Theory of the photoacoustic effect with solids
TL;DR: In this article, a quantitative derivation for the acoustic signal in a photoacoustic cell in terms of the optical, thermal, and geometric parameters of the system is presented. And the theory predicts the dependence of the signal on the absorption coefficient of the solid, thereby giving a theoretical foundation for the technique of photoacoustical spectroscopy.
Abstract: When chopped light impinges on a solid in an enclosed cell, an acoustic signal is produced within the cell. This effect is the basis of a new spectroscopic technique for the study of solid and semisolid matter. A quantitative derivation is presented for the acoustic signal in a photoacoustic cell in terms of the optical, thermal, and geometric parameters of the system. The theory predicts the dependence of the signal on the absorption coefficient of the solid, thereby giving a theoretical foundation for the technique of photoacoustic spectroscopy. In particular, the theory accounts for the experimental observation that with this technique optical absorption spectra can be obtained for materials that are optically opaque.
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TL;DR: The theory for a sensitive spectroscopy based on the photothermal deflection of a laser beam is developed and its implications for imaging and microscopy are given, and the sources of noise are analyzed.
Abstract: The theory for a sensitive spectroscopy based on the photothermal deflection of a laser beam is developed. We consider cw and pulsed cases of both transverse and collinear photothermal deflection spectroscopy for solids, liquids, gases, and thin films. The predictions of the theory are experimentally verified, its implications for imaging and microscopy are given, and the sources of noise are analyzed. The sensitivity and versatility of photothermal deflection spectroscopy are compared with thermal lensing and photoacoustic spectroscopy.
1,267 citations
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TL;DR: In this article, the theory and applications of photo-acoustic (also called optoacoustic) methods belonging to the more general area of photothermal measurement techniques are reviewed, covering excitation of gaseous or condensed samples with modulated continuous light beams or pulsed light beams.
Abstract: This paper reviews the theory and applications of photoacoustic (also called optoacoustic) methods belonging to the more general area of photothermal measurement techniques. The theory covers excitation of gaseous or condensed samples with modulated continuous light beams or pulsed light beams. The applications of photoacoustic methods include spectroscopy, monitoring deexcitation processes, probing physical properties of materials, and generating mechanical motions. Several other related photothermal methods, as well as particle-acoustics and wave-acoustics methods are also described. This review complements an earlier and narrower review [Rev. Mod. Phys. 53, 517 (1981)] that is mainly concerned with sensitive detection by pulsed photoacoustic spectroscopy in condensed matter.
1,183 citations
TL;DR: In this paper, the authors combined thermal wave and thermography to provide a short-time low-frequency phase angle image where non-thermal features can be suppressed using lock-in data analysis.
Abstract: Thermography and thermal wave techniques can be combined to provide in a short‐time low‐frequency phase angle images where nonthermal features can be suppressed. The principle is optical thermal wave generation simultaneously on the whole sample surface and sequential monitoring of all pixels using both thermographic techniques and lock‐in data analysis. Due to parallel stationary excitation one can use low modulation frequencies allowing for a depth range that is of relevance for applications.
638 citations
TL;DR: In this article, the authors extended the theory of photoacoustic effect to include the contribution of mechanical vibration of the sample and solved equations for thermal and acoustic waves in both sample and gas.
Abstract: The theory of the photoacoustic effect is extended to include the contribution of mechanical vibration of the sample. Coupled equations for thermal and acoustic waves are solved in both sample and gas. It is shown that the pressure signal in the gas may be significantly affected by acoustic coupling in the sample, and experimental confirmation of this extended theory is given. The results of the fully coupled treatment are shown to be accurately reproduced by an extension of the Rosencwaig piston model: the pistonlike motion of the gas boundary layer adjoining the sample is superimposed on the mechanical vibration of the sample surface to give a composite piston displacement which then produces the pressure signal in the gas. The composite‐piston model provides relatively simple algebraic results applicable to many cases of physical interest.
451 citations
TL;DR: The promise of constructing multifunctional theranostic nanocomposites based on 2D transitional metal dichalcogenides for multimodal imaging-guided cancer therapy is highlighted, achieving effective tumor ablation in an animal tumor model.
Abstract: Theranostics for in vivo cancer diagnosis and treatment generally requires well-designed nanoscale platforms with multiple integrated functionalities. In this study, we uncover that functionalized iron oxide nanoparticles (IONPs) could be self-assembled on the surface of two-dimensional MoS2 nanosheets via sulfur chemistry, forming MoS2-IO nanocomposites, which are then modified with two types of polyethylene glycol (PEG) to acquire enhanced stability in physiological environments. Interestingly, 64Cu, a commonly used positron-emitting radioisotope, could be firmly adsorbed on the surface of MoS2 without the need of chelating molecules, to enable in vivo positron emission tomography (PET) imaging. On the other hand, the strong near-infrared (NIR) and superparamagnetism of MoS2-IO-PEG could also be utilized for photoacoustic tomography (PAT) and magnetic resonance (MR) imaging, respectively. Under the guidance by such triple-modal imaging, which uncovers efficient tumor retention of MoS2-IO-(d)PEG upon int...
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TL;DR: The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 11, No. 71, pp. 510-528 as mentioned in this paper discusses the production of sound by radiant energy.
Abstract: (1881). LXVIII. Upon the production of sound by radiant energy. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 11, No. 71, pp. 510-528.
264 citations
TL;DR: In this article, the opto- or photo-acoustic effect used in gas analysis has been extended to the study of solids, providing a simple method for obtaining information about optical absorptions and subsequent de-excitations in solids.
247 citations
210 citations
TL;DR: In this paper, a new technique for performing optical spectroscopy on solids has been developed Photoacoustic spectra of cytochrome c and hemoglobin show how this technique can be used to obtain information about optical absorptions and subsequent deexcitations in solid biological materials, particularly those which cannot readily be studied by conventional means.
Abstract: A new technique for performing optical spectroscopy on solids has been developed Photoacoustic spectra of cytochrome c and hemoglobin show how this technique can be used to obtain information about optical absorptions and subsequent de-excitations in solid biological materials, particularly those which cannot readily be studied by conventional means
161 citations