•Pb nanowires-Au nanoparticles nanostructure decorated reduced graphene oxide were synthesized for the first time.•A novel non-enzyme H2O2 sensor was fabricated based rGO-Pb NWs-GNPs by a facile electrodeposition method.•The sensor exhibited good catalytic ability to the reduction of H2O2.•The study provides a potential platform and practicable approach to fabricate various of non-enzymatic amperometric sensors.Graphene sheets are a sp2-hybridized carbon material that offer extraordinary electrical conductivity and excellent thermal and mechanical properties. They are expected to find use in a wide variety of applications. In this study, a new novel electrocatalyst, a Pb nanowires-Au nanoparticles nanocomposite decorated with reduced graphene oxide (rGO-Pb NWs-Au NPs), was successfully synthesized by an effective and simple approach. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy were employed to observe the as-prepared nanomaterial. In addition, the electrochemical behaviors of a rGO-Pb NWs-Au NPs-modified glassy carbon (GC) electrode were evaluated by cyclic voltammetry and chronoamperometry. The final prepared sensor exhibited favorable electroreduction activity towards H2O2 with a remarkable sensitivity of 552.43 µA mM−1 cm−2, a wide linear range of 0.005–1.25 mM, a detection limit of 0.6 µM and a rapid response time (within 5 s). Moreover, the sensor also exhibited good reproducibility, selectivity and stability. Therefore, the present work also provides a potential practicable approach to fabricate various of non-enzymatic amperometric sensors, such as sensors for the detection of glucose, urea, ascorbic acid and dopamine.

A facile and effective strategy to fabricate non-enzymatic H2O2 sensor was developed based on Nafion/Platinum nanoparticles/reduced graphene oxide (Nafion/Pt NPs/RGO) nanocomposite modified glassy carbon (GC) electrode. The morphology of Nafion/Pt NPs/RGO nanocomposite was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, Fourier transform infrared spectrum (FT-IR), and X-ray diffraction (XRD) spectrum respectively. The electrochemical properties of the prepared H2O2 sensor were evaluated by cyclic voltammetry and chronoamperometry. The prepared H2O2 sensor exhibited excellent electroreduction activity toward H2O2 with a wide linear range of 0.005–3 mM, a remarkable sensitivity of 132.8 μA mM−1 cm−2, and a low detection limit of 0.4 μM (S/N = 3). In addition, it showed good selectivity, reproducibility, and long-term stability. The excellent performance of the sensor might be attributed to the synergic effect of nanohybrids. These favorable results indicated that the prepared Nafion/Pt NPs/RGO nanocomposite is promising for fabricating non-enzymatic H2O2 sensor.

•It is the first time to prepare a sensor focused on AA detection using CA-MWCNTs-PEDOT/GCE.•CA-MWCNTs-PEDOT nanocomposite was fabricated by a facile electrodeposition method.•The cationic PEDOT film could interact with negatively charged AA at a low potential.•The oxidation peaks of interfering species (DA, UA) could be distinguished clearly.•The prepared sensor had ultra-high sensitivity and linear range detection.The poly (3,4-ethylenedioxythiophene) (PEDOT) nanomaterial was synthesised by a facile electrodeposition on a glassy carbon electrode (GCE) modified by carboxylated multi-wall carbon nanotubes (CA-MWCNTs). The nanocomposite was characterized using transmission electron microscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy and fourier transform infrared spectroscopy. Moreover, a highly sensitive ascorbic acid (AA) sensor was developed based on the nanocomposite. Owing to the combination of the advantages of CA-MWCNTs and PEDOT, the modified electrode exhibited excellent electro-catalytic activity for AA detection which was investigated in detail by cyclic voltammetry and chronoamperometry. The cationic PEDOT film on CA-MWCNTs could interact with anionic AA in neutral PBS at a low potential and distinguish the oxidation peaks of common interfering species. The effects of electrodeposition time and pH value on the current responses of the modified electrode towards AA were optimized to obtain the maximal sensitivity. The prepared AA sensor demonstrated high sensitivity (1699.36 μA mM− 1 cm− 2), wide linear range detection (100 μM to 20 mM), low detection limit (4.2 μM), rapid response time (less than 4 s), good selectivity and long-term stability. This work presented a facile approach for future research in AA amperometric sensors.

