Transition Metal Ion Doping Research Articles

The effect of Mn-doped ZnSe passivation layer on the performance of CdS/CdSe quantum dot-sensitized solar cells**Project supported by the National Natural Science Foundation of China (Grant Nos. 61376011, 61704114, 51402141, and 61604086), the Gansu Provincial Natural Science Foundation, China (Grant No. 17JR5RA198), the Fundamental Research Funds for the Central Universities, China (Grant Nos. lzujbky-2018-119 and lzujbky-2018-ct08), and the Fund from

ZnSe as a surface passivation layer in quantum dot-sensitized solar cells plays an important role in preventing charge recombination and thus improves the power conversion efficiency (PCE). However, as a wide bandgap semiconductor, ZnSe cannot efficiently absorb and convert long-wavelength light. Doping transition metal ions into ZnSe semiconductors is an effective way to adjust the band gap, such as manganese ions. In this paper, it is found by the method of density functional theory calculation that the valence band of ZnSe moves upward with manganese ions doping, which leads to acceleration of charge separation, wider light absorption range, and enhancing light harvesting. Finally, by using ZnSe doped with manganese ions as the passivation layer, the TiO2/CdS/CdSe co-sensitized solar cell has a PCE of 6.12%, and the PCE of the solar cell increases by 9% compared with the undoped one (5.62%).

Ultra-small cobalt nanocrystals embedded in 2D-MoS2 nano-sheets as efficient co-catalyst for solar-driven hydrogen production: Study of evolution rate dependence on cobalt nanocrystal size

2D-MoS2 nanostructures are attractive co-catalysts for photocatalytic hydrogen evolution due to their suitable water reduction potentials and high stability. However, the catalytic activity of MoS2 is greatly limited by the catalytically inert basal planes. Doping of transition-metal ions into MoS2 structure is an effective way to activating the basal planes. To this end, the formation of size-controlled metal nanocrystals with clean surface and mono dispersed nature is a current challenge. Here we utilized pulsed laser ablation in liquid approach to generate high purity size controlled cobalt nanocrystal by adjusting the laser fluences and systematically evaluate the effect of cobalt nanocrystals size and concentration on MoS2 to activate the basal planes. A set of Co-MoS2/CdS nanorods with different cobalt size were examined, and an optimal cobalt size of 3.1 nm was obtained. The optimized CdS/Co-MoS2 nanocomposite showed a very high H2 production rate (275 mmol h−1 g−1) with outstanding stability. To the best of our knowledge, this is the best performance reported for CdS/MoS2 based nanocomposites. The remarkable hydrogen evolution rate and stability may be due to reduced recombination rate and greatly increased density of catalytic active sites which is determined by photoluminescence and impedance spectroscopy. Finally, we believe that the strategies applied in the present study to form robust photocatalysts and its utilization in solar driven hydrogen production would inspire the development of other low-cost photocatalysts for renewable fuel production.

Emission Enhancement of Cu-Doped InP Quantum Dots through Double Shelling Scheme.

The doping of transition metal ions, such as Cu+ and Mn2+ into a quantum dot (QD) host is one of the useful strategies in tuning its photoluminescence (PL). This study reports on a two-step synthesis of Cu-doped InP QDs double-shelled with ZnSe inner shell/ZnS outer shell. As a consequence of the double shelling-associated effective surface passivation along with optimal doping concentrations, Cu-doped InP/ZnSe/ZnS (InP:Cu/ZnSe/ZnS) QDs yield single Cu dopant-related emissions with high PL quantum yields of 57–58%. This study further attempted to tune PL of Cu-doped QDs through the variation of InP core size, which was implemented by adopting different types of Zn halide used in core synthesis. As the first application of doped InP QDs as electroluminescent (EL) emitters, two representative InP:Cu/ZnSe/ZnS QDs with different Cu concentrations were then employed as active emitting layers of all-solution-processed, multilayered QD-light-emitting diodes (QLEDs) with the state-of-the-art hybrid combination of organic hole transport layer plus inorganic electron transport layers. The EL performances, such as luminance and efficiencies of the resulting QLEDs with different Cu doping concentrations, were compared and discussed.

