Nanocrystallized copper phosphate endowed with photothermal conversion and photoacoustic imaging capabilities

Copper-based nanomaterials have garnered significant attention for their potential applications in photothermal (PT) conversion and photoacoustic (PA) imaging due to their unique optical properties. However, current strategies often involve complex synthesis processes and the incorporation of additional materials, which limit their practical applicability. Here, we employed a straightforward nanocrystallization method to synthesize copper phosphate nanoparticles (Cu 3 (PO 4 ) 2 NPs), converting free copper ions into solid-phase nano-sized particles. This approach not only simplifies the synthesis process but also enhances the optical and thermal properties of the resulting Cu 3 (PO 4 ) 2 NPs. The Cu 3 (PO 4 ) 2 NPs achieved a temperature increase of over 20°C and a PT conversion efficiency of 10.5% under 808 nm laser irradiation. Furthermore, Cu 3 (PO 4 ) 2 NPs exhibited strong, concentration-dependent PA signals, which enabled effective deep tissue imaging in vivo. The enhanced properties of Cu 3 (PO 4 ) 2 NPs can be attributed to the nanocrystallization of the particles, which alters the local environment of copper ions and enhances [Formula: see text] transitions through specific ligand field effects. These effects increase light absorption, particularly in the NIR region, by facilitating better overlap of electronic states and enabling more efficient non-radiative relaxation processes. This highlights the significance of nano-structuring in developing advanced nanomaterials with tailored functionalities for biomedical applications.