One-pot synthesis of phosphine-free indium selenide (InSe) QDs and their structural characterization for LPG and humidity sensing

In the present manuscript, we reported the facile, low cost, and phosphine-free synthesis of indium selenide (InSe) quantum dots (QDs) via one-pot synthesis route. The particle size analysis revealed the average particle size of InSe QDs as ~ 13 nm. Optical properties of InSe QDs were investigated using photoluminescence (PL) and UV absorption analysis. InSe QDs exhibited an excitation wavelength of 370 nm with two major absorption peaks at ~ 405 and 432 nm. Characteristic energy band gap of the QD was evaluated as 2.2 eV from Tauc plot. Time-resolved photoluminescence (TRPL) witnessed the 6.41 ns recombination time for the InSe QDs. Formation of uniform spherical particle with size ranging from 2 to 4 nm is evident from transmission electron microscopy (TEM). XRD pattern of as-synthesized InSe QD was found in the close agreement with standard tetragonal chalcopyrite structure. Finally, the sensing film was fabricated using a spin-coating method and is further employed as a LPG gas and humidity sensor. Sensor response for the LPG gas was found as 4.41 with response and recovery times calculated as 7.5 and 6.3 s, whereas for the humidity the average sensitivity of the sensing film is calculated as 8.89 MΩ/% RH with response and recovery times 5.3 and 13.2 s.