Abstract
Silver nanoparticles (AgNPs) have a large number of technological
applications, such as photonic devices, molecular diagnostics,
antimicrobial coating and biomedical devices. These nanomaterials can be
synthesized using common fungi, which represents a green approach with
the additional advantage of biocompatibility. Here we applied
Tip-Enhanced Raman Spectroscopy (TERS) to obtain optical
characterization with resolution beyond the diffraction limit of AgNPs
produced by Rhodotorula glutinis and Rhodotorula mucilaginosa fungi.
Those fungi are conventional found in ordinary soil of north part of
Brazil, which biosynthesize core-shell AgNPs with protein-capping layer.
With TERS we were able to investigate with lateral resolution of few
nanometers the size and structure of the protein capping layer, how it
interacts with the Ag core, and how sensitive the system (core+ protein)
is to visible light illumination. Despite the complex data generated
which depends on the orientation of the protein, which is highly, it was
possible to detect the stretching of the S - S sulfur bridge in amino
acids. This stretch band is induced by a trans C-alpha - S conformation
acid on Rm-AgNPs, thus showing the potential of characterization of TERS
in nanobiosystems.
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