Upconversion nanoparticle–Ag@C@Ag composite films for rapid temperature sensing

Abstract

Conventional thermometers could not meet the requirements of temperature sensing at the nanoscale. Recently reported upconversion fluorescent nanothermometers have good performance for the nanoscale temperature sensing but require a relatively long response time. Here, we significantly improve the response rate of optical temperature sensing of upconversion nanoparticles (UCNPs) by coupling with Ag@C@Ag nanoparticles. Ag@C@Ag core–shell nanoparticles have a much higher thermal conductivity than UCNPs and are used for rapid thermal sensing and subsequent thermal diffusion media to UCNPs. It is found that the UCNP–Ag@C@Ag composite film thermometer has a temperature response rate higher than 264% of that of singular UCNP thermometers, if UCNPs are coupled with an optimal proportion of Ag@C@Ag nanoparticles in the composite film. The theoretical simulation indicates that this remarkably enhanced response rate is ascribed to the efficient near field energy transfer from the core–shell Ag@C@Ag structure to the UCNPs.