Laser-induced Photoacoustic Spectroscopy Research Articles

Hypersensitive Transition of Nd(III) Complexes in Liquids Detected by Pulsed-Laser-Induced Photoacoustic Spectroscopy

Laser-induced photoacoustic (PA) spectroscopy for the spectral measurements of extremely weak absorption such as a forbidden transition of lanthanide ions in liquids has been established. In spectroscopy, a pulsed Nd:YAG laser connected with a MOPO series optical parametric oscillator which emits a broad spectrum covering UV and visible regions is used as the excitation source, and the induced PA signals are detected by an optimized PA piezoelectric transducer. The absorption spectra of trivalent lanthanide ions (\(\text{ Pr}^{3+}, \text{ Ho}^{3+}\), and \(\text{ Nd}^{3+})\) in aqueous solutions have been obtained by the detection system with a detection-limit absorbance of \(1.3\times 10^{-5}\,\text{ cm}^{-1}\) at room temperature. In addition, the effects of different binding environments on the band shapes and oscillator strengths of the hypersensitive transitions of \(\text{ Nd}^{3+}\) ions, i.e., \(\text{ Nd}(\text{ CH}_{3}\text{ COO})_{3}\)\(\cdot \)\(\text{ H}_{2}\text{ O}\) dissolved in \(0.1\,{\text{ mol}} \cdot \text{ l}^{-1}\) acetic acid and \(\text{ Nd(3-butanedione)}_{3}{\cdot } 2\text{ H}_{2} \text{ O}\) dissolved in triglycol compared with \(\text{ NdCl}_{3}\) in \(0.1\,{\text{ mol}}\cdot \text{ l}^{-1}\) hydrochloric acid, are observed. The results show that the chemical environment around the lanthanide ions has great impact on 4f–4f transitions, which is rationalized as the impact in terms of ligand (or solvent) special structures and coordination properties.

Resonant photo-acoustic detection of carbon monoxide with UV Laser at 213 nm

A trace-gas sensor for carbon monoxide based on Pulsed Laser-Induced Photo-Acoustic Spectroscopy (PLIPAS) in conjunction with laser excitation wavelength of 213 nm was designed, fabricated and tested for the first time. PLIPAS-based sensor with different cell geometry was employed to enhance the sensitivity down to 58 ppbV level. The parametric dependence of the PLIPAS signals on CO gas concentration, buffer gas (Ar, O2 and He) concentration, laser pulse energy was studied and Ar proved to be better than O2 and He in terms of enhancing the sensitivity of the system. The signal-to-noise ratio and limit of detection have been quantified for different experimental conditions. This study proves that PLIPAS-based CO gas sensor is a reliable gas-leak detection system with high sensitivity and selectivity. Hence this sensor can be employed for pollution monitoring and detection of CO in a noisy environment.

ChemInform Abstract: Laser-Induced Photoacoustic Spectroscopy for the Speciation of Transuranic Elements in Natural Aquatic Systems

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Laser-induced photoacoustic spectroscopy investigation of colon phantom tissue

This paper discusses laser-induced photoacoustic investigations; it concerns a non-destructive technique for the determination of the thermal diffusivity of colon phantom tissue employing open photoacoustic cell configuration.

Application of Laser-Induced Photoacoustic Spectroscopy for Determination of Plutonium Concentration in Nuclear Waste Solutions

Laser-induced photoacoustic spectroscopy was used in a quantitative analysis of Pu in HNO3 medium. Plutonium was quantitatively oxidized to Pu(VI) using Ce(IV). The photoacoustic measurement of Pu(VI) with maximum absorption at 830.5 nm was subsequently performed to determine the concentration. The photoacoustic signal was linearly proportional to the Pu(VI) ion concentration. The detection limit of Pu(VI) was estimated to be 0.5 microg mL(-1) (3sigma) in 3 M HNO3. By the proposed method, Pu concentration was successfully determined in a nuclear waste solution for use in nuclear materials management.

Time-resolved photoacoustic spectroscopy using fiber Bragg grating acoustic transducers

Abstract An acoustic transducer based on a fiber Bragg grating (FBG) is presented and characterized for use in time-resolved laser-induced photoacoustic spectroscopy (PAS) on solid samples. The photoacoustic wave was generated by pulsed laser excitation of immobilized carbon black or erbium oxide powder, and detected by recording either the transmission or reflection spectrum of a clamped fiber Bragg grating (FBG). The characterization of the FBGs photoacoustic response is based on the experimental comparison with a static lateral strain source and on theoretical analysis using the piecewise-uniform approach to photoelastic theory. The temporal resolution of the response is determined by the arrangement of the FBG with respect to the source of the acoustic wave and is better than 150 ns, as was verified in a deconvolution analysis. The method has not only a fast time response but also is simple, inexpensive, and accurate as indicated by the good agreement of the experimental photoacoustic spectrum with previous measurements.

