Dual-SAM functionalization on integrated cantilevers for specific trace-explosive sensing and non-specific adsorption suppression

Two self-assembled monolayers (SAMs), 6-mercaptonicotinic acid (6-MNA) and hydrophobic heptadecafluorodecyltrimethoxysilane (FAS-17), are used to specifically modify the two surfaces of a piezoresistive SiO2 cantilever for functionalizations of both specific explosive-sensing improvement and non-specific molecular-adsorption suppression. With the dual-SAM modification technique, the on-chip-integrated ultra-sensitive microcantilever sensor behaves more sensitively and has quicker sensing properties to trace trinitrotoluene (TNT) than the previously reported cantilever functionalized with 4-MBA SAM, as well as being able to significantly suppress the cross-talk influence from environmental air humidity. Measurement results show that the high-performance sensor achieves a rapid, reversible and reproducible response to TNT vapour, with a detecting resolution of tens of ppt.