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. Author manuscript; available in PMC: 2021 Aug 25.
Published in final edited form as: ACS Nano. 2020 Aug 12;14(8):9408–9422. doi: 10.1021/acsnano.0c05215

Figure 2.

Figure 2.

Plasmonic coupling causing local-field enhancement and spectral shifts. (a) Electric-field intensity distribution on top surface and (b) within the interparticle gap as a function of distance (g) between two gold nanorings. As g reduces, the electric-field intensity between the two particles is enhanced due to plasmonic coupling. (c) Induced aggregation and plasmon coupling causes a red-shift in the absorption spectrum. As a result, the absorbance at 710 nm increases. (d,e) Aggregation-based enhancement of the PA signal in vitro. (d) PA intensity curves of AuNPs and AuNPs@P3—a positive control that self-aggregates showing that increased NIR absorbance leads to a higher PA signal compared to the unaggregated control. (e) PA signal of AuNPs@P1 and AuNPs@P2 (negative control) treated with collagenase IV for 3 h in PBS buffer. Nanoparticles aggregated in the presence of collagenase IV results in a higher PA signal. Panels (a,b) were reprinted with permission from ref 53. Copyright 2012 American Chemical Society. Panels (c–e) were reprinted with permission from ref 63. Copyright 2020 John Wiley and Sons.