Narrow Results

Transition metal elements and others in river water sample supplied by The Japan Society for Analytical Chemistry (JSAC) were determined by PIXE using 2.5 MeV proton beam at the Tokyo Institute of Technology Van de Graaff Laboratory. The relative detection efficiency for each X-ray of element and its recovery were studied in two methods: "Drop and Dry" and "Concentration" methods. Ten elements (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se and Pb) were determined, being in good agreement with the values certified by JSAC except for Mn. Intensity of K_α X-ray of As and L_α, X-ray of Pb nearly close to each other could be successfully evaluated using isolated L_β X-ray of Pb. Mn was insufficiently recovered to give lower content than the certified value in the present conditions. V that is not listed in the certificate was found to show good agreement with that reported previously. Concentration method using sodium dibenzyldithiocarbamate only could be successfully employed for collecting these elements.

Pyrazinamide (PZA) is among the first-line drugs for the treatment of tuberculosis, which seems to reappear as a frequent disease. In this study we investigate the structural changes induced in these samples as evidenced by thermal behaviour and electron spin resonance of new transition metal complexes of PZA. We is search for a correlation between structure and thermal transformations described as multi-step processes consisting in crystalline phase transition, decomposition, melting and thermo-oxidation.

Glass stability and the structural role of iron oxide in xFe₂O₃(100-x)[B₂O₃–MO] systems (M=Ca, Sr or Ba, 0≤x≤30 mol%) were estimated from differential thermal analysis. The results suggest structural changes characteristic for the transition from short range to intermediate range order as the cationic field strength of the alkaline earths increases. In contrast, the iron addition has an opposite effect and determines a higher glass stability of these systems.

We have calculated the electrical resistivity of amorphous transition metals Fe and Ni by using the Diffraction model as proposed by Ziman. The electron–ion interaction is described by a local model pseudopotential, and the static structure factors are taken from the experiment. The d-band effect, a characteristic of the transition metals, is accounted for through the sp–d hybridization effect. Agreement of the calculated results with the available experimental data is found to be remarkably good for both systems.

Combining the modified analytic embedded atom method (MAEAM) with lattice dynamics theory, the phonon dispersion along five symmetry directions have been calculated for three transition metals V, Nb and Ta. A good agreement between calculations and experiments along three high symmetry directions [q00], [qqq] and [qq0] implies that the predicted phonon dispersion along the other two directions [1qq] and are well behaved. Along each direction, the phonon frequency decreases for V, Nb and Ta successively may be related to the ratio of the cohesive energy to atomic mass.

A modified generalized Morse (mGM) equation of state (EOS) is proposed that can incorporate the cohesive energy data correctly. It is compared with a four-parameter modified Rose EOS (MR EOS) which is proposed by following the Rose's approach and the Vinet EOS. The MR, mGM and Vinet EOSs are applied to five transition metals to fit all experimental compression data available. The results show that for all pressure ranges the mGM EOS gives the best fitting results. From the comparison of variation of pressure and energy versus compression ratio between MR and mGM EOS, it is clear that the pressure and energy of the MR EOS oscillate both in the neighborhood of (V/V₀) ≈ 0.005 and in the range (V/V₀) > 1. Such oscillations are physically incorrect, and the tendency of the mGM EOS are physically correct both in the neighborhood of (V/V₀) ≈ 0.005 and in the range (V/V₀) > 1. Generally speaking, the mGM EOS has evident advantage among the three EOSs, and the MR EOS's practical applications are seriously limited because of the physically incorrect oscillations.

First-principles calculations on the incompressibility, elasticity and hardness of the Os, OsB₂, Re, and ReB₂ materials have systematically been performed by the plane-wave basis pseudopotential method. Transition metals Os and Re, which have high bulk modulus but low hardness, can be converted into hard materials by combining them with small B atoms. Moreover, electronic and structural mechanisms of ReB₂ and OsB₂ are analyzed in detail and compared. It is shown that incorporating small B atoms into heavy transition metals should be a valid pathway to obtain new superhard materials.

