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Hybrid composites ZnO/PANI were facily synthesized by a sonication process at room temperature. This procedure is non‐expensive, time/energy saving and environmentally safe. The as‐prepared ZnO/PANI were characterized by FTIR, UV‐vis spectroscopies and SEM in order to investigate the structure and morphology of the studied composites. The samples were used to modify carbon paste electrode (CPE) in order to develop electrochemical biosensors (ZnO/PANI/CPE). The sensing properties of the nanoparticles were evaluated for dopamine, ascorbic acid and uric acid non‐enzymatic detection. The effect of percentage of polyaniline in the composites and the effect of calcination on the biosensor's response were also examined in the present study. It was revealed that the existence of PANI in ZnO/PANI/CPE largely enhanced the electroactive surface area and therefore the sensitivity for electrochemical sensing. A good electrochemical behavior was noted for ZnO/40 wt% PANI‐cal/CPE modified electrode toward DA, AA and UA oxidation. The electroactive surface area of the previously mentioned modified electrode (0.235 cm2) was two times higher than that of the bare electrode (0.117 cm2). The liner relationships between current intensities and concentrations were found to be 0.01–1.4 mM, 0.1–1.3 mM and 0.01–0.12 mM, with detection limit of 0.029 mM, 0.063 mM and 0.007 mM, for DA, AA and UA respectively. In the mixtures of ascorbic acid (AA), dopamine (DA) uric acid (UA) and glucose (Glu) the sensor showed high selectivity of DA with low interference of ascorbic acid by a current change of 14 %. The as‐prepared ZnO/PANI/CPE biosensor displayed a good reproducibility and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • TiO 2 , M x Ti 1-x O 2 (M = V, Ni, Co) synthesized and fabricated on Nickel foam. • DFT and other studies show excellent activity of V 0.03 Ti 0.97 O 2 @NF to detect glucose. • The sensitivity and LOD are found to be 1129.31 μAmM-1cm-2 and 1.8 μM respectively. • Selectivity and stability of V 0.03 Ti 0.97 O 2 @NF are found to be excellent for glucose. • V 0.03 Ti 0.97 O 2 @NF demonstrates a good response toward real samples. Diabetes is a chronic condition that can last a lifetime and has claimed a great number of lives in recent years. This motivated scientists to design a glucose biosensor to monitor and control blood glucose levels in diabetic patients. Herein, hydrothermal derived Vanadium (V), Nickel (Ni), and Cobalt (Co)-doped TiO 2 (M x Ti 1-x O 2 (x = 0.01, 0.02, and 0.03)) was synthesized to achieve the best material to answer the pertaining problem. Of all the materials synthesized, V 0.03 Ti 0.97 O 2 @NF demonstrated the highest level of sensitivity, and selectivity, and has higher electrochemical cycling stability in 0.1 M KOH. It exhibits a very high sensitivity of 1129.31 μAmM-1cm-2 and Limits of Detection (LOD) and Limits of Quantification (LOQ) of 1.8 μM (S/N = 3) and 6.2 μM, respectively, with a broad linear range from 20 μM to 2 mM. The DFT approach was employed computationally to analyze the adsorption of glucose on surfaces of pure TiO 2 and TiO 2 doped with V, Ni, and Co respectively. The research findings highlight that when it comes to its interaction with glucose, pure TiO 2 exhibits significantly less reactivity compared to transition metal-doped TiO 2. Experimentally it shows that the V 0.03 Ti 0.97 O 2 @NF surface has the most sensitive glucose detection capability and it also exhibited significant selectivity towards glucose in the presence of additional interference. It demonstrated 100% retention after cycling stability and had a shelf life of ≃30 days. The V 0.03 Ti 0.97 O 2 @NF-based sensor exhibits accurate glucose sensing, even for human serum samples. [ABSTRACT FROM AUTHOR]

In view of the various stability issues and high cost of enzymatic glucose biosensors, non-enzymatic biosensors have received great attention in recent research and development. Copper oxide (CuO) nanowires (NWs) were fabricated on Cu foil substrate using a simple thermal oxidation method. The phase and morphology of the CuO NWs could be controlled by synthesis temperature. Variation in oxidation states enables CuO NWs to form Cu (III) species, which is crucial in catalysing the eletro-oxidation of glucose. The Cu-based metal/oxide composite electrode works as a non-enzymatic biosensor that adapts to the fast, dynamic change in glucose concentration, with a low saturation concentration (~0.7 mM) and a lower detection limit of 0.1 mM, making CuO NWs an excellent sensor towards impaired fasting glucose. The simplicity, cost-effectiveness and non-toxicity features of this study might make a way for potentially scalable application in glucose biosensing.

