Charged Bi Research Articles

In-situ Bi-modified Pt towards glycerol and formic acid electro-oxidation: Effects of catalyst structure and surface microenvironment on activity and selectivity

The performances of glycerol electro-oxidation reaction (GOR) and formic acid electro-oxidation reaction (FAOR) catalyzed by Pt catalyst were dramatically improved by adding Bi3+ into the reaction solution. The dynamic structure and microenvironment of in-situ Bi-modified Pt and their impact on the catalytic performances were revealed. A strong correlation was established between the Bi coverage of Pt-based catalysts and their resistance to CO poisoning and performance in GOR and FAOR. When Bi3+ increased to a certain amount, a Bi-shell containing hydroxides was formed on Pt surfaces except the formation of Pt-Bi ensemble. On Pt catalyst covered with 43.9 % Bi, the peak mass-specific activities of GOR and FAOR in forward scans were 4.2 and 34.7 times that of Pt/NCNTs, respectively. The peak electrochemical active surface area (ECSA)-specific activity of FAOR in forward scan for Pt with 52.6 % Bi coverage was 80.6 times that of Pt/NCNTs. The dehydrogenation process in FAOR and the 4-electron pathway in GOR were improved for Bi-modified Pt. The experimental results and DFT calculations indicated that the positively charged Bi and structure of Pt-Bi ensemble improved the adsorption and interaction of negatively charged intermediates, and the enhanced hydroxides facilitated the oxidation and removal of toxic intermediates, such as CO.

Ion-photon emission under bombardment of Ta target with cluster and multiply charged Bi ions

In this work the yield of ion-photon emission (IPE) was measured under bombardment of Ta target with cluster and multiply-charged projectiles in the energy range of 2–12 keV. The study was carried out on a unique experimental setup created for studying the interaction of cluster and multiply-charged ions with a solid, which was modernized and supplemented with a system for measuring IPE. Primary cluster ions Bim+ (m = 1–4) and multiply charged Biq + ions (q = 1–6) were obtained using the source that was developed. An increase in the integral yield of IPE was observed with an increase in the number of atoms in the bombarding cluster ions and their energy. The yield of IPE during the bombardment of Ta targets with multiply charged Biq + ions (q = 1–6) was shown the IPE yield weakly depends on the multiply charge at q < 4 and increases as the charge increases from 3 to 6.

Electro‐Oxidation of Polyols on Bi‐Modified Pt in Acidic Media (HClO4). Understanding Activity and Selectivity Trends

AbstractHerein we show that Pt(111) and Pt(100) can produce the ketone through the oxidation of the secondary carbon of the polyols. After the Bi modification, the selectivity for the ketone formation increases. On the other hand, we observe that pure and Bi‐modified Pt(110) only produced the C3 molecules oxidized in the primary carbon, and it is the only facet that shows an enhancement in the activity due to the modification. In line with these findings, small Pt nanoparticles are not selective for ketone formation. Finally, based on data obtained through DFT calculations, we suggest that positively charged Bi adatoms interact with the OH‐ groups of the enediol‐like intermediate (believed to be the precursor for the ketone/aldehyde production), facilitating the oxidation of the secondary carbon to produce DHA.

The First Naked Bismuth-Chalcogen Metal Carbonyl Clusters: Extraordinary Nucleophilicity of the Bi Atom and Semiconducting Characteristics.

