Single Ultrabright Fluorescent Silica Nanoparticles Can Be Used as Individual Fast Real-Time Nanothermometers

Optical-based nanothermometry represents a transformative approach for precise temperature measurements at the nanoscale, which finds versatile applications across biology, medicine, and electronics. The assembly of ratiometric fluorescent 40 nm nanoparticles designed to serve as individual nanothermometers is introduced here. These nanoparticles exhibit unprecedented sensitivity (11% /K) and temperature resolution 128 \, \mathrm{K} \cdot \mathrm{Hz}^{-1/2} \cdot \mathrm{W} \cdot \mathrm{cm}^{-2}, outperforming existing optical nanothermometers by factors of 2-6 and 455, respectively. The enhanced performance is attributed to the encapsulation of fluorescent molecules with high density inside the mesoporous matrix. It becomes possible after incorporating hydrophobic groups into the silica matrix, which effectively prevents water ingress and dye leaking. A practical application of these nanothermometers is demonstrated using confocal microscopy, showcasing their ability to map temperature distributions accurately. This methodology is compatible with any fluorescent microscope capable of recording dual fluorescent channels in any transparent medium or on a sample surface. This work not only sets a new benchmark for optical nano-thermometry but also provides a relatively simple yet powerful tool for exploring thermal phenomena at the nanoscale across various scientific domains.