•RGO/Pt-Ag NPs nanocomposite was prepared by a facile strategy.•A novel non-enzyme H2O2 sensor was fabricated based RGO/Pt-Ag NPs.•The H2O2 sensor exhibited good catalytic ability to the reduction of H2O2.•The study provides a promising approach for the fabrication of graphene-bimetallic metal.A new electrocatalyst, Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide nanocomposite, was successfully synthesized by a facile, eco-friendly and controllable route. The morphological characterization of RGO/Pt-Ag NPs nanocomposite was examined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, X-ray diffraction (XRD) spectrum, and Fourier transform infrared spectrum (FT-IR), respectively. And then, the RGO/Pt-Ag NPs nanocomposite was immobilized on the surface of glassy carbon (GC) electrode to fabricate a novel and highly sensitive non-enzymatic hydrogen peroxide sensor. The electrochemical behaviors of the prepared sensor were investigated by cyclic voltammetry and chronoamperometry. The sensor showed excellent performance toward H2O2 with sensitivity as high as 699.6 μA mM−1 cm−2 and 402.7 μA mM−1 cm−2, wide linear range of 0.005–1.5 mM and 1.5–7 mM, and low detection limit of 0.04 μM (S/N=3). Moreover, the prepared hydrogen peroxide sensor was applied to in real samples with satisfactory results. These excellent results indicate that the prepared RGO/Pt-Ag NPs nanocomposite has broad application prospect in the field of sensors.

•RGO/MnO2/AuNPs was prepared by a facile, eco-friendly and controllable route.•MnO2 and AuNPs attached to RGO sheets owing to the oxygenated functional groups.•The sensors were fabricated by taking full advantage of the synergistic effect.•The sensors showed outstanding electrochemical performance.•The study provides a promising approach to fabricate graphene–metal–metal oxide nanocomposite.In this paper, reduced graphene oxide (RGO)/manganese dioxide (MnO2)/gold nanoparticles (AuNPs) nanocomposite was prepared by a facile, eco-friendly and controllable route, and the morphology of RGO/MnO2/AuNPs nanocomposite was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, X-ray diffraction (XRD) spectrum, and Fourier transform infrared spectrum (FT-IR), respectively. And then, taking full advantage of the synergistic effect among RGO, MnO2 and AuNPs, poly(diallyldimethylammonium chloride) (PDDA)-functionalized RGO/MnO2/AuNPs nanocomposite was immobilized on the surface of glassy carbon (GC) electrode to fabricate a novel nonenzymatic hydrogen peroxide sensor, and the results demonstrated that the sensor showed excellent electrocatalytic activity toward H2O2 with ultrahigh sensitivity of 1132.8 μA mM−1 cm−2 and low detection limit of 0.6 μM (S/N = 3). In addition, a glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) on the surface of the PDDA-RGO/MnO2/AuNPs-modified GC electrode. In glucose determination, the glucose biosensor exhibited excellent performance with a high sensitivity of 83.7 μA mM−1 cm−2, a low detection limit of 1.8 μM (S/N = 3), and a small Km value of 1.54 mM. Moreover, the prepared hydrogen peroxide sensor and glucose biosensor were applied to in real samples with satisfactory results, indicating the prepared sensors are promising in practical application.

A facile and effective approach to prepare glucose biosensor was developed based on chitosan-reduced graphene oxide-Au nanoparticles (CS-RGO-AuNPs) hybrids modified Pt electrode. Here CS which has many amino groups along its macromolecular chains and possesses good hydrophilic capability was used as reductant and stabilizer to transform GO into RGO. And one-pot warm bath method was employed to fabricate CS-RGO-AuNPs hybrids. The nanocomposites provided a good micro-bioenvironment for glucose oxidase (GOD) to facilitate electrocatalysis of glucose. The resulting biosensor exhibited a wide linear range of 15 μM to 2.13 mM, with a remarkable sensitivity of 102.4 μA mM−1 cm−2, a detection limit of 1.7 μm estimated at a signal-to-noise ratio of 3 and fast response time (within 5 s). Moreover, it showed good reproducibility, anti-interference ability and long-term stability. It showed that as-prepared CS-RGO-AuNPs nanohybrids not only exhibit efficiency for enzyme immobilization but also are of great importance for amplifying the sensor response. So the current work could provide a feasible approach and potential platform to fabricate a variety of enzymatic amperometric sensors.

•Use of silver nanowires in fabrication of novel non-enzyme H2O2 sensor.•The silver nanowires exhibited good catalytic ability to the reduction of H2O2.•Cyclic voltammetry scanning favored to activate electrochemical properties.•Sensor showed favorable performances at a low potential of −0.2 V vs. Ag/AgCl.A novel strategy to fabricate a hydrogen peroxide (H2O2) sensor was developed based on silver nanowires modified Pt electrode. The sensor was fabricated by simple casting of silver nanowires (Ag NWs) aqueous solution on a Pt electrode. Silver nanowires were synthesized by an l-cysteine-assisted poly (vinyl pyrrolidone) (PVP)-mediated polyol route. UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the prepared nanowires. The electrochemical properties of H2O2 sensor were evaluated by cyclic voltammetry (CV) and chronoamperometry. The as-obtained silver nanowires exhibited favorable electroreduction activity toward H2O2, and results indicated that the Ag NWs modified Pt (Ag NWs/Pt) electrode might be gifted from CV scanning with higher surface area and more active sites that afford more effective surface exposure in the electrode–electrolyte interface and consequently improved electrochemical properties. At the applied potential of −0.2 V vs. Ag/AgCl, the Ag NWs/Pt electrode as an enzyme-free sensor exhibited a wide linear range of 0.5 μM–30 mM to H2O2, with a remarkable sensitivity of 9.45 μA/mM, a detection limit of 0.2 μM estimated at a signal-to-noise ratio of 3 and fast response time (within 5 s). Moreover, it showed good reproducibility, anti-interferant ability and long-term stability. The excellent performance of the sensor might be attributed to the well-defined silver nanowires with special catalytic activity.

