Nd3+-doped Bi2SiO5 nanospheres for stable ratiometric optical thermometry in the first biological window

Abstract

The development of nanoscale thermal sensors with high sensitivity to ambient temperature change is crucial to monitor the biological processes from living forms. In this work, we report on the Nd3+-doped Bi2SiO5 nanospheres acting as nanothermometers in the first biological window. Uniform Bi2SiO5:Nd3+ nanospheres are synthesized by the diffusion and reaction between the bismuth-based precursor core and the silica shell. The as-synthesized Bi2SiO5:Nd3+ nanospheres can be effectively excited by 808 nm near infrared laser diode and emit in the near infrared range due to the characteristic transitions of Nd3+. The luminescence intensity ratio of two spectrally separated emission peaks located at 867 nm (P1) and 898 nm (P2) from the 4F3/2 → 4I9/2 transition of Nd3+ is found to be noticeably temperature-dependent, which can be used for luminescent ratiometric thermal sensing. The results reveal that the yielded Bi2SiO5:Nd3+ nanothermometers possess suitable values of relative sensitivity, temperature uncertainty and repeatability within the physiologically relevant temperature range. These Nd3+-doped Bi2SiO5 nanospheres emerge as very promising temperature probes for luminescence nanothermometry.