I. Pellejero

Explosives detection using nanoporous coatings

Zeolite-coated cantilevers provided with internal heating elements have been developed and used for the selective detection of nitroderivates, in particular o-nitrotoluene as an example of an explosive-related molecule. In particular, Co exchanged commercial BEA zeolites have been deployed of rectangular Si cantilevers by microdropping technique. In particular, two different strategies have been demonstrated to increase the zeolite modified cantilevers performance: the sensing coating and the operating temperature. As a result, o-nitrotoluene LOD values below 1 ppm are attained at room temperature conditions; whereas the interference of toluene at concentrations below 1000 ppm is completely suppressed by heating the cantilever.

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

An array comprising four Si μ-cantilevers coated with nanoporous functionalized ETS-10 crystals sub-micrometric in size has been developed as a multisensing platform for explosives recognition in vapor phase. The detection capabilities of the proposed device have been tested for common taggants [such as 1-methyl-2-nitro-benzene (o-MNT)] and explosives (commercial detonation cord, a plastic tube filled with pentaerythritol tetranitrate (PETN); and C-4, a mixture of cyclotrimethylenetrinitramine (RDX), binders and plastifiers). The general strategy for the detection of explosives in vapor phase is based on the characteristic fingerprint each one produces as a result of the dissimilar chemical interactions between the ETS-10 coated μ-cantilevers and the target molecules emanating from the explosives and swept by ambient air. A portable lock-in amplifier has been implemented to exploit the truly benefits of the array in terms of portability, reduced size, and energy consumption. Such low-power electronic interface is capable of creating the excitation signal as well as obtaining the response values of four resonating μ-cantilevers simultaneously. The resulting sensing platform has successfully been applied for the o-MNT, PETN, and RDX detection at trace level.

Portable lock-in amplifier for microcantilever based sensor array. Application to explosives detection using Co-BEA type zeolites as sensing materials

Recent advances in microcantilever-based sensors have led to a significant increase in sensitivity, making them a competitive solution in highly demanding applications as explosives detection. However, these sensors face severe challenges related to: reliability, sensitivity, reproducibility and throughput; that have yet to be solved for commercial applications. This paper describes our efforts in this direction, particularly on the reproducible detection of nitroaromatic type explosives by means of parallelization combined with: i) nanoporous solids as sensing materials; and, ii) a portable low-power electronic readout interface capable of both excitation and measurement of the multisensing platform. The response of the sensor array, comprising 4 microcantilevers, due to presence of 2-nitrotoluene, a common explosive taggant, has been properly monitored. The obtained results with 4 identical Co-BEA coated Si microcantilevers underline the importance of a proper sensing material degassing on the sensor performance.

Zeolite based microconcentrators for volatile organic compounds sensing at trace-level: fabrication and performance

A novel 6-step microfabrication process is proposed in this work to prepare microfluidic devices with integrated zeolite layers. In particular, microfabricated preconcentrators designed for volatile organic compounds (VOC) sensing applications are fully described. The main novelty of this work is the integration of the pure siliceous MFI type zeolite (silicalite-1) polycrystalline layer, i.e. 4.0 ± 0.5 μm thick, as active phase, within the microfabrication process just before the anodic bonding step. Following this new procedure, Si microdevices with an excellent distribution of the adsorbent material, integrated resistive heaters and Pyrex caps have been obtained. Firstly, the microconcentrator performance has been assessed by means of the normal hexane breakthrough curves as a function of sampling and desorption flowrates, temperature and micropreconcentrator design. In a step further, the best preconcentrator device has been tested in combination with downstream Si based microcantilevers deployed as VOC detectors. Thus, a preliminar evaluation of the improvement on detection sensitivity by silicalite-1 based microconcentrators is presented.