Dr. Arpad ROSTAS

ZnO is recognized as one of the most versatile semiconductor materials, due to its adjustable properties, making it ideal for various applications. Herein, C-doped ZnO nanoparticles were obtained by thermal decomposition and tested as photocatalysts for water depollution and electrode materials in a symmetric supercapacitor device. These nanoparticles exhibited polyhedral shapes with sizes ranging from 95 to 104 nm. The impact of the doping level on the evolution of defect centers was analyzed using EPR and PL spectroscopy. Under visible light, the photocatalytic performance was tested against two contaminants, Rhodamine B (RhB) dye and oxytetracycline (OTC) antibiotic. A 1% C doping level provided the optimal photocatalytic performance, achieving degradation rates of 80% for RhB and 50% for OTC. The photodegradation process was elucidated by examining ROS species generated, linked to the measured valence band position and defect levels. Additionally, the same sample showed superior electrochemical performance when tested in a symmetric supercapacitor device, achieving a maximum specific capacitance of 104.16 F/g at a 2 mV/s scan rate, with an energy density of 14.46 Wh/kg and excellent cyclic stability, retaining 99% capacity after 2000 cycles. These findings highlight the versatility of C-doped ZnO nanoparticles, making them effective in environmental remediation and energy storage applications.

This study explores synthesizing and characterizing LaPO4:Sb3+/xMn2+ (LSBMx) phosphors (x = 0%-5%) prepared via the co-precipitation method. Structural analysis and luminescence properties reveal that LSBM0 (without Mn2+) emits blue light under UV excitation, while Mn2+-doped samples exhibit tunable emission from blue to orange-red. Under UV excitation, LSBMx phosphors demonstrate a broad visible emission band with multiple peaks attributed to the 4T1(4G) -> 6A1(6S) transition of Mn2+. The broad emission band (520-660 nm) can be deconvoluted into four Gaussian components centered at 564 nm (Mn-I), 595 nm and 616 nm (Mn-II), and 648 nm (Mn-III), corresponding to Mn2+ in La3+sites due to charge inconsistency, crystal field modifications induced by Sb3+ incorporation, and Mn2+- Mn2+ dimers, respectively. Energy transfer efficiency calculations determine the optimal Mn2+ concentration to be approximately 3%. This novel phosphor system demonstrates versatile green, orange, and red emission capabilities, establishing a valuable framework for developing Mn2+-doped luminescent materials with potential applications in LED lighting technology.

This study synthesized a solid-solution series of KCo1-x Ni x Cr2(PO4)3 phosphates with the alpha-CrPO4-type three-dimensional framework, in which edge-sharing CrO6 octahedra and PO4 tetrahedra create tunnels hosting K+ cations. Systematic Ni2+/Co2+ substitution was used to tune dielectric and charge-transport properties. All compounds showed stable paraelectric behavior; increasing Co content enhanced polarizability and dielectric permittivity while maintaining low dielectric loss. When used as electrode materials in graphite-based supercapacitors, higher Co content led to improved electrochemical performance, with the Co1Ni0 composition delivering a specific capacitance of 447 F/g, an energy density of 48.18 Wh/kg, and a power density of 1752 W/kg. The results demonstrate that Ni2+/Co2+ substitution is an effective strategy for designing advanced supercapacitor electrodes that combine high charge-storage capacity (due to increased permittivity) with improved power capability (due to higher conductivity).

Simonkolleite nano-platelets, with the chemical formula Zn-5(OH)(8)Cl-2 center dot H2O (ZHC), both undoped and Mndoped, were synthesized by a wet-chemical synthesis method. The physicochemical properties of the materials have been investigated using several complementary experimental techniques, including powder X-ray diffraction, specific surface area and porosity measurements, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray Fluorescence, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. On the one hand, the morpho-structural characteristics of the material are not significantly affected by the dopant used at low concentrations; however, the textural characteristics, specifically the specific surface area and porosity, vary with the Mn concentration. On the other hand, the cellular response of skin cells (human fibroblasts and mouse melanoma) exposed to undoped and Mn-doped ZHC was assessed, revealing a certain dependency on the Mn concentration. It was observed that the cells' response could be correlated with both the dopant concentration and the exposure time of the cells, independent of the morpho-textural characteristics of the materials. Even at the low Mn amounts used in this study, the cells' response depends on the Mn concentration, thus showing drastic cytotoxicity in human fibroblast cells at concentrations higher than 0.25 mu g/mL, irrespective of the exposure time (24 or 48 h), but showing low cytotoxicity at concentrations lower than 0.25 mu g/mL. In contrast, the presence of Mn does not drastically affect mouse melanoma cells, even at concentrations higher than 0.5 mu g/mL, but this depends on the exposure time. To our knowledge, this is the first study on the effects of Simonkolleite on skin cells, and it is of great interest considering the current and potential applications of this material in skin wound treatment and animal food supplements.

This study explores strategies to enhance the ionic conductivity of LiTi2(PO4)(3) (LTP), a promising NASICON-type solid electrolyte for next-generation solid-state batteries. Although LTP exhibits an open-framework structure favorable for Li+ diffusion, its intrinsic low ionic conductivity limits practical application. To address this, this research investigates the impact of co-doping titanium (Ti4+) with iron (Fe3+) and yttrium (Y3+) in Li1+xFeyYx-yTi2-x(PO4)(3) (where x = 0.3 and y = 0.1, 0.15, 0.2), aiming to increase charge carrier concentration and induce structural distortion beneficial for ion transport. Samples were synthesized via solid-state reaction and characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The local environment of Fe3+ was further analyzed using electron paramagnetic resonance and Mossbauer spectroscopy. Spark Plasma Sintering (SPS) was employed to obtain dense ceramics and suppress secondary phase formation. The electrical properties were investigated by impedance spectroscopy over the 150K-400K temperature range, and the relaxation dynamics and conduction mechanisms were analyzed using the modulus formalism and a.c. methods conductivity. The Li1.3Fe0.15Y0.15Ti1.7(PO4)(3) composition exhibited the highest room-temperature conductivity of 8.21 x 10(-4) S/cm, confirming the combined effect of Fe3+/Y3+ co-doping and SPS densification in enhancing the ionic transport properties of LTP-based solid electrolytes.

Ag-decorated TiO2 aerogels were synthesized using an acid-catalyzed sol-gel method, followed by drying under supercritical CO2 and annealing within the temperature range of 350-500 degrees C, with 50 degrees C increments. This study explores the preparation-structure-performance relationships of Ag-TiO2 aerogels influenced by the annealing process, focusing on their morphological, (micro)structural, optical, and textural properties and surface defects concerning photocatalytic activity. X-ray diffraction (XRD) and Raman spectroscopy confirmed that all aerogels exhibited a single anatase phase of TiO2, while electron microscopy (SEM/TEM) and XPS analysis demonstrated the presence of components. Increasing the annealing temperature resulted in particle size and pore structure changes, reducing the aerogel's overall surface area and porosity, as observed by SEM and nitrogen (N2) sorption analysis. Additionally, according to the Williamson-Hall (W-H) analysis based on the X-ray peak profile, the lattice microstrain value decreased while the crystallite size increased with rising annealing temperature. Optical investigation showed a strong UV light absorption characteristic of TiO2 and a visible light absorption band attributed to the plasmonic effect of silver nanoparticles. Moreover, a gradual photoluminescence (PL) quenching trend was observed with decreasing annealing temperature, indicating a reduction in the recombination rate of photo-induced electrons and holes in Ag-TiO2, alongside the formation of oxygen vacancies and structural defects, consistent with electron paramagnetic resonance (EPR) measurements. The Ag-decorated TiO2 aerogels demonstrated enhanced visible-light photocatalytic activity for methylene blue (MB) degradation, with the Ag-TiO2 aerogel annealed at 500 degrees C exhibiting the highest photocatalytic performance. This improvement can be attributed to the synergistic effects of chemical composition, plasmonic enhancement, morphological properties, and light absorption characteristics.

