Laser-induced copper deposition from solution is accompanied by the evolution of two types of gas objects that differ considerably in the geometric sizes of bubbles, optical properties and effects on ...the copper deposition process.
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•We proposed laser-induced synthesis of Raney-like copper-based nanocatalysts.•Their catalytic activity towards homo- and cross-coupling reactions was studied.•Growth of such ...copper-based particles can be controlled by adding phenanthroline.•It is possible to manage the course of the catalytic reaction by changing their size.
In this work, we propose the promising approach that provides conditions for laser-induced ex situ synthesis of Raney-like copper-based nanostructured catalysts. Their catalytic activity and selectivity were investigated in Cu-catalyzed acetylene homo-coupling, Pd/Cu-catalyzed the Sonogashira cross-coupling and Cu-catalyzed azide-alkyne cycloaddition (CAAC). It was found that the growth of particles generated within the focus of the laser beam can last even if laser irradiation is off and can be controlled by adding phenanthroline to the reaction mixture as the stabilizing ligand or by increasing its temperature and concentration. Particle size of the synthesized copper-based catalysts significantly affects the reaction selectivity. Thus, it is possible to manage the course of the catalytic reaction towards formation of either homo-coupling or cross-coupling products by changing the size of the catalytically active copper-containing particles produced during laser-induced synthesis.
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•Raman spectroscopy and GCMS revealed signs of the originals of the Russian avant-garde.•Spectral Results are confirmed by GCMS and X-ray methods.•Signs of forgeries were revealed in ...the same way.•In the paintings of the Russian avant-garde of the 20th century, ZnO was used, but not TiO2.•A brief historical analysis of the colors of the Russian avant-garde artists of the 20th century is made.
The paper describes the results of using Raman spectroscopy to study the canvases of Russian avant-garde artists. The study aimed to identify stable signs of paints for the recognition of counterfeits. The subject of the research was zinc white as a component of paints used by the 20th-century Russian avant-garde. Temporal changes occurring with them are due to chemical reactions of organic paint components with whites and with each other. The study shows that Raman spectroscopy is the most sensitive method for detecting ZnO time markers. Its results are compared with the results of pyrolysis–gas chromatography, mass spectrometry, and X-ray analysis of paints from paintings from the Russian avant-garde of the early, middle, and late twentieth century. The study results demonstrate that the paint compositions of the early and late 20th Century have significant similarities. The result of their aging is the appearance of products of thermal desorption and pyrolysis in the form of a homologous series of alcohols and aromatic hydrocarbons formed during the destruction and oxidation of oleic, linoleic, linolenic, palmitic, stearic acids, and/or azelaic acid. These acids are found in flaxseed oil. Zinc white of the early 20th century contains significant additions of gypsum. The composition of the components of mid-century paints is much less diverse. Genuine paintings contain homologous series of fatty acids sorbed on zinc oxide. The paper analyzes historical reasons for this phenomenon. The research shows that one of the stable signs of falsification is the use of titanium white and organic catalysis products based on them. The results of gas chromatography and mass spectrometry and Raman spectroscopy are supplemented by X-ray phase and X-ray fluorescence analysis. The paper provides detailed reference data on the spectra of Raman light scattering, thermal desorption, and pyrolysis of paints of the studied canvases and shows the differences in the mass spectra of genuine paintings and falsifications.
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•Electronic spectra of the copper(II) halide complexes in acetonitrile were obtained.•Stability constants of the copper(II) halide complexes were calculated.•The lowest-energy forms ...of copper(II) halide complexes were determined.•Copper(II) coordination number decreases upon increase the number of halide ions.•Experimental electronic absorption spectra are consistent with TD-DFT calculations.
The results of spectrophotometric study and quantum chemical calculations for copper(II) chloro- and bromocomplexes in acetonitrile are reported. Electronic spectra of the individual copper(II) halide complexes were obtained in a wide spectral range 200–2200 nm. Stability constants of the individual copper(II) halide complexes in acetonitrile were calculated: log β1 = 8.5, log β2 = 15.6, log β3 = 22.5, log β4 = 25.7 for CuCln2−n and log β1 = 17.0, log β2 = 24.6, log β3 = 28.1, log β4 = 30.4 for CuBrn2−n. Structures of the studied complexes were optimized and electronic spectra were simulated using DFT and TD-DFT methodologies, respectively. According to the calculations, the more is the number of halide ligands the less is coordination number of copper ion.
