A versatile optode system for oxygen, carbon dioxide, and pH measurements in seawater with integrated battery and logger

Herein, we present a small and versatile optode system with integrated battery and logger for monitoring of O-2, pH, and pCO(2) in seawater. Three sensing materials designed for seawater measurements are optimized with respect to dynamic measurement range and long-term stability. The spectral properties of the sensing materials were tailored to be compatible with a commercially available laboratory oxygen logger that was fitted into a pressure housing. Interchangeable sensor caps with appropriate "sensing chemistry" are conveniently attached to the end of the optical fiber. This approach allows using the same instrument for multiple analytes, which offers great flexibility and minimizes hardware costs. Applications of the new optode system were demonstrated by recording depth profiles for the three parameters during a research cruise in the Baltic Sea and by measuring surface water transects of pH. The optode was furthermore used to monitor the concentration of dissolved oxygen in a seagrass meadow in the Limfjord, Denmark, and sensor packages consisting of pO(2), pH, and pCO(2) were deployed in the harbors of Kiel, Germany, and Southampton, England, for 6 d. The measurements revealed that the system can resolve typical patterns in seawater chemistry related to spatial heterogeneities as well as temporal changes caused by biological and tidal activity

Concanavalin A electrochemical sensor based on the surface blocking principle at an ion-selective polymeric membrane

We report on a new electrochemical sensor for Concanavalin A. It is based on blocking the surface of plasticized PVC membranes that were covalently modified with D-mannose using click chemistry. The interaction of D-mannose with Concanavalin A on the surface perturbs the flux of a marker ion for which the ion-selective membrane is responsive, and this results in a change in the electrochemical signal. The sensor was characterized using a variety of electrochemical protocols, and results were confirmed by quartz crystal microbalance experiments. The lowest limit of detection (10μgmL−1) was obtained using a membrane containing a cation exchanger and tetrabutylammonium ion as the marker ion. Figure An electrochemical sensor for Concanavalin A based on the surface blocking principle was prepared by covalent modification of a plasticized PVC membrane surface with D-mannose by click chemistr

Visible light induced photoacid generation within plasticized PVC membranes for copper (II) ion extraction

We present here an approach for light induced generation of lipophilic cation-exchangers in plasticized PVC membranes. Using camphorquinone as photosensitizer, a lipophilic cationic photoacid generator can produce protons under visible light illumination and endow the polymeric membrane with ion-exchanging property. After light illumination, the membrane containing a Cu2+ ionophore, is able to extract Cu2+ ions from the contacting aqueous solution. The acid generation upon light irradiation is relatively fast (ca. 100 s). The Cu2+ extraction process was imaged with fluorescence microscopy using Calcein, a fluorescence indicator whose fluorescence is quenched by Cu2+. Such a technique may form a new platform for light triggered ion concentration perturbation

Reversible Photodynamic Chloride-Selective Sensor Based on Photochromic Spiropyran

We report here for the first time on a reversible photodynamic bulk optode sensor based on the photoswitching of a spiropyran derivative (Sp). The photoswitching of Sp induces a large basicity increase in the polymeric phase, which triggers the extraction of Cl– and H+. Cl– is stabilized by a lipophilic chloride-selective ionophore inside the membrane, while H+ binds with the open form of Sp and induces a spectral change, hence providing the sensor signal. The system was studied with spectroscopic and electrochemical methods

Concanavalin A electrochemical sensor based on the surface blocking principle at an ion-selective polymeric membrane

We report on a new electrochemical sensor for Concanavalin A. It is based on blocking the surface of plasticized PVC membranes that were covalently modified with D-mannose using click chemistry. The interaction of D-mannose with Concanavalin A on the surface perturbs the flux of a marker ion for which the ion-selective membrane is responsive, and this results in a change in the electrochemical signal. The sensor was characterized using a variety of electrochemical protocols, and results were confirmed by quartz crystal microbalance experiments. The lowest limit of detection (10 μg mL−1) was obtained using a membrane containing a cation exchanger and tetrabutylammonium ion as the marker ion

Ultrasmall Fluorescent Ion-Exchanging Nanospheres Containing Selective Ionophores

We present a convenient precipitation procedure to fabricate ultrasmall fluorescent ion-selective nanosensors that operate on the basis of bulk ion-exchange sensing principles. The nanosphere matrix is composed of bis(2-ethylhexyl) sebacate (DOS) and a triblock copolymer Pluronic(®) F-127, which also functions as a surfactant to stabilize the nanoparticle. The particles can be prepared easily in large quantity without resorting to further complicated purification. Dynamic light scattering shows that these particles have a monodisperse size distribution with an average diameter of ∼40 nm, suggesting that the nanoparticles are among the smallest ionophore-based ion-selective nanosensors reported to date. A newly reported oxazinoindoline (Ox) as well as a Nile blue derivative (chromoionophore I) was used as a chromoionophore. Na(+)- and H(+)-selective nanospheres were characterized by absorbance and fluorescence spectroscopy. Owing to the very small size of the nanospheres, the suspension containing the particles is transparent. In the additional presence of the pH indicator HPTS, spectroscopic interrogation of pH and Na(+) in the same sample was demonstrated. As an example, the nanospheres were used to measure the Na(+) level in commercial mineral waters, and the results showed good agreement with atomic absorption spectroscopy (AAS)

In situ surface functionalization of plasticized poly(vinyl chloride) membranes by 'click chemistry'

We report here for the first time a universal method to achieve a covalent surface modification of plasticized poly(vinyl chloride) (PVC). A copper(I)-catalyzed azide-alkyne cycloaddition (’click chemistry’) is performed on plasticized PVC containing partial azide substitutions. This surface modification is performed under mild conditions after membrane casting and is likely to be generally applicable to electrochemical and optical sensors. The concept is illustrated by attaching fluorescein and sulfonated Nile blue derivatives, as well as tetraethylene glycol to the membrane surface. Characterization by confocal microscopy, ATR-IR, QCM, UV/Vis spectroscopy and pulsed chronopotentiometry supports the surface modification procedure. As an initial example of practical utility, tetraethylene glycol modification is shown to significantly reduce surface adsorption by albumin, as evidenced by QCM and electrochemical experiments

Towards Ion-Selective Membranes with Electrogenerated Chemiluminescence Detection: Visualizing Selective Ru(bpy)₃²⁺ Transport Across a Plasticized Poly(vinyl chloride) Membrane

We report here on an attractive concept to integrate electrochemically triggered ion-selective transport across an ion-selective plasticized PVC membrane and electrogenerated chemiluminescence (ECL) as a detection technique. This will eventually form the basis for an alternate transduction mechanism for electrochemical ion sensors. To this end, the selective extraction of the ECL reagent Ru(bpy)32+ is demonstrated by an o-NPOE plasticized PVC membrane doped with lipophilic cation-exchanger. Chemical imaging of Ru(bpy)32+ electrotransported across the PVC membrane demonstrates the feasibility of this concept as a future trend for two dimensional ion sensing