Surface morphology and luminescence characterization of β-FeSi2 thin films prepared by pulsed laser deposition

β-FeSi₂ thin films were prepared on Si (1 1 1) substrates by pulsed laser deposition (PLD) with a sintering FeSi₂ target and an electrolytic Fe target. The thin films without micron-size droplets were prepared using the electrolytic Fe target; however, the surface without droplets was remarkably rougher using the Fe target than using the FeSi₂ target. After deposition at 600 °C and then annealing at 900 °C for 20 h, XRD indicated that the thin film prepared using the Fe target had a poly-axis-orientation, but that prepared using the FeSi₂ target had a one-axis-orientation. The PL spectra of the thin films prepared using the FeSi₂ and Fe targets at a growth temperature of 600 °C and subsequently annealed at 900 °C for 20 h had A-, B- and C-bands. Moreover, it was found that the main peak at 0.808 eV (A-band) in the PL spectrum of the thin films prepared using the FeSi₂ target was the intrinsic luminescence of β-FeSi₂ from the dependence of PL peak energy on temperature and excitation power density.     

Americium and plutonium separation by extraction chromatography for determination by accelerator mass spectrometry

A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N′,N′-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8 M HNO₃ with 0.05 M NaNO₂ before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO₃, and desorbed with 0.1 M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02 M TiCl₃ facilitated the complete desorption of Pu. Interferences (e.g. Ca²⁺, Fe³⁺) were washed off from the resin bed with excess HNO₃. Using NdF_3, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7 ± 5.3% and 95.5 ± 4.6% for ²⁴¹Am and ²⁴²Pu respectively in reagents without a matrix. The recoveries of the same isotopes were 99.1 ± 6.0 and 96.8 ± 5.3% respectively in garden soil. The robustness of the method was validated using certified reference materials (IAEA 384 and IAEA 385). The measurements agree with the certified values over a range of about 1–100 Bq kg⁻¹. The single column separation of Pu and Am saves reagents, separation time, and cost.     

Investigation of reactive acrylic monomers for their effect on the temperature range and operating voltage of polymer-stabilised optically isotropic liquid crystal blue phases

Synthesis of various reactive acrylic monomers (RMs) to be used as components in liquid crystalline blue phase (LCBP) mixtures has been carried out in order to investigate their effect on temperature range and operating voltage. All the newly synthesised RMs were fully purified and characterised. These were added in various molar ratios to LCBP mixtures, which were stabilised by ultraviolet polymerisation, and improvements in the operating voltage and temperature range were studied. The compatibility of LCBP and monomer side-chains was investigated in terms of polarity and alkyl chain length.     

Fabrication of interconnected 1D molecular lines along and across the dimer rows on the Si(100)-(2 x 1)-H surface through the radical chain reaction

To realize nanoscale wiring in two dimensions (2D), the fabrication of interconnected one-dimensional (1D) molecular lines through the radical chain reaction of alkene molecules (CH2=CH-R) on the H-terminated Si(100)-(2 x 1) surface have been investigated using scanning tunneling microscopy (STM) at 300 K. By the judicious choice of R in the CH2=CH-R molecule and by creating a dangling bond (DB) at a desired point using the STM tip, the perpendicularly connected allyl mercaptan (ALM) and styrene lines have been fabricated on the Si(100)-(2 x 1)-H surface. The continuous growth of the styrene line at the end DB of a growing ALM line (or vice versa) does not occur, perhaps, due to steric hindrance or/and interaction between adsorbed molecules.     

