Observed Charge Transfer Research Articles

Assessing pristine and metal doped C2N monolayer as a nanocarriers for anticancer drug

Theoretical research has introduced two-dimensional structures of thin sheets known as the pristine C2N monolayer and the Zn-doped C2N monolayer. These sheets show promise as nanocarriers for delivering the anticancer drug purinethol (PU). Through calculations of binding energy (Eb), it was observed that both the pristine C2N monolayer (−0.505 eV) and the Zn-decorated C2N monolayer (−0.762 eV) exhibit favorable characteristics for drug delivery. Eb values fall within range of physisorption, indicating their suitability as candidates for transporting drugs. An observed charge transfer (CT) of 0.035 e occurs in the Zn-decorated C2N monolayer, leading to a depletion of charge in the Zn-doped C2N monolayer system. The primary contributor to this charge loss is the Zn atom, which experiences a charge reduction of 0.035 e. To understand the phenomenon of drug release, the binding energy was recalculated under biological conditions, specifically in an acidic environment. The results indicate a decline in Eb (−0.218 eV) as well as a short recovery time, suggesting successful release of PU within body. The theoretical predictions we have made are expected to serve as inspiration for experimental researchers in their efforts to design drug delivery systems (DDSs) based on C2N monolayers.

Charge-transfer hyperbolic polaritons in α-MoO3/graphene heterostructures

Charge transfer is a fundamental interface process that can be harnessed for light detection, photovoltaics, and photosynthesis. Recently, charge transfer was exploited in nanophotonics to alter plasmon polaritons by involving additional non-polaritonic materials to activate the charge transfer. Yet, direct charge transfer between polaritonic materials has not been demonstrated. We report the direct charge transfer in pure polaritonic van der Waals (vdW) heterostructures of α-MoO3/graphene. We extracted the Fermi energy of 0.6 eV for graphene by infrared nano-imaging of charge transfer hyperbolic polaritons in the vdW heterostructure. This unusually high Fermi energy is attributed to the charge transfer between graphene and α-MoO3. Moreover, we have observed charge transfer hyperbolic polaritons in multiple energy–momentum dispersion branches with a wavelength elongation of up to 150%. With the support from the density functional theory calculation, we find that the charge transfer between graphene and α-MoO3, absent in mechanically assembled vdW heterostructures, is attributed to the relatively pristine heterointerface preserved in the epitaxially grown vdW heterostructure. The direct charge transfer and charge transfer hyperbolic polaritons demonstrated in our work hold great promise for developing nano-optical circuits, computational devices, communication systems, and light and energy manipulation devices.

Insights into charge transfer dynamics of Li batteries through temperature-dependent electrochemical impedance spectroscopy (EIS) utilizing symmetric cell configuration

Studying charge transfer processes in Li batteries poses a challenge due to their complicated nature and the battery's inherent inertness. While electrochemical impedance spectroscopy (EIS) offers a promising approach to investigating these processes, its effectiveness is hindered by the complexity of the data generated and the ambiguity in the analyses. Here, we demonstrate that the assignment process is not straightforward for complex secondary Li batteries, and it necessitates additional measurements and in-depth analysis. We first performed simplification of the impedance data by employing symmetric cell configurations to obtain charge transfer resistance values for each electrode. We second took advantage of altering three parameters during the EIS measurement: electrolyte composition, measurement temperature, and the state of health to extract important parameters related to both the anodic and cathodic charge transfer mechanisms. The analysis enabled the correlation of the observed charge transfer resistances to the corresponding electrochemical process and to obtain the kinetic parameters of the studied process. Our work illustrates how EIS can be used to study and understand the intricate electrochemical charge transfer processes in Li batteries, which are difficult to explore using alternative techniques.

Magnetic coupling mechanism of the interface in Bi2Se3/La0.7Sr0.3MnO3

The magnetic proximity effect in Bi2Se3 (BS)/La0.7Sr0.3MnO3 (LSMO) heterostructures is studied by first-principles calculations based on the density functional theory (DFT). Two heterogeneous structures LSMO (La, Sr, O termination layer, labeled as LaSrO)/BS and LSMO (Mn, O termination layer, labeled as MnO2)/BS are configured. In the LaSrO/BS system, the larger interfacial distance (2.88 Å) and higher interfacial binding energy (−6.36 eV) indicate a greater degree of stability for this structure. The spin polarization density distribution and spin magnetic moment results show BS can be effectively magnetized in both heterostructures. The magnetic coupling effect and observed charge transfer in MnO2/BS are more pronounced, suggesting potential differences in the magnetic exchange mechanisms between LaSrO/BS and MnO2/BS. The projected density of states (PDOS) and spin polarizability suggest that electron exchange and orbital hybridization between Mn-3d orbitals and BS play a crucial role in inducing magnetic order in BS. In MnO2/BS, the magnetic proximity effect is stronger, and more spin electron transfer between Mn-d and Se-p orbital of BS. These results may promote the application of TIs in the spintronic devices field.

