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The development of flexible substrate materials and nanomaterials with high electrochemical performance is of great significance for constructing efficient wearable electrochemical sensors for real-time health monitoring. Herein, a wearable electrochemical sweat sensor based on a Ni–Co MOF nanosheet coated Au/polydimethylsiloxane (PDMS) film was prepared for continuous monitoring of the glucose level in sweat with high sensitivity. First, a stretchable Au/PDMS film based three-electrode system was prepared by chemical deposition of a gold layer on the hydrophilic treated PDMS. Then, Ni–Co MOF nanosheets with high electrocatalytic activity were synthesized by a facile solvothermal method and modified on the Au/PDMS electrode. The electrocatalytic activity of the Ni–Co MOF nanosheets synthesized under different Ni : Co ratios was investigated. The Ni–Co MOF/Au/PDMS (NCAP) film electrode showed excellent electrochemical performance for glucose detection with a wide linear range of 20 μM to 790 μM and a high sensitivity of 205.1 μA mM−1 cm−2. In addition, the flexible sensor shows high stability and a good electrochemical response to glucose when stretched and bent to different levels. Moreover, it maintained long-term stability and high selectivity for glucose monitoring. Lastly, a sweat-absorbent cloth was used to cover the working area of the sensor and was fixed with a needle and thread to form a wearable sweat glucose sensor. The sensor can be attached to the skin for stable, accurate and continuous monitoring of glucose levels in human sweat for one day. This work validates the potential of our high-performance wearable sensor for out-of-clinic health monitoring. [ABSTRACT FROM AUTHOR]

A covalent organic framework (COF) is a promising type of porous material with customizable surface characteristics. Confining multiple catalytic units within a mesoporous COF can generate abundant active sites and improve the catalytic performance. In this work, a COF with both metalloporphyrin and a metal nanoparticle complex denoted as hemin/TAPB-DMTP-COF/AuNPs (TAPB: 1,3,5-tris(4-amino-phenyl)benzene, DMTP: 2,5-dimethoxyterephaldehyde, AuNPs: Au nanoparticles) has been successfully fabricated through a hierarchical encapsulation method. The as-synthesized composite was then employed to construct an electrochemical sensing platform for the efficient detection of bisphenol A (BPA). Under the optimal conditions, the hemin/TAPB-DMTP-COF/AuNP sensor presented a linear range of 0.01–3 μmol L−1 and a low detection limit of 3.5 nmol L−1. The satisfactory signal amplification is based on a triple-signaling amplification strategy due to the abundant Fe3+ sites of Fe-porphyrin, high conductivity of AuNPs and a large specific surface area of the TAPB-DMTP-COF. The proposed method was used to measure the content of BPA in different water samples with a satisfactory recovery from 95.5 to 104.0%, suggesting the great potential of the sensor in practical applications. [ABSTRACT FROM AUTHOR]

In this research, a novel manganese dioxide nanorod-anchored graphene oxide (MnO2 NRs/GO) composite was synthesized by a simple hydrothermal method for electrochemical sensing application. A highly sensitive electrochemical sensor for dopamine (DA) was constructed by modifying glassy carbon electrode (GCE) with MnO2 NRs/GO. The morphology and performance of the composite material and modified GCEs were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV), respectively. The resultant MnO2 NRs/GO composite has a large electroactive area and shows excellent electrochemical activity toward DA. Under the optimal conditions, the DA sensor shows a linear response in the DA concentration ranges of 0.1 μM–0.08 mM and 0.08–0.41 mM with a low detection limit of 0.027 μM and a high sensitivity of 602.4 μA·mM−1·cm−2. The MnO2 NRs/GO composite provides a promising platform for the construction of a highly sensitive and selective sensor of DA. [ABSTRACT FROM AUTHOR]

