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Plasmonic nanoparticles can be used in photothermal therapy thanks to their ability to generate local heat. The light-to-heat conversion efficiency is crucial for therapeutic and diagnostic applica...

Control over volatile products of metabolic processes in human body in exhaled air is a promising method for noninvasive medical diagnostics. The mid-IR range (2 – 12 mm) is of great interest for diagnostic applications of the exhaled air spectral analysis. Laser optoacoustic spectroscopy is quite attractive for detecting a large set of gaseous substances; however, high-power sources of tunable radiation are required to increase the method sensitivity. We consider the possibility of using a parametric light generator based on a BaGa4Se7 crystal as a broadband tunable mid-IR laser source for laser optoacoustic spectroscopy.

The cis -skew to trans -planar photoisomerization of benzil in the photoexcited state was studied by laser-induced optoacoustic spectroscopy (LIOAS) in a series of normal alkane solvents at room temperature. The structural volume change due to the photoisomerization process has been estimated and compared with the same calculated from the optimized skew and trans structures. The magnitude of the structural volume change is estimated to be 22.9 ± 1.2 mL/mol. This study reveals that an expansion in volume occurs during the photoinduced isomerization process. In non-polar alkane solvents, the estimated volume change has been argued to be free from electrostrictional contribution.

This chapter provides the molecular constants for (003) and (005) states of triatomic HD16O (H16OD) molecule measured using intracavity laser absorption spectroscopy, optoacoustic spectroscopy and theoretical calculation.

Reaction volume changes, ΔVR, enthalpy content, ΔHMLCT, and decay lifetimes, τ2, of the metal-to-ligand charge transfer (MLCT) complex of (2,2‘-bipyridine)tetracyanoruthenate(II) complex, Ru(bpy)(CN)42-, inside the water pools of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles dispersed in n-alkanes, were determined using laser-induced optoacoustic spectroscopy (LIOAS). Emission quantum yields, Φem, of the complex were also determined by steady-state measurements. The enthalpy content of the MLCT state of Ru(bpy)(CN)42- was not dependent on the amount of water inside the reverse micelles (defined as the molar ratio R = [H2O]/[AOT]) and was, within experimental error, similar to that in water. However, the values of τ2 and Φem decrease while those of ΔVR increase as the values of R are incremented from 3 to 10. At the larger R values, τ2, Φem, and particularly ΔVR resemble the values in neat water. These results are interpreted to arise from the type of water involved in the hydrogen bond int...

Laser induced optoacoustic spectroscopy has been used to determine the relative contribution of the intersystem crossing and internal conversion to the non-radiative energy dissipation from the two excited ICT probes p-N,N-dimethylaminobenzonitrile (DMABN), and p-N,N-dimethylaminobenzaldehyde (DMABA) in solvents of different polarity. It is observed that while intersystem crossing is the main non-radiative deactivation process for DMABN in all the solvents studied this is not the case in polar solvents for DMABA.

It is important to identify patients with chronic obstructive pulmonary disease (COPD) and lung cancer in the early stages of the disease. The method of laser opto-acoustic gas analysis, in this case, can act as a promising tool for diagnostics. The material for this study were the gas emission samples collected from patients and healthy volunteers – samples of exhaled air, swabs from teeth and cheeks. A set of material was formed three groups: healthy volunteers, patients with COPD, lung cancer patients. The resulting samples were analyzed by means of laser opto-acoustic gas analyzers: with intracavity location detector (ILPA-1), with extracavity location detector (LGA-2). Presentation of the results in an easy to visual form was performed using the method of elastic maps, based on the principal component analysis. The results of analysis show potentialities of usage of laser optoacoustic spectroscopy application to assess the status of patients with chronic obstructive pulmonary disease and lung cancer.

Hummers method is commonly used for the fabrication of graphene oxide (GO) from graphite particles. The oxidation process also leads to the cutting of graphene sheets into small pieces. From a thermodynamic perspective, it seems improbable that the aggressive, somewhat random oxidative cutting process could directly result in graphene nanosheets without destroying the intrinsic π-conjugated structures and the associated exotic properties of graphene. In Hummers method, both KMnO4 and NO2(+) (nitronium ions) in concentrated H2SO4 solutions act as oxidants via different oxidation mechanisms. From both experimental observations and theoretical calculations, it appears that KMnO4 plays a major role in the observed oxidative cutting and unzipping processes. We find that KMnO4 also limits nitronium oxidative etching of graphene basal planes, therefore slowing down graphene fracturing processes for nanosheet fabrication. By intentionally excluding KMnO4 and exploiting pure nitronium ion oxidation, aided by the unique thermal and kinetic effects induced by microwave heating, we find that graphite particles can be converted into graphene nanosheets with their π-conjugated aromatic structures and properties largely retained. Without the need of any postreduction processes to remove the high concentration of oxygenated groups that results from Hummers GO formation, the graphene nanosheets as-fabricated exhibit strong absorption, which is nearly wavelength-independent in the visible and near-infrared (NIR) regions, an optical property typical for intrinsic graphene sheets. For the first time, we demonstrate that strong photoacoustic signals can be generated from these graphene nanosheets with NIR excitation. The photo-to-acoustic conversion is weakly dependent on the wavelength of the NIR excitation, which is different from all other NIR photoacoustic contrast agents previously reported.

