Toward Performance and Applications of Large Area Optical Thermometry Based on the Luminescence of Germanium‐Vacancy Defects in Diamond Nanocrystals

Abstract

Herein optical properties of aggregates of hydrophobic nanodiamonds (NDs) with germanium‐vacancy (GeV) defects distributed on substrates with different hydrophilicities (bare Si or TiO2 (anatase) film on Si substrate) are investigated with an aim to achieve millimeter‐scale, nearly homogeneous spatial distribution of ND aggregates. ND aggregates are spread by drop casting of a water colloid. The luminescence spectra of GeV defects are studied in a wide temperature range (85–400 K). The possibility of optical thermometry operating in a wide temperature range also covering biotemperatures is demonstrated using a separate microaggregate of NDs on the anatase film.

Luminescence Thermometry with Nanoparticles: A Review

“…They observed the thermal shift of the GeV center's ZPL at 602 nm and fitted it with different models. The results shown in Figure 19 proved that nanodiamond aggregates with GeV center are optical temperature sensors with a sensitivity of 0.2 cm −1 K −1 at room temperature [147]. Unlike NV centers, which exhibit an almost 100 nm broad emission band, group IV-based defects in nanodiamonds concentrate almost all their photoluminescence into a few nanometers-wide zero phonon lines (ZPLs), and their temperature-dependent changes have been used for all-optical thermometry [131,[144][145][146][147][148].…”

“…They observed the thermal shift of the GeV center's ZPL at 602 nm and fitted it with different models. The results shown in Figure 19 proved that nanodiamond aggregates with GeV center are optical temperature sensors with a sensitivity of 0.2 cm −1 K −1 at room temperature [147]. Then, the laser excitation was removed, and the object was cooled for 5 min, after which, a spectrum was recorded again.…”

“…NV temperature sensors were characterized using the ODMR method and had maximal temperature sensitivities of ~2 K/Hz −1/2 . Unlike NV centers, which exhibit an almost 100 nm broad emission band, group IV based defects in nanodiamonds concentrate almost all their photoluminescence into a few nanometers-wide zero phonon lines (ZPLs), and their temperature-dependent change have been used for all-optical thermometry [131,[144][145][146][147][148]. Miller et al [147] studied ag gregates of nanodiamonds with germanium-vacancy (GeV) defects distributed on differ ent substrates within a wide temperature range of 85-400 K, with the aim of obtaining 2D optical thermometer with high nanoscale spatial resolution, predominantly for biomedi cal applications.…”

“…The spectra are obtained in the temperature range 293-323 K. Insert: a cluster of ND aggregates; (b) the fits of the ZPL shifts from different theoretical models. Adapted with permission from [147].…”