Tuning the Electronic Properties of Two-Dimensional Lepidocrocite Titanium Dioxide-Based Heterojunctions.

Two-dimensional (2D) heterostructures reveal novel physicochemical phenomena at different length scales that are highly desirable for technological applications. We present a comprehensive density functional theory study of van der Waals (vdW) heterostructures constructed by stacking 2D TiO2 and 2D MoSSe monolayers to form the TiO2-MoSSe heterojunction. The heterostructure formation is found to be exothermic, indicating stability. We find that by varying the atomic species at the interfaces, the electronic structure can be considerably altered due to the differences in charge transfer arising from the inherent electronegativity of the atoms. We demonstrate that the heterostructures possess a type II or type III band alignment, depending on the atomic termination of MoSSe at the interface. The observed charge transfer occurs from MoSSe to TiO2. Our results suggest that the Janus interface enables the tuning of electronic properties, providing an understanding of the possible applications of the TiO2-MoSSe heterostructure.

Description of Photodegradation Mechanisms and Structural Characteristics in Carbon@Titania Yolk-Shell Nanostructures by XAS.

Carbon@titania yolk-shell nanostructures are successfully synthesized at different calcination conditions. These unique structure nanomaterials can be used as a photocatalyst to degrade the emerging water pollutant, acetaminophen (paracetamol). The photodegradation analysis studies have shown that the samples with residual carbon nanospheres have improved the photocatalytic efficiency. The local electronic and atomic structure of the nanostructures are analyzed by X-ray absorption spectroscopy (XAS) measurements. The spectra confirm that the hollow shell has an anatase phase structure, slight lattice distortion, and variation in Ti 3d orbital orientation. In situ XAS measurements reveal that the existence of amorphous carbon nanospheres inside the nano spherical shell inhibit the recombination of electron-hole pairs; more mobile holes are formed in the p-d hybridized bands near the Fermi surface and enables the acceleration of the carries that significantly enhance the photodegradation of paracetamol under UV-visible irradiation. The observed charge transfer process from TiO2 hybridized orbital to the carbon nanospheres reduces the recombination rate of electrons and holes, thus increasing the photocatalytic efficiency.

Electron-withdrawing bulky group substituted carbazoles for blue TADF emitters: Simultaneous improvement of blue color purity and RISC rate constants

Carbazole is a weak electron donor suitable to construct blue thermally activated delayed fluorescence (TADF) emitters, but the less repulsion effect of its five-member-ring structure can't guarantee the frontier molecular orbital separation and TADF feature. A group of carbazole-π-triazine based blue fluorescence emitters is designed by introducing the steric hindrance groups with different electronic properties at the donor or π-bridge. When electron-withdrawing pyridyl with moderate steric hindrance is introduced to the 1-site of 3,6-Di-tert-butyl-9H-carbazole, PyBuCz-TRZ and PyBuCz-MeTRZ gain the blue-shifted TADF. The observed charge transfer triplet excited state within the donor (3CTD) between carbazole and pyridyl units has different spatial orbital angular momentum and allowed spin-orbit coupling (SOC) with the charge transfer singlet excited state (1CT) of the whole molecule from carbazole donor to triazine acceptor, thus, acting as the media state to facilitate efficient multi-channel reverse intersystem crossing (RISC) process. This is the first time to introduce an electron-withdrawing group into the 1-position of carbazole donors to construct TADF molecules, not only achieving the blue-shifted TADF at 455 nm but also improving the external quantum efficiency to 15.3% in organic light-emitting diodes. This donor strategy should be valid to design more blue TADF materials.