The fabrication of chemically stable metal–organic frameworks for electrochemical sensors is essential to broaden their applications. In this study, the integration of a Zr-based metal–organic framework (UiO-66-NH2) with multi-walled carbon nanotubes (MWCNTs) was achieved by a one-pot solvothermal reaction. This composite was then characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and contact angle measurements. The porous structure and unreacted amine groups provided by UiO-66-NH2 frameworks accompanied by the excellent conductivity of MWCNTs have made this composite an ideal electrode material for lead detection. After the optimization of MWCNT content and the detection conditions, the oxidation peak currents were proportional to lead concentrations in the range of 0.001–0.8 μmol L−1 with a low detection limit of 0.5 nmol L−1 (S/N = 3). More importantly, the well-preserved crystallinity of MWCNTs@UiO-66-NH2 after 80 cycles and after being soaked in different pH aqueous solutions indicates the promising application of this sensor for real samples. Satisfactory recoveries were achieved when this sensor was used to detect lead in real samples. Furthermore, the excellent stability of this composite makes it possible to be employed in other fields, including extreme acidic media. [ABSTRACT FROM AUTHOR]

Urchin-like InS nanostructures were functionalized with multi-walled carbon nanotubes (MWCNTs) and deposited on a glassy carbon electrode (GCE) to obtain a new kind of sensor for dopamine (DA). The new electrode was characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, cyclic voltammetry and differential pulse voltammetry. It is found that the current response toward DA is significantly enhanced compared to that of a bare GCE or a GCE modified with MWCNTs. The peak separation between DA and ascorbic acid (AA) is up to 225 mV. The new electrode also has improved selectivity for DA over AA compared to the bare electrode. The new DA sensor has a wide linear range (0.5-300 μM), high sensitivity (594.9 μA mM cm) and low detection limit (0.1 μM). CNTs wrapped on urchin-like nanostructures remarkable improve its electrocatalytic activity and thus provide a promising strategy to develop excellent composite materials for electrochemical sensing. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Non-invasive wearable sweat glucose sensors are expected to be highly desirable for personalized diabetes management. Therefore, developing facile, convenient, and scalable manufacturing method of such wearable sensors is urgently needed. Herein, we report a simple and low-cost stamping-vacuum filtration dry transfer (SVFDT) method for construction of a wearable sweat glucose electrochemical sensor. In this patch, a three-electrode array template was made by using a polyvinyl chloride (PVC) stamp, followed by the preparation of multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) (MP) film electrode using the vacuum-filtration dry transfer method. In addition, for further enhancing the conductivity of the electrode, another similar stamp with a raised surface dipping carbon nanotubes (CNTs) conductive coating was stamped on the surface of the MP electrode to obtain CNTs/MWCNTs/PDMS (CMP) electrode. CMP electrode was modified with the enzyme-like Ni-Co metal-organic framework (MOF) material which showed good electro-catalytic activity and achieved high sensitivity for glucose detection with a low detection limit of 6.78 μM and a wide linear range of 20 μM - 1.1 mM. More importantly, the Ni-Co MOF modified CMP (NCMP) electrode also displayed high stability under stretching and bending conditions. Finally, the sweat absorbent cloth was combined with the NCMP film electrode to form a wearable flexible electrochemical sensor patch, which could adhere to the skin to enrich sweat and realize real-time detection of sweat glucose with high accuracy. This SVFDT method can also be applied to the fabrication of other electronic devices. [Display omitted] • A wearable sweat glucose electrochemical sensor based on bimetallic MOF. • SVFDT method was used for prepare CMP film electrode. • NCMP film based sensor showed high performance for glucose detection. • An NCMP film based on-body sensor for real-time monitoring of sweat glucose. [ABSTRACT FROM AUTHOR]

Highlights • A hierarchically Cu-BTC MOF based electrochemical sensor was firstly constructed for non-electroactive pesticide detection. • This MOF based sensor possesses wide detection range and low detection limit. • The sensor displays good reproducibility and stability, exhibiting good performance in real sample detection. Abstract An electrochemical sensor based on hierarchically Cu-BTC MOF material for non-electroactive glyphosate detection has been firstly constructed in this report. By using Cu-BTC frameworks as a detection matrix, the large specific surface area of the material can increase the electrode reaction site and further improve the detection performance. The electrochemical behavior of Cu-BTC frameworks for glyphosate detection was evaluated by cyclic voltammetry (CV). Under optimum conditions, differential pulse stripping voltammetry (DPV) is employed to detect glyphosate. The results show that the fabricated sensor displays ultralow detection limit (1.4 × 10−13 mol L-1) and wide detection range (1.0 × 10-12 to 1.0 × 10-9 mol L-1 and 1.0 × 10-9 to 1.0 × 10-5 mol L-1). Besides, this sensor possesses acceptable reproducibility and stability, as well as good selectivity against the major metabolite of glyphosate aminomethylphosphonic acid (AMPA) and other interference. Furthermore, this electrochemical sensor can also be applied to the detection of glyphosate in soybean. It is worth mentioning that this effectively Cu-BTC based sensor has great potential application in favorable and selective detection of organophosphorus pesticides in actual samples. [ABSTRACT FROM AUTHOR]

