Biomedical Engineering Reference
In-Depth Information
Au 29 (SG) 20 , Au 33 (SG) 22 , Au 39 (SG) 24 ] revealed that they are molecules
in nature and that their optical and photophysical properties are
highly dependent on the core sizes and the number of GSH ligands. 60
The optical band gaps of these GS-protected Au NCs and other Au
NCs (Au 140 , Au 38 , Au 11 ) all increase upon decreasing their size. These
blue shifts in emission maxima upon reducing the NCs' sizes are due
to increased energy gaps between the quantized levels (interband or
intraband transitions) ascribed to the smaller core sizes as well as
to the higher coverage of thiolates or other capping molecules (e.g.,
phosphine). 60 The luminescence properties of the GS-protected Au
NCs are quite different from those for the Au(I)-GS complexes. In
contrast, many luminescent Au NCs, such as those listed in Table 9.1,
do not exhibit a size-dependence of their optical band gaps.
Figure 9.3 (A) Au MPCs with different core sizes and monolayers.
C6, C12, PhC2, PEG, and PPh 3 represent hexanethiolate,
dodecanethiolate, phenylethanethiol, poly(ethylene glycol)
(MW 350) thiolate, and triphenylphosphine, respectively.
Asterisks indicate artifacts from second- and third-order
excitation peaks (800 and 1200 nm); the dip at 1165 nm is
partly due to solvent/ligand absorption. (B) (a) Luminescence
intensity (at 1000 nm) vs. number of TMA ligands exchanged
onto Au 140 (C6) 53 MPCs. (b) Luminescence at 690 nm of
products of core metal galvanic exchange reactions of Ag
tiopronin MPCs (average core diameter: 1.6 nm) with Au(I)[ p -
SCH 2 (C 6 H 4 )C(CH 3 ) 3 ]. Reprinted with permission from Ref. 23.
See also Color Insert.
Figure 9.3A reveals the visible-NIR luminescence of ive different
Au NCs (all <2 nm in diameter) that have Au core atoms (Au 11 -Au 201 )
 
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