This tutorial review surveys the optical properties of plasmonic nanoparticles studied by various single particle spectroscopy techniques. The surface plasmon resonance of metallic nanoparticles depends sensitively on the nanoparticle geometry and its environment, with even relatively minor deviations causing significant changes in the optical spectrum. Because for chemically prepared nanoparticles a distribution of their size and shape is inherent, ensemble spectra of such samples are inhomogeneously broadened, hiding the properties of the individual nanoparticles. The ability to measure one nanoparticle at a time using single particle spectroscopy can overcome this limitation. This review provides an overview of different steady-state single particle spectroscopy techniques that provide detailed insight into the spectral characteristics of plasmonic nanoparticles.
The response of living systems to
nanoparticles is thought to depend
on the protein corona, which forms shortly after exposure to physiological
fluids and which is linked to a wide array of pathophysiologies. A
mechanistic understanding of the dynamic interaction between proteins
and nanoparticles and thus the biological fate of nanoparticles and
associated proteins is, however, often missing mainly due to the inadequacies
in current ensemble experimental approaches. Through the application
of a variety of single molecule and single particle spectroscopic
techniques in combination with ensemble level characterization tools,
we identified different interaction pathways between gold nanorods
and bovine serum albumin depending on the protein concentration. Overall,
we found that local changes in protein concentration influence everything
from cancer cell uptake to nanoparticle stability and even protein
secondary structure. We envision that our findings and methods will
lead to strategies to control the associated pathophysiology of nanoparticle
exposure in vivo.
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