Electronic structures and optical properties of zinc-blende aluminum nitride doped with transition metals are investigated. Lu-doped system possesses the most considerate stability with the lowest formation energy of −9.033 eV compared to others. Band structures of systems are introduced to investigate a more excellent semiconductor capacity for Re-doped system with a band gap $(E_G)$ of 0.689 eV, with others having band gaps of 2.120, 2.159, 1.806, 1.837 and 0.879 eV, respectively, much smaller than that of pristine one, 3.113 eV. Moreover, absorption spectra curve reaches the lowest peak of $2.558\times 10^5{\mathrm{\text{cm}}}^{-1}$ for Os-doped system; simultaneously, the system exhibits a relatively negative reflectivity spectra and dielectric loss of 5.620 eV that are extensively expected in solar cell industry, predicting its broad scope of application prospects in photoelectric and microelectronic devices.

Macrocyclic compounds have got recognition in modern science and technologies because of their potential applications in energy, catalysis, material science, biochemistry, and pharmaceutical. The most interesting feature of macrocyclic complexes is their adjustable macrocyclic cavity which opens many possibilities for the development of various important fields. Herein, we synthesized two MN₄-macrocyclic complexes (M = Fe(III) and Ni(II) by using template method, and characterized by employing multiple techniques like molar conductance, FTIR, UV–Vis and mass spectra. On the basis of characterization results, a saddle shaped octahedral geometry can be attributed to theses complexes. The “saddle shape” geometry of these complexes is due to the steric repulsions between the benzenoid and amidic moieties on the macrocyclic framework as suggested by theoretical investigations. Further, the electrochemical investigations carried out using cyclic voltammetry in methanol at the Pt electrode indicated that the unusual oxidation state of metal ion could stabilize the macrocyclic framework of the complex. Moreover, these complexes were also evaluated for their antibacterial activities against several pathogens using Gentamycin as standard drug. The results suggested that these complexes did have significant antimicrobial activity.

This study reports the third-order nonlinear optical (NLO) properties of hexamethylenetetramine (HMTA) stabilized pure and transition metals (Cu, Co and Mn) doped ZnS nanoparticles (NPs) and their electronic structures. The third-order NLO properties of pure and transition metals (Cu, Co and Mn) doped ZnS NPs were measured by $Z$-scan technique. From these measurements, the pure and doped ZnS samples exhibit negative nonlinearity i.e., self-defocusing. The open aperture $Z$-scan measurement shows saturated absorption within the medium. The prepared pure and doped ZnS samples exhibit nonlinear refractive index of the order of 10${}^{-8}$(cm²/W), nonlinear absorption (NLA) coefficient of the order of 10${}^{-4}$cm/W and nonlinear optical susceptibility of the order of 10${}^{-6}$esu. The electronic structures of these ZnS NPs were investigated using near edge X-ray absorption fine structure (NEXAFS) measurements at the C K-, N K- and Co L${}_{3,2}$-edges. The C K- and N K-edges XANES spectra reveal the appearance of several spectral features in the range 285–290eV and 390–430eV respectively. The Co L${}_{3,2}$-edge NEXAFS spectrum exhibits multiplet absorption lines similar to those of Co${}^{2+}$ ions coordinated in tetrahedral symmetry with four sulfur nearest neighbors. These results clearly demonstrate that divalent Co ions substitute Zn sites. From the Raman spectra, the appearance of multiple resonance Raman peaks indicates that the prepared ZnS samples have good optical quality.

The unique geometry of carbon nanotubes offers an ideal template for designing one-dimensional metal/nanotube hybrid structures. Through ab initio calculations we found that transition-metal/nanotube hybrid structures exhibit very interesting physical properties. The hybrid structures can have drastically different conduction properties from those of the pristine tubes and considerable magnetic moments. In some instances perfect spin polarization is achieved. The results point to a new and promising approach that uses such hybrid structures as devices for spin-polarized transport, which is expected to provide immense applications in the emerging field of spintronics.

The reaction under autogenic pressure at elevated temperature (RAPET) technique is proposed for synthesizing a series of metal phosphide nanoparticles such as MoP, MoP₂, Cu₃P and CuP₂ at 850${}^{\circ }$C for 3.50h by reacting selectively the transition metal powders with elemental phosphorus. The obtained products are characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). A reaction mechanism is suggested based on the experimental results.