A new multi-component nanocomposite electrode was built by anchoring heteropoly blue CoP 6 Mo 18 on NiO-loaded carbon nanofibers (NiO-CNFs) via electrospinning and solvothermal methods. The hybrid electrode can quickly and efficiently detect DA and L-Trp alone or together because of synergism between electronic sponge characteristics of CoP 6 Mo 18 and high porosity conductive network of NiO-CNFs. [Display omitted] • A biosensors was built by anchoring CoP 6 Mo 18 POMs on NiO-CNFs. • The composite electrode has a strong response to DA and DRL in a wider linear range. • The sensor can quickly and efficiently detect DA and L-Trp alone or together. • The synergism of NiO-CNFs and CoP 6 Mo 18 enhance biometrics ability of sensor. Non-enzymatic electrochemical biosensors have great application value in the identification and detection of organic biological small molecules, especially in biomedical detection. In this paper, a carbon-based sensing material consisting of basket-type polyoxometallates (POMs) modified with synergistic multicomponent active centers was prepared. A novel POMs with heteropolyblue properties, {Co(phen) 3 } 3 [{Co(H 2 O) 2 }{Co(H 2 O) 3 } 4 }{Sr ⊂ P 6 MoVI 16 MoV 2 O 73 } 2 ]·8H 2 O (CoP 6 Mo 18), was modified on NiO-loaded carbon nanofibers (NiO-CNFs) to construct novel nanocomposites CoP 6 Mo 18 @NiO-CNFs. Differential pulse voltammetry (DPV) tests show that the nanocomposite electrode had a strong response to L-tryptophan (L-Trp) and dopamine (DA) with lower detection limit of 22.2 nM and 27.8 nM (S/N = 3) in the linear range of 66.7 nM-478 μM and 83.3 nM-437 μM, respectively. The results demonstrated that the modified electrode can quickly and efficiently detect DA and L-Trp alone or together due to catalytic synergy between CoP 6 Mo 18 and NiO-CNFs. The combination of the two materials not only enhances the current response signals of the electrodes to the analytes DA and L-Trp, but also effectively improves the selectivity and stability of the sensor. Importantly, the prepared sensor can be used for trace detection of DA and L-Trp in pre-treated human serum samples in practical applications, and the recovery rate is as high as 98.9 %, which suggests that the CoP 6 Mo 18 @NiO-CNFs/GCE sensor has potential application value in biology and medical fields. [ABSTRACT FROM AUTHOR]

An efficient and robust electrocatalyst is significant for glucose biosensing. The emergence of metal-organic framework (MOF) derived materials opens up new avenues for the development of high-performance glucose sensing catalysts. Herein, MOF derived nickel-cobalt hydroxide supported on conductive copper sheet (NiCo-OH/Cu sheet) is prepared at room temperature. The as-obtained NiCo-OH is endowed with three-dimensional network structure which enables the effective exposure of active materials, sufficient contact between glucose molecule and catalyst. The NiCo-OH/Cu sheet is revealed as good glucose electrochemical sensing material with a wide linear range of 0.05∼6.0 mM and a high sensitivity of 1340 μ A mM -1 cm -2 . Additionally, the as-fabricated NiCo-OH/Cu sheet displays good anti-interference ability and long-term stability., (© 2024 IOP Publishing Ltd.)

Thickness of the electro‐polymerized layer grown on a substrate and used as the recognition element for the analyte is critical to measuring the response of a biosensor, with high sensitivity and accuracy. However, it is difficult to control the thickness during synthesis. A mathematical model is developed in this study that considers thickness of the electro‐polymerized layer in simulating the electrochemical response of a non‐enzymatic biosensor for cholesterol in blood. The model includes transient kinetics and one‐dimensional diffusion of the analyte in the poly‐methyl orange (PMO) recognition layer electrochemically grown on the electrode. The governing partial differential equations resulting from the species conservation balances in the PMO layer are numerically solved. Time and spatial concentration profiles of the analyte in the PMO layer are determined. Model predictions are calibrated with the experimental data for different PMO thicknesses. Interestingly, model predictions show a linear response over the calibrated concentration range of cholesterol for all PMO layer thicknesses. Based on the chronoamperometry measurements, the model predictions for the cholesterol concentrations measured in the laboratory samples were also found to be remarkably accurate. This is the first mathematical model developed to understand the transport and kinetics of an analyte in the electro‐polymerized layer used as the recognition element of a non‐enzymatic biosensor. [ABSTRACT FROM AUTHOR]

Lactate sensors are increasingly used for applications in sports and clinical medicine, but currently have several shortcomings including low sensitivity. We demonstrate a highly sensitive and selective non-enzymatic lactate sensor based on porous nickel oxide by sol-gel based inverse micelle method. The porosity and surface area of nickel oxide depending on the calcination temperature (250, 350, and 450 °C) were compared using electron microscopy and a Brunauer-Emmett-Teller (BET) surface area analyzer. Furthermore, we also compared the chemical state of Ni3+ in porous nickel oxides, which is known to be strongly engaged with electrocatalytic lactate detection, with different calcination temperature. The sensing characteristics were assessed using an amperometric response with a three-electrode system. Owing to a relatively large surface area and high Ni3+/Ni2+ ratio, NiO calcined at 250 °C, exhibit maximum sensitivity at 62.35 μA/mM (cm2), and a minimum detection of limit of 27 μM, although, it has large amount of organic residue because of low calcination temperature. In addition to its sensitivity, a porous nickel oxide electrode also displays good selectivity against other interferents such as l -ascorbic acid, uric acid, and dopamine, further supporting its potential as a non-enzymatic lactate sensor. [ABSTRACT FROM AUTHOR]

A glucose biosensor was developed based on a 4-cyano-4′-pentylbiphenyl (5CB)-filled transmission electron microscopy (TEM) grid cell by coating poly (styrene- b -acrylic acid) (PS- b -PAA) at the 5CB/aqueous interface and immobilising 3-aminophenyl boronic acid (APBA) on the PAA block chains by N -(3-dimethylaminopropyl)- N -ethylcarbodiimide coupling. Binding events between APBA and glucose were translated into homeotropic-to-planar configurational changes of 5CB, which were observed by polarised optical microscopy (POM) under crossed polarisers. This liquid-crystal-based glucose biosensor exhibited high sensitivity (limit of detection: 0.1 mM), even in complex serum and urine samples, high selectivity (against cholesterol, haemoglobin, and urea), and good stability for 40 d. This new and sensitive glucose biosensor has the advantages of low production cost, a simple immobilisation technique, and easy detection with POM, and may be useful for pre-screening glucose levels in human samples (serum and urine). [ABSTRACT FROM AUTHOR]

