A New Solid-State pH Sensor and Its Application in the Construction of all Solid-State Urea Biosensor

Abstract

A new solid-state pH sensor is developed using neutral poly(3-cyclohexyl thiophene) assembled over a Pt disk electrode. The new sensor is developed following two different approaches; 1) the neutral poly(3-cyclohexyl thiophene) dissolved in chloroform and subsequent coating on to a Pt disk electrode; 2) the neutral polymer is incorporated into plasticized poly(vinyl chloride) matrix membrane. In both cases the polymer modi®ed electrode is sensitive to pH and a reversible super Nernstian behavior is observed. The typical response of the pH sensor and its reversibility are reported. The polymer coated electrode is subsequently used to construct an all solid-state urea sensor. The construction of this new urea sensor involves the following two major steps; a) 20 mL of urease solution (40 mg /mL) is allowed to assemble overnight at 4 C over neutral poly (3-cyclohexyl thiophene) modi®ed electrode; b) an organically modi®ed sol-gel layer is allowed to form over the urease adsorbed polymer modi®ed electrode. The new solid-state urea sensor provides excellent reproducibility of the measurements and is stable for 3 months when stored at 4 C under dry condition. The typical response of the solid-state urea sensor and the calibration plot of urea analysis are reported.

Ion-Selective Electrodes with Three-Dimensionally Ordered Macroporous Carbon as the Solid Contact

“…Some of the electrodes using these polymers as an intermediate layer have been reported to be sensitive to CO 2 and pH, such as in the case of PPy, PANI, and poly(3octylthiophene) (POT). [25][26][27][28][29][30][31][32] For PANI, partial conversion from its conducting to its nonconducting emeraldine salt form was found during long-term measurements (1-3 months), 33 which results in a decrease of the electrode potential. Moreover, some polymers, such as PT, are organic semiconductors with a suitable band gap for photon absorption, giving SC-ISEs that are photoresponsive.…”

Physioelectrochemical Investigation of Electrocatalytic Oxidation of Saccharose on Conductive Polymer Modified Graphite Electrode

“…Particularly, elucidating the bioelectrochemistry and electroanalysis of biologically important substances, are under intense research with the use of chemically modified electrodes. Several conducting polymers, such as polypyrrole (PPy), polyaniline (PANI), polythiophene (PTH) and poly ortho amino phenol (POAP), have been already in extensive use in order to immobilize desired chemical species and enzymes for development of sensors [19][20][21][22][23].…”

Urea Biosensor Based on Conducting Polymer Transducers

“…Conducting polymer or solid state ion selective electrodes (ISEs) based potentiometric sensor falls in the asymmetric type because ionic dipolar layer is generated at the interface of liquid and solid phases [73]. Since the biochemical reaction between analyte and urease change pH due to the formation of ammonia and carbondioxide, it can be analysed using pH sensitive or H+ exchanger moieties through potentiometric mode of detection [74]. In addition, potentiometric sensor for detection of ammonia, and ammonium ion generated by enzymatic reaction, using ISE are being studied [75].…”