An All-solid-state Cd2+-selective electrode with a low detection limit

A new all-solid-state Cd2+-selective electrode with a low detection limit was prepared by using conjugated thiophene oligomer alpha-sexithiophene (alpha-6T) as solid contact deposited between an ionophore-doped poly(vinyl chloride) membrane and a gold disc substrate. The electrode exhibited a Nernstian response for Cd2+ ions over a wide concentration range of 10(-3)-10(-7) M with a detection limit as low as 1.3 x 10(-8) M. Results showed that the fabricated potentiometric sensor was suitable for use within the pH range of 2.0-9.0 and exhibited good reproducibility for long-term measurements. (C) 2011 Elsevier B.V. All rights reserved.A new all-solid-state Cd2+-selective electrode with a low detection limit was prepared by using conjugated thiophene oligomer alpha-sexithiophene (alpha-6T) as solid contact deposited between an ionophore-doped poly(vinyl chloride) membrane and a gold disc substrate. The electrode exhibited a Nernstian response for Cd2+ ions over a wide concentration range of 10(-3)-10(-7) M with a detection limit as low as 1.3 x 10(-8) M. Results showed that the fabricated potentiometric sensor was suitable for use within the pH range of 2.0-9.0 and exhibited good reproducibility for long-term measurements. (C) 2011 Elsevier B.V. All rights reserved

Improved potentiometric response of all-solid-state Pb2+-selective electrode

Zero-current ion-flux has a great influence on the characteristics of the ion-selective electrodes. In this work the improvement of analytical performance of all-solid-state Pb2+-selective membrane electrodes was demonstrated by adjusting the transmembrane ion flux. The study is focused on the relationship between the conditioning solution and the linear working range of the obtained electrodes for different sample matrixes. Results show that the electrode with appropriate conditioning keeps good reproducibility within linear working range. The utility of the electrode has been tested by successfully determining Pb2+ concentration in real water samples. (c) 2012 Elsevier B.V. All rights reserved

All-solid-state Zn²⁺-selective electrodes for wastewater measurements

A novel all-solid-state Zn2+-selective electrode with a low detection limit was prepared using poly (3-octylthiophene) (POT) as ion-to-electron transducer. The electrode exhibits a Nernstian response for Zn2+ ions over a wide concentration range from 10-3 to 10-9 M with a low detection limit of 1.0×10-9 M. Results also showed that the fabricated potentiometric sensors are suitable for the pH range of 3.0 ~7.1 with good stability in harsh conditions. © (2012) Trans Tech Publications

Highly Efficient Silver Catalyst Supported by a Spherical Covalent Organic Framework for the Continuous Reduction of 4-Nitrophenol

Developing new materials and novel technologies for the highly efficient treatment of toxic organic pollutants is highly desirable. Chemical reduction based on heterogeneous substrate/noble metal catalysts and the reducing agent NaBH4 has become an effective method in recent years. Here, a spherical covalent organic framework (SCOF) was designed to provide basic sites for Ag ions, by which small Ag NPs were immobilized on the SCOF to form Ag NPs@SCOF microspheres. The prepared microspheres exhibited a high catalytic reduction ability toward 4-nitrophenol (4-NP). An optimized permeation flux of 2000 L m(-2) h(-1) (LMH) and a more than 99% 4-NP reduction efficiency were obtained with flow-through experiments, which are far better than the reported results (below 200 LMH). Moreover, the microspheres could maintain stable catalytic performance under a continuous flow-through process. Our work provides an efficient material and technology that can be applied to easily treat toxic organic pollutants

A solid-contact Pb2+-selective electrode using poly (2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) as ion-to-electron transducer

In this work, a novel all-solid-state polymeric membrane Pb(2+)-selective electrode was developed by using for the first time poly(2-methoxy-5-(2&#39;-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) as solid contact. To demonstrate the ion-to-electron transducing ability of MEH-PPV, chronopotentiometry and electrochemical impedance spectroscopy measurements were carried out. The proposed electrodes showed a Nernstian response of 29.1 mV decade(-1) and a lower detection limit of subnanomolar level. No water film was observed with the conventional plasticized PVC membrane. This work demonstrates a new strategy for the fabrication of robust potentiometric ion sensors. (C) 2011 Elsevier B.V. All rights reserved.</p

Towards mass production of a spherical montmorillonite@covalent organic framework@gold nanoparticles heterostructure as a high-efficiency catalyst for reduction of methylene blue

Gold nanoparticles (Au NPs) supported by a covalent organic framework (COF) exhibited a remarkably catalytic performance towards organic pollutants, while the application is limited by the recovery and reuse from the mixture due to the size of Au NPs@COF at the nanoscale. Herein, Au NPs were in situ reduced on the surface of sulfhydryl groups functionalized new COF with NaBH4, followed by the deposition on polydopamine modified micron-sized porous spherical montmorillonite (SMt) to construct a spherical SMt@COF@Au NPs heterostructure. SMt was used here due to its excellent adsorption ability towards methylene blue (MB), increasing the concentration of MB near COF@Au NPs, thus accelerating the catalytic reaction. Hence, the optimized apparent reduction rate constant (Kapp) and turnover frequency (TOF) in our experiment could reach 8.32 min-1 and 3.2 ? 105 h-1, respectively, at 40 ?C and pH values of 10, which is much better than the reported. Furthermore, micro-sized SMt with self-sedimentary property could be easily recovered from the mixture without any devices involved. More importantly, the granular micro-sized morphology of the SMt-based heterostructure could facile transport on the product line and reduce the fouling, facilitating mass production COF@Au NPs based catalyst for application

