Explosives Detection by array of Si μ-cantilevers coated with titanosilicate type nanoporous materials

An array comprising 4 Si microcantilevers coated with nanoporous ETS-10 crystals sub-micrometric in size has been deployed as a multisensing platform for 2-nitrotoluene (an explosive related molecule) recognition. For such purposes, the adsorption properties of synthetic microporous ETS-10 titanosilicate type materials have been tailored by means of the Si/Ti ratio, and surface grafting with organic groups (amine, imidazol). Our general strategy for vapor detection of explosives involves the combination of Si based nanoporous solids as sensing materials and resonating Si cantilevers provided with self-heating elements as tiny microbalances (mass sensitivity factors ~18 Hz/ng). Particularly for this work, ETS-10 type titanosilicates with promoted basic properties (Si/Ti=4, -NH₂ anchored on the external surface) exhibit the higher affinity towards nitroaromatic derivatives as electron defficient molecules. A high remarkable hydrophilic character is shown by titanosilicates modified by covalent linkage with imidazole based organosilane (above 17% wt. water uptake at room temperature). Accounting from such versatile sorption behavior, the family of nanoporous ETS-10 crystals has been deployed by microdropping technique over the 8 Si-microcantilevers chip. By means of a portable low-power electronic interface capable of the simultaneous excitation and measurement of 4 sensor output signals, such multisensing platform has been successfully applied for 2-nitrotoluene detection at trace level.