Technetium(VII) sulfide colloid growing observed by laser-induced photoacoustic spectroscopy

Particle growing processes were investigated for technetium(VII) sulfide (Tc2S7) colloids produced in a mixture of Na2S and TcO4 - solutions by laser-induced photoacoustic spectroscopy (LPAS). Analysis of the LPAS signal intensities indicated that the particle size increased in the solution with an increase of standing time, while the number of particles remained constant. It was revealed that the size of colloid particles increased by deposition of Tc2S7 on the particle surfaces, not by coagulation of colloid particles. The formation mechanism and growing process of the colloids are discussed based on the LaMer model, which deals with nucleation processes.

A spectroscopic study of the hydrolysis, colloid formation and solubility of Np(IV)

The hydrolysis, colloid formation and solubility of Np(IV) are investigated in aqueous HClO4-NaClO4solutions (log [H+] = 0 to -2.5) by absorption spectroscopy in the wavelength range of 680-1000 nm. Applying Laser induced photoacoustic spectroscopy (LPAS) in the range of 680-760 nm, the study is extended to low Np(IV) concentrations of 10-6mol/l in DClO4-NaClO4-D2O solutions up to log [D+]=-3.3. Laser induced breakdown detection (LIBD) demonstrates the formation of Np(IV) colloids when the Np(IV) concentration exceeds the solubility of Np(OH)4(am) at given pH. The simultaneous decrease of the Np(IV) absorption bands at 723 and 960 nm cannot be ascribed to the formation of the mononuclear complex Np(OH)3+as assumed in the literature. It is found to be caused by polynucleation. In undersaturated Np(IV) solutions below 10-4mol/l, the position and intensity of the absorption maximum at 723 nm are practically insensitive to the pH change. In oversaturated solutions the absorption band decreases significantly. The spectroscopically determined pH-dependent equilibrium concentration of mononuclear Np(IV) species above freshly formed solid or colloidal Np(IV) particles indicates that Np(OH)22+is the predominant species in the pH range of 1.5-3. This finding is in agreement with the Np(IV) hydrolysis constants reported in the literature from a solvent extraction study with239Np(IV) trace concentrations. The solubility product of freshly formed Np(OH)4(am) particles is determined to be logK'sp= -54.4±0.4 in 0.1 M HClO4-NaClO4and logK°sp=-56.5±0.4 (converted toI=0 by applying the SIT).

Cation-cation complexes of PuO2+and NpO2+with Th4+and UO22+

Cation-cation complexes of NpO2+and PuO2+with UO22+and Th4+were studied using laser-induced photoacoustic spectroscopy (LIPAS). An equilibrium constant of 2.4±0.2 M-1was measured at an ionic strength of 6.0 M for the NpO2+· UO22+complex which is in good agreement with previous measurements using conventional absorption spectroscopy and Raman spectroscopy. Equilibrium constants of 1.8±0.9 and 2.2±1.5 M-1were measured for NpO2+· Th4+and PuO2+· UO22+complexes at an ionic strength of 6.0 M, respectively. This is the first time that LIPAS has been used to study cation-cation complexes and the first time that the PuO2+· UO22+cation-cation complex has been reported.

Complex Formation between UO2+ 2 and CO2- 3: Studied by Laser-Induced Photoacoustic Spectroscopy (LIPAS)

Complex Formation between UO²⁺ ₂ and CO^2- ₃: Studied by Laser-Induced Photoacoustic Spectroscopy (LIPAS)

Measurements of Gas Concentrations in a Fluidized Bed Combustor Using Laser-Induced Photoacoustic Spectroscopy and Zirconia Cell Probes

