Binary nanocrystal superlattice membranes self-assembled at the liquid–air interface

Abstract

The spontaneous organization of multicomponent micrometre-sized colloids or nanocrystals into superlattices is of scientific importance for understanding the assembly process on the nanometre scale and is of great interest for bottom-up fabrication of functional devices. In particular, co-assembly of two types of nanocrystal into binary nanocrystal superlattices (BNSLs) has recently attracted significant attention, as this provides a low-cost, programmable way to design metamaterials with precisely controlled properties that arise from the organization and interactions of the constituent nanocrystal components. Although challenging, the ability to grow and manipulate large-scale BNSLs is critical for extensive exploration of this new class of material. Here we report a general method of growing centimetre-scale, uniform membranes of BNSLs that can readily be transferred to arbitrary substrates. Our method is based on the liquid-air interfacial assembly of multicomponent nanocrystals and circumvents the limitations associated with the current assembly strategies, allowing integration of BNSLs on any substrate for the fabrication of nanocrystal-based devices. We demonstrate the construction of magnetoresistive devices by incorporating large-area (1.5 mm x 2.5 mm) BNSL membranes; their magnetotransport measurements clearly show that device magnetoresistance is dependent on the structure (stoichiometry) of the BNSLs. The ability to transfer BNSLs also allows the construction of free-standing membranes and other complex architectures that have not been accessible previously.

A colloidoscope of colloid-based porous materials and their uses

“…With the focus on the assembly of simple, spherical particles, this review does not cover the synthesis and self-assembly of more complex colloidal building blocks, such as Janus particles, 34,35 patchy particles, [36][37][38][39] core-shell particles, [40][41][42] particles with more complex internal structures, [43][44][45] anisotropic particles, 46 or non-spherical nanocrystals. [47][48][49][50] Complex properties and highly functional materials can emerge solely by controlling the structure of the material or by providing a template to generate patterns in another material. The classical structures created by spherical assemblies are direct opals, consisting of threedimensional assemblies of colloidal particles in the ordered arrangement of a face centered cubic crystal ( Figure 3A), and their inverse analogues created by backfilling the interstitial sites with a second material and subsequent removal of the colloids which serve as templates to generate an interconnected, porous matrix ( Figure 3C).…”

Nanoparticle Superlattices: The Roles of Soft Ligands

“…Reproduced with permission 10, 11, 12, 18, 20, 21, 79, 120, 133, 135, 138, 144, 171, 172, 173, 174, 175, 176, 177. Copyright 1998, 2001, 2006, 2007, 2009, 2010, 2011, 2013, Nature Publishing Group.…”

Interfacial liquid-state surface-enhanced Raman spectroscopy

“…O riented assemblies of functional colloidal nanoparticles [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are important for both fundamental science and technological applications. Such assemblies have been realized on two-dimensional (2D) solid substrates by utilizing evaporation-based convection 6,7 , capillary interaction 8 , electric fields 9,10 , substrate templating 11,12 and surface tailoring of nanoparticles 13,14 .…”