Photoacoustic Spectrometry Coupled with Total Internal Reflection Technique: Theory and Experiment

Laser-Heating Thermal Modulation Voltammetric Determination of Phosphate Ion Using a Graphite-Reinforced Carbon Electrode

“…The peak intensities for 12-molybdophosphate ion were increased at frequencies lower than 100 Hz, and decreased at frequencies higher than 100 Hz. Since this dependence seemed to be curious, we theoretically estimated the amplitudes of thermal modulation at the chopping frequencies from a thermal-diffusion theory for a system consisting of an optically transparent (the sample solution) and opaque (the electrode) phase, 34,35 and plotted the peak intensities for [Fe II (CN)6] 4-and the 12-molybdophosphate ion against the theoretical amplitudes. The peak intensity for the 12-molybdophosphate ion was not proportional to the amplitude, whereas the peak intensity for [Fe II (CN)6] 4-was proportional.…”

Ultraviolet Laser Photo-Modulation Voltammetry of Tetraphenylborate at a Liquid/Liquid Interface

“…12 In this work, based on a model proposed by them, the concentration dependence was investigated by solving a diffusion equation for the transferring photolytic product under intermittent irradiation. 20 From the model illustrated in Fig. 7, the diffusion equation is expressed by…”

Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces

“…That being said, a new set of techniques, known as evanescent field-based photoacoustics (EFPA) 5,6,15,18, as shown in Figure 1, has the potential to estimate material properties at the nanoscale in a consolidated set of experiments. EFPA encompasses the sub-techniques of total internal reflection photoacoustic spectroscopy (TIRPAS) 23,25,26,[33][34][35][43][44][45] , photoacoustic spectroscopy/total internal reflection photoacoustic spectroscopy refractometry (PAS/TIRPAS refractometry) /C p where α is the volume thermal expansion coefficient, v s is the speed of sound in the medium, and C p is the heat capacity at constant pressure, H 0 is the radiant exposure of the laser beam, c is the speed of sound in the excited medium, x is length, and t is time. The magnitude of the resulting acoustic wave relies directly upon the optical absorption coefficient of the material, µ a , which is the inverse of the optical penetration depth, δ, which is in turn a measure of the distance the light travels until it decays to 1/e of its initial optical intensity.…”

“…With such a small optical penetration depth, the evanescent field is able to interact with the environment very close to the interface of the two materials, and well below the optical and acoustic diffraction limits. The optical properties of materials or particles within this range may perturb the field or otherwise alter its generation, which interaction can be detected by a variety of methods 3,5,6,10,15,17,18,21,23,[25][26][27][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][84][85][86][87][88][89][90][91][92][93][94][95] .…”

“…This family includes, but is not limited to, total internal reflection photoacoustic spectroscopy (TIRPAS), optical tunneling photoacoustic spectroscopy (OTPAS), and surface plasmon resonance photoacoustic spectroscopy (SPRPAS). The interested reader should refer to the following references for derivations of the equations used for TIRPAS 5,6,18,23,25,26,[33][34][35][43][44][45][46][47] , PAS/TIRPAS refractometry 18 , and OTPAS 6 . In each case, the photoacoustic effect is generated through a different excitation mechanism than simple transmittance through a prism; for instance, in TIRPAS, the light is evanescently coupled through a prism/substrate/sample interface into the chromophores (which could include the sample material itself, or guest molecules within the sample), whereas in SPRPAS, the primary mode of excitation is instead through the absorption of a surface plasmon, which is a secondary E-M wave created when the energy of the evanescent field is transferred into the electron cloud of a metal layer deposited on the prism surface.…”