Tunable emission color and anti-thermal-quenching behaviors in niobates for high-sensitive optical thermometry

Sensitive probing of temperature variations on nanometre scales is an outstanding challenge in many areas of modern science and technology. In particular, a thermometer capable of subdegree temperature resolution over a large range of temperatures as well as integration within a living system could provide a powerful new tool in many areas of biological, physical and chemical research. Possibilities range from the temperature-induced control of gene expression and tumour metabolism to the cell-selective treatment of disease and the study of heat dissipation in integrated circuits. By combining local light-induced heat sources with sensitive nanoscale thermometry, it may also be possible to engineer biological processes at the subcellular level. Here we demonstrate a new approach to nanoscale thermometry that uses coherent manipulation of the electronic spin associated with nitrogen-vacancy colour centres in diamond. Our technique makes it possible to detect temperature variations as small as 1.8 mK (a sensitivity of 9 mK Hz(-1/2)) in an ultrapure bulk diamond sample. Using nitrogen-vacancy centres in diamond nanocrystals (nanodiamonds), we directly measure the local thermal environment on length scales as short as 200 nanometres. Finally, by introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, we demonstrate temperature-gradient control and mapping at the subcellular level, enabling unique potential applications in life sciences.

State-of-the-art progress in strategy design based on the Ln 3+ luminescence involving dual emission construction for ratiometric luminescence thermometry is reviewed. The ratiometric fluorescence technique is believed to hold promise as the most important non-contact thermometry technique for future mass application due to the reliability and convenience originating from self-referencing. The discovery of thermally coupled levels in lanthanide ions initiated and boosted the fast development of the ratiometric fluorescence technique for temperature sensing in the past decades. However, the dilemma in the energy spacing between the two thermally coupled levels sets a limitation for further improvement of thermometric performance, which can be addressed by novel strategies other than thermally coupled level routes. The unique electronic structure of Ln 3+ ions offers great opportunities for conceiving such strategies. In this review, we have summarized recent progress in novel strategy design for ratiometric fluorescence temperature sensing, with the focus on the Ln 3+ luminescence involving dual emission construction. Various features of Ln 3+ luminescence dynamics have been described to play critical roles in judicious strategy design.