High-Energy Chemistry and Processing in Liquids

2016年から日本化学会新領域研究グループ「液相高エネルギー化学の新展開」で大学、国立研究機関の研究者らが協力し、年会特別企画の開催などを行ってきた。その活動のまとめとして、この度、Springer Nature社として契約して"High-Energy Chemistry and Processing in Liquids"というタイトルで書籍を出版することになった。この書籍はPart I High-energy chemistry and processing of metals (5 chapters), Part II High-energy processing of nonmetals (7 chapters), Part III High-energy chemistry of nonmetals (6 chapters)の３部構成になっており、佐伯はPart I の一部を"Laser-induced particle formation in a solution of precious metal ions: its application to separation of precious metals from industrial waste and fundamental study on its reaction mechanism.というタイトルで分担執筆する

Application of MCR analysis to time-resolved LIBS measurement using liquid jet sampling method

In LIBS measurement of a solution of metal ions, the emission spectrum shows very complicated structure, where electronic transition bands of metal ions and neutrals are overlapped each other. If we know kinds of the metal ions prior to the LIBS measurement, we assign the electronic transition bands based on spectroscopic database. On the other hand, when there is no information, the assignment becomes tough work. In this study, focusing on similarity of emission decay from the same metal species, we design to classify the emission bands into groups using multivariate curve resolution by alternating least-squares (MCR-ALS). Although the MCR-ALS method was applied to the LIBS analysis in order to explore kinetics of ionic recombination and molecular formation within the plasma, there has been few applications on the LIBS. In this work, we observed time-resolved LIBS spectra of an aqueous solution containing Mo and Sr ions by ultra-thin liquid jet sampling method, and analyzed a series of the LIBS spectra using the MCR-ALS. Though the analysis, we discuss possibility to deconvolute a complicated LIBS spectrum into the groups of emission bands of each metal species.11th International Conference on Laser-Induced Breakdown Spectroscop

Ab initio study of palladium dichloride PdCl2 and its anion PdCl2-

We theoretically study geometries and electronic structures of palladium dichloride PdCl2　and its anion PdCl2-, using the MP2 (or CASPT2) and MRCI methods. Spin singlet and triplet PdCl2 and doublet PdCl2- are investigated. As a result of geometry optimization, both linear and bent geometries are obtained for singlet and triplet PdCl2 and only linear geometries for doublet PdCl2-; it is found that there are two minima (linear and bent) on the ground 11A1 state for singlet PdCl2 and the bent minimum is energetically lowest in neutral PdCl2. It is of great importance to note that the total energies of all calculated states for linear PdCl2- are predicted much lower in energy than the ground 11A1 state for linear singlet PdCl2, indicating that the PdCl2- anion is electronically stable. The equilibrium electron affinity of bent 11A1 PdCl2 is calculated 4.61 (4.10) eV with the MRCI (MRCI + Q) method

Photoinduced gold recovery mediated by isopolymolybdate in strongly acidic HCl/NaCl solutions

The laser-induced formation of gold nanoparticles (AuNPs) was studied in hydrochloric acid solutions containing isopolymolybdate. Aqueous solutions of HAuCl4 (0.5 mM) in HCl (0.1–1.0 M)/NaCl media containing ethanol (0.5% v/v) were irradiated with 355 nm laser pulses in the absence or presence of molybdate. The reaction progress was probed by UV-vis spectroscopy. Without molybdate, the formation of AuNPs is significantly hindered because a large excess of Cl− renders the AuCl4− precursor resistant to direct photoreduction with ethanol. The incorporation of molybdate into solution effectively mediates the photoinduced formation of AuNPs in 0.1–0.5 M HCl. For this range of acidity, photoirradiation generates the molybdenum blue (MB) species from the reaction of photoexcited Mo36O1128− (polyoxoanions) with ethanol, followed by the reduction of AuCl4− with the MB species. At a higher acidity, the formation of AuNPs is virtually undetectable because the MB species are no longer generated due to the absence of anionic molybdate precursors

Ab initio MRCI study on potential energy surfaces for double Cl loss from the palladium tetrachloride anion PdCl42-

We theoretically study double Cl loss from the palladium tetrachloride anion PdCl42- using the ab initio MRCI method. The double Cl loss is probably a significant process in the laser-induced particle formation of Pd in aqueous/EtOH solution which was proposed recently by Saeki et al. (M. Saeki et al., J. Phys. Chem. C 123 (2019) 817). It is predicted that the wave packet created on excited potential energy surfaces (PESs) by the UV irradiation at 266 nm temporally propagates on the PESs and finally spreads over a flat region, where neutral Cl and anionic Cl- are generated

Detection of Gadolinium in Surrogate Nuclear Fuel Debris Using Fiber-Optic Laser-Induced Breakdown Spectroscopy under Gamma Irradiation

Fiber-optic laser-induced breakdown spectroscopy (FO-LIBS) was applied to a qualitative and quantitative analysis of gadolinium (Gd) in mixed oxide samples, simulating nuclear fuel debris in the damaged reactors of the Fukushima Daiichi Nuclear Power Station. The surrogate debris was prepared from mixed oxide materials containing Gd2O3, with varying Gd concentrations. The emission spectra of the surrogate debris show that the optical emission lines at 501.5 nm and 510.3 nm are suitable for Gd detection in the nuclear fuel debris. LIBS measurements were further performed under gamma irradiation (0–10 kGy/h), resulting in a decrease in spectral intensities due to radiation-induced damage to the optical fiber. For quantification of Gd, robust calibration curves against gamma irradiation were established from the intensity ratio of Gd (501.5 nm)/Ce (474.5 nm) emission lines, yielding the limits of detection for Gd in the range of 0.03–0.08 wt%. These results demonstrate that FO-LIBS is a potential tool for in situ and remote analysis of nuclear fuel debris

Ab initio MRCI study on potential energy curves for a single Cl loss from the palladium tetrachloride anion PdCl42-

We theoretically investigate a single Cl loss from the PdCl42- anion, which is a candidate for key processes in the laser-induced particle formation of Pd in aqueous/EtOH solution proposed recently by Saeki et al. (M. Saeki et al., J. Phys. Chem. C 123 (2019) 817). We calculate low-lying potential energy curves (PECs) of PdCl42- as a function of a Pd-Cl bond length with the MRCI method. It is found that PdCl42- is excited to a 1Eu state by UV irradiation, followed by a Pd-Cl bond elongation on the repulsive 21A1 and/or 21B1 PECs, leading adiabatically to the Cl- formation

Spectral Decomposition of LIBS Dataset using Multivariate Curve Resolution Approach

Laser Induced Breakdown Spectroscopy (LIBS) has been considered as powerful technique that can able to monitor molten debris, which arose from the accident at Fukushima Daiichi Nuclear Power Station in 2011. Although the LIBS is a point measurement technique, it has been used as elemental surface mapping technique in many fields, because it allows user to realize fast spatial scanning without any sample preparation. However, depending on spatial resolution of measurement and investigating area, it is necessary to carry out large number of measurements. Due to the size and complexity of the dataset, analysis of such dataset is challenging and it requires considerable computational effort. Therefore, various strategies and methods have been proposed to obtain qualitative and quantitative information from the dataset. In this paper, we will focus on Multivariate Curve Resolution – Alternating Least Squares (MCR-ALS) approach to obtain elemental distribution of a simulated fuel debris sample.Symposium on Applications of Advanced Measurement Technologie