Graphical abstract TAPB-DMTP-COFs/AuNPs composites were synthesized and investigated as a novel electrochemical probe for chlorogenic acid detection. Highlights • COFs/AuNPs composites were synthesized using a solution infiltration method. • Results exhibited high sensitivity and good stability to chlorogenic acid detection. • Satisfactory results were achieved in real samples. • This research expands the applications of COFs based composites in biosensor. Abstract In this work, novel gold nanoparticles-doped TAPB-DMTP-COFs (TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde; COFs, covalent organic frameworks) composite was successfully prepared via COFs as the host matrix to support the growth of gold nanoparticles. With the strong electrostatic interaction between gold nanoparticles and unsaturated amine group present on TAPB-DMTP-COFs, the gold nanoparticles were successfully immobilized onto the surface of TAPB-DMTP-COFs under vigorously stirring. Then, this novel composite was used to constitute an advanced electrochemical sensor and presented a good electrocatalytic activity toward the oxidation of chlorogenic acid (CGA) in the phosphate buffer solution (pH 7.0). After a series of experiments, this electrochemical sensor displays a wide linear range of 1.0 × 10−8 – 4.0 × 10−5 mol L−1, low detection limit of 9.5 × 10−9 mol L−1 as well as a good repeatability of 4.1% in 2.0 × 10−5 mol L−1 CGA after ten scanning rounds. Moreover, the sensor exhibits an excellent stability and maintains its catalytic activity at least 100 cycles. Our work not only provides a simple way to detect CGA quantitatively in real samples, but paves a new platform for COFs-based composite in biosensor. [ABSTRACT FROM AUTHOR]

Here, a new porous graphene (PGR) based nanocomposite was synthesized by a chemical and thermal reduction of graphite oxide in the assistance of calcium lignosulfonate (CLS), and characterized by scanning electron microscopy SEM, TEM, XPS, Zeta potential analysis, FTIR and EIS. Then the as-prepared CLS/PGR was used along with Nafion to modify a glassy carbon electrode (GCE) for constructing electrochemical sensor to detect Pb 2+ and Cd 2+ simultaneously. Compared with the bare GCE, the reduced graphene oxide/GCE, and the CLS/PGR/GCE, the Nafion/CLS/PGR/GCE exhibited improved electrochemical performance in detecting the two ions. It could be ascribed to the synergistic contribution from PGR, CLS and Nafion, which integrated the advantageous features of high active surface area, good cation exchange ability and strong adsorption capacity. Under optimum conditions, this novel sensor showed a wide detection range for Pb 2+ and Cd 2+ (0.05–5.0 μM) with the limit of detection and limit of quantification for Pb 2+ 0.01 and 0.03 μM, for Cd 2+ 0.003 and 0.01 μM, respectively. It was successfully applied for the simultaneous determination of Pb 2+ and Cd 2+ in real water samples with satisfying recoveries of 93.6–105.3% for Pb 2+ and 93.5–102.5% for Cd 2+ , demonstrating its feasibility for the determination of environmental metallic pollutants. [ABSTRACT FROM AUTHOR]