Catalytic actions of aluminum chloride on laser-induced liquid-phase copper deposition process were studied. Copper deposition experiments in aqueous solutions containing aluminum chloride upon 532 ...nm laser irradiation at different line deposition rate were performed. The influence of pH on the deposition rate and topology of the deposited copper microstructures was investigated. Enhanced rate of copper reduction in aluminum chloride solutions was observed. High purity copper microstructures with good electrical conductivity were obtained.
The method of laser-induced chemical deposition of metal from solution was applied in the continuous in situ laser generation of metal copper catalysts for model organic synthesis reactions. The gas ...phase products producing during laser-induced copper deposition were analyzed by gas mass spectroscopy whereas solutions used for the copper deposition were investigated before and after laser irradiation using chromato-mass and NMR spectroscopy. It was found out that the catalysis of the studied organic reactions by metal catalysts generated during laser deposition process occurs only upon laser irradiation of the reaction mixture, in turn, the copper structures deposited under laser light exhibit no catalytic activity.
Ultrafast excited-state dynamics of CuCl4 2– in acetonitrile is studied by femtosecond broadband transient absorption spectroscopy following excitation of the complex into all ligand-field (LF or ...d–d) states and into the two ligand-to-metal charge transfer (LMCT) states corresponding to the most intense steady-state absorption bands. The LF excited states are found to be nonreactive. The lowest-lying 2E LF excited state has a lifetime less than 150 fs, and the lifetimes of the second (2B1) and the third (2A1) LF excited states are 1 and 5 ps, respectively. All three LF states decay directly into the ground 2B2 state. Such significant differences in excited-state decay time constants were rationalized computationally through time-dependent density functional theory (TD-DFT) computations. TD-DFT mapping of the relaxation pathway along the symmetric Cl–Cu–Cl umbrella bending vibration gives evidence for a conical intersection between the 2E excited state and the ground 2B2 state. The LMCT states decay within 200 fs with the primary deactivation mode consistent to be Cu–Cl stretch. A fraction of the CuCl4 2– complexes excited into the LMCT states undergoes ionic dissociation to form products that survive longer than 1 ns. The remaining fraction undergoes internal conversion, which can be viewed as back electron transfer, populating the lower vibrationally hot LF states. The LF states populated from the LMCT states exhibit the same lifetimes as the Franck–Condon LF states and likewise decay directly into the ground state.
When establishing the age of a document using spectral methods, the result is influenced not only by the storage conditions, but also by the methods of measuring the spectra and mathematical ...processing of the results. This work analyzes the influence the modes of measuring Raman spectra have on the result of measuring the writing composition spec-tra. The analysis area includes the correlation coefficients of the full spectral matrices as a criterion for the reliability of the determination date. The influence of focusing accuracy, correctness of subtraction of the baseline, sample irradiation time, and varying the number of repetitions is investigated. In the study, chemometric tools for the analysis of Raman spectra were also applied. The influence of mathematical spectra processing shows that the components PC4, P5, and PC6 are most closely related to the shelf life, although they do not make the maximum contribution to the variance in the system. Taking into account all the requirements for measuring spectra, the PCA method applied to the Raman spectra of writing compositions allows clustering samples by manufacturer’s brands and by the sample shelf life.
When establishing the age of a document using spectral methods, the result is influenced not only by the storage conditions, but also by the methods of measuring the spectra and mathematical ...processing of the results. This work analyzes the influence the modes of measuring Raman spectra have on the result of measuring the writing composition spec-tra. The analysis area includes the correlation coefficients of the full spectral matrices as a criterion for the reliability of the determination date. The influence of focusing accuracy, correctness of subtraction of the baseline, sample irradiation time, and varying the number of repetitions is investigated. In the study, chemometric tools for the analysis of Raman spectra were also applied. The influence of mathematical spectra processing shows that the components PC4, P5, and PC6 are most closely related to the shelf life, although they do not make the maximum contribution to the variance in the system. Taking into account all the requirements for measuring spectra, the PCA method applied to the Raman spectra of writing compositions allows clustering samples by manufacturer’s brands and by the sample shelf life.
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