•Perpendicularly immobilized FWCNTs (p-FWCNTs) on Au surface through wet chemical approaches for the first time.•Innovatively used conductive thionine to instead of 11-amino-n-undecanethiol (AUT) for aligned CNTs.•Electrodeposited Pt nanoparticles (PtNPs) on p-FWCNTs/Thionine/Au electrode surface for fabricating non-enzymatic H2O2 sensors with the remarkable sensitivity 229.7 μA mM−1 cm−2 and successfully applied the sensor on detecting H2O2 in real samples.•Prepared (PDDA/GOx)8/(PAA/PVS)3/p-FWCNTs/Thionine/Au glucose biosensor with improved sensitivity by the layer-by-layer self assembly technique and applied it in biological sample analysis.•Constructed an ideal platform for the development of various highly sensitive sensors.In this paper, we innovatively immobilized few-walled carbon nanotubes (FWCNTs) perpendicularly on Au surface through conductive thionine instead of aminoalkanethiols so as to improve electrochemical properties. Because FWCNTs own smaller aggregates, stronger chemical corrosion resistant, and higher conductivity than single-walled carbon nanotubes (SWCNTs), and thionine is a good electron transfer mediator can provide amino and sulfhydryl groups playing the same function as insulating aminoalkanethiols. The strategy for obtaining perpendicularly aligned FWCNTs (p-FWCNTs) is electrostatically assembled thionine and 11-amino-n-undecanethiol (AUT) on Au surface via Au-S bond to provide amino groups for covalently combining terminus-carboxylated FWCNTs, we confirmed and compared the results by AFM, Raman spectroscopy and electrochemical methods. In order to prove the constructed basement has excellent electrochemical properties can provide a good platform for sensors fabrication, we developed a novel non-enzymatic hydrogen peroxide (H2O2) sensor by electrodepositing Pt nanoparticles (PtNPs) on p-FWCNTs/Thionine/Au electrode surface, and verified the result by TEM, EDX and electrochemical techniques. Furthermore, polyallylamine (PAA) and poly(vinyl sulfate) (PVS) permselective layer, poly(diallyldimethylammonium) (PDDA) and glucose oxidase (GOx) multilayer films were layer-by-layer self-assembled on p-FWCNTs/Thionine/Au surface to fabricate a glucose biosensor. Either the non-enzymatic H2O2 sensor or the enzyme-based glucose biosensor showed good sensitivity, selectivity, reproducibility and stability, both them had been applied for biological sample analysis with satisfactory results. The results show that the p-FWCNTs/Thionine/Au electrode can work as an ideal platform for the development of highly sensitive sensors, coupled with p-FWCNTs are rich in functional groups could be used for fabricating diverse sensors.

In this paper, a highly sensitive electrochemical sensor for dissolved oxygen was prepared. A glassy carbon electrode was modified with silver nanodendrites that were synthesized by electrochemical deposition on the electrode without the use of a surfactant or template. The electrode displayed efficient electrocatalytic reduction of dissolved oxygen to form hydroxy ions via a four-electron reduction pathway, and a significant decrease in the respective overvoltage. The sensor responded linearly to dissolved oxygen in the 1.0–66.7 μM concentration range, and had a remarkably good sensitivity (0.169 μA μM−1) at an applied potential of −300 mV (vs. Ag/AgCl). The lower detection limit was 0.043 μM (at the signal-to-noise ratio of 3), and the response time was 5 s. The good performance was attributed to the enlarged electro-active surface of the dendritic silver nanostructures and to the efficiency of electron transfer between dissolved oxygen and the electrode. The sensor also showed good reproducibility, long-term stability, and relative good selectivity.