This paper demonstrates the functionality of a simple and convenient microfluidic method in synthesizing a series of poly(vinylpyrrolidone) (PVP) stabilized nanoparticles (NPs) of various novel metals (Pt, Pd, Ru, Rh, Ag, and Au) with an average diameter of $<$2 nm. In this method, the use of microfluidic mixture provided a homogenous mixing of the metal precursors and reducing agent nearly at the molecular level, that yield monodispersed sub-nanosize NPs. Core diameters of the produced NPs determined by transmission electron microscopy (TEM), were $1.3\pm 0.3$, $1.6\pm 0.3$, $1.3\pm 0.2$, $1.7\pm 0.4$, $1.9\pm 0.4$ and $1.2\pm 0.2$nm for Pt, Pd, Ru, Rh, Ag and Au NPs, respectively. Of them, Pt NPs were detailed characterized. The obtained Pt NPs were found to have fcc crystal structure with 1.2 nm crystalline size which is very similar to the corresponding TEM result. The efficiency of the synthesis of NPs by micromixer was compared with batch/NaBH₄ reduction method for the Pt NPs. It was found that in batch method the as-prepared NPs decreased the reducing ability of NaBH₄ by catalytic degradation. In contrast, the micromixer could separate the produced metal NPs from the reaction system soon after the formation of NPs and enables feeding the fresh NaBH₄ solution throughout the synthesis. Fourier Transform Infrared (FTIR) spectrometry measurements of adsorbed ${}^{12}$CO molecules on Pt NPs showed that the NPs surface were negatively charged with a high population of edge and vertices atoms.

Photophysical properties of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMpyP4) and its metallocomplexes M(II)TMpyP4 (M = Zn, Cu, Ni, Co) bound to natural DNA and synthetic poly-, oligo- and mononucleotides are considered with a primary emphasis placed upon intermolecular interaction of the photoexcited porphyrins with the nearest environment. Quenching of the fluorescent S₁ (but not triplet T₁) state due to guanine to porphyrin electron transfer is observed for TMpyP4 intercalated between GC base pairs of the double-strand helixes, whereas in the case of TMpyP4 complexed with guanosine monophosphate (GMP) both S₁ and T₁ states of the porphyrin are quenched. Furthermore, a dependence of the efficiency of TMpyP4 triplet state quenching by the dissolved molecular oxygen from air on the porphyrin localization enables one to readily distinguish porphyrin groove binding mode from intercalation. Excited states of the TMpyP4 complexes with transition metals, in spite of their very short lifetimes, also interact with nucleic acid components by means of an axial ligand binding/release to/from the metal. A possible structure of the five-coordinate excited complex (“exciplex”) formed in case of CuTMpyP4 groove binding to some single- and double-strand polynucleotides is discussed.

New phthalonitrile (L1), metal-free phthalocyanine (H₂Pc) and zinc-phthalocyanine (ZnPc) substituted in peripheral positions with 2-pyridyl methyl pendant arm linked mixed donor macrocyclic ligands have been prepared in a multi-step reaction sequence. The novel compounds were characterized by a combination of elemental anlaysis, ¹H NMR, ¹³C NMR, IR, UV-vis and MS spectral data. The influence of metal cations such as Cd²⁺, Zn²⁺, Hg²⁺, Al³⁺, Fe³⁺ and Cu²⁺ on the spectroscopic properties of dinitrile compound L1 and free phthalocyanine H₂Pc was investigated by means of absorption spectrophotometry. Spectrophotometric titrations were carried out with these ligands for Cu²⁺ ion. The complex composition of Cu-L1 was found 1:1 by means of spectrophotometric titration data. The spectrophotometric method showed good sensitivity for Cu²⁺ with linear range of 2.6 × 10^-6 to 1.3 × 10^-4 M with dinitrile compound.

