• Asian Journal of Atmospheric Environment
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• v.9 no.1
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• pp.86-90
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• 2015

Temperature was considered to estimate the minimum detectable absorption coefficient of aerosol particles from photothermal spectroscopy. Light energy absorbed by subsequent emission from the aerosol results in the heating of the aerosol sample and consequently causes a temperature change as well as changes in thermodynamic parameters of the sample. This thermal effect is the basis of photothermal spectroscopy. Photothermal spectroscopy has several types of techniques depending on how the photothermal effects are detected. Photothermal interferometry traces the photothermal effect, refractive index, using an interferometer. Photoacoustic spectroscopy detects the photothermal effect, sound wave, using a microphone. In this study, it is suggested that the detection limit for photothermal spectroscopy can be influenced by the introduction of a slip correction factor when the light absorption is determined in a high temperature environment. The minimum detectable absorption coefficient depends on the density, the specific heat and the temperature, which are thermodynamic properties. Without considering the slip correction, when the temperature of the environment is 400 K, the minimum detectable absorption coefficient for photothermal interferometry increases approximately 0.3% compared to the case of 300 K. The minimum detectable absorption coefficient for photoacoustic spectroscopy decreases only 0.2% compared to the case of 300 K. Photothermal interferometry differs only 0.5% point from photoacoustic spectroscopy. Thus, it is believed that photothermal interferometry is reliably comparable to photoacoustic spectroscopy under 400 K.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2465-2470
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• 2007

We have analyzed the three-dimensional thermal conduction in anisotropic materials using nonsymmetric-Fourier transforms. And a complete theoretical treatment of the photothermal deflection spectroscopy has been performed for thermal conductivity measurement in anisotropic medium. Thermal conductivity tensor was determined by the deflection angle and phase angle with the relative position between the heating and probe beams. The influence of the parameters, such as modulation frequency of the heating beam, the thermal conductivity tensor, was investigated.

• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.11-13
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• 1997

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2795-2799
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• 2013

Irradiation of gold nanorods (GNRs) with laser light corresponding to the longitudinal surface plasmon oscillation results in rapid conversion of electromagnetic energy into heat, a phenomenon commonly known as the photothermal effect of GNRs. Herein, we propose a facile strategy for increasing the photothermal conversion efficiency of GNRs by integration to form graphene oxide (GO) nanocomposites. Moreover, conjugation of iron oxide (IO) with the GO-GNR nanohybrid allowed magnetic enrichment at a specific target site and the separated GO-IO-GNR assembly was rapidly heated by laser irradiation. The present GO-IO-GNR nanocomposites hold great promise for application in various biomedical fields, including surface enhanced Raman spectroscopy imaging, photoacoustic tomography imaging, magnetic resonance imaging, and photothermal cancer therapy.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2078-2086
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• 2003

As technology advances with development of new materials, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. The measurement of thermal properties can be done in a non-contact way using photothermal displacement spectroscopy. In this work, the thermal diffusivity was measured by analyzing the magnitude and phase of deformation gradient. We proposed a new data analysis method based on the real part of deformation gradient as the pump-probe offset value. As the result, compared with the literature value, the measured thermal diffusivities of materials showed about 3 % error.

• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.153-157
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• 1999

The dependence of the absorption edge of wurtzite $Al_xGa_{1-x}N$ on alN mole fraction has been studied. The AlN mole fraction was varied from 0 to 1. The absorption coefficients at room temperature were determined by transmission and photothermal deflection spectroscopy. Photothermal deflection spectroscopy can be applied to determine the low absorbance values. From the results, the effective bandgaps of $Al_xGa_{1-x}N$ alloys were determined by choosing corresponding photon energies of the positions of the absorption coefficient of $6.3\times10^4\textrm{cm}^{-1}$ at the absorption curves of the $Al_xGa_{1-x}N$ alloys. From the energy position of the absorption coefficient versus AlN mole fraction, a bowing parameter of 1.3eV was determined. The bowing parameter agreed quite well with the measured effective bandgaps of AlGaN alloys.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.47-53
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• 2001

