[en] In this doctoral thesis, we use a helium ion microscope (HIM) to place individual point defects in MoS${}_2$ and examine their physical properties for future applications in quantum technology and catalysis. We use scanning probe microscopy to study the interactions of helium ions with MoS${}_2$ and identify several different defect types. Subsequently, we study the optical properties of these defects. Furthermore, we investigate the catalytic properties of pristine and helium ion irradiated MoS${}_2$ for applications in solar water splitting devices.