Structural and bonding properties of small hydrocarbons inside Ca(squarate)-metal organic framework: ab-initio study

Ab−initio Molecular Dynamic (MD) and static Density Functional Theory (DFT) are used to study the structural and bonding properties of small hydrocarbon adsorbates inside Ca(squarate)−Metal Organic Framework (MOF). Car−Parrinello Molecular Dynamics (CPMD) simulations of a single−adsorbate−MOF structure are used to obtain the adsorbate most preferred site of adsorption. This site is used for further structural and bonding analyses using static DFT. Unlike many other MOFs; we found that the Ca(squarate)−MOF physisorbs and weakly binds small adsorbate molecules such as C2H2, C2H4, C2H6, and C3H8 with no observed charge transfer and minimal hybridization with the MOF orbitals. No covalent bonding is seen near the preferred site of adsorption. The calculated binding energies decreases as the H content in the adsorbate molecule increases and found to be −18.71 kJ/mol, −18.14 kJ/mol, −15.75 kJ/mol, and—4.47 kJ/mol for C2H2, C2H4, C2H6, and C3H8 molecules respectively. Density of State (DOS) and a Crystal Orbital Overlap Population (COOP) analyses show that the interactions between C and H atoms in the molecule and C and O atoms in the MOF have antibonding characteristics near the Fermi level. These antibonding states tend to destabilize the overall electronic structure of the combined adsorbate/MOF system and hence decrease the binding energies of these adsorbates inside the MOF.

Low loaded MoS2/Carbon cloth as a highly efficient electrocatalyst for hydrogen evolution reaction

Active edge sites of MoS2 nanosheets exhibit promising futures for hydrogen evolution reaction (HER), comparable with remarkable performances of highly cost platinum. However, 3D structures of MoS2 suffer from a lack of high mobility and unexposed active sites which lower the electrocatalytic activity. In this study, we show that there is a balance between increasing the active sites on the one hand and managing the charge transfer to facilitate the reaction on the other hand, and achieving this balance increases the efficiency of the electrocatalyst tremendously. For this purpose, we directly attached exfoliated MoS2 nanosheets onto carbon cloth (CC) substrate as a 3D network of conductive fibers via electrophoretic deposition at different applied voltages and deposition times, without adding any binder. This strategy gives rise to superior exposure of active sites while still maintaining good charge transferability over the whole 3D structure. Thus, a trace amount of loaded catalyst is enough to reach the benchmark current density of 10 mA/cm2 towards H2 production with a low overpotential of 137 mV vs. RHE. The Stability of the optimum structures under continuous operation was examined up to 50 min and further confirmed with 500 successive cyclic voltammetry (CV) sweeps. To understand the adsorption nature of hydrogen, density functional theory (DFT) was employed for the MoS2/graphene in both cases of pristine and defected MoS2. The results of hydrogen adsorption free energy calculations revealed that H adsorption on the S site is the most stable adsorption configuration and with increasing the MoS2 thickness, the MoS2/graphene activity towards hydrogen evolution decreases. A similar trend is also observed for the defected MoS2/graphene composite up to two-layer MoS2 and the activity remains the same for three-layer MoS2. The experimentally observed charge transfer into the MoS2 upon adsorption of the hydrogen atom and water molecule is also confirmed by our DFT calculations.

Charge transfer transitions in glasses - Attempt of a systematic review

In glasses, even low levels of dopants or impurities can give rise to very intense and broad charge transfer transitions from ligands (e.g. oxygen or fluorine ions) to the metal ion (L→M), absorbing strongly in the short wavelength ultraviolet. In an attempt of a systematic review of charge transfer transitions, we compile data of various glass systems with high intrinsic transmission that allow the observation of charge transfer (CT) transitions involving cations of different electronic configurations. Various glasses of different composition were selected as matrices, including fluoroaluminate glasses with low P2O5 content (FP10 = 35AlF3–10MgF2–30CaF2–15SrF2–10Sr(PO3)2), phosphate [SrP = Sr(PO3)2, NSP = Na2O-40SrO-50P2O5], silicate (NS = 15Na2O–85SiO2, DS = 33Na2O–67SiO2), aluminosilicate (BCAS = 10BaO–10CaO–15Al2O3–65SiO2) and borosilicate (NBS1 = 16Na2O–10B2O3–74SiO2, NBS2 = 4Na2O–1Al2O3–21B2O3–74SiO2, Duran = 5Na2O/K2O–1Al2O3–12B2O3–82SiO2) compositions. All glasses were prepared from very high purity materials and doped with various metal ions. Charge transfer transitions of electrons to or from these cations induce absorption and photoluminescence phenomena in the ultraviolet and visible spectral region, which were recorded by optical spectroscopy.Charge transfer transitions were considered for empty valence orbitals, that is, for the high valent 3d, 4d and 5d ions, and for Zn2+, Ag+, Cu+ with full d10 orbitals. 3d, 4d and 5d ions with partially filled valence orbitals that could be stabilized in the named glasses are studied as well. Doping concentrations for these allowed transitions typically ranged from 5 to 5000 wt-ppm of metal ions, with some samples also displaying higher dopant levels.Inter valence charge transfer (IVCT) transitions directly from one metal ion to a neighboring metal ion (M→M) of the same element or metal to metal charge transfer (MM-CT) between ions of different elements can also induce strong visible absorption and deep coloring for which some examples will be discussed.