The dynamic combustion behavior of a circulating, fluidized bed boiler (CFB) was studied using two high-speed gas analysis systems during the combustion of coal, pear, and wood chips. Time-resolved concentrations of SO2 and NO were measured by laser-induced photoacoustic spectroscopy (LIPS). A zirconia-cell based probe (lambda-probe), synchronized with the LIPS probe, measured fluctuations between reducing and oxidizing conditions. The two probes were positioned in the same measurement volume on the centerline of the CFB combustion chamber. The purpose of the work was to investigate the behavior of the LIPS in a combustion chamber containing reacting gases in order to extend the previous h-probe measurements to other gas components. Correlations between oxidizing and reducing conditions and gas species concentrations in three locations in the combustion chamber are presented. The best correlations were found in the upper part of the CFB combustion chamber. In some cases the correlation between reducing conditions and the LIPS signal was caused by unburnt hydrocarbons. Average values of [NO] and [SO2] obtained by the LIPS system were compared with the results from a sampling probe connected to on-line analyzers. The measurements of [NO] and [SO2] were disturbed by interfering gases during reducing conditions. During a sufficiently long time of oxidizing conditions, however, reasonable agreement was obtained between LIPS measurements of [NO] and [SO2] and those of the on-line analyzers. On some occasions (low SO2 concentration) the concentration of the OH radical was also measured.

The Chemistry of Actinide Behavior in Marine Systems

Nuclear test explosions and reactor waste releases have deposited an estimated 16 × 1015 Bq of plutonium into the world's oceans. Chemical speciation, oxidation state, redox reactions, and sorption characteristics are integral in predicting solubility of the different actinides, their migration behaviors and their potential effects on marine biota. Transport mechanisms, biosequestration, interactions with carbonate and humic substances and chemical redox and speciation influence migration patterns. Analytical methods such as ultraviolet-visible absorption spectrophotometry, laser-induced photoacoustic spectroscopy and mass spectrometry are utilized to obtain information on the chemical speciation and oxidation states at sub-tracer levels. Predictive computer models has attempted to evaluate the extensive data needed to adequately parameterize the complex, interdependent and continuous processes involved.

Redetermination of the Quantum Yield of Photoisomerization and Energy Content in the K-Intermediate of Bacteriorhodopsin Photocycle and Its Mutants by the Photoacoustic Technique

Data obtained previously in our lab for the quantum yield retinal photoisomerization and the energy content of the K-intermediate formed in the bacteriorhodopsin and its mutants (bR) photocycle are reexamined using time-resolved transient spectroscopy and laser-induced photoacoustic spectroscopy. In the present experiment both nanosecond and subpicosecond laser pulses are used for excitation, with different reference compounds. From these new results it can be concluded that using CoCl2 as a reference compound in the photoacoustic experiment with subpicosecond laser pulses gives a large amount of prompt heat release resulting from multiphoton absorption processes. This results in an overestimated energy content of the K-intermediate of bR and its mutants. Using different reference compounds, the corrected values are 40 ± 10 kJ/mol, which is in agreement with previously reported values. The apparent quantum yield and energy content values (for each of the isomeric compositions) of the mutants D212N, D85N, ...

Stability quotients of neodymium acetate complexes from 20 to 70‡C by laser-induced photoacoustic spectroscopy

The formation of Nd(III) acetate complexes in aqueous solution is studied by laser-induced photoacoustic spectroscopy and spectrophotometry. Stability quotients for the complexes Nd(CH3COO)2+ and Nd(CH3COO)2 and dissociation quotients for acetic acid are determined at 20, 35, 50 and 70‡C in NaClO4 medium of ionic strength 2.2m (2.0M at 20‡C). The 20‡C results are consistent with previous values determined by potentiometry and energy transfer from Tb(III). The temperature dependence of the stability quotients is consistent with the measured enthalpies of reaction at 25‡C.

Laser Induced Photoacoustic Spectroscopy for Analysis of Neptunium(V) Ions under PUREX Process Condition

A laser induced photoacoustic spectroscopy (LIPAS) system has been studied to analyze penta-valent(NpO+ 2) neptunium under PUREX process condition. The detection limit absorptivity of Np(V) in nitric acid is found to be 3.41 × 10−5 cm−1 which is two orders lower than that of conventional absorption spectrophotometry. The intensity of the photoacoustic signal is magnified in proportion to the coexisting uranium concentration. Signals of Np(V) ions in the presence of uranium agree well with signals of Np(V) without uranium when multiplying by the specific heat of the solutions containing uranium. The photoacoustic spectra are measured by a double-cell system.

