Colloidal hybrid nanoparticles contain multiple nanoscale domains fused together by solid-state interfaces. They represent an emerging class of multifunctional lab-on-a-particle architectures that underpin future advances in solar energy conversion, fuel-cell catalysis, medical imaging and therapy, and electronics. The complexity of these 'artificial molecules' is limited ultimately by the lack of a mechanism-driven design framework. Here, we show that known chemical reactions can be applied in a predictable and stepwise manner to build complex hybrid nanoparticle architectures that include M-Pt-Fe(3)O(4) (M = Au, Ag, Ni, Pd) heterotrimers, M(x)S-Au-Pt-Fe(3)O(4) (M = Pb, Cu) heterotetramers and higher-order oligomers based on the heterotrimeric Au-Pt-Fe(3)O(4) building block. This synthetic framework conceptually mimics the total-synthesis approach used by chemists to construct complex organic molecules. The reaction toolkit applies solid-state nanoparticle analogues of chemoselective reactions, regiospecificity, coupling reactions and molecular substituent effects to the construction of exceptionally complex hybrid nanoparticle oligomers.

Nanoparticles of elemental germanium have interesting optical and electronic properties and relatively low toxicity, making them attractive materials for biological and optoelectronic applications. The most common routes to colloidal Ge nanoparticles include metathesis reactions involving Zintl salts, hydride reduction of Ge halides, and thermal decomposition of organogermane precursors. Here we describe an alternative “heat-up” method for the synthesis of size- and shape-tunable Ge nanoparticles that are both crystalline and air stable. The readily available reagents GeI4, oleylamine, oleic acid, and hexamethyldisilazane are combined in one pot and heated to 260 °C, where a rapid nucleation event occurs and multifaceted nanoparticles of crystalline Ge form. By varying the concentration of GeI4, the nanoparticle size can be tuned from 6 to 22 nm with narrow size distributions. Adding trioctylphosphine yields cube-shaped particles, and switching the solvent to octadecene yields one-dimensional nanostructures. The Ge nanoparticles, which are fully air stable for more than 6 months, were characterized by XRD, TEM, HRTEM, EDS, XPS, DRIFT, and UV−visible spectroscopy.

The reaction of colloidal AuCu nanoparticles with dissolved sul-fur and bubbling oxygen in oleyl-amine at 172 °C yields phase-segregated colloidal Au−Cu2S het-erodimers. This prototype system demonstrates an alternative route to colloidal hybrid nanoparticles, which applies element-selective chemical reactions to alloy nanoparticles with preprogrammed compositions.