Commercial nanodiamonds for precise fluorescence-based temperature sensing.

This article focuses on the use of fluorescent nanodiamonds (FNDs) containing nitrogen-vacancy (NV) color centers for precise temperature sensing in aqueous solutions. The study characterizes the spectrofluorometric properties of the NV zero-phonon lines at 575 nm (NV⁰) and 637 nm (NV⁻) in 100 nm commercial nanodiamonds at 0.5 mg/ml concentration over a temperature range of 30–45 °C, demonstrating high linear correlations between fluorescence intensities and temperature. Results indicate that the NV⁰ relative intensity provides temperature measurements with an uncertainty as low as 0.4 °C, while NV⁻ intensity shows slightly larger errors, and that intensity ratios between NV charge states reveal thermally induced charge recombination effects. The findings suggest that commercially available FNDs can serve as accessible, stable, and low-cost all-optical nanothermometers suitable for biological and material science applications.