•We fabricated the BLG-MWCNTs-GNPs nanocomposite through a facile method.•GNPs were decorated on BLG-MWCNTs easily owing to the sulfhydryl groups.•The nanocomposite had excellent electrocatalytic activity and biocompatibility.•A glucose biosensor based on the nanocomposite had satisfactory performances.A facile approach was developed for the preparation of nanocomposite based on β-lactoglobulin (BLG)-functionalized multi-wall carbon nanotubes (MWCNTs) and gold nanoparticles (GNPs) for the first time. Owing to the amphipathic nature, BLG can be adopted onto the surface of MWCNTs to form BLG-MWCNTs with uniform dispersion in water. Taking advantage of sulfhydryl groups on BLG-MWCNTs, GNPs were decorated on the BLG-MWCNTs-modified glassy carbon electrode (GCE) by electrodeposition. The nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy and X-ray spectroscopy analysis. Cyclic voltammetry and chronoamperometric method were used to evaluate the electrocatalytic ability of the nanocomposite. Furthermore, a glucose biosensor was developed based on the immobilization of glucose oxidase with cross-linking in the matrix of bovine serum albumin (BSA) on the nanocomposite modified GCE. The resulting biosensor exhibited high sensitivity (3.98 μA mM−1), wider linear range (0.025–5.5 mM), low detection limit (1.1 μM at the signal-to-noise ratio of 3) and fast response time (within 7 s) for glucose detection.

We have developed an effective strategy to fabricate a novel non-enzymatic nitrite sensor. Copper nanodendrites (Cu-NDs) and reduced graphene oxide (RGO) were successively deposited on glassy carbon electrode (GCE) via a simple and two-step electrodeposition method. The fabricated sensor showed an excellent electrocatalytic activity for nitrite reduction. Moreover, the effects of electrodeposition circles, Cu2+ concentration, pH value and detection potential on the current responses of Cu-NDs/RGO/GCE toward nitrite were optimized to obtain the maximal sensitivity. Under optimal experimental conditions, Cu-NDs/RGO/GCE demonstrated the low detection limit of 0.4 μM nitrite (signal-to-noise ratio, S/N = 3), the high sensitivity of 214 μA mM−1 cm−2, and the wide linear range from 1.25 × 10−3 to 13 mM. The superior response of the sensor to nitrite was mainly attributed to the enlarged surface-to-volume ratio with more electroactive sites and the synergistic effect of Cu-NDs and RGO. This work presented a feasible approach for future research in non-enzymatic amperometric sensors and other surface functionalizing.

Silver nanostructures of different morphologies including well-defined dendrites were synthesized on an Au substrate by a simple surfactant-free method without using any template. The morphology of the material was investigated by field-emission transmission electron microscopy and scanning electron microscopy. The crystal nature of the dendritic nanostructure was revealed from their X-ray diffraction and electron diffraction patterns. Effects of applied potential, electrolysis time, and the solution concentration were studied. The possible formation mechanism of the dendritic morphology was discussed from the aspects of kinetics and thermodynamics based on the experiment results. The H2O2 electroreduction ability of the dendritic materials was characterized. Use of silver dendrite-modified electrode as H2O2 sensor was also demonstrated.

Polyelectrolyte multilayer microcapsules with entrapped horseradish peroxidase (HRP) have been prepared via a layer-by-layer (LbL) self-assembly strategy of polycation and polyanion on CaCO3 microparticles as templates. Preparation conditions have been studied and optimized. Within the investigated ranges, use of buffer solutions with lower pH value or lower ionic strength in the buffer solution for polyelectrolyte self-assembly has resulted in thinner polyelectrolyte film and higher permeability of the microcapsules. For dissolving the CaCO3 templates, use of weakly acidic (pH 4.0) buffer solution in place of routinely used EDTA reagent has improved the catalytic activity of microcapsules. The HRP-containing microcapsules have exhibited catalytic activity to pyrogallol as substrate, while the catalytic activity to 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS) was severely suppressed. No less than 90% of the maximum enzymatic activity to pyrogallol has remained after 30 days. Promising prospects in various biocatalysis applications have been expected for the enzyme microcapsules, due to their selective permeability, stability and reusability.Highlights► Preparation method for enzyme-containing microcapsules was improved. ► Selective permeability to different substrates for one enzyme was firstly shown. ► Enzymatic activity was improved by replacement of the metal chelating reagent EDTA. ► More than 90 % of the maximum enzymatic activity remained after 30 days storage.

Well-defined silver (Ag) dendritic nanostructures were successfully synthesized by electrodeposition without the use of any template or surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the as-prepared Ag nanomaterials. These dendrites are aggregates of Ag nanoparticles, which are highly crystalline in nature. The concentration of AgNO3 affects the shape of the nanoparticles. In addition, the electrochemical properties of the Ag dendrite-modified glassy carbon electrode (Ag/GC) were characterized by cyclic voltammetry and chronoamperometry. Results indicated that the as-obtained Ag dendrites exhibited favorable electroreduction activity towards oxygen (O2) and hydrogen peroxide (H2O2). When used as a sensor, the Ag/GC electrode exhibited a wide linear range of 0.005–12 mM H2O2, with a remarkable sensitivity of 7.39 μA/mM, a detection limit of 0.5 μM, estimated at a signal-to-noise ratio of 3, and a rapid response time (within 5 s). Moreover, the electrode showed good reproducibility, anti-interferant ability and long-term stability.

