Facile and in-situ spray deposition of SnO₂ – reduced graphene oxide heterostructure sensor devices

A facile and economic solution based technique is developed for the deposition of SnO₂—Reduced Graphene Oxide (RGO) heterostructure thin films. The single step deposition process leads to uniformly dispersed SnO₂ nanocrystallites on well exfoliated RGO sheets as confirmed by x-ray diffraction, Raman spectroscopy and transmission electron microscopy investigations. The response to NO₂ gas at room temperature (25 °C) is studied. The interface between n-type SnO₂ and p-type RGO flakes forms a hetrostrcuture barrier, which enhances the native sensitivity of pristine RGO towards toxic gases like NO₂. The technique allows controlling the density of SnO₂ nanoparticles (∼3 nm in size) attached to the RGO flakes and thereby enhancing the response of the heterostructure sensor device. The highest SnO₂ loading shows a 14 fold increase in response to 200 ppm of NO₂ and a response time as low as 5 s compared to that of ∼200 s for bare RGO films. (letter)