Hydrothermal synthesis of MoS2 nanosheets for multiple wavelength optical sensing applications

In the present work, MoS2 nanosheets were synthesized by a hydrothermal method for optical sensing application. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman and UV-vis spectroscopy were carried out to characterize the synthesized MoS2 nanosheets. SEM and TEM images showed the morphology of ultrathin nanosheets of MoS2. Optical sensor of MoS2 nanosheets was fabricated and thoroughly studied using various laser excitation wavelengths (λex): 440 nm (indigo); 460 nm (blue); 550 nm (green); 570 nm (yellow); 635 nm (red) and 785 nm (infra-red). The excellent photoresponsivity was observed in the visible range and maximum was found to be 23.8 μA/W for λex: 635 nm (red illumination). The mechanism for photoresponse was proposed and correlated with the absorption spectroscopy. The response and recovery times for 635 nm were 2.5 and 3.2 s, respectively. The photoresponsive characteristics of MoS2 nanosheets were also explored as a function of optical power density.