Liming Dai,*,†,‡ Yuhua Xue,†,‡ Liangti Qu,* Hyun-Jung Choi, and Jong-Beom Baek* †Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Department of Chemistry, School of Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China School of Energy and Chemical Engineering/Center for Dimension-Controllable Covalent Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, 689-798, South Korea

Metal-free catalysts for oxygen reduction reaction.

Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

During the past decade, enormous progress has been made in growing ultrathin organic films and multilayer structures with a wide range of exciting optoelectronic properties. This progress has been made possible by several important advances in our understanding of organic films and their modes of growth. Perhaps the single most important advance has been the use of ultrahigh vacuum (UHV) as a means to achieve, for the first time, monolayer control over the growth of organic thin films with extremely high chemical purity and structural precision.1-3 Such monolayer control has been possible for many years using well-known techniques such as Langmuir-Blodgett film deposition,4 and more recently, self-assembled monolayers from solution have also been achieved.5 However, ultrahighvacuum growth, sometimes referred to as organic molecular beam deposition (OMBD) or organic molecular beam epitaxy (OMBE), has the advantage of providing both layer thickness control and an atomically clean environment and substrate. When combined with the ability to perform in situ highresolution structural diagnostics of the films as they are being deposited, techniques such as OMBD have provided an entirely new prospect for understanding many of the fundamental structural and optoelectronic properties of ultrathin organic film systems. Since such systems are both of intrinsic as well as practical interest, substantial effort worldwide has been invested in attempting to grow and investigate the properties of such thin-film systems. This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods. We will describe the most important work which has been published in this field since the emergence of OMBD in the mid-1980s. Both the nature of thin-film growth and structural ordering will be discussed, as well as some of the more interesting consequences to the physical properties of such organic thin-film systems will be considered both from a theoretical as well as an experimental viewpoint. Indeed, it will 1793 Chem. Rev. 1997, 97, 1793−1896

Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques.

It is estimated that the world will need to double its energy supply by 2050. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new materials, particularly carbon nanomaterials, for efficient energy conversion and storage. Comparing to conventional energy materials, carbon nanomaterials possess unique size-/surface-dependent (e.g., morphological, electrical, optical, and mechanical) properties useful for enhancing the energy-conversion and storage performances. During the past 25 years or so, therefore, considerable efforts have been made to utilize the unique properties of carbon nanomaterials, including fullerenes, carbon nanotubes, and graphene, as energy materials, and tremendous progress has been achieved in developing high-performance energy conversion (e.g., solar cells and fuel cells) and storage (e.g., supercapacitors and batteries) devices. This article reviews progress in the research and development of carbon nanomaterials during the past twenty years or so for advanced energy conversion and storage, along with some discussions on challenges and perspectives in this exciting field.

Carbon Nanomaterials for Advanced Energy Conversion and Storage

It is shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions). A more complete theory is developed. It is shown that excitons are approximate bosons, and, in interaction with the electromagnetic field, the exciton field plays the role of the classical polarization field. The eigenstates of the system of crystal and radiation field are mixtures of photons and excitons. The ordinary one-quantum optical lifetime of an excitation is infinite. Absorption occurs only when "three-body" processes are introduced. The theory includes "local field" effects, leading to the Lorentz local field correction when it is applicable. A Smakula equation for the oscillator strength in terms of the integrated absorption constant is derived.

a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals.

Neutron inelastic scattering experiments have been carried out to measure the phonon energies of deuterated naphthalene C10D8 for the lowest 12 dispersion branches along ( xi 00) and (00 xi ) directions at various temperatures ranging from 6 to 300K. Using measured mode Gruneisen parameters the quasiharmonic shifts related to the deformation of the lattice and to the temperature-dependent anharmonic self-energy shift were obtained separately. For calculations the authors used the rigid molecule model based on the '6-exp' potential.

http://iopscience.iop.org/article/10.1088/0022-3719/17/33/004/pdf

Anharmonicity of phonons in crystalline naphthalene

An extended quantum-chemical study has been performed to examine the flame-generated silica formation at the atomic level. Starting from a set of free molecules, condensation was shown to be a non-barrier and energetically favorable. The coalescence of the formed bare-surface protoparticles can be prevented by particle surface passivation in the course of the hydroxylation reaction. The protoparticle size is determined by a balance of the fusion and hydroxylation/dehydroxylation processes. The main factors responsible for the inherent amorphicity of the fumed silica have been determined.

From Molecules to Particles: Quantum-chemical View Applied to Fumed Silica

The current paper is aimed at the determination of barriers that govern the covalent coupling between partners of C60-based composites consisting of two fullerenes C60 (C60 dimer), C60 and single-walled carbon nanotubes ([C60-(4,4)] carbon nanobuds), and C60 and graphene ([C60-(5,5)] and [C60-(9,8)] graphene nanobuds). Barrier energies are determined as coupling ones Etotcpl and are expanded over two contributions that present the total energy of deformation of the composites' components Etotdef and the energy of covalent coupling Etotcov. In view of these energetic parameters and in contrast to expectations, seemingly identical reactions that are responsible for the formation of intermolecular [2 + 2] cycloadditions in the studied composites result in different final products. This peculiarity is suggested to occur as a result of the topochemical character of the covalent coupling between the two members of the studied composites, once additionally complicated by the varied donor–acceptor contribution.

C60-based composites in view of topochemical reactions

The response of a nanographene sheet to external stresses is considered in terms of a mechanochemical reaction. The quantum chemical realization of the approach is based on a coordinate-of-reaction concept for the purpose of introducing a mechanochemical internal coordinate (MIC) that specifies a deformational mode. The related force of response is calculated as the energy gradient along the MIC, while the atomic configuration is optimized over all of the other coordinates under the MIC constant-pitch elongation. The approach is applied to the benzene molecule and (5, 5) nanographene. A drastic anisotropy in the microscopic behavior of both objects under elongation along a MIC has been observed when the MIC is oriented either along or normally to the C-C bonds chain. Both the anisotropy and high stiffness of the nanographene originate at the response of the benzenoid unit to stress.

Structure-Sensitive Mechanism of Nanographene Failure

We present the investigation of the electronic structure of X60 molecules (X=C, Si), containing 60 odd electrons with spin-dependent interaction between them. Conditions for the electrons to be excluded from the covalent pairing are discussed. A computational spin-polarized quantum-chemical scheme is suggested to evaluate four parameters—energy of radicalization, exchange integral, atom spin density, and squared spin— to characterize the effect quantitatively. A polyradical character of the species, weak for C60 and strong for Si60, is established.

/pdf/fullerenes-as-polyradicals-27tzp0arfv.pdf

Elena F. Sheka

Papers

Anharmonicity of phonons in crystalline naphthalene

From Molecules to Particles: Quantum-chemical View Applied to Fumed Silica

C60-based composites in view of topochemical reactions

Structure-Sensitive Mechanism of Nanographene Failure

Fullerenes as polyradicals