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Optimizing the light-emitting efficiency of silicon quantum dots (Si QDs) has been recently intensified by the demand of the practical use of Si QDs in a variety of fields such as optoelectronics, photovoltaics, and bioimaging. It is imperative that an understanding of the optimum light-emitting efficiency of Si QDs should be obtained to guide the design of the synthesis and processing of Si QDs. Here an investigation is presented on the characteristics of the photoluminescence (PL) from hydrosilylated Si QDs in a rather broad size region (≈2-10 nm), which enables an effective mass approximation model to be developed, which can very well describe the dependence of the PL energy on the QD size for Si QDs in the whole quantum-confinement regime, and demonstrates that an optimum PL quantum yield (QY) appears at a specific QD size for Si QDs. The optimum PL QY results from the interplay between quantum-confinement effect and surface effect. The current work has important implications for the surface engineering of Si QDs. To optimize the light-emission efficiency of Si QDs, the surface of Si QDs must be engineered to minimize the formation of defects such as dangling bonds at the QD surface and build an energy barrier that can effectively prevent carriers in Si QDs from tunneling out. [ABSTRACT FROM AUTHOR]

The dispersion of silicon quantum dots (Si QDs) in water has not been established as well as that in organic solvents. It is now demonstrated that the excellent dispersion of Si QDs in water with photoluminescence (PL) quantum yields (QYs) comparable to those for hydrophobic Si QDs can be realized by combining the processes of hydrosilylation and self-assembly. Hydrogen-passivated Si QDs are initially hydrosilylated with 1-dodecence. The toluene solution of the resulting dodecyl-passivated Si QDs is mixed with the water solution of the amphiphilic polymer of Pluronic F127 to form an emulsion. Dodecyl-passivated Si QDs are encapsulated in the micelles self-assembled from F127 in the emulsion. The size of the Si-QD-containing micelles may be tuned in the range from 10 to 100 nm. Although self-assembly in the emulsion causes the PL QY of Si QDs to decrease, after a few days of storage in ambient conditions, Si QDs encapsulated in the water-dispersible micelles exhibit recovered PL QYs of ≈24% at the PL wavelength of ≈680 nm. The intensity of the PL from Si QDs encapsulated in the water-dispersible micelles is >90% of the original value after 60 min ultraviolet illumination, indicating excellent photostability. [ABSTRACT FROM AUTHOR]

Excellent dispersion of silicon quantum dots (Si QDs) in water is realized by combining the processes of hydrosilylation and self‐assembly. As described by X. D. Pi and co‐workers on page 751, the size of self‐assembled Si QD micelles can be tuned from 10 to 100 nm. This image schematically shows red‐light‐emitting Si QDs contained in the water‐dispersible micelles under ultraviolet illumination. [ABSTRACT FROM AUTHOR]