4d 4f Research Articles

HAXPES Cr Kα measurement of bulk hafnium

Hafnium was analyzed using high-resolution high energy x-ray photoelectron spectroscopy (HAXPES). The HAXPES spectra of Hafnium obtained using monochromatic Cr Kα radiation at 5414.8 eV include survey scan and high-resolution spectra of Hf 3s, Hf 3p3/2, Hf 3d5/2, Hf 4p3/2, Hf 4d, and Hf 4f.

Study of the 6.x nm short wavelength radiation spectra of laser-produced erbium plasmas for BEUV lithography

Beyond extreme ultraviolet (BEUV) radiation with a wavelength of 6.x nm for lithography is responsible for reducing the source wavelength to enable continued miniaturization of semiconductor devices. In this work, the Required BEUV light at 6.x nm wavelength was generated in dense and hot Nd:YAG laser-produced Er plasmas. The spectral contributions from the 4p–4d and 4d–4f transitions of singly, doubly and triply excited states of Er XXIV–Er XXXII in the BEUV band were calculated using Cowan and the Flexible Atomic Code. It was also found that the radiative transitions between multiply excited states dominate the narrow wavelength window around 6.x nm. Under the assumption of collisional radiative equilibrium of the laser-produced Er plasmas, the relative ion abundance in the experiment was inferred. Using the Boltzmann quantum state energy level distribution and Gram–Charlier fitting function of unresolved transition arrays (UTAs), the synthetic spectrum around 6.x nm was finally obtained and compared with the experimental spectrum. The spatio-temporal distributions of electron density and electron temperature were calculated based on radiation hydrodynamic simulation in order to identify the contributions of various ionic states to the UTAs arising from the Er plasmas near 6.x nm.

Possible Half‐Metallic Ferromagnetism in Rare‐Earth Metals Based Ruthenate Double Perovskites: Ba2RERuO6 (RE = Dy, Tm)

Herein, a systematic mechanism behind long‐range ferromagnetic (FM) ground state is described based on 4d–4f interactions demonstrated in strongly correlated Ba2DyRuO6 and Ba2TmRuO6 double‐perovskite (DP) systems. Density functional theory (DFT) + U based possible half‐metallic FM nature of the considered DPs is realized along with integer values of spin magnetic moments (8.0 and 3.0 μB f.u.−1, respectively). This robust FM configuration is mainly dependent on Ru5+ and rare‐earth (RE3+) elements highlighting the importance of B‐site cationic ordering approach used in present study. The optical response of considered rare‐earth ruthenate DPs is also scrutinized, implying their potential usage in optical filter devices. The DFT + U based results are validated via comparing with existing experimental literature. This study suggests Ba2DyRuO6 and Ba2TmRuO6 as a novel addition to the family of half metals and will surely pave the way for materialists to experimentally explore their physical features for spintronic usage.

Large magnetodielectric coupling in the vicinity of metamagnetic transition in 6H–perovskite Ba3GdRu2O9

The 6H-perovskites Ba3RRu2O9 (R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of 4d–4f magnetic interactions. Here, a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba3GdRu2O9 is reported. The signature of long-range antiferromagnetic (AFM) ordering ∼14.8 K (T N) is evident from the magnetization and heat capacity studies. The T N shifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magnetization at 2 K shows three metamagnetic transitions with the opening of small hysteresis in different regions. A new transition at T 1 emerges after the onset of the first metamagnetic transition. Complex magnetic behavior is observed in different magnetic field regions whereas these field regions themselves vary with the temperature. Dielectric response recorded at zero and 80 kOe field exhibits the development of MD coupling well above T N. The MD coupling (∼4.5% at 10 K) is enhanced by 25% as compared to the Dy counterpart. Effect of complex magnetic behavior is also conveyed in the MD results where the maximum value of MD coupling is observed in the vicinity of 10 K (onset of T 1) and near the second metamagnetic transition. Our investigation suggests that both Gd and Ru moments align simultaneously at T N. Short-range magnetic ordering is possibly responsible for MD coupling above T N.