A silver nanowires modified platinum (Ag NWs/Pt) electrode was developed for simultaneous and selective determination of chloride, bromide and iodide ions by cyclic voltammetry in aqueous solutions. Silver nanowires were synthesized by an l-cysteine-assisted poly (vinyl pyrrolidone) (PVP)-mediated polyol route. X-ray diffraction (XRD) and scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were employed to investigate the prepared nanowires. The intrinsic high surface area and the fast electron transfer rate ascribed from the nanowire structure could further improve halide detection performance. The determination was based on measurement of the well-separated oxidation peak currents of respective silver halides formed on the surface of silver during an anodic potential sweep. The concentration range was linear from 50 μM to 20.2 mM for bromide and iodide and 200 μM to 20.2 mM for chloride, and the sensitivity was 0.059 μA/mM, 0.042 μA/mM and 0.032 μA/mM for chloride, bromide and iodide, respectively. The correlation coefficient was 0.999 in each case. The Ag NWs/Pt electrode offered a useful platform for the development of a highly sensitive halide sensor.

A novel noncovalent approach was developed for the functionalization of multi-wall carbon nanotubes (MWNTs) using the hydrophobin, HFBI. Owing to the amphipathic nature, HFBI can be adopted onto the surface of MWNTs to form HFBI–MWNTs nanocomposite with good dispersion in water. The HFBI–MWNTs nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and water contact angle measurements (WCA). Furthermore, a glucose biosensor was developed based on HFBI–MWNTs by a one-step casting method. The resulting biosensor displayed high sensitivity, wider linear range, low detection limit, and fast response for glucose detection, which implicated that the HFBI–MWNTs nanocomposite film holds great promise in the design of electrochemical devices, such as sensors and biosensors.

A novel amperometric choline biosensor based on the nanocomposite film composed of choline oxidase (ChOx), multi-wall carbon nanotubes (MWCNTs), gold nanoparticles (GNp) and poly(diallyldimethylammonium chloride) (PDDA) was developed for the specific detection of choline. GNp-decorated MWCNTs (MWCNTs–GNp) was synthesized by a classical chemical method, and GNp was attached on MWCNTs through the specific interaction between –SH and Au. The enzyme ChOx would be attached to the MWCNTs–GNp matrix and also be adsorbed electrostatically with PDDA which was employed not only as a dispersant but also a binder material. The microscopic structure and composition of the synthesized MWCNTs–GNp were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX), and properties of the resulting choline biosensors were monitored by electrochemical measurements. Taking the sensitivity and selectivity into consideration, 0.35 V versus Ag/AgCl was selected to detect choline. The resulting biosensor exhibited a wide linear range of 0.001–0.5 mM choline, with a remarkable sensitivity of 12.97 μA/mM, a detection limit of 0.3 μM estimated at a signal-to-noise ratio of 3 and fast response time (within 7 s). Moreover, it showed good reproducibility, anti-interferant ability and long-term stability. This work presented a feasible approach for further research in biosensing and other surface functionalizing.

A novel strategy to fabricate hydrogen peroxide (H2O2) sensor was developed based on multi-wall carbon nanotube/silver nanoparticle nanohybrids (MWCNT/Ag nanohybrids) modified gold electrode. The process to synthesize MWCNT/Ag nanohybrids was facile and efficient. In the presence of carboxyl groups functionalized multi-wall carbon nanotubes (MWCNTs), silver nanoparticles (Ag NPs) were in situ generated from AgNO3 aqueous solution and readily attached to the MWCNTs convex surfaces at room temperature, without any additional reducing reagent or irradiation treatment. The formation of MWCNT/Ag nanohybrids product was observed by transmission electron microscope (TEM), and the electrochemical properties of MWCNT/Ag nanohybrids modified gold electrode were characterized by electrochemical measurements. The results showed that this sensor had a favorable catalytic ability for the reduction of H2O2. The resulted sensor could detect H2O2 in a linear range of 0.05–17 mM with a detection limit of 5 × 10−7 M at a signal-to-noise ratio of 3. The sensitivity was calculated as 1.42 μA/mM at a potential of −0.2 V. Additionally, it exhibited good reproducibility, long-term stability and negligible interference of ascorbic acid (AA), uric acid (UA), and acetaminophen (AP).