Mixed bismuth-chalcogen-iron clusters [{EFe3(CO)9}Bi]- [E = Te (1a) or Se (1b)] were produced via the reduction of BiCl3 with [EFe3(CO)9]2- under mild conditions. X-ray analysis showed that both clusters 1a and 1b had a square-pyramidal geometry, where the naked Bi and chalcogen both adopted a distorted trigonal-pyramidal configuration with a stereoactive lone pair. Complexes 1a and 1b can be further functionalized by methylation and metalation, which permits the nucleophilicity of the 6s/5s and 6s/4s lone pairs to be compared. In the metalation, the 6s pair of the Bi atom in 1a and 1b had an extraordinary nucleophilicity toward the unsaturated Cr(CO)5 fragment, even in the presence of the more chemically active 5s or 4s pair, whereas in the case of methylation, only the 4s pair of Se could be selectively alkylated. Upon oxidation of 1a and 1b with suitable oxidizing agents, NaBiO3 or K2SeO3, Bi-E bonded tetrahedral complexes [{EFe2(CO)6}Bi]- [E = Te (4a) or Se (4b)] were formed by the elimination of one Fe(CO)3 vertex. X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and density functional theory (DFT) calculations showed that all of the Bi atoms in these complexes had oxidation states close to +1. Due to the electropositive character of the Bi atom, pronounced induced Bi···E inter- and intramolecular interactions were evident in 1a (1b), 4a (4b), and the metalated 3a (3b), where their linear-like ···Bi···E··· or zigzag-like ···Bi-E··· (E = Te or Se) chain or the Bi···E···E···Bi (E = Te or Se) dimeric chain can further expand into the two-dimensional network via nonclassical C-H···O(carbonyl) interactions, supported by noncovalent interaction index and DFT calculations. These positively charged Bi-induced Bi···E (E = Te or Se) and carbonyl-aided weak interactions can facilitate efficient electron transport within these ternary Bi-E-Fe or quaternary Bi-E-Fe-Cr cluster-based frameworks, resulting in semiconducting behavior with surprising ultranarrow energy gaps of 1.01-1.21 eV.

Fragmentation of Bi clusters by multiply charged ions

We report on collisions of multiply charged ions with free Bi nanoparticles in the gas phase. The nanoparticles contain up to 650 Bi atoms corresponding to a diameter of 3.5 nm. The stability limit of multiply charged Bi clusters has been investigated yielding appearance sizes for Bi clusters in charge states up to $q=6$, which are in good agreement with predictions of the liquid drop model. This finding underlines the metallic character of the Bi particles. By coincidence measurements the correlation between the dominant fragments ${\mathrm{Bi}}^{+}$ and ${{\mathrm{Bi}}_{3}}^{+}$ and larger multiply charged residues has been determined. The comparison of the kinetic energies with $Q$-value calculations within the liquid drop model allowed identifying specific decay processes as two-body asymmetric fission or multifragmentation events. The higher kinetic energies of singly charged monomer ions compared to that of trimer ions are explained by a higher fissility of the decaying system. Correlation islands for small fragments indicate different decay mechanisms based on two-step processes where a third undetected fragment can be emitted in the first or the second step.

From Complex Inorganic Oxides to Ag-Bi Nanoalloy: Synthesis by Femtosecond Laser Irradiation.

Bimetallic nanoalloys with a wide variety of structures and compositions have been fabricated through many diverse techniques. Generally, various steps and chemicals are involved in their fabrication. In this study, the synthesis of Ag–Bi nanoalloys by femtosecond laser irradiation of an inorganic oxide Ag2WO4/NaBiO3 target without any chemicals like reducing agents or solvent is presented. The interaction between these materials and the ultrashort pulse of light allows the migration of Ag and Bi atoms from the crystal lattice to the particles surfaces and then to the plasma plume, where the reduction of the positively charged Ag and Bi species in their respective metallic species takes place. Subsequently, the controlled nucleation and growth of the Ag–Bi alloyed nanoparticles occurs in situ during the irradiation process in air. Although at the bulk level, these elements are highly immiscible, it was experimentally demonstrated that at nanoscale, the Ag–Bi nanoalloy can assume a randomly mixed structure with up to 6 ± 1 atom % of Bi solubilized into the face-centered cubic structure of Ag. Furthermore, the Ag–Bi binary system possesses high antibacterial activity against Staphylococcus aureus (methicillin-resistant and methicilin-susceptible), which is interesting for potential antimicrobial applications, consequently increasing their range of applicability. The present results provide potential insights into the structures formed by the Ag–Bi systems at the nanoscale and reveal a new processing method where complex inorganic oxides can be used as precursors for the controlled synthesis of alloyed bimetallic nanoparticles.

