CC Bonding of Graphene Oxide on 4‐Aminophenyl Modified Gold Electrodes towards Simultaneous Detection of Heavy Metal Ions

This paper studied the electrochemical sensors based on C? C bonding of graphene oxide (GO) on π‐conjugated aromatic group modified gold electrodes for simultaneous detection of heavy metal ions. For comparison, another sensing interface Au‐Ph‐NH‐CO‐GO, in which GO was modified to Au‐Ph‐NH₂ interfaces by amide bonding. On the basis of the principle of heavy metal ions complexation with oxygenated species on GO, the fabricated sensing interfaces were used for the simultaneous determination of Pb²⁺, Cu²⁺ and Hg²⁺. The performance of two sensing interfaces for simultaneous detection of three metal ions was compared. Au‐Ph‐GO sensing interface demonstrated higher sensitivity and better repeatability than Au‐Ph‐NH‐CO‐GO sensing interface.     

Ultrasensitive Determination of Vitamin B12 Using Disposable Graphite Screen‐Printed Electrodes and Anodic Adsorptive Voltammetry

A facile, rapid and ultra‐sensitive method for the determination of vitamin B₁₂ (cyanocobalamin) at the sub‐nanomolar concentration range by using low‐cost, disposable graphite screen‐printed electrodes is described. The method is based on the cathodic preconcentration of square planar vitamin B_12s, as occurred due to the electro reduction of Co(III) center in vitamin B_12a to Co(I), at ?1.3 V versus Ag/AgCl/3 M KCl for 40 s. Then, an anodic square wave scan was applied and the height of the peak appeared at ca. ?0.73 V versus Ag/AgCl/3 M KCl, due to the oxidation of Co(I) to Co(II) in the adsorbed molecule, was related to the concentration of the vitamin B₁₂ in the sample. EDTA was found to serve as a key‐component of the electrolyte by eliminating the background signal caused by metal cations impurities contained in the electrolyte (0.1 M phosphate buffer in 0.1 M KCl, pH 3). It also blocks trace metals contained in real samples, thus eliminating their interference effect. The method was optimized to various working parameters and under the selected conditions the calibration curve was linear over the range 1×10^?10–8×10^?9 mol L^?1 vitamin B₁₂ (R²=0.994), while the limit of detection for a signal‐to‐noise ratio of 3 (7×10^?11 mol L^?1 vitamin B₁₂) is the lowest value of any reported in the literature for the electrochemical determination of vitamin B₁₂. The sensors were successfully applied to the determination of vitamin B₁₂ in pharmaceutical products.     

Large‐Area Alignment of Tungsten Oxide Nanowires over Flat and Patterned Substrates for Room‐Temperature Gas Sensing

Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single‐crystalline ultrathin W₁₈O₄₉ nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir–Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H₂ at room temperature.     

Cu3(hexaiminotriphenylene)2: An Electrically Conductive 2D Metal–Organic Framework for Chemiresistive Sensing

The utility of metal–organic frameworks (MOFs) as functional materials in electronic devices has been limited to date by a lack of MOFs that display high electrical conductivity. Here, we report the synthesis of a new electrically conductive 2D MOF, Cu₃(HITP)₂ (HITP=2,3,6,7,10,11‐hexaiminotriphenylene), which displays a bulk conductivity of 0.2 S cm^?1 (pellet, two‐point‐probe). Devices synthesized by simple drop casting of Cu₃(HITP)₂ dispersions function as reversible chemiresistive sensors, capable of detecting sub‐ppm levels of ammonia vapor. Comparison with the isostructural 2D MOF Ni₃(HITP)₂ shows that the copper sites are critical for ammonia sensing, indicating that rational design/synthesis can be used to tune the functional properties of conductive MOFs.     

Responsive Inverse Opal Hydrogels for the Sensing of Macromolecules

Dual responsive inverse opal hydrogels were designed as autonomous sensor systems for (bio)macromolecules, exploiting the analyte‐induced modulation of the opal’s structural color. The systems that are based on oligo(ethylene glycol) macromonomers additionally incorporate comonomers with various recognition units. They combine a coil‐to‐globule collapse transition of the LCST type with sensitivity of the transition temperature toward molecular recognition processes. This enables the specific detection of macromolecular analytes, such as glycopolymers and proteins, by simple optical methods. While the inverse opal structure assists the effective diffusion even of large analytes into the photonic crystal, the stimulus responsiveness gives rise to strong shifts of the optical Bragg peak of more than 100 nm upon analyte binding at a given temperature. The systems’ design provides a versatile platform for the development of easy‐to‐use, fast, and low‐cost sensors for pathogens.     

Dynamic Bio-Barcode Assay Enables Electrochemical Detection of a Cancer Biomarker in Undiluted Human Plasma: A Sample-In-Answer-Out Approach

There is a need for biosensing systems that can be operated at the point-of-care (POC) for disease screening and diagnostics and health monitoring. In spite of this, simple to operate systems with the required analytical sensitivity and specificity in clinical samples, using a sample-in-answer-out approach, remain elusive. Reported here is an electrochemical bio-barcode assay (e-biobarcode assay) that integrates biorecognition with signal transduction using molecular (DNA/protein) machines and signal readout using nanostructured electrodes. The e-biobarcode assay eliminates multistep processing and uses a single step for analysis following sample collection into the reagent tube. A clinically relevant performance for the analysis of prostate specific antigen (PSA) in undiluted and unprocessed human plasma: a log-linear range of 1 ng mL⁻¹–200 ng mL⁻¹ and a LOD of 0.4 ng mL⁻¹, was achieved. The e-biobarcode assay offers a realistic solution for biomarker analysis at the POC.     

In-situ growth of V2O5 flower-like structures on ceramic tubes and their trimethylamine sensing properties

V₂O₅ flower-like structures assembled by thin nanosheets were in-situ growth on ceramic tubes by hydrothermal process. The structural characterization indicates that V₂O₅ flower-like structures is orthogonal diamond phase, which entirely covered on the surface of ceramic tubes. TMA sensing measured results revealed that the sensor based on V₂O₅ flower-like structures exhibited fast reversible and response, good selectivity to TMA and good stability at 200 °C. The good sensing performance may be ascribed to flower-like structures and directly growth sensing film on the ceramic tube without structure damage. Our works give a simple in-situ growth flower-like structures route on sensing device, which exhibits potential application for detecting trace amounts of TMA gas.     

智能手机在生化传感分析中的应用进展

该文主要综述了基于智能手机生化检测的光学和电化学检测技术,及其在生化传感分析中强大的通信手段。重点介绍了智能手机集成的生化传感器技术的性能、优点,及其在生化检测中的应用,讨论了目前智能手机在生化传感分析方面存在的局限性和面临的挑战,并展望了未来的发展方向和潜在的机遇。     

Plasmonic sensors based on thick metal film perforated with rectangular nanohole arrays

The dependence of optical properties on the ambient medium, the period of nanohole arrays and the metal film thickness in a thick silver film perforated with rectangular nanohole arrays is investigated using the finite‐difference time‐domain technique. As a result of the coupling between top and down surface plasmon polaritons, mediated by localized surface plasmon resonances supported by the metallic rectangular nano‐ holes, interesting light phenomena are observed for varying thickness of the metal film and period of the rectangular nanohole arrays. Based on the dependence of the optical properties on the ambient medium, the possibility of exploiting thick metal rectangular nanohole arrays as plasmonic sensors is further discussed, the potential application as plasmonic sensors is revealed. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)