Screw Dislocation Driven Growth of Nanomaterials

Abstract

Nanoscience and nanotechnology impact our lives in many ways, from electronic and photonic devices to biosensors. They also hold the promise of tackling the renewable energy challenges facing us. However, one limiting scientific challenge is the effective and efficient bottom-up synthesis of nanomaterials. We can approach this core challenge in nanoscience and nanotechnology from two perspectives: (a) how to controllably grow high-quality nanomaterials with desired dimensions, morphologies, and material compositions and (b) how to produce them in a large quantity at reasonable cost. Because many chemical and physical properties of nanomaterials are size- and shape-dependent, rational syntheses of nanomaterials to achieve desirable dimensionalities and morphologies are essential to exploit their utilities. In this Account, we show that the dislocation-driven growth mechanism, where screw dislocation defects provide self-perpetuating growth steps to enable the anisotropic growth of various nanomaterials at low supersaturation, can be a powerful and versatile synthetic method for a wide variety of nanomaterials. Despite significant progress in the last two decades, nanomaterial synthesis has often remained an "art", and except for a few well-studied model systems, the growth mechanisms of many anisotropic nanostructures remain poorly understood. We strive to go beyond the empirical science ("cook-and-look") and adopt a fundamental and mechanistic perspective to the anisotropic growth of nanomaterials by first understanding the kinetics of the crystal growth process. Since most functional nanomaterials are in single-crystal form, insights from the classical crystal growth theories are crucial. We pay attention to how screw dislocations impact the growth kinetics along different crystallographic directions and how the strain energy of defected crystals influences their equilibrium shapes. Furthermore, such inquiries are supported by detailed structural investigation to identify the evidence of dislocations. The dislocation-driven growth mechanism not only can unify the various explanations behind a wide variety of exotic nanoscale morphologies but also allows the rational design of catalyst-free solution-phase syntheses that could enable the scalable and low cost production of nanomaterials necessary for large scale applications, such as solar and thermoelectric energy conversions, energy storage, and nanocomposites. In this Account, we discuss the fundamental theories of the screw dislocation driven growth of various nanostructures including one-dimensional nanowires and nanotubes, two-dimensional nanoplates, and three-dimensional hierarchical tree-like nanostructures. We then introduce the transmission electron microscopy (TEM) techniques to structurally characterize the dislocation-driven nanomaterials for future searching and identifying purposes. We summarize the guidelines for rationally designing the dislocation-driven growth and discuss specific examples to illustrate how to implement the guidelines. By highli...

Face the Edges: Catalytic Active Sites of Nanomaterials

“…Crystals can be enlarged through screw dislocations under proper supersaturations in two competing directions, directions of in‐plane and vertical to plane 56. For layered structures, the growth rates of these two directions are inherently different, thus the growth manner can be proper controlled.…”

Yukawa-like confinement potential of a scalar particle in a Gödel-type spacetime with any l

“…In this regard, see the energy levels of a hydrogen atom placed in the gravitational fields of a cosmic string or a global monopole [5], and the correction of energy levels depends on the features of the specific space-time. Also, during the last decades, some authors have widely studied the influences of topological defects on the non-relativistic or relativistic quantum systems such as bound states of electrons and holes to a disclination [6], the influence of the screw dislocation on the energy levels of nona e-mail: eshgi54@gmail.com; m.eshghi@semnan.ac.ir relativistic electrons [7], screw dislocations driven growth of nanomaterials [8], topological defects space times [9], the Landau levels in the presence of topological defects [10,11], the influence of Coulomb potential and quantum oscillator in conical spaces [12], exact solutions of the Klein-Gordon equation in cosmic string space-time [13,14] and others [15][16][17].…”

Eshelby twist and correlation effects in diffraction from nanocrystals

“…4 The discovery of branched nanowires and the chiral pattern produced by the Eshelby twist allows for the observation of this twist using real space imaging tools such as scanning electron microscopes. An alternative technique for the observation of dislocations and twist, which Eshelby mentioned in his original paper, is X-ray diffraction (XRD).…”