Lifetime-based fiber-optic water sensor using a luminescent complex in a lithium-treated Nafion (TM) membrane

A lifetime-based fiber-optic sensor that can be used to measure water conte nt in organic solvents and relative humidity of air is described. The senso r is based on the luminescence lifetime quenching of ruthenium(II)bisphenan throlinedipyridophenazine (Rudppz) immobilized in a Nafion (TM) membrane th at is mechanically attached to the distal tip of an optical fiber. Treatmen t of the Nation (TM) membrane with lithium hydroxide prior to doping with R udppz provides a stable sensor response with intense, long-lived luminescen ce. The response of the sensor to relative humidity was characterized using dry air, room air, and water saturated air. The sensor is useful for measu ring the water content of organic solvents below 4% (v/v) and the detection limit is determined to be 0.06, 0.07, and 0.006% (v/v) in DMSO, ethanol, a nd acetonitrile, respectively. It is being developed for the purpose of mea suring water concentration gradients across Naflon (TM) membranes. (C) 2001 Elsevier Science B.V. All rights reserved.