Excitation Of Cu Research Articles

Recent Development of Copper (II) Complexes of Polypyridyl Ligands in Chemotherapy and Photodynamic Therapy.

Cancer is a deadly disease associated with abnormal cell growth and invasion to various parts of the body. Many drugs such as cisplatin and carboplatin have been used for the treatment of cancer over the years. However, a lack of selectivity toward cancer cells and associated side effects with current treatment options has fueled continued efforts throughout the world to find better anticancer drugs. Over the past decades, copper-containing compounds have shown excellent anticancer activity. Cu(II) complexes are well studied and show broad-spectrum pharmacological activity. The redox activity of copper ions contributes to cytotoxic activity in combination with ligands that possess bioactivity. Binding of copper with various types of bidentate, tridentate, and tetradentate ligands can activate the processes of necrosis, apoptosis, and angiogenesis. Copper induces the formation of reactive oxygen species to cleave DNA. Similarly, light-assisted excitation of Cu(II) complexes in the red region of the electromagnetic spectrum helps produce different reactive species, thereby inducing anticancer activity through a photodynamic mechanism. In general, in vivo and in vitro studies have demonstrated that the administration of copper ions is effective against various cancer cell lines. Herein we discuss the past ten years of research into copper complexes of terpyridine-, 2,2'-bipyridine-, and 1,10-phenanthroline-based ligands as potential anticancer agents. The aspects of chemotherapy by redox-mediated pathways and photodynamic therapy using light-assisted excitation are reviewed, with a focus on mechanisms of activity, details of important experimental procedures, as well as drawbacks in the design of copper-containing drugs.

Monovalent copper-mediated UV to NIR luminescence down-shifting in Yb3+-doped glass

Sensitized NIR emission from Yb3+ ions is realized under near-UV excitation of Cu+ and a Cu2+–Yb2+ CTS model is proposed to explain the luminescence down-shifting.

Thermal and spectroscopic characterization of copper and erbium containing aluminophosphate glass.

Thermal, Raman scattering, optical absorption, and photoluminescence characterizations were carried out on aluminophosphate glass containing Cu+/Cu2+ along with near-infrared (IR) emitting Er3+ ions of interest to photonic applications. Material synthesis was carried out by the melt-quench technique wherein Cu+ ions were incorporated at a high concentration by addition of 10 mol% of Cu2O together with SnO. The copper oxide doping was recognized to result in a decrease of the glass transition temperature of the matrix, however Er3+ doping displayed opposite propensity. Raman measurements under 785 nm excitation were consistent with calorimetry data indicating that copper ions modify glass structural features. The degree of copper oxidation during material preparation was assessed quantitatively through the Cu2+ absorption feature around 850 nm. The presence of substantial Cu+ concurred with the significant red shift in the near-ultraviolet glass absorption edge, and was analyzed in the context of optical band gap determinations. An evaluation of the luminescence decay kinetics of Cu+ ions in the presence of Er3+ agreed with a non-radiative energy transfer which appeared more effective for excitation of Cu+ near the glass absorption edge at 400 nm. Such excitation was confirmed to result in the sensitized near-IR emission from Er3+ ions around 1.53 μm of interest to lasers, the telecommunications, and spectral conversion in photovoltaic cells.

Effect of uniform magnetic field on laser-produced Cu plasma and the deposited particles on the target surface

AbstractLaser-produced copper plasma in the presence of variable transverse external magnetic field in air is investigated using optical emission spectroscopy. As the magnetic field increases from 0 to 0.5 T, the intensity of Cu I lines initially increases and then decreases slightly at a 0.5 T. The maximum intensity enhancement of all five Cu I lines occurs at a magnetic field of 0.3 T. The increase in intensity is attributed to an increase in the electron impact excitation of Cu. With increase in magnetic field, the electron density and temperature were found to increase due to increase in the confinement of plasma. The difference in intensity enhancement factor is due to the difference in excitation rate coefficients. The surface morphology of irradiated copper target is also analyzed at 0.3 T magnetic field at which the density is maximum and reveals the formation of Cu/Cu2O/CuO nanoparticles (NPs). More NPs are formed at the peripheral region than at the central region of the ablated crater and is due to the oxidation of Cu atom in the plasma–ambient interface. The larger grain size of nanostructures in the presence of magnetic field is due to an increase in the inverse pulsed laser deposition. The intensity of Raman peak of Cu2O decreases in the presence of magnetic field and that of CuO increases which is more likely due to conversion of Cu2O to CuO. The photoluminescence intensity of CuO increases in the presence of magnetic field due to the phase transformation of Cu2O to CuO in agreement with the result of Raman spectroscopy.

