Chiral 3D CdSe Nanotetrapods

Abstract

Three-dimensional (3D) nanomaterials have been intensively investigated because of their unique properties and wide range of potential applications; however, the ligand-induced chirality in 3D semiconductor nanocrystals has been scarcely studied. In this paper, we report the synthesis of hydrophobic 3D CdSe nanotetrapods (Tps) with a high degree of uniformity in their morphology by using the hot-injection method. The core and arms of Tps are distinct in their crystal structure, thus creating an intracrystal heterojunction. The size of Tps, primarily the length of four arms, is controlled by changing the amount of didecyldimethylammonium bromide and reaction time. Next, enantiopure cysteine ligands were introduced to replace the hydrophobic native stabilizers to prepare chiral l- and d-cysteine-capped CdSe Tps. Importantly, the circular dichroism (CD) line shapes of l/d-cysteine-capped CdSe Tps are assigned to the different excitonic transitions of the core and arms, respectively. In addition, the observed CD activities are found to be sensitive to the size of the CdSe Tps, where the anisotropic g factors have increased and reached the maximum value at a moderate aspect ratio (AR) and a further increase of the AR leads to a decrease of the g factor. Because of charge transfer between the core and arms, we propose a plausible mechanism potentially responsible for the induced CD line shapes in terms of the excitonic states of Tps with two different crystal structures. We believe that chiral 3D nanomaterials with anisotropic morphologies could offer new opportunities for relevant applications.

Chiral carbon dots: synthesis, optical properties, and emerging applications

“…Strain and the subsequent change of the crystal structure of nanoparticles can also cause the appearance of the optical activity in non-chiral materials 99 . By means of colloidal chemistry, nanoparticles can be synthesized in different shapes ranging from spherical dots and elongated nanorods to nanoplatelets, nanoscrolls, nanoribbons, and tetrapods; some of these shapes cause intrinsic optical activity 18 , 100 , 101 . Another way to introduce chirality is functionalization of the nanoparticle’s surface with chiral ligands, which may result in hybridization of their energy levels and/or distortion of their surface.…”

“…Another way to introduce chirality is functionalization of the nanoparticle’s surface with chiral ligands, which may result in hybridization of their energy levels and/or distortion of their surface. Using this approach, plenty of chiral semiconductor nanoparticles have been reported, such as CdS 89 , CdSe 101 , 102 , and CdTe 103 – 105 quantum dots, perovskites nanocrystals 91 , and nano-sheets 106 . Moreover, it was shown that chiral quantum dots can also be synthesized without using chiral precursors or ligands, yet enantiomer nanoparticles could be separated 90 , which pointed out that their optical activity may originate from chiral defects at the particle’s surface.…”

Imprinting chirality in inorganic nanomaterials for optoelectronic and bio-applications: strategies, challenges, and opportunities

“…32,33 The nanoparticle surface can be modified with an intrinsic chiral ligand generally containing functional surface-active head groups such -NH 2 , -COOH, -SH, N 3 , etc., which would allow the further attachment of any desired moiety around the NP's surface. [34][35][36][37][38][39][40] In general, the choice of functionalizing reagents depends very much on the nature of the nanoparticles; for example, thiol derivatives for gold and silver nanoparticles, carboxylic or phosphoric derivatives for metal oxides, and silane-based compounds for silica nanoparticles. This approach has been widely used in the field of biosensing and imaging and has been reviewed elsewhere.…”

Authentic Intelligent Machine for Scaling Driven Discovery: A Case for Chiral Quantum Dots

“…As an ever-evolving area, the study of chiral quantum dots (QDs) is attracting substantial attention due to their huge potential in the applications of stereosensing, − catalysis, , circularly polarized light emitters, − and more recently spintronics − and biological administrations. ,, Fundamentally, chiral QDs can be divided into several species involving (1) intrinsic chiral crystals and lattice or defects, − (2) chiral ligand-induced chiral optical activity transmissions, − and (3) chiral assemblies and shapes of achiral QDs. ,− A body of extensive reviews has well-summarized the recent progress of these nanomaterials. − Moreover, to physically understand the chiral origins, exciton–exciton (including ligand–core and particle–particle) interactions, and theories of dislocations and lattice growth mechanisms, together with advanced simulation techniques such as coupled dipole method (CDM), , density functional theory (DFT), ,,, and nondegenerate coupled-oscillator (NDCO) are widely employed/combined to unveil the chiral origins and obtain CD line shapes in the past decades …”