Soft x-ray spectra of cerium laser-produced plasmas

Spectra of laser-produced plasmas of cerium have been recorded in the 1.5 to 15.5 nm spectral region. The plasmas were formed using the frequency doubled pulsed output of a neodymium-doped yttrium aluminium garnet (Nd:YAG) laser at 532 nm. At the power densities incident on-target, ranging from 8.6 × 109–2.1 × 1013 W cm−2, Ce4+ to Ce27+ ions gave rise to emission from Δn = 0, 1 transitions to final states where n = 4. The spectra are dominated by an intense unresolved transition array (UTA) in the 8–10 nm region arising from n = 4 to n = 4 transitions. Two distinct components of this UTA are observed whose appearance is strongly dependent on laser power density, corresponding to transitions involving ions with open 4d and open 4f subshells, the latter at longer wavelengths. Multiple other transition arrays are identified and UTA statistics are given. The analysis was aided by atomic structure calculations and the use of a steady state collisional-radiative model.

Synthesis of β-Enaminonitrile-Linked 8-Methoxy-1H-Benzo[f]Chromene Moieties and Analysis of Their Antitumor Mechanisms.

A series of aryl-substituted 3-amino-1-aryl-8-methoxy-1H-benzo[f]chromene-2-carbonitriles (4a–4q) were designed and synthesized via reaction of 6-methoxy-2-naphthol with a mixture of appropriate aromatic aldehydes and malononitrile under microwave conditions. The structures of the novel compounds 4b, 4c, 4f, 4g, 4i, 4l, 4m, and 4o–4q were established according to IR, 1H-NMR, 13C-NMR/13C-NMR-DEPT, and MS. The benzochromene derivative 4c with a single chlorine at the meta position of the phenyl ring and, to a lesser extent, other benzochromenes with monohalogenated phenyl ring (4a, 4c–4f) exhibited the highest cytotoxicity against six human cancer cell lines MDA-MB-231, A549, HeLa, MIA PaCa-2, 5,637, and Hep G2. The mechanisms of the cytotoxic activities of benzochromenes with monohalogenated phenyl ring (4a, 4c–4f) were further analyzed using triple-negative breast cancer cell line MDA-MB-231. Cell cycle analysis showed accumulation of the treated cells in S phase for 4a, 4d–4f, and S-G2/M phases for 4c. In vivo, 4a and 4c–4f inhibited growth, proliferation, and triggered apoptosis in preestablished breast cancer xenografts grown on the chick chorioallantoic membranes while exhibiting low systemic toxicity. Compounds 4a and 4c–4f increased levels of mitochondrial superoxide and decreased mitochondrial membrane potential resulting in initiation of apoptosis as demonstrated by caspase 3/7 activation. In addition, 4c induced general oxidative stress in cancer cells. The SAR study confirmed that halogens of moderate size at meta or para positions of the pendant phenyl ring enhance the cytotoxic activity of 3-amino-1-aryl-8-methoxy-1H-benzo[f]chromene-2-carbonitriles, and these compounds could serve as leads for the development of novel anticancer therapies.

Resonant photoemission spectroscopy of the ferromagnetic Kondo system CeAgSb2

We study the electronic structure of single crystal CeAgSb2, a low T c ferromagnetic Kondo system, using synchrotron radiation photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). We have carried out Ce 5s, Ce 5p, Sb 4d core level PES as well as Ce 4d–4f resonant PES of the valence band states of CeAgSb2. We also report the resonant PES behavior of Ce 5s and 5p core-levels and the simultaneous intensity suppression of Sb 4d core-level and Ag 4d valence band states across the Ce 4d–4f threshold. The Ce 4d–4f resonant valence band spectra show typical f 0 and f 1 features associated with Kondo behavior. The constant initial state spectra of the f 0 and f 1 features show maxima at different incident photon energies, arising from different relative contributions of surface and bulk character Ce 4f partial density of states. XAS across the Ce 3d–4f M-edge also shows the corresponding final state f 1 and f 2 features. The weak temperature dependence of the XAS spectra between T = 25 K and 300 K could be simulated using a full multiplet calculation combined with a simplified single-impurity Anderson model approach. The calculations confirm the Kondo screening and allows quantification of the bulk Ce 4f electron count in CeAgSb2. The Ce 5s states show an exchange splitting which reflects the local magnetic moment of Ce 4f states. The overall results characterize the bulk and surface sensitive Ce 4f states, and indicate the role of Kondo effect in forming the moderately enhanced heavy-fermion carriers in CeAgSb2.