Contact Charge Transfer between Nominally Identical Materials

AbstractDifferences in concentrations of excited electrons arising from geometry‐dependent differences in de‐excitation paths lead to differences in Fermi energies, which enable contact charge transfer between otherwise identical solids of different size. This model is used with a quasi‐equilibrium description of the Fermi energy to estimate a lower bound of the magnitude of charging of pairs of like particles and the charge distribution in groups of interacting like particles. The predictions agree with observed charge transfer directions between large and small particles and with the broad particle size range over which charging is observed. Estimates of charging are compared to available measurements, the breakdown limits of air, and the relative strengths of interparticle electrostatic and gravitational forces. The influence of particle size distribution on the charge distribution in groups of particles is examined.

Carrier Dynamics and Transfer across the CdS/MoS2 Interface upon Optical Excitation.

Carrier dynamics across the interface of heterostructures have important technological, photovoltaic, and catalytic implications. Using first-principles time-dependent density functional theory, we have systematically investigated the charge transfer of excited carriers from CdS to MoS2 and found that two interdependent mechanisms are responsible for the transfer, one slow and one fast. While the slower process may be attributed to typical electron-phonon coupling, the interfacial dipole resulting from this transfer enables a fast secondary process involving a level crossing of the excited carrier state in CdS with receiving states in MoS2. An analysis based on the interfacial binding energy reveals that the Cd-terminated (001) interface is by far the most energetically favorable, which in addition to its calculated fast resonant electron transfer suggests it is a good candidate to explain the experimentally observed charge transfer between CdS and MoS2.

In situ observation of charge transfer and crystal field formation via high energy resolution X-ray spectroscopy during temperature programmed oxidation.

Herein, it has been demonstrated how resonant X-ray emission spectroscopy can be employed to study the charge transfer dynamics in real-time during the temperature-induced oxidation of metallic tungsten. Application of high energy resolution schemes allowed distinguishing charge transfer to separate orbitals resulting from crystal field splitting. Based on the time-resolved studies, it was possible to determine the corresponding charge transfer rates. From the experimental data, we determined that the electron transfer during the thermal oxidation of the metal dominates in the temperature range of 470-570 °C, reaching a maximum of 0.036 electrons per °C.

Observation of charge transfer in mixed-dimensional heterostructures formed by transition metal dichalcogenide monolayers and PbS quantum dots

We report an experimental study on charge transfer properties of mixed-dimensional heterostructures formed by zero-dimensional PbS quantum dots and two-dimensional transition metal dichalcogenides. Monolayers of ${\mathrm{MoSe}}_{2}$ and ${\mathrm{MoS}}_{2}$ were fabricated by mechanical exfoliation and chemical vapor deposition techniques, respectively. PbS quantum dots with diameters of 2.3 and 5 nm were synthesized by a hot-injection method and characterized by optical absorption spectroscopy and ultraviolet photoemission spectroscopy. The quantum dots were deposited on the ${\mathrm{MoS}}_{2}$ and ${\mathrm{MoSe}}_{2}$ monolayers to form heterostructures. Photoluminescence and transient absorption measurements were performed on the heterostructures as well as individual materials to reveal their photocarrier dynamics. We found that the holes excited in ${\mathrm{MoSe}}_{2}$ can efficiently transfer to both 2.3- and 5-nm PbS quantum dots, while electrons in these quantum dots cannot transfer to ${\mathrm{MoSe}}_{2}$. Similar charge transfer properties were observed between ${\mathrm{MoS}}_{2}$ and the 5-nm PbS quantum dots, while no charge transfer was observed between ${\mathrm{MoS}}_{2}$ and the 2.3-nm quantum dots. These results provide useful information for understanding the physical mechanism of charge transfer in mixed-dimensional heterostructures and for developing PbS quantum-dot-based mixed-dimensional materials.

