Surface-Enhanced Raman Scattering Based on Noble Metal Nanoparticles - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 260

pH of the colloidal sol and the molecular adsorbate concentration
during the encapsulation process. Formation of nanoaggregates
in the colloidal Au sol was demonstrated by a change in color and in
extinction response as shown in Fig. 11.6A. Monodispersed 12 nm Au
NPs exhibit an absorption maximum at 520 nm prior to the addition
of Raman reporter molecule, R6G. The extinction response of NAEB
in Fig. 11.6A showed an additional peak at 640 nm indicative of
the nanoaggregates structure. A transmission electron microscopy
(TEM) image of the NAEB (Fig. 11.6C) shows that a majority of the
NAEB are made of 2-5 NPs encapsulated in a dense silica shell and
have a typical dimension of ~150 nm. A typical SERS spectrum of
R6G-NAEB is shown in Fig. 11.6B.

(A) A B

A

AB

(B) S. aureus

+

A

AB

AAB

AB C

A

Figure 11.5 (A) Schematic depiction of NAEB fabrication; (B) Targeted
detection of S. aureus by NAEB conjugated to S. aureus speciic
sdAb. Reproduced from Ref. 56 with permission.

(A)

(B) (C)

A

AB

( ) ( )

Figure 11.6 (A) Bulk extinction spectra of 12 nm colloidal Au sol (dash)
and R6G-NAEB; (B) SERS spectrum of R6G-NAEB; (C) TEM
image of NAEB. Reproduced from Ref. 56 with permission.

To achieve target-speciic detection of S. aureus , a selected
antibody must exhibit both good binding afinity and speciicity to