Aerogels are fine inorganic superstructures with enormously high porosity and are known to be exceptional materials with a variety of applications, for example in the area of catalysis. [1] The chemistry of the aerogel synthesis originated from the pioneering work [2] from the early 1930s and was further developed starting from the 1960s. [1,3] Attractive catalytic, thermoresistant, piezoelectric, antiseptic, and many other properties of the aerogels originate from the unique combination of the specific properties of nanomaterials magnified by macroscale self-assembly. Currently, the most investigated materials that form fine aerogel superstructures are silica and other metal oxides together with their mixtures. Recently, the possibility of creating aerogels and even light-emitting monoliths with densities 500 times less than their bulk counterparts from colloidal quantum dots and clusters of metal chalcogenides has attracted attention. These developments may open opportunities in areas such as semiconductor technology, photocatalysis, optoelectronics, and photonics. [4][5][6][7][8][9][10][11][12][13] Quite a number of different approaches have focused on modifying oxide-based aerogels (silica, titania, alumina, etc.) with metal nanoparticles (such as of platinum) to carry the catalytic properties from the metal [14,15] into the porous structures of the aerogels. [1,16,17] Fine mesoporous assemblies of catalytically active metal nanoparticles were also created by using artificial opals [18] and fungi [19] as templates. Other superstructural materials derived from metal nanoparticles include mesoporous platinum-carbon composites, [20] gold nanoparticles interlinked with dithiols, [21] necklace nanochains of hybrid palladium-lipid nanospheres, [22] electrocatalytically active nanoporous platinum aggregates, [23] foams, [24] and highly ordered two-and three-dimensional supercrystals. [25][26][27][28][29] The creation of non-supported metal aerogels has however not been reported to date. Recently, the formation of highly porous spherical aggregates ("supraspheres") of several hundred nanometers in diameter, where nanoparticles from one or two different metals were cross-linked with dithiols, was reported. [30,31] The metal aerogels presented herein exhibit an average density two orders of magnitude lower than that of the reported foams.[32] Their primary structural units match the size range of single nanoparticles (5-20 nm), which is an order of magnitude smaller than that of the self-assembled supraspheres.[31] Moreover, in the present case, no chemical cross-linkers are involved in the self-assembly process. The formation of such noble-metal nanoparticle-based mesoporous monometallic and bimetallic aerogels is an important step towards self-supported monoliths with enormously high catalytically active surfaces. Considering that metal nanoparticles possess very specific optical properties owing to their pronounced surface plasmon resonance, aerogels from metal nanoparticles may also find future applications in nano...

A convenient route at ambient conditions was employed to prepare narrow-dispersed ZnO nanorods in terms of size and morphology. Transmission electron microscopy and X-ray diffraction were used to characterize the structurally uniform and well-proportioned products. The as-prepared specimen exhibits strong ultraviolet exciton emission at 385 nm and disappearance of visible defect emission.

We present a facile and reproducible method for synthesizing monodisperse platinum (Pt) spheres with sizes ranging from 10 to 100 nm in diameter and exceptionally small standard deviations of 3% for large spheres. The reaction takes place in aqueous solution using a multistep seed-mediated approach. The Pt nanospheres consist of several small crystallites resulting in a surface roughness of 5-10 nm. Extinction spectra are measured from particles dispersed in water and calculated for single particles which are found to be in excellent agreement. We obtain a linear correlation between the plasmon extinction maximum (from UV to the visible regions) and the particle diameter which might be of value for experimentalists in the field.