Modifying La0.6Sr0.4MnO3 Perovskites with Cr Incorporation for Fast Isothermal CO2‐Splitting Kinetics in Solar‐Driven Thermochemical Cycles

AbstractPerovskites are promising oxygen carriers for solar‐driven thermochemical fuel production due to higher oxygen exchange capacity. Despite their higher fuel yield capacity, La0.6Sr0.4MnO3 perovskite materials present slow CO2‐splitting kinetics compared with state‐of‐the‐art CeO2. In order to improve the CO production rates, the incorporation of Cr in La0.6Sr0.4MnO3 is explored based on thermodynamic calculations that suggest an enhanced driving force toward CO2 splitting at high temperatures for La0.6Sr0.4CrxMn1−xO3 perovskites. Here, reported is a threefold faster CO fuel production for La0.6Sr0.4Cr0.85Mn0.15O3 compared to conventional La0.6Sr0.4MnO3, and twofold faster than CeO2 under isothermal redox cycling at 1400 °C, and high stability upon long‐term cycling without any evidence of microstructural degradation. The findings suggest that with the proper design in terms of transition metal ion doping, it is possible to adjust perovskite compositions and reactor conditions for improved solar‐to‐fuel thermochemical production under nonconventional solar‐driven thermochemical cycling schemes such as the here presented near isothermal operation.

Electrochemical Performance Enhancement of Na0.7MnO2 for Sodium-Ion Batteries By Doping and Conformal Surface Coating

Sodium-ion batteries (SIBs), which have similar working mechanism to that of Li-ion batteries (LIBs), have attracted great attention as new power sources for large-scale energy storage because of the abundant of Na reserves. However, there is still a huge challenge for the development of SIBs due to the low rate capacity and poor cycle stability of cathode materials. Different approaches of element doping and surface modifications have been widely applied to improve the electrochemical performance of those cathode materials. Herein, doping of Ti4+ and Zr4+ and coating of TiO2 and ZrO2 have been achieved by atomic layer deposition (ALD). The rate capability and cycling stability of the modified material were improved and the enhancement mechanism was studied. The TiO2 and ZrO2 coatings act as a stable interfacial layer to enhance the cycle stability of NMO by suppressing side reactions between the electrode and electrolyte. The doping of transition metal ions reduces the bond length of Mn-O and increases its bond energy, which further enhances the stability of the layered structure. In addition, the doping of transition metal ions can also enhance the intrinsic electronic conductivity by enlarging the Na-O bond length and lowering the Na+ migration barrier, thereby increasing the rate capacity.

Effects of co-activator species and transition metal ions doping on structure and fluorescence properties of strontium aluminate phosphors