This study presents annealing time variation as an alternative approach for tuning structural and ionic defects in SnO2 nanoparticles (NPs) synthesized by a modified Pechini method, to modulate charge transfer and the formation of reactive oxygen species (ROS), enabling a correlation of these with photocatalytic activity. Structural refinements of the X-ray diffraction (XRD) data, combined with Raman and infrared (IR) spectroscopy, revealed that the samples adopted a tetragonal P42/mnm symmetry, with a distinct short-range structural order (associated with intraoctahedral [SnO6] distortions), which strongly depends on the annealing time. Field emission scanning electron microscopy (FE-SEM), scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (STEM/EDX), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) analyses showed the formation of homogeneous NPs smaller than 50 nm in the SnO2 samples, with a surface area between 12.072 and 14.102 m2 g-1. The presence of unusual reduced Sn3+ species associated with oxygen vacancies (VO) was evidenced by electron paramagnetic resonance (EPR) spectroscopy, and Sn2+ was characterized by Sn MNN Auger electron emission. The amount of these defects also depends on the annealing time. The synergistic effect and the photocatalytic mechanism were then elucidated. The degree of intraoctahedral [SnO6] distortions and the amounts of Sn3+:VO defects play a fundamental role in the charge transfer mechanism to modulate ROS generation during photoexcitation, as indicated by the photohydroxylation of terephthalic acid (TA) and in situ spin-trapping EPR measurements. Specifically, we show the formation of two main ROS, center dot OOH and center dot OH, which leads to a different photocatalytic pathway in SnO2 NPs. In conclusion, our study enlightens and uncovers the importance of choosing appropriate conditions for materials processing to fine-tune structural and electronic properties to design other functional materials.

Herein, alpha-MoO3 micro- and nanoparticles were synthesized by a modified Pechini method, and the impact of the crystal structure and crystal growth orientation on the formation of ionic defects and, consequently, on the catalytic performance of the materials in the ethylic transesterification reaction for biodiesel production was investigated. Structural refinements from X-ray diffraction data and Raman spectra revealed the formation of alpha-MoO3 in a Pbnm orthorhombic phase, with nanoplate-like morphology at 500 degrees C (thickness between 100 and 260 nm) or ribbon-like morphology at 700 degrees C (thickness between 400 and 900 nm). An anisotropic crystal orientation along the [010] direction was observed with an increase of the calcination temperature. We emphasize the dependence of the orientation change with the elimination of ionic-type defects (oxygen vacancies and reduced Mo5+ centers) by the temperature using complementary techniques such as X-ray photoelectron and electron paramagnetic resonance spectroscopies. The catalytic activity of the samples depends on the orientation process and the presence of defects that act as acid-active sites on the catalyst surface and therefore play an important role in biodiesel production. This effect was confirmed by surface stability and reactivity simulated by density functional theory calculations, suggesting that the Mo and O surface terminals greatly impacted the interface catalytic reaction. The highest catalytic performance toward the biodiesel conversion (89% of conversion at 150 degrees C for 2 h) was achieved for the polycrystalline catalyst calcined at 500 degrees C, which was correlated with random crystal orientation and the presence of reduced Mo5+ and oxygen vacancy centers on the different facets exposed on the surface. The biodiesel production was confirmed by H-1 and C-13 NMR spectroscopy and gas chromatography analysis.

Most photocatalytic processes involve physicochemical phenomena occurring at the semiconductor-water interface. The interfacial charge transfer strongly depends on the charge carrier self-trapping or defect-based trapping mechanisms active in the crystal lattice of the photocatalyst. Thus, the crystal lattice distortion is expected to influence the photocatalytic efficiency during polymorphic phase transformations (PPT). A simple synthesis method involving the ultrasound-assisted excess hydrolysis of titanium tetra-isopropoxide (TTIP) (hydrolysis ratio (number of moles of water/number of moles of TTIP) r = 245) was used to obtain multiphase titanium dioxide (TiO2) nanomaterials with complex defect structures. Electron paramagnetic resonance (EPR) spectroscopy was employed to characterize the paramagnetic centers in the synthesized TiO2 and their behavior during incipient PPT. The calcined samples showed a complex defect structure comprising three types of paramagnetic centers: F+-centers (an electron trapped in an oxygen vacancy (Ov)), V-centers (oxygen ions with trapped holes) and paramagnetic centers involving Ti3+ such as Ti3+- Ov. The sample obtained at 600 degrees C, temperature marking the onset of a massive mixed transformation of anatase into rutile and brookite, composed of approximately 81 % anatase, 10 % brookite, and 9 % rutile, exhibited an intense and broadened EPR signal and enhanced photocatalytic activity for hydroxyl radical generation and hydrogen production by water splitting, despite its rather low specific surface area of 34 m2/g. The results revealed the synergistic effects of charge carrier trapping mechanisms in the early stages of PPT, boosting the photocatalytic performance of TiO2. The present study supports the design of facile synthesis methods for better TiO2 photocatalysts and promotes the development of further studies regarding lattice defect engineering during phase transformations in nanomaterials.

Herein, Cu(II)-doped SrSnO3 perovskites (SrSn1-x Cu x O3, namely SSO:Cux) were prepared by a modified Pechini method and applied as supercapacitors (SCs) for the first time. The effect of dopant concentration (x = 1, 2.5, and 5 mol %) was investigated to fine-tune the structural and electronic properties to design potential candidates as SCs. The SSO:Cux samples were characterized by conventional XRD and synchrotron XRD (S-XRD) combined with Rietveld refinements and spectroscopic analyses, such as Raman, FTIR, UV-vis, EPR, and XANES/NEXAFS. The electrochemical performance of the SSO:Cux samples was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic cycling with potential limitation (GCPL). It was evidenced that incorporating 2.5 mol % Cu(II) into the SrSnO3 perovskite lattice (SrSn0.975Cu0.025O3, SSO:Cu2.5) led to a significant change in structural disorder and electronic properties, which play an essential role in creating a mixture of point defects such as reduced Sn3+ and Cu+ cations, and oxygen vacancies (VO). The SC device constructed with the SSO:Cu2.5 material showed a specific capacitance of 613 F g-1 at a scan rate of 1 mV s-1, with a remarkable specific energy density and specific energy power of 25.42 W h kg-1 and 32678.57 W kg-1, respectively, which are higher than those observed for any other available perovskite-based SCs. This performance was primarily attributed to the formation of mixed Sn4+/Sn3+ and Cu2+/Cu+ cations, which alter the structural and electronic properties of SrSnO3. Our findings indicate that an improved capability to store high energy and power may be achieved by fine-tuning the Cu(II) dopant concentration in the lattice and controlling the formation of undesired phases. This offers experimental guidance to design other Cu-doped perovskites as alternative materials for energy storage applications.

