhancements in comparison with free enzymes in solution, respectively), but also exhibit long-term stability, excellent selectivity and reusability. More importantly, the based wearable sweatband sensor measurement results showed a high correlation (>0.84, P < 0.001) with the levels measured by commercial glucometer. The reported dual confinement strategy opens up a window to immobilize enzymes with enhanced catalytic efficiency and stability for clinical-grade noninvasive continuous glucose sensor. [Display omitted] • A dual-confinement strategy that can doubly confine high-loading enzymes within NC-ZIF with unusual bioactivity and stability. • The mesoporosity of NC-ZIF can be precisely regulated to optimize the performance of packaged enzymes by adjusting the etching times. • The optimized GOx/Hemin@NC-ZIF catalyst could realize high sensitivity detection of glucose by colorimetric and electrochemical sensors. • The based wearable sweatband sensor measurement results show a high correlation (>0.84, P < 0.001) with the levels measured by commercial glucometer. [ABSTRACT FROM AUTHOR]