silicon and coumarin

Introduction of a heteroatom into a fluorophore was carried out for coumarin through a replacement of its bridging oxygen atom with a silicon atom. The maximum-emission wavelength of Si-coumarin (SiC B) bathochromically shifted from 426 nm in cyclohexane to 626 nm in water. The adipogenic differentiation processes in mesenchymal stem cells were monitored using SiC B.

Topics: Adipogenesis; Animals; Cell Line; Coumarins; Density Functional Theory; Hydrogen Bonding; Mesenchymal Stem Cells; Mice; Microscopy, Confocal; Silicon

Catalytic surfaces have been prepared by complexation of palladium on self-assembled terpyridine monolayers on silicon. A reaction-based fluorogenic probe was developed to allow facile visualization of the catalytic potential of the surface. Superior activity of the immobilized catalyst compared with the homogeneous control reactions is demonstrated.

Topics: Catalysis; Coordination Complexes; Coumarins; Molecular Structure; Palladium; Silicon

In the present paper, dsDNA separation has been studied in a silicon micropillar array column using ion-pair RP-HPLC (IP-RP-HPLC). The deep-etched (32.0 μm) silicon micropillar array was fabricated by advanced deep UV lithography and by a dedicated Bosch etch process and then sealed by anodic bonding to a Pyrex glass. The pillar surface was subsequently conditioned hydrophobic. Working in isocratic mode under nonretained conditions, van Deemter curves of dsDNA and coumarin were established to assess the performance of the micropillar array column, resulting in plate heights of only a few micrometers. Working in gradient mode, separations of dsDNA fragments were evaluated. The relevant gradient operation parameters were studied to understand their influence on dsDNA separations. The correlation between DNA length and retention was measured and theoretically described in a length range of 50-500 bp, promising for the determination of DNA of an unknown length. Finally, a separation example demonstrated the excellent separation power of on-chip IP-RP chromatography by achieving a large operation range of DNA length (10-300 bp) with a 5-bp difference among 11 dsDNA fragments.

Topics: Chromatography, High Pressure Liquid; Chromatography, Reverse-Phase; Coumarins; DNA; Microfluidic Analytical Techniques; Molecular Weight; Silicon

We report on the grafting of coumarin chromophores on flat silicon surfaces and in regions of nanometric dimensions drawn on silicon surfaces. The coumarin derivative was grafted by using the quaternization of a tertiary amine group of the chromophore with a ((chloromethyl)phenylethyl)-dimethylchlorosilane (CMPDCS) grafted on silicon. Complete characterization of the grafted layer was performed as a function of reaction time by X-ray photoelectron spectroscopy, X-ray reflectometry, atomic force microscopy, fluorescence spectroscopy and laser-scanning confocal microscopy. The results indicate that about one chromophore molecule is grafted every second CMPDCS molecule, resulting in a surface density of coumarin of slightly more than one coumarin per nm2. A broadening of the distribution of the fluorescence lifetimes was observed, suggesting that the grafted molecules experience a larger distribution of environments in the grafted layer than in solution. Since this reaction is fully compatible with silicon processing technology, the grafting could also be performed in nano-regions of size as small as 250 nm defined by combining electron-beam lithography with silanization. In such nano-sized regions the distribution of fluorescence lifetimes was narrower, suggesting a possible influence of the confinement on the organization of the molecules.

Topics: Coumarins; Microscopy, Atomic Force; Microscopy, Electron; Molecular Structure; Nanostructures; Silicon; Spectrum Analysis