Investigation of extreme ultraviolet spectra from highly charged holmium ions in 1 μ m laser-produced plasmas

Absolute intensity calibrated extreme ultraviolet spectra radiated by highly charged holmium (Ho) ions from 1 μm Nd:YAG laser generated plasmas in the 1–8 nm wavelength spectral range were measured and investigated. The spectral features show a broad structured continuum-like emission band, most prominent in the wavelength range 6–8 nm, which accounts for more than half of the emitted power. Assuming local thermodynamic equilibrium (LTE) in the laser produced plasmas and using the flexible atomic code and Cowan suite of codes, the wavelengths and LTE-gA values of unresolved transition arrays (UTAs) from E 1-contributing transition arrays 4p–4d, 4d–4f and super transition arrays such as 4p64d k−14f + 4p54d k+1–4p64d k−24f2 + 4p44d k+2 + 4p54d k 4f and 4d10(5s5p) k 4f m−k –4d9(5s5p) k 4f m−k+1 were calculated and shown to be responsible for the strongest observed spectral structure. Transitions between these excited to excited states are considered, since even if only weakly present, they will not be influenced by opacity effects unlike resonance transitions involving ground configurations. Another two intense continuous emission bands at 3–6 nm and 2–3 nm that dominate the spectra in the shorter wavelength range mainly arise from 4d–5p, 4d5s–4d5s5p, 4f–5g, 4f5s–4f5s5g and 4d–5f, 4d5s–4d5s5f, 4p–5s transitions. Spectral line shape parameters of Gaussian fits to the LTE-gA weighted radiation spectra of each Ho ion were given, enabling direct explanation of recorded spectra. Based on the LTE-gA UTAs formalism parameters, reasonable agreement is obtained between the synthetic spectrum and experimental result enabling some of the observed spectral features to be identified.

EUV spectroscopy of Sn5+–Sn10+ ions in an electron beam ion trap and laser-produced plasmas

Emission spectra from multiply-charged Sn5+–Sn10+ ions are recorded from an electron beam ion trap (EBIT) and from laser-produced plasma (LPP) in the extreme ultraviolet range relevant for nanolithographic applications. Features in the wavelength regime between 12.6 and 20.8 nm are studied. Using the Cowan code, emission line features of the charge-state-resolved Sn ion spectra obtained from the EBIT are identified. Emission features from tin LPP either from a liquid micro-droplet or planar solid target are subsequently identified and assigned to specific charge states using the EBIT data. For the planar solid tin target, the 4d–5p transitions of Sn8+–Sn10+ ions are shown to dominate the long-wavelength part of the measured spectrum and transitions of type 4d–4f + 4p–4d are visible in absorption. For the droplet target case, a clear increase in the charge state distribution with increasing laser intensity is observed. This qualitatively demonstrates the potential of using long-wavelength out-of-band emission features to probe the charge states contributing to the strong unresolved transition array at 13.5 nm relevant for nanolithography.

Measurement and analysis of the extreme ultraviolet emission band of laser-produced antimony plasmas

The temporal evolution of extreme ultraviolet (EUV) emission spectra of laser-produced antimony (Sb) plasmas has been measured in the 7–16 nm wavelength region using spatio-temporally resolved lase-produced plasma spectroscopy technique. The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time. The spectral structures were also analyzed according to Hartree–Fock calculations with configuration interaction effects and contributed from 4d–4f, 4d–4p, and 4d–5f unresolved transition arrays of Sb7+–Sb13+. A steady-state collisional-radiative model was used to estimate the electron temperature and density range of Sb plasmas. This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.

Synthesis and Antimicrobial Activity of Sulfur Derivatives of Quinolinium Salts.

A novel method for cleavage of the dithiine ring in 5,12-(dimethyl)-thioqinantrenium bis-chloride 1 “via” reaction with sodium hydrosulfide leads to 1-methyl-3-mercaptoquinoline-4(1H)-thione 2. Further transformation of thiol and thione functions of compound 2 leads to a series of sulfide and disulfide derivatives of quinolinium salts 4 and 6. 1-Methyl-4-chloro-3-benzylthioquinoline chloride 8 was obtained by N-alkylating 4-chloro-3-benzylthioquinoline using dimethyl sulfate. Antimicrobial activity of the obtained compounds was investigated using six Gram-positive and six Gram-negative bacterial strains, as well as Candida albicans yeast. Greater activity was demonstrated towards Gram-positive strains. MIC values for compounds and with benzylthio 4d and benzoylthio 4f substituents in 3-quinoline position were found to be in the 0.5–1 μg/mL range, at a level similar to that of ciprofloxacin (reference). Compounds 4d and 4f also demonstrated interesting antifungal properties (MIC = 1).