One-Pot Synthesis of Monodisperse Colloidal Copper-Doped CdSe Nanocrystals Mediated by Ligand–Copper Interactions

We report a one-pot synthesis of high-quality colloidal copper-doped cadmium selenide nanocrystals (Cu+:CdSe NCs) by injection of a mixture of copper iodide (CuI) and trioctylphosphine (TOP) into solutions containing preformed CdSe NCs. This method allows NC doping to be separated from nucleation and growth, thereby simultaneously achieving large size tunability, narrow size dispersion, and exclusively copper-based photoluminescence (PL). The copper doping level is affected by both the reaction time and the relative concentrations of the cadmium precursor, CuI, and TOP. A correlation is demonstrated between the copper dopant concentration and the intensities of the characteristic near-IR PL and midgap absorption bands, both associated with metal-to-ligand (conduction band) charge-transfer (MLCBCT) excitation of Cu+ dopants. Mechanistic studies reveal that Cu2–xSe NCs are easily formed as kinetic intermediates under reaction conditions involving substantial copper and that these NCs then act as a copper so...

The use of radiative transition rates to study the changes in the excitation of Cu ions in a Ne glow discharge caused by small additions of H2, O2 and N2

The excitation of Cu+ ions in a Ne glow discharge with small additions of H2, O2 and N2 was studied. Ratios of radiative transition rates between different Cu II levels in a discharge in neon, with and without the molecular gas added, were calculated, and the formalism of transition rate ratio (TRR) diagrams was developed and used to study the changing excitation conditions. Virtually no changes in the excitation of Cu+ ions occur in a neon discharge if nitrogen is added. Additions of hydrogen and oxygen to neon as the discharge gas affect excitation of the 4d, 5s and some other Cu II levels in the vicinity of the ionization energy of neon (21.56eV). Also some lower Cu II levels, excited by radiative decay of those higher energy levels, are affected. The 4p 3P2 level at 15.96eV is enhanced by additions of hydrogen. It was suggested that this enhancement is caused by the asymmetric charge transfer reaction between neutral copper atoms and the H2+ molecular ions.

Spin excitations in the skyrmion hostCu2OSeO3

We have used inelastic neutron scattering to measure the magnetic excitation spectrum along the high-symmetry directions of the first Brillouin zone of the magnetic skyrmion hosting compound Cu$_2$OSeO$_3$. The majority of our scattering data are consistent with the expectations of a recently proposed model for the magnetic excitations in Cu$_2$OSeO$_3$, and we report best-fit parameters for the dominant exchange interactions. Important differences exist, however, between our experimental findings and the model expectations. These include the identification of two energy scales that likely arise due to neglected anisotropic interactions. This feature of our work suggests that anisotropy should be considered in future theoretical work aimed at the full microscopic understanding of the emergence of the skyrmion state in this material.

Multi-structured temporal behavior of neutral copper transitions in laser-produced plasma in the presence of variable transverse static magnetic field

We report on the effect of variable magnetic field on temporal behavior of neutral copper (Cu I) transitions in laser-produced copper plasma at atmospheric pressure using optical emission spectroscopy. In the presence of magnetic field, the intensity of copper atomic lines at 510.5, 515.3, and 521.8 nm gets enhanced due to increase in electron-impact excitation rate. The enhancement factor of the neutral lines is different due to different electron-impact excitation rates. We observed that the Cu I profile consists of two components recorded in the absence of magnetic field and at 0.1 T. At magnetic field of 0.3 T, the appearance of third slow component at delayed time, i.e., 122, 130, and 140 ns for Cu I (521.8, 515.3, and 510.5 nm) is also observed. We demonstrate that the generation of slow component is related to electron-impact excitation of Cu I atom rather than backflow particles and instabilities at atmospheric pressure. The instabilities generated during the plasma deceleration by magnetic field can be reduced in the presence of air at atmospheric pressure which will be applicable to enhance the sensitivity of laser-induced breakdown spectroscopy. The fast component is least affected by the magnetic field due to longer magnetic diffusion time.

Enhanced Photocatalytic Property of Cu Doped Sodium Niobate

We investigate the photocatalytic activity of Cu doped NaNbO3powder sample prepared by the modified polymer complex method. The photocatalytic activity of hydrogen evolution from methanol aqueous solution was improved by Cu 2.6 at% doping. The photocatalytic degradation of rhodamine B (RhB) under visible light irradiation was enhanced in comparison with pristine NaNbO3. Cu introduction improved the adsorption property of NaNbO3, judging from the Fourier transform infrared spectra. Moreover, the ultraviolet light excitation in Cu doped sample would accelerate the mineralized process.

Probing Cu(I) in homogeneous catalysis using high-energy-resolution fluorescence-detected X-ray absorption spectroscopy.

