Sesame-ball-like PTT nanoplatforms with fluorescence-background-free temperature sensing

Abstract

In this study, spherical Ag+-poor Ag2S nanoparticles (~15.8 nm) with uniform distribution (~2.1 nm) were successfully synthesized by a one-step aqueous phase. They exhibited good optical absorption properties and pH stability. The first principles calculations show that Ag deficiency leads to the decreased contribution originating from the transition from Ag 4d orbitals to S 3p orbitals and the reduced absorptance at 635 nm. Then, the sesame-ball-like Zn2Ga2.92Hf0.045Ge0.75O8:Cr0.02-Ag2S (ZGGO:Cr,Hf-Ag2S) composite nanoplatforms with fluorescence-background-free temperature sensing were constructed by electrostatic adsorption of Ag+-poor Ag2S nanoparticles on the surfaces of near-spherical ZGGO:Cr,Hf nanoparticles. It is found that their photothermal conversion efficiency is about 46% upon 635 nm excitation. In addition, they showed good photothermal stability and biocompatibility and enhanced photothermal conversion ability in response to acidic pH environments. As the tissue thickness reaches to 5 mm, the bactericidal rates of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) can reach to about 72% and 64%, respectively. Meanwhile, the sesame-ball-like ZGGO:Cr,Hf-Ag2S composite nanoplatforms with broad-spectrum bactericidal performance can be used as afterglow ratio nanothermometer and realize real-time temperature monitoring during the therapy process. The temperature sensitivity is found to increases from 0.052 to 0.054 K-1 with increasing temperature from 307 to 320 K. The temperature difference between the noncontact and direct measurements is about 0.78℃, suggesting that the constructed sesame-ball-like composite nanoplatforms to realize noncontact temperature sensing and deep tissue sterilization using a 635 nm laser excitation at the same time.