Nonradiative relaxation dynamics of CuCl42- complexes photoexcited into the highest-energy ligand-field electronic state (2A1) is studied in acetonitrile, dichloromethane, and chloroform solvents, as ...well as in acetonitrile-water and in acetonitrile-deuterated water mixtures. Due to ultrafast internal conversion, this excited state directly converts to the electronic ground state in dichloromethane and chloroform. The nonradiative relaxation constant is similar in anhydrous acetonitrile. Addition of water to acetonitrile solutions efficiently quenches the excited ligand-field 2A1 state. The quenching is proposed to be due to the diffusion-controlled formation of an electronically excited pentacoordinated CuCl4H2O2- encounter complex or a short-lived exciplex of similar structure, in which the electronic excitation energy transfers into the O-H stretch of the coordinated H2O molecule. This is followed by the dissociation of the pentacoordinated species, resulting in the reformation of the ground-state CuCl42- and free H2O molecules.
Ultrafast excited-state dynamics of CuCl
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
E LF excited state has a lifetime less than 150 fs, and the lifetimes of the second (
B
) and the third (
A
) LF excited states are 1 and 5 ps, respectively. All three LF states decay directly into the ground
B
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
E excited state and the ground
B
state. The LMCT states decay within 200 fs with the primary deactivation mode consistent to be Cu-Cl stretch. A fraction of the CuCl
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.
The development of an algorithm to automate the process of measuring the magnetic properties of macroscopic objects in motion is an important problem in various industries, especially in ferrous ...metallurgy and at factories where ferrous scrap is a strategic raw material. The parameter that requires work control is the hidden mass fraction of a non-magnetic substance that is present in the ferromagnetic raw material. The solution to this problem has no prototypes. In our work, a simple measuring device and a mathematical algorithm for calculating the mass fraction of the non-magnetic fraction in a strongly magnetic matrix were developed. The device is an inductance coil, in which the angle of the electromagnet losses is related to the mass of the magnetic material moving the coil. The magnitude of the instantaneous values of the lost angle integral was compared with the result of weighing the object on scales. This allowed us to calculate the proportion of the magnetic and non-magnetic fractions. The use of this prototype is herein illustrated. The experimental results of the determination of the magnetic-fractional composition depending on the mass of scrap metal and its bulk and the magnetic characteristics are presented.
Photochemistry of copper(II) monochlorocomplexes in methanol and acetonitrile solutions is studied by UV-pump/broadband deep-UV-to-near-IR probe femtosecond transient absorption spectroscopy. Upon ...255 and 266 nm excitation, the complexes in acetonitrile and methanol, respectively, are promoted to the excited ligand-to-metal charge transfer (LMCT) state, which has a short (sub-250 fs) lifetime. From the LMCT state, the complexes decay via internal conversion to lower-lying ligand field (LF) d–d excited states or the vibrationally hot ground electronic state. A minor fraction of the excited complexes relaxes to the LF electronic excited states, which are relatively long-lived with lifetimes >1 ns. Also, in methanol solutions, about 3% of the LMCT-excited copper(II) monochlorocomplexes dissociate forming copper(I) solvatocomplexes and chlorine atoms, which then further react forming long-lived photoproducts. In acetonitrile, about 50% of the LMCT-excited copper(II) monochlorocomplexes dissociate forming radical and ionic products in a ratio of 3:2. Another minor process observed following excitation only in methanol solutions is the re-equilibration between several forms of the copper(II) ground-state complexes present in solutions. This re-equilibration occurs on a time scale from sub-nanoseconds to nanoseconds.
Nonradiative relaxation dynamics of CuCl
complexes photoexcited into the highest-energy ligand-field electronic state (
A
) is studied in acetonitrile, dichloromethane, and chloroform solvents, as ...well as in acetonitrile-water and in acetonitrile-deuterated water mixtures. Due to ultrafast internal conversion, this excited state directly converts to the electronic ground state in dichloromethane and chloroform. The nonradiative relaxation constant is similar in anhydrous acetonitrile. Addition of water to acetonitrile solutions efficiently quenches the excited ligand-field
A
state. The quenching is proposed to be due to the diffusion-controlled formation of an electronically excited pentacoordinated CuCl
H
O
encounter complex or a short-lived exciplex of similar structure, in which the electronic excitation energy transfers into the O-H stretch of the coordinated H
O molecule. This is followed by the dissociation of the pentacoordinated species, resulting in the reformation of the ground-state CuCl
and free H
O molecules.
Microelectronics industry is growing fast and the rate of new devices' development increases every year. Therefore, methods for simple and high-precision metal coating on dielectrics are needed. ...Existing methods do not allow performing the high-precision metal deposition without using photomasks, while making a photomask for each prototype is a long and expensive process. One of the methods of maskless metal deposition is laser-induced chemical liquid-phase deposition (LCLD). In this work we show the effect of substrate surface type on a result of LCLD. Deposited copper structures were characterized by SEM, EDX and impedance spectroscopy. The results show that laser-induced copper deposition is highly affected by the surface being a homogeneous or composite material. It was found that the deposits with low resistivity and high quality metal localization mostly appear on the two-phase surfaces. In contrast, deposits on one-phase surfaces exhibited poor topology of copper material. Statistical modeling was involved to describe this phenomenon.