Detection of Ambient NO by Laser-Induced Photoacoustic Spectrometry Using A2Σ+ − X2Π (0,0) Transitions Near 226 nm

Trace concentrations of NO are detected under ambient conditions by laser-induced photoacoustic spectroscopy. NO is excited via its A2Σ+-X2π (0,0) band with radiation near 226 nm, and the subsequent heat released is monitored by a microphone. Rotationally resolved photoacoustic spectra are recorded and fit with the use of a multiparameter computer simulation based on a Boltzmann distribution. Transition probabilities and rotational energies are used as input parameters. The effect of buffer gas pressure, buffer gas, laser energy, and NO concentration on the PA signal is investigated both experimentally and by model calculations. Limits of detection (LODs) of 1.2, 2.8, and 4.9 ppm are obtained for NO in Ar, N2, and air, respectively. The ultimate sensitivity of this approach is greater with LODs projected in the low-ppb range by utilizing higher laser energies and an improved system design. The results are compared with those of previous studies using complementary laser-based spectroscopic techniques.

Laser Induced Photoacoustic Spectroscopy for Analysis of Neptunium(V) Ions under PUREX Process Condition.

A laser induced photoacoustic spectroscopy (LIPAS) system has been studied to analyze penta-valent(NpO+ 2) neptunium under PUREX process condition. The detection limit absorptivity of Np(V) in nitric acid is found to be 3.41 × 10−5 cm−1 which is two orders lower than that of conventional absorption spectrophotometry. The intensity of the photoacoustic signal is magnified in proportion to the coexisting uranium concentration. Signals of Np(V) ions in the presence of uranium agree well with signals of Np(V) without uranium when multiplying by the specific heat of the solutions containing uranium. The photoacoustic spectra are measured by a double-cell system.

Relationships between Laser Powers and Photoacoustic Signal Intensities of Flavin Adenine Dinucleotide and β-Carotene Dissolved in Solutions

Ar ion laser-induced photoacoustic spectroscopy has been performed on 0.01 µ M flavin adenine dinucleotide in H2O and 0.01 µ M β-carotene in n-hexane where the optical absorption spectroscopy is not applicable. On the basis of the linear relationships between laser powers and photoacoustic signal intensities up to 500 mW, it may be concluded that laser power ranging from 10 to 50 mW is required for the successful observation of photoacoustic signals without any photochemical or photobiological effects.

Ion-exchanger phase photoacoustic spectrometry for trace analysis of metal ions

Laser-induced photoacoustic spectroscopy has been applied to the determination of chromate, uranyl, and Cr(VI) and Fe(II) ions as coloured complexes that were sorbed on ion-exchanger beads. A simple photoacoustic cell has been constructed; it consisted of a fused silica glass tube and an attached cylindrical piezoelectric transducer. A pulsed laser fight at 532 or 355 nm irradiated the ion-exchanger beads that had been collected in the glass tube of the cell. Since a sample material was effectively concentrated on the ion exchanger, the sensitivity was much higher than that in the corresponding photoacoustic spectrometry in a solution state. The lowest detection limit was 0.21 ng/ml Fe for Fe(II)-DPPS (4,7-diphenyl-1,10-phenanthrolinedisulphonate) complex sorbed on QAE-Sephadex gel. Analytical characteristics of the present method are described.

Applications of Photoacoustic Spectroscopy to Speciation of Lanthanide Elements in Aqueous Solutions and of Solid Phase.

Actinide elements in near neutral aqueous solutions are involved in a variety of chemical reactions such as hydrolysis, complexation, redox reaction, sorption and precipitation. Study of these reactions necessitates identification of chemical and physical forms of actinide species (speciation). Photoacoustic spectroscopy (PAS) has been widely used for studying samples in the form of solids, liquids and gases. For actinide elements in solution, laser-induced PAS (LPAS) has been successfully applied in the past several years, and provided valuable information of the speciation and the microscopic chemical behavior(1)(3). However, little progress has been made for sorbed and precipitated actinide species. We have initiated applications of PAS techniques to speciate lathanide and actinide elements in aqueous phase/adsorbent/precipitate systems ; LPAS has been developed for aqueous species, and the ultraviolet-visible-near infrared (UV-VIS-NIR) PAS and Fourier transform infrared (FT-IR) PAS for adsorbed and precipitated species. These techniques all offer the advantages of PAS : a direct non-perturbing detection, minimal sample preparation, versatility in shape of sample, and high sensitivity. As the first step of the applications of PAS to the speciation, we carried out the measurement on photoacoustic spectra of lanthanide solutions and solids. This note focuses on some results of neodymium, intended to illustrate the efficacy of PAS as a versatile technique for lanthanide speciation. The PAS equipments and procedures we applied are briefly described.