The phosphors of SrAl2O4: Eu2+, RE3+ (RE = Dy3+, Tb3+, Ho3+, La3+, Nd3+, Y3+, Tm3+, Er3+) and SrAl2O4: Eu2+, Dy3+, M2+ (M = Mn2+, Ni2+, Mg2+, Cu2+, Zn2+) were synthesized by co-precipitation combined hydrothermal method, and analyzed by X-ray diffraction (XRD), fluorescence spectrometer and SEM. XRD patterns illustrated that the synthesized products all were the mixed crystal phase of SrAl2O4 and Sr4Al14O25. The diffraction peaks shapes of phosphors SrAl2O4: Eu2+, RE3+ (RE = Tb3+, Ho3+, Y3+) were almost unchanged contrast to the marked changes of phosphors SrAl2O4: Eu2+, RE3+ (RE = Tm3+, Er3+, Nd3+, La3+), which showed co-activator species had a great impact on the crystal field around the emission center (Eu2+). Besides, the peak positions of SrAl2O4: Eu2+, Dy3+, M2+ (M = Mn2+, Ni2+, Mg2+, Cu2+, Zn2+) were unaltered after doping, while the peak intensity of crystal phase Sr4Al14O25 was enhanced after doped by cations (Mn2+, Ni2+, Cu2+, Zn2+), which indicated the doping of transition metal ions would cause the crystal phase transition. The fluorescence analysis results indicated that the luminescent intensity were reduced after being doped by co-activator ions (Dy3+, Tb3+, Ho3+, La3+, Nd3+, Y3+), but enhanced when doped by co-activator ions (Tm3+, Er3+), and the final emission wavelength and intensity sequence were as follows: $$\lambda$$ Nd < $$\lambda$$ La < $$\lambda$$ Er < $$\lambda$$ Y < $$\lambda$$ Tm < $$\lambda$$ Tb < $$\lambda$$ Ho < $$\lambda$$ Dy, INd < IDy < IY < ITb < IHo < ILa < ITm < IEr. Instead, the fluorescence emission intensity decreased with the increment of the doping concentration of transition metal ions, which perhaps because the transition metal ions doping under the optimal concentration of co-activator could reduce the luminescence intensity of products due to the concentration quenching. The crystal particles of SrAl2O4: Eu2+, Dy3+ presented regular hexagon flake-like morphology with a width of ~ 500 nm and a thickness of ~ 70 nm. The title products could be applied in the safety indicators, emergency lighting danger signals, automobiles, solar cells, etc.

Tuning the optical bandgap of V2O5 nanoparticles by doping transition metal ions

Abstract In this study the influence of transition metal ions doping on optical properties of V2O5 nanoparticles is investigated. The shift in absorption edge caused by the dopant is analyzed from the UV-visible absorption spectra. The absorption edge of Ti doped V2O5 nanocrystals is shifted to longer wavelength region, while that of Zr doped V2O5 showed a blue shift. Ti doped V2O5 nanocrystal in spite of its large crystallite size showed improved optical properties and its optical bandgap (1.96 eV) is less than un-doped V2O5 (2.2 eV). This is attributed to lattice expansion by Ti ion and formation of oxygen vacancies within the bandgap. The oxygen vacancies acts as intermediate energy states and reduce the optical bandgap. However, the PL spectra of Ti-doped V2O5 did not exhibited emission peak corresponding to oxygen vacancies due to high crystallinity. The life time of excitons in excited state is investigated from time resolved PL decay. The excitons in doped sample showed tri-exponential decay whereas in pure sample they exhibited bi-exponential decay. The average lifetime of excitons in doped V2O5 is higher than pure V2O5 sample. This study reveals that by optimizing the concentration of Ti and Zr dopant ions in V2O5 lattice, its energy band structure can be tailored for photovoltaic, catalytic and photoluminescence applications. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Nanotechnology: Ideas, Innovations & Initiatives-2017 (ICN:3i-2017).

Transition-Metal Ion-Doped Flower-Like Titania Nanospheres as Nonlight-Driven Catalysts for Organic Dye Degradation with Enhanced Performances.

Titania has recently been identified as a new and effective nonlight-driven catalyst for degradation of organic pollutant with the use of H2O2 as an oxidant; however, either relatively low surface area or lack of diversity in chemical composition largely limits its catalytic performance. In this work, a series of transition-metal ion (Mn2+, Co2+, Ni2+, and Cu2+)-doped titania nanomaterials with regular flower-like morphology, good crystallinity (anatase), and large specific surface areas (71.4–124.4 m2 g–1) were facilely synthesized and utilized as catalysts for methylene blue (MB) degradation in the presence of H2O2 without light irradiation. It was revealed that the doping of transition-metal ions (especially Mn2+) into titania could significantly improve the catalytic efficiency. At 30 °C, 10 mL of MB with a concentration of 50 mg L–1 could be completely degraded within 60–100 min for these doped samples, whereas the removal rate was only 35.1% within 100 min with the use of pure flower-like titania. Temperature-dependent kinetic studies indicated that the presence of transition-metal ion dopants could markedly lower the activation energy and thus resulted in enhanced catalytic performances. Test of reusability exhibited that these doped catalysts could well keep their original catalytic activities after reuse for several cycles, indicating their excellent catalytic durability.

