Commonality in the Origin and the Manifestation in the Real World of Electronegativity and Hardness

The electronegativity and the hardness are two different fundamental descriptors of atoms and molecules, and this chapter describes how the authors have logistically discovered the commonality between the heuristic and basic philosophical structures of their origin and also the manifestation in the real world. Also, the chapter demonstrates that the physical hardness and the chemical hardness with evolution of time have converged to one and the same general principle– the hardness. The authors also try to expose the physical basis and operational significance of another very important descriptor–the electronegativity. The chapter also explores whether the hardness equalization principle can be conceived analogous to the well established electronegativity equalization principle. The authors hypothesize that the electronegativity and the absolute hardness are two different appearances of the one and the same fundamental property of atoms, and the Hardness Equalization Principle can be equally conceived like the electronegativity equalization principle. To test this hypothesis, the authors have made several comparative studies by evaluating some well known chemico-physical descriptors of the real world, such as hetero nuclear bond distances, dipole charges, and dipole moments of molecules. The detailed comparative study suggests that the paradigm of the hardness equalization principle may be another law of nature like the established electronegativity equalization principle.

Dipole Moment as a Possible Diagnostic Descriptor of the Conformational Isomerism of the Ammonia Molecule

In this report, Ghosh and Rajak have made a detailed quantum mechanical study of the variation of the dipole moment of ammonia as a function of its conformations evolving during the process of its umbrella inversion by invoking their method of dipole correlation of electronic structure as basis. Ghosh et al discover a surprising result that the variation of dipole moment mimics the total energy curve as a function of reaction coordinates revealing the fact that the dipole moment is one possible diagnostic descriptor of the conformational isomerism of molecules containing lone pair electrons. The dipole is calculated and partitioned into bond and lone pair components for a large number of conformations between the equilibrium shape and the transition state of inversion and the results are interpreted and correlated in terms of the localized molecular orbitals, LMOs generated from the canonical molecular orbitals, CMO’s of each conformation. Anderson, from the concept of space time symmetry, postulated that ammonia has zero dipole moment. Present study reveals that Anderson’s correlation relied upon the bond moment only while the major component of dipole of ammonia originates from the lone pair of nitrogen.

On the Method of the Determination of the Global Hardness of Atoms and Molecules

Since, the hardness is a conceptual hypothesis only and not observable; there is no possibility of its quantum mechanical evaluation. Any attempt of modeling this abstract semiotic representation for the purpose of developing some mathematical algorithms and to convert it into theoretical quantities of cognitive representations, it is required that the hardness should be reified in terms of the physico-chemical behavior of such conundrums goaded by the quantum mechanical principles. Some scales of measurement of hardness are introduced with the evolution of time.

On the Modeling of Carbon Nanotubes as Drug Delivery Nanocapsules

The structure of carbon nanotubes is recognized to be suitable for medical applications such as encapsulating drugs or genes with the aim of targeted deliveries. In this regard, knowing about the suction force exerted on a nonoscale object which is supposed to be sucked into a carbon nanotube, and whether the object is accepted by the carbon nanotube are important issues to be studied. In this chapter, considering the nanoscale object as a carbon nanotube, a new semi-analytical method is developed to determine the van der Waals interaction between two concentric single-walled carbon nanotubes.

Probing the Reactive Center for Site Selective Protonation in a Molecule by the Local Density Functional Descriptors

In this study, the authors have explored the efficacy of the local density functional descriptors like the fukui functions (f), the local softness (s) and the local philicity as probe for the reactive centers and site selectivity of the chemico-physical process of protonation of some molecules having multiple site for protonation, viz CH3NCO (Methyl isocyanate), CH3NCS (methyl isothiocyanate), NH2OH (hydroxyl amine), NH2OCH3 (o-methylhydroxylamine), CH3NHOH (N-methylhydroxylamine), NH2CH2COOH (glycine), CH3CH(NH2)COOH (alanine) and OHCH2CH2NH2 (ethanol amine). The authors have seen in terms of the numerical values of the local descriptors measures the reactivity (nucleophilicity) of a particular atomic site of a donor center towards a proton. In all cases, it can be said that the dynamic chemico-physical process of site selectivity can nicely be correlated in terms of the computed values of the local descriptors. Thus, it is found that the theoretical descriptors of the DFT can be efficiently exploited to study the mechanism of site selectivity in a chemical reaction.

