No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Feasible H 2 S Sensing in Water with a Printed Amperometric Microsensor
ResearchGate has not been able to resolve any citations for this publication.
(1) Background: Hydrogen sulfide (H2S) is a widely recognized gasotransmitter, with key roles in physiological and pathological processes. The accurate quantification of H2S and reactive sulfur species (RSS) may hold important implications for the diagnosis and prognosis of diseases. However, H2S species quantification in biological matrices is still a challenge. Among the sulfide detection methods, monobromobimane (MBB) derivatization coupled with reversed phase high-performance liquid chromatography (RP-HPLC) is one of the most reported. However, it is characterized by a complex preparation and time-consuming process, which may alter the actual H2S level; moreover, a quantitative validation has still not been described. (2) Methods: We developed and validated an improved analytical protocol for the MBB RP-HPLC method. MBB concentration, temperature and sample handling were optimized, and the calibration method was validated using leave-one-out cross-validation and tested in a clinical setting. (3) Results: The method shows high sensitivity and allows the quantification of H2S species, with a limit of detection of 0.5 µM. Finally, it can be successfully applied in measurements of H2S levels in the serum of patients subjected to inhalation with vapors rich in H2S. (4) Conclusions: These data demonstrate that the proposed method is precise and reliable for measuring H2S species in biological matrices and can be used to provide key insights into the etiopathogenesis of several diseases and sulfur-based treatments.
Inkjet printing and 3D inkjet printing have found many applications in the fabrication of a great variety of devices which have been developed with the aim to improve and simplify the design and performance of sensors and analytical platforms. Here we review developments of these printing technologies being reported during the last 10 years and demonstrate their versatile applicability for the fabrication of improved sensing platforms and analytical and diagnostic sensor systems. Illustrative examples are reviewed in the context of particular advantages provided by inkjet printing technologies. Next to aspects of device printing and fabrication strategies, we highlight the utilization of inkjet dispensing, which can be implemented into common analytical tools utilizing customized inkjet printing equipment as well as state-of-the-art consumer inkjet printing devices. This review aims to providing a comprehensive overview of examples integrating inkjet and 3D inkjet printing technologies into device layout fabrication, dosing and analytical applications to demonstrate the versatile applicability of these technologies, and furthermore, to inspire the utilization of inkjet printing for future developments. This article is protected by copyright. All rights reserved.
The flexible and rechargeable energy storage device with excellent performance is highly desired due to the demands of portable and wearable devices. Herein, by integrating the bendability and stretchability of Polyvinyl alcohol (PVA), pseudocapacitance of Polyaniline (PANI), and the charge transport ability of carbon nanotubes (CNTs), PVA/CNT/PANI flexible film was fabricated as supercapacitor electrodes with excellent electrochemical performance and flexibility. Full-solid supercapacitor is prepared based on PVA/H 2 SO 4 gel electrolyte and as-prepared film electrodes. The device achieves an areal capacitance of 196.5 mF cm ⁻² with high cycling stability. The flexible properties of PVA, the conductivity of CNT, and the pseudo-capacitance of PANI contribute to the superior performance. Present work develops a facile and effective way for preparing flexible electrode materials.
Graphical Abstract
In present work, we fabricated PVA/CNT/PANI flexible film as supercapacitor electrodes with excellent electrochemical performance and flexibility.
Removal of hydrogen sulfide (H2S) released from various source processes is crucial because this compound can cause corrosion and environmental damage even at low concentration levels. The porous materials offer a wide variety of chemical architectures with tunable pore size and high surface area that are very promising for the adsorption of H2S molecules. This review attempts to comprehensively compile the current studies in the literature on hydrogen sulfide removal in gas purification processes using highly porous materials such as zeolites, carbon materials, activated carbon, porous metal oxides, mesoporous silica, and metal-organic frameworks as highly effective adsorbents. Possible interactions between the H2S and active adsorption sites of these materials are also discussed. Surface functionality and porosity play a crucial role in the H2S removal performance by virgin or modified porous materials. However, tailoring these materials to obtain high adsorption capacity, good selectivity, and suitable stability and regenerability and to retain structural integrity under high temperatures or in the presence of moisture are still the major challenges in the practical applications. According to the extensive background knowledge for H2S removal by different porous materials in this review, it can be expected that the readers gain the insight to the further developments in this area and design new cost-effective sorbents.
