Tailoring the luminescence properties of Cs2TeCl6 nanocrystals via high-pressure and low-temperature stimuli for multi-parameter optical manometry and thermometry

To search for bifunctional luminescent platform for optical manometry and thermometry, the Cs₂TeCl₆ nanocrystals were prepared. Excited at 456 nm, the designed nanocrystals emitted dazzling orange emission centered at 596 nm, arising from self-trapped exciton emission, whose fluorescence intensity, full width at half maximum (FWHM) and decay time were sensitive to temperature. Through analyzing the temperature-dependent lifetime, the thermometric properties of the resulting nanocrystals was evaluated, resulting in high relative sensitivity of 3.76% K^-1. Moreover, the in-situ pressure-dependent Raman and emission spectra were tested to clarify the potential of the developed nanocrystals for optical manometry. The pressure-related Raman spectra demonstrated the splendid structural stability and reversibility of the studied sample. Via studying the pressure-dependent Raman modes, one knows that the maximum pressure sensitivity of Cs₂TeCl₆ nanocrystals was 9.62 cm^-1/GPa.  Furthermore, when pressure was increased, distinct spectral blue-shift was observed in the synthesized nanocrystals, contributing to the controllable luminescence at high-pressure, i.e., the emitting color changed from orange to yellow. Through analyzing the pressure-dependent emission band centroid and FWHM, one knows that the maximum pressure sensitivities of the resultant nanocrystals were 3.54 and 4.82 nm/GPa, respectively. Notably, when the color coordinate was adopted as the manometric parameter, colorific pressure sensing was also realized in the designed nanocrystals, resulting in a relative sensitivity of 4.62% GPa^-1. Our findings imply that the utilization of high-pressure and low-temperature stimuli is an efficient route to regulate the luminescence properties of the Cs₂TeCl₆ nanocrytals, ensuring their feasibilities in optical thermometry and manometry.