Metal-to-ligand charge transfer excitations in Cu(I) X-ray absorption spectra are introduced as spectroscopic handles for the characterization of species in homogeneous catalytic reaction mixtures. Analysis is supported by correlation of a spectral library to calculations and to complementary spectroscopic parameters.

Hybridization of magnetic excitations between quasi-one-dimensional spin chains and spin dimers in Cu3Mo2O9observed using inelastic neutron scattering

We have studied the exchange interactions and the hybridization effects of two kinds of magnetic excitations in Cu${}_{3}$Mo${}_{2}$O${}_{9}$ by using inelastic neutron scattering. This compound has two magnetic subsystems, i.e., the quasi-one-dimensional (q1D) antiferromagnetic (AF) spin system and the quantum spin dimers. We observe two branches in the magnetic excitations and obtain the magnetic parameters as follows. We evaluate the intrachain interaction ${J}_{4}=4.0$ meV in the q1D AF spin system and the intradimer interaction ${J}_{3}=5.8$ meV in the spin dimers. Applying the interchain mean-field theory (CMF) with the random-phase approximation (RPA), we estimate the mass gap of the q1D AF spin system as 1.2 meV. Using the CMF-RPA theory, the ferromagnetic interchain interaction between the magnetic chain along the $a$ axis and the AF one between the magnetic chains at the center and the corner of the unit cell are estimated to be $\ensuremath{-}{J}_{a}={J}_{\ensuremath{\alpha}\ensuremath{\beta}}=0.19$ meV, respectively. The hybridization parameter, which represents the intersubsystem interaction, has the wave-vector dependence as ${E}_{\mathrm{int}}\mathrm{sin}(\ensuremath{\pi}k)$, where ${E}_{\mathrm{int}}=1.6$ meV and ${\mathit{kb}}^{*}$ denotes the wave vector of magnetic excitation along the ${b}^{*}$ direction. The modulation of the molecular field generated by the magnetic excitation of the q1D AF spin system plays an important role in this hybridization.

Transverse and Longitudinal Excitation Modes in Interacting Multispin Systems

Magnetic excitation in coupled multispin system is studied theoretically focusing on Cu 2 Fe 2 Ge 4 O 13 and Cu 2 CdB 2 O 6 as typical examples of such system. These compounds consist of spin dimer and spin monomer parts and show an antiferromagnetic phase transition at low temperatures due to the spin monomer part. A multispin containing a spin dimer and spin monomers is treated as a basis unit. The multispin forms a spin multiplet and its energy levels are separated into high and low regions reflecting the characteristic energies of the dimer and monomer parts. We regard the system as interacting multispins and apply an extended Holstein–Primakoff theory by introducing bosons for each energy level of a spin multiplet. In the low-energy region, the obtained magnon dispersion and dynamical spin correlation function agree quantitatively with experimental results of inelastic neutron scattering performed in Cu 2 Fe 2 Ge 4 O 13 . Analyzing dynamical spin correlation functions, we find several high-energy modes with longitudinal spin fluctuations peculiar to the coupled spin dimer and spin monomer system. One-magnon Raman scattering is studied to probe such longitudinal modes. Magnetic excitation in Cu 2 CdB 2 O 6 is also studied in the same way.

Neutron inelastic scattering investigation of the magnetic excitations inCu2Te2O5X2(X=Br,Cl)

Neutron inelastic scattering investigations have been performed on the spin tetrahedral system Cu_2Te_2O_5X_2 (X = Cl, Br). We report the observation of magnetic excitations with a dispersive component in both compounds, associated with the 3D incommensurate magnetic order that develops below $T^{Cl}_{N}$=18.2 K and $T^{Br}_{N}$=11.4 K. The excitation in Cu_2Te_2O_5Cl_2 softens as the temperature approaches $T^{Cl}_{N}$, leaving diffuse quasi-elastic scattering above the transition temperature. In the bromide, the excitations are present well above $T^{Br}_{N}$, which might be attributed to the presence of a degree of low dimensional correlations above $T^{Br}_{N}$ in this compound.

Bosonic stimulation of cold excitons in a harmonic potential trap in Cu [formula omitted

A high-density cold exciton gas is generated in a harmonic potential trap by two-photon resonance excitation of Cu 2 O at 2 K. Strongly localized light signal is observed at the bottom of the potential trap when the exciton density exceeds 10 17 cm - 3 . The possibility of bosonic stimulation of excitons from the trap rim to the bottom is discussed in connection with the origin of the light signal.

