A new type of all-solid-state reference electrode was designed and characterized. The electrodes are based on a polymer/inorganic salt composite and a silver/silver chloride reference element. A rigorous testing procedure was used to reveal the possible influence of pH, solution composition, as well as the concentration and mobility of ions. The tests demonstrated the insensitivity of the electrodes to the matrix effects, excellent stability of the potential readings, and significantly reduced leakage of inorganic salt. In the performed tests the composite reference electrodes were on a par with or better than the high-quality commercial reference electrodes. The reference electrodes described here are of analytical quality allowing for continuous, prolonged, and intensive usage.
Multi-walled carbon nanotubes (MWCNTs) were compared with poly(3-octylthiophene) (POT) as ion-to-electron transducer in all-solid-state potassium ion-selective electrodes with valinomycin-based ion-selective membranes. MWCNTs and POT were mixed with the other components of the potassium ion-selective membrane cocktail (valinomycin, KTpClPB, o-NPOE, PVC, THF) which was then applied on a glassy carbon (GC) substrate to prepare single-piece ion-selective electrodes (SPISEs). Results from potentiometric and impedance measurements showed that the MWCNT-based electrodes have a more reproducuible standard potential and a lower overall impedance than the electrodes based on POT. Both types of electrodes showed similar sensitivity to potassium ions and no redox sensitivity.
Acid-precipitated
lignin nanoparticles with a cationic polymer
coating exhibit antibacterial activity when infused with silver. While
the use of such particles would be beneficial due to their high antibacterial
activity with a low silver content, their production holds steps that
are difficult to scale up to inexpensive industrial manufacture. For
example, the production of acid-precipitated lignin nanoparticles
requires the use of ethylene glycol, which is not easily recycled.
Furthermore, the binding of silver to these particles is weak, and
thus the particles need to be used rapidly after preparation. Here,
we show that with a deprotonation reaction of an organic solution
of anhydrous lignin and subsequent ion exchange with silver nitrate
and colloid formation by solvent exchange, highly spherical silver
carboxylate colloidal lignin particles (AgCLPs) can be prepared. Silver
is not released from the particles in deionized water but can be released
in physiological conditions, shown by their high antibacterial efficacy
with low silver loading. In comparison to lignin nanoparticles with
weakly bound silver, AgCLPs have high antibacterial activity even
without cationic polyelectrolyte coating, and they retain their antibacterial
activity for days. While the rapid depletion of silver from silver-infused
lignin nanoparticles can be considered beneficial for some applications,
the sustained antibacterial activity of the AgCLPs with ionically
bound silver will enable their use in applications where silver nanoparticles
have been previously used. Our results demonstrate that CLPs, which
can be produced with a closed cycle process on a large scale, can
be rapidly and quantitatively functionalized into active materials.
Ion-selective organic electrochemical junction transistors (IS-OEJTs) were prepared and their performance was studied for the detection of potassium, calcium, and silver ions. In this kind of sensors the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrene sulfonate) (PSS), PEDOT: PSS, is utilized for transduction of chemical information to electronic information in the solid state. In order to achieve selectivity, the channel region of the transistors was coated with ionophore-based polymeric membranes. The organic electrochemical junction transistors (OEJTs) studied in this work differ from the field-effect transistors in the fact that the change in drain/source current is not induced by an electric field but rather by electrochemical reduction/oxidation (undoping/doping) of the conducting polymer in the channel region between the drain and source. Therefore the transistors studied in this work are called electrochemical junction transistors and not fieldeffect transistors. They are rather regarded as bipolar junction transistors where the source, drain, and gate terms are replaced with emitter, collector, and base, respectively. À1 M -10 À4 M (with 0.1 M K þ as the interfering ion) was achieved by using ca.10 wt% ionophore and 5 wt% lipophilic salt. Ag þ -selective OEJTs, both in presence and absence of ISM, gave more complicated response than Ca 2þ -or K þ -selective OEJTs. One reason is that Ag þ is an electroactive ion that may oxidize the PEDOT: PSS transducer layer even in the absence of the base voltage.
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