21 research outputs found
Simple, Robust, and Plasticizer-Free Iodide-Selective Sensor Based on Copolymerized Triazole-Based Ionic Liquid
Novel solid-contact iodide-selective electrodes based on covalently attached 1,2,3 triazole ionic liquid (IL) were prepared and investigated in this study. Triazole-based IL moieties were synthesized using click chemistry and were further copolymerized with lauryl methacrylate via a simple one-step free radical polymerization to produce a "self-plasticized" copolymer. The mechanical properties of the copolymer are suitable for the fabrication of plasticizer-free ion-selective membrane electrodes. We demonstrate that covalently attached IL moieties provide adequate functionality to the ion-selective membrane, thus achieving a very simple, one-component sensing membrane. We also demonstrate that the presence of iodide as the counterion in the triazole moiety has direct influence on the membrane's functionality. Potentiometric experiments revealed that each electrode displays high selectivity toward iodide anions over a number of inorganic anions. Moreover, the inherent presence of the iodide in the membrane reduces the need for conditioning. The nonconditioned electrodes show strikingly similar response characteristics compared to the conditioned ones. The electrodes exhibited a near Nernstian behavior with a slope of -56.1 mV per decade across a large concentration range with lower detection limits found at approximately 6.3 Ă— 10(-8) M or 8 ppb. These all-solid-state sensors were utilized for the selective potentiometric determination of iodide ions in artificial urine samples in the nanomolar concentration range
Robust and ultrasensitive polymer membrane-based carbonate-selective electrodes
Quantitative analysis of the carbonate species within clinical and environmental samples is highly critical to the advancement of accurate environmental monitoring, disease screening, and personalized medicine. Herein we report the first example of carbonate detection using ultrasensitive ion selective electrodes (ISEs). The low detection limit (LDL) of these electrodes was at least 4 orders of magnitude lower than the best currently existing carbonate sensors. This was achieved by a simple alteration of the sensor's conditioning protocol. This resulted in the reduction of ion fluxes across the membrane interface consequently lowering the LDL to picomolar levels. The proposed ISEs exhibited near-Nernstian potentiometric responses to carbonate ions with a detection limit of 80 pmol L(-1) (5 ppt) and was utilized for direct determination of carbonate in seawater. Moreover, the new methodology has produced electrodes with excellent reproducibility, robustness, and durability. It is anticipated that this approach may form the basis for the development of highly sensitive and robust ion selective electrodes capable of in situ measurements
Communication—sulfonated poly (ether ether ketone) as cation exchange membrane for alkaline redox flow batteries
A sulfonated poly (ether ether ketone) (sPEEK) was tested as the separator in a full alkaline flow battery with 2,6-dihydroxyanthraquinone-ferro/ferricyanide, DHAQ-FeCy, redox couples. Cell performance was compared to that of an identical cell utilizing a perfluorosulfonic acid (PFSA) membrane. Replacement of the PFSA membrane with sPEEK resulted in a 10% power density increase, a 40% decrease in capacity loss per day and an 85-fold decrease in ferricyanide permeation. Though long-term stability of sPEEK in alkaline media requires improvement, these results highlight the potential to produce non-fluorinated membranes with better performance in organic redox flow batteries than the commercially available PFSAs. © The Author(s) 2018
Time- and Composition-Dependent Evolution of Distinctive Microstructures in Bitumen
Bitumen’s
chemistry often results in complicated intermolecular
associations, which are manifested by the diverse microstructures
as observed by atomic force microscopy (AFM). These microstructures
largely contribute to bitumens’ bulk mechanical properties;
therefore, it is essential to understand the chemical–microstructural–mechanical
relationships for optimal design of bitumen-related applications.
However, the complex nature of bitumen and the various influencing
factors often lead to practical challenges in investigation of bitumens’
microstructures and their chemical origins. This study aims at addressing
some of the main concerns related to AFM characterization of bitumens’
microstructures, namely the dependence of bitumens’ microstructures
on such factors as sample preparation methods, annealing conditions
and durations, and chemical composition. Our results suggest that
microstructures of bitumen films of a few micrometers or thicker (i.e.,
the thickness of the asphalt-coating layer over the aggregates in
asphalt concrete) were comparable regardless of their sample preparation
methods, provided that toluene was likely completely removed. Additionally,
bitumens annealed at room temperature for over 2 months showed time-dependent
microstructures, which correlate well with bitumens’ room-temperature
steric hardening behavior as verified by other researchers using modulated
differential scanning calorimetry. Microstructures of the bitumen
films stabilized after different annealing durations depending on
the dimensions of the molecular structures and the complexity of the
molecular interactions among the multiple phases in each bitumen.
Distinctive microstructures were observed for remixed bitumens with
increasing asphaltene concentrations. Consistency between our observations
and other relevant literature suggests that microstructures observed
by AFM are probably not just a surface phenomenon. The above findings
provide deeper insights into the establishment of the complicated
chemical–mechanical relationships for bitumen that pave the
path toward tuned bitumen performance