Figure 3.

Spectral shifts affect the absorption coefficient. (a) Absorption spectra of silver-coated AuNRs with increasing shell thickness (right to left). Increasing shell thickness causes a blue-shift in the absorption spectra due to a reduction in the AuNR aspect ratio. The μ_a at 680 nm reduces because of the blue-shift. (b) Selective etching of the silver shell with an increasing concentration of reactive oxygen species (H₂O₂) restores the AuNR absorption and μ_a at 680 nm. (c) PA intensity at 680 nm increases as a function of H₂O₂ concentration as μ_a increases in (b). (d) In vivo detection of oxidative stress as a function of time. Iodide-doped silver-coated particles are more sensitive to oxidative stress and show a 70% increase in PA intensity over 90 min (680 nm). Adapted with permission from ref 13. Copyright 2020 The Royal Society of Chemistry.