A series of bismuth heterocycles, termed bismoles, were synthesized via the efficient metallacycle transfer (Bi/Zr exchange) involving readily accessible zirconacycles. The luminescence properties of three structurally distinct bismoles were explored in detail via time-integrated and time-resolved photoluminescence spectroscopy using ultrafast laser excitation. Moreover, time-dependent density functional theory computations were used to interpret the nature of fluorescence versus phosphorescence in these bismuth-containing heterocycles and to guide the future preparation of luminescent materials containing heavy inorganic elements. Specifically, orbital character at bismuth within excited states is an important factor for achieving enhanced spin-orbit coupling and to promote phosphorescence. The low aromaticity of the bismole rings was demonstrated by formation of a CuCl π-complex, and the nature of the alkene-CuCl interaction was probed by real-space bonding indicators derived from Atoms-In-Molecules, the Electron Localizability Indicator, and the Non-Covalent Interaction index; such tools are of great value in interpreting nonstandard bonding environments within inorganic compounds.
The synthesis of germanium nanocrystals (GeNCs) with well-defined surface chemistry is of considerable interest because of their potential applications in the optoelectronic, battery, and semiconductor industries. Modifying and tailoring GeNC surface chemistry provides an avenue by which reactivity, environmental compatibility (e.g., solubility, resistance to oxidation), and electronic properties may be tailored. Hydride-terminated GeNCs (H-GeNCs) are of particular interest because the reactivity of surface Ge-H bonds toward alkenes and alkynes via hydrogermylation affords the potential for convenient modification; however, these reactions and their scope have not been widely explored. This report describes a straightforward route for preparing a GeNC/GeO composite via disproportionation of heretofore-unexplored Ge(II) oxide-based precursor from which the H-GeNCs were freed by subsequently chemical etching. The H-GeNCs were derivatized using a series of hydrogermylation approaches (i.e., thermally activated, radical-initiated, and borane-catalyzed). The presented findings indicate surface functionalization occurs under all conditions investigated; however the nature of surface species (i.e., monolayers vs multilayers) and surface coverage varies depending upon the conditions employed.
Dynamic distortions and polaronic effects have been investigated in La0.8Ba0.2Mn1–xAlxO3 doped manganites of R3¯c symmetry. We studied the transport and magnetic properties and constructed a phase diagram of this system. We also analyzed the dependence of the transport data on the doping level x. The dependence of the polaron activation energy in the paramagnetic state on x doping was calculated and compared with the available literature data. The results suggest an interplay between a magnetic polaron mediated conductivity which dominates at low x and a bipolaron mediated one which controls electric transport at higher doping. It is suggested that the magnetic polaron formation is responsible for the increased magnetoresistance at low Al doping. Investigation on the nature of the magneto-transport mechanism of such ferromagnetic manganite will be useful in understanding its potential applications at the paramagnetic state.
Thermal diffusivities of Bi2Sr2CaCu2O8 superconductor at room temperature with the addition of different amounts of nano Ag (Bi2Sr2CaCu2O8-Agx with x=0-1.0) were measured using the open-cell photoacoustic technique. The thermal diffusivity was obtained by analyzing the phase of photoacoustic signal of thermally thick samples instead of analyzing the amplitude signal of thermally thick-to-thin samples. Two methods of phase analysis of thermally thick samples were applied, that is, Calderon’s method and the thermal diffusion model. The phase analysis is suitable where the dominanant mechanism contributing to the photoacoustic signal is thermal diffusion alone, which is true for Bi2Sr2CaCu2O8 superconductor. We have found that the thermal diffusivity increases with the amounts of nano-Ag. The values of thermal diffusivity obtained were between 0.012<th>50-0.001<th>28 and 0.016<th>06-0.002<th>30 cm2/s for Ag0 to Ag1.0.
This paper reports the results of thermal diffusivity measurement on nano Ag added Bi 2 Sr 2 CaCu 2 O 8- Ag x (with x = 0–1.0) ceramics using an open-cell photoacoustic instrument. The thermal diffusivities were obtained by analyzing the phase of the photo-acoustic signal of thermally thick samples using Calderon's method as well as the analysis of the phase in thermally thick region. We found that the thermal diffusivity increases with the amounts of nano Ag . The values of thermal diffusivity obtained were between 0.01250 ± 0.00128 to 0.01606 ± 0.00230 cm 2/ s for Ag 0 to Ag 1.0. The electrical resistance versus temperature measurements showed a metal-like behavior for all samples. However, a metal-like transition was observed between x = 0.5 and 0.7 when results of thermal diffusivity and electrical resistance measurements were analyzed together with samples x ≥ 0.7 showing the metallic behavior.
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