Fiber-Optic Sensor Technology and Combinatorial Chemistry

Abstract

Our recently introduced “Fiber-Optic Combinatorial Chemistry” technique combines combinatorial synthetic methods and optical fiber sensor technologies. Our one-dimensional combinatorial chemistry method allows for synthesis of large compound libraries in a linear format, for example in the cladding of optical fibers. Subjecting these libraries to assays that indicate positive identification of a library member by the binding of a fluorescent group, produces, in effect, an optical fiber sensor array. The location of a particular fluorescent region along the optical fiber can be determined through the optical time-of-flight technique, in which laser pulses propagating through the fiber core probe through their evanescent fields the fluorescent properties of the compounds located in the fiber cladding. It is a virtue of our combinatorial synthetic procedure that with the location of a compound on the fiber, its synthetic history is immediately known. We demonstrated that limitations on the spatial resolution of compounds along the fiber due to the excited state lifetimes of the fluorescent marker molecules can be overcome by the use of a second fiber - evanescently coupled to the first one - as an optical delay.

The existing claddings of optical fibers severely restrict the range of chemistries for the synthesis of combinatorial libraries. Therefore, in order to make our method more generally applicable, the existing fiber cladding has to be replaced by a porous material that can act as solid support for reactions and at the same time preserve the optical guiding conditions of the fiber. In this contribution we discuss the requirements for such a replacement cladding and evaluate the general suitability of a functionalized candidate material.