Electronic structure of ferromagnetic heavy fermion, YbPdSi, YbPdGe, and YbPtGe studied by photoelectron spectroscopy, x-ray emission spectroscopy, and DFT + DMFT calculations

Electronic structures of ferromagnetic heavy fermion Yb compounds of YbPdSi, YbPdGe, and YbPtGe are studied by photoelectron spectroscopy around the Yb 4d–4f resonance, resonant x-ray emission spectroscopy at the Yb L3 absorption edge, and density functional theory combined with dynamical mean field theory calculations. These compounds all have a temperature-independent intermediate Yb valence with large and small components. The magnitude of the Yb valence is evaluated to be YbPtGe YbPdGe YbPdSi, suggesting that YbPtGe is the closest to the quantum critical point among the three Yb compounds. Our results support the scenario of the coexistence of heavy fermion behavior and ferromagnetic ordering which is described by a magnetically-ordered Kondo lattice where the magnitude of the Kondo effect and the RKKY interaction are comparable.

Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA) emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5–7.5) × 1013 cm−3. The UTA spectral structure was due to emission from 4d–4f transitions in highly charged ions with average charge states of q = 20–40. A numerical simulation successfully reproduced the observed spectral behavior.

Ag+-induced photoluminescence enhancement in lanthanide post-functionalized MOFs and Ag+ sensing.

The robust gallium carboxylate Ga(OH)(btec)·0.5H2O (MIL-61) is selected as a parent MOF to prepare Ln-MIL-61 by PSM. This work investigates the luminescence of Ln-doped MIL-61 (Ln = Eu3+, Tb3+, Sm3+, Dy3+) in the visible light region. Upon 314 nm excitation, the emission spectra of Eu-MIL-61, Tb-MIL-61 and Eu/Tb-MIL-61 all exhibit their respective strong sharp emission bands. However, Sm-MIL-61 and Dy-MIL-61 show very similar emission to MIL-61 and almost no luminescence of Sm3+ and Dy3+. In this work, the weak fluorescence of Sm3+ or Dy3+ doped MIL-61 is effectively sensitized by Ag+. Besides, single-phase white-light emitters based on the resulting 4d-4f heterometallic co-doped MOFs can be realized. Furthermore, Sm-MIL-61 shows more highly sensitive and selective sensing towards Ag+, and is a promising optical sensor for Ag+ detection in a few daily water samples.

A multi-responsive luminescent sensor for organic small-molecule pollutants and metal ions based on a 4d-4f metal-organic framework.

Two silver(i)-lanthanide(iii) heterometallic-organic frameworks (HMOFs) {[Ln3Ag3(BPDC)5(OX)(H2O)7]·7H2O}n (Ln = Tb (1), Gd (2)) have been synthesized via a mixed ligand approach using 2,2'-bipyridine-3,3'-dicarboxylic acid (H2BPDC) and oxalic acid (H2OX) under hydrothermal conditions. Single crystal X-ray diffraction studies showed a (3,4,5)-connected new topology of {3·42·5·62}{3·43·52·63·7}{3·5·62·9·10}{42·5·63}{42·5}{42·6}{43·5·62}{43·63}{43·64·82·10}. Luminescence studies showed that the characteristic emissions of Tb3+ ions are observed in HMOF 1 which can be capable of sensing organic small-molecule pollutants and metal ions. In addition, it can also discriminate the isomers of pentanol as well as quantitatively distinguish benzendiamines which are carcinogenic but used for hair coloring.

A dual-emitting 4d-4f nanocrystalline metal-organic framework as a self-calibrating luminescent sensor for indoor formaldehyde pollution.

A dual-emissive 4d-4f Ag(i)-Eu(iii) functionalized MOF nanocomposite was fabricated and utilized as a self-calibrating luminescent nanoprobe for detecting indoor formaldehyde (FA). The implantation of Ag(+) ions can tune the dual-emissive characters of the material. FA can interact with the Ag(+) ions and induce opposite luminescence behaviors of the two emitters in the singular molecular material, thus realizing its recognition. This nanoprobe for FA exhibits many merits, such as excellent selectivity, high sensitivity with a detection limit of 51 ppb, fast response, room-temperature testing ability, easy preparation and low cost. This is the first example of a MOF-implicated self-calibrated sensor for indoor FA detection.