Graphical abstract Ni(OH) 2 /RGO/Cu 2 O nanocomposite was in-situ -grown on the surface of Cu substrate through a Cu foil-involved one-pot hydrothermal process. As-synthesized Ni(OH) 2 /RGO/Cu 2 O@Cu directly acted as a nonenzymatic sensor which exhibited excellent sensing performance towards glucose and hydrogen peroxide with an ultrahigh sensitivity, low detection limit and wide detection range. Highlights • A Ni(OH) 2 /RGO/Cu 2 O nanocomposite in-situ grown on Cu substrate surface through a Cu foil-involved one-step hydrothermal reaction. • Cu foil as support, Cu source of Cu 2 O, reductant of GO and the subsequent current collector. • 3D hierarchical tubular Ni(OH) 2 architecture provides a high specific surface area facilitating the short diffusion distance for species. • Ultrahigh-sensitivity and low detection limit for glucose and hydrogen peroxide. Abstract A hierarchized Ni(OH) 2 /RGO/Cu 2 O nanocomposite electrode grown on Cu foil was prepared through a facile in-situ one-pot hydrothermal method. Three kinds of strong interfaces of Ni(OH) 2 /RGO, RGO/Cu 2 O and Cu 2 O/Cu were simultaneously formed and thus a sandwich structure of Ni(OH) 2 /RGO/Cu 2 O was constructed on Cu substrate. Without further assembly and modification, as-synthesized Ni(OH) 2 /RGO/Cu 2 O@Cu was directly used as a non-enzymatic sensor, which exhibited a better amperometric response than other non-enzymatic sensors, e.g., detection limit (0.35 μM and 0.20 μM), sensitivity (5350 uA·mM−1·cm-2 and 1706.3 uA·mM−1·cm-2) and linear range (0.5 μM to 7.67 and 7.5 mM) on the detection of glucose and hydrogen peroxide. Furthermore, the non-enzymatic sensor showed good long-term stability and good performance in human blood analysis. The present work gives a new insight in sensor based on metal hydroxide/RGO/metal oxides electrode and its potential application in non-enzymatic glucose and hydrogen peroxide sensing. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen peroxide (H 2 O 2 ) is one of the most universal and essential ingredients in distinct biological tissues. Herein, a novel non-enzymatic sensor based on reduction graphene oxide-persimmon tannin‑platinum nanocomposite (RGO-PT-Pt) was exploited for H 2 O 2 detection. RGO-PT-Pt nanocomposite was prepared by reduction procedure with ascorbic acid as reducing agent and characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV–vis) and Fourier infrared spectroscopy (FT-IR). Taking advantage of high electro-catalytic efficiency of Pt nanoparticles, high electronic conductivity and large surface area of RGO, and significant adsorption ability of PT on metal ions and its prevention of agglomeration to promote RGO dispersion, RGO-PT-Pt nanocomposite revealed better catalytic ability towards H 2 O 2 via a synergistic effect. Under the optimal conditions, the RGO-PT-Pt non-enzymatic biosensor exhibited outstanding electrocatalytic activity towards H 2 O 2 reduction. The amperometric response demonstrated a linear relationship with H 2 O 2 concentration from 1.0 to100 μM with the correlation coefficient of 0.9931. The limit of detection was 0.26 μM (S/N = 3) and the response time was 3 s. Furthermore, the fabricated sensor exhibited a practical applicability in the quantification of H 2 O 2 in human serum samples with an excellent recovery rate. Due to excellent performance such as fast response time, low detection limit, high stability and selectivity, the RGO-PT-Pt non-enzymatic biosensor has potential application in clinical diagnostics. Graphical abstract Unlabelled Image Highlights • A novel non-enzymatic sensor based on RGO-PT-Pt for H 2 O 2 detection was developed. • The RGO-PT-Pt non-enzymatic biosensor was characterized by SEM, XPS, CV and EIS. • The H 2 O 2 biosensor demonstrated a linear relationship from 1.0 to 100 μM with R2 of 0.9931. • The RGO-PT-Pt biosensor showed fast response time, low detection limit and higher selectivity. [ABSTRACT FROM AUTHOR]

Abstract A microwave-assisted synthesis is described for the preparation of bismuth tungstate/graphene nanoribbons (Bi 2 WO 6 @GNRs) nanocomposite as cost-effective alternative to existing hydrothermal method. HR-TEM, XRD, XPS, EDX, BET and Raman characterizations reveal the incorporation of Bi 2 WO 6 flowers on GNRs. The electrochemical and interfacial properties of the composite were probed by voltammetry and impedance studies. The electrocatalytic ability of the composite was assessed by studying the redox reactions of hazardous dihydroxybenzene isomers. Bi 2 WO 6 @GNRs modified screen-printed electrode was found to distinguish the voltammetric signals of catechol and hydroquinone (separation gap of 140 mV, vs. Ag|AgCl), minimizes reaction overpotentials, and amplifies the electrochemical current signal. The effects of concentration scan rate and cross-reactivity are studied. Bi 2 WO 6 @GNRs incorporated sensor displayed detection limits of 5.31 nM and 7.24 nM for catechol and hydroquinone, respectively. The method was found to be practically applicable in the determination of catechol and hydroquinone in water samples and face cream sample, respectively. Graphical abstract Image 1 Highlights • Microwave-assisted synthesis of bismuth tungstate@graphene nanoribbons nanocomposite (Bi2WO6@GNRs). • Excellent electrocatalytic ability towards the sensitive determination of catechol and hydroquinone. • Sub-nanomolar level detection with detection limits of 5.31 and 7.24 nM for catechol and hydroquinone. • Practicality in the real samples of red wine and face cream. [ABSTRACT FROM AUTHOR]

