In this article, boundary element method simulations are used to optimise the geometry of silver and gold nanocone probes to maximise the localised electric field enhancement and tune the near‐field resonance wavelength. These objectives are expected to maximise the sensitivity of tip‐enhanced Raman microscopes. Similar studies have used limited parameter sets or used a performance metric other than localised electric field enhancement. In this article, the optical responses for a range of nanocone geometries are simulated for excitation wavelengths ranging from 400 to 1000 nm. Performance is evaluated by measuring the electric field enhancement at the sample surface with a resonant illumination wavelength. These results are then used to determine empirical models and derive optimal nanocone geometries for a particular illumination wavelength and tip material. This article concludes that gold nanocones are expected to provide similar performance to silver nanocones at red and near‐infrared wavelengths, which is consistent with other results in the literature. In this article, 633 nm is determined to be the shortest usable illumination wavelength for gold nanocones. Below this limit, silver nanocones will provide superior enhancement. The use of gold nanocone probes is expected to dramatically improve probe lifetime, which is currently measured in hours for silver coated probes. Furthermore, the elimination of passivation coatings is expected to enable smaller probe radii and improved topographical resolution.
Nanoceria has evolved as one of the promising nanomaterials due to its unique enzyme-like properties, including excellent oxidase mimetic activity, which significantly increases in the presence of fluoride ions. However,...
This Article describes a method for
the characterization of the
imaging performance of tip-enhanced Raman spectroscopy probes. The
proposed method identifies single-walled carbon nanotubes that are
suitable as one-dimensional Raman scattering objects by using atomic
force microscope maps and exciting the radial breathing mode using
785 nm illumination. High-resolution cross sections of the nanotubes
are collected, and the point spread functions are calculated along
with the optical contrast and spot diameter. The method is used to
characterize several probes, which results in a set of imaging recommendations
and a summary of limitations for each probe. Elemental analysis and
boundary element simulations are used to explain the formation of
multiple peaks in the point spread functions as a consequence of random
grain formation on the probe surface.
Cerium oxide nanoparticles (CeNPs) depict excellent in vitro and in vivo antioxidant properties, determined by the redox switching of surface cerium ions between its two oxidation states (Ce3+ and Ce4+)....
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