Biological Synthesis of Silver Nanoparticles and their Functional Properties

A nanoparticle is defined as a small object between 1 and 100 nanometer in size and has a large surface to volume ratio. Silver nanoparticles (AgNPs) could be synthesized using various chemical and physical processes. However, these methods lead to hazardous by-products. In the recent past, AgNPs are produced by biological means. The size, shape and composition of AgNPs have significant effect on their biological applications. Aqueous solution of AgNP is not stable and rapidly undergoes agglomeration which is prevented by electrostatic or steric stabilization techniques with the help of capping or protective agents. The biologically synthesized nanoparticles are now favoured because it is a green alternative, mild, and does not need toxic chemicals and solvents. The scope of this review is to provide an overview of the various biological means researched for the synthesis of AgNPs, different techniques and chemicals used to develop stable solution, various techniques for their characterization, and their biological. The future research directions in this subject area are also dicussed.

Nanoroots of Quantum Chemistry Atomic Radii, Periodic Behavior, and Bondons

This chapter identifies specific roots of chemistry and quantum chemistry and advances the idea that length and energy carry major roles at the nano-quantum level. A detailed exposition of this binom is unfolded under the specific radii-electronegativity or radii-chemical hardness that is then naturally extended to the radii-chemical descriptors relationships, having the atomic periodicity as the main benchmark check for their reliability. As such, considering different analytic electronegativity scales, they are reported and compared to the respective atomic orbital radii scales, both for the electronic density formulation, as uniform atomic electronic assembly, and for Slater type density orbital, respectively. The scheme for atomic orbital radii is further generalized by chemical descriptors in the frame of density functional theory. Finally, the chemical bond is treated through introducing the chemical quantum particle-the bondon-as a molecular nano-reality in modeling the energy-length space towards the chemical space, or bonding and reactivity. The existence of the chemical field along the associate bondon particle characterized by its mass (), velocity (), charge (), and life-time () are revealed by employing the combined Bohmian quantum formalism with the U(1) and SU(2) gauge transformations of the non-relativistic wave-function and the relativistic spinor, within the Schrödinger and Dirac quantum pictures of electronic motions.

Cluster Origin of Solvent Features of Fullerenes, Single-Wall Carbon Nanotubes, Nanocones, and Nanohorns

This chapter discusses the existence of single-wall carbon nanocones (SWNCs), especially nanohorns (SWNHs) in organic solvents in the form of clusters. A theory is developed based on a bundlet model describing their distribution function by size. Phenomena have a unified explanation in bundlet model in which free energy of an SWNC, involved in a cluster, is combined from two components: a volume one, proportional to number of molecules n in a cluster, and a surface one proportional to n1/2. A bundlet model enables describing distribution function of SWNC clusters by size. From purely geometrical differences, bundlet (SWNCs) and droplet (fullerene) models predict different behaviours. The SWNCs of various disclinations are investigated via energetic–structural analyses. Several SWNC’s terminations are studied which are different among one another because of the type of closing structure and arrangement. Packing efficiencies and interaction-energy parameters of SWNCs/SWNHs are intermediate between fullerene and single-wall carbon nanotube (SWNT) clusters.

Nanostructured Metal Oxide Gas Sensor

This chapter provides a review of recent progress in gas sensor based on semiconducting metal oxide nanostructure. The response mechanism and development of various methods to enhancement of sensing properties receives the most attention. Theoretical models to explain the effects of morphology, additives, heterostructured composite and UV irradiation on response improvement were studied comprehensively. Investigations have indicated that 1D nanostructured metal oxide with unique geometry and physical properties display superior sensitivity to gas species. Also, the proposed conduction model in gas sensor based on 1D Metal oxide is discussed. Finally, the response mechanism of hierarchical and hollow nanostructures as novel sensing materials is addressed.

DFT Correlation of the Site Selectivity of Donor–Acceptor Chemical Interaction

In this study, the time evolution of concept local HSAB principle as a necessary prelude to our jargon of the trade Correlation of the Site Selectivity of Donor–Acceptor Chemical Interaction in terms of the Local Density Functional Descriptors is discussed at length . The authors try to correlate the known facts relating to the formations of some donor acceptor supermolecules such as HCN–BF3,HNC–BF3, H3C–CN–BF3 and H3C–NC–BF3 by the chemical interaction of a well known Lewis acid, BF3 and various donor ligands/Lewis bases like HCN,HNC,H3C–CN, H3C–NC which are inherently structural isomers having multiple donating sites, in terms of the local DFT descriptors like the local softness (s) and fukui functions (f) of such chemical systems. It is also noted that the dynamic chemico-physical process of site selectivity is found to have a very nice correlation in terms of the computed values of the local descriptors namely the fukui functions and the local softnesses. Thus, the authors find that the theoretical descriptors of the local HSAB principle can be efficiently exploited to study the mechanism of site selectivity in a chemical reaction.