Room temperature transparent conducting magnetic oxide (TCMO) properties in heavy ion doped oxide semiconductor

Bismuth doped ZnO (ZnBi0.03O0.97) thin films are grown using pulsed laser deposition. The existence of positively charged Bi, absence of metallic zinc and the Zn-O bond formation in Bi doped ZnO are confirmed using X-ray Photoelectron Spectroscopy (XPS). Temperature dependent resistivity and UV-visible absorption spectra show lowest resistivity with 8.44 × 10-4 Ω cm at 300 K and average transmittance of 93 % in the visible region respectively. The robust ferromagnetic signature is observed at 350 K (7.156 × 10-4 emu/g). This study suggests that Bi doped ZnO films should be a potential candidate for spin based optoelectronic applications.

Sources for beyond extreme ultraviolet lithography and water window imaging

Lithography tools are being built and shipped to semiconductor manufacturers for high volume manufacturing using extreme ultraviolet lithography (EUVL) at a wavelength of 13.5 nm. This wavelength is based on the availability of Mo/Si multilayer mirrors (MLMs) with a reflectivity of ∼70% at this wavelength. Moreover, the primary lithography tool manufacturer, ASML, has identified 6.x nm, where x∼7, as the wavelength of choice for so-called Beyond EUVL, based on the availability of La/B4C MLMs, with theoretical reflectance approaching 80% at this wavelength. The optimum sources have been identified as laser produced plasmas of Gd and Tb, as n = 4–n = 4 transitions in their ions emit strongly near this wavelength. However, to date, the highest conversion efficiency obtained, for laser to EUV energy emitted within the 0.6% wavelength bandwidth of the mirror is only 0.8%, pointing to the need to identify other potential sources or consider the selection of other wavelengths. At the same time, sources for other applications are being developed. Conventional sources for soft x-ray microscopy use H-like line emission from liquid nitrogen or carbon containing liquid jets which can be focused using zone plates. Recently the possibility of using MLMs with n = 4−n = 4 emission from a highly charged Bi plasma was proposed and subsequently the possibility of using Δn = 1 transitions in 3rd row transition elements was identified. All of these studies seek to identify spectral features that coincide with the reflectance characteristics of available MLMs, determine the conditions under which they are optimized and establish the maximum conversion efficiencies obtainable. Thus, there is a need for systematic studies of laser produced plasmas of a wide range of elements as some of the challenges are similar for all of these sources and some recent results will be presented.

Spectroscopic study of bismuth ions with an electron beam ion trap

We present the electron beam energy dependence of the emission spectra of multiply charged Bi ions measured with an electron beam ion trap in the wavelength range of the water window. Experimental results are compared to the theoretical ones calculated with the flexible atomic code.

Adsorption of thiourea on Bi(1 1 1) electrode surface

The impedance spectroscopy and in situ STM methods have been used for investigation of the thiourea (TU) adsorption at the electrochemically polished Bi(111) electrode from weakly acidified (pH≈5) Na2SO4 supporting electrolyte solution. Influence of the Bi(111) electrode potential and TU concentration on the adsorption kinetics of thiourea has been demonstrated. In the region of maximum adsorption, E>−0.85V (Ag|AgCl in saturated KCl), the heterogeneous adsorption and diffusion steps are the rate determining stages for TU adsorption. It was found that for more concentrated TU solutions|Bi(111) interface (cTU⩾1.0M), the stable TU adlayer is detectable by the in situ STM method only at the weakly negatively and positively charged Bi(111) electrode surface. At lower TU concentrations the adsorbed TU molecules are mobile and cannot be visualized using in situ STM method. At moderately negatively charged Bi(111) electrode surface, there are no chemisorbed TU molecules detectable by in situ STM method. The in situ STM data are in a good agreement with the impedance data indicating that the weak slow chemisorption with the partial charge transfer step takes place at E>−0.85V.