In this study, highly catalytic platinum nanoparticles (PtNPs) were synthesized on polished Au thin-film electrode using surfactant assisted electrochemical technique (SAET) for a high-performance non-enzymatic glucose sensor. Residual surfactants on the fabricated electrodes were removed by dipping into a tetrahydrofuran (THF) solution. The physical characteristics of the electrodes were investigated through FESEM, XRD, and EDX, and the analytical analyses were demonstrated with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. After optimization considering the NP deposition potential and time, dipping time in THF, the fabricated biosensor showed a promising electro-oxidation towards glucose in terms of high sensitivity of 5.87 ± 0.13 μAmM −1  cm −2 , detection limit of 0.235 μM, wide linear range from 0.25–36 mM, fast response lower than 5 s, and good reproducibility and stability. The proposed SAET can be applied to uniform deposition and dispersion of other nanoparticles for numerous applications. Therefore, the proposed sensing platform can be useful to monitor glucose in diagnostic bioprocess monitoring and environmental monitoring. [ABSTRACT FROM AUTHOR]

Herein, the synthesis of novel non-aggregated spinel nickel ferrite, NiFe 2 O 4 nanosheets (NiFe 2 O 4 NSs) and its application towards the selective electrocatalytic reduction of hydrogen peroxide are described. Initially, NiFe 2 O 4 NSs is synthesized by one-step hydrothermal approach, and numerous characterizations deliberately explain the compound's composition and structure. Finally, the NiFe 2 O 4 NSs underwent direct non-enzymatic electrochemistry and succeeded, it as mimicking Horseradish Peroxidase properties. The significance of non-aggregated NiFe 2 O 4 NSs together with good electrocatalytic properties leads the material to the platform for electrochemical sensors. Moreover, NiFe 2 O 4 NSs is fabricated and validated as an enzyme-free biosensor for the sensitive detection of H 2 O 2 . The demonstrated sensor revealed excellent detection of H 2 O 2 with the pico-molar detection limit (12.4 pM), and also it offered good analytical parameters with more extensive linear range and higher sensitivity . Likewise, the non-enzymatic biosensor annexes good durability, reproducibility, and selectivity towards the determination of H 2 O 2 . Due to the nourishing capacity of the prepared NiFe 2 O 4 NSs, it is employed for the enzyme-free detection of H 2 O 2 in human blood and rat brain serum samples. [ABSTRACT FROM AUTHOR]

Cholesterol is one of the main biomarkers for atherosclerosis which can lead to the coronary heart and peripheral arterial diseases. Development of non-enzymatic electrochemical biosensors for the measurements of cholesterol over a wide linear concentration range, with high sensitivity and accuracy is challenging. A novel Cu/Ni bimetal-dispersed carbon nanofiber/polymer nanocomposite (BMCP)-based electrode was developed in this study for the measurements of cholesterol. Dendritic nanofibers of poly methyl orange (PMO), which served as the recognition element for cholesterol, were successfully grown over BMCP, using electro-polymerization. Tested using various electrochemical techniques including chronoamperometry and differential pulse voltammetry, the prepared PMO-BMCP biosensor showed a high sensitivity (226.30 μA mM −1  cm −2 ) and low detection limit (0.002 mg dL −1 ) over 0.04–600 mg dL −1 concentration range, with remarkable linearity (R 2  = 0.999), which were either higher or comparable to most of the cholesterol sensors discussed in literature. The biosensor exhibited good reproducibility and long-time (~8 months) stability of the electrochemical activity. The presence of interfering bioactive agents, namely, glucose, uric acid, creatinine, urea and p-acetamido phenol had negligible effect on the measurement of cholesterol. The proposed material and method described in this study can be used to develop similar non-enzymatic electrochemical biosensors for other bioactive molecules in blood, such as glucose and creatinine. [ABSTRACT FROM AUTHOR]

3-Aminophenyl boronic acid (APBA)-decorated 4-cyano-4′-pentylbiphenyl (5CB) microdroplets were utilized for glucose detection with high specificity and sensitivity. APBA decoration was performed by firstly coating poly(acrylic acid) (PAA) on the 5CB droplet with amphiphilic poly(4-cyanobiphenyl-4′-undecylacrylate-b-acrylicacid) (LCP-b-PAA) and performing covalent bonding of APBA to the PAA chains by EDC coupling between the acrylic groups of PAA and the amine groups of APBA. The binding events between APBA and glucose were translated by configurational change (from radial to bipolar) of the 5CB droplets, observed under a polarized optical microscope with crossed polarizers. The liquid crystal (LC) droplet-based non-enzymatic (NE) biosensor for glucose detection exhibited high sensitivity (detection limit of 0.05 mM) even in complex serum sample, high selectivity against cholesterol, uric acid, and acetaminophen, and good stability for 30 d. This NE-based glucose LC biosensor is cost-effective and highly stable compared to enzyme-based LC glucose biosensors and thus, could replace such enzyme-based biosensors. [ABSTRACT FROM AUTHOR]

ZnO/RGO/ZnO nanocomposite was in-situ anchored on Zn foil through a simple one-step hydrothermal approach. Based on the redox reaction between graphene oxide (GO) and Zn foil, and the electrostatic attraction between the negative-charged GO and positive-charged zinc ions, three strong interfaces of ZnO/RGO, RGO/ZnO and ZnO/Zn were simultaneously constructed, which led to improved electron and ion transfer. As-prepared ZnO/RGO/ZnO@Zn directly acted as sensor for amperometric detection of sunset yellow without further assembling, which exhibited an ultrahigh sensitivity of 20.25 uA μM −1 cm −2 , a low limit of detection (3 nM), a wide linear detection ranging from 0.01 to 5 µM. [ABSTRACT FROM AUTHOR]

