Near Infrared sensor based on Graphene Nanomaterials on Flexible Substrates

Abstract:
In this paper we introduce carbon nanotubes (CNTs) and graphene oxide (GO) hybrid nanocomposites based optical sensors. The optoelectronic responsivity was investigated in the near infrared NIR region. The sensors were prepared out of homogeneous dispersions of CNT and GO in aqueous solutions and they were then deposited on thin flexible substrate by drop casting. The optical sensitivity was measured using a laser diode with a wave length of 980 nm in air and at room temperature. Furthermore, UV-Vis-NIR measurements and scanning electron microscopy images are also investigated aiming to check the morphology and the quality of the dispersions. The films made by aqueous solution of graphene oxide and single walled carbon nanotubes (SWNT) showed a change in resistance up to 4% by laser illumination of 0.5 mW/mm². Furthermore, the films made by physical mixing of CNT and graphene oxide were found more sensitive to IR radiation than those based on only CNT or GO materials. This is due to the flat photoresponse in wide range of the spectrum and enhanced absorption. A sensor made by SWNT/GO composite showed resistance changes of 37% under 1.5 mW/mm² of IR illumination at room temperature and the responsivity can reach up to 40 mA/W at laser illumination of 0.5mW/mm². In addition, an improvement was already achieved by mixing both species in hybrid nanocomposites although further improvement is still also foreseen. Owing to their unique band structure and electronic properties, absorption in a wide range of wavelengths and enhanced optical properties of GO/SWNT nanocomposites make them suitable for optical sensors.