Enhanced activity of β-Ga2O3 by substitution with transition metal for CO2 photoreduction under visible light irradiation

Gallium oxide semiconductors have been developed as effective photocatalysts for water splitting driven by UV light irradiation, but there is no relevant study for the CO2 photoreduction application. Herein, we report the first investigation of β-Ga2O3 applying to photocatalytic CO2 reduction under visible light irradiation by doping transition metal ions (M = V, Cr, Mn, Fe, Co, Ni and Cu) onto the framework. Using sol-gel method, a series of transition metal ions incorporated β-Ga2O3 have been successfully obtained, in which the transition metal substitution content is 2 mol%. The β-Ga2O3:M photocatalysts are characterized completely by diverse tests (e.g., XRD, XPS, UV–Vis DRS, SEM). The effective replacement of Ga3+ ion by M ions significantly expands the scope of spectral response from UV light to visible light, and Fe3+, Co2+, Ni2+ significantly enhance the photocatalytic activity under visible light irradiation. In these cases, CO and H2 are evolved as the reduction products from CO2 and H+ by the generated electrons, respectively. Among these effective catalysts we prepared, β-Ga2O3:Ni exhibits the most substantial CO formation rate of 14.3 μmol/h at 30 °C, and the selectivity for CO evolution exceeds 60.9%. Furthermore, the CO formation rate increases to 24.6 μmol/h after loading of Ag as the co-catalyst. The stability of the Ag/β-Ga2O3:Ni are verified after five cycle of CO2 photoreduction under visible light.

Alteration of the electronic structure and the optical properties of graphitic carbon nitride by metal ion doping.

The photoluminescence quenching of graphitic carbon nitride (GCN) was systematically investigated with the doping of transition metal ions. The photoluminescence spectra of metal doped and pristine GCN were monitored and the trend of quenching efficiency was found to be Cu2+ > Co2+ > Mn2+. Interestingly, with the increasing doping concentration of different metal ions simultaneous red shift and luminescence quenching was determined in the photoluminescence spectra as well as increased absorption tail in longer wavelength hence enhancement in the bandgap. The change in the optical properties could be mainly due to structural reconstruction and doping induced electronic redistribution is discussed.

Photocatalytic properties of Fe-doped ZnO electrospun nanofibers

Undoped and Fe-doped Zinc Oxide (ZnO) nanofibers were prepared by electrospinning method to investigate the effect of transition metal ion doping on the photocatalytic performance of ZnO. A variety of techniques were employed to characterize various properties of the fabricated nanofibers. It was realized that the crystallization of ZnO fibers was significantly improved by optimizing the sintering conditions. The results revealed that Fe-doping greatly improved the photocatalytic activity of ZnO owing to modified nanofibers morphology and the reduced optical bandgap. The ZnO nanofibers showed the optimum photocatalytic activity for 1.5% Fe-doping percentage which was attributed to the presence of maximum dopant ions in the ZnO matrix. The enhanced photocatalytic performance of ZnO could increase its scope of industrial and commercial applications.

The Preparation and Optical Properties of Ni(II) and Mn(II) Doped in ZnTe Nanobelt/Nanorod by Using Chemical Vapor Deposition.