The effect of the annealing temperature on 1% nitrogen-doped WO3 materials was studied, which were then used as electrode materials for high-performance supercapacitor (SC) devices. The supercapacitive performance of the proposed materials was strongly influenced by the doping element and the annealing temperature by directly changing the defect structure of the host material. The 1% N-doped WO3 materials annealed at different temperatures were thoroughly characterized through various characterization techniques, including electron paramagnetic resonance and photoluminescence spectroscopy, giving insight into the effect of N-doping on the defect structure and optical properties of WO3. When the WO3:N materials were used as electrode material in symmetric SCs, the doping element and the annealing temperature improved the electrochemical performance. No booster materials (such as carbon black) were used in the symmetric SC designs, showing increased specific capacitance (102 F/g) and energy density (14.6 W h/kg) values.

Visible light-mediated photodegradation offers a sustainable and environmentally friendly solution for removing emerging contaminants from water sources. Herein, we report on the synergy effect between adsorption and visible-light-driven photo-degradation of 17 fl - estradiol using (Au)TiO 2 nanotubes-graphene composites. The graphene structures (graphene oxide - GO or thermally reduced graphene oxide - trGO) provide a platform for strong adsorption of 17 fl -estradiol molecules and facilitate the charge transfer between plasmonic Au nanoparticles and TiO 2 , leading to an improvement of the overall degradation process. To better understand the effect of Au nanoparticles and TiO 2 separately, three different concentrations of Au (1 %, 2.5 %, and 5 %) were prepared and characterized. The estrogenic molecules preferred GO over trGO, suggesting that hydrogen bonds govern the interaction between GO and 17 fl -estradiol. Consequently, a higher photocatalytic efficiency of GOcontaining composites was observed when removing estrogenic molecules. The role of adsorption proved crucial for capturing and retaining more contaminant molecules on the composite surface, thus increasing the odds of surface reactions with the photogenerated carriers. A total removal of 17 fl -estradiol has been obtained for Au (1 %, 2.5 %, and 5 %) TiO 2 nanotubes-GO. The mechanism behind the adsorption and photo-degradation processes has been discussed.

Potassium ions are important for developing electrode materials because they have similar properties to lithium and sodium ions. Mixed chromium phosphates (KMIICr(PO4)2) II Cr (PO 4 ) 2 ) with substituted M II sites using divalent elements (M = Ni, Co, Cu) were synthesized using a solid-state reaction method. The samples were analyzed using various techniques such as powder X-ray diffraction, Fourier transform infrared, Raman, and electron paramagnetic resonance spectroscopy. The proposed phosphates had a monoclinic phase structure with a P21/n 1 /n space group, and they contained large tunnels occupied by K+ + cations. The dielectric properties showed that the Ni-based phosphates had slower dielectric relaxation, while the Co and Cu-based phosphates had quicker polarization and depolarization processes. Additionally, the resistance of the grains decreased from Ni to Co to Cu-based phosphates, indicating easier charge movement in each material, consistent with the increase in conductive losses and a.c. conductivity when changing the M II ions.

The compounds KBa 1-x Sr x Cr 2 (PO 4 ) 3 (with x = 0.00; 0.25; 0.50; 0.75; 1.00) were synthesized by a solid-state reaction, and they were thoroughly characterized by different spectroscopic and microscopic techniques. Their structures were indexed in a cubic system with a P2 1 3 space group forming a 3D framework built on CrO 6 octahedra and PO 4 tetrahedra sharing vertices leading to identical Cr 2 P 3 O 18 (U) units. The interconnection between the tetrahedral and octahedral groups leads to the formation of two large closed cavities (K, M II )(1) and (K, M II )(2), statistically occupied by K + and M 2+ (M = Ba, Sr) atoms. Electron paramagnetic resonance spectroscopy confirmed the presence of paramagnetic Cr 3+ ions, showing the effects of substituting the Ba 2+ ions with smaller Sr 2+ ions on the dipolar coupling between the Cr 3+ centers. The obtained materials and active carbon were used as electrode materials in hybrid SC devices. At the same time, their electrochemical properties were assessed by potentiostatic electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge measurements, showing promising results with a maximal specific capacitance (3.86 F/g), energy density (343 mWh/kg), and power density (30.9 kW/kg) in the case of KBa 0.5 Sr 0.5 Cr 2 (PO 4 ) 3 , proving them as good candidates for positive and/or negative electrode materials for energy storage applications.

Plastics are omnipresent in the environment and degrade into smaller fragments in time. This study shows how plastics could reach nanometer sizes under specific conditions and the interaction of the nanofragments with prokaryotic cells. Imaging and spectroscopy techniques were employed to determine the modifications induced in artificially aged low-density polyethylene (LDPE). Scanning electron microscopy indicated that nanometer-scale LDPE could be obtained after ultraviolet-C (UVC) exposure for 10 days. Raman and Fourier-transformed infrared spectroscopy confirmed the chemical changes within the UVC-exposed LDPE are consistent with the increase of crystallinity. Moreover, the interaction between the degraded LDPE and chemo- and photosynthetic organisms was observed through fluorescence, confocal, electron microscopy techniques, and electron paramagnetic resonance spectroscopy. The results showed how micro/nano-LDPE could influence the development of Escherichia coli and Arthrospira platensis after only 72 h of interaction. This fundamental study indicates the environmental presence and effects of nanometer-sized LDPE resulting from light exposure.

Bulk nanocrystalline La0.67Ba0.33_xKxMnO3 (with x = 0, 0.05, 0.1, and 0.2) manganites have been prepared by the modified sol-gel method (Pechini). The single-phase rhombohedral crystal structure with the R-3c (no. 167) space group was verified by X-ray diffraction (XRD) and sustained by Rietveld refinement. As follows from the results of XRD structural analyses, the increase in K-doping triggers an increase in the distortion of the MnO6 octahedra, which eventually causes the narrowing of the eg bandwidth. Mn is in a mixed valence state of Mn4+/ Mn3+ as inferred by X-ray photoelectron spectroscopy. Magnetic measurements confirm that the Curie tem-perature decreases from 348 K for La0.67Ba0.33MnO3 to 316 K for La0.67Ba0.13K0.20MnO3. The increasing of the Mn4+ ion concentration at the B-site sublattice and A-site ionic disorder (sigma 2) breaks up the double exchange interaction between the Mn3+ and Mn4+ ions. The ferromagnetic to paramagnetic second-order magnetic phase transition at TC is also confirmed by electron paramagnetic resonance. According to magnetic field-dependent magnetization isotherms at different temperatures, La0.67Ba0.13K0.20MnO3 shows a relatively large magneto -caloric effect (1400 mJ cm_ 3 K_ 1 at 316 K under 5 T applied magnetic field), which raises the possibility of using this material for room-temperature micro-scale magnetic cooling.

We investigate the interlayer coupling between two thin ferromagnetic (F) films mediated by an antiferromagnetic (AF) spacer in F*/AF/F trilayers and show how it transitions between different regimes on changing the AF thickness. Employing layer-selective Kerr magnetometry and ferromagnetic-resonance techniques in a complementary manner enables us to distinguish between three functionally distinct regimes of such ferromagnetic interlayer coupling. The F layers are found to be individually and independently exchange-biased for thick FeMn spacers-the first regime of no interlayer F-F* coupling. F-F* coupling appears on decreasing the FeMn thickness below 9 nm. In this second regime found in structures with 6.0-9.0-nm-thick FeMn spacers, the interlayer coupling exists only in a finite temperature interval just below the effective Neel temperature of the spacer, which is due to magnon-mediated exchange through the thermally softened antiferromagnetic spacer, vanishing at lower temperatures. The third regime, with FeMn thinner than 4 nm, is characterized by a much stronger interlayer coupling in the entire temperature interval, which is attributed to a magnetic-proximity induced ferromagnetic exchange. These experimental results, spanning the key geometrical parameters and thermal regimes of the F*/AF/F nanostructure, complemented by a comprehensive theoretical analysis, should broaden the understanding of the interlayer exchange in magnetic multilayers and potentially be useful for applications in spin thermionics.

