Time-resolved photoluminescence decay characteristics of bovine serum albumin-conjugated semiconductor nanocrystallites

Figures & data

Figure 1. A typical flow chart diagram for obtaining (a) unconjugate CdS- and CdZnS-NCs and (b) thiol-capped and BSA-conjugated CdS NCs.

Figure 2. Optical absorption spectra (OAS) of (a) CdS, (b) CdZnS and (c) Cd_0.25Zn_0.75S-NCs systems. Numbers (1), (2) and (3) represent untreated, thiol-stabilised and BSA-NCs conjugates, respectively.

Figure 3. High resolution electron microscopy images of (a) CdS-NCs and (b) CdS-BSA conjugates. A magnified view of isolated, spherical CdS-NCs (∼2 nm) is shown in the figure inset–(a).

Figure 4. Steady-state PL spectra of (a) CdS, (b) CdZnS and (c) Cd_0.25Zn_0.75S-NCs systems. Figure insets represent spectral responses in the selective wavelength range (400–460 nm) highlighting prominent peak positions. Symbols (−), (▴) and (□) correspond to untreated, thiol-stabilised and BSA-NCs conjugates, respectively.

Figure 5. Schematic view of the radiative emission process in NCs.

Table 1. PL-decay constants for various Cd_{1− x} Zn _x S-NCs and BSA conjugates.

Sl.	Sample Cd1− x Zn x S	x (%)	τ f (ns)	τ s (ns)	A f (%)	A s (%)	τ s /τ f	τ (ns)
1	CdS-NCs	0	24.13	24.13	50	50	1	12.06
2	CdS-NCs-BSA		2.07	18.84	80.9	19.1	9.1	1.87
3	CdZnS-NCs	50	21.25	21.25	50	50	1	10.62
4	CdZnS-NCs-BSA		2.21	20.07	78.8	21.2	9.08	1.99
5	Cd0.25Zn0.75S-NCs	75	17.54	17.54	50	50	1	8.77
6	Cd0.25Zn0.75S-NCs-BSA		2.34	20.31	74.3	25.7	8.68	2.09

Figure 6. Time-resolved photoluminescence spectra (λ _ex = 375 nm; λ _em = 430 nm) of (a) CdS, (b) CdZnS and (c) Cd_0.25Zn_0.75S-NCs systems.

Figure 7. Decay time constant vs. stoichiometry (% x, Zn) for Cd_{1− x} Zn _x S-NCs and BSA conjugates.