The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

The electronic properties of graphene, a two-dimensional crystal of carbon atoms, are exceptionally novel. For instance, the low-energy quasiparticles in graphene behave as massless chiral Dirac fermions which has led to the experimental observation of many interesting effects similar to those predicted in the relativistic regime. Graphene also has immense potential to be a key ingredient of new devices, such as single molecule gas sensors, ballistic transistors and spintronic devices. Bilayer graphene, which consists of two stacked monolayers and where the quasiparticles are massive chiral fermions, has a quadratic low-energy band structure which generates very different scattering properties from those of the monolayer. It also presents the unique property that a tunable band gap can be opened and controlled easily by a top gate. These properties have made bilayer graphene a subject of intense interest. In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene f...

Properties of graphene: a theoretical perspective

Metal-organic frameworks (MOFs) are typically highlighted for their potential application in gas storage, separations and catalysis. In contrast, the unique prospects these porous and crystalline materials offer for application in electronic devices, although actively developed, are often underexposed. This review highlights the research aimed at the implementation of MOFs as an integral part of solid-state microelectronics. Manufacturing these devices will critically depend on the compatibility of MOFs with existing fabrication protocols and predominant standards. Therefore, it is important to focus in parallel on a fundamental understanding of the distinguishing properties of MOFs and eliminating fabrication-related obstacles for integration. The latter implies a shift from the microcrystalline powder synthesis in chemistry labs, towards film deposition and processing in a cleanroom environment. Both the fundamental and applied aspects of this two-pronged approach are discussed. Critical directions for future research are proposed in an updated high-level roadmap to stimulate the next steps towards MOF-based microelectronics within the community.

/pdf/an-updated-roadmap-for-the-integration-of-metal-organic-4ryw3jm11n.pdf

An updated roadmap for the integration of metal–organic frameworks with electronic devices and chemical sensors

Main-group analogues to fullerene-C60 have been predicted theoretically many times. Now, B40− has been observed using photoelectron spectroscopy and, with its neutral analogue, B40, confirmed computationally. In contrast to fullerene-C60, the all-boron fullerene (or borospherene) features triangles, hexagons and heptagons, bonded uniformly by delocalized σ and π bonds over the cage surface.

http://casey.brown.edu/chemistry/research/LSWang/publications/399.pdf

Observation of an all-boron fullerene.

Based on a series of ab initio studies we have pointed out the remarkable structural stability of nanotubular and quasiplanar boron clusters, and postulated the existence of novel layered, tubular, and quasicrystalline boron solids built from elemental subunits. The present study illustrates and predicts qualitative structural and electronic properties for various models of nanotubular and layered boron solids, and compares them to well-known tubular and layered forms of pure carbon and mixed boron compounds.

/pdf/new-boron-based-nanostructured-materials-1oivnl5tii.pdf

New boron based nanostructured materials

Based on a numerical ab initio study, we discuss a structure model for a broad boron sheet, which is the analog of a single graphite sheet, and the precursor of boron nanotubes. The sheet has linear chains of $sp$ hybridized $\ensuremath{\sigma}$ bonds lying only along its armchair direction, a high stiffness, and anisotropic bonds properties. The puckering of the sheet is explained as a mechanism to stabilize the $sp$ $\ensuremath{\sigma}$ bonds. The anisotropic bond properties of the boron sheet lead to a two-dimensional reference lattice structure, which is rectangular rather than triangular. As a consequence the chiral angles of related boron nanotubes range from 0\ifmmode^\circ\else\textdegree\fi{} to 90\ifmmode^\circ\else\textdegree\fi{}. Given the electronic properties of the boron sheets, we demonstrate that all of the related boron nanotubes are metallic, irrespective of their radius and chiral angle, and we also postulate the existence of helical currents in ideal chiral nanotubes. Furthermore, we show that the strain energy of boron nanotubes will depend on their radii, as well as on their chiral angles. This is a rather unique property among nanotubular systems, and it could be the basis of a different type of structure control within nanotechnology.

/pdf/broad-boron-sheets-and-boron-nanotubes-an-ab-initio-study-of-5a429szhwk.pdf

Broad boron sheets and boron nanotubes: An ab initio study of structural, electronic, and mechanical properties

We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems and show that there are at least three very natural mechanisms - edge reconstruction, edge passivation, and edge closure - which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be stable at room temperature. Charge doping and the presence of edge defects further destabilize the intrinsic magnetism of such systems.

http://nano.tu-dresden.de/pubs/reprints/2011_PRB_83_045414.pdf

Stability of edge states and edge magnetism in graphene nanoribbons

Using ab initio quantum-chemical and density functional methods we have determined novel structures of bare boron clusters. In addition to previously reported quasi-planar, convex and spherical cluster forms, boron nanotubules seem to be highly stable as well. These novel nanotubular structures are composed of hexagonal pyramids only and can be considered as segments of extended pipes. Applying a previously reported "Aufbau Principle", one can easily construct stable boron structures besides the new nanotubular clusters described below. Thus the Aufbau principle should help in illuminating the chemical and physical nature of new boron materials based on boron nanotubules.

https://iopscience.iop.org/article/10.1209/epl/i1997-00388-9/pdf

Nanotubules of bare boron clusters: Ab initio and density functional study

Plasmonic structures for light manipulation at sub-wavelength scale have received great interest in the field of photovoltaic (PV) solar cells for their potential to significantly enhance the cell's efficiency. The performance of any solar cell is determined by the capability to absorb incoming light and produce electric charges, which, in turn, has a number of limiting factors. One is related to the ever-reducing size and acceptance angle of the active region. Another is the limited spectral sensitivity of the active material, which cannot make use of significant parts of the solar spectrum. Correspondingly, the energy harvesting may be improved in two ways, namely by adopting light trapping schemes and by exploiting spectral modification processes to shift frequencies of the solar spectrum, which are initially not absorbed, into the region of maximum absorption of the cell. Plasmonic nanoparticles (NPs) can give a significant boost to both these aspects, by scattering and concentrating the electromagnetic field into the active region of the device, and by doing that within specific spectral regions, which can be properly tuned by optimizing the size, shape, distribution of the plasmonic NPs, and by choosing the right surrounding medium. During the last ten years, many papers have been published on very specific issues, but also on general properties of plasmonics applied to solar cells, with a strong increase between 2006 and 2012, followed by a period of significant, but stable, literature productivity. Given these premises, an organized and schematic summary of the main strategies and of the recent results on the field is given in this review, where different plasmonic approaches are compared and discussed, also by recalling specific examples from the literature and providing a few key conclusions to understand the main aspects and the future perspectives of the field.

Alexander Quandt

Papers

New boron based nanostructured materials

Broad boron sheets and boron nanotubes: An ab initio study of structural, electronic, and mechanical properties

Stability of edge states and edge magnetism in graphene nanoribbons

Nanotubules of bare boron clusters: Ab initio and density functional study

Plasmonic enhanced solar cells: Summary of possible strategies and recent results