Photocatalysis is one of the approaches for solving environmental issues derived from extremely harmful pollution caused by industrial dyes, medicine, and heavy metals. Titanium dioxide is among the most promising photocatalytic semiconductors; thus, in this work, TiO2 powders were prepared by a hydrothermal synthesis using titanium tetrachloride TiCl4 as a Ti source. The effect of the hydrochloric acid (HCl) concentration on TiO2 formation was analyzed, in which a thorough morpho-structural analysis was performed employing different analysis methods like XRD, Raman spectroscopy, SEM/TEM, and N-2 physisorption. EPR spectroscopy was employed to characterize the paramagnetic defect centers and the photogeneration of reactive oxygen species. Photocatalytic properties were tested by photocatalytic degradation of the rhodamine B (RhB) dye under UV light irradiation and using a solar simulator. The pH value directly influenced the formation of the TiO2 phases; for less acidic conditions, the anatase phase of TiO2 crystallized, with a crystallite size of approximate to 9 nm. Promising results were observed for TiO2, which contained 76% rutile, showing a 96% degradation of RhB under the solar simulator and 91% under UV light after 90 min irradiation, and the best result showed that the sample with 67% of the anatase phase after 60 min irradiation under the solar simulator had a 99% degradation efficiency.

Because of their significant magnetocaloric properties, Ca and Pb-doped LaMnO3 can be employed in magnetic refrigeration systems. The partial substitution effect of Ca2+ by Pb2+ cations on the structural, magnetocaloric properties, and critical behavior of mixed valence perovskites La0.8Ca0.2-xPbxMnO3 (0 <= x <= 0.15), synthesized by the flash combustion route, was studied in this work. The presence of structural transformations of the prepared ceramics from an orthorhombic structure (Pbnm space group) for samples with x = 0.1 was detected by X-ray diffraction analysis, which is related to the A-site disorder. The field-cooled (FC) magnetization indicated a second-order ferromagnetic-paramagnetic transition for the investigated samples when the temperature was increased. Due to the change in the Mn3+/Mn4+ ratio, substituting Ca2+ with larger Pb2+ ions increases the Curie temperature (T-C) by increasing Pb doping content from 90 K for x = 0 to 205 K for x = 0.15. The magnetization isotherms of all samples showing a second-order phase transition were studied, where an applied magnetic field of 5 T, the value of maximum magnetic entropy variation /Delta S-M(max)/ for the sample with x = 0.15 was estimated to be 2.73 Jkg(-1) K-1. In addition, it has a significant relative cooling power of about 276 Jkg(-1) under the same applied magnetic field strength. The critical behavior of the samples was investigated close to T-C. The exponent values were identical to the mean-field method, indicating a large disorder of spin magnetic moments in the perovskite compounds.

In this work, Tungsten(W)-doped TiO2 nanoparticles were synthesized using the sol-gel method and were used as electrode materials in supercapacitor applications. The structural and morphological properties of the prepared samples were analyzed by means of XRD, STEM, TEM, and XPS. The analysis of the defect centers was carried out using EPR spectroscopy. The electrochemical analysis of the assembled supercapacitor was done using cyclic voltammetry, galvanostatic cycling with potential limitation technique, potentiostatic electrochemical impedance spectroscopy, and voltage-holding experiments. All the presented samples showed paramagnetic defects in the EPR analysis, while 0.5% W-doped TiO2 showed a maximum signal intensity. The supercapacitor performance from the synthesized electrode material showed highly encouraging results. The equivalent series resistance (R-s) value for all the designs showed values under "1 omega,' which reflects high conductivity. As the maximum EPR intensity comes from TiO2 doped with 0.5% W, the supercapacitor performance of this sample was tested with a newly designed five-electrode system. This design showed superior performance compared to any other used designs with a specific capacitance of 25.5 F g(-1), with an energy density of 14.16 Wh kg (-1 )at 302 kW kg (-1).

The phosphate KCoCr-(PO4)(2) and iron-substitutedvariants KCoCr1-x Fe x (PO4)(2) (x =0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route,while a high substitution level of Fe was achieved. Their structureswere refined using powder X-ray diffraction and indexed in a monoclinicsystem with a P2(1)/n spacegroup. A 3D framework with six-sided tunnels parallel to the [101]direction was formed in which the K atoms are located. Mo''ssbauerspectroscopy confirms the exclusive presence of octahedral paramagneticFe(3+) ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopyconfirmed the presence of paramagnetic Cr3+ ions. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present higher ionic activity. Relative to the electrochemicalactivity of K, these materials could be good candidates for positiveand/or negative electrode materials for energy storage applications. The synthesized phosphate KCoCr-(PO4)(2) and Fe-substituted variants KCoCr1-x Fe x (PO4)(2) (x = 0.25, 0.5, and 0.75) present a 3D frameworkwith six-sided tunnels in which the K atoms are located. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present improved ionic activity, making these materials goodcandidates for positive and/or negative electrode materials for energystorage applications.

Sodium hexatitanate (Na2Ti6O13) nanoparticles have been synthesized by the hydrothermal method with microwave and conven-tional heating, after which their photocatalytic properties toward an azo dye pollutant degradation have been investigated. Insights into the dynamics and reactivity of the species involved in the photocatalytic mechanism of the (Na2Ti6O13) samples were precisely investigated, for the first time, by X-band electron paramagnetic resonance (EPR) spectroscopy under different experimental conditions. X-ray diffraction structural analysis revealed that all samples crystallized in a monoclinic C2/m structure, with different short-range structural order according to the employed heating, as indicated by Raman. Field-emission scanning electron microscopy and transmission electron microscopy results revealed the formation of rod-and fiber-like nanoparticles with different diameters and lengths. EPR measurements indicated the presence of different Ti3+ point defects and F centers in the samples. X-ray photoelectron spectroscopy analysis proved the presence of oxygen-related defects, but no Ti3+ was detected on the surface. Spin trapping experiments monitored the generation of hydroxyl (OH center dot) radicals over UV-irradiation time. Various parameters contribute to the photocatalytic activity of the samples; however, the type of defect and particle morphology appeared as key factors for enhanced efficiency. Our study provides significant information about paramagnetic defects in Na2Ti6O13 materials and their role in photocatalysis to design other Ti-based photocatalysts.

Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H-2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), approximate to 5 x 7 & Aring;(2) in cross-section, that generate H-2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H-2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H-2 photochemically for a long time.