This work developed a novel sulfate biosensor based on arylsulfatase (AS) inhibition. AS mixed with glutaraldehyde and bovine serum albumin was immobilized on glassy carbon electrode (GCE), which was first modified with poly- l -lysine (PLL)/graphene (GR) hybrid and electrodeposited gold nanoparticles (AuNPs). The characterizations were performed by TEM, SEM, FTIR, Raman spectroscopy and cyclic voltammetry. AS can catalyze 4-nitrocatechol sulfate (NCS) to hydrolyze to sulfate and 4-nitrocatcchol (NC), which is electroactive and an anodic current occurs at ∼0.42 V vs. SCE. However, the production of NC would decrease in the presence of sulfate due to its inhibition effect on the enzymatic hydrolysis reaction, thus leading to a decrease in the oxidation current. The inhibition measurements were carried out by detecting this current decrease after adding sulfate. At optimal conditions, the inhibition rate was linear to −log [sulfate] in the concentration range from 1.0 × 10 −7 to 1.0 × 10 −5 M with the detection limit of 4.0 × 10 −8 M. The introduced biosensor was further applied to assay the sulfate constituent in PM 2.5 , and the results were verified by employing ion chromatography as a reference. It showed that the new biosensor has a promising application for sulfate detection in real samples. [ABSTRACT FROM AUTHOR]

In this work, SrTiO 3 nanoparticles (SrTiO 3 NPs), a novel and effective perovskite-type material, are synthesized to modify electrode for the development of sensitive enzymatic electrochemical biosensor applications. The electrochemical behavior of glucose oxidase (GOx) immobilized on SrTiO 3 NPs-modified glassy carbon electrode is investigated. Scanning electron microscopy and cyclic voltammetry are used to characterize the morphology and assay property of different modified electrodes. Results illustrate that SrTiO 3 NPs possess large surface area and apparently enhance the direct electron transfer between GOx and modified electrode. The SrTiO 3 NPs-based enzyme biosensor shows a high sensitivity of 15.6 mA·M − 1 ·cm − 2 , wide linear range from 0.01 mM to 1.2 mM, and a low detection limit of 3 μM (S/N = 3). Furthermore, the resultant glucose biosensor has excellent selectivity, acceptable repeatability, practicality and stability. The perovskite SrTiO 3 NPs provide a very attractive and potential electrode material to develop electrochemical biosensors. [ABSTRACT FROM AUTHOR]

Using a facile and efficient method, two-dimensional (2D) ultra-thin MnO 2 nanosheets were successfully prepared. Due to the large specific surface area and mesoporous structure, MnO 2 nanosheet is a good candidate for use as an enhanced electrochemical sensing material. MnO 2 nanosheets were immobilized onto glassy carbon electrodes with Nafion film to construct a H 2 O 2 electrochemical nonenzymatic sensor. Amperometric study showed MnO 2 nanosheets exhibited very high electrocatalytic activity towards H 2 O 2 reduction. A very low detection limit (5 nM) was reached with a wide linear range (25 nM–2 μM and 10–454 μM) and a high sensitivity of 3261 mA M −1 cm −2 . The fabricated H 2 O 2 sensor also exhibited excellent selectivity, good reproducibility and long-time stability. Furthermore, the constructed high sensitive sensor was successfully applied to perform real-time monitoring trace concentration of H 2 O 2 released by SP2/0 cells, indicating that MnO 2 nanosheets provide a new platform for developing high performance electrochemical sensors in biological applications. [ABSTRACT FROM AUTHOR]

An electrochemical sensor based on multi-walled carbon nanotubes and chitosan-nickel complex (MWCNTs/CTS-Ni) was fabricated by self-assembly technique for sensitive determination of metronidazole. The electroanalytical performance of the proposed MWCNTs/CTS-Ni modified electrode was intensively evaluated. The experimental results indicated that the MWCNTs/CTS-Ni modified glassy carbon electrode exhibited excellent electrocatalytic activity towards metronidazole. The proposed sensor revealed linear response to metronidazole in the concentration range of 0.1 to 150 μmol L − 1 , with a low detection limit of 0.025 μmol L − 1 . Moreover, the sensor also showed good selectivity, reproducibility and stability. The proposed method could be successfully applied for the sensitive determination of metronidazole in pharmaceutical and biological samples. [ABSTRACT FROM AUTHOR]