As the technology has developed and new materials have been produced, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. This measurement can be done in a non-contact way using photothermal displacenent spectroscopy. In this study, photothermal displacement method was used to measure the thermal diffusivity quantitatively. The specimens used in this study were the pure materials. The Ar-ion laser was used as an energy source and the periodical deformation induced by this pump laser was detected by the He-Ne laser. The magnitude and the phase angle of deformation gradient were measured. The thermal diffusivity was obtained by analyzing the phase angle of deformation gradient. As the result, comparing with the literature value, the thermal diffusivities of materials measured were showed about 2% error.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.318-324
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• 2003

A time-resolved probe beam deflection (PBD) technique was employed to study the energy relaxation dynamics of photofragments produced by photodissociation of $CH_3I$ at 266 nm. Under 500 torr argon environment, experimental PBD transients revealed two energy relaxation processes; a fast relaxation process occurring within an acoustic transit time (less than 0.2 ㎲ in this study) and a slow relaxation process with the relaxation time in several tens of ㎲. The fast energy relaxation of which signal intensity depended linearly on the excitation laser power was assigned to translational-to-translational energy transfer from the photofragments to the medium. As for the slow process, the signal intensity depended on square of the excitation laser power, and the relaxation time decreased as the photofragment concentration increased. Based on experimental findings and reaction rate constants reported previously, the slow process was assigned to methyl radical recombination reaction. In order to determine the rate constant for methyl radical recombination reaction, a theoretical equation of the PBD transient for a radical recombination reaction was derived and used to fit the experimental results. By comparing the experimental PBD curves with the calculated ones, the rate constant for methyl recombination is determined to be $3.3({\pm}1.0)\;{\times}\;10^6\;s^{-1}torr^{-1}$ at 295 ± 2 K in 500 torr Ar.

• Clean Technology
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• v.26 no.4
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• pp.251-256
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• 2020

The biocompatibility and plasmonic properties of Au nanoparticles make them useful for photothermal therapy, drug delivery, imaging, and many other fields. This study demonstrated a novel, facile, economic, and green synthetic method to produce gold nanoparticles. Gold nanoparticles (AuNPs) with spherical and triangular shapes were effectively synthesized using only Schisandra chenesis fruit extract as the capping and reducing agent. The shape of the AuNPs could be engineered simply by adjusting the molar concentration of HAuCl4 in the reaction mixture. The as-synthesized AuNPs were characterized using UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and energy dispersive X-ray analysis (EDXA). This study revealed that by using the HAuCl4 concentration in the AuNP synthesis, the shape and size of the AuNPs could be controlled by the concentration of HAuCl4 and Schisandra chinensis fruit extract as a surfactant. The as-synthesized AuNPs samples had sufficient colloidal stability without noticeable aggregation and showed the predominant growth of the (111) plane of face-centered cubic gold during the crystal growth. The catalytic efficiency of the AuNPs synthesized using Schisandra chenesis fruit extract was examined by monitoring the catalytic reduction of 4-nitrophenol to 4-aminophenol using Ultraviolet-visible spectroscopy (UV-Vis spectroscopy). The synthesized AuNPs showed good catalytic activity to reduce 4-nitrophenol to 4-aminophenol, revealing their practical usefulness.

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.574-578
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• 1993

Laser-induced photoacoustic spectroscopy (LIPAS), which utilizes the photothermal effect that results from nonradiative relaxation of excited state molecules, was used in the speciation analysis of the complexes of neodymium(III) and water soluble synthetic polyelectrolyte, poly methacrylic acid (PMAA), in 0.1 M $NaClO_4$ at pH of 6.0. The minimum detection limit of Nd(III) by LIPAS was $5.O{\times}10^{-6}$ M. Experiment was carried out at low concentration ratio of Nd(III) to PMAA to assure that 1 : 1 complexes predominate. The bound and free Nd(III) species were characterized by measuring nonradiative relaxation energy of the excited states $(^2GM{7/2}\;and\;^4G_{5/2})$ to the metastable state $(^4G_{3/2})$. Two species were quantified by deconvolution of the mixed spectrum using their respective reference spectra. The conditional stability constant measured by LIPAS was 5.52 L$mol^{-1}$.