Complex-radical terpolymerization of phenanthrene,maleic anhydride,and trans-stilbene

The radical terpolymerization of the donor-acceptor-donor monomer system, phenanthrene (P)—maleic anhydride (M)—trans-stilbene (S), was studied. These monomers are known to be nonhomopolymerizable. The terpolymerization was carried out in p-dioxane and/or toluene at 70°C in the presence of benzoyl peroxide used as the initiator. P and S were found to form charge transfer complexes (CTC) with M in p-dioxane at 35°C. The results obtained are discussed in terms of the free monomer and complex propagation models. It is shown that terpolymerization is carried out at a stage close to binary copolymerization of two complexomers. The reactivity ratio of P … M and S … M complexes was estimated by the Kelen-Tüdös method. Absorbance ratios at 1770 cm^?1 (v_C=0 of anhydride group), 764 cm^?1 (δ_CH in monosubstituted benzene of S), and 820 cm^?1 (δ_CH in disubstituted benzene of P) as a function of terpolymer composition were established. P—M—S terpolymers are shown to have high thermal stabilities. © 1995 John Wiley & Sons, Inc.     

Selective chain reaction of acetone leading to the successive growth of mutually perpendicular molecular lines on the si(100)-(2 x 1)-H surface

The successive growth of mutually perpendicular molecular lines from one dangling-bond (DB) site on the Si(100)-(2 x 1)-H surface has been realized through a substrate-mediated chain reaction at 300 K. Among various molecules, acetone molecules undergo the most facile chain reaction with a DB site, which proceeds selectively on the Si(100)-(2 x 1)-H surface, resulting in only single molecular lines in the parallel-row (parallel to the dimer row) direction. The smaller size and higher reactivity of acetone molecules enable us to successively grow a parallel-row acetone line from the end of a cross-row (perpendicular to the dimer row) allylmercaptan line simply by changing the feed of gas molecules into the reaction chamber. Since the length of a molecular line is controlled by the number of gas molecules impinged, it is possible to turn a chain reaction from the cross-row direction to the parallel-row direction at any desired point on the surface. The reaction path of the adsorbing molecules is discussed. The present study provides a new means of fabricating mutually perpendicular molecular lines through a chain reaction initiating at a preselected DB site on the Si(100)-(2 x 1) surface.     

Density Functional Theory Approach to the Vibrational Properties and Magnetic Specific Heat of the Covalent Chain Antiferromagnet KFeS2

Ternary potassium-iron sulfide, KFeS₂, belongs to the family of highly anisotropic quasi-one-dimensional antiferromagnets with unusual “anti-Curie–Weiss” susceptibility, quasi-linearly growing with a rising temperature up to 700 K, an almost vanishing magnetic contribution to the specific heat, drastically reduced magnetic moment, etc. While some of the measurements can be satisfactorily described, the deficiency of the entropy changes upon the magnetic transition and the spin state of the iron ion remains a challenge for the further understanding of magnetism. In this work, high-quality single-crystalline samples of KFeS₂ were grown by the Bridgman method, and their stoichiometry, crystal structure, and absence of alien magnetic phases were checked, utilizing wave-length dispersive X-ray electron-probe microanalysis, powder X-ray diffraction, and ⁵⁷Fe Mössbauer spectroscopy, respectively. An ab initio approach was developed to calculate the thermodynamic properties of KFeS₂. The element-specific phonon modes and their density of states (PDOS) were calculated applying the density functional theory in the DFT + U version, which explicitly takes into account the on-site Coulomb repulsion U of electrons and their exchange interaction J. The necessary calibration of the frequency scale was carried out by comparison with the experimental iron PDOS derived from the inelastic nuclear scattering experiment. The infrared absorption measurements confirmed the presence of two high-frequency peaks consistent with the calculated PDOS. The calibrated PDOS allowed the calculation of the lattice contribution to the specific heat of KFeS₂ by direct summation over the phonon modes without approximations and adjustable parameters. The temperature-dependent magnetic specific heat evaluated by subtraction of the calculated phonon contribution from the experimental specific heat provides a lower boundary for estimating the reduced spin state of the iron ion.     

A review on TiO2 nanotubes: synthesis strategies,modifications, and applications

Journal of Solid State Electrochemistry - In the field of nanotechnology, titanium dioxide nanotubes (TiO2 NTs) are one of the most valued inventions. They were discovered in 1996, and have since...     

