Organophosphorus compound detection with a supported copper + cuprous oxide island film. 2. Alternating current studies and sensor performance

Detection of organophosphorous nerve agents using liquid crystals supported on chemically functionalized surfaces

“…Previous studies have reported on various principles and devices for the detection of organophosphorous nerve agents and simulants [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Surface acoustic wave (SAW) devices [8][9][10][11][12][13], piezoelectric quartz crystal microbalance (QCM) sensors [14,15], and fluorescence-based detection kits [16] have been shown to report simulant concentrations below 1 ppm, but often suffer from slow response times (up to 20 min).…”

“…Surface acoustic wave (SAW) devices [8][9][10][11][12][13], piezoelectric quartz crystal microbalance (QCM) sensors [14,15], and fluorescence-based detection kits [16] have been shown to report simulant concentrations below 1 ppm, but often suffer from slow response times (up to 20 min). Electrical resistivity methods [17][18][19][20] used to detect simulants are fast and sensitive (tens of ppb within 1 min) but are not typically highly specific. Colorimetric tubes [21] and enzyme-based [2] methods have been shown to detect organophosphorous agents at low concentrations (ppb range) with high specificity but require long sampling/analysis times and are not necessar- ily suitable as continuous monitoring systems.…”

Use of self-assembled monolayers, metal ions and smectic liquid crystals to detect organophosphonates

“…These schemes are generally based on the transduction of changes in the physical or chemical properties of a thin layer of semiconductor, polymer or enzyme solution after exposure to OPs. Examples of these techniques include surface acoustic wave (SAW) devices [4][5][6][7][8][9], electrical resistivity methods [10][11][12][13], quartz crystal microbalances (QCM) [14,15], enzyme-based detection kits [2], and fluorescence detection [16]. Traditional analytical techniques, such as ion mobility spectroscopy [17], Fourier transform infrared spectroscopy (FT-IR) [18,19], and gas chromatography (GC)-mass chromatography [20,21] have also been used for the detection of OPs.…”

“…We recently demonstrated that micrometer-thick films of the nematic LC, 4 -pentyl-4-biphenyl-carbonitrile (5CB), supported on nanostructured surfaces decorated with metal ions can be used to detect OPs [22]. The approach is based on four principles: (1) mesogens (molecules that form LC phases) at interfaces can communicate their orientations deep into the bulk of a liquid crystal (up to ∼100 m Table 1 Detection limits and response times of surface analytical and conventional analytical techniques for detection of organophosphonates Method Vapor sensitivity Response time SAW devices [4][5][6][7][8][9] DMMP-200-1000 ppbv 5-20 min Electrical resistivity [10][11][12][13] DMMP-44 ppbv 1 min QCM [14,15] DMMP-100 ppbv 5-20 min Enzyme-based kit (M256A1) [2] G agents-0.09 ppbv 15 min Fluorescent detection [16] DFP * -10 ppmv <30 s FT-IR [18,19] DMMP-1000 ppbv N/A GC-MS [20,21] Sarin-0.01-1 ppbv N/A Ion mobility spectrometry [17] Sarin-20 ppbv < 1 min Nematic liquid crystals [22] DMMP-20 ppbv 20 s * * Smectic liquid crystals DMMP-10 ppbv 20 s * * * Diisopropyl fluorophosphates. * * The response time is defined as the time at which a change in optical appearance of a LC film can be observed by the naked eye.…”

Interdigitated gate electrode field effect transistor for the selective detection of nitrogen dioxide and diisopropyl methylphosphonate

“…A significant portion of the organophosphorus contaminants contain either the phosphoryl or thiophosphoryl group. Since diisopropyl methylphosphonate (DIMP) is a phosphoryl-containing compound, has low toxicity, and has been used in prior detector development investigations, it was selected as a model compound in this research (2)(3)(4)(5)(6)(7)(8).…”