Controlled assemblies from 0 to 3D of colloidal nanocrystals (NCs) have recently attracted growing interest as a result of their potentially novel electronic and optical properties, which might be different from those of a corresponding collection of non-coupled NCs or from the bulk.^1,3

One issue that has been mainly addressed in this field is the control of the interparticle distance in the assembly which allows the tuning of the properties of the NC superstructure. In our work different CdX materials (X stands for S^2-, Se^2- or Te^2-) of various sizes and shapes, synthesized by a seeded-growth approach,⁴  have been assembled giving rise to only inorganic NC-based superstructures with different branching degrees by easily processable solution-based reactions.

One general assembling strategy has been used for the organization of Type IV-VI semiconductor NCs independently of their nature. The aim of our work is the formation of an inorganic junction between NCs by means of a previous selective nucleation of gold dots (Au) on the tips of the semiconductor nanostructures. Trace amounts of iodine (I₂) were able to glue the Au domains that had nucleated at the tips of the NCs, as previously observed by Cheng et al.⁵when iodide was added to a colloidal Au solution.

In the solution the final size of the assembly can be controlled by the ratio between NCs and aggregator agent (I₂). The selective nucleation of Au domains in just one or both tips of the chalcogenide NCs introduces preferential anchoring points that allow tuning the assembling freedom degree of the heterostructures.

Semiconductor NCs are interesting candidates for electronic and photovoltaic devices.^{6, 7, 8} In addition, zero interparticle distances in the net are expected to improve optical and electronic properties of the assemblies with respect to those of individual NCs. In this sense, the use of continuous and solely inorganic-based semiconductor “polymers” could improve the performance of the final device.

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1. Synthesis, structural and magnetic properties of magnetic metal/semiconductor nanocrystals heterostructures
2. Reversibly UV-light-induced hydrophobic/oleofilic to amphiphilic surface transition in thin films of organic-capped TiO₂ nanorods
3. Topologically controlled growth of colloidal semiconductor/magnetic nanocrystal heterostructures: site-selective functionalization of TiO₂ nanorods with either γ-Fe₂O₃ or ε-Co spherical domains