Anion exchange membranes (AEMs) contribute significantly to enhance the performance and efficiency of alkaline polymer electrolyte fuel cells (APEFCs). A sequence of composite anion exchange membranes (AEMs) consisting of poly(vinyl alcohol) (PVA), poly(diallyldimethylammonium chloride) (PDDA), and nano-zirconia (NZ) has been prepared by a solution casting technique. The effect of zirconia mass ratio on attribute and performance of composite AEMs was investigated. The chemical structures, morphology, thermal, and mechanical properties of AEMs were characterized by FTIR, SEM, thermogravimetric analysis, and universal testing machine, respectively. The performance of composite AEMs was verified using water uptake, swelling degree, ion-exchange capacity, and OH− conductivity measurement. The nano-zirconia was homogeneously dispersed in the PVA/PDDA AEMs matrix. The mechanical properties of the composite AEMs were considerably enhanced with the addition of NZ. Through the introduction of 1.5 wt.% NZ, PVA/PDDA/NZ composite AEMs acquired the highest hydroxide conductivity of 31.57 mS·cm−1 at ambient condition. This study demonstrates that the PVA/PDDA/NZ AEMs are a potential candidate for APEFCs application.
Hydroxyl anion conducting membrane composed of poly(vinyl alcohol) (PVA), poly(diallyldimethylammonium chloride) (PDDA), and hydroxylated multiwalled carbon nanotubes (MWCNTs-OH) have been synthesized via a facile blending-casting method assisted by a hot-chemical cross-linking process. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) showed that PDDA and MWCNTs-OH were successfully introduced into the PVA matrix and MWCNTs-OH could effectively improve the network structure of the membrane. With the addition of MWCNTs-OH, many properties of the membranes such as thermal, chemical, mechanical stability and swelling property were improved significantly. Most prominent is the improvement of mechanical property, where the PVA/PDDA/MWCNTs-OH(1:0.5/3 wt.%) membrane showed high tensile strength of 40.3 MPa, tensile elongation of 12.3% and high Young's modulus of 782.8 MPa. Moreover, MWCNTs-OH bound the polymer chains in the membranes more compactly, resulting in decreased water uptake. By tuning the mass fraction of PVA, PDDA, and MWCNTs-OH in the membrane, the maximum OH⁻ conductivity (0.030 S cm⁻¹ at room temperature) was achieved for the composition of 0.5 wt.% MWCNTs-OH doped with the PVA: PDDA (1:0.5 by mass) blend. The membranes showed excellent oxidative stability when treated with both a solution of H2O2 (30 wt.%) at room temperature and in a hot KOH solution (8 M) at 80 °C. Based on the full aliphatic structure membrane (PVA/PDDA-OH/1 wt.%MWCNTs-OH), membrane electrode assemblies (MEAs) fabricated with Pt/C cathode catalyst can achieve power densities of 41.3 mW cm⁻² and 66.4 mW cm⁻² in a H2/O2 system at room temperature and 40 °C, respectively. Using CoPc as the Pt-free cathode catalyst, power densities of 9.1 mW cm⁻² and 14.0 mW cm⁻² at room temperature and 40 °C were obtained, respectively.
The demand for real-time monitoring of cell functions and cell conditions has dramatically increased with the emergence of Organ-On-a-Chip (OOC) systems. However, the incorporation of co-cultures and microfluidic channels in...
Stable homogeneous dispersions of carbon nanotubes (CNTs) have been prepared by using sodium dodecyl sulfate (SDS) as dispersing agent. To our knowledge, it is the first report to quantitatively characterize colloidal stability of the dispersions by UV-vis spectrophometric measurements. When the sediment time reaches 500 h, the supernatant CNT concentration drops as much as 50% for the bare CNT suspension, compared to 15% with the addition of SDS. Furthermore, after 150 h, no precipitation is found for CNT/SDS dispersions, exhibiting an extreme stability. Zeta potential, auger electron microscopy, and FTIR analysis are employed to investigate the adsorption mechanism in detail. It has been concluded that the surfactant containing a single straight-chain hydrophobic segment and a terminal hydrophilic segment can modify the CNTs-suspending medium interface and prevent aggregation over long periods. The morphology of the CNT dispersions is observed with optical microscopy. An intermediate domain of homogeneously dispersed nanotubes exhibits an optimum at 0.5 wt% CNTs and 2.0 wt% SDS.
