  In this work, the room temperature polar vapor sensing behavior of two
dimentional (2D) heterojunction Graphene-TiS3 materials and TiS3 nanoribbons is
investigated. TiS3 nanoribbons were synthesized via chemical vapor transport
(CVT) and their structure was investigated by scanning electron microscopy
(SEM), high resolution transmission electron microscopy (HRTEM), energy
dispersive X- ray spectroscopy (EDS), X-ray diffraction (XRD), Raman
spectroscopy and Fourier transform infrared spectroscopy (FT-IR) analysis. The
gas sensing performance of the TiS3 nanoribbons was assessed through the
observed changes in their electronic behavior. Sensing devices were fabricated
with gold contacts and with lithographically patterned graphene (Gr) electrodes
in a 2D heterojunction Gr-TiS3-Gr architecture.. It is observed that the gold
contacted TiS3 device has a rather linear I-V behavior while the Gr-TiS3-Gr
heterojunction forms a contact with a higher Schottky barrier (250 meV). I-V
responses of the sensors were recorded at room temperature with a relative
humidity of 55% and for different ethanol vapor concentrations (varying from 2
to 20 ppm). I-V plots indicated an increase in the resistance of Gr-TiS3-Gr by
the adsorption of water and ethanol molecules with relatively high sensing
response (~3353% at 2 ppm). Our results reveal that selective and stable
responses to a low concentration of ethanol vapor (2 ppm) can be achieved at
room temperature with transient response and recovery times of around 6 s and
40 s, respectively. Our proposed design demonstrate a new approach for
selective molecular recognition using polar interactions between analyte vapors
and heterojunctions of 2D-materials.
