Short Wavelength Inner Filter Technique (SWIFT) in Designing Reactive Fluorescent Molecular Probes

Here, we present a conceptually novel and experimentally straightforward technique for selective analyte detection that uses a combination of commercial fluorophores and simple chemicals. The technique utilizes the well-known inner filter effect (IFE); however, the fluorophore's excitation is performed at wavelengths significantly shorter than its absorption maximum. In the presence of the analyte, the "filter" appears or disappears at the excitation wavelength resulting in the fluorescence turning OFF or ON, respectively. Unlike common probes, our technique allows real-time monitoring of a fluorophore's stability as well as its recycling. We further demonstrate the applicability of this technique in continuing analyte detection as well as vapor analysis.