Mechanisms of boron diffusion in silicon and germanium

B migration in Si and Ge matrices raised a vast attention because of its influence on the production of confined, highly p-doped regions, as required by the miniaturization trend. In this scenario, the diffusion of B atoms can take place under severe conditions, often concomitant, such as very large concentration gradients, non-equilibrium point defect density, amorphous-crystalline transition, extrinsic doping level, co-doping, B clusters formation and dissolution, ultra-short high-temperature annealing. In this paper, we review a large amount of experimental work and present our current understanding of the B diffusion mechanism, disentangling concomitant effects and describing the underlying physics. Whatever the matrix, B migration in amorphous (α-) or crystalline (c-) Si, or c-Ge is revealed to be an indirect process, activated by point defects of the hosting medium. In α-Si in the 450-650 °C range, B diffusivity is 5 orders of magnitude higher than in c-Si, with a transient longer than the typical amorphous relaxation time. A quick B precipitation is also evidenced for concentrations larger than 2 × 1020 B/cm3. B migration in α-Si occurs with the creation of a metastable mobile B, jumping between adjacent sites, stimulated by dangling bonds of α-Si whose density is enhanced by B itself (larger B density causes higher B diffusivity). Similar activation energies for migration of B atoms (3.0 eV) and of dangling bonds (2.6 eV) have been extracted. In c-Si, B diffusion is largely affected by the Fermi level position, occurring through the interaction between the negatively charged substitutional B and a self-interstitial (I) in the neutral or doubly positively charged state, if under intrinsic or extrinsic (p-type doping) conditions, respectively. After charge exchanges, the migrating, uncharged BI pair is formed. Under high n-type doping conditions, B diffusion occurs also through the negatively charged BI pair, even if the migration is depressed by Coulomb pairing with n-type dopants. The interplay between B clustering and migration is also modeled, since B diffusion is greatly affected by precipitation. Small (below 1 nm) and relatively large (5-10 nm in size) BI clusters have been identified with different energy barriers for thermal dissolution (3.6 or 4.8 eV, respectively). In c-Ge, B motion is by far less evident than in c-Si, even if the migration mechanism is revealed to be similarly assisted by Is. If Is density is increased well above the equilibrium (as during ion irradiation), B diffusion occurs up to quite large extents and also at relatively low temperatures, disclosing the underlying mechanism. The lower B diffusivity and the larger activation barrier (4.65 eV, rather than 3.45 eV in c-Si) can be explained by the intrinsic shortage of Is in Ge and by their large formation energy. B diffusion can be strongly enhanced with a proper point defect engineering, as achieved with embedded GeO2 nanoclusters, causing at 650 °C a large Is supersaturation. These aspects of B diffusion are presented and discussed, modeling the key role of point defects in the two different matrices.

Ultra-broad near-infrared photoluminescence from crystalline (K-crypt)2Bi2 containing [Bi2]2− dimers

For the first time, we report that a single crystal of (K-crypt)2Bi2 containing [Bi2]2+ displays ultra-broad near-infrared photoluminescence (PL) peaking at around 1190 nm and having a full width at the half maximum of 212 nm, stemming from the inherent electronic transitions of [Bi2]2+.The results not only add to the number of charged Bi species with luminescence, but also deepen the understanding of Bi-related near-infrared emission behavior and lead to the reconsideration of the fundamentally important issue of Bi-related PL mechanisms in some material systems such as bulk glasses, fibers, and conventional optical crystals.

