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

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 modified 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 µL of urease solution (40 mg /mL) is allowed to assemble overnight at 4 °C over neutral poly (3-cyclohexyl thiophene) modified electrode; b) an organically modified sol-gel layer is allowed to form over the urease adsorbed polymer modified 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.