Temporal behavior of unresolved transition array emission in water window soft x-ray spectral region from multiply charged ions

We have characterized the spectral structure and the temporal history of the laser-produced high-Z multi-charged ion plasmas for the efficient water window soft x-ray sources. Strong unresolved transition array emission was observed due to 4d–4f and 4f–5g transitions from Au, Pb, and Bi plasmas in the 280–700 eV photon energy region. The temporal behavior of the emission was essentially similar of that of the laser pulse with a slight delay between different transitions. These results provide feedback for accurate modeling of the atomic processes with the radiative hydrodynamic simulations.

Heteropentanuclear Oxalato-Bridged nd-4f (n=4, 5) Metal Complexes with NO Ligand: Synthesis, Crystal Structures, Aqueous Stability and Antiproliferative Activity.

A series of heteropentanuclear oxalate-bridged Ru(NO)-Ln (4d–4f) metal complexes of the general formula (nBu4N)5[Ln{RuCl3(μ-ox)(NO)}4], where Ln=Y (2), Gd (3), Tb (4), Dy (5) and ox=oxalate anion, were obtained by treatment of (nBu4N)2[RuCl3(ox)(NO)] (1) with the respective lanthanide salt in 4:1 molar ratio. The compounds were characterized by elemental analysis, IR spectroscopy, electrospray ionization (ESI) mass spectrometry, while 1, 2, and 5 were in addition analyzed by X-ray crystallography, 1 by Ru K-edge XAS and 1 and 2 by 13C NMR spectroscopy. X-ray diffraction showed that in 2 and 5 four complex anions [RuCl3(ox)(NO)]2− are coordinated to YIII and DyIII, respectively, with formation of [Ln{RuCl3(μ-ox)(NO)}4]5− (Ln=Y, Dy). While YIII is eight-coordinate in 2, DyIII is nine-coordinate in 5, with an additional coordination of an EtOH molecule. The negative charge is counterbalanced by five nBu4N+ ions present in the crystal structure. The stability of complexes 2 and 5 in aqueous medium was monitored by UV/Vis spectroscopy. The antiproliferative activity of ruthenium-lanthanide complexes 2–5 were assayed in two human cancer cell lines (HeLa and A549) and in a noncancerous cell line (MRC-5) and compared with those obtained for the previously reported Os(NO)-Ln (5d–4f) analogues (nBu4N)5[Ln{OsCl3(ox)(NO)}4] (Ln=Y (6), Gd (7), Tb (8), Dy (9)). Complexes 2–5 were found to be slightly more active than 1 in inhibiting the proliferation of HeLa and A549 cells, and significantly more cytotoxic than 5d–4f metal complexes 6–9 in terms of IC50 values. The highest antiproliferative activity with IC50 values of 20.0 and 22.4 μM was found for 4 in HeLa and A549 cell lines, respectively. These cytotoxicity results are in accord with the presented ICP-MS data, indicating five- to eightfold greater accumulation of ruthenium versus osmium in human A549 cancer cells.

Ketenes from N-(2-Pyridyl)amides

Methoxycarbonylketene 4a, methoxycarbonyl(methyl)ketene 4b, chloroketene 4c, cyanoketene 4d, diphenylketene 4e, and 2-pyridylketene 4f have been generated by flash vacuum thermolysis of the corresponding 2-pyridylacetamide derivatives 3a–f and isolated in Ar matrices for FT-IR spectroscopic characterisation. The N-(2-pyridyl)-2-pyridylacetamide 3f yielded 2-pyridyl isocyanate in addition to 2-pyridylketene.

Syntheses, crystal structures and properties of series of 4d–4f ln(III)–Ag(I) heterometallic coordination polymers

By control of the experimental parameters such as ligands, pH value and reacting temperature, series of three-dimensional (3D) 4d–4f Ln(III)–Ag(I) porous coordination polymers (PCPs) with interesting chain-layer construction, namely, {[LnIIIAgI(na)(ina)(ox)]·2(H2O)}n [Ln=Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Ho(6), Y(7), Yb(8)], have been successfully synthesized under hydrothermal conditions and structurally characterized. All the complexes are characterized by elemental analyses, FT-IR spectroscopy, Powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Furthermore, the luminescence properties of compounds 2 and 4 and the magsnetic properties of complexes 3 and 5 were also investigated in detail.