Complex physico-chemical investigations have been performed on white inlaid substance used in the orna-mentation of prehistoric clay artefacts from southern Romania ceramics from the Early Chalcolithic, up to the Middle/Late Bronze Age. Structural and morphological investigations of the white pigments have showed hundreds of nm up to microns size particles with calcite and hydroxyapatite (ash bone) as dominant components. The calcite was found on Early Chalcolithic pigment vessels while those where hydroxyapatite was dominant from the Middle/Late Bronze Age. FTIR spectra revealed the biogenic source of the hydroxyapatite (i.e. cremated animal bone) and the crystallinity degree values agrees with the expected temperatures of firing of the ancient furnaces; the calcite-based pigments were supposed to be filled post firing. The EPR was not able to able to provide a clear assignment of the cremated animal bones but thermoluminescence showed various sources of calcite.

Zeolitic imidazole frameworks (ZIFs) and TiO2 based composites have recently attracted interest to control pathogenic microorganism growth. In this context, two novel TiO2/ZIF-67 nanocomposites were synthesized by the microwave-assisted solvothermal method using two different routes: one pot composite (OPC) and two step composite (TSC) syntheses. X-ray powder diffraction and vibrational spectroscopy data revealed the formation of crystalline ZIF-67 and disordered TiO2 in the OPC composite, while both phases were crystalline in the TSC sample. Sphere-like morphologies were obtained for both materials, as indicated by SEM and TEM images. XPS measurements showed mixed-valence Ti (Ti3+/Ti4+) and Co (Co2+/Co3+) on the surface of both materials, while EPR analysis confirmed the presence of Co2+ ions and oxygen-related defects. The results showed that TiO2 has no antimicrobial activity against Staphylococcus aureus, while the TSC has higher and the OPC has lower activity than pure ZIF-67. Highly efficient biocidal activity at a concentration of 2.5 mg mL(-1) was observed for the TSC. The difference in the antimicrobial performance of the nanocomposites can be correlated with the balance between structural order/disorder, which depends on the synthesis route used, and the material solubility. The results also indicate the release of Co ions and the ligand as a possible mechanism together with redox reactions to inactivate bacteria. Thus, this work provides simple and promising synthesis routes to obtain TiO2/ZIF-67 nanocomposites for potential use as new antimicrobial agents.

In an attempt to increase the biological activity of the 1,2,4-triazolo[1,5-a]pyrimidine scaffold through complexation with essential metal ions, the complexes trans-[Cu(mptp)(2)Cl-2] (1), [Zn(mptp)Cl-2(DMSO)] (2) (mptp: 5-methyl-7-phenyl-1,2,4-triazolo[1,5-a]pyrimidine), [Cu-2(dmtp)(4)Cl-4]center dot 2H(2)O (3) and [Zn(dmtp)(2)Cl-2] (4) (dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine), were synthesized and characterized as new antiproliferative and antimicrobial species. Both complexes (1) and (2) crystallize in the P2(1)/n monoclinic space group, with the tetrahedral surroundings generating a square-planar stereochemistry in the Cu(II) complex and a tetrahedral stereochemistry in the Zn(II) species. The mononuclear units are interconnected in a supramolecular network through pi-pi interactions between the pyrimidine moiety and the phenyl ring in (1) while supramolecular chains resulting from C-H center dot center dot center dot pi interactions were observed in (2). All complexes exhibit an antiproliferative effect against B16 tumor cells and improved antibacterial and antifungal activities compared to the free ligands. Complex (3) displays the best antimicrobial activity against all four tested strains, both in the planktonic and biofilm-embedded states, which can be correlated to its stronger DNA-binding and nuclease-activity traits.

The remarkable properties of Eu2+-activated phosphors, related to the broad and intense luminescence of Eu2+ ions, showed a high potential for a wide range of optical-related applications. Oxy-fluoride glass-ceramic containing Europium (II)-doped CaF2 nanocrystals embedded in silica matrix were produced in two steps: glass-ceramization in air at 800 degrees with Eu3+-doped CaF2 nanocrystals embedded followed by Eu3+ to Eu2+ reduction during annealing in reducing atmosphere. The broad, blue luminescence band at 425 nm and with the long, weak tail in the visible range is assigned to the d -> f type transition of the Eu2+ located inside the CaF2 nanocrystals in substitutional and perturbed sites, respectively; the photoluminescence quantum yield was about 0.76. The X-ray photoelectron spectroscopy and Electron paramagnetic spectroscopy confirmed the presence of Eu2+ inside the CaF2 nanocrystals. Thermoluminescence curves recorded after X-ray irradiation of un-doped and Eu2+-doped glass-ceramics showed a single dominant glow peak at 85 degrees C related to the recombination between F centers and Eu2+ related hole within the CaF2 nanocrystals. The applicability of the procedure can be tested to obtain an oxy-fluoride glass-ceramic doped with other divalent ions such as Sm2+, Yb2+, as nanophosphors for radiation detector or photonics-related applications.

Polycrystalline La(0.8)K(0.2-x)Pb(x)MnO3 (x = 0.05, 0.10, 0.15, 0.20) ceramics were successfully prepared by flash combustion route and their structural, morphological, magnetic and magnetocaloric properties were investi-gated. Structural analyses using X-ray diffraction reveal that all samples are crystallized in the rhombohedral structure and belong to R c space group. The increase of Pb doping does not modify the crystalline structure but changes the grain size and lattice parameters. X-ray photoelectron spectroscopy (XPS) fitting results of Mn 2p peaks confirmed the coexistence of Mn3+ and Mn4+ ions which contribute to the double exchange interactions improving the ferromagnetic order in the samples. The magnetization's temperature and magnetic field de-pendences indicate a second-order ferromagnetic-paramagnetic transition of the ceramics. A significant mag-netic entropy change near room temperature was observed for La0.8K0.1Pb0.1MnO3, showing considerable magnetocaloric properties. Furthermore, electron paramagnetic resonance spectroscopy (EPR) was also used to examine the ferromagnetic-paramagnetic transition.

Tunable blue-white-orange emitting LaPO4:Ce3+/Mn2+/Zr4+(LPCMZ) phosphors have been synthesized by co precipitation followed by calcination. The X-ray diffraction (XRD) shows the phase transition from hexagonal to monoclinic between 600 and 700 ?C, accompanied by the increase of average nanocrystallites size from 8 to 64 nm. The Raman measurements revealed the vibrational modes associated with the LPCMZ crystalline phases, where the band positions and the full width at half maximum values depend on the structural parameters and nanocrystals size. For low-temperature calcination of 500 ?C, scanning electron microscopy (SEM) revealed nanoclusters composed of thinner nanoneedles, which developed into a rod-like self-assembly shape for higher calcination temperatures at around 900 ?C. Electron paramagnetic resonance (EPR) spectroscopy reveals a broad isotropic EPR signal, assigned to agglomerated/clustered Mn2+ ions, which are dispersed only at high temperatures above 900 ?C. The photoluminescence spectra recorded under UV-excitation of Ce3+ ions showed the Mn2+ green/red (546, 630 nm) emissions due to an energy transfer (ET) between Ce3+ and Mn2+. Depending on the calcination temperature, the Mn2+ emission color can be finely adjusted from blue to white and orange.

A series of LaPO4:Ce3+/Mn2+/xZr(4+) (LPOCM:xZr(4+)) (0% <= x Mn2+) being discussed in detail. Under UV-excitation of Ce3+, typical green-red PL emission is observed for the LPOCM:xZr(4+) phosphors, which is attributed to the T-4(1)(G) -> (6)A(1)(S) transition of the Mn2+ ion. The charge compensation strategy achieved the Mn2+ PL-enhancement and color-tuning effect in LPOCM:xZr(4+) phosphors. A strong blue emission with color purity of up to 97% is observed in the Ce3+ singly-doped sample. Cold white light emission can be obtained by doping 5% Zr4+ in LPOCM phosphor under UV irradiation. The corresponding CIE 1931 coordinates were inferred to be (0.309, 0.329), close to the standard white emission (0.330, 0.330). The color was tuned towards whitish-orange/red emissions for higher Zr4+ concentrations (15% and 30%). These findings indicate that the charge compensation approach can greatly improve the PL and color-tunable properties of LPOCM:xZr(4+) phosphors.