Optoacoustic spectroscopy detection is one of the newest detection methods. It can detect the weak-absorbed specimen with high-sensitivity. In this treatise, the technique is applied to detect the water quantity in oil. There are two spectral absorbing wave bands of water, so the innovation of this project lies in adopting laser sources with two different wave bands. This can effectively strengthen the signal intensity of optic acoustic effect and increase the rate of Signal-to-Noise. Adopting the ARM embedded-system to collect data can help to enormously reduce the hardware bulk of the instrument. This project has adopted the wavelet-analyzing method to fulfill the wave-filtering and noise-cleaning for the experiment result, established the mathematical model. It is proved that the detecting result is validity.

Time-resolved laser-induced optoacoustic spectroscopy (LIOAS) is a sensitive photobaric method for nondestructive probing of materials that monitors the pressure changes induced in a liquid or a solid sample after photoexcitation with a pulsed laser. LIOAS is an interesting tool for investigating photo-induced chemical processes as well as ‘optically silent’ intermediates, i.e., those displaying no changes in absorption or emission. A phenomenological approach to the equations related to this technique is employed and a description is given of the equipment and data handling as well as a few examples of applications of LIOAS to small molecules either in solution or in a solid powder matrix.

One of the challenging problems in the BR cycle is the accurate determination of the photochemical quantum yield for the reaction of BR yielding its early intermediates, J and K. Due to the strong overlap between the absorption spectra of BR and K [1], it is difficult to obtain this yield through optical methods. Sub-ps LIOAS circumvents this problem by measuring the heat stored after excitation with a laser pulse, affording thus the quantum yield of the species storing the energy for a time longer than the heat integration time of the experiment.

This paper contains a review of results of the experimental investigation of linear and nonlinear absorption of atmospheric gases using the methods of multichannel optoacoustic spectroscopy with pulsed visible and IR lasers.

The Doppler-free optoacoustic spectrum of the oxygen-18 species of methanol has been investigated with a CO2 laser. Seventeen coincidences have been found between infrared absorptions of CH183OH and CO2 laser lines. The strongest feature seen, pumped by the 10R(20) CO2 laser line, has two plausible alternative identifications, determined from a parallel high-resolution spectroscopic study of the C-O stretching band. Further experimental tests are suggested to resolve the assignment, and predicted far-infrared laser frequencies are given for the two possibilities.

Optoacoustic spectroscopy (OAS) is based on measuring the OA signal as a function of wavelength of the monochromatic radiation impinging on the sample. In this chapter we consider mainly the general experimental techniques and potentialities of laser OAS of gaseous media.

To get information about the product stabilization within the photosynthetic electron transport chain, it is of interest to measure the heat evolved in the system upon irradiation. The cyanobacterium Synechococcus sp, containing both photosystems PS-i and PS-II, was chosen as the subject of investigation. LIOAS-measurements were performed a) in vivo with intact cells and b) in vitro with isolated PS-II and PS-I particles. In all cases the internal reference for maximal heat production [1] was the same system with inhibited photosynthetic activity. Compared to the conventional photoacoustic spectroscopy (PAS), LIOAS has a better time resolution (< 2 μs) and excludes contributions from modulated photosynthetic oxygen-evolution.

Optoacoustic spectroscopy investigate solid, semi conductor and liquid samples which are strongly or weakly absorbing, or which preclude the use of reflectance or transmission spectroscopy due to scattering of the incident radiation. The material presented in this chapter demonstrates the great potentiality of OAS of condensed media.

Optoacoustic spectroscopy can also be used to solve nonspectroscopic problems, in particular, to measure and control the parameters of laser radiation, to study the thermal properties of various media, to investigate electron-phonon interaction, etc. In this chapter we consider some interesting areas of such nonspectroscopic applications.

Optoacoustic (OA) detection apparatus can be used for analysis of various optical absorbers in very dilute concentrations. Parameters of pulse OA spectroscopy as applied to highly transparent samples are derived allowing to compare the potentialities to these of conventional absorption methods. We consider a frequently used OA device based upon linear thermoelastic OA conversion. Practice of both amplitude and dynamic versions of OA method are discussed. The role of pure solvent contribution is revealed. Useful estimates are provided.

Laser-induced optoacoustic spectroscopy (LIOAS) was applied to the study of 13-cis (13RT), 11-cis (11RT), and all-trans (trRT)-retinal photoisomerization in various n-alkanes. From the analysis of ...

Molecular spectroscopists have studied the absorption of optical radiation for over 100 years, but only in the last five years have experiments come forth on the subsequent relaxation of the molecular excitation to produce heat. By detecting this heat as an acoustic pulse using sensitive microphones and bolometers, the eventual fate of absorbed photons can be followed, both energetically and kinetically. Several examples of the unique information derived from this acoustic method of molecular spectroscopy will be presented.

A method and apparatus that significantly increases the sensitivity and flexibility of laser optoacoustic spectroscopy, with reduced size. With the method, it no longer is necessary to limit the use of laser optoacoustic spectroscopy to species whose absorption must match available laser radiation. Instead, "doping" with a relatively small amount of an optically absorbing gas yields optoacoustic signatures of nonabsorbing materials (gases, liquids, solids, and aerosols), thus significantly increasing the sensitivity and flexibility of optoacoustic spectroscopy. Several applications of this method are demonstated and/or suggested.

(1986). Laser Optoacoustic Spectroscopy. Optica Acta: International Journal of Optics: Vol. 33, No. 11, pp. 1338-1338.