The doping techniques are often used to modify the properties of semiconductors. Transition metal ion doping in semiconductor can lead to dilute magnetic semiconductors (DMSs), which may initiate some novel properties related to spins. In contrast to the wide band semiconductor ZnO, ZnSe and CdS crystal the transition metal (TM) ion aggregate can be the origin of the ferromagnetic behaviors, which influence their optical properties mainly through the exciton-spin interactions due to their high exciton binding energy. For narrow band semiconductor, the carrier-spin coupling is the main cause of magnetism as observed in ZnTe. The ZnTe nanobelt for DMS with the TM ions such as Ni(II) and Mn(II) doping mainly induce the excess carrier effect in the lattice after photo-excitation, whose optical properties are also strongly depended on the fabrication method structure and morphology. Photo-excited carriers and electron-phonon interaction (but less excitons) are responsible for their large redshifts in ZnTe nanostructures. The strong interaction between the doped magnetic ion spins and holes, electron-phonon coupling, p-d hybridization as well as local electron correlation in TM ions determined their optical properties. TM ions incorporation in ZnTe lattice has suppressed the broad defect emission band far from the bandedge and broadened the electron correlations and electron hole plasma band near bandedge when excited by the rising excitation powers. We also identified that the polarized PL of Ni(II) and Mn(II) doped samples to calculate the strain dependence of band splitting near valance band.

Effect of Ni Doping on the Structural and Optical Properties of TiO2 Nanoparticles at Various Concentration and Temperature

TiO2 nanopowders doped by Ni were prepared by sol–gel method. The effects of Ni ion (transition metal ion) doping on the physical structural and optical properties of TiO2 have been investigated by X-ray diffraction (XRD), scanning electron microscopy and UV–Vis absorption spectroscopy. XRD results suggest that adding impurities has a significant effect on anatase phase stability, crystallinity, and particle size of TiO2. The phase transformation from anatase to rutile was inhibited by Ni ion doped TiO2 at temperatures 675 °C. The lowest band gap value (2.83 eV) was obtained for TiO2-4%Ni sample calcined at 675 °C.

Modified with Transition Metals (Cu, Fe, Ni, Co) as Efficient Deoxidizers for O2 Removal from Low-Concentration Coal Bed Methane

Deoxidizer Na2S/AC was modified with transition metal ions (Co2+, Ni2+, Fe3+, and Cu2+) by co-impregnation and step-by-step impregnation methods. Those deoxidizers were characterized and tested for the removal of O2 from low-concentration coal bed methane. Results showed that the effective deoxidizing amount of deoxidizers (QO2) and conversion rate of Na2S (CNa2S) of the deoxidizers are in the following order: Co-Na2S/AC > Ni-Na2S/AC > Fe-Na2S/AC > Na2S/AC > Cu-Na2S/AC. As compared to that of the deoxidizer Na2S/AC, the content of reactive oxygen species (O£–) of the modified deoxidizers was enhanced with the doping of transition metal ions (Co2+, Ni2+, Fe3+, and Cu2+). The more content of O£– on the deoxidizer was, the higher deoxidizing activity there was when the dispersion of Na2S and metal ions of deoxidizers was higher. The deoxidizer Co-Na2S/AC had the largest content of O£– and higher dispersion of Na2S and Co2+, and this made it the largest QO2 (54.88 mL/g) and CNa2S (75.50%) at 200 °C. However, ...

Effect of transition metal ion (Cr3+, Mn2+ and Cu2+) doping on the photocatalytic properties of ZnWO4 nanoparticles

In this work, we report the effect of transition metal ion doping on the photocatalytic properties of ZnWO4 nanoparticles. Undoped and transition metal (Cr3+, Mn2+ and Cu2+) doped ZnWO4 nanoparticles have been synthesized sonochemically and have been characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Band gap has been estimated using UV–vis diffuse reflectance spectroscopy (DRS) which shows a red shift with doping which could be attributed to doping effects and lattice variation. The photocatalytic efficiency of the samples was tested for Methylene blue (MB) degradation under simulated solar light (150 W Xe arc lamp) which showed improvement with doping. The best results were obtained for ZnWO4:Cr3+(2 mol%) and ZnWO4:Cu2+(2 mol%) samples which was a result of proper band gap tuning and enhanced separation of the photogenerated electron/hole pairs leading to effective degradation of the MB dye solution. The photocatalytic mechanism has been elucidated and it could be inferred that photogenerated holes and hydroxide radicals play a major role in the photocatalysis process.