A novel hydrogen peroxide (H 2 O 2 ) nonenzymatic electrochemical sensor was constructed based on CoSn(OH) 6 nanocubes (NC). The CoSn(OH) 6 nanocubes with uniform size distribution were prepared by a co-precipitation method at room temperature. Then CoSn(OH) 6 NC solubilized in Nafion was immobilized on glassy carbon electrode (GCE) by the physical adsorption to determination of H 2 O 2 . The detection limit has been estimated to be 1 μM with a wide linear range from 4 to 400 μM. The as-made sensor also exhibited excellent selectivity and super stability. In addition, the sensor can be successfully applied to detect the H 2 O 2 levels in human serum samples with satisfactory results. The high electrocatalytic activity of CoSn(OH) 6 NC may be owing to the large surface area and uneven surface structure. We believe these cube-like CoSn(OH) 6 nanocrystals provide a promising platform for developing nonenzymatic H 2 O 2 sensors in biological applications. [ABSTRACT FROM AUTHOR]

In this work, an efficient and universal streptavidin-functionalized nitrogen-doped graphene (NG) was for the first time proposed and used to develop a highly sensitive electrochemical immunosensor for the detection of tumor markers. Transmission electron microscopy, electrochemical impedance spectrum, static water contact measurement, and cyclic voltammetry were used to characterize the streptavidin-functionalized NG platform and immunosensor. The biofunctionalized NG showed excellent hydrophilicity, larger specific surface area, and high electrochemical activity. These properties of the platform enhanced the loading capacity of proteins, and retained the bioactivity of the immobilized proteins, and thus remarkably improved the sensitivity of the immunosensor. Using carcinoembryonic antigen (CEA) as model analyte, the proposed immunosensor demonstrated a wide linear range of 0.02–12 ng mL −1 with a low detection limit of 0.01 ng mL −1 . The CEA immunosensor could be applied to detect human serum samples with satisfactory results. The streptavidin-functionalized NG material provided an universal and promising platform for the electrochemical immunosensing applications. [ABSTRACT FROM AUTHOR]

An electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan–copper complex (MWCNTs/CTS–Cu) was fabricated by self-assembly technique. The MWCNTs/CTS–Cu modified GCE showed an excellent electrocatalytic activity for the oxidation of paracetamol, and accelerated electron transfer between the electrode and paracetamol. Under optimal experimental conditions, the differential pulse peak current was linear with the concentration of paracetamol in the range of 0.1–200 μmol L −1 with a detection limit of 0.024 μmol L −1 . The sensitivity was found to be 0.603 A/mol L −1 . The proposed sensor also showed a high selectivity for paracetamol in the presence of ascorbic acid and dopamine. Moreover, the proposed electrode revealed good reproducibility and stability. The proposed method was successfully applied for the determination of paracetamol in tablet and human serum samples. [ABSTRACT FROM AUTHOR]

The accurate measurement of nitrate in PM 2.5 is essential for a complete understanding of the effects of aerosols on human health, the impact of aerosols on the radiative balance of the earth and the role of aerosols in visibility problems. In this paper, we present a novel, quick, easy, cheap and eco-friendly electroanalytical procedure for the determination of nitrate in PM 2.5 samples using a carbon-fiber micro-disk electrode (CFMDE) coupled with square-wave voltammetry (SWV). Under optimal experimental conditions the nitrate SWV response increases linearly with nitrate concentration over a range of 0.003–2.0 mmol L −1 , and the detection limit is 1.10 μmol L −1 ( S / N =3). Nitrate contents in daily PM 2.5 of Yangzhou in China were detected successfully by employing this novel method, and the results were compared well with those obtained by using ion chromatography. Then, we detected nitrate in two-hour PM 2.5 filter samples via the standard addition method, and the concentrations were applied in an analysis of the daily change of nitrate contained in PM 2.5 of Yangzhou. The research in this work indicates that the electrochemical method opens a new opportunity for fast, portable, and sensitive analysis of components in PM 2.5 . [ABSTRACT FROM AUTHOR]