The species cis-[Cu(tbg)(2)](ClO4)(2) (CuTP) (tbg: 1-(o-tolyl)biguanide) was designed as a novel antimicrobial and biocompatible agent. The single-crystal X-ray diffraction revealed a mononuclear species with a very interesting structure consisting of two tautomeric forms of tbg arranged in a cis-configuration. A complex hydrogen bond network with perchlorate anions involved in different interactions leads to a supramolecular structure. The EPR data indicated the formation of a stable cis-trans mixture in dimethylsulfoxide. Moreover, the EPR experiments evidenced no activity against the superoxide radical (O-2 center dot(-)) but scavenging ability of the hydroxyl radical (HO center dot). This complex exhibited excellent antibacterial properties against planktonic and biofilm embedded gram-negative (Klebsiella pneumoniae, Enterobacter cloacae) and gram-positive (Bacillus subtilis, Lysteria monocytogenes) bacteria. The best efficiency was noticed against E. cloacae and L. monocytogenes with minimal inhibitory concentration and minimal biofilm eradication for a concentration value of 1.95 mu g/ml. One of the possible mechanisms of antimicrobial activity is represented by reactive oxygen species (ROS) generation. The complex was not cytotoxic on L929 fibroblasts. The in silico analysis confirmed the drug-likeness and safety profile of the tested compound and its potential for developing novel antimicrobial and therapeutic tools, targeting other clinical conditions besides infectious diseases.

The hematite-based nanomaterials are involved in several catalytic organic and inorganic processes, including water decontamination from organic pollutants. In order to develop such species, a series of bimetallic hematite-based nanocomposites were obtained by some goethite composites-controlled calcination. Their composition consists of various phases such as alpha-FeOOH, alpha-Fe2O3 or gamma-Fe2O3 combined with amorphous (Mn2O3, Co3O4, NiO, ZnO) or crystalline (CuO) oxides of the second transition ion from the structure. The component dimensions, either in the 10-30 or in the 100-200 nm range, together with the quasi-spherical or nanorod-like shapes, were provided by Mossbauer spectroscopy and powder X-ray diffraction as well as transmission electron microscopy data. The textural characterization showed a decrease in the specific area of the hematite-based nanocomposites compared with corresponding goethites, with the pore volume ranging between 0.219 and 0.278 cm(3)g(-1). The best catalytic activity concerning indigo carmine removal from water in hydrogen peroxide presence was exhibited by a copper-containing hematite-based nanocomposite sample that reached a dye removal extent of over 99%, which correlates with both the base/acid site ratio and pore size. Moreover, Cu-hbnc preserves its catalytic activity even after four recyclings, when it still reached a dye removal extent higher than 90%.

The current study aims to present and discuss the results obtained by complementary archaeometric methods applied for the first time on white pigments inlaid on excised pottery of the Boian-Vidra tradition (Early Chalcolithic, c. 4900-4600 BCE). The samples came from three settlements located in Southern Romania (Sultana-Ghetarie, Vidra, and Vladiceasca). They were selected considering that the pottery was produced in approximately contemporary sites, located relatively close to each other in the same geographical region, namely the Romanian Plain. The experimental part included the analysis of local samples of carbonate concretions and prehistoric animal bone ash as reference materials. Archaeometric investigations consisted in applying "in-air" PIXE and EDX methods for the chemical composition, XRD and FTIR for mineralogical data, SEM for microstructure observation, and EPR for the characterisation of the paramagnetic centres. Calcite, bone ash, and silica rich sediments were identified as the primary decorating pigments. The mixtures of calcite and bone-ash observed in 13 samples were specific to the sites at Vidra and Vladiceasca. Silica-rich sediments from distant sources were the main whitening materials in two samples from Vladiceasca, while for the samples from Sultana-Ghetarie, calcite was the only whitening mineral. The results show with a high degree of confidence the use of both local (i.e., carbonate neo-formations and bone ash) and exotic (silica-rich sediments) raw materials to obtain the white pigment applied to Boian-Vidra pottery. Thus, the current data show the adaptability of the potters with respect to the surrounding resources and also provide new evidence for a vast trade network of raw materials and/or finished products in the Lower Danube area during the Early Chalcolithic. The deliberate mixing of two whitening materials from different sources could be a technological choice and may highlight complex symbolic behaviours.

Melanoma is a skin cancer characterized by rapid growth and spread for which current therapies produce both resistance and increased risk of infection. To develop new anti-melanoma biocompatible species, the series of complexes Cu(N-N)(bzac)(X)center dot nH(2)O (N-N: 1,10-phenanthroline/2,2 '-bipyridine, Hbzac: 1-phenyl-1,3-butanedione, X: NO3/ClO4, and n = 0, 1) was studied. Single-crystal X-ray diffraction revealed a mononuclear structure for all complexes. The ability of the complexes to scavenge or trap reactive oxygen species such as O-2 center dot(-) and HO center dot was proved by EPR spectroscopy experiments. All complexes inhibited B16 murine melanoma cells in a dose-dependent and nanomolar range, but the complexes with 1,10-phenanthroline were more active. Moreover, comparative activity on B16 and healthy BJ cells revealed a therapeutic index of 1.27-2.24. Bioinformatic methods were used to calculate the drug-likeness, pharmacokinetic, pharmacogenomic, and pharmacodynamic profiles of the compounds. The results showed that all compounds exhibit drug-likeness features, as well as promising absorption, distribution, metabolism, and excretion (ADME) properties, and no toxicity. The pharmacodynamics results showed that the neutral species appear to be good candidates for antitumor molecular targets (Tyrosyl-DNA phosphodiesterase 1, DNA-(apurinic or apyrimidinic site) lyase or Kruppel-like factor 5). Furthermore, the pharmacogenomic results showed a good affinity of the copper(II) complexes for the human cytochrome. These results recommend complexes bearing 1,10-phenanthroline as good candidates for developing drugs to melanoma alternative treatment.

The present study aimed to assess the feasibility of developing low-cost multipurpose iron oxide/TiO2 nanocomposites (NCs) for use in combined antitumor therapies and water treatment applications. Larger size (approximate to 100 nm) iron oxide nanoparticles (IONPs) formed magnetic core-TiO2 shell structures at high Fe/Ti ratios and solid dispersions of IONPs embedded in TiO2 matrices when the Fe/Ti ratio was low. When the size of the iron phase was comparable to the size of the crystallized TiO2 nanoparticles (approximate to 10 nm), the obtained nanocomposites consisted of randomly mixed aggregates of TiO2 and IONPs. The best inductive heating and ROS photogeneration properties were shown by the NCs synthesized at 400 degrees C which contained the minimum amount of alpha-Fe2O3 and sufficiently crystallized anatase TiO2. Their cytocompatibility was assessed on cultured human and murine fibroblast cells and analyzed in relation to the adsorption of bovine serum albumin from the culture medium onto their surface. The tested nanocomposites showed excellent cytocompatibility to human fibroblast cells. The results also indicated that the environment (i.e. phosphate buffer or culture medium) used to disperse the nanomaterials prior to performing the viability tests can have a significant impact on their cytotoxicity.

