Suppression Of Energy Transfer In Hybridized Organic Films For High Temperature Ratiometric Sensing

Luminescent thermometry,generally based on temperature dependent luminescence intensity,luminescence lifetime and ratiomteric intensity,has receiving increasing attentions due to its non-invasive detection,high temporal/spatial resolution,high sensitivity,resistance to electrical/magnetic fields and the ability to work with fast moving objects.Among them,ratiometric luminescent thermometry presents a more reliable and accurate measurement due to its self-reference sensing characteristics.This enables the sensing behavior independent of luminophore concentration,fluctuation of excitation source/detector and luminescence background.However,ratiometric luminescent thermometry commonly relies on energy transfer between different colored emitters,which usually decreases their original marked difference in temperature responsiveness when mixing together.This often results in low sensitivity and poor repeatability.Therefore,suppression of energy transfer provides a feasible strategy to achieve high-performance ratiometric thermosensing.Herein mixing two thermal-resistant luminophores,simply by varing the long-wavelength emitter concentration,a series of solid-films with different doping ratio are prepared.It is investigated that by systematic photophysical properties,the energy transfer efficiency is found to be only 34.71%at higher acceptor ratio of 60%and even slightly decrease to 32.58%by further increasing the acceptor concentration to 80%.But,the spectrum overlap integral（J）is prominent to be 2.51×10¹³cm^-1nm⁴.Atomic force microscopy（AFM）phase images reveal that this phase separation around nanopores becomes dominant when the doping ratio reaches above 40%.We clearly explain the mechanism in suppression of energy transfer,by increasing the dopant concentration to induce microphase separation.On this basis,one of the inexpensive and easily prepared solid-film organic high temperature ratiometric thermometers have been developed.The maximum absolute sensitivity（S_a）is measured as 1.49×10^-2K^-1at 464 K（191°C）,and the maximum relative sensitivity（S_r）is 1.12%K^-1at 429 K（156°C）.They exhibit a broad eye-detective sensing range of 102–236°C with the relative sensitivity（S_r）higher than 0.5%K^-1and the maximum temperature resolution attaining 0.39 K.Good reversibility and stability have also been demonstrated in ambient atmosphere.With temperature rising from room temperature to 300°C,digital numbers are yellow-green,greenish white,white and blue purple emissive,which enables multiple anti-counterfeiting encryptions for safety information storage.Moreover,hybridizing a thermal-resistant luminophore with an excited state intramolecular proton transfer（ESIPT）compound,by minimize the spectrum overlap to block energy transfer,designs another high-proformance solid-film organic high temperature ratiometric thermometers.The maximum absolute sensitivity（S_a）and maximum relative sensitivity（S_r）are measured as 1.684×10^-2K^-1（459.87 K）,and 1.223%K^-1（414.62 K）.The operating effective temperature range is determined to be 293～493 K,with the temperature resolution below 0.5 K,offering the minimum values of 0.067 at 393 K,0.062 at 453 K,0.066 at 473 K respectively.These works provide new methods for establishing robust and sensitive surpressed-energy-transferred film thermometers for naked-eye high temperature sensing.