The flexible electrochemical sensor is a key component of the health monitoring system which can continuously track the physiological signals of the human body, while there is no obvious discomfort and invasiveness. Therefore, it has great potential in personalized medical testing. However, the development of flexible electrochemical sensors currently faces many difficulties, such as the limitations of conductive material properties and manufacturing methods, and the disadvantages of commonly used flexible substrates that are not resistant to high temperatures. In this work, inorganic nanomaterials commonly used to make flexible electrochemical sensors were classified to zero-dimensional (0D) nanomaterials, one-dimensional (1D) nanomaterials, two-dimensional (2D) nanomaterials, and hybrid nanomaterials according to their morphology. The fabrication method of the nanomaterials-based flexible electrochemical sensors was also introduced. Furthermore, the application of flexible electrochemical sensors for chemical and biological sensing and their detection performance were summarized. The detection targets were classified to ion, small molecule, biomacromolecule, and bacteria, respectively. [Display omitted] • The flexible electrochemical sensor can replace the bulky and expensive analytical instruments used in the medical field. • Inorganic functional nanomaterials that commonly used to make flexible electrochemical sensors was introduced. • Inorganic functional nanomaterials were classified to 0D, 1D, 2D and hybrid nanomaterials. • The fabrication method of the nanomaterials-based flexible electrochemical sensors was also introduced. • The application of flexible electrochemical sensors for chemical and biological sensing was summarized. [ABSTRACT FROM AUTHOR]

In this work, we reported an efficient platinum nanoparticles functionalized nitrogen doped graphene (PtNPs@NG) nanocomposite for devising novel electrochemical glucose biosensor for the first time. The fabricated PtNPs@NG and biosensor were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, UV–vis spectroscopy, electrochemical impedance spectra and cyclic voltammetry, respectively. PtNPs@NG showed large surface area and excellent biocompatibility, and enhanced the direct electron transfer between enzyme molecules and electrode surface. The glucose oxidase (GOx) immobilized on PtNPs@NG nanocomposite retained its bioactivity, and exhibited a surface controlled, quasi-reversible and fast electron transfer process. The constructed glucose biosensor showed wide linear range from 0.005 to 1.1 mM with high sensitivity of 20.31 mA M −1 cm −2 . The detection limit was calculated to be 0.002 mM at signal-to-noise of 3, which showed 20-fold decrease in comparison with single NG-based electrochemical biosensor for glucose. The proposed glucose biosensor also demonstrated excellent selectivity, good reproducibility, acceptable stability, and could be successfully applied in the detection of glucose in serum samples at the applied potential of −0.33 V. This research provided a promising biosensing platform for the development of excellent electrochemical biosensors. [ABSTRACT FROM AUTHOR]

Bovine interferon gamma (BoIFN-γ) released by T cells plays very important roles in early diagnosis of Mycobacterium tuberculosis (MTB) infections and control of bovine tuberculosis. In this work, a label-free electrochemical impedance immunosensor is for the first time developed for highly sensitive determination of BoIFN-γ. Cylinder-shaped TiO 2 nanorods are synthesized by a facile hydrothermal method, and show high surface area and good hydrophicility. The immunosensor is fabricated by the immobilization of BoIFN-γ monoclonal antibody on the TiO 2 nanorods modified glassy carbon electrode. The prepared TiO 2 and immunosensor are characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, contact angle measurement, cyclic voltammetry, and electrochemical impedance spectra. The BoIFN-γ concentration is measured through the relative increase of impedance values in corresponding specific binding of BoIFN-γ antigen and BoIFN-γ antibody. The relative increased impedance values are proportional to the logarithmic value of BoIFN-γ concentrations in a wide range of 0.0001 to 0.1 ng/mL with a low detection limit of 0.1 pg/mL. The developed BoIFN-γ immunosensor shows a 249-fold decrease in detection limit in comparison with current enzyme-linked immunosorbent assay. This study provides a new, simple, and highly sensitive approach for very potential application in early diagnosis of MTB infections and control of bovine tuberculosis. [ABSTRACT FROM AUTHOR]

Highlights: [•] The first example of sensor construction based on NH2-MIL-125. [•] Photo-oxidization ability of NH2-MIL-125. [•] Mn2+ detection based on photooxidation and electrochemistry. [•] The method has low detection limit and wide linearity. [Copyright &y& Elsevier]