An amperometric sensor has been developed with high sensitivity for real-time measurement of H2S gas at room temperature (25 °C±2 °C). In order to enhance the utilization of platinum and improve its catalytic performance, an ultrathin and one-dimensional (1D) Pt nanotubes (Pt NTs, ∼3.5 nm in wall thickness) were designed and used as sensing electrode materials. Different concentrations of H2S gas were tested to evaluate the sensitivity of the sensor and to obtain the relationship between the electricity response signal and H2S gas concentration. At room temperature, the sensor based on Pt NTs shows better sensing performance than that based on Pt nanoparticles, which is mainly attributed to two factors, namely, the inherent characteristic of the hollow 1D Pt NTs. The Pt NTs-based sensor shows a detection limit as low as 0.025 ppb, which are the lowest among H2S gas sensors reported in the literatures. The response and recovery times are 0.75 s and 0.86 s for 0.8 ppb H2S, respectively. In addition, the sensor shows a wide range (100 ppm-0.025 ppb), high selectivity compared to other gases (including CO, NH3, CH2O, NO and NO2), good reproducibility, and satisfactory long-term stability. Thus, the ultrathin Pt NTs-based gas sensor would be a great potential to the real-time and online monitoring of the trace ppb-level H2S gas at room temperature.
Gas hazard was evaluated at Lavinio-Tor Caldara, the southernmost gas-discharging zone of the quiescent Albani Hills volcano in central Italy. Also this zone, like the other gas discharges of this volcanic complex, is located above a structural high of the buried Mesozoic carbonate basement, which represents the main reservoir for gas rising from depth. All extensional faults affecting the carbonates are leaking pathways along which gas may rise to the surface creating hazardous conditions. Gas is dominated by CO2 (>90 vol%) and the second component at Lavinio-Tor Caldara is H2S that displays the highest content (4.0–6.3 vol%) of all gas manifestations of the Rome region. This H2S enrichment corresponds to a marked decrease in ³He/⁴He (R/Ra) isotopic ratio suggesting that gas was contaminated in an upper crustal environment. The main gas discharge occurs at the natural reserve of Tor Caldara, in zones where past sulphur mining excavations removed the surficial impervious cover, or along a ditch. Comparison of the results of four soil CO2 flux surveys carried out in 2005–2018 at Miniera Grande within Tor Caldara, indicates that the highest soil CO2 release occurs shortly after local earthquakes. Continuous monitoring of CO2 and H2S air concentration and of wind speed has been carried out for four months in twelve anomalous gas realising sites of Tor Caldara. Results indicate that only H2S reaches lethal concentration (>250 ppm) near the soil in no wind nights, explaining the presence of small dead animals. At Lavinio, the main soil gas release occurs near old water wells that likely produced a gas blowout during drilling. A total release of over 20 tons/day from 2.93 km² of gas of endogenous origin, has been estimated for the Lavinio-Tor Caldara area by a detailed soil CO2 flux survey (2572 measurement points over an area of 3.65 km²). The main structural lineaments of the area have N-S and W-E directions, but also NE-SW and NW-SE directions are well represented. Some sectors of the investigated area are exposed to a severe gas hazard for people and animals and precautionary measures should be adopted.
With a growing demand for the availability of inexpensive, simple and rapid prototyped devices, the prospect of miniaturization of the reference electrodes using printing techniques becomes promising. A stable and reusable full inkjet-printed solid-state reference electrode (IPRE) was developed. The reference electrode was fully produced by consecutive inkjet printing of several layers. Ag ink was printed and chlorinated by NaClO printing forming a Ag/AgCl pseudo-reference electrode. Then, a surface protection by printing a Cl- saturated polyvinyl butyral membrane finally gave a reference electrode that demonstrated an outstanding performance comparable to commercial ones. This full inkjet printing fabrication strategy will improve the viability of producing low-cost miniaturized reference electrodes with interest in many electrochemical sensor dependent areas.
