Characterization of tracers for two-color laser-induced fluorescence thermometry of liquid-phase temperature in ethanol, 2 ethylhexanoic-acid/ethanol mixtures, 1-butanol, and o-xylene

Raw data set to the publication: https://doi.org/10.1364/AO.419684

The fluorescence spectra of dye solutions change their spectral signature with temperature. This effect is frequently used for temperature imaging in liquids and sprays based on two-color laser-induced fluorescence (2cLIF) measurements by simultaneously detecting the fluorescence intensity in two separate wavelength channels resulting in a temperature-sensitive ratio. In this work, we recorded temperature-dependent absorption and fluorescence spectra of solutions of five laser dyes (coumarin 152, coumarin 153, rhodamine B, pyrromethene 597 and DCM) dissolved in ethanol, a 35/65 vol.% mixture of ethanol/2-ethylhexanoic acid, ethanol/HMDSO, o-xylene, and 1-butanol to investigate their potential as temperature tracer in evaporating and burning sprays. The dissolved tracers were excited at either 266, 355, and 532 nm (depending on the tracer) for temperatures between 296 and 393 K (depending on the solvent), and for concentrations ranging between 0.1  and 10 mg/l. Absorption and fluorescence spectra of the tracers were investigated for their temperature dependence, the magnitude of signal re-absorption, the impact of different solvents and varying two-component solvent compositions. Based on the measured fluorescence spectra the tracers were analyzed for their 2cLIF temperature sensitivity in the respective solvents. Coumarin 152 showed for single-component solvents the overall best spectroscopic properties for our specific measurement situation related to temperature imaging measurements in spray-flame synthesis of nanoparticles as demonstrated previously in ethanol spray flames (Prenting et al., Exp. Fluids 61 (2020) 77).

本数据集对应发表论文：https://doi.org/10.1364/AO.419684

染料溶液的荧光光谱会随温度变化改变其光谱特征。该效应常被用于液体与喷雾的温度成像，具体基于双色激光诱导荧光（two-color laser-induced fluorescence, 2cLIF）测量技术：通过同时检测两个独立波长通道内的荧光强度，得到对温度敏感的强度比值。

本研究中，我们测试了五种激光染料（香豆素152、香豆素153、若丹明B、吡咯甲川597及DCM）分别溶解于乙醇、35/65体积比的乙醇/2-乙基己酸混合溶剂、乙醇/六甲基二硅氧烷（HMDSO）、邻二甲苯以及正丁醇中的温度依赖性吸收光谱与荧光光谱，以探究这些染料作为蒸发与燃烧喷雾中温度示踪剂的潜力。

本研究针对不同示踪剂分别采用266 nm、355 nm或532 nm波长进行激发；测试温度范围为296 K至393 K（随溶剂种类变化），示踪剂浓度范围为0.1 mg/L至10 mg/L。我们对各示踪剂的吸收光谱与荧光光谱展开系统研究，分析其温度依赖性、信号再吸收强度、不同溶剂及二元溶剂组分变化的影响。基于实测荧光光谱，我们评估了各示踪剂在对应溶剂中的2cLIF温度敏感性。

针对本研究中与纳米颗粒喷雾火焰合成温度成像相关的特定测试场景，香豆素152在单一组分溶剂中展现出最优的综合光谱特性——这一结论已在乙醇喷雾火焰测试中得到验证（Prenting等，Exp. Fluids 61 (2020) 77）。