Preparation and electrochemical properties of nano-sized cryptomelane particles for the formation of potentiometric potassium ion sensors

The potentiometric response of 100-nm spherical K1.3Mn8O16 particles versus K+ ions has been studied in aqueous media using a polymeric technology. The stoichiometry of this material evolves in potassium nitrate solution towards K1.08Mn8O16. A stable and reversible response has been obtained with a sensitivity of 47 mV dec(-1) in the range from 8 x 10(-5) to 1 mol . L-1, and a rather good selectivity towards Li+, Na+, Mg2+ and Ca2+ (logK(K+/Xn+) approximate to -3). We assume that this potentiometric response is the result of the ability of K1.08Mn8O16 to specifically adsorb K+ ions.