A tetragonal columnar-shaped TiO2 (TCS-TiO2) nanorods are synthesized via a facile route for the immobilization of glucose oxidase (GOx). A novel electrochemical glucose biosensor is constructed based on the direct electrochemistry of GOx at TCS-TiO2 modified glassy carbon electrode. The fabricated biosensor is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, electrochemical impedance spectra and cyclic voltammetry. The immobilized enzyme molecules on TCS-TiO2 nanorods retain its native structure and bioactivity and show a surface controlled, quasi-reversible and fast electron transfer process. The TCS-TiO2 nanorods have large surface area and provide a favorable microenvironment for enhancing the electron transfer between enzyme and electrode surface. The constructed glucose biosensor shows wide linear range from 5.0×10−6 to 1.32×10−3 M with a high sensitivity of 23.2mAM−1 cm−2. The detection limit is calculated to be 2.0×10−6 M at signal-to-noise of 3. The proposed glucose biosensor also exhibits excellent selectivity, good reproducibility, and acceptable operational stability. Furthermore, the biosensor can be successfully applied in the detection of glucose in serum sample at the applied potential of −0.50V. The TCS-TiO2 nanorods provide an efficient and promising platform for the immobilization of proteins and development of excellent biosensors. [ABSTRACT FROM AUTHOR]

Abstract: An electrochemical sensor based on a copolymer poly(4-vinylpyridine)-co-poly(acrylonitrile), P4VP-co-PAN, and Fe2O3 nanoparticle film modified glassy carbon electrode was developed for the determination of glucose. We studied the response of glucose with the proposed electrode, and determined the optimum conditions by changing the potential, pH and P4VP-co-PAN. The current response measurements were performed in PBS (c=0.1M) with a potential of 0.7V. The current response of this glucose sensor showed a linear relationship with the concentration in the range of 2.5μM–0.58mM (r=0.997). The experimental results demonstrate that this method has such merits as simple operation, low cost, high sensitivity, long term stability and good reproducibility, with satisfactory results. [Copyright &y& Elsevier]

A novel glucose electrochemical biosensor was constructed based on the immobilization of glucose oxidase (GOx) in cage-like PbS nanostructure. The fabricated biosensor was characterized by scanning electron microscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry, respectively. The direct electrochemistry of GOx at cage-like PbS nanostructure modified glassy carbon electrode was for the first time studied. The cage-like PbS nanostructure has larger surface area and provides a favorable microenvironment for facilitating the direct electron transfer between enzyme and electrode surface. The immobilized enzymes on PbS cage-like nanostructure retains its native structure and bioactivity and shows a surface controlled, reversible two-proton and two-electron transfer reaction with a apparent electron transfer rate constant of 2.85s−1. The biosensor shows wide linear range for glucose from 5.0×10−5 M to 1.45×10−3 M with high sensitivity of 11.02mAM−1 cm−2. The detection limit was calculated to be 1.0×10−5 M at signal-to-noise of 3. Moreover, the proposed glucose biosensor displays excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied in the detection of glucose in serum sample. The cage-like PbS nanostructure provides a promising approach for immobilizing proteins and fabricating excellent biosensors. [ABSTRACT FROM AUTHOR]

Abstract: A novel visible light sensitized photoelectrochemical sensing platform was constructed based on the perylene-3,4,9,10-tetracarboxylic acid/titanium dioxide (PTCA/TiO2) heterojunction as the photoelectric beacon. PTCA was synthesized via facile steps of hydrolysis and neutralization reaction, and then the PTCA/TiO2 heterojunction was easily prepared by coating PTCA on nano-TiO2 surface. The resulting photoelectric beacon was characterized by transmission electron microscope, scanning electron microscopy, X-ray diffractometry, FTIR spectroscopy, and ultraviolet and visible spectrophotometer. Using parathion-methyl as a model, after a simple hydrolyzation process, p-nitrophenol as the hydrolysate of parathion-methyl could be obtained, the fabricated derivative photoelectrochemical sensor showed good performances with a rapid response, instrument simple and portable, low detection limit (0.08nmolL−1) at a signal-to-noise ratio of 3, and good selectivity against other pesticides and possible interferences. It had been successfully applied to the detection of parathion-methyl in green vegetables and the results agreed well with that by GC–MS. This strategy not only extends the application of PTCA, but also presents a simple, economic and novel methodology for photoelectrochemical sensing. [Copyright &y& Elsevier]