Deciphering salt tolerance in tetraploid honeysuckle (Lonicera japonica Thunb.) from ion homeostasis, water balance and antioxidant defense

Polyploid plants are usually salt tolerant, but the underlying mechanisms remain fragmental. This study aimed to dissect salt resistance of tetraploid honeysuckle (Lonicera japonica Thunb.) from ion balance, osmotic adjustment and antioxidant defense by contrasting with its autodiploid through pot experiments. Less salt-induced reduction in leaf and root biomass confirmed higher tolerance in tetraploid honeysuckle, and moreover, its greater stability of photosynthetic apparatus was verified by mild influence on delayed chlorophyll fluorescence transients. Compared with the diploid, greater root Na+ exclusion helped alleviate salt-induced decrease in leaf K+/Na+ for maintaining ion balance in tetraploid honeysuckle, and relied on Na+/H+ antiporter activity, because their difference of root Na+ exclusion disappeared after applying a specific inhibitor of Na+/H+ antiporter. Lower reduction in leaf relative water content suggested higher tolerance to osmotic pressure in tetraploid honeysuckle under salt stress, which hardly resulted from osmotic adjustment given the similar decrease extent of leaf osmotic potential with that in the diploid. In contrast to significant elevated leaf lipid peroxidation and superoxide dismutase and ascorbate peroxidase activities in the diploid, no obvious changes in them suggested that tetra-ploid honeysuckle never suffered salt-induced oxidative stress. According to more accumulated leaf chlorogenic acid and phenolics and greater elevated leaf phenylalanine ammonia-lyase activity and transcription, leaf phenolic synthesis was enhanced greater in tetraploid honeysuckle upon salt stress, which might serve to prevent oxidative threat by consuming reducing power. In conclusion, polyploidy enhanced salt tolerance in honeysuckle by maintaining ion homeostasis and water balance and preventing oxidative stress

Synthesis and characterization of monoazathiacrown ethers as ionophores for polymeric membrane silver-selective electrodes

Nine monoazathiacrown ethers have been synthesized and explored as ionophores for polymeric membrane Ag+-selective electrodes. Potentiometric responses reveal that the ion-selective electrodes (ISEs) based on 2,2'-thiodiethanethiol derivatives can exhibit excellent selectivities toward Ag+. The plasticized poly(vinyl chloride) membrane electrode using 22-membered N2S5-ligand as ionophore has been characterized and its logarithmic selectivity coefficients for Ag+ over most of the interfering cations have been determined as &lt;-8.0. Under optimal conditions, a lower detection limit of 2.2 x 10(-10) M can be obtained for the membrane Ag+-ISE. (C) 2010 Elsevier B.V. All rights reserved.Nine monoazathiacrown ethers have been synthesized and explored as ionophores for polymeric membrane Ag(+)-selective electrodes. Potentiometric responses reveal that the ion-selective electrodes (ISEs) based on 2,2'-thiodiethanethiol derivatives can exhibit excellent selectivities toward Ag(+). The plasticized poly(vinyl chloride) membrane electrode using 22-membered N(2)S(5)-ligand as ionophore has been characterized and its logarithmic selectivity coefficients for Ag(+) over most of the interfering cations have been determined as <-8.0. Under optimal conditions, a lower detection limit of 2.2 x 10(-10) M can be obtained for the membrane Ag(+)-ISE. (C) 2010 Elsevier B.V. All rights reserved

Soil greenhouse gas emissions reduce the contribution of mangrove plants to the atmospheric cooling effect

Mangrove soils have been recognized as sources of greenhouse gases, but the atmospheric fluxes are poorly characterized, and their adverse warming effect has rarely been considered with respect to the potential contribution of mangrove wetlands to climate change mitigation. The current study balanced the warming effect of soil greenhouse gas emissions with the plant carbon dioxide (CO _2 ) sequestration rate derived from the plants’ net primary production in a productive mangrove wetland in South China to assess the role of mangrove wetlands in reducing the atmospheric warming effect. Soil characteristics were also studied in the summer to examine their relationships with gas fluxes. The soil to atmosphere fluxes of nitrous oxide (N _2 O), methane (CH _4 ) and CO _2 ranged from −1.6 to 50.0 μ g m ^−2 h ^−1 , from −1.4 to 5360.1 μ g m ^−2 h ^−1 and from −31 to 512 mg m ^−2 h ^−1 , respectively, which indicated that the mangrove soils act as sources of greenhouse gases in this area. The gas fluxes were higher in summer than in the cold seasons and were variable across mangrove sites. Gas fluxes in summer were positively correlated with the soil organic carbon, total nitrogen, and ammonia contents. The mangrove plants sequestered a considerable amount of atmospheric CO _2 at rates varying from 3652 to 7420 g CO _2 m ^−2 yr ^−1 . The ecosystem acted as a source of CH _4 and N _2 O gases but was a more intense CO _2 sink. However, the warming effect of soil gas emissions accounted for 9.3–32.7% of the plant CO _2 sequestration rate, partially reducing the benefit of mangrove plants, and the two trace gases comprised 9.7–33.2% of the total warming effect. We therefore propose that an assessment of the reduction of atmospheric warming effects by a mangrove ecosystem should consider both soil greenhouse gas emissions and plant CO _2 sequestration