A procedure for supporting silver nanoparticles (AgNPs) on nylon is proposed. Besides, the membrane has been developed as a solid-phase colorimetric plasmonic sensor for volatile sulphide compounds (VSCs) like H2S, CH3SH and (CH3)2S. AgNP behaviour in the membrane has been studied by UV-vis diffuse reflectance spectrometry, Raman, High-resolution transmission electron microscopy (HR-TEM) and Scanning electron microscopy (SEM). The sensor responded by changing its color from yellow in absence of VSCs to several orange/brown colors in function of VSC concentration as occurs in solution; an increase in the hydrodynamic diameter, estimated by both, Asymmetric flow field flow fractionation (AF4) coupled on line to Dynamic light scattering (DLS) detector and batch DLS, is achieved when sulphide is added to the citrate capped AgNPs. Diffuse reflectance spectrometry and processed digital images obtained with a smartphone have been used as measurements and several transformations for quantitation are proposed; a linear concentration range of hydrogen sulphide from 150 to 1000 ppbv and detection limit (LOD) of 45 ppbv were achieved measuring after 10 min of the sensor exposition to the hydrogen sulphide atmosphere (2 L) for humidity percentages between 50 and 96 % and room temperature. Satisfactory results in terms of precision (< 10%) and selectivity were obtained. The new sensor reported was stable, sensitive, non-expensive, disposable, safe and user-friendly. Furthermore, it has successfully been applied to determine VSCs expressed as hydrogen sulphide in breath samples (2 L and 250 mL) as a proof of concept. The limit of detection can be improved by increasing the exposition time, if necessary.
Biogas is a vital renewable energy source that could play an effective role in fulfilling the world’s energy demand, not only in heat and power generation but also as a vehicle fuel in the future. Unfortunately, due to impurities, biogas requires a series of upgrading steps, which affects its economics and sustainability. Hydrogen sulfide (H 2 S) is one of the impurities that economically and environmentally hinder the biogas utilization as a source of energy. H 2 S removal from biogas using different technologies was extensively studied and established. One of such technology is adsorption. Adsorption by solid sorbents is considered as a suitable removal technique for toxic gases such as H 2 S because of its simplicity, easy handling, and environmental friendly sorbents. In this review, the utilization of waste material-based sorbent for H 2 S removal was appraised. Other gaseous components of biogas such as siloxanes, CO 2 , etc., are out of the scope of this work. The potential and effectiveness of the waste-derived sorbents, either raw waste or modified waste, were summarized in terms of its characteristics, suitability, and sustainability. The review provides an insightful analysis of different types of wastes such as sewage sludge, food waste, forestry waste, fly ash, and industrial wastes as an alternative to commercial adsorbents to adsorb H 2 S gas. Based on the analysis, it was concluded that if these sorbents are to be successfully commercialized, its economic analysis, regeneration conditions, and potential utilization of the spent sorbents has to be further exploited. Nevertheless, there is a great prospectus in the future for these waste materials to be utilized as sorbents for H 2 S removal.
Hydrogen sulfide (H 2 S) could be directly produced in mammals and recognized as a third gasotransmitter, which are closely associated with physiological and pathological processes. However, the detailed mechanism remains unclear, mainly due to a lack of robust sensors to accurately and quantitatively detect its concentrations in biological samples. Herein, for the first time, we develop a new electrochemical sensor for the detection of H 2 S based on the chemical reaction between copper oxide (CuO and Cu 2 O) and hydrogen sulfide (including H 2 S and HS ⁻ ) at a neutral solution (pH 7.4). Interestingly, when Na 2 S exists, copper and its oxide can be converted into Cu 2 S and CuS, resulting in an increase in the oxidation peak current of Cu 2 S-CuS with the increase of Na 2 S concentration, which is a direct evidence confirming the excellent sensor for the H 2 S detection. More importantly, the linear relationship between the oxidation peak currents of Cu 2 S-CuS and Na 2 S concentration is observed from 0.4 μM to 400 μM with a low detection limit of 0.2 μM, and satisfying selectivity. The developed strategy may have a great potential for further understanding the roles that biological H 2 S plays in biological systems.
