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Jo et al. Soft Sci 2024;4:27 https://dx.doi.org/10.20517/ss.2024.19 Page 3 of 14

reaching an optimal ZnSe inner shell thickness.

EXPERIMENTAL
Synthesis of InP core QDs
Synthesis of green-emissive InP cores was conducted by mixing 0.15 mmol of indium (In) acetate,
0.125 mmol of Zn acetate, 0.5 mmol of palmitic acid, and 5 mL of 1-octadecene (ODE) in a 50 mL flask,
followed by degassing at 120 °C for 60 min. Next, 0.1 mmol of tris(trimethylsilyl)phosphine [(TMS) P]
3
diluted with 1 mL of trioctylphosphine (TOP) was injected into the mixture under flowing nitrogen. The
mixture was then heated to 240 °C, and the growth of InP cores proceeded at that temperature for 10 min.
The reaction was completed by cooling the InP core growth solution to room temperature and the resulting
InP cores were precipitated by adding excess ethanol and redispersed in 1 mL of toluene.

Double shelling of InP core with ZnSe/ZnS based on Zn oleate or Zn halides
For Zn oleate [Zn(OA) ]-based shelling, 5.0 mmol of Zn acetate, 3 mL of ODE, and 10 mmol of oleic acid
2
(OA), and 1 mL of InP core dispersion (in toluene) were loaded in a 50 mL flask. After the toluene was fully
removed through evacuation at 120 °C for 30 min, the mixture was heated to 160 °C. For ZnSe inner
shelling, Se-TOP solution [1.0 mmol of selenium (Se) dissolved in 1 mL of TOP] was rapidly introduced,
followed by the reaction at 300 °C for 60 min. For a sequential growth of ZnS outer shell, S-TOP solution
(0.5 mmol of S dissolved in 0.5 mL of TOP) was injected, followed by the reaction at 300 °C for 60 min. The
whole growth reaction was finalized by adding 0.75 mL of 1-octanethiol (OTT) and reacting at 230 °C for
60 min. After cooling to room temperature, as-synthesized QDs were collected with the addition of excess
ethanol, repeatedly purified with a combined solvent of hexane/ethanol using centrifugation, and finally
redispersed in hexane. In the case of Zn halides-based shelling, 5.0 mmol of Zn halide (ZnCl , ZnBr , or
2
2
ZnI ), 3 mL of ODE, and 3 mL of oleylamine (OLA), and 1 mL of InP core dispersion were loaded in a flask
2
and the following procedures were exactly the same as above.
Double shelling of InP core with ZnSe/ZnS based on Zn halide-derived hybrid approach
First, 5.0 mmol of Zn halide (ZnCl , ZnBr , or ZnI ), 3 mL of ODE, 3 mL of OLA, and 1 mL of InP core
2
2
2
dispersion were loaded in a flask, followed by the same procedures as above prior to ZnSe inner shelling.
For ZnSe inner shelling, Se-TOP solution (1.0 mmol of Se dissolved in 1 mL of TOP) and Zn stock solution
(2.8 mmol of Zn acetate dissolved in 0.88 mL of OA and 8 mL of ODE) were rapidly injected together,
followed by the reaction at 300 °C for 60 min. Then, ZnS outer shelling was conducted by injecting S-TOP
solution (0.5 mmol of S dissolved in 0.5 mL of TOP) and the Zn stock solution (0.7 mmol of Zn acetate
dissolved in 0.44 mL of OA and 2 mL of ODE) and reacting at 300 °C for 60 min. The subsequent
procedures were the same as above. The overall synthetic procedures are illustrated in Scheme 1.

Characterization
Absorption and PL spectra of InP QDs dispersed in hexane were measured by using ultraviolet (UV)-visible
spectroscopy (Shimadzu, UV-2450) and a 500 W Xe lamp-equipped spectrophotometer (PSI Co. Ltd., Darsa
Pro-5200), respectively. PL QY of QDs was assessed in an integrating hemisphere with an absolute PL QY
measurement system (Otsuka, QE-2000). PL decay profile of QDs in hexane dispersion was recorded using
the time-correlated single-photon counting method on a spectrophotometer (Edinburgh Instruments, FS5)
equipped with a picosecond pulsed laser diode (EPL-375). High-resolution transmission electron
microscopy (TEM) images of QDs were obtained with a JEM-2100F (JEOL Ltd). X-ray photoelectron
spectroscopic (XPS) (Thermo Scientific Inc., K-Alpha) analysis on QDs was performed to identify their
surface chemical composition. Powder X-ray diffraction (XRD) with Cu Ka radiation (Rigaku, Ultima IV)
31
was used to additionally provide information on size variation of a series of heterostructured InP QDs. P
solid-state nuclear magnetic resonance (NMR) experiments were recorded on a spectrometer (Bruker,