A non-enzymatic glucose biosensor was developed by utilizing the zinc oxide nanoparticles (ZnO NPs) synthesized by a novel green method using the leaf extract of Ocimum tenuiflorum . The structural, optical and morphological properties of ZnO NPs characterized by means of X-ray diffraction (XRD), ultraviolet-visible (UV–vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDAX) spectroscopy, and transmission electron microscopy (TEM). The XRD analysis revealed that the ZnO NPs were crystalline and had a hexagonal wurtzite structure. The crystallite size measured by XRD was the same as that measured using SEM and TEM. The UV–vis absorption spectrum estimates the band gap of ZnO NPs present in the range of 2.82 to 3.45 eV. The reduction and formation of ZnO NPs mainly due to the involvement of leaf extract bio-molecular compounds analyzed from the FTIR spectra. The SEM result confirms the morphology of the NPs responsible from the various concentration of leaf extract in the synthesis process. HRTEM analysis depicts the spherical structure of ZnO NPs. The synthesized NPs have the average size ranges from 10 to 20 nm. The fabricated GCE/ZnO glucose sensor represents superior electro catalytic activity that has been observed for ZnO NPs with a reproducible sensitivity of 631.30 μA mM − 1 cm − 2 , correlation coefficient of R = 0.998, linear dynamic range from 1–8.6 mM, low detection limit of 0.043 μM (S/N = 3) and response time < 4 s. [ABSTRACT FROM AUTHOR]

A simple solution based deposition process has been used to fabricate Zn doped Co3O4 electrode as an electrocatalyst for non-enzymatic oxidation of glucose. XRD, HRTEM, SEM, EELS, AFM, EIS was used to characterise the electrode. The addition of Zn as dopant on Co3O4 resulted in enhanced electrochemical performance of Zn:Co3O4 material compared to pristine Co3O4 due to increased charge transferability. The as prepared electrode showed fast response (<7 s) time, good sensitivity (193 μA mM−1 cm−2) in the linear range of 5 μM-0.62 mM, good selectivity towards glucose at a relatively lower applied potential of +0.52 V in 0.1 M NaOH solution. A detection limit of ∼2 μM was measured for the Zn:Co3O4 electrode. The applied fabrication method resulted in good inter and intra electrode reproducibility as was shown by the lower relative standard deviation values (R.S.D). The electrode retained 70 % of initial current response after 30 days. Although the as prepared Zn:Co3O4 electrodes did not result in highest reported sensitivity, and lowest limit of detection; the ease of fabrication and scalability of production, good inter and intra electrode reproducibility makes it a potential candidate for commercial application as glucose sensor. [ABSTRACT FROM AUTHOR]

Different nanostructures of copper oxide (CuO) by in-situ growth on carbon clothes (CC) are prepared to develop ultrasensitive non-enzymatic glucose sensors. The electrochemical performance of the CuO-based electrodes for detecting glucose has been investigated by cyclic voltammetry (CV) and chronoamperometry. The CuO nanosheets (CuO NSs)/CC electrode demonstrates a high sensitivity of 4902 μA mM −1 cm −2 at an applied potential of 0.55 V (vs. Ag/AgCl/3 M KCl) in alkaline solution, and it shows 2973 μA mM −1 cm −2 and 1246 μA mM −1 cm −2 for the CuO nanowires (CuO NWs)/CC and CuO nanoparticles (CuO NPs)/CC, respectively. Ascribing to high conductivity of CC, high specific surface-area from CuO nanostructures, and facilitated charge transfer through in-situ grown structure, the electrodes demonstrate ultrasensitive, selective, stable and fast amperometric sensing (<3 s) of glucose, which presents a new strategy to develop non-enzymatic glucose sensors. [ABSTRACT FROM AUTHOR]

A non-enzymatic acetylcholine (ACh) electrochemical biosensor was constructed based on flower-like NiAl layered double hydroxides (NiAl-LDHs) decorated with carbon dots (CDs). The flower-like NiAl-LDHs with a cross-linking nanosheet structure and high specific surface area were hydrothermally fabricated. Then CDs with negative surface charge were decorated on the NiAl-LDHs with positively charged brucite-like layers to obtain NiAl-LDH/CD composites. Compared with the NiAl-LDHs, the NiAl-LDH/CD composites exhibited enhanced electroconductivity and electrocatalytic performance for ACh oxidation. The NiAl-LDH/CD composites modified glassy carbon electrode had a wide linear response range of 5–6885 μM, high sensitivity of 133.20 ± 0.03 mA M −1 cm −2 and low limit of detection of 1.7 μM, which are superior among the non-enzymatic ACh electrochemical biosensors. The biosensor also exhibited a good durability and long-term stability, and an excellent selectivity for ACh detection. The good performance in the non-enzymatic detection of ACh could be attributed to the synergistic effect between NiAl-LDHs and CDs. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanorods (NRs) have been synthesized via the hydrothermal process. The NRs were grown over a conductive glass substrate. A non-enzymatic electrochemical sensor for hydrogen peroxide (H2O2), based on the prepared ZnO NRs, was examined through the use of current-voltage measurements. The measured currents, as a function of H2O2 concentrations ranging from 10 μM to 700 μM, revealed two distinct behaviours and good performance, with a lower detection limit (LOD) of 42 μM for the low range of H2O2 concentrations (first region), and a LOD of 143.5 μM for the higher range of H2O2 concentrations (second region). The prepared ZnO NRs show excellent electrocatalytic activity. This enables a measurable and stable output current. The results were correlated with the oxidation process of the H2O2 and revealed a good performance for the ZnO NR non-enzymatic H2O2 sensor. [ABSTRACT FROM AUTHOR]

