Modern analytical thermooptical spectroscopy

Sensitivity Enhancement of Thermal-Lens Spectrometry Using Laser-Induced Precipitation

“…9,14,17 The setup comprises an excitation Ar + laser (Innova 90-6, Coherent, Palo Alto, CA) operated at 488.0 nm (170 mW in the sample, the beam waist 61.3 mm) and a HeNe probe laser (SP 106-1, Spectra-Physics, Eugene, OR; 632.8 nm, 5 mW in the sample; the beam size in the sample, 108.8 mm). The chopping frequency was low (4 Hz) to ensure the complete dissipation of the thermal-lens at the end of each steadystate excitation-cooling cycle.…”

“…20 Basically, these effects provide additional difficulties in the development of thermooptical methods of analysis; however, the reported examples of successful uses of these effects for increasing the analysis efficiency are impressive and promising. 9,20 Still, the uses of laser-induced effects to enhance the thermal-lens signal are not widespread. The enhancement of thermal-lens signal usually involves new experimental configurations for setups, however, various sample-modification techniques are used for changing thermooptical properties of the sampled material, thus improving the thermal-lens sensitivity.…”

“…Laser irradiation in thermooptical spectroscopy could not only provide a local increase in the temperature as a result of laser energy conversion into heat, but could also result in additional effects such as an increase in the reaction rate 9,[14][15][16] or a change in the energy balance of the kinetically controlled reactions, 13 emerging of laser-induced reactions, 11,12 photoinduced decomposition or isomerization, 17,18 or coagulation of metal nanoparticles. 19 On the other hand, products of light-induced or light-enhanced reactions affect the formation of thermal-lens element due to scattering or reabsorption of the radiation.…”

“…7,8 In this connection, the primary trend in developing thermooptical spectroscopy lies in its capabilities of facilitating the basic understanding of the processes following laser irradiation in media and their effects on photochemical and optical parameters of analytes and samples. 4,[9][10][11][12][13][14] This area combines the applications of thermooptical spectroscopy that highlight its unique properties as a method of analytical chemistry.…”

Crystallization monitoring by thermal-lens spectrometry

“…Thermal lensing successfully determines light absorption in the case of inhomogeneous systems: colloid or micellar solutions, solutions of gold nanoparticles [2,3]. Presence of salts, micelles, or polymers in solution could change some thermooptical parameters of the sample like density, thermal conductivity, or the temperature gradient of the refraction index [1].…”