Scalable and bright: unlocking functional silicon quantum dots with near-unity internal quantum yield through...

Silicon quantum dots (SiQDs) are a promising class of functional nanomaterials combining non-toxicity, in comparison with their binary counterparts, and tunable optoelectronic properties. However, reaching their full potential in applications requires scalable fabrication and fast and simpler modification methods, enabling bonding of a broad variety of ligands and control over the photoluminescence efficiency. Here, we advance a versatile synthesis-modification methodology based on non-thermal plasma. In particular, we complement synthesis in non-thermal plasma allowing for extensive size tuning of SiQDs with unconventional air-free plasma-induced in-liquid reactions (PILRs) which enable rapid attachment of diverse ligands, using 3D-printed components for atmospheric control. Our approach yields brightly luminescent SiQDs with diameters starting from 2.4 nm with quantum yields of up to 20% and excellent colloidal stability across solvents of varying polarity. Spectrally resolved lifetime analysis uncovers a near-unity internal quantum yield for bright SiQDs and reveals how surface chemistry and aggregation govern dark-to-bright QD population ratios and photoluminescence quenching. Additionally, we simplify the well-established protocols of thermal hydrosilylation, showing that controlled-atmosphere sample collection without any further purification steps is a necessary condition for obtaining monodispersions with good optical properties. These results define a simple route to functionally engineered SiQDs, providing new insight into emission dynamics and establishing a strong foundation for their integration into advanced photonic, bioimaging, and energy-harvesting devices.