Abstract: Metal–organic framework (MOF) is a relatively new group of interesting materials for specific electrochemical sensing because of its electrocatalytic activity and large surface area. Here, a Zn4O(BDC)3 (MOF-5; BDC2− =1,4-benzenedicarboxylate) modified carbon paste electrode for lead detection was developed. The electroanalytical procedure comprised two steps: chemical accumulation of the adsorbed metal ions at the modified electrode surface, followed by electrochemical detection of the pre-concentrated species using differential pulse stripping voltammetry. It was found that the MOF-5 was capable of adsorbing lead ions from aqueous solutions and could determine the ions prominently at optimum experimental conditions. Many important parameters to acquire the best electrochemical response were carried out, including the amount of MOF-5, different electrolyte solutions, pH, deposition potential, deposition time, and interferences due to other ions. Finally, a calibration graph was obtained with a linear range from 1.0×10−8 to 1.0×10−6 molL−1 (R 2 =0.9981) and detection limit was found to be 4.9×10−9 molL−1. The relative standard deviation (for n =11) was 3.4% at 1.0×10−7 molL−1 of lead level. The proposed method was used for the determination of lead in the real water samples and standard reference materials. [Copyright &y& Elsevier]

Abstract: An electrochemical sensor based on a self-made electrode from recordable CDs was developed for the non-enzymatic detection of glucose by chronoamperometry. We discussed the amperometric current response of glucose with the change of potential, pH and electrode area, and determined the optimum detection conditions. The current response measurements were performed in a phosphate buffered solution (pH 6.5) with a potential of −0.50V, and presented a linearity over the range of 0.5–13mmol/L (r =0.996). The experimental results of the designed sensor demonstrate that this method has merits such as simple operation, low cost and rapid responses. The results of detecting glucose in blood samples were satisfactory. [Copyright &y& Elsevier]

Abstract: Electrochemical impedance immunosensor, with its high sensitivity from electrochemical impedance analysis and ideal specificity from the immunoassay, is increasingly used in the detection of a kind of phenoxy acid herbicides which is 2,4-Dichlorophenoxybutyric acid (2,4-DB). In this experiment, synthetic 2,4-DB antibodies were immobilized on the electrode by the crosslinking of l-Cysteine/glutaraldehyde, and 2,4-DB were measured by the increase of electron-transfer resistance when the immune reaction occurred, with Fe(CN)6 3−/Fe(CN)6 4− as the probe. Under optimal conditions, the change of resistance is in a linear relationship with the logarithm of the concentration in the range of 1.0×10−7–1.0×10−3 g/L (R=0.994) with the detection limit of 1.0×10−7 g/L (0.1ppb). This method bears such merits as simplicity in operation, high sensitivity, wide linear range, specificity, reproducibility and good stability. The actual soybean samples were analyzed with the recovery of 82.8%–102.3%. [Copyright &y& Elsevier]

Abstract: In this work, a kojic acid electrochemical sensor, based on a non-covalent molecularly imprinted polymer (MIP) modified electrode, had been fabricated in the lab-on-valve system. The sensitive layer was synthesized by cyclic voltammetry using o-phenylenediamine as the functional monomer and kojic acid as the template. The template molecules were then removed from the modified electrode surface by washing with NaOH solution. Differential pulse voltammetry method using ferricyanide as probe was applied as the analytical technique, after extraction of kojic acid on the electrode. Chemical and flow parameters associated with the extraction process were investigated. The response recorded with the imprinted sensor exhibited a response in a range of 0.01–0.2μmolL−1 with a detection limit of 3nmolL−1. The interference studies showed that the MIP modified electrode had excellent selectivity. Furthermore, the proposed MIP electrode exhibited good sensitivity and low sample/reagent consumption, and the sensor could be applied to the determination kojic acid in cosmetics samples. [Copyright &y& Elsevier]