Abstract
Herein we present an unusual phosphine-free method to fabricate water soluble CdSeS nanocrystals in cubic structure. In this method, glycerin was used as a stabilizing agent replacing tri-n-octylphosphine oxide (TOPO). Water solution of Na2SeO3 in polyethylene glycol was utilized as Se source. 3-Mercaptopropionic acid (MPA) provides S source. The phosphine-free Se and S sources were found to be highly reactive and suitable for the synthesis of CdSeS nanocrystals. XRD and HRTEM images confirm the formation of CdSeS nanocrystals in zinc blende structure. The absorption peaks on UV-vis spectra of as-prepared CdSeS nanocrystals are tunable from 330 nm to 440 nm, which blue shifts to shorter wavelength side in comparison with that of pure CdSe nanocrystals. The cubic CdSeS nanocrystals demonstrate narrow PL emissions spectra between 464 and 615 nm. Transmission electron microscopy images show the uniformity for the size distribution of the ternary QDs. Series water soluble CdSe1–xSx (x = 0∼1) nanocrystals have also been synthesized using Na2SeO3 and Na2S solution as the Se-S co-sources. Tunable band gap energies of CdSe1–xSx (x = 0∼1) nanocrystals upon chemical composition x have been achieved, the gap ranges from 290 nm to 558 nm.
Highlights
Over the past decades, scientists have discovered new species ranging between molecules and solids with unique size dependent physical and chemical properties [1,2,3]
The ternary QDs reported by other research groups were from hot-injection approaches using of Trin-octylphosphine (TOP)/tri-n-octylphosphine oxide (TOPO) or other long chain organic compounds [26,31] as the capping agent at high temperature
Structure determination CdSeS nanocrystals were produced through the reaction of
Summary
Scientists have discovered new species ranging between molecules and solids with unique size dependent physical and chemical properties [1,2,3]. To achieve the widespread use of QD-based devices and systems, it would be important to develop safe, economical, and environmentally friendly large-scale syntheses of high-quality QDs. For the synthesis of colloidal II-VI QDs, earlier efforts focused more on binary systems, such as CdSe and CdS QDs, and recent efforts more on ternary systems, such as CdTeSe [13,14,15], CdSeS [16,17,18], ZnCdSe, and ZnCdS QD alloys [19,20,21,22,23,24,25]. Alloyed CdSeS nanocrystals can be tuned readily to emit in the wavelength range of 480–540 nm, which is not achieved with binary CdSe or CdS QDs alone [4,27,28,29,30]. The ternary QDs reported by other research groups were from hot-injection approaches using of Trin-octylphosphine (TOP)/tri-n-octylphosphine oxide (TOPO) or other long chain organic compounds [26,31] as the capping agent at high temperature
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