Abstract
This paper presents a new effective approach for the sensitive film deposition of surface acoustic wave (SAW) chemical sensors for detecting organophosphorus compounds such as O-ethyl-S-2-diisopropylaminoethyl methylphosphonothiolate (VX) containing sulfur at extremely low concentrations. To improve the adsorptive efficiency, a two-step technology is proposed for the sensitive film preparation on the SAW delay line utilizing gold electrodes. First, mono[6-deoxy-6-[(mercaptodecamethylene)thio]]-β-cyclodextrin is chosen as the sensitive material for VX detection, and a ∼2 nm-thick monolayer is formed on the SAW delay line by the binding of Au-S. This material is then analyzed by atomic force microscopy (AFM). Second, the VX molecule is used as the template for molecular imprinting. The template is then removed by washing the delay line with ethanol and distilled water, thereby producing the sensitive and selective material for VX detection. The performance of the developed SAW sensor is evaluated, and results show high sensitivity, low detection limit, and good linearity within the VX concentration of 0.15–5.8 mg/m3. The possible interactions between the film and VX are further discussed.
Highlights
Wohtjen [1] first reported the surface acoustic wave (SAW) method for gas sensing in 1979
The sensitivity of a SAW sensor depends on the amount of vapor adsorbed and the inherent ability of the SAW transducer to respond to physical changes in the membrane caused by vapor adsorption
Given the high mass-sensitivity of the SAW sensor, the thickness of the self-assembled, molecularly imprinted film was estimated by measuring the frequency shift as follows [22,23]: Δf = −1.26 × 106f02hρ where Δf (Hz) is the frequency shift between coated and uncoated SAW delay lines. f0 (MHz) is the operating frequency of the SAW sensor. h is the film thickness of the self-assembled, molecularly imprinted film, and ρ (g/cm3) is the density of the film material
Summary
Organophosphorus Compounds Using a Two-Step Self-Assembly and Molecular Imprinting Technology. Yong Pan 1,*, Liu Yang 1, Ning Mu 1, Shengyu Shao 1, Wen Wang 2, Xiao Xie 2 and Shitang He 2. Received: 19 February 2014; in revised form: 28 April 2014 / Accepted: 13 May 2014 /
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