Deformable, spherical aggregates of metal nanoparticles connected by long-chain dithiol ligands self-assemble into nanostructured materials of macroscopic dimensions. These materials are plastic and moldable against arbitrarily shaped masters and can be thermally hardened into polycrystalline metal structures of controllable porosity. In addition, in both plastic and hardened states, the assemblies are electrically conductive and exhibit Ohmic characteristics down to approximately 20 volts per meter. The self-assembly method leading to such materials is applicable both to pure metals and to bimetallic structures of various elemental compositions.

Low-polydispersity copper nanoparticles (NPs) and nanorods (NRs) were synthesized by thermal decomposition of copper(II) acetylacetonate precursors in the presence of surfactants. Exchange of weakly bound alkylamine ligands for alkanethiols increased the stability of the NPs and, depending on the thiols’ terminal functionality, rendered them soluble in organic solvents or in water. The water-soluble nanoparticles stabilized with positively charged thiols exhibited long-term (months) stability and antifungal properties. The NPs and NRs stabilized with weakly bound alkylamine ligands are catalytically active in alkyne coupling reactions.

Supraspheres (SS) composed of hundreds to thousands of metal nanoparticles (NPs) and crosslinked by dithiol linkers are assembled into larger structures, which are subsequently converted into nanoporous metals (NMs). Conversion is achieved by heating which removes organic molecules stabilizing the NPs and allows for NP fusion. Heating of SS solutions leads to NMs of overall macroscopic dimensions; localized radiation using collimated electron beam is used to prepare metallized surface micropatterns. Depending on the composition of supraspherical precursors, nanoporous materials composed of up to three metals can be obtained. Strategies for controlling pore size and nanoscale surface roughness of these materials are discussed.

A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na–birnessite is an easily prepared manganese oxide with a 7 Å interlayer spacing and Na+ cations and water in the interstitial region. The material is readily characterized by powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, elemental analysis, and Mn oxidation state determination. It also undergoes facile ion exchange with Mg2+ to yield Mg–buserite, an analogous manganese oxide with a 9.6 Å interlayer spacing. Diffraction patterns and physical morphology can be related to the layered structure of the material. A thorough compositional analysis can also be done, which includes determination of mixed valency and interstitial hydration.

High quality manganese oxide thin films with smooth surfaces and even thicknesses have been prepared with a nonaqueous sol-gel process involving reduction of tetraethylammonium permanganate in methanol. Spin-coated films have been cast onto soft glass, quartz, and Ni foil substrates, with two coats being applied for optimum crystallization. The addition of alkali metal cations as dopants results in exclusive formation of the layered birnessite phase. By contrast, analogous reactions in bulk solgel reactions yield birnessite, tunneled, and spinel phases depending on the dopant cation.XRD patterns confirm the formation of well-crystallized birnessite. SEM images of Li-, Na-, and K-birnessite reveal extremely smooth films having uniform thickness of less than 0.5 µm. Thin films of Rb-and Cs-birnessite have more fractured and uneven surfaces as a result of some precipitation during the sol-gel transformation. All films consist of densely packed particles of about 0.1 µm. When tetrabutylammonium permanganate is used instead of tetraethylammonium permanganate, the sol-gel reaction yields amorphous manganese oxide as the result of diluted Mn sites in the xerogel film.Bilayer films have been prepared by casting an overcoat of K-birnessite onto a Na-2 birnessite film. However, Auger depth profiling indicates considerable mixing between the adjacent layers.