Mirrorless Lasing from Mesostructured Waveguides Patterned by Soft Lithography

Yang, Peidong; Wirnsberger, Gernot; Huang, Howard; Cordero, Steven R.; McGehee, Michael D.; Scott, Brian J.; Deng, Tao; Whitesides, George M.; Chmelka, Bradley F.; Buratto, Steven K.; Stucky, Galen D.

doi:10.1126/science.287.5452.465

Cited by 500 publications

(359 citation statements)

References 27 publications

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“…One can thus conclude that the QDs are spatially isolated from each other inside the beads, similar to that of organic dyes dispersed in mesoporous silica. [24][25][26] By using two independent measures (single-dot spectroscopy and bulk concentration measurement) reported previously, 21 we estimate that the numbers of quantum dots per bead are as large as 2 million (depending on the pore size), corresponding to ca. 5% surface coverage or occupancy rate.…”

Section: Resultsmentioning

confidence: 99%

Doping Mesoporous Materials with Multicolor Quantum Dots

2003

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Rapid and precise doping of mesoporous silica beads has been achieved with luminescent quantum dots, leading to 1-2 orders of magnitude improvements over the results previously achieved with polystyrene latex beads. A surprising finding is that multivalent hydrophobic interactions provide a strong driving force for efficient partitioning and immobilization of surfactant-coated quantum dots in the silica nanopores. The results indicate that the doping levels are so quantitative and precise that at least 30 ratios are distinguishable with two colors of quantum dots and that over 1000 ratios are possible with only three colors. By integrating mesoporous structures and quantum-confined particles, this work opens new possibilities in developing encoded or "smart" nanocomposite materials for multiplexed bioassay, high-throughput screening, and military security applications.

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Section: Resultsmentioning

confidence: 99%

Doping Mesoporous Materials with Multicolor Quantum Dots

2003

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“…Here, we demonstrate molding of solgel precursors to make nanostructured metal oxide films, whose features are 1 order of magnitude smaller than those previously demonstrated for sol-gel molding. 15,17 We show that embossing with a hard polymer mold can be an attractive alternative to pattern nanoporous films in a relatively simple process (Figure 1). Specifically, we nanostructure titania (TiO 2 ) films from sol-gel precursors to resemble the structure of an anodic alumina (AAO) template with pore diameters of 35-65 nm.…”

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confidence: 99%

Nanostructuring Titania by Embossing with Polymer Molds Made from Anodic Alumina Templates

2005

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We demonstrate a method for embossing titania sol−gel precursor with poly(methyl methacrylate) (PMMA) molds to make thin films of titania that have dense arrays of 35−65 nm diameter pores, whose features are 1 order of magnitude smaller than those previously demonstrated for sol−gel molding. We show that the high modulus of PMMA is necessary to preserve small features with high aspect ratios on the mold for nanopatterning. The molds are prepared by thermally infiltrating PMMA into anodic alumina templates, whose pore dimensions and depths are adjustable by varying anodization conditions. The difficulties associated with mold release from a master are avoided by wet etching the template. These titania films, and others made with other semiconductors, could be useful for photovoltaic, photocatalytic, and sensing applications where nanostructuring of surfaces with controlled dimensions are essential.Nanostructured semiconductor materials have drawn a lot of attention because they exhibit interesting optical, electronic, and catalytic properties. Semiconductor films with a dense array of pores at the 10-50 nm length scale are attractive for photovoltaics, 1-4 photocatalytics, 5,6 and sensing applications. 7 For these applications, it is desirable to pattern semiconductors in a relatively simple and cheap process. Although soft lithography 8 and nanoimprint lithography 9 are promising ways to nanopattern materials, they both have limitations and may not be suitable for patterning certain materials and specifications. Soft lithography, which usually utilizes elastomer poly(dimethylsiloxane) (PDMS) molds, has been extensively used to pattern photoresists, biological macromolecules, and semiconducting polymers. 8,10 The resolution achievable with PDMS however has often been limited to >100 nm due to its relatively low compression modulus of ∼2 MPa. 11 The use of a harder version of PDMS (h-PDMS) with a compression modulus of ∼9 MPa has increased the resolution to about 50 nm, 11,12 but only for features that are not densely spaced together and of high aspect ratio. This points to the need for an even harder mold as patterning is pushed toward increasingly smaller scale. Nanoimprint lithography, which has formidable resolution approaching 5 nm, 13 uses a hard Si or SiO 2 mold to achieve high aspect ratio features. Nanoimprinted materials include photoresists, polymers, silicon, and sol-gel materials, 9,14-16 but some other materials cannot be patterned by nanoimprint lithography because the mold adheres to the film and cannot be removed. For instance, nanostructuring of sol-gel inorganics potentially useful in many low cost applications can be very challenging with either soft lithography or nanoimprint lithography. Here, we demonstrate molding of solgel precursors to make nanostructured metal oxide films, whose features are 1 order of magnitude smaller than those previously demonstrated for sol-gel molding. 15,17 We show that embossing with a hard polymer mold can be an attractive alternative to pattern nanoporo...

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“…3,4 The properties of these solids depend on their compositions, structures, and dynamics, often across several length scales, which are challenging to characterize, understand, and control. 5,6 Solid-state nuclear magnetic resonance (NMR) spectroscopy plays a crucial role in the characterization of these materials at a molecular level, complementing other methods, such as X-ray diffraction, electron microscopy, and bulk property measurements (see ref 7 for a recent review).…”

Section: Introductionmentioning

confidence: 99%