SummaryIn this article we present the development of a multibeam two-photon laser scanning microscope. A new type of beam splitter to create the multitude of laser beams is described. This type of beam splitter has higher transmission and generates more uniform beams than can be achieved with the microlens approach used by other groups. No crosstalk exists between the different foci due to small temporal delays between the individual beams. The importance of dispersion compensation to obtain maximum efficiency of the microscope is discussed. With optimum compensation the fluorescence signal was raised by a factor of 14. Different modes of detecting the fluorescence signals and their effect on imaging speed and resolution are discussed.

This manuscript describes the synthesis of poly(methacrylic acid) (PMAA) brushes via surfaceinitiated atom transfer radical polymerization (SI-ATRP) of sodium methacrylate (NaMA) and their use as substrates for the mineralization of calcium carbonate. A CuBr/CuBr 2 /bipyridine catalyst system in aqueous solution at room temperature allowed the synthesis of brushes with thicknesses of up to 300 nm. Using substrates modified with mixtures of an ATRP-initiator modified trimethoxysilane and an "inert" pivaloyl-modified trimethoxysilane to initiate the ATRP of NaMA, a series of brushes with varying chain density could be prepared. Subsequent mineralization experiments revealed that, while low-density brushes promoted the formation of calcite crystals, high-density brushes were covered with a thin layer of amorphous CaCO 3 (ACC). This is of interest because ACC can serve as a metastable precursor for different crystalline CaCO 3 polymorphs and offers attractive perspectives for the bottom-up fabrication of well-defined CaCO 3 crystal architectures.

How to get into films: Micropatterned poly(methacrylic acid) (PMAA) brushes are used as an ionotropic matrix for the fabrication of microstructured calcite thin films. The calcite films are an exact 3D replica of the PMAA brush matrix (see Scheme; ACC=amorphous CaCO3 phase).

A novel process, carbon dioxide induced gelation, opens new pathways towards hydrogels and can be coupled with supercritical drying to produce aerogels.

Thin tablets and films of calcium carbonate have been grown at the air-water interface via an amorphous precursor route using soluble process-directing agents and a Langmuir monolayer based on resorcarene. By using appropriate concentrations of poly(acrylic acid-sodium salt) in combination with Mg2+ ion, an initially amorphous film is deposited on the monolayer template, which subsequently crystallizes into a mosaic film composed of a mixture of single-crystalline and spherulitic patches of calcite and aragonite. Of particular importance is the synthesis of single-crystalline "tablets" of aragonite (approximately 600 nm thick), because this phase generally forms needle-like polycrystalline aggregates when grown in vitro. To our knowledge, a tabular single-crystalline morphology of aragonite has only been observed in the nacreous layer of mollusk shells. Therefore, this in vitro system may serve as a useful model for examining mechanistic issues pertinent to biomineralization, such as the influence of organic templates on nucleation from an amorphous phase.

No abstract

The highly charged amphiphilic dendron-calixarene (1) forms stable monolayers at the air-water interface. Crystallization of CaCO 3 beneath monolayers of 1 selectively leads to growth of the metastable polymorph vaterite at low surface pressure, in distinct contrast to the growth characteristics of calcite or aragonite crystals under less highly charged calixarene monolayers, as we have reported previously. This result lends further support to our hypothesis that surface charge density is the dominant factor governing heterogeneous nucleation of CaCO 3 crystals at the monolayer/solution interface.

No abstract