Iron Oxide–Gold Composite Nanoparticles and Nano-Gap Junctions …
269
Fig. 10 Representative Raman spectra of 4-mercaptophenol. (Color figure online)
activities of gold nanospheres were investigated initially using 10 mM nominal 4mercaptophenol in aqueous solution as the reporter analyte of interest. All spectra
collected show the characteristic peaks of the 4-mercaptophenol spectrum. The peak
at ≈ 1080–1100 cm
−1 corresponding to the ring-breathing mode ν1 was used to
monitor differences between the control 4-mercaptophenol and gold nanospheres
engineered with the same concentration of 10 mM nominal 4-mercaptophenol. As
expected, when gold nanospheres were used, an enhancement Raman response was
collected. However, the surface-enhanced Raman spectroscopy response generated
on gold nanospheres was minimally enhanced. An ≈ 10% larger response was
observed for gold nanospheres in comparison with the control 4-mercaptophenol
(Fig. 11b). While it is not clear if a monolayer analyte was created on the surface
of gold nanoparticles during the surface functionalizations, the results are encouraging and may suggest that in an optimized system, one could generate positive
enhancement responses.
In order to explore the influence of “hot-spot” junctions and nano-gaps on the
surface Raman scattering experiments, gold–iron oxide composites were engineered
with the same model analyte. The surface-enhanced Raman scattering experiments
collected on the composite nanoparticles are shown in Fig. 12. There are several key
findings generated from these studies.
The most important conclusion from these studies is that the gold–iron oxide
nanocomposite structures provide a three-time magnitude Raman enhancement
response in comparison with the gold nanospheres. It is assumed that a combination
of effects is responsible for these positive results.
For example, the composite structures form aggregated architectures that promote
formation of “hot-spot” junctions. This is attributed to the use of a key component
269
Fig. 10 Representative Raman spectra of 4-mercaptophenol. (Color figure online)
activities of gold nanospheres were investigated initially using 10 mM nominal 4mercaptophenol in aqueous solution as the reporter analyte of interest. All spectra
collected show the characteristic peaks of the 4-mercaptophenol spectrum. The peak
at ≈ 1080–1100 cm
−1 corresponding to the ring-breathing mode ν1 was used to
monitor differences between the control 4-mercaptophenol and gold nanospheres
engineered with the same concentration of 10 mM nominal 4-mercaptophenol. As
expected, when gold nanospheres were used, an enhancement Raman response was
collected. However, the surface-enhanced Raman spectroscopy response generated
on gold nanospheres was minimally enhanced. An ≈ 10% larger response was
observed for gold nanospheres in comparison with the control 4-mercaptophenol
(Fig. 11b). While it is not clear if a monolayer analyte was created on the surface
of gold nanoparticles during the surface functionalizations, the results are encouraging and may suggest that in an optimized system, one could generate positive
enhancement responses.
In order to explore the influence of “hot-spot” junctions and nano-gaps on the
surface Raman scattering experiments, gold–iron oxide composites were engineered
with the same model analyte. The surface-enhanced Raman scattering experiments
collected on the composite nanoparticles are shown in Fig. 12. There are several key
findings generated from these studies.
The most important conclusion from these studies is that the gold–iron oxide
nanocomposite structures provide a three-time magnitude Raman enhancement
response in comparison with the gold nanospheres. It is assumed that a combination
of effects is responsible for these positive results.
For example, the composite structures form aggregated architectures that promote
formation of “hot-spot” junctions. This is attributed to the use of a key component