Facile one-step dialysis strategy for fabrication of hollow complex nanoparticles.

We developed a facile one-step dialysis method to prepare a series of hollow iridium complexes and their rare-earth hybrid complex nanoparticles (NPs). The resulting Ir-Dy hybrid NPs exhibited an excellent transverse relaxivity (r(2)) value of similar to 194.5 mM(-1) s(-1) (7.0 T) and a strong ultrasound contrast effect with the signal stable up to 10 min.