Publications

We report a simple, rapid approach to synthesize water-soluble and biocompatible fluorescent quantum dot (QD) micelles by encapsulation of monodisperse, hydrophobic QDs within surfactant/lipid micelles. Analyses of UV-vis and photo luminescence spectra, along with transmission electron microscopy, indicate that the water-soluble semiconductor QD micelles are monodisperse and retain the optical properties of the original hydrophobic QDs. The QD micelles were shown to be biocompatible and exhibited little or no aggregation when taken up by cultured rat hippocampal neurons. © 2005 American Chemical Society.

Abstract not provided.

Gold nanocrystal(NC)/silica films are synthesized through self-assembly of water-soluble gold nanocrystal micelles and silica by sol-gel processing. Absorption and transmission spectra show a strong surface plasmon resonance absorption peak at {approx}520 nm. Angular excitation spectra of surface plasmon show a steep dip in the reflectivity curve at {approx}65{sup o} depending on the thickness and refractive index of the gold NC/silica film. A potential SPR sensor with enhanced sensitivities can be realized based on these gold NC/silica films.

We report the synthesis of a new nanocrystal (NC) mesophase through self-assembly of water-soluble NC micelles with soluble silica. The mesophase comprises gold nanocrystals arranged within a silica matrix in a face-centered cubic lattice with cell dimensions that are adjustable through control of the nanocrystal diameter and/or the alkane chain lengths of the primary alkanethiol stabilizing ligands or the surrounding secondary surfactants. Under kinetically controlled silica polymerization conditions, evaporation drives self-assembly of NC micelles into ordered NC/silica thin-film mesophases during spin coating. The intermediate NC micelles are water soluble and of interest for biolabeling. Initial experiments on a metal-insulator-metal capacitor fabricated with an ordered three-dimensional gold nanocrystal/silica array as the "insulator" demonstrated collective Coulomb blockade behavior below 100 kelvin and established the current-voltage scaling relationship for a well-defined three-dimensional array of Coulomb islands.

Abstract not provided.

Recently so-called soft lithography approaches [Angew. Chem. Int. Ed. 37 (1998) 550] have been combined with surfactant [Adv. Mater. 9 (1997) 811. Nature 390 (1997) 674] and particulate [Science 282 (1998) 2244] templating procedures to create oxides with multiple levels of structural order. But the materials thus formed have been limited primarily to oxides with no specific functionality, and the associated processing times have ranged from hours to days. Using self-assembling inks we have combined evaporation-induced (silica/surfactant) self-assembly [Adv. Mater. 11 (1999) 579] with rapid prototyping techniques like micro-pen lithography [Science 283 (1999) 661. Mat. Res. Soc. Symp. Proc. 542 (1999) 159], ink-jet printing [Adv. Mater. 11 (1999) 734, Mat. Sci. Eng. C5 (1998) 289], and dip coating on micro-contact printed substrates to form hierarchically organized structures in seconds. By co-condensation of tetrafunctional silanes (Si(OR)4) with tri-functional organosilanes ((RO)3SiR') [Chem. Commun. (1999) 1367. Chem. Commun. (1997) 1769, J. Am. Chem. Soc. 119 (1997) 4090] or bridged silsesquioxanes (RO)3Si-R'-Si(OR)3) or by inclusion of organic additives, we have selectively derivatized the silica framework with functional R' ligands or molecules. The rapid-prototyping procedures we describe are simple, employ readily available equipment, and provide a link between computer-aided design and self-assembled functional nanostructures. We expect that the ability to form arbitrary functional designs on arbitrary surfaces will be of practical importance for directly writing sensor arrays and fluidic or photonic systems. © 2001 Elsevier Science B.V. All rights reserved.

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Abstract not provided.

Using a micro-Contact Printing ({mu}-CP) technique, substrates are prepared with patterns of hydrophilic, hydroxyl-terminated SAMS and hydrophobic methyl-terminated SAMS. Beginning with a homogeneous solution of silica, surfactant, ethanol, water, and functional silane, preferential ethanol evaporation during dip-coating, causes water enrichment and selective de-wetting of the hydrophobic SAMS. Correspondingly, film deposition occurs exclusively on the patterned hydrophilic SAMS. In addition, by co-condensation of tetrafunctional silanes (Si(OR){sub 4}) with tri-functional organosilanes ((RO){sub 3}Si(CH{sub 2}){sub 3}NH{sub 2}), the authors have selectively derived the silica framework with functional amine NH{sub 2} groups. A pH sensitive, micro-fluidic system was formed by further conjugation reactions with pH sensitive dye molecules.