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Nanomaterials, Nanoelectronics, and Nanofabrication Technology
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
SWCNTs can behave as a metal or a semiconductor depending on the intrinsic bandgap and chirality. Chirality is the noun of chiral: an asymmetric nature in which the structure and its mirror image are not superimposable. A biological example of chiral is a human hand in which both right and left hands are structurally the same but the right hand is a mirror image of the left hand. Chemically, chiral compounds are typically optically active; large organic molecules often have one or more chiral centers where four different groups are attached to a carbon atom. For an SWCNT, the chirality is the amount of “twist” present in the tube. If you think of SWCNTs as a rolled-up graphene sheet made up of hexagons (see Figure 8.2), the chirality is how far the axis of the tube (line down center of tube) is from being parallel to one side of the hexagons (y-axis in Figure 8.2) [12]. If the tube axis is parallel, the SWCNT will be semiconducting. The chirality of nanotubes has a significant impact on their transport properties, particularly the electronic properties [13].
Stereochemistry
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Organic molecules are three-dimensional, and this property leads to isomers that differ only in their spatial arrangement. Such molecules are called stereoisomers, and special properties are associated with stereoisomers that possess stereogenic atoms (an atom that possesses four different groups or atoms). This chapter will introduce the concepts of chirality, including enantiomers, diastereomers, meso compounds, and absolute configuration. The Cahn–Ingold–Prelog selection rules will be introduced in order to determine the absolute configuration of a stereogenic center. The optical properties of stereogenic molecules will also be discussed, including the highly important physical property, specific rotation.
Linear Raman Spectroscopy
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
Recall that chirality is a geometric property of (some) molecules, meaning that such a molecule is nonsuperposable on its mirror image. For example, the presence of an asymmetric carbon center is one of several structural features that are responsible for chirality in molecules. Note that left- and right-hand configurations of chiral molecules are often dubbed enantiomers. The left- and right-handed variants carry the labels S and R, respectively; they indicate the absolute configuration of the molecule; i.e., they refer to the actual orientation in space of the substituents around the stereo-center. This nomenclature allows one to describe the steric configuration of molecules, without the need for a 3D picture representation.
Optimal design of electromagnetic metamaterial electronic device sensor with specific performance based on multivariate big data fusion
Published in Journal of Experimental Nanoscience, 2023
An important research direction in the field of metamaterials is to study chiral and related electromagnetic phenomena [6]. Chirality refers to the geometric property that a structure cannot coincide with its mirror image after translation and rotation. Chiral metamaterials are one kind of chiral materials, which can exhibit two important electromagnetic properties: circular birefringence and circular dichroism. Circular birefringence refers to the ability of a structure to rotate the polarization plane of electromagnetic waves. Circular dichroism refers to the difference in the propagation of right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) waves in chiral media. Subsequent studies have shown that planar chiral metamaterials can also produce another novel phenomenon: asymmetric transmission (AT). This special phenomenon was first discovered by Fedotov and others in 2006 [7]. Due to these special electromagnetic characteristics of electromagnetic metamaterials, many researchers have designed a variety of miniature microwave components and applied them in the field of wireless communication and defense industry [8]. The structural loss of metamaterials has become a major problem in its application field [9]. It has certain practical value and is beneficial to broaden the application of electromagnetic metamaterial in the field of antenna and microwave devices [10].
A review on the energy absorption response and structural applications of auxetic structures
Published in Mechanics of Advanced Materials and Structures, 2022
Matheus Brendon Francisco, João Luiz Junho Pereira, Guilherme Antônio Oliver, Lucas Ramon Roque da Silva, Sebastião Simões Cunha, Guilherme Ferreira Gomes
Chiral model is the type of structure that responds to a compressive force with one rotation, something that is normally done using a transmission and a crankshaft [80]. Thinking of an automotive engine, there is burning of fuel inside the cylinder that generates a linear movement of the piston. The piston pushes the connecting rod that is connected to the crankshaft, and it is the crankshaft that produces rotation. The term chirality is used to define an object that cannot be superimposed on its mirror image. Prall and Lakes [13] analyzed the Poisson's ratio of chiral structures through theoretical and experimental analyzes for plane deformations. The parameters used in the approach of the authors are shown in Figure 5. They analyzed the deformation of the material and arrived at Equations (21)–(23) (the parameters of equation are shown in Figure 5).
Photodissociation study of spatially oriented (R)-3-bromocamphor by the hexapole state selector
Published in Molecular Physics, 2022
Hsiu-Pu Chang, Masaaki Nakamura, Toshio Kasai, King-Chuen Lin
One big challenge, using asymmetric top molecules, is their chiral discrimination. Palazzetti et al. [19] predicted that the photofragment scattering distribution of the enantiomers could be discriminated in those angular distributions if the parent chiral molecules were oriented. The photofragment angular distribution of oriented molecules depends on the molecular orientation and photodissociation dynamics. For different enantiomers of chiral molecules, the permanent dipole moments, the transition dipole moments and the (most probable) recoil velocity vectors will have identical magnitudes, but will have mirror images reflecting its chirality. Hence, the difference could result in different photofragment distributions to discriminate enantiomers with an appropriate experimental set-up. Although the molecules we have tested did not show an apparent difference because of the almost achiral geometric condition of the three vectors, it is a notable application of molecular orientation: the chiral discrimination combines an achiral light source and molecular orientation to realise a chiral detection.