Laser‐Driven Synthesis of Bright and Stable CdSeZnS Alloy Nanocrystals in Organic Media

Femtosecond laser in situ generation of photoluminescent nanocrystals enables rapid fabrication and tunable fluorescence, but the resulting crystals often exhibit poor quality and low quantum efficiency. Additionally, the high pulse energy required tends to induce hollow structures, hindering the formation of high‐quality fluorescent data points. In this study, bright and stable CdSeZnS nanocrystals were directly synthesized in situ within an organic medium at room temperature using a femtosecond laser. A record‐high equivalent fluorescence quantum yield of 36.4% was achieved. This is the highest efficiency ever attained for this technique. Adjusting the laser parameters allows tuning of the emission wavelength of the nanocrystals from green to red, enabling the successful realization of both 2‐ and 3D patterning. The formation mechanism of laser‐induced nanocrystals and their alloying process were systematically investigated. The key challenge of hollow structure formation during laser‐induced crystal growth was successfully addressed by employing a strategy of low‐power nucleation and subsequently heating growth. These laser‐generated nanocrystals demonstrate flexibility and stability, retaining fluorescence after 7 days of solution storage. Furthermore, patterning can be achieved with ultra‐low pulse energy (as low as 5 nJ) and submicron resolution (minimum dot spacing of 700 nm). This work highlights the significant potential of laser‐synthesized alloy nanocrystals for advanced photonics applications, including optical storage and anti‐counterfeiting