A novel glucose biosensor was developed, based on the immobilization of glucose oxidase (GOD) with cross-linking in the matrix of bovine serum albumin (BSA) on a Pt electrode, which was modified with gold nanoparticles decorated Pb nanowires (GNPs-Pb NWs). Pb nanowires (Pb NWs) were synthesized by an l-cysteine-assisted self-assembly route, and then gold nanoparticles (GNPs) were attached onto the nanowire surface through –SH–Au specific interaction. The morphological characterization of GNPs-Pb NWs was examined by transmission electron microscopy (TEM). Cyclic voltammetry and chronoamperometry were used to study and to optimize the electrochemical performance of the resulting biosensor. The synergistic effect of Pb NWs and GNPs made the biosensor exhibit excellent electrocatalytic activity and good response performance to glucose. The effects of pH and applied potential on the amperometric response of the biosensor have been systemically studied. In pH 7.0, the biosensor showed the sensitivity of 135.5 μA mM−1 cm−2, the detection limit of 2 μM (S/N = 3), and the response time <5 s with a linear range of 5–2200 μM. Furthermore, the biosensor exhibits good reproducibility, long-term stability and relative good anti-interference.

Hydrophobins are small fungal proteins which self-assemble on interfaces and significantly change the surface wettability. The self-assembled film of hydrophobin HFBI on a gold surface improved the surface hydrophilicity with water contact angle changing from 73.8 ± 1.8° to 45.3 ± 1.4°. A quartz crystal microbalance (QCM) analysis indicated that the HFBI coverage density on a gold surface was 588 ng cm−2, and the self-assembled film remained stable under different pH values ranging from 1 to 13. A hydrophilic protein such as choline oxidase (ChOx) was then successfully immobilized on the HFBI modified gold surface. To evaluate the bioactivity of immobilized enzyme, an amperometric choline biosensor was constructed based on the Gold/HFBI/ChOx electrode, which produced as large as 4578.27 nA response current by 0.238 μg immobilized ChOx, when saturated by choline substrate. Comparing with our choline biosensors previously reported, the HFBI self-assembled film exhibited excellent capability to preserve the bioactivity of ChOx, hence a great potential in electrochemical biosensing is suggested.

A new strategy for fabricating glucose biosensor was presented by layer-by-layer assembled chitosan (CS)/gold nanoparticles (GNp)/glucose oxidase (GOD) multilayer films modified Pt electrode. First, a cleaned Pt electrode was immersed in poly(allylamine) (PAA), and then transferred to GNp, followed by the adsorption of GOD (GOD/GNp/PAA/Pt). Second, the GOD/GNp/PAA/Pt electrode was immersed in CS, and then transferred to GNp, followed by the adsorption of GOD (GOD/GNp/CS/GOD/GNp/PAA/Pt). Third, different layers of multilayer films modified Pt electrodes were assembled by repeating the second process. Film assembling and characterization were studied by quart crystal microbalance, and properties of the resulting glucose biosensors were measured by electrochemical measurements. The results confirmed that the assembling process of multilayer films was simple to operate, the immobilized GOD displayed an excellent catalytic property to glucose, and GNp in the biosensing interface efficiently improved the electron transfer between analyte and electrode surface. The amperometric response of the biosensors uniformly increased from one to six layers of multilayer films, and then reached saturation after the seven layers. Among the resulting biosensors, the biosensor based on the six layers of multilayer films was best. It showed a wide linear range of 0.5–16 mM, with a detection limit of 7.0 μM estimated at a signal-to-noise ratio of 3, fast response time (within 8 s). Moreover, it exhibited good reproducibility, long-term stability and interference free. This method can be used for constructing other thin films, which is a universal immobilization method for biosensor fabrication.

A novel amperometric glucose biosensor based on the nine layers of multilayer films composed of multi-wall carbon nanotubes (MWCNTs), gold nanoparticles (GNp) and glucose oxidase (GOD) was developed for the specific detection of glucose. MWCNTs were chemically modified with the H2SO4–HNO3 pretreatment to introduce carboxyl groups which were used to interact with the amino groups of poly(allylamine) (PAA) and cysteamine via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide cross-linking reaction, respectively. A cleaned Pt electrode was immersed in PAA, MWCNTs, cysteamine and GNp, respectively, followed by the adsorption of GOD, assembling the one layer of multilayer films on the surface of Pt electrode (GOD/GNp/MWCNTs/Pt electrode). Repeating the above process could assemble different layers of multilayer films on the Pt electrode. PBS washing was applied at the end of each assembly deposition for dissociating the weak adsorption. Film assembling and characterization were studied by transmission electron microscopy and quartz crystal microbalance, and properties of the resulting glucose biosensors were measured by electrochemical measurements. The marked electrocatalytic activity of Pt electrode based on multilayer films toward H2O2 produced during GOD enzymatic reactions with glucose permitted effective low-potential amperometric measurement of glucose. Taking the sensitivity and selectivity into consideration, the applied potential of 0.35 V versus Ag/AgCl was chosen for the oxidation detection of H2O2 in this work. Among the resulting glucose biosensors, the biosensor based on nine layers of multilayer films was best. It showed a wide linear range of 0.1–10 mM glucose, with a remarkable sensitivity of 2.527 μA/mM, a detection limit of 6.7 μM estimated at a signal-to-noise ratio of 3 and fast response time (within 7 s). Moreover, it exhibited good reproducibility, long-term stability and the negligible interferences of ascorbic acid, uric acid and acetaminophen. The study can provide a feasible approach on developing new kinds of oxidase-based amperometric biosensors, and can be used as an illustration for constructing various hybrid structures.

