Raman Signal
Enhancement Dependence on the Gel Strength
of Ag/Hydrogels Used as SERS Substrates
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Abstract
A series
of hydrogel samples composed of Ag nanoparticles dispersed
in carrageenan gels have been prepared and used in SERS studies. These
studies demonstrate the dependence of the enhancement of the SERS
signal on the strength of the Ag/polysaccharide hydrogel. 2,2′-Dithiodipyridine
was used as the analyte probe. Several strategies were employed in
order to vary the gel strength. These include the increase of the
polysaccharide content in the gel, the addition of KCl as cross-linker,
and the variation of the type of carrageenan (κ, ι, λ)
network. An increase in the gel strength originates an increase in
the SERS enhancement observed. The results have been interpreted considering
hot spots increase due to the formation of Ag particles nanojunctions
as the biopolymer matrix tends to rearrange into stronger gels. This
is the first report showing that there is a direct correlation between
the gel strength of a hydrogel composite used as substrate and its
analytical SERS sensitivity