Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering

Abstract

Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10(14) to 10(15), much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.

Enhanced Fluorescence from Fluorophores on Fractal Silver Surfaces

“…This result is roughly consistent with recent SERS data which showed the presence of intense signals, which appeared to be located between clusters of particles. [25][26] Emission spectra were collected from eight selected regions of varying brightness. In all cases, the emission spectra appeared to be that of fluorescein (Figure 4).…”

Non-destructive state detection for quantum logic spectroscopy of molecular ions

“…Here, we demonstrate for the first time quantum logic operations between a single molecular ion and a co-trapped atomic ion, making a wide range of molecular ions accessible to this highlydeveloped toolbox. The presented technique allows the investigation of single molecules in a well isolated system avoiding disturbance from the environment, which is the limiting factor in other implementations of single molecule spectroscopy such as surface enhanced Raman spectroscopy (SERS) 22 Quantum logic operations between atoms are based on state dependent forces often induced by laser fields. The same approach is applicable to molecular ions.…”

Surface-Enhanced Raman Spectroscopy-Based Label-Free Insulin Detection at Physiological Concentrations for Analysis of Islet Performance

“…Surface-enhanced Raman spectroscopy (SERS) is an ideal approach for optical label-free sensing because it identifies targeted molecules based on their unique vibrational and rotational signatures. [22][23][24][25][26] Application of SERS for hormone detection appears relatively unexplored due to minimal experimental success: previously reported SERS-based quantitative insulin sensors were limited due to weaklyenhancing substrates made of randomly dispersed nanoparticles resulting in micromolar detection sensitivity, approximately 2 to 4 orders of magnitude larger than clinically-relevant insulin levels. [27][28][29][30] In this study, we report highly sensitive SERS-based insulin sensing at clinically relevant concentrations using a non-resonant SERS substrate with strong signal enhancement and wafer- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5 scale uniformity.…”