A novel amperometric choline biosensor has been fabricated with choline oxidase (ChOx) immobilized by the sol-gel method on the surface of multi-walled carbon nanotubes (MWCNT) modified platinum electrode to improve the sensitivity and the anti-interferential property of the sensor. By analyzing the electrocatalytic activity of the modified electrode by MWCNT, it was found that MWCNT could not only improve the current response to H2O2 but also decrease the electrocatalytic potential. The effects of experimental variables such as the buffer solutions, pH and the amount of loading enzyme were investigated for the optimum analytical performance. This sensor shows sensitive determination of choline with a linear range from 5.0 × 10−6 to 1.0 × 10−4 mol/L when the operating pH and potential are 7.2 and 0.15 V, respectively. The detection limit of choline was 5.0 × 10−7 mol/L. Selectivity for choline was 9.48 μA·(mmol/L)−1. The biosensor exhibits excellent anti-interferential property and good stability, retaining 85% of its original current value even after a month. It has been applied to the determination of choline in human serum.

A novel method for real time kinetic analysis of the interaction between IL-1α and sIL-1R I is reported. sIL-1R I was immobilized on the biotin cuvette surface of the resonant mirror biosensor to set up the experimental model. Results obtained from the assay confirmed that biotinylated sIL-1R I was specifically immobilized on the avidin-coated biotin cuvette surface, the interaction between IL-1α and sIL-1R I was fast and specific, and the interaction response is dose-dependence of IL-1α in solution with a range of 150–2400 nM. The binding curve was fitted by FASTfit analysis, which fitted the monophasic association quite well, and the error did not exceed 0.4 arc seconds. Kinetic constants for IL-1α binding to sIL-1R I were determined from the plots of Kon versus the concentration of IL-1α. For the interaction, kass was 2.81 × 103 M−1 s−1, Kdiss was 2.52 × 10−3 s−1, and KD was 8.97 × 10−7 M.

Paeoniae radix 801 is one of the active ingredients of the blood-activating and stasis-eliminating traditional Chinese medicine (TCM). In order to find out its action mechanism, an interaction assay system (IAsys) biosensor and a quartz crystal microbalance (QCM) were employed for the study on the specific interaction between P. radix 801 and endothelin-1 (ET-1). In the experiments, ET-1 was immobilized on the surfaces of the IAsys biosensor cuvettes and the QCM substrates by surface modification techniques, and then P. radix 801 was added to the cuvette and the substrate, separately. Then, the binding and interaction process between P. radix 801 and ET-1 was monitored. The results showed that P. radix 801 bound ET-1 specifically and the average binding masses were 1.28 ng mm−2 on the IAsys biosensor and 135 ng cm−2 (=1.35 ng mm−2) on the QCM sensor, respectively. Therefore, P. radix 801 generates bioactivity by binding and restraining the activity of ET-1. Both the IAsys biosensor and the QCM measurement techniques had high reproducibility and reliability and were found to be reliable tools to study the interaction of P. radix 801 and ET-1. This finding offers a new and effective way to study the action mechanism of P. radix 801.

An amperometric choline biosensor was developed by immobilizing choline oxidase (ChOx) in a layer-by-layer (LBL) multilayer film on a platinum (Pt) electrode modified with Prussian blue (PB). 6-O-Ethoxytrimethylammoniochitosan chloride (EACC) was used to prepare the ChOx LBL films. The choline biosensor was used at 0.0 V versus Ag/AgCl to detect choline and exhibited good characteristics such as relative low detection limit (5 × 10−7 M), short response time (within 10 s), high sensitivity (88.6 μA mM−1 cm−2) and a good selectivity. The results were explained based on the ultrathin nature of the LBL films and the low operating potential that could be due to the efficient catalytic reduction of H2O2 by PB. In addition, the effects of pH, temperature and applied potential on the amperometric response of choline biosensor were evaluated. The apparent Michaelis–Menten constant was found to be (0.083 ± 0.001) ×10−3 M. The biosensor showed excellent long-term storage stability, which originates from a strong adsorption of ChOx in the EACC multilayer film. When the present choline biosensor was applied to the analysis of phosphatidylcholine in serum samples, the measurement values agreed satisfactorily with those by a hospital method.