A Rational Design for Enhanced Catalytic Activity and Durability: Strongly Coupled N-Doped CrOx/Ce0.2Zr0.8O2 Nanoparticle Composites

As a classic catalyst for NO oxidation, CrOx/Ce0.2Zr0.8O2 has been widely researched to improve its intrinsic catalytic activity and stability under complex flue gas environments. Some strategies, such as nanosize reduction, composite catalysts, and transition metal or rare earth ion doping, have been reported to enhance the catalytic properties. However, the commercialization of CrOx/Ce0.2Zr0.8O2 is greatly hindered by its poor stability under complex flue gas environments. Herein, we reveal a new route to fabricate N-doped CrOx/Ce0.2Zr0.8O2 nanoparticles, which exhibit not only higher NO conversion but also H2O and SO2 tolerance. The morphology and structure were analyzed via X-ray diffraction, transmission electron microscope, et al., investigating the enhancement of N doping. Additionally, the formation of the Ce–O–N–Zr chemical bond and the possible catalytic mechanism were examined by in situ diffuse reflectance infrared Fourier transform spectroscopy, which provided insight into both the fabricatio...

Synthesis of Mn-doped CuGaS_2 quantum dots and their application as single downconverters for high-color rendering solid-state lighting devices

Photoluminescence (PL) of quantum dots (QDs) can be modulated by doping transition metal ions into them, yielding either only a dopant-related single PL band with an excitonic emission entirely quenched or multiple PL bands with a dopant-related PL superposed, depending on the host QD composition targeted. Herein, we attempt Mn doping into green-emitting CuGaS2 (CGS) QDs through surface adsorption and lattice diffusion strategy. The resulting Mn-doped, ZnS-shelled CGS or CGS:Mn/ZnS QDs exhibit two distinct PL bands associated with host QD defect and dopant emissions. The spectral ratio of such two PL components is facilely tunable by varying Mn concentration. A series of CGS:Mn/ZnS QDs possess high PL quantum yields in the range of 74–76% regardless of Mn concentration. Taking full advantage of the wide PL coverage of green-to-red and efficient absorption capability at the blue region of the present doped QDs, they are packaged as single downconverters with a blue light-emitting diode (LED) chip to fabricate a high-color rendering solid-state lighting device. Various electroluminescent characteristics of white QD-LED are evaluated as a function of QD doping concentration and input current and discussed in detail.

Effects of Ho3+ and transition metal ion doping on optical and magnetic properties of BiFeO3 nanopowders

BiFeO3 (BFO), Bi0.9Ho0.1FeO3 (BHFO), and transition metal (TM = Cr, Mn, Co, Ni, Cu, Zn) doped Bi0.9Ho0.1FeO3 (BHFO-TM) nanopowders were prepared by a double-solvent-based sol–gel route. The effects of Ho3+ and TM ion co-doping on the structural, morphological, optical, and magnetic properties of BFO nanopowders were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–Vis-NIR Spectrophotometer, and vibrating sample magnetometer. XRD patterns confirmed the distorted perovskite structure with R3c space group for all BHFO and BHFO-TM samples. TEM images identified that the particles of all BHFO and BHFO-TM samples were structured at the nanoscale (50 ~ 90 nm). BHFO-TM samples represented different visible light absorption and further decreased the band gap of BFO. The band gap of BHFO-Co nanoparticles (NPs) was the least (1.70 eV), which was a promising material for photocatalyst and photovoltaic devices. The magnetic tests indicated that BHFO-Cr in the BFO, BHFO, and BHFO-TM NPs samples had stronger ferromagnetic property with a small coercive magnetic field (H c = 82 Oe), which is suitability for device applications. The mechanisms of the effects of Ho3+ and transition metal ion doping on optical and magnetic properties of BFO nanopowders were discussed in detail.

