All-Solid-State Polymeric Membrane Ion-Selective Electrodes Based on NiCo₂S₄ as a Solid Contact

The performance criteria for the design of all-solid-state ion-selective electrodes mainly include high electrode-to-electrode reproducibility and a low potential drift. Here, we introduce nickel cobalt sulfide (NiCo2S4) as a solid contact for ion-to-electron transduction based on multiple redox couples. NiCo2S4 materials with different morphologies can be prepared through a facile hydrothermal/solvothermal method. A NiCo2S4-based solid-contact Ca2+-ISE has been developed, which exhibits a Nernstian slope of 27.5 ± 0.2 mV/dec in the activity range from 1.0 × 10–6 to 2.9 × 10–2 M with a detection limit of 5.0 × 10–7 M. A variation of the standard potential E° for eight individual solid-contact electrodes can be obtained as low as 0.35 mV. Due to the synergistic effect of cobalt and nickel ions in the ternary sulfide, an excellent redox capacitance (565 μF) of the buried solid contact coated with the ion-selective membrane can be achieved and is much larger than those obtained from other redox solid-contact materials reported so far, thus yielding a high potential stability of 2.2 ± 0.4 μV/h. In addition, the NiCo2S4-based solid-contact Ca2+-ISE shows a reduced water layer at the sensing membrane/NiCo2S4 interface and provides an excellent resistance to the interferences from light, O2, and CO2. The proposed strategy utilizing NiCo2S4 as a solid contact is a promising alternative for the fabrication of calibration-free ASS-ISEs

Transition from Complete to Partial Wetting within Membrane Compartments

Transition from Complete to Partial Wetting within Membrane Compartment

Robust Potentiometric Microelectrodes for <i>In Situ</i> Sensing of Ion Fluxes with High Sensitivity

Simple, reproducible, and reliable preparation of robust potentiometric microelectrodes is both challenging and of great importance for noninvasive real-time ion sensing. Herein, we report a simple strategy for the large-scale synthesis of nickel cobalt sulfide (NiCo2S4) nanowire arrays grown on carbon fibers for potentiometric microelectrodes. The highly uniform NiCo2S4 nanowire array serving as a transduction layer can provide a high capillary pressure and viscous resistance for loading the ion sensing membrane and exhibit a large redox capacitance for improving the stability. An all-solid-state lead-selective microelectrode, which presents a detection limit of 2.5 × 10–8 M in the simulated soil solution, was designed as a model for noninvasive, in situ, and real-time detection of ion fluxes near the rice root surface. Importantly, the microsensor enables sensitive detection of trace-level ion-fluxes. This work provides a simple yet general strategy for designing potentiometric microelectrodes

Scanning electron microscopy images of soil colloids after co-culture.

<p>The first row is liquid co-culture with two fungi and the second row is solid co-culture with two fungi. Control: a) and d); low enzymatic fungi, <i>G. rutilus</i>, b) and e); high enzymatic fungi, <i>C striatus</i>, c) and f).</p

Cellulose and chitin metabolism related enzyme activity.

<p>a) chitinase; b) carboxymethyl cellulase; c) β-glucosidase. X axis labels: 1. <i>R. integra</i>; 2. <i>S. granulatus</i>; 3. <i>P. impudicus</i>; 4. <i>P. adiposa</i>; 5. <i>C. dryophila</i>; 6. <i>A. sylvicola</i>; 7. <i>C. striatus</i>; 8. <i>G. rutilus</i>; 9. <i>L. deliciosus</i>; 10. <i>G. mammosum</i></p

Functionalized Metal–Organic Framework UiO-66-NH-BQB for Selective Detection of Hydrogen Sulfide and Cysteine

Hydrogen sulfide (H2S) is an important signaling molecule related to many diseases. Thus, H2S has a great impact on the pathological and physiological processes in biological systems. Cysteine (l-Cys) is a building block for proteins and important metabolites. To understand their roles in the physiological metabolic procedures, the measurement of the H2S level and identifying cysteine in the biological system is significant. In this study, through the functionalization of UiO-66-NH2 by 4-(2,2-dicyanoethenyl)­benzoic acid (BQB), a novel UiO-66-NH-BQB is successfully synthesized and used as a fluorescence probe to recognize and detect H2S and l-Cys. The fluorescence signals of the probe are enhanced great when it is exposed to H2S or cysteine molecules; thus, it is able to determine quantificationally the H2S concentration in an aqueous solution. The detection limitation of the UiO-66-NH-BQB to H2S concentration is found to be as low as 1.74 μM. The developed fluorescent probe based on UiO-66-NH-BQB displays a high selectivity and excellent biocompatibility, which is very promising for recognition and sensing of biothiols in organisms

Protein and phosphorus metabolism related enzyme activity.

<p>a) protease; b) acid phosphatase X axis labels are the same to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111740#pone-0111740-g001" target="_blank">Fig. 1</a>.</p

List of definitions of comorbidities.

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STROBE checklist for items that should be included in reports of cohort studies.

(DOC)</p

Lignin metabolism related enzyme activity.

<p>a) Polyphenol oxidase; b) Laccase; (c) Guaiacol oxidase. X axis labels: 1. <i>R. integra</i>; 2. <i>S. granulatus</i>; 3. <i>P. impudicus</i>; 4. <i>P. adiposa</i>; 5. <i>C. dryophila</i>; 6. <i>A. sylvicola</i>; 7. <i>C. striatus</i>; 8. <i>G. rutilus</i>; 9. <i>L. deliciosus</i>; 10. <i>G. mammosum</i></p