High-Speed Fluctuations in Surface-Enhanced Raman Scattering Intensities from Various Nanostructures

Abstract

The observation of single molecule events using surface-enhanced Raman scattering (SERS) is a well-established phenomenon. These events are characterized by strong fluctuations in SERS intensities. High-speed SERS intensity fluctuations (in the microsecond time scale) have been reported for experiments involving single metallic particles. In this work, the high-speed SERS behavior of six different types of nanostructured metal systems (Ag nanoshells, Ag nanostars, Ag aggregated spheres, Au aggregated spheres, particle-on-mirror, and Ag deposited on microspheres) was investigated. All systems demonstrated high-speed SERS intensity fluctuations. Statistical analysis of the duration of the SERS fluctuations yielded tailed distributions with average event durations around 100 μs. Although the characteristics of the fluctuations seem to be random, the results suggest interesting differences between the system that might be associated with the strength distribution and density of the localized SERS hotspots. For instance, systems with more localized fields, such as nanostars, present faster fluctuation bursts compared to metallic aggregates that support spread-out fields. The results presented here appear to confirm that high-speed SERS intensity fluctuations are a fundamental characteristic of the SERS effect.

Ultra-High-Speed Dynamics in Surface-Enhanced Raman Scattering

“…In some occasions, the Stokes-shifted SIF activities were seen to originate from different locations at different times for each of the excitation colors. Similarly, experiments performed using two different polarizations (perpendicular to each other) also revealed selective excitation of different areas on a single particle, suggesting that the excitation conditions for individual hotspot environments were accessed.…”

“…In some occasions, the Stokes-shifted SIF activities were seen to originate from different locations at different times for each of the excitation colors. Similarly, experiments performed using two different polarizations (perpendicular to each other) also revealed selective excitation of different areas on a single particle, 39 suggesting that the excitation conditions for individual hotspot environments were accessed. The statistics of the time dependent SIFs presented in Figures 3 and 4 seems to imply that hotspots are turned on (and off) in very localized regions on the single nanoparticle, which allow single molecule events to be observed even from a fully coated surface.…”

Negative DNA supercoiling makes protein-mediated looping deterministic and ergodic within the bacterial doubling time

“…Yet, in the thermal bath of the eukaryotic nucleus, or prokaryotic nucleoid, molecular motion is random and the behavior of a molecule can only be described in probabilistic terms ( 8 , 9 ). Single-molecule experimentation allows fluctuation analysis ( 10–12 ) and has revealed very heterogeneous behavior of molecules ( 13–18 ). Measurements have shown that protein-mediated loops form and rupture stochastically, and the lifetimes of such loops span several orders of magnitude ( 19–22 ).…”

Negative DNA supercoiling makes protein-mediated looping deterministic and ergodic within the bacterial doubling time

“…Yet, in the thermal bath of the eukaryotic nucleus, or prokaryotic nucleoid, molecular motion is random and the behavior of a molecule can only be described in probabilistic terms (Nelson, 2003;Phillips R. et al, 2013). Single-molecule experimentation allows fluctuation analysis (Bido et al;Kundu et al, 2020;Milenkovic et al, 2020) and has revealed the robustly heterogeneous looping behavior of molecules (Datta and Seed, 2018;Finzi and Gelles, 1995;Graham et al, 2017;Kumar et al, 2016;Manzo et al, 2011;Manzo et al, 2012;Miyashita et al, 2015;Neuman et al, 2003;Wang et al, 1998;Zurla, 2009). Indeed, protein-mediated loops form and rupture stochastically in purified systems, and the lifetimes of such loops span several orders of magnitude.…”

“…Yet, in the thermal bath of the eukaryotic nucleus, or prokaryotic nucleoid, molecular motion is random and the behavior of a molecule can only be described in probabilistic terms (6,7). Single-molecule experimentation allows fluctuation analysis (8)(9)(10) and has revealed very heterogeneous looping behavior of molecules (11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Measurements have shown that protein-mediated loops form and rupture stochastically, and the lifetimes of such loops span several orders of magnitude.…”