一种非接触式稀土荧光自参比温度传感器

A Contactless Self-Calibration Temperature Sensor Based on the Rare-Earth Fluorescence

发展了一种非接触式稀土荧光自参比温度传感器,即将有机稀土配合物K[Yb(Az)_4]包埋在苯乙烯-甲基丙烯酸甲酯共聚物中,并附着在洁净的石英片上制备得到了温度传感薄膜Yb@PSMM。通过研究不同温度下Yb^(3+)的荧光发射光谱,利用其在近红外波段荧光性质随温度变化的规律,开发了一种比率型稀土荧光温度传感方法,其原理是通过不同温度下Yb^(3+)的荧光发射光谱的形状随温度的变化,结合在不同温度下Yb^(3+)的核外电子在外层Stark劈裂亚能级上的分布符合Boltzmann分布律的特点,利用其近红外荧光发射光谱中900 nm～990 nm波长范围内与990～1 150 nm波长范围内的积分峰面积比的自然对数与温度的倒数呈现的线性关系作为温度测量的标准曲线,实现了-195～105℃范围内的温度精确测量。经考察,该发光温度传感器在0℃附近的温度测量分辨率达到了0.1℃。与已报道的发光温度传感器相比,提出的新型温度传感器具有如下几个优势:其一,所选用的发光材料的Stokes位移大于500 nm,有效地避免了环境背景干扰;其二,由于采用荧光积分峰面积而非荧光强度作为考察对象,大大减小了测量中由于仪器或测量次数较少引入的随机误差;其三,采用同一发光材料的荧光发射光谱中两个荧光峰面积的比值,相当于在体系中引入了自参比,有效避免了由于荧光材料的浓度、几何构型以及光源强度等外界因素变化对测量结果产生的影响;其四,利用稀土发光材料作为温度传感材料,可以利用其荧光寿命长、单色性好、强度高的特点;其五,温度传感膜本身不溶于水,也不在水中扩散,便于直接测量原位温度变化;其六, Yb^(3+)的发光位于900～1 150 nm的近红外波长范围,而这个波段的荧光具有较好的穿透性使得该温度传感器有望在复杂体系的温度传感、成像等领域发挥重要作用。在实际测量的装置中,通过调整光路使得辐照在样品上的入射光斑大小仅约为1 mm^2,并将Yb@PSMM固体膜样品的放置方向与入射激发光的夹角设置为225°,从而规避了入射光源的反射光对检测器的影响,而具有较好穿透能力的近红外荧光几乎不受影响,从而进一步确保了该温度传感器的测量结果。

A contactless self-calibration temperature sensor based on the rare-earth fluorescence was developed.The new temperature sensing film Yb@PSMM was prepared by dispersed K[Yb(Az) 4] in poly (styrene-block-methyl methacrylate) and then attached to a clean quartz plate,and the optical properties of Yb^3+ in this system under different temperature were investigated.The shape of the fluorescence emission spectrum of Yb^3+ changed regularly with temperature,and the distribution of extra-nuclear electrons in the Stark cleavage sublevels of Yb^3+ at different temperatures still obeyed Boltzmann distribution law.The natural logarithm (ln) of the ratio of the two characteristic emission peak areas at 900~990 and 990~1150 nm in the fluorescence spectrum linearly varied with the reciprocal of temperature (1/ T ) from -195 to105 ℃.Upon using this linear relation as the standard curve,this temperature sensing method exhibited a temperature resolution of 0.1 ℃ around 0 ℃.Compared with the reported luminescence temperature sensors,the new temperature sensor proposed in this paper had advantages as follows.Firstly,the Stokes shift of the selected luminescent material was larger than 500 nm,which effectively avoided the interference of environmental backgrounds.Secondly,due to the use of fluorescence integrated peak areas instead of fluorescence intensities,the influence of random errors introduced by the instrument or measurement was greatly reduced.Thirdly,by taking advantage of the radiometric relationship between the intensities of different fluorescence peaks in one compound,a reliable self-calibration was introduced in this system equality,which effectively reduced the influence of external factors such as the variation of fluorescent material concentration,geometric configuration,or light source intensity.Fourthly,as a rare-earth luminescence material,the sensing method could utilize the characteristics of long fluorescence lifetime,good fluorescence monochromaticity,and high fluorescence intensities.Fifthly,the temperature sensing film was almost insoluble and indiffusible in water,which was convenient for direct measurement of the in-situ temperature changes.Lastly,Yb^3+ emission was from 900 to1150 nm,due to the deep penetration of near infrared light,this temperature sensor would have a wide potential use in temperature-sensing and imaging of complex system.Further ensuring method for the measurement results of the temperature sensor was adopted in our measurement device: the irradiated spot size on the sample could be adjusted to be about1 mm2,and the angle between the placement direction of Yb@PSMM film and the excitation light was set to be225°.Thus,the influence of the reflected light was circumvented,but the fluorescent emission light was hardly affected.