Design of novel photothermal conversion nanoparticles integrated with temperature self-response ability based on thermal-enhanced NIR to NIR luminescence

The development of photothermal therapy (PTT) agents possessing temperature self-response ability and working in the deep tissues is an urgent need for noninvasive cancer treatment. Herein, a nanocomposite ma-terial hexagonal phase NaLuF4: Yb3+/Nd3+@SiO2@Cu2S is successfully constructed for the purpose of meeting the above demands. Under the irradiation of 980 nm near-infrared (NIR) light, the prepared nanocrystals (NCs) exhibit good photothermal conversion capacity and ultrasensitive temperature sensing properties along with remarkable resolution. The optical thermometry is realized by the fluorescence intensity ratio of Nd3+: 4Fj (j = 7/ 2, 5/2, and 3/2) levels, of which the NIR emission intensities are strongly enhanced with the increasing tem-perature due to the phonon-assisted energy transfer mechanisms between Yb3+ and Nd3+. As the excitation and emission wavelength of the sample are all located in the biological window, its penetration depth in the bio-logical tissues can be reached to 8 mm. The adsorptive Cu2S NCs on the surface of NaLuF4: Yb3+/Nd3+@SiO2 provide the required light-to-heat conversion capacity, which has been investigated in detail through the laser-irradiated and bactericidal experiment respectively. These findings provide a feasible strategy to design high-performance PTT agents integrated with precise temperature self-measurement function for deep-tissue therapy.

Automated summary

The development of photothermal therapy (PTT) agents that can self-respond to temperature and work in deep tissues is urgently needed for noninvasive cancer treatment. In this study, a nanocomposite material called hexagonal phase NaLuF4:Yb3+/Nd3+@SiO2@Cu2S is successfully created to meet these demands. The prepared nanocrystals (NCs) exhibit excellent photothermal conversion capacity and ultrasensitive temperature sensing properties, enabling optical thermometry using the fluorescence intensity ratio of Nd3+ ions. The adsorption of Cu2S NCs on the surface of NaLuF4:Yb3+/Nd3+@SiO2 provides the necessary light-to-heat conversion capacity, making it a promising candidate for deep tissue therapy.