Table 3.

ToF-SIMS negative secondary ion fragments from CdSe/CdS/ZnS QDs. The observed fragments are consistent with the QD elemental compositions. The Cd and Se fragments are associated with the CdSe QD core; the CdSx fragments are associated with the CdS intermediate layer; the phosphrous containing fragments are associated with ODPA and TOPO ligands.

Negative secondary ion mass	Molecular Species (−1)	Assignment		Relative Intensity %
25.007	C2H	Most intense peak		100.00
31.972	S	CdSe/CdS/ZnS		11.8
63.947	S2			4.6
79.923	Se			3.4
145.884	CdS			4.5
159.842	Se2			0.6
177.863	CdS2			3.8
191.814	CdSe			0.7
209.846	CdS3			1.6
45.997	CH3P	Organic Ligands	TOPO/ODPA	8.5
61.993	CH3PO			21.4
74.995	C2H4PO			2.1
237.087	C16H14P			1.7
255.267	C16H32P			3.1
62.964	PO2		ODPA	14.6
78.972	PO3			42.9
79.963	PO3H			17.4
80.973	PH2O3			4.8
90.994	C2H4PO2			0.4
93.980	CH3PO3			0.6
106.983	C2H4PO3			0.5
333.249	C18H37PO3H (M−H)			0.9
334.265	C18H37PO3H2			0.6
348.2623	C18H37PO4 (M−2H+O)			3.7
349.260	C18H37PO4 H (M−H+O)			1.1
281.288	C18H33O2 (M−4H)		Stearate23	7.0
283.301	C18H35O2 (M−2H)			4.2
284.270	C18H36O2 (M−H)			0.9
285.265	C18H37O2			0.7