A stable and sensitive non-enzymatic glucose sensor was prepared by modifying a boron-doped diamond (BDD) electrode with nickel (Ni) nanosheets and nanodiamonds (NDs). The NDs were electrophoretically deposited on the BDD surface, and acted as nucleation sites for the subsequent electrodeposition of Ni. The morphology and composition of the modified BDD electrodes were characterized by field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The Ni nanosheet-ND modified BDD electrode exhibited good current response towards the non-enzymatic oxidation of glucose in alkaline media. The NDs significantly extended the potential window. The response to glucose was linear over the 0.2–1055.4-μM range. The limit of detection was 0.05 μM, at a signal-to-noise ratio of 3. The Ni nanosheet-ND/BDD electrode exhibited good selectivity, reproducibility and stability. Its electrochemical performance, low cost and simple preparation make it a promising non-enzymatic glucose sensor. [ABSTRACT FROM AUTHOR]

The history of ferrites comes from many centuries and was fundamental in many fields. Initially, ferrites were extracted directly from nature, but in the last century, scientists learned to produce ferrites with different properties that gave origin to many advances in industrial and instrumental applications. More recently, the designed preparation of ferrites with nanometric size revealed remarkable characteristics. In the last years, different spinel ferrites were used as electroactive layers to build high-performance modified electrodes. In this review, it is presented a critical overview of the utilization of spinel ferrites (with a general formula MFe 2 O 4, where M2+ = Mg2+, Ni2+, Co2+, Cu2+, Mn2+ and Zn2+) to create differentiated voltammetric sensors. The association of these materials with graphene, glassy carbon, carbon nitride, ionic liquids, nanoparticles of noble metals, oxides of transition metals and other materials can produce notable synergic responses towards electrochemical activity. Some of these sensors can produce very sensitive signals and ample concentration ranges for compounds such hydrogen peroxide, glucose and bisphenol A, and present potential for many other applications. Along this review, all these aspects will be discussed and the main results are organized in tables, using as a base the metal associated with the ferrite. • We review the contributions of MFe 2 O 4 materials to obtain enhanced electrochemical sensors. • We present and compare the main strategies to develop MFe 2 O 4 -based electrochemical sensors. • The main preparation methods in the design of MFe 2 O 4 materials and electrode modification. • Quo Vadis: The top 10 materials for the main target species (glucose, H 2 O 2 and bisphenol A). • Recent trends and perspectives on electrochemical sensors based on MFe 2 O 4. [ABSTRACT FROM AUTHOR]

Hole-transporting materials with tunable structures and properties are mainly applied in organic light-emitting diodes as transport layer. But their catalytic properties as signal amplifiers in biological assays are seldom reported. In this paper, a starburst molecule, 4,4,4″-tri(N-carbazolyl)-triphenylamine (TCT), containing a triphenylamine as the central core and three carbazoles as the peripheral functional groups was designed and synthesized. Subsequently, the hole-transporting material based on the TCT polymer, poly(TCT) (PTCT), was achieved via a low-cost electrochemical method and exploited as an efficient metal-free electrocatalyst for non-enzymatic glucose detection. Here, this hole-transporting material served three purposes: electrochemical recognition (owing to hydrogen bonding interaction and the biomimetic microenvironment created by the polymer), electrocatalysis (owing to the hole-transporting capability of triphenylamine and the catalytic property of carbazole), and signal amplification (owing to energy migration along the conductive polymer backbone). The electrocatalytic and sensing performances of the sensor based on PTCT were evaluated in detail. Results revealed that the PTCT film could efficiently catalyze the oxidation of glucose at a less-positive potential (+0.20 V) in the absence of any enzymes. The response to glucose was linear in the concentration range of 1.0–6000 μM, and the detection limit was 0.20 μM. With good stability and selectivity, the proposed sensor could be feasibly applied to detect glucose in practical samples. The encouraging sensing performances suggest that the hole-transporting material is one of the promising biomimetic catalysts for electrocatalysis and relevant fields. [ABSTRACT FROM AUTHOR]

A novel flexible, non-enzymatic glucose sensor with ultrahigh sensitivity and fast response, based on NiAl-layered double hydroxide (NiAl-LDH) modified carbon cloth (CC) electrode, has been successfully fabricated. Curved NiAl-LDH sheets based 3D macroporous films were prepared by an in situ growth technique, which provided a large surface area and great electronic/ionic conductivity between CC and LDH. The resulting electrodes exhibit ultrahigh sensitivity toward glucose detection, providing a sensitivity up to 14.13 mA mM −1 cm −2 and response time less than 1 s. In addition, the electrocatalytic activity of the glucose sensor decreases in proportion to the area of the CC. Half-sized electrodes provide a sensitivity up to 13.48 mA mM −1 cm −2 and response time less than 2 s. Due to the unique structure of the resulting electrode, this flexible application and ultrahigh sensitivity of the NiAl-LDH/CC sensor open up a new type of hybrid material for portable, low-cost glucose sensors. [ABSTRACT FROM AUTHOR]

A hierarchical MFI zeolite, with typical micro/meso bimodal pore structures, was prepared by desilication method. CuO nanoparticles (NPs) were incorporated into the hierarchical MFI zeolite by impregnation method. CuO/hierarchical zeolite composites were characterized by X-ray diffraction, transmission electron microscopy and nitrogen sorption. It is shown that the CuO nanoparticles are mostly dispersed in the mesopores with remaining of the crystallinity and morphology of the host zeolite. CuO nanoparticles located in hierarchical zeolite exhibit the excellent electrocatalytic performances to oxidation of glucose in alkaline media. The electrocatalytic activity enhances with increasing the loading content of CuO from 5% to 15%. The composites were fabricated for nonenzyme glucose sensing. Under the optimal conditions, the sensor shows a wide linear range from 5 × 10 −7 to 1.84 × 10 −2 M with a low detection limit of 3.7 × 10 −7 M. The sensor also exhibits good repeatability, long-term stability as well as high selectivity against interfering species. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanorods (NRs) have been synthesized via the hydrothermal process. The NRs were grown over a conductive glass substrate. A non-enzymatic electrochemical sensor for hydrogen peroxide (H2O2), based on the prepared ZnO NRs, was examined through the use of current-voltage measurements. The measured currents, as a function of H2O2 concentrations ranging from 10 μM to 700 μM, revealed two distinct behaviours and good performance, with a lower detection limit (LOD) of 42 μM for the low range of H2O2 concentrations (first region), and a LOD of 143.5 μM for the higher range of H2O2 concentrations (second region). The prepared ZnO NRs show excellent electrocatalytic activity. This enables a measurable and stable output current. The results were correlated with the oxidation process of the H2O2 and revealed a good performance for the ZnO NR non-enzymatic H2O2 sensor.