A layer-by-layer deposition technique was employed for fabricating choline sensors with different polycations. We used two kinds of choline oxidase (ChOx)/polycation thin films to modify platinum (Pt) electrodes, each having the same enzyme (ChOx) but with different polycations, poly(ethyleneimine) (PEI) and poly(diallyldimethylammonium chloride) (PDDA). The Pt electrodes coated with a ChOx/PEI or ChOx/PDDA thin film were used successfully as choline sensors. The ChOx/PEI film-modified sensor showed a higher response, wider dynamic range and shorter response time than those of the ChOx/PDDA film-based sensor. The results were rationalized based on the different permeability of the thin films due to the different structure of the polycationic materials. The assembly processes of the thin films were monitored by quartz crystal microbalance (QCM) measurements.

A facile and effective approach to prepare glucose biosensor was developed based on chitosan-reduced graphene oxide-Au nanoparticles (CS-RGO-AuNPs) hybrids modified Pt electrode. Here CS which has many amino groups along its macromolecular chains and possesses good hydrophilic capability was used as reductant and stabilizer to transform GO into RGO. And one-pot warm bath method was employed to fabricate CS-RGO-AuNPs hybrids. The nanocomposites provided a good micro-bioenvironment for glucose oxidase (GOD) to facilitate electrocatalysis of glucose. The resulting biosensor exhibited a wide linear range of 15 μM to 2.13 mM, with a remarkable sensitivity of 102.4 μA mM−1 cm−2, a detection limit of 1.7 μm estimated at a signal-to-noise ratio of 3 and fast response time (within 5 s). Moreover, it showed good reproducibility, anti-interference ability and long-term stability. It showed that as-prepared CS-RGO-AuNPs nanohybrids not only exhibit efficiency for enzyme immobilization but also are of great importance for amplifying the sensor response. So the current work could provide a feasible approach and potential platform to fabricate a variety of enzymatic amperometric sensors.

A novel amperometric choline biosensor based on the nanocomposite film composed of choline oxidase (ChOx), multi-wall carbon nanotubes (MWCNTs), gold nanoparticles (GNp) and poly(diallyldimethylammonium chloride) (PDDA) was developed for the specific detection of choline. GNp-decorated MWCNTs (MWCNTs–GNp) was synthesized by a classical chemical method, and GNp was attached on MWCNTs through the specific interaction between –SH and Au. The enzyme ChOx would be attached to the MWCNTs–GNp matrix and also be adsorbed electrostatically with PDDA which was employed not only as a dispersant but also a binder material. The microscopic structure and composition of the synthesized MWCNTs–GNp were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX), and properties of the resulting choline biosensors were monitored by electrochemical measurements. Taking the sensitivity and selectivity into consideration, 0.35 V versus Ag/AgCl was selected to detect choline. The resulting biosensor exhibited a wide linear range of 0.001–0.5 mM choline, with a remarkable sensitivity of 12.97 μA/mM, a detection limit of 0.3 μM estimated at a signal-to-noise ratio of 3 and fast response time (within 7 s). Moreover, it showed good reproducibility, anti-interferant ability and long-term stability. This work presented a feasible approach for further research in biosensing and other surface functionalizing.

•A facial DNA biosensor was developed for mercury ions determination.•The biosensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy.•The as-prepared biosensor exhibits excellent selectivity and superior sensitivity.•The as-prepared biosensor could be applied to determinate of water sample.The present work describes an effective strategy to fabricate a highly sensitive and selective DNA-biosensor for the determination of mercury ions (Hg2 +). The DNA 1 was modified onto the surface of Au electrode by the interaction between sulfydryl group and Au electrode. DNA probe is complementary with DNA 1. In the presence of Hg2 +, the electrochemical signal increases owing to that Hg2 +-mediated thymine bases induce the conformation of DNA probe to change from line to hairpin and less DNA probes adsorb into DNA 1. Taking advantage of its reduction property, methylene blue is considered as the signal indicating molecule. For improving the sensitivity of the biosensor, Au nanoparticles (Au NPs) modified reporter DNA 3 is used to adsorb DNA 1. Electrochemical behaviors of the biosensor were evaluated by electrochemical impedance spectroscopy and cyclic voltammetry. Several important parameters which could affect the property of the biosensor were studied and optimized. Under the optimal conditions, the biosensor exhibits wide linear range, high sensitivity and low detection limit. Besides, it displays superior selectivity and excellent stability. The biosensor was also applied for water sample detection with satisfactory result. The novel strategy of fabricating biosensor provides a potential platform for fabricating a variety of metal ions biosensors.