13 Search Results

Novel nanocarbons such as fullerenes, nanotubes, graphene, and nanodiamond reside at the cutting edge of nanoscience and technology. Along with chemical functionalization, geometric constraints (such as extreme curvature in nanotubes or defects within or at the surfaces of diamond nanoparticles) significantly alter the electronic states of the nanocarbon material. Understanding the effects of steric strain on the electronic structure is critical to developing nanoelectronic applications based on these materials. This paper presents a fundamental study of how strain affects the electronic structure in a benchmark series of some fundamental saturated carbon cage compounds. Adamantane, C₁₀H₁₆, the smallest diamondoid and arguablymore » the smallest nanodiamond crystallite, has carbon atoms essentially commensurate with diamond lattice positions and possesses by far the least molecular strain of this series. Twistane also is a C₁₀H₁₆ isomer but the fixed cyclohexane twist conformation of the central ring introduces additional strain into the cage. Octahedrane [(CH)₁₂] and cubane [(CH)₈] are considerably more strained, culminating in cubane where carbon–carbon bonds lie either parallel or orthogonal to one another. Using gas-phase near-edge x-ray absorption fine structure spectroscopy to probe the unoccupied electronic states, we observe two major progressions across this series. First, a broad C–C σ* resonance in the absorption splits into two more narrow and intense resonances with increasing strain. Second, the first manifold of states previously associated with tertiary C–H σ* in the diamondoid series appears to broaden and shift to lower energy. This feature is more than twice as intense in cubane than in octahedrane, even though these two molecules have only tertiary carbons, with the chemical formula (CH)x. The spectral differences are entirely due to the shape of the molecules; in particular, in cubane, the features arise from a high degree of p-p interaction between parallel C–C bonds. In contrast to the conventional wisdom that near-edge x-ray absorption is primarily an atomically localized spectroscopy, molecular shape and associated strain lead to the dominant features in spectra acquired from this fundamental series of carbon cage structures.« less

Platinum-based antineoplastic agents play a major role in the treatment of numerous types of cancer.

Abstract Owing to the high abundance and gravimetric capacity (1165.78 mAh g ⁻¹ ) of pure sodium, it is considered as a promising candidate for the anode of next‐generation batteries. However, one major challenge needs to be solved before commercializing the sodium metal anode: The growth of dendrites during metal plating. One possibility to address this challenge is to use additives in the electrolyte to form a protective solid electrolyte interphase on the anode surface. In this work, we introduce a diamondoid‐based additive, which is incorporated into the anode to target this problem. Combining operando and ex situ experiments (electrochemical impedance spectroscopy, opticalmore » characterization, and cycling experiments), we show that molecular diamondoids are incorporated into the anode during cycling and successfully mitigate the growth of dendrites. Furthermore, we demonstrate the positive effect of the additive on the operation of sodium‐oxygen batteries by means of increased energy density.« less

Deciphering absolute configuration of a single molecule by direct visual inspection is the next step in compound identification, with far-reaching implications for medicinal chemistry, pharmacology, and natural product synthesis. We demonstrate the feasibility of this approach utilizing low temperature atomic force microscopy (AFM) with a CO-functionalized tip to determine the absolute configuration and orientation of a single, adsorbed [123]tetramantane molecule, the smallest chiral diamondoid. We differentiate between single enantiomers on Cu(111) by direct visual inspection, and furthermore identify molecular dimers and molecular clusters. The experimental results are confirmed by a computational study that allowed quantification of the corresponding intermolecular interactions.more » The unique toolset of absolute configuration determination combined with AFM tip manipulation opens a route for studying molecular nucleation, including chirality-driven assembly or reaction mechanisms.« less

The enigmatic near-UV absorber, OSSO, in the yellowish atmosphere of Venus and three novel isomers have been spectroscopically characterized.

Two SO₃isomers,cis-OSOO and cyclic OS(✓O)O, were formed in the oxidation of SO and trapped in cryogenic matrices for spectroscopic characterization.

The monochromatic photoemission from diamondoid monolayers provides a new strategy to create electron sources with low energy dispersion and enables compact electron guns with high brightness and low beam emittance for aberration-free imaging, lithography, and accelerators. However, these potential applications are hindered by degradation of diamondoid monolayers under photon irradiation and electron bombardment. Here, we report a graphene-protected diamondoid monolayer photocathode with 4-fold enhancement of stability compared to the bare diamondoid counterpart. The single-layer graphene overcoating preserves the monochromaticity of the photoelectrons, showing 12.5 meV ful width at half-maximum distribution of kinetic energy. Importantly, the graphene coating effectively suppresses desorptionmore » of the diamondoid monolayer, enhancing its thermal stability by at least 100 K. Furthermore, by comparing the decay rate at different photon energies, we identify electron bombardment as the principle decay pathway for diamondoids under graphene protection. As a result, this provides a generic approach for stabilizing volatile species on photocathode surfaces, which could greatly improve performance of electron emitters.« less

Abstract A novel approach for the bottom‐up construction of hybrid organic–inorganic nanocomposites with an intimate arrangement between sp ³ ‐carbon 3D molecular‐size nanodiamonds (diamondoids) and a coated palladium surface as nanolayer is reported. The construction process is conducted stepwisely from the gas phase, using first controlled vapor‐phase self‐assembly of tailor‐made functionalized diamantane derivatives, followed by low‐temperature (45 °C) chemical vapor deposition of an organometallic complex in a reducing H ₂ atmosphere over the self‐assembled diamondoid scaffold. The use of self‐assemblies of primary diamantane phosphine and phosphine oxide, which are produced with high structural uniformity and reproducibility, yields new hybrid diamondoid‐palladiummore » materials incorporating PdOPHdiamantane bonding motifs. Additional investigations provide evidence for a very challenging issue in the intimate construction of sp ³ ‐C/metal scaffolds. Scanning electron microscopy and transmission electron microscopy microscopies combined with X‐ray photoelectron spectroscopy surface analysis and EDX bulk analysis confirm the formation of diamondoid‐palladium organohybrids with unique surface layering. The vapor phase‐controlled mild synthetic process allows excellent control over nanocomposite formation and morphology from molecular‐level modifications. As such, this bottom‐up composite building process bridges scales from the molecular (functionalized diamondoids) over nanoscopic (self‐assemblies) to microscopic regime (hybrids), in the challenging association of transition metals with an electronically saturated sp ³ ‐carbon organic host material.« less

Abstract The fusion of the sp ³ ‐hybridized parent diamondoid adamantane with the sp ² ‐hybridized pyrene results in a hybrid structure with a very large dipole moment which arises from bending the pyrene moiety. Presented herein is the synthesis, study of the electronic and optical properties, as well as the dynamic behavior of this new hydrocarbon.

Abstract The fusion of the sp ³ ‐hybridized parent diamondoid adamantane with the sp ² ‐hybridized pyrene results in a hybrid structure with a very large dipole moment which arises from bending the pyrene moiety. Presented herein is the synthesis, study of the electronic and optical properties, as well as the dynamic behavior of this new hydrocarbon.