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Graphene Oxide Doped Conducting Polymer Nanowires Fabricated by Soft Lithography for Gas Sensing Applications

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Abstract

This paper reported a high-performance e-nose type chemiresistive gas sensor composed of graphene oxide (GO) doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowires. Large scale and well-defined sub-100 nm nanowires were prepared using nanoscale soft lithography in a highly efficient and facile way, facilitating subsequent device integration. The responses of the nanowire sensors to volatile organic compounds (VOCs) can be tuned by the different polymer components, which are utilized to constitute unique identification codes for ethanol, n-hexane, acetone and p-xylene and realize the discrimination of different VOCs. Besides, the score plot and classification matrix obtained respectively from the principal component analysis (PCA) and linear discriminant analysis (LDA) provide sufficient information to differentiate different VOCs.

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... For this reason, graphene/polymer composites were also conducted in the investigations of gas sensing. Tang et al. reported an e-nose type chemiresistive gas sensor composed of graphene oxide doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) nanowires fabricated by soft lithography [118] . Large scale and well-defined sub 100 nm nanowires with different weight percentages of GO were arrayed to tune volatile organic compounds (VOCs) sensor responses, which were utilized to constitute unique identification codes for ethanol, n-hexane, acetone, and pxylene and realized the discrimination of different VOCs. ...
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... GO can detect the target species' lowest level with almost all the atoms exposed to the environment because of the high surface to volume ratio. It has also been reported that GO has a high CO2 adsorption capacity and excellent CO2 sensing properties [25,26]. The effects of temperature change, humidity, and CO2 concentration on GO-coated interdigital sensor have been analysed in this work. ...
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Twelve metal ions are analyzed by a microchip that was developed for high-performance recognition and analysis. The microchip enhances fluorescence at multiple channels and improves the discriminability of multi-analyte testing. The facile fabrication of the microchip and insights into sensing efficiency will be of great importance for the development of advanced discriminant analysis for complex analytes.
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An emerging approach for diagnosing LC relies on volatile organic compounds (VOC), viz. organic compounds with relatively high vapor pressure or volatility, that can be detected in the headspace of cancer cells or blood samples, and/or in the exhaled breath. Identification, separation, and integration of the peaks in measured chromatograms for each sample. This might involve the use of Gaussian and non-Gaussian peak-fitting software, algorithms for the numerical calculation of the peak area, and algorithms for background compensation. Using internal standards might improve the reliability of the results, allowing a compensation of spectral shifts prior to the peak integration. The available statistical tests differ in the assumptions concerning the tested groups or populations: Gaussian and non-Gaussian populations, paired and unpaired groups, comparison between two or more groups.
Article
The sorption equilibria and kinetics of three volatile organic compounds (VOCs)—benzene, chloroform, and acetone—in a newly developed divinyl-terminated poly(dimethylsiloxane) (PDMSvi)–oligo polymer were studied. The PDMSvi–oligo polymer was prepared from a hexane solution consisting of PDMSvi as the polymer, oligosilylstyrene as the crosslinker, and a platinum–divinyltetramethyldisiloxane complex as the Karstedt catalyst. The sorption uptake of each VOC by the polymer was measured gravimetrically at different VOC partial pressures at a constant temperature and at different temperatures between 24 and 50°C. The rate of VOC sorption was monitored until equilibrium was established. The solubility coefficient increased when the VOC activity increased, and the results revealed that the PDMSvi–oligo polymer was a good sorbent for the three VOCs examined. Relatively high solubilities of these VOCs were obtained in this polymer in comparison with those reported for conventional silicone rubbers. The Flory–Huggins model fit the observed equilibrium sorption isotherms of the benzene and chloroform systems very well, whereas the Koningsveld–Kleinjtens variation law had to be combined with the Flory–Huggins model to describe the sorption isotherm of acetone in the polymer film. The rates of sorption of the three VOCs in the polymer samples were generally rapid and controlled by Fickian diffusion. The diffusivities of benzene, chloroform, and acetone at 24°C, determined with the diffusion equation, were approximately 10−6 cm/s. The sorption and diffusion data revealed that the newly developed PDMSvi–oligo polymer was an excellent sorbent for the three VOCs examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 920–927, 2004
Article
The deposition of nanoscale conducting polymer patterns on semiconductor surfaces using DPN was reported. It was shown that electrostatic interactions between water soluble ink materials and charged substrates can provide a significant driving force for the generation of stable DPN patterns on semiconductor surfaces. Characterization of the patterned conducting polymers was performed by LFM and electrochemical methods, the results of which were fully consistent with the conclusion that conducting polymer molecules can be successfully transported from the tip to these types of charged surfaces.