A new detection system for the endogenous gaseous transmitter and environmental pollutant hydrogen sulfide is presented. It is based on the modulation of the fluorescence spectrum of a coumarin dye by the absorption spectrum of the recombinant hemoglobin I from clam Lucina Pectinata upon coordination of the analyte. While we establish that the reported affinity of rHbI for H2S has been overestimated, the association of the protein with an appropriate fluorophore allows fast, easy and reversible detection and quantification of hydrogen sulfide in buffer as well as biological fluids such as human plasma, with a quantification limit below 100 nM.
Low-cost and robust hydrogen sulfide (H2S) gas sensors can be utilized in different industrial applications. Earlier we have demonstrated an inexpensive wirelessly readable copper acetate based H2S gas sensor which was successfully employed for monitoring the quality of raw poultry. In this study we have thoroughly investigated and optimized the performance of inkjet-printed copper acetate based H2S gas sensor on flexible plastic substrate at room temperature. The effect of ink composition, print density, number of print nozzles and temperature of the substrate on sensor performance was tested. The long term stability of these sensors after exposure to H2S was studied extensively and was optimized as a function of the print density of copper acetate. The conversion of copper acetate to copper sulfide upon reaction with H2S was established by x-ray
photoelectron spectroscopy. We believe that the optimized sensor developed in this study with respect to stability, repeatability and material consumption will pave the way for the commercial use of these sensors e.g. in food quality monitoring and environmental applications.
A novel electrochemical sensor based on poly-(diallyldimethylammonium chloride) (PDDA), gold nanoparticles (AuNPs) and multi-walled carbon nanotubes (MWCNTs) modified organic electrochemical transistors (OECTs) was successfully fabricated and successfully applied to determination of Tyrosine (Tyr). The as-prepared device was characterized by field emission scanning electron microscopy (FE-SEM) and electrochemical workstation. Electrochemical performance of the modified OECT for detection of Tyr was investigated by cyclic voltammetry (CV) and chronoamperometry methods. Compared with the OECTs with the bare and the MWCNTs/PDDA modified OECTs Au gate electrode, the ultimate OECT with the MWCNTs/PDDA/AuNPs modified Au gate electrode displayed higher catalytic activity toward the oxidation of Tyr. The MWCNTs/PDDA/AuNPs modified OECT exhibited a linear response to Tyr over a wide concentration range of 0.3 μM to 10 μM with a detection limit of 10 nM in PBS solution (pH = 7.4), suitable for Tyr detection in human body fluids. Considering the main advantages of OECT such as low cost, no need for pre-treatment, easy to use and real-time detecting capability, we believe that the MWCNTs/PDDA/AuNPs modified OECT can potential be employed as a highly-sensitive, real-time, portable and disposable sensor for practical detection of Tyr in real sample.
Inkjet printing is a digital and non-contact printing technique that is beginning to be used in the manufacture of electronic devices, including electrochemical sensors. This article covers the main works featuring inkjet printing for the production of electrochemical sensors, and focuses especially on the works reported since 2015. The main factor limiting the application of inkjet printing in the manufacture of advanced devices stems mainly from the strict rheological conditions that the ink needs to meet. This is the reason why inkjet is best used in combination with other manufacturing techniques. Given their high degree of maturity and accessibility, home/office printers will likely lead a future wave in the manufacture of electronic devices, particularly at the development and prototyping stages.
A novel hybrid metallic cobalt insided in multiwalled carbon nanotubles/molybdenum disulfide (Co@CNT/MoS2) modified glassy carbon electrode (GCE) was fabricated with a adhesive of Nafion suspension and used as chemical sensors for sulfide detection. Single-layered MoS2 was coated on CNTs through magnetic traction force between paramagnetic monolayer MoS2 and Co particles in CNTs. Co particles faciliated the collection of paramagnetic monolayer MoS2 exfoliated from bulk MoS2 in solution. Amperometric analysis, cycle voltammetry, cathodic stripping analysis and linear sweep voltammetry results showed the Co@CNT/MoS2 modified GCE exhibited excellent electrochemical activity to sulfide in buffer solutions, but amperometric analysis was found to be more sensitive than the other methods. The amperometric response result indicated the Co@CNT/MoS2-modified GCE electrode was an excellent electrochemical sensor for detecting S²⁻ with a detection limit of 7.6 nM and sensitivity of 0.23 mA/μM. The proposed electrode was used for the determination of sulfide levels in hydrogen sulfide-pretreated fruits, and the method was also verified with recovery studies.
