Au-Assisted Growth of Anisotropic and Epitaxial CdSe Colloidal Nanocrystals via in Situ Dismantling of Quantum Dots

Abstract

Metallic nanocrystals have revealed in the last years as valuable materials for the catalytic growth of semiconductor nanowires. Yet, only low melting point metals like Bi have been reported to successfully assist the growth of elongated CdX (X = S, Se, Te) systems in solution, and the possibility to use plasmonic noble metals has become a challenging task. In this work we show that the growth of anisotropic CdSe nanostructures in solution can also be efficiently catalyzed by colloidal Au nanoparticles, following a preferential crystallographic alignment between the metallic and semiconductor domains. Noteworthy, we report the heterodox use of semiconductor quantum dots as an homogeneous and tunable source of reactive monomer species to the solution. The mechanistic studies reveal that the in-situ delivery of these cadmium and chalcogen monomer species and the formation of Au x Cd y alloy seeds are both key factors for the epitaxial growth of elongated CdSe domains. The implementation of this method suggests an alternative synthetic approach for the assembly of different semiconductor domains into more complex heterostructures.

Synthesis and Thermoelectric Properties of Noble Metal Ternary Chalcogenide Systems of Ag–Au–Se in the Forms of Alloyed Nanoparticles and Colloidal Nanoheterostructures

“…Besides controlling size and shape of NPs, it allows sequential deposition of several materials in the form of a single hybrid NP, it fully exploits unconventional reactivity of nanomaterials such as cation or anion exchange, and it stabilizes metastable phases. [14][15][16][17][18][19][20][21][22][23] Thus, the formation of heterostructures with appropriate interfaces and the fine control over their chemical composition are reasonable aspects to be achieved by means of colloidal chemistry, and definitely key factors for further developments. 16,24,25 Just as a tiny fraction of numerous examples, type II-semiconductor heterostructures such as CdSe@CdTe multibranched NPs, metal-semiconductor hybrid systems such as Au(Pt)-CdSe nanodumbbells or Au(Pt)-Cu 2 ZnSnS 4 NPs, bimetallic core@shell Co@Cu or FePd@Pd nanostructures and narrow band gap semiconductor core-shell PbTe@PbS NPs have shown to be efficient systems for optoelectronic, catalytic and thermoelectric applications.…”

“…At the interface between solid-state and molecular chemistries, modern colloidal synthesis appears to be unique in several regards. Besides controlling size and shape of NPs, it allows sequential deposition of several materials in the form of a single hybrid NP, it fully exploits unconventional reactivity of nanomaterials such as cation or anion exchange, and it stabilizes metastable phases. − Thus, the formation of heterostructures with appropriate interfaces and the fine control over their chemical composition are reasonable aspects to be achieved by means of colloidal chemistry and definitely key factors for further developments. ,, Just as a tiny fraction of numerous examples, type II-semiconductor heterostructures such as CdSe@CdTe multibranched NPs, metal–semiconductor hybrid systems such as Au­(Pt)-CdSe nanodumbbells or Au­(Pt)-Cu 2 ZnSnS 4 NPs, bimetallic core@shell Co@Cu or FePd@Pd nanostructures, and narrow band gap semiconductor core–shell PbTe@PbS NPs have shown to be efficient systems for optoelectronic, catalytic, and thermoelectric applications. − Furthermore, colloidal NPs can then be used as pre-engineered building blocks for constructing a nanostructured extended solid with virtually unlimited control over its compositional and morphological features. ,, The most straightforward advantage of this method resides in the fact that a subnanometer compositional control is achieved already in the building blocks before the formation of the final composite, which guarantees a high homogeneity in the latter. On the whole, colloidal synthesis routes and bottom-up assembly procedures allow simultaneous atomic- and nanoscale-control over chemical composition and morphology of inorganic NPs and derived nanocomposites, which open new avenues in optoelectronic and energy applications. − …”

Change in Rate of Catalytic Growths of Nanocrystals Catalyst for Formation of Asymmetric Multicomponent Heterostructures and Their Self-Assembly

“…Nanomaterials acting as catalyst for facilitating growths of other nanomaterials have opened up a new approach for architecting dual and triple material heterostructures. − Among these, silver chalcogenides remained in the forefront for solution processed growths of different groups II–VI semiconductor nanostructures. ,− These silver chalcogenides have unique characteristic which showed temperature dependent phase transitions from α to β form. ,− At higher temperature, the obtained cubic (or β) phase allows movements of Ag­(+) ions within the lattice, creating vacancies. This provided a new opportunity for insertion of other metal ions and facilitated superionic type catalytic growth leading to semiconductor–semiconductor heterostructures.…”

Insights into the Synthesis Mechanisms of Ag-Cu3P-GaP Multicomponent Nanoparticles

“…During the last decades, the metal-assisted growth of semiconductor nanostructures has developed as a promising tool enabling high control over crystal properties, including crystal structure, − composition, − growth direction, − morphology, ,, surface faceting, − doping profile, − and defect structure. − The seed material’s role was limited to the capability to nucleate and selectively grow the semiconductor nanocrystal. − Few reports considered the seed material as an active component of the synthesized nanostructure. − We propose that the metal-assisted growth approach is promising for synthesizing advanced multicomponent nanostructures. Therefore, a deeper understanding of the involved formation mechanisms is essential to exploit its full potential.…”