<p>Lead halide perovskite quantum dots (QDs) have emerged as a promising material in various optoelectric devices. However, their fabrication and direct patterning remain challenging due to the intrinsic susceptibility of perovskite QDs. Thus, a chemically mild and facile patterning method is required for advancement in QD applications. Herein, we developed a laser-assisted ligand engineering method that enables facile and precise, non-destructive surface modification of QDs. By employing a mid-IR CO₂ laser, surface ligands were selectively removed, resulting in precise modulation of optical and chemical properties without disrupting the nanostructure. This solvent- and mask-free patterning technique offers rapid processing and facile spatial control compared with conventional chemical approaches. We demonstrated the application of this technique in the fabrication of a QD-based fluorescent sensing platform. The laser-assisted ligand engineering enabled CsPbBr₃ perovskite-embedded nanofibers to exhibit a dual-mode fluorescent response to gaseous ammonia, with a detection limit of 0.152 ppm for fluorescence quenching and 0.6 ppm for enhancement. This approach enables direct patterning of visually responsive sensors, highlighting their potential for integrated detection and display.</p> Graphical Abstract <p></p>