Anodic Behavior of Erythrocytes and Erythrocytes Ghosts on the Carbon Paste Electrode

Electrochemical investigations of processes occurring when blood cells come into contact with foreign conductive materials provide important fundamental and application-specific information. Indeed, the mechanism of blood cell interaction with foreign surfaces is not well understood at the present time. On the other hand, the results of such studies have the potential of underpinning the development of new physicochemical methods for assessment of the traumatic ability of the material towards blood cells. While charge transfer between metal bodies and erythrocytes has long been hypothesized, only recently was experimental (coulometric) evidence of electron transfer obtained during the interaction of erythrocytes with the platinum electrode [1]; it should be noted that this phenomenon was observed both in the cathodic and the anodic potential ranges. Electron transfer may be rationalized as a result of electrochemical transformations of functional groups located on the erythrocyte membrane. To elucidate the localization of electrochemical processes between the erythrocyte and the electrode, it is important to rule out the occurrence of numerous vital processes in a whole cell that could greatly complicate the interpretation of results. Therefore, erythrocytes ghosts, or lysed erythrocyte membranes that fully or partially retain the surface functional groups of whole red blood cells but no longer contain physiologically functional components of an erythrocyte, are an especially suitable model for studying such electrochemical processes on the membrane surface. In the present work, the electrochemical behavior of erythrocytes and erythrocytes ghosts on a carbon paste electrode (CPE) in phosphate buffered saline (PBS) was investigated. With a highly developed surface area compared to traditional solid electrodes, CPE possesses an increased sensitivity of measurements. Polarization measurements were performed using a three-electrode cell and an IPC Pro L potentiostat in the potential range between 0 mV and 1000 mV with a potential scan rate of 10 mV/s. A CPE working electrode (d = 2 mm) utilized was made from Super P carbon black (TIMCAL, Belgium) with paraffin oil as the binder. The mass ratio of carbon black to binder was 1:0.3 (w/w). Thermally expanded graphite foil was used as the auxiliary electrode, and saturated Ag/AgCl served as the reference electrode. In the resulting voltammograms recorded in a suspension of erythrocytes, two electrooxidation peaks are present, with maximums at potentials of +400 mV and +700 mV (Fig. 1a). The height of the oxidation peaks was dependent on the concentration of cells in the suspension. Thus, erythrocytes were shown to possess electrochemical activity on CPE in the anodic range of potentials. It is noteworthy that earlier work [1] did not discover any polarization peaks on the platinum electrode in the anodic potential range. However, the electrooxidation process was observed on the platinum electrode via coulometry at potentials more positive than +200 mV. This can be rationalized by considering the increase in sensitivity when using coulometry on a smooth platinum electrode as compared with the polarization measurement method. At the same time the voltammogram for the suspension of erythrocytes ghosts on a CPE is characterized by an electrooxidation peak with a maximum at +700 mV, with the peak maximum height being dependent upon the concentration of ghosts in the suspension (Fig. 1b). Evidence of electrochemical activity for both whole erythrocytes and erythrocytes ghosts corroborates the hypothesis that electrochemical processes (i.e., electron transport between the blood cell membrane and foreign material) are localized on certain functional groups present on the cell membrane. Differences in the anodic behavior of erythrocytes and erythrocytes ghosts may be attributed to erythrocytes ghosts not being a full-fledged cell, as well as to differences in the chemical composition of functional groups on cell membranes of erythrocytes vs. ghosts. The observed charge transfer phenomena provide experimental corroboration of the hypothesis about the involvement of cell-membrane functional group electrochemistry in the process of electron transport between erythrocytes (or erythrocytes ghosts) and a foreign surface. References Yu. Tsivadze, M.Sh. Khubutiya, I.V. Goroncharovskaya, A.K. Evseev, Michael M. Goldin, N.V. Borovkova, O.V. Batishchev and Mark M. Goldin, Mendeleev Commun., 27, 183 (2017). Figure 1

Air Gap-Based Cavities Dramatically Enhance the True Intrinsic Spectral Signals of Suspended and Pristine Two-Dimensional Materials