A novel dual surface modification on titanium in dental use: Characterization and topography

This laboratory study aimed to compare, contrast, and evaluate the effect of a novel dual surface modification method on the adhesion strength of resin composite cement to titanium. C.p.-2 grade titanium samples were silica-coated, etched with HNO₃(69vol %) or a blend of HCl (35vol %) and H₃PO₄ (85vol %), for 1 h at 80°C. Surface roughness was measured by surface roughness profilometry, topographic analysis by scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface analyses by energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS). Silanization of all specimens was carried out after SEM, EDX, and AFM analysis, before enclosed mold microshear bond strength testing (EM-μSBS). Adhesion strengths were measured after artificial ageing: 1 day, 1 week, 4 weeks, and 8 weeks by EM-μSBS testing and failure mode analysis by optical microscopy. Polished titanium was used as a control. The highest surface roughness was observed in titanium samples treated with silica-coating + HCl-H₃PO₄ etching. The elemental composition confirmed the presence of Ti, O, C, with Si and Al in samples treated with silica-coating. A gradual decrease in EM-μSBS values was observed in all titanium samples with adhesive and cohesive failure modes. The novel dual surface modification method applied in this study suggests that silica-coating + HCl-H₃PO₄etching strongly affects titanium surface topography and roughness. The presence of Si on silica-coated surface modified titanium before silanization with an experimental silane has a positive effect on the EM-μSBS of titanium samples treated with silica-coating only or silica-coating + HNO₃ etching.     

Syntheses,characterizations, crystal structures,DFT/TD-DFT,luminescence behaviors and cytotoxic effect of bicompartmental Zn (II)-dicyanamide Schiff base coordination polymers: An approach to apoptosis,autophagy and necrosis type classical cell death

Two new Zn (II)-dicyanamide (dca) 1-D chain coordination polymers (CPs), [Zn (L^OMe)(μ₁-dca)(μ_1,5-dca)]_n (1) and [Zn (L^OEt)(μ₁-dca)(μ_1,5-dca)]_n (2) have been successfully synthesized from bicompartmental Schiff base ligands N,N^′-Bis(3-methoxysalicylidenimino)-1,3-diaminopropane (H₂L^OMe), N,N^′-Bis(3-ethoxysalicylidenimino)-1,3-diaminoproane (H₂L^OEt) respectively and structurally characterized using various spectroscopic protocols like ¹H NMR, IR, Raman, UV–Vis, fluorescence as well as elemental analysis, TGA, PXRD and SCXRD studies. X-ray single crystal study revealed that both the complexes have two different geometrical arrangement of Zn metal centres with distorted square pyramidal Zn(2) and trigonal prismatic geometry Zn(1). Ab-initio DFT (Density functional theory) has been executed at B3LYP (Becke, 3-parameter, Lee-Yang-Parr) using DGDVP (Diffuse gradient double valence polarised) basis set to explain FMO (Frontier molecular orbital), TD-DFT (Time-dependent density functional theory) and photovoltaic efficiency in Dye Sensitized Solar Cell (DSSC). Hirshfeld surface (HS) and 2D fingerprint plot analyses are shed more light on the non-covalent supramolecular interactions. The steady state and time-resolved fluorescence measurements have been conducted in DMSO and solid-state. CPs exhibited bi-exponential decay in DMSO as well as solid-state where fluorescence behaviors are mainly intra-ligand (π → π^*) in nature with lifetimes in the range (1.11–1.06 ns). In particular, in vitro cytotoxic activities were evaluated towards MCF7 (breast cancer) cell line, MDA-MB-231 (breast carcinoma) cell line and MCF10A (breast epithelial) cell line using MTT assay. CP 1 had lower cytotoxic effect against MCF7 (20 μM), MDA-MB-231 (15 μM) cell lines in comparison with cisplatin (42.2 ± 8, 128.2 ± 7 μM). CP 1 induced classical cell death apoptosis, autophagy and necrosis. Lower IC₅₀ value of CP 1 against MDA-MB-231 cell line provide new insights in the development of cancer therapeutics.