Water and wastewater treatment processes has been monitored using expensive yet inefficient “single-point” probes that can only measure single parameter at single point without obtaining a complete picture of physicochemical or biochemical status. The study targeted at this crucial challenge by developing novel micro-electrode array (MEA) sensors using ink-jet printing technology (IPT). Multiple mm-sized electrodes were printed on a flexible film for simultaneous monitoring of multiple parameters at high temporal and spatial resolution. The calibration of four types of MEA sensors (temperature, conductivity, dissolved oxygen (DO) and pH) in water solution showed high coefficient of determination (R² > 0.99) between the MEA readings and the parameter targeted. The shock tests demonstrated high accuracy of MEA sensors and rapid response with a reading frequency of 0.1 s, which captured the shock impacts in more details than commercial probes. Furthermore, patterning multiple types of MEA sensors on a single film enables the auto-correction between the parameters targeted and reduces the measurement errors. MEA surface property observed during 4-week immersion into wastewater and waste sludge revealed the intact structure and high mechanic stability. The study clearly demonstrated the unbeatable advantages of MEAs over existing “single-point” probes: compact sensor configuration, multiple-parameter monitoring in a single measurement, easy fabrication and ultra-low cost ($0.2/sensor), which will decode the system “black box”, provide complete dataset for switch control strategy, and enhance the treatment performance at the lowest capital and operational cost.
Treatment of high-strength sulfate wastewaters is becoming a research issue not only for its optimal management but also for the possibility of recovering elemental sulfur. Moreover, sulfate-rich wastewater production is expected to grow due to the increased SO2 emission contained in flue gases which are treated by chemical absorption in water. Bioelectrochemical systems (BESs) are a promising alternative for sulfate reduction with a lack of electron donor, since hydrogen can be generated in situ from electricity. However, complete sulfate reduction leads to hydrogen sulfide as final sulfur compound. This work is the first to demonstrate that, in addition to an efficient sulfate-rich wastewater treatment, elemental sulfur could be recovered in a biocathode of a BES under oxygen limiting conditions. The key of the process is the biological oxidation of sulfide to elemental sulfur simultaneously to the sulfate reduction in the cathode using the oxygen produced in the anode that diffuses through the membrane. High sulfate reduction rates (up to 388 mg S-SO4²⁻ L⁻¹ d⁻¹) were observed linked to a low production of sulfide. Accumulation of elemental sulfur over graphite fibers of the biocathode was demonstrated by energy dispersive spectrometry, discarding the presence of metal sulfides. Microbial community analysis of the cathode biofilm demonstrated the presence of sulfate-reducing bacteria (mainly Desulfovibrio sp.) and sulfide-oxidizing bacteria (mainly Sulfuricurvum sp.). Hence, this biocathode allows simultaneous biological sulfate reduction and biological sulfide oxidation to elemental sulfur, opening up a novel process for recovering sulfur from sulfate-rich wastewaters.
Bioelectronic interfaces require electrodes that are mechanically flexible and chemically inert. Flexibility allows pristine electrode contact to skin and tissue, and chemical inertness prevents electrodes from reacting with biological fluids and living tissues. Therefore, flexible gold electrodes are ideal for bioimpedance and biopotential measurements such as bioimpedance tomography, electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). However, a manufacturing process to fabricate gold electrode arrays on plastic substrates is still elusive. In this work, a fabrication and low-temperature sintering (≈200 °C) technique is demonstrated to fabricate gold electrodes. At low-temperature sintering conditions, lines of different widths demonstrate different sintering speeds. Therefore, the sintering condition is targeted toward the widest feature in the design layout. Manufactured electrodes show minimum feature size of 62 μm and conductivity values of 5 × 10 6 S m-1. Utilizing the versatility of printing and plastic electronic processes, electrode arrays consisting of 31 electrodes with electrode-to-electrode spacing ranging from 2 to 7 mm are fabricated and used for impedance mapping of conformal surfaces at 15 kHz. Overall, the fabrication process of an inkjet-printed gold electrode array that is electrically reproducible, mechanically robust, and promising for bioimpedance and biopotential measurements is demonstrated.
