Accurate measurements of organic dye solutions by use of pulsed laser photothermal deflection spectroscopy.
Accurate measurements of organic dye solutions by use of pulsed laser photothermal deflection spectroscopy.
复制标题
使用脉冲激光光热偏转光谱法精确测量有机染料溶液。
DOI：
10.1021/ac00111a028
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发表时间：
1995
影响因子：
7.4
通讯作者：
Bialkowski,SE
中科院分区：
文献类型：
--
作者：
Chartier,A;Bialkowski,SE
具有有限三重态量子产率的有机染料分子被示出为产生异常的光热信号幅度时，脉冲激光激发。这些异常信号可能是由于电子单重态的光学漂白和随后的三重态自旋流形内的光学吸收引起的。基于激发态和激发态弛豫速率表达式，推导出一个模型，并应用于分析激发激光辐照度相关的光热信号幅度数据。该模型与实验结果吻合较好。随后，它被用来纠正光热签署在高辐照度和推导出所研究的分子的光动力学参数。模型与激发辐照相关数据的回归允许确定T2-Ti弛豫速率常数和三重态交叉吸收截面。将模型回归应用于水和乙醇溶剂中赤藓红的分析以及乙醇溶剂中曙红和碘化1，1 '-二乙基-2，2-花菁染料的分析。发展了一种定量测定分析物浓度的方法。分析光热光谱法采用超灵敏技术测量固体、气体和液相样品中的微弱光致发光。1 23”4 5这些方法通过监测样品内的光激发和随后的热弛豫产生的折射率变化来工作。光热偏转光谱法和光热透镜光谱法是测量均匀流体样品光吸收的两种最常用的光热方法。光热透镜和偏转光谱仪的工作原理和实验设计非常相似，这两种技术在分析实用性方面几乎没有区别。这两种方法都能达到10 - 6-10 - 7 Au范围内的吸光度检测限。脉冲激励与连续激励的相对优点和分析效用一直是文献中讨论的主题。5 6基于脉冲和连续激光的设备
Organic dye molecules having a finite triplet quantum yield are shown to yield anomalous photothermal signals magnitudes when pulsed laser excitation is used. These anomalous signals can be due tooptical bleaching of the electronic singlet states with subsequent optical absorp-tion within the triplet spin state manifold. A model based on excitation and excited state relaxation rate expressions is derived and applied to the analysis of excitation laser irradiance-dependent photothermal signal magnitude data. The model isfound to fit the experimental results very precisely. It is subsequently used to correct the photothermal signed at high irradiances and to deduce photodynamic parameters from the studied molecule. Regres-sion of the model to the excitation irradiance-dependent data allowsdetermination of the T2—Ti relaxation rate constant and the triplet state cross absorption section. Model regression is applied to the analyses of erythrosin in water and ethanol solvent and of eosin and 1, 1'-diethyl-2, 2-cyanine iodide dyes in ethanol solutions. A method for quantitative determination of analyte concentration is developed.Analytical photothermal spectroscopy employs ultrasensitive techniques to measure weak optical absorbances in solid, gas, and liquid phase samples.* 1 23" 4 5These methods work by monitoring refractive index changes produced by optical excitation and subsequent thermal relaxation within the sample. Photothermal deflection spectroscopy and photothermal lens spectroscopy are the two most widely used of the photothermal methods for optical absorption measurement in homogeneous fluid samples. The operational principles and experimental designs for photothermal lensing and deflection spectrometers are very similar, and there is very little difference in theanalytical utility of these two techniques. Both have been used to achieve absorbance detection limits inthe range of 10 “6-10" 7 AU. The relative merits and analytical utility ofpulsed versus continuous excitation has been a subject of discourse in the literature. 5 6 Apparatuses based on pulsed and continuous laser