Abstract
The dual-modal imaging platform that combines short-wavelength infrared light (SWIR) and photoacoustic (PA) imaging seeks to improve both the imaging resolution and signal-to-noise ratio. Together with the advancement of this dual-modal imaging platform, it is important to co-develop suitable contrast agents that will facilitate the visualization of specific lesions or biochemical pathways. In this work, we studied the feasibility of using CaF2 core-shell (CCS) nanoparticles for both SWIR and PA dual-modal imaging. The composition of the core comprises of ytterbium (Yb3+) and erbium (Er3+) codoped within the CaF2 matrix, whilst the shell comprises of undoped CaF2. An additional SiO2 shell was coated on the CCS nanoparticles to potentially provide these nanoprobes with the ability to be attached to other targeting moieties as well as enhance the PA signal from our nanoprobes. We have found that CCS nanoparticles with Yb3+ of 20 mol% show the maximum visible and SWIR fluorescence emission intensities. The PA signal amplitude was increased by similar to 100% by increasing the Yb3+ concentration or with the addition of a similar to 18 nm SiO2 coating. We have successfully synthesized CCS/SiO2 nanoparticles which show promise as a dual-modal imaging probe for SWIR fluorescence and PA imaging.