The MoOx/AuNPs composite film modified glassy carbon electrode was fabricated by electro-depositing simultaneously gold nanoparticles and molybdenum oxides using cyclic voltammetry. The morphology and topography of the MoOx/AuNPs composite were characterized by scan electron microscopy and X-ray photoelectron spectroscopy respectively, and the electrocatalytic oxidation of glucose at the MoOx/AuNPs composite film was investigated and analyzed in detail. It was shown that the MoOx/AuNPs composite was of strong electrocatalytic activity towards oxidation of glucose as well as other saccharides, so that an attempt was made for direct voltammetric determination of glucose. Then the positive scan polarization reverse catalytic voltammetry was proposed for the first time. Based on this method, the pure oxidation current was extracted by subtraction of the blank current in the reverse scan. The current sensitivity was enhanced tremendously and the signal to noise ratio was improved adequately. The electrocatalytic oxidation of glucose at the MoOx/AuNPs modified electrode was performed in alkaline medium, a wide linear range from 0.01 mmol/L to 4.0 mmol/L of glucose, a higher current sensitivity of 2.35 mA/(mmol/L.m2), and a lower limit of detection of 9.01 μmol/L (at signal/noise=3) were achieved. In addition, the electrocatalytic oxidation of other saccharides such as lactose, fructose and sucrose was also evaluated. [ABSTRACT FROM AUTHOR]

In view of the various stability issues and high cost of enzymatic glucose biosensors, non-enzymatic biosensors have received great attention in recent research and development. Copper oxide (CuO) nanowires (NWs) were fabricated on Cu foil substrate using a simple thermal oxidation method. The phase and morphology of the CuO NWs could be controlled by synthesis temperature. Variation in oxidation states enables CuO NWs to form Cu (III) species, which is crucial in catalysing the eletro-oxidation of glucose. The Cu-based metal/oxide composite electrode works as a non-enzymatic biosensor that adapts to the fast, dynamic change in glucose concentration, with a low saturation concentration (~0.7 mM) and a lower detection limit of 0.1 mM, making CuO NWs an excellent sensor towards impaired fasting glucose. The simplicity, cost-effectiveness and non-toxicity features of this study might make a way for potentially scalable application in glucose biosensing.

Abstract: Gold nanostructures with controllable morphologies were synthesized by electrochemical deposition on phosphorus doped diamond-like carbon (DLC:P) film surfaces. The morphology of the as-synthesized gold nanostructures controlled by deposition potentials affected the electrocatalytic behavior of Au/DLC:P electrodes. The gold nanostructures obtained at −0.1V showed a 3D flower-like morphology (consisting of staggered nanosheets), and exhibited higher electrocatalytic activity towards glucose electrooxidation at the potential below 0.1V in alkaline media compared with other gold nanostructures (hemispherical and branched clusters) in terms of more unsaturated gold (220) and (311) crystal faces and monolayer oxide mediators on gold surfaces. The gold nanostructures with controllable morphologies were hence promising for the development of an electrocatalyst of non-enzymatic glucose sensor. [Copyright &y& Elsevier]

Abstract: In this paper, ultralong MnOOH nanowires were first synthesized via a facile solution method without using any organic surfactants. A novel non-enzymatic hydrogen peroxide (H2O2) sensor was then developed on the base of MnOOH nanowire composite film modified glass carbon electrode (GCE). The resulted biosensor exhibited excellent performance for H2O2 determination with a wide linear range (1.5×10−4–1.6mM), a highly reproducible response (R.S.D. of 2.7%) and long-term stability. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective non-enzymatic hydrogen peroxide sensor. [Copyright &y& Elsevier]

Abstract: An enzyme-free amperometric glucose sensor of gold nanoparticle-constituted nanotube array electrode is presented. The resulted gold nanotube array electrode with significantly enhanced surface roughness shows prominent catalytic activity toward the electrooxidation of glucose in a pH 7.4 phosphate buffer (PBS) solution and thus can be used to individually or simultaneously determine glucose and the common interfering molecule of ascorbic acid (AA). In the case of glucose detection, the amperometric responses show a linear relationship to glucose concentration in the range of 1mM–42.5mM with a detection limit down to 10μM. The present non-enzymatic glucose electrochemical biosensor shows a good stability and reproducibility. [Copyright &y& Elsevier]

Potentiometric biosensors based on flexible arrayed silver paste electrode and copper-doped zinc oxide sensing film modified by iron-platinum nanoparticles (FePt NPs) are designed and manufactured to detect lactate in human. The sensing film is made of copper-doped zinc oxide (CZO) by a radio frequency (RF) sputtering system, and then modified by iron-platinum nanoparticles (FePt NPs). The surface morphology of copper-doped zinc oxide (CZO) is analyzed by scanning electron microscope (SEM). FePt NPs are analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The average sensitivity, response time, and interference effect of the lactate biosensors are analyzed by voltage-time (V-T) measurement system. The electrochemical impedance is analyzed by electrochemical impedance spectroscopy (EIS). The average sensitivity and linearity over the concentration range 0.2–5 mM are 25.32 mV/mM and 0.977 mV/mM, respectively. The response time of the lactate biosensor is 16 s, with excellent selectivity. [ABSTRACT FROM AUTHOR]