Photoredox reactivity of copper(II)-3,5-diisopropylsalicylate induced by ligand-to-metal charge transfer excitation of the copper-phenolate chromophore

The electronic spectrum of Cu II(dps) 2 in CH 3CN with dps=3,5-diisopropylsalicylate shows a ligand field absorption at λ max=711 nm ( ε=140 M −1 cm −1), and a phenolate to Cu(II) ligand-to-metal charge transfer (LMCT) band at λ max=428 nm ( ε=950). LMCT excitation of Cu II(dps) 2 leads to the reduction of Cu(II) to Cu(I). Copper(II) disappears with φ=2.8×10 −3 at λ irr=436 nm.

Optical tracking of high‐density cooled excitons in potential traps in Cu2O

AbstractThe density distribution of cold exciton clouds generated into a strain‐induced potential well by two‐photon excitation in Cu2O is studied at 2 K. The potential shapes of the double well are examined by two‐photon diagnostics. The motion of the exciton clouds is tracked by time‐resolved luminescence imaging and spectral imaging. We find that an anomalous spike appears on the center of the well in a specific excitation condition, i.e. ΔE = −5.0 meV, where ΔE is the detuning of the two‐photon excitation energy from the orthoexciton level under zero stress. The origin of the spike has been discussed in view of bosonic stimulation of the excitons into the ground state.

Coordination of Cu+ and Cu2+ ions in ZSM-5 in the vicinity of two framework Al atoms

A combined quantum mechanics/interatomic potential function technique has been used to examine Cu+/Al− sites in the vicinity of H+Al− sites and Cu2+ in the vicinity of two framework Al atoms under dehydrated conditions. The symmetrical coordination of Cu2+ ions to four framework oxygen atoms is the most stable site and Cu2+ is hard to reduce at these sites. In agreement with EPR measurements a square-pyramidal coordination of Cu2+ at these sites is suggested. However, this symmetrical coordination is attained only for specific positions of the framework aluminium pair. Coordination changes upon reduction of divalent to monovalent copper ions and upon excitation of Cu+ ions in the first triplet excited state are also investigated. The coordination of the copper ions does not significantly change during reduction in the dehydrated state. Coordination changes of Cu+ upon excitation in the triplet state and calculated transition energies for Cu+/Al− sites in the vicinity of H+Al− sites are identical to those observed for isolated Cu+/Al− sites.

Spin-Peierls Gap and Two-Magnetic-Excitation Bound and Resonant States in Cu1-xZnxGeO3and CuGe1-ySiyO3

We study a spin-Peierls gap and a bound and a resonant states of two magnetic excitations in Cu 1- x Zn x GeO 3 and CuGe 1- y Si y O 3 . Breakdown of the selection rule in the doped samples enables us to observe the spin-Peierls gap excitation in the first-order Raman process. It is found that this excitation shifts to lower frequency and merges into the tail of the elastic scattering together with its line broadening with increasing dopant concentration. The bound state of a particle-hole pair is observed just below the bottom of the second-order Raman band in pure CuGeO 3 . It changes into a resonant state and disappears rapidly as the concentration of the dopant is increased, owing to the weakening of attractive interaction and the extreme increase of the dampings of the magnetic excitations. These features are demonstrated theoretically by using Green's function.

Long-Lived Charge-Separated States Following Light Excitation of Cu(I) Donor−Acceptor Compounds

Long-Lived Charge-Separated States Following Light Excitation of Cu(I) Donor−Acceptor Compounds

Excitation-autoionization through 3d-4l inner-shell excitations in Cu- to Kr-like ions and the effect on fractional-ion-abundance balance in coronal plasmas.

Excitation of inner-shell electrons into autoionizing levels followed by autoionization (EA) can enhance the total ionization rate. For ions isoelectronic to elements of the fourth row, the present results show that the enhancements can be much more important than those previously calculated for the preceding isoelectronic sequences. \ensuremath{\Delta}n=1 3d-4l inner-shell excitations, which are the dominant EA channels, are considered here. Detailed computations of EA rates were performed using the relativistic distorted-wave method, and the behavior of the EA rate coefficients along the Cu, Zn, Ga, and Kr isoelectronic sequences has been analyzed. In the other sequences from Ge to Br with configurations involving a very large number of levels, EA calculations have been performed for a few elements only. In view of an easy use of the data, and for application to other elements, approximate analytical expressions have been deduced for ionization energies, average inner-shell excited-configuration energies, total electron-impact excitation rates, as well as average branching ratios for autoionization. These data enable a direct evaluation of the EA rates in all the sequences from Cu to Kr for all the elements with 40\ensuremath{\le}Z\ensuremath{\le}92. Finally, the EA rate coefficients were introduced in the coronal ionization rate equations. Fractional ion abundances for Mo (Z=42), Xe (Z=54), Pr (Z=59), and Dy (Z=66) obtained with and without taking into account EA processes are presented. The results show a decrease of up to 40% in the temperature of maximum abundance for Kr- to Ni-like ions.