Synthesis, self-assembly, disassembly, and reassembly of two types of Cu2O nanocrystals unifaceted with {001} or {110} planes.
In this work, we describe a solution-based synthesis of monodisperse Cu(2)O nanocrystals with controllable sizes in the nanoscale regime. Two types of nanocrystals, cubes and rhombic dodecahedra unifaceted with either {001} or {110} crystal planes, have been prepared at a 100% morphological yield. In particular, synthetic parameters and formation processes of the Cu(2)O nanocrystals have been investigated in detail, and a range of well-oriented supercrystals/superlattices built from the two types of nanobuilding blocks have been attained for the first time. It has been revealed that n-hexadecylamine used in the present work plays multiple roles: it serves as a chelating ligand to form [Cu(NH(2)C(16)H(33))(4)](2+) complex precursor, as a phase-transferring agent to transfer divalent Cu(2+) ions into the organic phase, as a reducing agent to generate monovalent Cu(+) (i.e., Cu(2)O), as a passivating adsorbate to control crystal morphology, and as a surface capping agent to generate self-assemblies of nanocrystals via van der Waals interaction. Apart from synthesis and self-assembly, disassembly and reassembly of Cu(2)O nanocrystals have also been investigated. The disassembly processes are accompanied with aggregative growths of nanocrystals, which can be attributed to a combined process of "oriented attachment" and Ostwald ripening, leading to permanent engagement and enlargement of nanocrystals. Finally, our self-assembled nanocrystals of Cu(2)O show a lower detection limit, lower operating temperature, and higher sensitivity in ethanol vapor detection, compared with other Cu(2)O-based alcohol sensors reported in the recent literature. A greater depletion layer of carrier and a relatively small contact potential may account for the observed sensing enhancement in the sensors made from the organized Cu(2)O nanocrystals.
Yao
Ke Xin
KX
Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, and Minerals, Metals, and Materials Technology Center, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
Yin
Xiao Ming
XM
Wang
Tai Hong
TH
Zeng
Hua Chun
HC
D003300:Copper / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods*
D003300:Copper; C000520:cuprous oxide