ИСТИНА

Micro-diamonds with color centers are promising objects for various applications spreading from microelectronics to quantum optics due to their remarkable mechanical, thermal, and optical properties. Photoluminescence (PL) of color centers in diamonds can be also applied for precise temperature sensing at the micro- and nano-scales. Micro-diamonds are chemically inert and biocompatible, widening their application to biophotonics. Synthesis of micro- crystallites with specific needle shape, controlled localization of color centers and enriched with SiVs may allow increasing accuracy and reliability of all-optical temperature determination and sensitivity of the method.Dart-like micron-sized single crystal diamonds needles (D-SCDNs) were obtained by CVD-synthesis. D-SCDNs have a pronounced tip and are enriched with both nitrogen-vacancy (NV) and silicon-vacancy (SiV) color centers, which follows from the presence characteristic PL of these centers in spectra. However, intensity of zero-phonon line (ZPL) of SiV color centers is several orders of magnitude higher then NVs. The major part of SiVs is concentrated in the tip. All-optical thermometry was performed in the following way: The PL spectra of SiV color centers of DSCDNs were measured with excitation at 470 nm wavelength during uniform heating followed by cooling in the physiologically significant range (25-55 °C). The dependencies of lifetime, FWHM and peak position of SiV ZPL and its intensity on temperature were investigated. In order to reduce the errors caused by equipment and laser intensity fluctuations and to increase the measurement accuracy, we applied the normalizing of PL intensity measured at the maximum peak position of SiVs' ZPL (λem=738 nm) on the intensity at the wavelength where it is temperature independent (λem=732 nm).