Production of highly charged ion beams with SECRAL

Superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL) is an all-superconducting-magnet electron cyclotron resonance ion source (ECRIS) for the production of intense highly charged ion beams to meet the requirements of the Heavy Ion Research Facility in Lanzhou (HIRFL). To further enhance the performance of SECRAL, an aluminum chamber has been installed inside a 1.5 mm thick Ta liner used for the reduction of x-ray irradiation at the high voltage insulator. With double-frequency (18+14.5 GHz) heating and at maximum total microwave power of 2.0 kW, SECRAL has successfully produced quite a few very highly charged Xe ion beams, such as 10 e microA of Xe(37+), 1 e microA of Xe(43+), and 0.16 e microA of Ne-like Xe(44+). To further explore the capability of the SECRAL in the production of highly charged heavy metal ion beams, a first test run on bismuth has been carried out recently. The main goal is to produce an intense Bi(31+) beam for HIRFL accelerator and to have a feel how well the SECRAL can do in the production of very highly charged Bi beams. During the test, though at microwave power less than 3 kW, more than 150 e microA of Bi(31+), 22 e microA of Bi(41+), and 1.5 e microA of Bi(50+) have been produced. All of these results have again demonstrated the great capability of the SECRAL source. This article will present the detailed results and brief discussions to the production of highly charged ion beams with SECRAL.

Theoretical analysis of radiation spectrum in highly charged Tm-like Bi XV

Using the fully relativistic multiconfiguration Dirac–Fock approach, we have calculated 2249 energy levels and radiative lifetimes, and various transition elements for the E1, M1, E2 and M2 transitions among the fine-structure energy levels belonging to the 4f145s25p65d, 5s25p6nl, 5s25p55d2, 5s25p55d5l, 5s5p6 5d2, 5s5p65d65d6l (n⩽8, l⩽4), etc, configurations of highly charged Tm-like ions Bi XV. The calculation results of this work are in good agreement with recent experimental data. We have found some longer lifetime metastable energy levels and self-excitation phenomena, and explained the physical mechanism of many-photon radiation and many-photon absorption. The calculation results provide more necessary atomic data for the research on XUV lasers.

Photoelectron imaging and theoretical investigation of bimetallic Bi1–2Ga–2− and Pb1–4− cluster anions

We present the results of photoelectron velocity-map imaging experiments for the photodetachment of small negatively charged Bi(m)Ga(n) (m=1-2, n=0-2), and Pb(n) (n=1-4) clusters at 527 nm. The photoelectron images reveal new features along with their angular distributions in the photoelectron spectra of these clusters. We report the vertical detachment energies of the observed multiple electronic bands and their respective anisotropy parameters for the Bi(m)Ga(n) and Pb(n) clusters derived from the photoelectron images. Experiments on the BiGa(n) clusters reveal that the electron affinity increases with the number of Ga atoms from n=0 to 2. The BiGa(2)(-) cluster is found to be stable, both because of its even electron number and the high electron affinity of BiGa(2). The measured photoelectron angular distributions of the Bi(m)Ga(n) and Pb(n) clusters are dependent on both the orbital symmetry and electron kinetic energies. Density-functional theory calculations employing the generalized gradient approximation for the exchange-correlation potential were performed on these clusters to determine their atomic and electronic structures. From the theoretical calculations, we find that the BiGa(2)(-), Bi(2)Ga(3)(-) and Bi(2)Ga(5)(-) (anionic), and BiGa(3), BiGa(5), Bi(2)Ga(4) and Bi(2)Ga(6) (neutral) clusters are unusually stable. The stability of the anionic and neutral Bi(2)Ga(n) clusters is attributed to an even-odd effect, with clusters having an even number of electrons presenting a larger gain in energy through the addition of a Ga atom to the preceding size compared to odd electron systems. The stability of the neutral BiGa(3) cluster is rationalized as being similar to BiAl(3), an all-metal aromatic cluster.

Size- and charge-dependent geometric and electronic structures of Bin (Bin−) clusters (n=2–13) by first-principles simulations

Neutral and negatively charged bismuth clusters, Bi n and Bi(-)n (n=2-13), are investigated by first-principles simulations with the scalar-relativistic projector-augmented wave potential and the spin-polarized generalized gradient approximation. Both types of clusters show size-dependent odd-even oscillations in stability, density of states, and vertical and adiabatic electron affinities, in close agreement with experiment. The negative charge thoroughly reverses the oscillations and considerably influences the geometric structures, particularly of the odd-sized clusters. We note that most atoms in the ground states and the low-lying isomers are three coordinated with a quasilayerlike growth mode based on pentagon units, due to a weak s-p hybridization. The Bi12 cluster is found to prefer a small elongated tubelike structure with the surface consists of six curved-pentagon rings and two triangular facets, which may be the basis for the formation of bismuth nanotubes experimentally reported.

