Hollow spheres with tailored shell structures and large internal voids are attractive materials as high-performance catalyst supports, biomaterials, photonic-band-gap materials, thermal and acoustical insulation materials, and electrode materials. Various types of hollow spheres with different compositions, such as polymer, silica, carbon, metal, or metal oxide, can be synthesized by a number of methods, using vesicles, emulsions, spray-drying, hydrothermal reduction, layer-by-layer assembly, and hard templating methods. [1] Among such systems, hollow carbon spheres (HCS), especially those with graphitic shells, are very attractive owing to their special properties, that is, good electrical conductivity, outstanding thermal stability, and satisfactory oxidation resistance at moderate temperature.Most pathways for the production of HCS rely on hard templating [2][3][4] or hydrothermal reduction. [5][6][7][8] The obtained hollow spheres usually have diameters around 200-500 nm. HCS with uniform diameter can be prepared by a hard templating method, but it is difficult to obtain graphitized shells. To prepare hollow graphitic spheres (HGS), hydrothermal reduction is one option. [5,6] However, the reaction is not easily controlled, and highly nonuniform hollow spheres result. Alternatively, HGS can be prepared through thermal pyrolysis with the aid of transition-metal species [9,10] or by a microemulsion pathway.[11] The resulting HGS usually have diameters less than 150 nm, the shapes are not perfectly spherical, and the yields are quite low. These detractors severely limit their practical applications. Hence, it remains a great challenge to develop an easy approach for the preparation of HGS, especially micrometer-sized HGS, which could be interesting as reactors for three-phase (solid, liquid, and gas) reactions owing to their large central void. To our knowledge, such HGS have not been reported to date.Herein, we demonstrate a new approach for a synthesis that can be adjusted to deliver either micrometer-sized hollow polymer, carbon, or graphitized spheres. Micrometer-sized solid polymer spheres (PS) are prepared in an alcoholic solution (see the Experimental Section) and are then hollowed out to form hollow polymer spheres (HPS) by a surprisingly simple water washing step. The HPS can be easily converted into HCS by mild pyrolysis. In the presence of a graphitization catalyst, graphitized shells are accessible. The synthesis is easily scalable to obtain large quantities of product with high purity.The PS were prepared by the polymerization of 2,4-dihydroxybenzoic acid (DA) and formaldehyde in the presence of lysine. The non-ionic surfactant F127 is used as an additive to achieve a homogeneous, spherical product. [12] Figure 1 a shows an SEM image of the obtained polymer spheres with a relatively uniform size of (1.3 AE 0.1) mm. Figure 1 b, which displays a typical large-scale TEM image, reveals that these polymer spheres are essentially solid. If the center were hollow or would contain alcohol, it would be pos...

Silica and silicates are abundant in the crust and the mantle of the earth. They are also indispensable in many fields of science and technology, such as cement, ceramics, glass, zeolites, and catalysts. The aqueous chemistry of silicates has thus been intensively studied in the past by different methods.[1] While the introduction of 29 Si NMR methods [2,3] allowed detailed insight into silicate speciation, dynamical information on various solution species [4] is still limited to small oligomers and short time domains.[2] Interconversion mechanisms of larger silicate oligomers remain largely unexplored. Larger oligomers have repeatedly been discussed as building blocks for zeolite formation, [5] but these suggestions have remained highly disputed. [6] In order to study the interconversion process between oligomers, we have used electrospray ionization mass spectrometry (ESI-MS) in connection with isotopically labeled silicates. For aqueous silicate solutions as studied here, as well as for organic silsesquioxane solutions, ESI-MS has proved to be a very versatile technique. [7] We have focused on two cagelike species: the octamer is known to be a very stable species in the presence of tetramethylammonium (TMA + ) [8] and the hexamer in the presence of tetraethylammonium (TEA + ). [9,10] To study the stability of these species and elucidate the interconversion mechanisms, kinetic experiments with isotopically labeled solutions were carried out. Naturally occurring silicon consists of three isotopes:28 Si (92.2 %), 29 Si (4.7 %), and 30 Si (3.1 %). A solution containing the cubic octamer as the major species was prepared by dissolution of SiO 2 in an aqueous solution (1 SiO 2 /1.1 TMAOH/54 H 2 O) for 24 h at 77 8C and aging at room temperature for 24 h, which leads to a stable system in which 55 % of all silicon atoms are present in the cubic octamer ( 29 Si NMR analysis). A solution containing the prismatic hexamer was obtained by using TEA hydroxide under the same conditions. For both species a second, identical solution, but made from 29 Si-enriched silica (96.7 % 29 Si, Euriso Top, France) was prepared in parallel.For mass spectrometric analysis, a previously described setup was used.[11] The individual solutions showed the same mass spectra, the only difference being that the main signals were shifted to higher mass due to the heavier silicon isotope. A superposition of the spectra of the octamer solutions containing the 28 Si and 29 Si silicate species in one plot is shown in Figure 1 a to provide a reference point. The intensities at masses other than m/z 551 or 559 are due to the small amounts of the other isotopes present in the respective starting solutions.After the two solutions were combined, exchange of the 29 Si atoms between the silicate oligomers was observed, until the statistically expected distribution was reached. Figure 1 be shows the temporal evolution of a series of mass spectra in the m/z range of the cubic octamer after combination of the silicate solutions at 35 8C. Starting from a bim...

Building blocks in solution: Characteristic structural elements of the germanium‐containing zeolites ZSM‐5, polymorph C of zeolite Beta, and zeolite A (see picture) are identified in solution immediately before nucleation. The conditions of the reaction direct the polycondensation of silicate towards specific structures at the solution stage.