In an attempt to propose new applications for the biomedical field, complexes with mixed ligands {[Cu(bpy)(2)(mu 2OClO3)]ClO4}n (1) and [Cu(phen)(2)(OH2)](ClO4)(2) (2) (bpy: 2,2'-biyridine; phen and 1,10-phenantroline) were evaluated for their antibacterial and cytotoxicicity features and for the elucidation of some of the mechanisms involved. Complex (2) proved to be a very potent antibacterial agent, exhibing MIC and MBEC values 2 to 54 times lower than those obtained for complex (1) against both susceptible or resistant Gram-positive and Gram-negative strains, in planktonic or biofilm growth state. In exchange, complex (1) exhibited selective cytotoxicity against melanoma tumor cells (B16), proving a promising potential for developing novel anticancer drugs. The possible mechanisms of both antimicrobial and antitumor activity of the copper(II) complexes is their DNA intercalative ability coupled with ROS generation. The obtained results recommend the two complexes for further development as multipurpose copper-containing drugs.

Goethite based nanocomposites with a different composition such as 6FeO(OH)center dot MnO(OH)center dot 0.5H(2)O (Mn-composite), xFeO(OH)center dot M(OH)(2)center dot yH(2)O (Co-composite (M: Co, x = 12, y = 3), Ni-composite (M: Ni, x = 7, y = 2)) and xFeO(OH)center dot MO center dot yH(2)O (Cu-composite (M: Cu, x = 5.5, y = 3), Zn-composite (M: Zn, x = 6, y = 1.5)) have been prepared by a soft chemical synthesis consisting in acetate hydrolysis. The data provided by Fourier transform infrared (FTIR), ultraviolet-visible-near infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR) and Mossbauer spectra account for a slight modification of all composites' physicochemical properties compared to the starting material. Powder X-ray diffraction and transmission electron microscopy (TEM) investigations revealed the secondary phase nature and presence along with that of goethite. The TEM data are also consistent with a nano rod-like morphology with a 5-10 nm width and an average length of 40 nm. The catalytic oxidation of cyclooctene with O-2 using isobutyraldehyde as reductant and acetonitrile as a solvent was performed in batch conditions for 5 h at room temperature. The selectivity for the epoxide was higher than 99% for all tested solids. The conversion of cyclooctene decreased from 55% to 4% following the same order of variance as the base/acid sites ratio: Mn-composite > Fe-composite > Co-composite > Ni-composite > Zn-composite > Cu-composite. The 6FeO(OH)center dot MnO(OH)center dot 0.5H(2)O (Mn-composite) exhibited the most promising catalytic activity in cyclooctene oxidation, which can be correlated with the redox ability of Mn(iii) combined with the increased base character of this solid. The catalytic activity of this sample decreases by 10% after several successive reaction cycles.

Europium doped (0.1% and 1%) chlomborate BaO-B2O3-BaCl2 glass and glass-ceramic with embedded BaCl2 nanocrystals have been synthesised, investigated, and compared with the corresponding nanocrystalline powder. The structural analysis of the glass evidenced ionic bonds characteristic to the glass host structure and compositional changes during the melting. X-ray diffraction and transmission electron microscopy revealed the formation of orthorhombic BaCl2 nanocrystals of about tens on nm in size and a smaller amount of BaB2O4 nanocrystals. Structural analysis of the Eu2+-doped BaCl2 nanocrystals has shown a distortion of the crystalline cell assigned to the growth process, affected by defects and ionic impurities. Photoluminescence spectra of the glass-ceramic revealed Eu3+ and Eu2+ luminescent ion species, but only Eu2+ is incorporated within the BaCl2 nanocrystalline phase. Electron paramagnetic resonance measurements in X-band sustain the presence of Eu2+ ions. The EPR parameters (g values and hyperfine constants) resulting from the Q-band EPR spectra simulations recorded on glass-ceramic are similar to those in Eu2+-doped BaCl2 and confirmed the partial incorporation of Eu2+ ions within the BaCl2:Eu2+ nanocrystals in the glass-ceramics.

In this work, the structural, thermal, vibrational, morphological, magnetic and optical properties of LaPO4:Ce/RE/Me (RE=Nd3+, Tb3+; Me-Cr3+, Mn2+) and LaPO4:Yb3+/Er3+ phosphors prepared by the co-precipitation method are presented. The obtained materials crystallized in monoclinic structure with the P2(1)/n space group and the particles were of nanorod shape with about 200 nm in length and the diameter approximately 19 nm. The presence of dopant ions was confirmed by both electron paramagnetic resonance (EPR) and UV-visible spectroscopies. In addition, the down-conversion (DC) and up-conversion (UC) of the LaPO4 nanophosphors via the 275 and 980 nm excitations, respectively, were considered, and a wide range of electronic transitions was observed. Based on the photoluminescence (PL) spectra, there is an efficient energy transfer (ET) process from Ce3+ donors to Nd3+ and Tb3+ acceptors, and the computed ET efficiency was 70% and 88%, respectively. The Ce3+/Cr3+ and Ce3+/Mn2+ doped LaPO4 showed weak far-red and green luminescence with much smaller ET efficiency of about 3.7 and 0.4%, respectively. LaPO4:Yb3+/Er3+ showed UC luminescence under the 980 nm laser radiation, and the resulted red and green light was attributed to the Er3+ transitions.

Lanthanum orthophosphate (LaPO4) and La0.95-xCe0.05MnxPO4 (x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO4 crystalline structure and an increase of the lattice strain as a consequence of the Mn2+ and Ce3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 +/- 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn2+ in isolated species, but also as agglomerates. Ce3+ and Mn2+ doping of LaPO4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce3+ to Mn2+ ions, green emission of Mn2+ ions at around 550 nm was observed upon 275 nm excitation.

Rare-earth elements are widely used as doping materials as they considerably change the semiconductor optical, electrical, magnetic and radiative properties. This work explores the influence of Gadolinium (Gd) as a dopant on the radiative, optical and magnetic properties of the Zinc Selenide (ZnSe). ZnSe single crystals were grown by the physical transport method and doped during the growth process using a GdSe source. A wide range of characterization equipment was employed to analyze the obtained ZnSe:Gd single crystals. Intracenter radiative transition of the Gd has not been detected. Gd ions activate the background impurities, causing radiative transitions from the conduction band to the Cu2+ level and intracenter transitions within V3+, V2+ and Cr2+ ions. At the same time, the edge band intensity is dependent on the dopant concentration. Optical transmittance decreases, but the position of the fundamental absorption band is unchanged. Single crystals have a zinc blende crystal structure, and Gd ions do not form complexes with native defects or background impurities.

Novel complexes of type [Cu(N-N)(dmtp)(2)(OH2)](ClO4)(2)& BULL;dmtp ((1) N-N: 2,2 & PRIME;-bipyridine; (2) L: 1,10-phenantroline and dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine) were designed in order to obtain biologically active compounds. Complexes were characterized as mononuclear species that crystallized in the space group P-1 of the triclinic system with a square pyramidal geometry around the copper (II). In addition to the antiproliferative effect on murine melanoma B16 cells, complex (1) exhibited low toxicity on normal BJ cells and did not affect membrane integrity. Complex (2) proved to be a more potent antimicrobial in comparison with (1), but both compounds were more active in comparison with dmtp-both against planktonic cells and biofilms. A stronger antimicrobial and antibiofilm effect was noticed against the Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). Both electron paramagnetic resonance (EPR) and Saccharomyces cerevisiae studies indicated that the complexes were scavengers rather than reactive oxygen species promoters. Their DNA intercalating capacity was evidenced by modifications in both absorption and fluorescence spectra. Furthermore, both complexes exhibited nuclease-like activity, which increased in the presence of hydrogen peroxide.

