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Identification and quantification of organic vapors by time-resolved diffusion in stacked mesoporous photonic crystals.

Microsensors for gas-phase analytes are fundamentally limited by their inability to discriminate between analytes. While cross-reactive arrays consisting of multiple different sensor elements provide one means to identify individual analytes, these "artificial nose" devices rely on complicated data processing algorithms and they generally suffer from significant zero-point drift. Herein, we present a single component optical sensor that is capable of identifying chemical compounds at parts-per-million concentrations. The device consists of a stack of three mesoporous silicon-based photonic crystals; a porous "drift tube" is sandwiched between two optically responsive layers. The drift layer temporally separates the optical responses of the other layers, and this difference is shown to be characteristic of the analyte.