Enhanced dimethyl methylphosphonate (DMMP) detection sensitivity by lead magnesium niobate-lead titanate/copper piezoelectric microcantilever sensors via Young's modulus change
We have examined the detection of dimethyl methylphosphonate (DMMP) using lead magnesium niobate-lead titanate (PMN-PT) piezoelectric microcantilever sensor (PEMS) coated with various planar and particulate receptor coatings. We showed that a two-order-of-magnitude enhancement in the flexural-mode resonance frequency shift, Îf, in DMMP detection that was not accountable for by mass loading alone could be achieved by using a planar Cu2+ adsorbed 11-Mercaptoundecanoic Acid (MUA/Cu2+) or planar 3-mercaptopropyltrimethoxysilane (MPS) coated PEMS. We also showed that the enhancement of Îf of PEMS was a result of the Young's modulus change in the PMN-PT layer induced by the surface stress generated by the binding of DMMP on a continuous receptor coating. Furthermore, the Young's modulus-change enhanced Îf in PEMS with a planar receptor coating was shown to be inversely proportional to the product of the average Young's modulus and thickness of the PEMS and independent of the PEMS lateral dimension. We also showed that with an array of three PEMS, one uncoated, one coated with planar MUA/Cu2+ and the other with planar MPS, the detection Îf pattern for DMMP was distinctively different from those of acetone and ammonia.