The properties of two-dimensional (2D) materials are readily affected by their surroundings. Therefore, the underlying substrates and surrounding materials always disturb the pristine properties of 2D materials. Herein, we describe how the pristine properties of suspended 2D materials can be precisely extracted from Raman and photoluminescence (PL) spectra with great signal enhancements by taking advantage of both air gap suspension and nanocavity enhancement effects. The modes of the Raman emission lines were enhanced to almost the same degree when the 2D materials were positioned over the nanocavity: the 2D/G peaks of suspended single-layer graphene (SLG) and the E12g/A1g peaks of MoS2 were significantly enhanced almost equally. Moreover, recording Raman and PL spectra at different positions of the suspended 2D materials was a very powerful tool for observing charge transfer between the pristine 2D materials and the surrounding materials. We also found that the residual holes of the suspended SLG could be neutralized by aluminum (Al) at certain positions. By employing the air cavity structure, we could readily locate the charge neutrality point of the suspended 2D materials. In addition, the PL intensity of MoS2 could be greatly enhanced when using the same nanocavity. The great enhancements in the PL signals from the suspended 2D materials allowed us to further investigate the spectral weights of both the A0 exciton and A– trion peaks when MoS2 was suspended or supported upon various metal films. This approach may open up new doors for techniques allowing precise characterization of abundant information from pristine and suspended 2D materials.

Observing Charge Transfer Interaction in CuI and MoS2 Heterojunction for Photoresponsive Device Application

Charge transfer interaction at the interface of semiconducting layered materials is of great interest to develop effective heterojunction optoelectronic devices. Here, we demonstrate the charge transfer interaction and formation of an active heterojunction between the molybdenum disulfide (MoS2) layer and p-type copper iodide (CuI) exhibiting excellent photoresponsive properties. The CuI film was fabricated by solid phase iodization of a copper film and direct thermal evaporation processes, which led to the formation of a transparent conducting layer. The thermally evaporated CuI film showed the main diffraction peak for the (111) plane, confirming the formation of the γ-CuI cubic crystal structure along the (111) plane on the MoS2 layers. The photoluminescence (PL) quenching effect was observed for the γ-CuI/MoS2 heterostructure, which can be attributed to the spontaneous separation of charge carriers at the interface. A photoresponsivity of 0.27 A/W was obtained at a bias voltage of 5 V for the γ-CuI/Mo...

Charge-transfer peculiarities in mesoporous BiVO4 surfaces with anchored indoline dyes

Mesoporous thin films of bismuth vanadate were synthesized by sol–gel method with defined deposition parameters and annealing treatments leading to nano-textured surfaces. The stabilization of monoclinic BiVO4 structure was demonstrated by structural investigations and nano-islands morphology of the films illustrated by Atomic Force Microscopy (AFM) studies. Indoline dyes (D149) were used to sensitize the film surfaces able to show photoinduced charge transfer on the hybrid surfaces using Kelvin force microscopy (KFM). The distributions of the surface electrical potentials were compared as function of the surface texture and the sensitization by dyes. A model of the band alignment in hybrid systems was proposed to account for the observed charge transfer. The photocatalytic activity of the hybrid films was also investigated and discussed.

Water Molecular Adsorption on the Low-Index Pt Surface: A Density Functional Study

We report the different way to explain the nature of water molecule (H2O) adsorption on the platinum (Pt) surfaces with low Miller index, i.e., (100), (110) and (111). Here, we perform periodic density functional theory (DFT) calculations to analyze the correlation between water-surface bonding strength and the observed charge transfer occurring in the systems. The results show that Pt-H2O interaction strength at the most stable adsorption sites, i.e., the atop site for each surfaces, follows the order of H2O/Pt(110) > H2O/Pt(100) > H2O/Pt(111). This order has the same pattern with the order of observed charge transfer contributed to the bonding formation. The differences in adsorption geometrical structures in these three surfaces are suggested to responsible for the order of bond strength since Coulomb interaction plays dominant roles in our electrostatic model. Furthermore, H2O-Pt interaction mechanism, which occurs through water 3a1 orbital releasing electron density (charge) followed by Pt-O bonding formation, is clarified.

Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution.

X-ray photoelectron and KLL Auger spectra were measured for the K^{+} and Cl^{-} ions in aqueous KCl solution. While the XPS spectra of these ions have similar structures, both exhibiting only weak satellites near the main line, the Auger spectra differ dramatically. Contrary to the chloride case, a very strong extra peak was found in the Auger spectrum of K^{+} at the low kinetic energy side of the ^{1}D state. Using the equivalent core model and abinitio calculations this spectral feature was assigned to electron transfer processes from solvent water molecules to the solvated cation. The observed charge transfer processes are suggested to play an important role in charge redistribution following single and multiple core-hole creation in atoms and molecules placed into environment.