Plasmonic nanoparticles can be utilized as surface-enhanced Raman scattering (SERS) probes for bioimaging and as photothermal (PT) agents for cancer therapy. Typically, their SERS and PT efficiencies reach maximal values under the on-resonant condition, when the excitation wavelength overlaps the localized surface plasmon resonance (LSPR) wavelength preferably in the near-infrared (NIR) biological window. However, the photogenerated heat may inevitably disturb or even destroy biological samples during the imaging process. Herein, we develop ultrabright SERS probes composed of metallic Au@Ag core-shell rodlike nanomatryoshkas (RNMs) with embedded Raman reporters. By rationally controlling the Ag shell thickness, the LSPR of RNMs can be tuned from UV to NIR range, resulting in highly tunable SERS and PT properties. As bright NIR SERS imaging nanoprobes, RNMs with a thick Ag shell are designed for minimal PT damage to the biological targets under the off-resonance condition, as illustrated through monitoring the changes in mitochondrial membrane potential of cancer cells during SERS imaging procedure. By contrast, RNMs with a thin Ag shell are designed as multifunctional NIR theranostic probes that combine enhanced photothermal therapy capability, as exemplified by efficient PT killing of cancer cells, with reduced yet still efficient imaging properties at the on-resonance excitation.

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With the increasing need for multi-purpose analysis in the biomedical field, traditional single diagnosis methods cannot meet the requirements. Therefore new multifunctional technologies and materials for the integration of sample collection, sensing and imaging are in great demand. Core-shell nanoparticles offer a unique platform to combine multifunctions in a single particle. In this work, we have constructed a novel type of core-shell superparamagnetic nanoshell (Fe₃O₄@SiO₂@Au), composed of a Fe₃O₄ cluster core, a thin Au shell and a SiO₂ layer in between. The obtained multifunctional nanoparticles combine the magnetic properties and plasmonic optical properties effectively, which were well investigated by a number of experimental characterization methods and theoretical simulations. We have demonstrated that Fe₃O₄@SiO₂@Au nanoparticles can be utilized for two-photon luminescence (TPL) imaging, near-infrared surface-enhanced Raman scattering (NIR SERS) and cell collection by magnetic separation. The TPL intensity could be further greatly enhanced through the plasmon coupling effect in the self-assembled nanoparticle chains, which were triggered by an external magnetic field. In addition, Fe₃O₄@SiO₂@Au nanoparticles may have great potential applications such as enhanced magnetic resonance imaging (MRI) and photo-thermotherapy. Successful combination of multifunctions including magnetic response, biosensing and bioimaging in single nanoparticles allows further manipulation, real-time tracking, and intracellular molecule analysis of live cells at a single-cell level.

Off-resonant gap-enhanced Raman tags (GERTs) show ultrahigh Raman enhancement and photostabilities and therefore can be used as ideal highly photostable nanoprobes for high-speed and high-resolution Raman bioimaging.

Combination of surface enhanced Raman scattering and multivariate statistical method allows to identify and distinguish three subtypes of non-small-cell lung cancer cells and leukocytes on the single-cell level.

Construction of ordered patterns of plasmonic nanoparticles is greatly important for nanophotonics relevant applications. We have reported a facile and low-cost magnetic field induced self-assembly approach to construct plasmonic superparamagnetic nanoshell (SN) chains up to several hundred micrometers in a few seconds in a large area without templates or other assistance processes. Experimental and theoretical investigations of the near- and far-field optical properties indicate that the super- and sub-radiant modes of the SN chains continuously redshift with the increase of SN number and the Fano resonance emerges in the infinite double- and triple-line SN chains. Strong plasmon coupling effects in the SN chains result in great electric field enhancements at visible and infrared wavelengths, which indicates that these chain structures potentially can be used as a common substrate for both surface enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) application. This fabrication method also offers a general strategy alternative to top-down processing that enables the construction of nanostructures for metamaterials, electromagnetic energy transport, and optical waveguide.

Surface-enhanced Raman scattering (SERS) nanoparticles can be utilized as optical labeling nanoprobes for bioimaging with advantages of the fingerprint vibrational signal as a unique optical code and the ultra-narrow linewidth for multiplexing. As a new type of SERS nanoprobes, gap-enhanced Raman tags (GERTs) developed recently can overcome the common issues of poor photostability and limited Raman enhancement. In this work, we have constructed bright nanotriangle-based GERTs (NT-GERTs) for combined SERS bioimaging and photothermal therapy. With optimized Au shell morphology and thickness, NT-GERTs possess 20 folds brighter SERS signal and a more efficient photothermal effect compared to conventional nanosphere-based GERTs. These NT-GERTs show great potential for intraoperative SERS bioimaging guided photothermal therapy of cancers.

Multifunctional superparamagnetic nanoshells were applied for improved 2D and 3D two-photon luminescence imaging, separation and seeding of co-cultured cells.