# Single-particle surface-enhanced coherent anti–Stokes Raman scattering: Nanoparticle design and mechanism

## TL;DR

This study explores how nanoparticle design affects SECARS signals, identifying optimal shapes for high-speed Raman imaging.

## Contribution

The paper identifies star-core core-satellite nanoparticles as effective for single-particle SECARS imaging.

## Key findings

- Only star-core core-satellite NPs produced single-particle SECARS signals.
- NP properties like size, morphology, and polarization influence SECARS enhancement.
- Findings guide the design of NPs for biological imaging and chemical sensing.

## Abstract

Surface-enhanced coherent anti–Stokes Raman scattering (SECARS) is believed to increase the signal intensity and sensitivity by combining the localized surface plasmon resonance and coherent Raman enhancement. However, the realization of SECARS is more complex than for surface-enhanced Raman scattering (SERS) and remains challenging. Unlike SERS, the nonlinear CARS process requires the coherent interaction of three distinct fields. The interactions between the electric fields and nanoparticle (NP) morphology for single-particle SECARS remain unexplored, and the underlying mechanisms generating the SECARS signal are not fully understood. Here, 27 distinct NPs were synthesized and screened using a CARS microscope. Among them, only star-core core-satellite NPs show single-particle SECARS signals, which were affected by laser polarization, two-photon luminescence background, photoinduced heating effects, particle size, and particle morphology. The influence of NP properties on SECARS enhancement offers guidance for the design and synthesis of NPs for single-particle SECARS and opportunities in biological imaging and chemical sensing.

Screening diverse nanoparticle sizes and shapes identifies properties for high-speed single-particle Raman imaging probes.