Remote Detection of HCN, HF, and Nerve Agent Vapors Based on Self-Referencing, Dye-Impregnated Porous Silicon Photonic Crystals

Abstract

A one-dimensional photonic crystal is prepared from porous silicon (pSi) and impregnated with a chemically specific colorimetric indicator dye to provide a self-referenced vapor sensor for the selective detection of hydrogen fluoride (HF), hydrogen cyanide (HCN), and the chemical nerve agent diisopropyl fluorophosphate (DFP). The photonic crystal is prepared with two stop bands: one that coincides with the optical absorbance of the relevant activated indicator dye and the other in a spectrally “clear” region, to provide a reference. The inner pore walls of the pSi sample are then modified with octadecylsilane to provide a hydrophobic interior, and the indicator dye of interest is then loaded into the mesoporous matrix. Remote analyte detection is achieved by measurement of the intensity ratio of the two stop bands in the white light reflectance spectrum, which provides a means to reliably detect colorimetric changes in the indicator dye. Indicator dyes were chosen for their specificity for the relevant agents: rhodamine-imidazole (RDI) for HF and DFP, and monocyanocobinamide (MCbi) for HCN. The ratiometric readout allows detection of HF and HCN at concentrations (14 and 5 ppm, respectively) that are below their respective IDLH (immediately dangerous to life and health) concentrations (30 ppm for HF; 50 ppm for HCN); detection of DFP at a concentration of 114 ppb is also demonstrated. The approach is insensitive to potential interferents such as ammonia, hydrogen chloride, octane, and the 43-component mixture of VOCs known as EPA TO-14A, and to variations in relative humidity (20–80% RH). Detection of HF and HCN spiked into the complex mixture EPA TO-14A is demonstrated. The approach provides a general means to construct robust remote detection systems for chemical agents.

Photonic crystal gas sensors based on metal–organic frameworks and polymers

“…2(II), other researchers constructed PCs by staining porous silicon with a chemically specic colorimetric indicator or permeating polystyrene with a reference channel for the detection of ammonia and the nerve agent diisopropyl uorophosphate (DFP). [30][31][32] Spin coating, dip coating or layer-by-layer deposition (Fig. 2(III)) is a process driven by centrifugal or capillary forces during solvent evaporation, which is very suitable for 1D DBR structures.…”

“…2(II), other researchers constructed PCs by staining porous silicon with a chemically specific colorimetric indicator or permeating polystyrene with a reference channel for the detection of ammonia and the nerve agent diisopropyl fluorophosphate (DFP). 30–32…”

Assembly of Nanometer-Sized Hollow Sphere Colloidal Crystals for Applications as Tunable Photonic Materials

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Three-Dimensional Photonic Crystals Based on Porous Anodic Aluminum Oxide

“…In turn, the PC design based on the periodic array of holes in a dielectric found success in light manipulation − and sensing − that stimulated interest to scalable methods of creating this type of PC. It makes ordered porous systems, in which the modulation of the dielectric constant is achieved by the permittivity difference between the matrix and the medium inside the pores (usually air), favorable for the preparation of PCs.…”