Electrochemical And Optical Sensors Based On Polymer Composites And Selective Probes

Carrier-based ion-selective sensors are well-established analytical tools that have been widely used in many fields because of their sensitive and rapid detection and dynamically real-time monitoring capabilities. However, these sensors still have many drawbacks during their applications, such as low selectivity towards highly hydrogen anions, components leaching, long response time, potential instability, and so on. In order to exploit sensors with more ideal properties, a lot of work has been done as follows:(1) Fabricated a novel sulfate-selective electrochemical sensor with an imidozalium type of ionic liquid as new addictive. The ion-sensing cocktail containing plasticizer, poly (vinylchloride) (PVC), sulfate ionophore, anion exchanger and the ionic liquid (BMIMPF6) is dropped directly on a solid substrate to form the electrode.62.5wt% of BMIMPF6, showed good compatibility in PVC matrice. The components together can form transparent, homogenous membranes. Comparable to traditional sulfate-selective sensors, the addition of BMIMPF6 in this novel sensor showed much improved selectivity towards highly hydrophilic sulfate ion over other high lipophilic anions such as NO3-, SCN-, and ClO4-. In addition, this novel sensor showed wide detection range (10-5～10-2) and short response time toward sulfate. (2) Fabricated single-piece all-solid-state ion-selective electrode with polymer-carbon nanotube composites. The ion-sensing cocktail containing plasticizer, poly (vinylchloride) (PVC) and multi-wall carbon nanotube (MWCNTs) in polymeric dispersant is dropped directly on a solid substrate to form the electrode.5 wt% of Block polymer pluronic F-127 or poly (ethylene-co-acrylic acid) with MWCNTs showed good compatibility in plasticized PVC matrix. The introduction of MWCNTs as ion-to-electron transducer has much improved the potential stability of the solid-contact electrode. It also makes an essential role to enhance the hydrophobicity of the membrane-conductor interface, which contributes to the more stable potential signal by elimination of undesirable water layer at the interface. The single-piece solid-state sensors with different ionophores were easily fabricated. Such electrodes exhibited excellent sensing properties comparable to the liquid-contact electrodes.(3) We developed the highly sensitive bulk optodes with new synthesized rhodamine type of fluorescent chromoionophore. The fluorescent turn-on through spirolactam ring-opening of rhodamine dye inside the hydrophobic polymer phase can only be obtained by incorporating cation exchanger into the sensing membrane. The rhodamine-based optode containing copper ionophore exhibited nanomolar detection limit to copper ion at pH 5.5. By introducing an inert BODIPY derivative B as the reference dye, a fluorescence resonance energy transfer (FRET) process is established between the chromoionophore and the reference dye to allow the ratiometric fluorescence measurement. The discrimination between metal ions has been achieved by simply introducing different kinds of commercially available ionophores into the membrane. The proposed optodes exhibited wide response range, excellent reproducibility and fast response time.