Naturally-derived metallo-bacteriochlorophylls have attracted much attention since their clinical approval for cancer photodynamic therapy. Their therapeutic properties are rooted in the metal complexation of bacteriochlorophylls, which endows them with optical properties favourable for biophotonic and biomedical applications, including near-infrared light-activated reactive oxygen species generation at therapeutic levels. Despite these advantages, the utility of these chromophores has been limited by synthetic challenges associated with bacteriochlorophyll metallation; specifically, a slow reaction rate and necessity of complex purification procedures remain barriers towards metalated bacteriochlorophyll synthesis. Here, these limitations are overcome through the development of a new fast, facile, efficient, base-free microwave heating metallation method for the synthesis of a series of metallo (Pd, Cu, Zn, Cd, Sn, In, Mn, Co) bacteriopyropheophorbides. The preparation and structural and optical spectral characterization of these complexes are presented. This microwave-enabled synthetic method is then applied to generate the clinical photosensitizer agent Pd-bacteriopheophorbide (TOOKAD) effectively and efficiently, followed by validation of its metallation-enhanced ROS generation.

In this research paper, the effect of the material of electrodes at the nanometer scale was elucidated towards measuring the electron transport properties of a single molecular junction comprising of anthracenedithiol molecule (ADT) stringed to two semi-infinite metallic electrodes using Extended Huckle Theory (EHT)-based semi-empirical modelling approach. The electron transport parameters i.e., I–V curves, Conductance-Voltage curves and transmission spectrum were investigated through ADT molecule by buffering it between different electrodes composed of rhodium, palladium, nickel and copper, all from transition metals series, under finite bias voltages within Keldysh's non equilibrium green function formulism (NEGF). The simulated results revealed that the copper electrodes showed maximum conduction whereas palladium showed least. The maximum conductance of 0.82 G₀ and 43 μA current was exhibited by copper and thus affirmed to be the most effective electrode at nanometre scale when compared with other electrodes viz. nickel, rhodium and palladium.

Water electrolysis is one of the most feasible ways to utilize clean and renewable energy sources in the form of hydrogen energy. However, the anodic oxygen evolution reaction (OER) is a slow kinetic process, so it is of great significance to develop efficient oxygen evolution catalysts (OECs). Many studies have shown that Ce plays an important role in high-performance transition-metal-based OECs. We discuss and summarize possible causes for the improved OER activity and stability with emphasis on the hybrids of cerium and transition metals, including cerium-doped catalysts, ceria-support catalysts and ceria-loaded catalysts. Finally, current challenges for the Ce-containing catalysts are identified, pointing to the future directions for propelling the water electrolysis research.

Due to their distinct structural, electrical, and electrochemical properties, macrocyclic complexes have been recognized as potential models in a variety of areas, including electrocatalysis, biology, and medicine. In this study, two hexa-aza-macrocyclic complexes of Ni(II) and Cu(II) transition metals (denoted as [NiL] and [CuL]) were synthesized via template procedure. Based on the results of multiple spectroscopic characterization, a distorted octahedral geometry was proposed for both the complexes. The electrochemical results showed that the macrocyclic framework can stabilize the unusual oxidation states of Ni(II) and Cu(II) transition metal ions, as evidenced by the corresponding quasi-reversible Ni(II)/(III) and Cu(II)/(III) redox couples. Additionally, both the complexes were found to be promising antibacterial agents against the B. subtilis, S. aureus, P. aeruginosa, and E. coli pathogens. The Cu(II) complex had the largest inhibition zone (22mm) against B. subtilis, while the Ni(II) complex had the smallest (15mm).

Many interesting properties of polyoxometalates (POMs) are related to their ability to reversibly accept and release electrons. The correct computational description of metal electrons in POMs is central to fully understand the implications and mechanisms related to reduced structures. We performed DFT calculations on fully oxidized [P₂W₁₈O₆₂]^6- and α₁/α₂-[P₂MW₁₇O₆₂]^n-(M = V, Mo) anions, and their one-electron reduced partners. Atomic spin populations of the reduced forms reveal that pure GGA functionals, which overdelocalize the electron density by nature, cannot correctly describe the extra electron especially when competition between the localized and delocalized situations is very close in energy, namely for α₂-[P₂MoW₁₇O₆₂]^7-. On the other hand, hybrid functionals like B3LYP or M05 can localize the electron at the correct site. Within these "well-behaved" density functionals, only the B3LYP gives the correct ordering and relative reduction energies (REs) with respect to electrochemical measurements, although the absolute values are always less exothermic than expected. At present, this is the best density functional for computing redox properties of POMs.