Studies on ferrocene immobilized sol-gel glasses and its application in the construction of a novel solid-state ion sensor

Two new sol-gel glass systems with immobilized ferrocene are developed usin g two different types of sol-gel precursors. System (1) is developed using ferrocene carboxaldehyde and a mixture of two silanes (3-aminopropyltrietho xy silane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxy silane). System (2) is developed using ferrocene monocarboxylic acid and a mixture of 3-glycidoxy propyltrimethoxysilane and trimethoxysilane. The surfaces of the sol-gel gl asses are analyzed based on scanning electron microscopy (SEM). The electro chemistry of ferrocene in system 1 and system 2 is characterized based on c yclic voltammetry. System 1 shows capacitive CV at slow scan rate whereas s ystem 2 shows good reversible electrochemistry of ferrocene. The potentiome tric response of the ferrocene immobilized sol-gel glass (system 1) is stud ied in 10 mM Tris-HCl buffer pH 7.0. A reproducible potential difference of system 1 to the order of -30 mV is recorded for 2 months with respect to a double junction SCE reference electrode. An ion sensing membrane is assemb led over the ferrocene immobilized sol-gel glass using plasticized PVC matr ix membrane containing dibenzo-18-crown-6. A typical potentiometric respons e of the ion sensor is reported. The response of the ion-sensor shows bette r response time, high reproducibility and relatively better slope for potas sium analysis as compared to earlier reported solid-state K+ ion-sensor bas ed on dibenzo-18-crown-6 neutral carrier. The reproducibility, detection li mit and relative response of the ion sensor to Na+ and NH4+ ions are report ed.