Hydroxyl anion conducting membranes have been developed using poly(vinyl alcohol) (PVA) as polymer matrix by incorporation of poly(diallyldimethylammonium chloride) (PDDA) as anion charge carriers. PDDA of four different molecular weight (namely PDDA-HMw, PDDA-MMw, PDDA-LMw and PDDA-ULMw) was incorporated in order to clarifying the effect of molecular weight on membrane performances. The membranes are characterized in detail by FTIR spectroscopy, scanning electron microscopy (SEM), thermal gravity analysis (TG), mechanical property, AC impedance technique, water uptake, swelling ratio, oxidation and alkaline stability to evaluate their applicability in alkaline fuel cells. The OH- conductivity of the membranes was found to be increased with increasing molecular weight of PDDA, and the maximum OH- conductivity of 0.027 S cm(-1) was achieved for PVA/PDDA-HMw membrane. The PVA/PDDA-HMw membrane also showed the best mechanical property and excellent thermal stability due to the most compact and dense network structure. All the membranes showed relatively high oxidative stability in 30%H2O2 and strong alkaline stability in 2 M KOH for 624 h at room temperature. The fuel cell performances of the MEAs with these membranes were 18.2, 23.4, 28.5 and 35.1 mW cm(-2) using H-2 and O-2 gases at 25 degrees C. The long-term stability of single-cell performance showed that the PVA/PDDA membrane could approximately last 80 h on the fuel cell with only a slight decrease of 0.1 V in cell potential. (C) 2013 Elsevier Ltd. All rights reserved.
It is reported for the first time that the performance of the electrochemical H2S sensor with the Nafion membrane pre-treated with the concentrated H2SO4 as the solid electrolyte is much more stable than that for the sensor with the Nafion membrane without H2SO4 pre-treatment. The sensitivity of the sensor is about 2.92μA/ppm. The response time of the sensor is about 9s. The detection limit is about 0.1ppm. Therefore, this kind of the electrochemical H2S gas sensor may be desirable for the practical application.
Size exclusion chromatography (SEC) with dual detection, i.e. employing a refractive index (RI), concentration sensitive, detector together with a multiangle light scattering (MALS) detector which is sensitive to molecular size, has been applied to study the solution properties of poly(diallyldimethylammonium chloride) (PDDA) in water containing different electrolytes, namely: NaCl, NaBr and LiCl, at 25°C. The analysis of a single highly polydisperse sample is enough for obtaining calibration curves for molecular weight and radius of gyration and the scaling law coefficients. The effect of the ionic strength on the conformational properties of the polymer can also be analyzed and unperturbed dimensions can be obtained by extrapolation of the values measured in a good solvent. The values of the characteristic ratio of the unperturbed dimensions thus obtained were: 17, 11 and 17, respectively, for NaCl, NaBr and LiCl solutions. Viscosity and conductivity measurements support the results obtained by SEC. Moreover, the experimental results are in good agreement with the theoretical calculations performed by combining molecular dynamics and Monte Carlo sampling procedures.
The performance of the solid polymer electrolyte (SPE)-H2S sensor has been studied. It was found that the electrochemical oxidation of H2S was controlled by the gas diffusion. That is the basis of the quantitative determination of H2S. The factors affecting the stability of the sensor have been studied. The results indicated that elemental sulfur was the main factor. In contrast with the H2S sensors reported in the liquid electrolyte systems, the stability of SPE-H2S sensor is better. The result was believed to be directly related to the porous and channeled structure of SPE-H2S electrode. In addition, the SPE-H2S sensor has many advantages, including a fast response, a satisfactory linearity and good reproducibility.