Abstract We report a highly sensitive optical sensor based on free-standing thin films derived from multi-walled carbon nanotubes (MWCNTs)-Alumina nanocomposite by Gel-cast technique. The sensing principle involves the change in the resistance/conductance of the fabricated nanocomposite film on interaction with the optical stimulus. The performance of the sensor strongly depends − on loading and dispersion of MWCNTs in Alumina host matrix; wavelength; and power density of the laser beam. The optimized loading of CNTs to achieve maximum sensitivity was 1.5wt%. The sensitivity of the sensor shows linear relationship with power density of the laser beam and found to be highly sensitive in Vis-NIR region. The maximum sensitivity of the sensor is found to be 13.2% at 635nm wavelength, 3.5mW/mm2 power density of laser beam and at 1.5wt% MWCNTs loading in Alumina host matrix. At this loading, the response time and recovery time of the sensor are found to be 1.7s and 2.1s respectively. The additional advantage of the present sensor is that it is facile and cost-effective method to fabricate high performance optical sensors. Highlights A promising facile and economic technique to develop MWCNTs/Alumina composite film. Optical sensors prepared from free-standing films for varying MWCNTs contents. FESEM analysis corroborates homogeneous dispersal of MWCNTs in host matrix. Fast response, high sensitivity andexcellent repeatability in Vis-NIR region. The technique holds potential for commercial scale production.
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