•Laser-assisted liquid-phase copper deposition is affected by substrate surface type.•Two-phase surface allows depositing conductive copper lines utilizing laser.•Dispersity of defects on interfaces may be described in terms of statistical modeling.
Copper(II) complexes are extremely labile with typical ligand exchange rate constants on the order of 106–109 M–1 s–1. As a result, it is often difficult to identify the actual formation mechanism ...of these complexes. In this work, using UV–vis transient absorption when probing in a broad time range (20 ps to 8 μs) in conjunction with DFT/TDDFT calculations, we studied the dynamics and underlying reaction mechanisms of the formation of extremely labile copper(II) CuCl4 2– chloro complexes from copper(II) CuCl3 – trichloro complexes and chloride ions. These two species, produced via photochemical dissociation of CuCl4 2– upon 420 nm excitation into the ligand-to-metal-charge-transfer electronic state, are found to recombine into parent complexes with bimolecular rate constants of (9.0 ± 0.1) × 107 and (5.3 ± 0.4) × 108 M–1 s–1 in acetonitrile and dichloromethane, respectively. In dichloromethane, recombination occurs via a simple one-step addition. In acetonitrile, where CuCl3− reacts with the solvent to form a CuCl3CH3CN− complex in less than 20 ps, recombination takes place via ligand exchange described by the associative interchange mechanism that involves a CuCl4CH3CN2– intermediate. In both solvents, the recombination reaction is potential energy controlled.
The simple and cheap method for fabrication of micro-sized electrochemical electrodes was proposed. The porous copper microstructures synthesized by laser-induced metal deposition technique were used ...as an indicator electrode, whereas a bulk polycrystalline copper with similar geometric parameters was used as an etalon electrode. The electrochemical properties of these electrodes were studied by cyclic voltammetry and impedance spectroscopy. The surface of the deposited copper structures was investigated by X-ray photoelectron spectroscopy and atomic force microscopy. An analytical response of the fabricated copper electrode is 15 times higher than those observed for a pure bulk copper. A study of sensory characteristics for hydrogen peroxide and
d
-glucose detection showed that the value of Faraday current at the fabricated copper electrode is 2–2.5 orders of magnitude higher than for etalon one.
In this work we study the influence of
l
-(+)-КNaC
4
H
4
O
6
× 4H
2
O (KNaT) and
l
-H
2
C
4
H
4
O
6
(H
2
T) on the complexation processes occurring during in situ laser-induced catalytic destruction ...of the organic components of the aqueous solutions with formation of the unsaturated hydrocarbons. For that purpose, ATR-FTIR, Raman, IR, and NIR spectroscopy as well as quantum chemical calculations were implemented. It was observed that hydration of T
2−
anion via carboxylate groups is stronger than that via hydroxyl groups. We also established the changes in the spectral characteristics of the absorption bands corresponding to vibrations of T
2−
, HT
−
, and H
2
T, at solid state-liquid and acid-salt transitions, depending on concentration of the solution components and the OH
−
/H
2
T ratio. Finally, it was shown that ethylene is a main product of the catalytic destruction of the copper tartrate complexes.
In this work we demonstrate the role of a ligand in formation of the conductive and electrocatalytically active copper microstructures produced using the in situ laser-induced metal deposition ...technique. For this purpose, the alkaline solutions of different concentrations containing copper(II) chloride and Rochelle salt, which is used as the ligand and exhibits both coordination and reduction properties, were studied by ATR-FTIR, UV–Vis, and Raman spectroscopy. According to spectroscopic studies and theoretical considerations, it was observed that at certain concentrations and proportion of copper(II) chloride and sodium potassium tartrate, and also within pH range between 7 and 13 the components of the plating copper solution form the tartrate copper complex, in which copper ion is coordinated by four hydroxyl groups of the ligand and two hydroxyl groups of the environment. As a result, the laser-induced deposition from solutions, where copper coordination occurs via hydroxyls rather than through other functional groups (e.g. carboxylate), results in the synthesis of the sensory active materials. Furthermore, we figured out that the presence of the reducing agents such as polyols in the plating copper solution also enhances the electrical conductivity and electrochemical characteristics of the resulting copper microdeposits, among which sorbitol displays the most attractive results. Thus, it was shown that the regime of copper coordination in an organic ligand and number of hydroxyl groups in a ligand and a reducing agent directly affect the properties of the synthesized copper microstructures. In addition, the overall results obtained in this study are quite useful for better understanding the mechanisms of the laser-induced metal deposition process, and very perspective for development and design of new non-enzymatic electrochemical sensors and biosensors. Keywords: Rochelle salt, ATR-FTIR, Laser-induced copper deposition, Tartrate copper complex, Quantum-chemical calculations
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