We report the plasma assisted synthesis of WS2 thin films and demonstrate their suitability for sensing applications. This was achieved by using a H2S plasma to sulphurise WO3 films at temperatures as low as 500 degrees C. This is a significant step towards semiconductor compatible growth of transition metal dichalcogenide (TMD) thin films without the need for highly elevated temperatures. We found that the electrical transport in thin films is highly sensitive to the presence of NH3. A sensitivity of 1.4 ppm NH3 in nitrogen at room temperature has been achieved, demonstrating the potential of 2D TMD films for sensing applications. (C) 2014 Elsevier B.V. All rights reserved.