Microwave-Assisted Hydrothermal Synthesis of Co Doped ZnO Nanocrystals

Spintronic devices employing both semiconducting and ferromagnetic properties of materials are to be realized by doping of high spin transition metal ions to semiconductors such as ZnO. Transition metal oxides are also interesting as electrocatalysts for electrochemical conversion of renewable electricity to chemical energy for its storage. In this study, we have attempted microwave (MW)-assisted hydrothermal synthesis of Co, Mn-doped ZnO nanoparticles.Aqueous precursor solutions containing ZnCl2 and CoCl2 or MnCl2 at various ratios in a total concentration of 0.2 M were basified with NaOH to ca. pH 13, and subjected to a 2.45 GHz MW[1,2] to promote reaction at 160°C for 30 min. The products were characterized by FE-SEM, XRD and UV-Vis. Mesoporous electrodes of ZnO and Zn0.92Co0.08O were fabricated by doctor blading method. The green-colored Co-doped samples exhibit characteristic absorption peaks at around 560, 610 and 650 nm due to d-d transition of Co(II) and a red shift of the bandgap absorption onset. Phase separation of Co(OH)2 has also been suggested by XRD and FE-SEM images for x > 0.1, so that doping up to about 10% was apparently possible. Systematic shift of the three major XRD peaks of Wurtzite ZnO towards low angles was recognized upon increasing x, suggesting substitution of the lattice Zn2+ ions with Co2+. Lattice constants were calculated as a = b = 3.252 Å, c = 5.204 Å for ZnO, whereas they were enlarged to 3.277, 5.244 Å, respectively, for x = 0.20. CVs of ZnO and Zn0.92Co0.08O electrodes in a neutral electrolyte are compared in Fig. 1. Besides the clear decrease of cathodic charging and discharging currents, Co-doping results in an anodic wave at around + 1 V due to Co2+ → Co3+, followed by a large increase of irreversible anodic current, as compared to the non-doped sample. Chronoamperograms for a few minutes confirmed this current enhancement and gas bubble evolution from the anode due to catalytic oxidation of water (2H2O → O2 + 4H+ + 4e-). [1] Y. Hirai, K. Furukawa, H. Sun, Y. Matsushima, K. Shito, A. Masuhara, R. Ono, Y. Shimbori, H. Shiroishi, M. S. White & T. Yoshida, “Microwave-assisted hydrothermal synthesis of ZnO and Zn-terephthalate hybrid nanoparticles employing benzene dicarboxylic acids” Microsyst Technol (2017). doi: 10.1007/s00542-017-3392-y[2] H. Sun, L. Sun, T. Sugiura, M. S. White, P. Stadler, N. S. Sariciftci, A. Masuhara & T. Yoshida, “Microwave-assisted hydrothermal synthesis of struture-controlled ZnO nanocrystals and their properties in dye-sensitized solar cells” Electrochemistry, in press. Figure 1

EPR of transition metal ions in microplasma coatings on the surface of Ti − 0 , 3al and Ti − 6Al − 4V titanium alloys

The study focuses on the EPR examination of titanium oxidation states and doped transition metal ions in microplasma coatings on the surface of details made of Ti−0,3al and Ti−6Al−4V titanium alloys, depending on the duration and modes of the microplasma oxidation process. No Ti3+ states are observed in the anodic mode of microplasma oxidation. When the microplasma process is conducted in the anodic-cathodic mode, paramagnetic Fe3+ and Ti3+ states are observed in the Ti−0,3al alloy, and V4+ and Ti3+ states are found in the Ti−6Al−4V alloy. The removal of the technological layer mostly containing low-temperature titanium oxides eliminates the EPR spectra of the mentioned paramagnetic states of transition metal ions. The anodic mode of microplasma oxidation followed by the anodic-cathodic mode at the final stage does not yield paramagnetic states of transition metal ions, which is very important for many applications of microplasma oxidation of coatings because the Ti3+ state is chemically active and may affect many chemical processes occurring on the oxide layer surface. Meanwhile, the inverse sequence of the microplasma oxidation modes gives rise to paramagnetic states of transition metal ions in the technological layer.