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

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.