• NiCo-NiCoO 2 /C is used as an electrocatalyst for non-enzymatic glucose biosensors. • Its nanocage structure enables promising sensitivity and durability. • Alloy particles and carbon coating contribute to improvement of electron transfer. • The proposed material is applied for glucose determination in serum samples. Hybrid transition metals/metal oxides/carbon bases with adjustable structures are becoming more and more important and attractive as electrode materials for electrocatalysis of glucose. Herein, we demonstrate the fabrication of carbon encapsulated hollow cage NiCo-NiCoO 2 composite (NiCo-NiCoO 2 /C), which were synthesized by a two-step procedure involving preparation of nickel-cobalt Prussian blue analogue (Ni-Co PBA) derivative (NiO-NiCo 2 O 4) and an organic carbon source, and the synthesis of the nanocomposite at 400°C for direct carbonization and reduction process in an Ar atmosphere. As a multi-component electrocatalyst for glucose oxidation in alkaline solution, the unique structure provides a large accessible surface area, while the uniformly distributed NiCoO 2 , NiCo, and C effectively catalyze and facilitate the glucose reaction. The sensitivity of the catalyst were 340.4 μA mM−1 cm−2 and 56.1 μA mM−1 cm−2 in the linear concentration ranges of 0.1 μM-600 μM and 0.9 mM-6.3 mM, respectively, and the LOD was 0.03 μM with good reproducibility and long-term stability. Besides, the effective performance of the sensor material in detecting glucose in real human serum has been recognized. The NiCo-NiCoO 2 /C annealed at an appropriate temperature has high electronic conductivity, large surface area, and faster ion/electron transfer at the electrode and electrolyte-electrode interface, resulting in a higher electrocatalytic oxidation of glucose ability. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel hierarchical nanostructure was prepared by integrating PB with Ti 3 C 2. • The synergistic effect produced favorable structure and performance optimization. • A sensitive and selective non-enzymatic electrochemical sensor for H 2 O 2 was built. • The proposed PB/Ti 3 C 2 showed negligible cytotoxicity to normal fibroblast cells. • Real-time and in-situ detection of H 2 O 2 released from living cells was realized. The rapid and accurate detection of H 2 O 2 levels in living cells has important significance in the early-diagnosis of many diseases. In this paper, a non-enzymatic electrochemical biosensor based on Prussian blue (PB) nanoparticles (NPs) intercalated Ti 3 C 2 nanosheets (PB NPs/Ti 3 C 2) was fabricated as a platform for detecting H 2 O 2. Physico-chemical characterizations revealed the optimized morphology and enlarged surface area of PB NPs/Ti 3 C 2. When applied to determine H 2 O 2 at the optimal potential, wide linear response in the ranges of 0.6 μM–63.6 μM and 63.6 μM–254 μM, a low limit of detection (0.20 μM), satisfactory stability and anti-interference ability were obtained at PB/Ti 3 C 2 /GCE for the synergistic effect between PB and Ti 3 C 2 on the structure optimization and performance complementation. Moreover, the prepared PB/Ti 3 C 2 showed negligible cytotoxicity to normal fibroblast cells at all tested time points and concentrations, validating its potential application in living cell concerned fields. For proof of concept, the proposed PB/Ti 3 C 2 /GCE realized the real-time and in-situ detection of H 2 O 2 secreted from living HeLa cells. Overall, the biocompatible PB/Ti 3 C 2 sensing interface with a hierarchical structure would be a competitive candidate for H 2 O 2 monitoring in biological samples or cellular investigation. [ABSTRACT FROM AUTHOR]

• Hierarchical core-shell Co 3 O 4 /CuO nanorod arrays were fabricated. • The uniform core-shell structure offers abundant electro-active sites. • The heterostructure favors electron transport within the electrode. • Co 3 O 4 /CuO on carbon cloth can be directly used as non-enzymatic glucose sensor. • The glucose sensor shows a high sensitivity and good selectivity. A hierarchical core-shell Co 3 O 4 /CuO nanorod array (NRA) anchored on flexible carbon cloth (CC) has been fabricated through a stepwise process consisting of magnetron sputtering of Cu, its anodic oxidation, and chemical bath deposition of Co 3 O 4. The structure, composition and morphology of the synthesized Co 3 O 4 /CuO NRA on CC were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The glucose sensing performance of the Co 3 O 4 /CuO NRA on CC electrode was investigated by cyclic voltammetry and chronoamperometry. The sensor exhibited a high sensitivity of 5405 μA mM−1 cm−2 with a fast response time (t 90 = 1.9 s) and a low detection limit of 0.38 μM. The electrode also showed outstanding selectivity toward various interferences. These results indicate that the Co 3 O 4 /CuO nanocomposites may be promising electrode materials for electrochemical biosensing. [ABSTRACT FROM AUTHOR]

Biosensor systems for wearable continuous monitoring are desired to be developed into conformal patch platforms. However, developing such patches is very challenging owing to the difficulty of imparting materials and components with both high stretchability and high performance. Herein, we report a fully stretchable microfluidics-integrated glucose sensor patch comprised of an omnidirectionally stretchable nanoporous gold (NPG) electrochemical biosensor and a stretchable passive microfluidic device. A highly electrocatalytic NPG electrode was formed on a stress-absorbing 3D micropatterned polydimethylsiloxane (PDMS) substrate to confer mechanical stretchability, high sensitivity, and durability in non-enzymatic glucose detection. A thin, stretchable, and tough microfluidic device was made by embedding stretchable cotton fabric as a capillary into a thin polyurethane nanofiber-reinforced PDMS channel, enabling collection and passive, accurate delivery of sweat from skin to the electrode surface, with excellent replacement capability. The integrated glucose sensor patch demonstrated excellent ability to continuously and accurately monitor the sweat glucose level.