SWCNT nano-composite optical sensors for VOC and gas trace detection

The feasibility of exploiting novel chemo-sensitive coatings based on cadmium arachidate (CdA)/singlewalled carbon nanotube (SWCNT) composites for the development of high performance optical chemo-sensors has been experimentally investigated and proved. SWCNT nano-composite overlays have been transferred on the distal end of standard optical fibers by the Langmuir-Blodgett deposition technique in order to realize extrinsic low-finesse Fabry-Perot interferometers. A structural and morphological characterization of the fabricated optical probes has been carried out by scanning electron microscopy observations and Raman spectroscopy analysis. Reflectance measurements have been carried out to test the sensing performance of the proposed devices to volatile organic compound (VOC) and gas exposure. Also, VOC trace detection has been evaluated in different environments, such as air and water. Obtained results have also been compared in the same operating conditions to those obtained in the case of standard SWCNT overlays deposited by using the same deposition technique and optical transducers in order to outline the effect of the nano-composite matrix both on the material integration effectiveness and sensing performance. The results shown here demonstrate that the use of nano-composite coatings not only promotes a better adhesion of the sensitive overlay to the fiber Surface, thus improving the robustness of the chemo-optical sensors, but also significantly enhances their sensitivities from three to seven times with respect to the SWCNT overlay directly deposited on the fiber surface. Moreover, resolutions in the range 30-250 part per billion (ppb) and 0.6-1.5 part per million (ppm) have been estimated in case of air and water environments, respectively. (C) 2009 Elsevier B.V. All rights reserved.