Accuracy of Measurements of Thermophysical Parameters by Dual-Beam Thermal-Lens Spectrometry

Abstract

Thermal-lens spectrometry is a sensitive technique for determination of physicochemical properties and thermophysical parameters of various materials including heterogeneous systems and nanoparticles. In this paper, we consider the issues of the correctness (trueness) of measurements of the characteristic time of the thermal-lens effect and, thus, of the thermal diffusivity determined by dual-beam mode-mismatching thermal lensing. As sources of systematic errors, major factors—radiation sources, sample-cell and detector parameters, and general measurement parameters—are considered using several configurations of the thermal-lens setups, and their contributions are quantified or estimated. Furthermore, with aqueous ferroin and Sudan I in ethanol as inert colorants, the effects of the intermolecular distance of the absorbing substance on the correctness of finding the thermophysical parameters are considered. The recommendations for checking the operation of the thermal-lens setup to ensure the maximum accuracy are given. The results obtained help reducing the impact of each investigated factor on the value of systematic error and correctly measure the thermophysical parameters using thermal-lens spectrometry.

Composition of the Cytochrome c Complex with Cardiolipin by Thermal Lens Spectrometry

“…For thermal lens experiments, a coaxial two-laser spectrometer was used [ 33 , 64 ]. The thermal lens is induced in the cell by the radiation from an Innova 90-6 argon ion laser (Coherent, Palo Alto, CA, USA) with generation wavelength of 514.5 nm (TEM 00 mode; maximum output radiation power, 1.5 W).…”

Thermal Diffusivity of Aqueous Dispersions of Silicon Oxide Nanoparticles by Dual-Beam Thermal-Lens Spectrometry

“…Ferroin was added to each sample. To reduce the systematic error caused by high absorbance, as described [23], the concentration of ferroin in the dispersions did not exceed 1 µmol/L. After that, the dispersions were mixed for 2 h on a laboratory shaker and used in the analysis.…”

“…The shutter frequency corresponds to the time of full development of the thermal lens and the transient curve reach the steady state. The selection of the number of transient curves for averaging is based on the recommendations made in [23]. The mode-mismatch factor was selected based on the condition of the minimum systematic error identified in [23] and corresponding to the conditions of the model [22].…”

“…The selection of the number of transient curves for averaging is based on the recommendations made in [23]. The mode-mismatch factor was selected based on the condition of the minimum systematic error identified in [23] and corresponding to the conditions of the model [22]. The sample-to-detector distance also corresponds to the conditions of the model [22].…”

“…The sample-to-detector distance also corresponds to the conditions of the model [22]. All systematic errors caused by the periodic divergence of the excitation beam, the relative displacement of two beams in the cell, the bias of the sample cell along the beam propagation, the position of the maximum intensity of the probe beam in the center of the detector are taken into account and reduced to zero, according to the recommendations made in [23].…”