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 using a one-step aqueous phase method. They exhibited good optical absorption properties and pH stability. 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 absorbance at 635 nm. Then, sesame ball-like Zn₂Ga_2.92Hf_0.045Ge_0.75O₈:Cr_0.02–Ag₂S (ZGGO:Cr,Hf–Ag₂S) composite nanoplatforms with fluorescence-background-free temperature sensing were constructed by electrostatic adsorption of Ag⁺-poor Ag₂S nanoparticles onto 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 5 mm, the bactericidal rates of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) can reach 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 nanothermometers to realize real-time temperature monitoring during therapy processes. The temperature sensitivity is found to increase 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 °C, suggesting that the constructed sesame ball-like composite nanoplatforms can realize noncontact temperature sensing and deep tissue sterilization using a 635 nm laser excitation at the same time.