Article
We report on the electrochemical growth of micro/nanowire devices using e-beam-patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable arrays. The concept of growing single wires and small arrays using this technique is demonstrated by single and double wires of Pd and polypyrrole with 500-nm and 1-µm widths up to 7-µm lengths and 200-nm thicknesses. The use of Pd wires as hydrogen sensors and polypyrrole wires as pH sensors is demonstrated. Semiconductor and metal nanowires and carbon nanotubes have been the subject of intense interest as sensors 1-4 and electronic devices for high-density circuits. 5-16 The tech-niques used to fabricate these devices have included using an atomic force microscope to manipulate individual carbon nanotubes onto prepatterned electrodes, 5 the random disper-sion of suspended carbon nanotubes in solution onto a substrate with prepatterned electrodes, 6-8 and using catalysts (as carbon nanotube nucleation sites) lithographically pat-terned on electrodes. 13,15 Although these methods have been adequate for demonstrating the operational characteristics of individual devices, they have intrinsic drawbacks of low throughput and limited controllability, which make them unattractive for large-scale circuits. Attempts to improve fabrication controllability have included applying an electric field for the postgrowth alignment of metal and semiconduc-tor nanowires 9,10 or for alignment during the growth of carbon nanotubes, 14 the growth of metal nanowire arrays on a selectively etched superlattice template followed by manual transfer to the desired substrate, 16 and the fluidic alignment of semiconductor nanowires on a substrate followed by e-beam lithography to form contacts. 2,11,12 Nanowire logic gates and a small-scale circuit have been successfully fabricated and demonstrated utilizing a layer-by-layer fluidic alignment. 12 However, device fabrication with controllability, reproducibility, and yield suitable for large-scale circuits remains a significant challenge.
Article
This paper reports on the integration of zinc oxide nanowires (ZnO NWs) with a silicon on insulator (SOI) CMOS (complementary metal oxide semiconductor) micro-hotplate for use as an alcohol sensor. The micro-hotplates consist of a silicon resistive micro-heater embedded within a membrane (composed of silicon oxide and silicon nitride, supported on a silicon substrate) and gold bump bonded aluminum electrodes that are used to make an ohmic contact with the sensing material. ZnO NWs were grown by a simple, low-cost hydrothermal method and characterised using SEM, XRD and photoluminiscence methods. The chemical sensitivity of the on-chip NWs to ethanol vapour (at different humidity levels) was characterised at two different temperatures namely, 300 °C and 400 °C (power consumption was 24 mW and 33 mW, respectively), and the sensitivity was found to be 0.1%/ppm (response 4.7 at 4363 ppm). These results show that ZnO NWs are a promising material for use as a CMOS ethanol gas sensor that offers low cost, low power consumption and integrated circuitry.
Article
A novel high-performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10 S cm−1 at 22 °C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1. Its high specific capacitance of 531 F/g was obtained in the potential range from 0 to 0.45 V at 200 mA/g by charge–discharge analysis compared to 216 F/g of individual PANI. The doping and the ratio of graphene oxide have a pronounced effect on the electrochemical capacitance performance of the nanocomposites.
Article
Zinc oxide nanorods were synthesized using a simple hydrothermal method. Formaldehyde-sensing characteristics were investigated without and with ultraviolet (UV) light irradiation. The gas response of nanorods to 110 ppm formaldehyde with UV light irradiation was about 120 times higher than that without UV light irradiation. The detection limit was as low as 1.8 ppm at room temperature. This high gas response under the UV light is attributed to photocatalytic oxidation. Furthermore, the significant improvements of the selectivity and recovery time were obtained after irradiating the nanorods with UV light. Our results demonstrated that applying UV light irradiation on the zinc oxide nanorods is an effective approach to achieve higher response and excellent selectivity to formaldehyde at room temperature.
Article
Ultrahigh density arrays of conducting polypyrrole (PPy) nanorods are fabricated directly on the indium-tin oxide coated glass by an electropolymerization within a porous diblock copolymer template. The nanorods are shown to have conductivity much higher than thin PPy films, due to the high degree of chain orientation, even though the separation distance for two neighboring PPy main chains is as small as 0.37 nm. The ultrahigh density arrays of conducting polymer nanorods have potential applications as sensor materials, nanoactuators, and organic photovoltaic devices.
Article
Within the past years there has been much effort in developing and improving new techniques for the nanoscale patterning of functional materials used in promising applications like nano(opto)electronics. Here a high-resolution soft lithography technique—nanomolding in capillaries (NAMIC)—is demonstrated. Composite PDMS stamps with sub-100 nm features are fabricated by nanoimprint lithography to yield nanomolds for NAMIC. NAMIC is used to pattern different functional materials such as fluorescent dyes, proteins, nanoparticles, thermoplastic polymers, and conductive polymers at the nanometer scale over large areas. These results show that NAMIC is a simple, versatile, low-cost, and high-throughput nanopatterning tool.
Article
We report here the use of nanomolding in capillaries (NAMIC) coupled with dithiocarbamate (DTC) chemistry to fabricate sub-50 nm quasi-1D arrays of 3.5 nm core gold nanoparticles (Au NPs) over large areas. Owing to chemical immobilization via the DTC bond, the patterned NP systems are stable in water and organic solvents, thus allowing the surface modification of the patterned Au NP arrays through thiol chemistry and further orthogonal binding of proteins. The electrical properties of these patterned Au NP wires have also been studied. Our results show that NAMIC combined with surface chemistry is a simple but powerful tool to create metal NP arrays that can potentially be applied to fabricate nanoelectronic or biosensing devices.