Adsorption of camphor and 2,2′-bipyridine on Bi(1 1 1) electrode surface

Impedance spectroscopy and in situ STM methods have been used for investigation of the camphor and 2,2′-bipyridine (2,2′-BP) adsorption at the electrochemically polished Bi(1 1 1) electrode from weakly acidified Na 2SO 4 supporting electrolyte solution. The influence of electrode potential on the adsorption kinetics of camphor and 2,2′-BP on Bi(1 1 1) has been demonstrated. In the region of maximal adsorption, i.e. capacitance pit in the differential capacitance versus electrode potential curve, the heterogeneous adsorption and diffusion steps are the rate determining stages for camphor and 2,2′-BP adsorption at the Bi(1 1 1) electrode. It was found that for camphor | Bi(1 1 1) interface the stable adsorbate adlayer detectable by using the in situ STM method has been observed only at the positively charged electrode surface, where the weak co-adsorption of SO 4 2− anions and camphor molecules is possible. At the weakly negatively charged Bi(1 1 1) electrode surface there are only physically adsorbed camphor molecules forming the compact adsorption layer. The in situ STM data in a good agreement with impedance data indicate that a very well detectable 2,2′-BP adsorption layer is formed at Bi(1 1 1) electrode in the wide region of charge densities around the zero charge potential.

Adsorption of camphor at Bi(111) electrode

Impedance spectroscopy and in situ STM methods have been used for investigation of the camphor adsorption at the electrochemically polished Bi(111) electrode from weakly acidified Na2SO4 base electrolyte aqueous solution. The influence of the electrode potential on the adsorption kinetics and camphor adsorption layer structure on Bi(111) has been demonstrated. In the region of the capacitance pit in the differential capacitance vs. electrode potential curve the so- called heterogeneous adsorption step is the rate determining stage for camphor adsorption at the electrochemically polished Bi(111) electrode, but not diffusion as usually assumed. It was found that the stable adsorbate adlayer detectable by using the in situ STM method has been observed only at the positively charged electrode surface, where the weak co-adsorption of SO42- anions and camphor molecules is possible. At the weakly negatively charged Bi(111) electrode surface there are only physically adsorbed camphor molecules forming the compact adsorption layer.

Interference between dielectronic and radiative recombination in electron - highly charged Bi collisions

Interference between radiative and dielectronic recombination in electron and highly charged Bi ion collisions has been studied by observing emitted x-rays with the Tokyo electron beam ion trap. The so-called Fano line shapes were fitted to the KLL DR resonant profiles observed as the enhancement of the x-ray counts. The shape parameters q have been determined similarly to the previous experiments for highly charged U [D A Knapp et al 1995 Phys. Rev. Lett. 74 54] and Hg ions [A J Gonzalez Martinez et al 2005 Phys. Rev. Lett. 94 20320]. The present results were compared to the previous results.

Charge-changing ion–ion collisions in heavy ion fusion

In heavy ion fusion, the compression of the DT pellet requires high intensity beams of ions in the gigaelectron volt energy range. Charge-changing collisions due to intrabeam scattering can have a high impact on the design of adequate accelerator and storage rings. Not only do intensity losses have to be taken into account, but also the deposition of energy on the beam lines after bending magnets, for example, may be nonnegligible. The center-of-mass energy for these intrabeam collisions is typically in the kiloelectron volt range for beam energies in the order of several gigaelectron volts. In this article, we present experimental cross sections for charge transfer and ionization in homonuclear collisions of Ar4+, Kr4+, and Xe4+, and for charge transfer only in homonuclear collisions of Pb4+ and Bi4+. Using a hypothetical 100-Tm synchrotron as an example, expected particle losses are calculated based on the experimental data. The results are compared with expectations for singly charged Bi+ ions, which are usually considered for heavy ion fusion.