Hybrid perovskites based solar cells have demonstrated high conversion efficiency but poor long-term stability. This study reports on the results obtained after doping the CH3NH3PbI2.6Cl0.4 mixed halide perovskite with imidazolium (C3N2H5+, denoted IM) on the "A site" position of a perovskite, to improve photovoltaic performances and stability of hybrid perovskite solar cells. The perovskite films were investigated exhaustively by different characterization techniques: X-ray diffraction, Atomic Force Microscopy, Scanning Electron Microscopy, UV-Vis, X-ray Photoelectron Electron Paramagnetic Resonance spectroscopies, Impedance Spectroscopy and Incident Photon-to-Electron Conversion Efficiency. The photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The amount of IM inserted in the perovskite play a key role on the film properties. The calculated new tolerance factors according to the "globularity factor" are experimentally proved and thus at doping concentrations greater than 20% for CH3NH3PbI2.6Cl0.4 perovskite the 3D structure is no longer obtained. However, below this value, the IM substituted perovskite film possesses an improved film quality and crystallinity as compared to the pristine film. Substituting MA+ with IM+ provides a favorable way to reduce recombination processes and shows great potential to achieve high stability, and an improved charge generation, resulting in increased PCE values. We find that the optimal percentage of imidazolium incorporation to achieve better stability of solar cells is 6%.

We observe a strong thermally controlled magnon-mediated interlayer coupling of two ferromagnetic layers via an antiferromagnetic spacer in spin-valve type trilayers. The effect manifests itself as a coherent switching as well as collective resonant precession of the two ferromagnets, which can be controlled by varying temperature and the spacer thickness. We explain the observed behavior as due to a strong hybridization of the ferro- and antiferromagnetic magnon modes in the trilayer at temperatures just below the Neel temperature of the antiferromagnetic spacer.

The aim of this paper is the study of the thermal behavior of the simonkolleite Zn-5(OH)(8)Cl-2 center dot H2O (ZHC) by electron paramagnetic resonance (EPR) spectroscopy, in particular. It is well known that during heating ZHC undergoes a complex transformation which involves several overlapping stages. However, with reference to the data reported on this subject, it can be concluded that there is still an ongoing debate regarding the intermediate stages of this process. The data presented in this study support a simple decomposition process of the ZHC prepared using the precipitation method. The EPR data correlated to the data obtained by other experimental techniques, such as XRD, TEM, SEM and EDX, indicate that during the thermal treatment the ZHC suffers a partial decomposition to ZnO with no intermediate products. After annealing at 500 degrees C for 1 h, a recombination process of ZHC is observed. Moreover, the kinetics associated to these decomposition steps were determined and the evolution of the paramagnetic centers was also followed and studied. This study offers new information related to the thermal behavior of ZHC, especially regarding the EPR data which is reported for the first time on this subject and material.

Structural analysis of the Eu2+-doped BaCl2 nanocrystals and the doping process was monitored and characterized via electron paramagnetic resonance spectroscopy. Structural analysis has shown a slight distortion of the cell which is reflected in the low value of microstrain and the Eu2+-doping effect is limited to the first order chlorine ions neighbors of Ba2+. Electron paramagnetic resonance measurements have indicated the presence of the Eu2+-dopant ions in the BaCl2 host matrix with a solubility limit of about 2%. From the spectra simulation, the isotropic g-value g(iso) = 1.9951(7), the isotropic hyperfine coupling constant A(iso)= 42.4 MHz and the high-order zero-field splitting parameters from the crystal field B-2(0) = 21 MHz and B-2(2)= -493 MHz were obtained. During X-ray irradiation, defects are produced and stabilized by the Eu2+ dopant ions. The single dominant thermoluminescence peak at 132 degrees C (activation energy E = 1.1 eV) was assigned to the recombination of the F(Cl)-center with Eu2+ related hole centers. (C) 2019 Elsevier B.V. All rights reserved.

Complexes with mixed ligands [Cu(N-N)(2)(pmtp)](ClO4)(2)((1) N-N: 2,2 '-bipyridine; (2) L: 1,10-phenanthroline and pmpt: 5-phenyl-7-methyl-1,2,4-triazolo[1,5-a]pyrimidine) were synthesized and structurally and biologically characterized. Compound (1) crystallizes into space groupPaand (2) inP-1. Both complexes display an intermediate stereochemistry between the two five-coordinated ones. The biological tests indicated that the two compounds exhibited superoxide scavenging capacity, intercalative DNA properties, and metallonuclease activity. Tests on various cell systems indicated that the two complexes neither interfere with the proliferation ofSaccharomyces cerevisiaeor BJ healthy skin cells, nor cause hemolysis in the active concentration range. Nevertheless, the compounds showed antibacterial potential, with complex (2) being significantly more active than complex (1) against all tested bacterial strains, both in planktonic and biofilm growth state. Both complexes exhibited a very good activity against B16 melanoma cells, with a higher specificity being displayed by compound (1). Taken together, the results indicate that complexes (1) and (2) have specific biological relevance, with potential for the development of antitumor or antimicrobial drugs.

Lanthanum orthophosphate (LaPO4) and La0.95-xCe0.05MnxPO4 (x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO4 crystalline structure and an increase of the lattice strain as a consequence of the Mn2+ and Ce3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 +/- 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn2+ in isolated species, but also as agglomerates. Ce3+ and Mn2+ doping of LaPO4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce3+ to Mn2+ ions, green emission of Mn2+ ions at around 550 nm was observed upon 275 nm excitation.

The species cis-[Cu(tbg)(2)](ClO4)(2) (CuTP) (tbg: 1-(o-tolyl)biguanide) was designed as a novel antimicrobial and biocompatible agent. The single-crystal X-ray diffraction revealed a mononuclear species with a very interesting structure consisting of two tautomeric forms of tbg arranged in a cis-configuration. A complex hydrogen bond network with perchlorate anions involved in different interactions leads to a supramolecular structure. The EPR data indicated the formation of a stable cis-trans mixture in dimethylsulfoxide. Moreover, the EPR experiments evidenced no activity against the superoxide radical (O-2 center dot(-)) but scavenging ability of the hydroxyl radical (HO center dot). This complex exhibited excellent antibacterial properties against planktonic and biofilm embedded gram-negative (Klebsiella pneumoniae, Enterobacter cloacae) and gram-positive (Bacillus subtilis, Lysteria monocytogenes) bacteria. The best efficiency was noticed against E. cloacae and L. monocytogenes with minimal inhibitory concentration and minimal biofilm eradication for a concentration value of 1.95 mu g/ml. One of the possible mechanisms of antimicrobial activity is represented by reactive oxygen species (ROS) generation. The complex was not cytotoxic on L929 fibroblasts. The in silico analysis confirmed the drug-likeness and safety profile of the tested compound and its potential for developing novel antimicrobial and therapeutic tools, targeting other clinical conditions besides infectious diseases.