Article
The patterning of conducting polymer PEDOT:PSS, an excellent organic electrode material, with high resolution (50 nm, middle part of figure) on both rigid and flexible substrates by AFM nanoscratching (left part of figure) is demonstrated. The high density electrode array (108 elements cm-2) and small area electrode pair (0.5-0.6 µm2) achieved by this technique demonstrates its excellent patterning ability. The scratched nano/sub-micrometer channel shows excellent performance in organic transistors (right part of figure) with high performance and low voltage.
Article
This protocol provides an introduction to soft lithography--a collection of techniques based on printing, molding and embossing with an elastomeric stamp. Soft lithography provides access to three-dimensional and curved structures, tolerates a wide variety of materials, generates well-defined and controllable surface chemistries, and is generally compatible with biological applications. It is also low in cost, experimentally convenient and has emerged as a technology useful for a number of applications that include cell biology, microfluidics, lab-on-a-chip, microelectromechanical systems and flexible electronics/photonics. As examples, here we focus on three of the commonly used soft lithographic techniques: (i) microcontact printing of alkanethiols and proteins on gold-coated and glass substrates; (ii) replica molding for fabrication of microfluidic devices in poly(dimethyl siloxane), and of nanostructures in polyurethane or epoxy; and (iii) solvent-assisted micromolding of nanostructures in poly(methyl methacrylate).
Article
The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 degrees C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures.
Article
Conducting polymers (CPs) have been extensively studied and widely applied in various organic devices. To improve the performances or extend the functions of the devices, CPs usually have to be nanostructured. Electrosynthesis provides an effective and convenient one-step approach to CP nanomaterials. The resulting materials are usually oriented on the electrode surfaces and their properties are easy to be controlled. This critical review focuses on the syntheses of CP nanostructures and nanocomposites by electrochemical polymerization. The applications of the nanomaterials in organic devices such as sensors, actuators and memory devices also will be discussed (111 references).
Article
The dispersion behavior of graphene oxide in different organic solvents has been investigated. As-prepared graphite oxide could be dispersed in N, N-dimethylformamide, N-methyl-2-pyrrolidone, tetrahydrofuran, and ethylene glycol. In all of these solvents, full exfoliation of the graphite oxide material into individual, single-layer graphene oxide sheets was achieved by sonication. The graphene oxide dispersions exhibited long-term stability and were made of sheets between a few hundred nanometers and a few micrometers large, similar to the case of graphene oxide dispersions in water. These results should facilitate the manipulation and processing of graphene-based materials for different applications.
Article
Olfaction exhibits both high sensitivity for odours and high discrimination between them. We suggest that to make fine discriminations between complex odorant mixtures containing varying ratios of odorants without the necessity for highly specialized peripheral receptors, the olfactory systems makes use of feature detection using broadly tuned receptor cells organized in a convergent neurone pathway. As a test of this hypothesis we have constructed an electronic nose using semiconductor transducers and incorporating design features suggested by our proposal. We report here that this device can reproducibly discriminate between a wide variety of odours, and its properties show that discrimination in an olfactory system could be achieved without the use of highly specific receptors.
Article
By coating different conducting polymers of thiophene and its derivatives on quartz crystal microbalance (QCM) sensor surfaces, new novel QCM gas sensors have been produced in two simple ways, which could classify testing gas samples of volatile organic compounds (VOCs) gases. Principle components analysis (PCA) has been performed based on the QCM measurement results, which shows that our QCM sensors array has very good utilizing potential on sensing both polar and low-polar/nonpolar VOC gases. The sensitivity, selectivity, reproducibility and detection limit of QCM sensors have also been discussed. Quantitative variation of sensitivity response with the increasing concentration has been studied. (PLS) analysis and prediction of concentrations of single gas in mixtures have been carried out.
Article
The development of the electronic nose have paved the way for the classification of bacteria, to monitor air quality on the space shuttle, or to check the spoilage of foodstuff. However, the electronic nose still is unable to discriminated between flavors, perfumes, smells and as a replacement for the human nose. Although it has been used to detect some important nonodorant gases, it is not adapted to substances of daily importance in mammalian life such as the scent of other animals, foodstuff or spoilage. Due to such limitations, the electronic nose was developed to mimic the human nose. It turns out that the human nose's unequaled performance is not due to the high number of different human receptor cells, but their selectivity and their unsurpassed sensitivity for some analyte gases. As such, the success of the electronic nose will not rely on increasing the number of individual sensors and creating redundant information by adding more similar sensors, but rather on DNA, molecular, imprinted molecules or even mobilized natural receptors, which promise to increase the sensitivity and importantly selectivity. An increase in the sensitivity can be achieved by appropriate sample pretreatment and preconcentration techniques, whereas filters and separation units can be used to increase the selectivity and reduce interfering substances.
Meso- and macroporous Co
  • H Nguyen
  • S A El-Safty