Spaser Nanoprobes Family for Narrow-Band Multiplexed Cell Imaging

Spaser nanoprobes, with their ultranarrow emission line widths and nanoscale sizes, are emerging as leading contenders for the next generation of biological luminescent probes. However, modulating spasing wavelengths across a broad spectral range remains a formidable challenge that constrains their application in multiplexed sensing and imaging. Here, we introduced a novel wavelength-tunable spaser system, successfully creating a nanoprobe family with 9 distinct spasing wavelengths. These nanoprobes exhibit ultranarrow emission line widths of 3-8 nm with a low pump threshold of 0.5 mJ cm^-2. We further investigated the influences of energy matching between the gain medium and the cavity on the emission performance of the spaser nanoprobes and successfully realized narrow-band luminescence in both individual and aggregated spaser particles under commercial confocal instruments. Moreover, we demonstrated the multiplexed imaging capability of 6 distinct spaser nanoprobes in a single HeLa cell within an imaging window of 200 nm, free of spectral crosstalk. Our results address the long-standing issue of wavelength tunability in spaser nanoprobes and also clarify previous disputes on the luminescence origin of single nanoparticles, marking a significant advancement in their application for ultramultiplexed biological imaging and sensing.