Bio-based Nanocomposites Prepared by In-situ Polymerization of Furfuryl Alcohol with Cellulose Whiskers and Montmorillonite Clay Effect of MMT catalyst on resinification of FA 50 100 150 200 250
Two-dimensional (2D) photonic crystal (PC) slabs have attracted much research interest due to the relative ease of achieving a full photonic bandgap. [1,2] A wide variety of applications in optoelectronics have been explored using 2D PCs, such as waveguides, [3] superprisms, [4] laser diodes, [5] and photonic integrated circuits. [6] Traditionally, 2D PCs are fabricated by electron-beam lithography, which is a top±down process that is expensive and limited to relatively small areas; [7] these factors possibly hinder the application and commercialization of 2D PCs. A combination of top±down and bottom± up processes has been attempted, in which a 2D pattern is created by lithography followed by a self-assembly process to achieve the final structure.[8] Recently, by using monolayer self-assembly (MSA) of polystyrene (PS) submicrometer spheres to define a pattern, a catalyst-controlled selective growth technique has been applied to make 2D periodic arrays, such as hexagonal-patterned carbon nanotubes [9] and ZnO nanorods. [10] This is a simple and cost-effective approach for growing quasi-one-dimensional (quasi-1D) nanostructure arrays on a relatively large scale. However, these as-synthesized 1D nanostructures have a large percentage of air space and a vanishing photonic bandgap, and are not suitable for photonic applications. We present here a bottom±up process for fabricating 2D PC slabs starting with patterned ZnO nanorod arrays that were conformally coated with TiO 2 by template-assisted atomic layer deposition (ALD), a powerful technique for fabricating a variety of nanostructures, such as inverse opals, [11,12] one-dimensional nanostructures, [13] and nanobowl arrays. [14] The space between the ZnO nanorods was partially filled with TiO 2 , thus forming a continuous ZnO/ TiO 2 matrix with a highly ordered air-hole array. This periodic structure showed a reflection peak at the theoretically predicted bandgap region, while the near-UV emission of ZnO was unaffected by the TiO 2 coating. This technique demonstrates an effective and economical bottom±up process for 2D PC fabrication. Our objective was to make a photonic crystal with high refractive-index contrast, which was achieved by a two-step process: growth of patterned nanorod arrays with large air holes, then infiltration of the nanorod arrays with TiO 2 to form an air/TiO 2 /nanorod photonic crystal. In the first step, a continuous hexagonal gold nanoparticle pattern was formed on a sapphire substrate. The aligned ZnO nanorods were then grown using the gold pattern as a catalyst in a tube furnace at elevated temperature.[10] A honeycomb-like pattern of dense and well-aligned ZnO nanorod arrays was produced, as shown by the scanning electron microscopy (SEM) image in Figure 1a. The diameter and length of the ZnO nanorods were controlled by the thickness of the gold catalyst layer and the growth time. For a growth time of 15 min, the length of the ZnO nanorods was~500 nm and their diameters ranged from 20±30 nm.
This paper describes competitive self-assembly from solutions of symmetric alpha,omega-difunctional molecules on Cu substrates briefly exposed (less than 5 min) to ambient conditions. XPS and PM-IRRAS were utilized as complimentary surface analytical techniques to characterize the resulting organized organic thin films (OOTFs) on these "ambient" Cu surfaces. The order of preferential adsorption was observed to be diisocyanide approximately = dithiol > dicarboxylic acid > dinitrile > diisothiocyanate, indicating that the isocyanide (-NC), and thiol (-SH) functions provide the strongest adhesion to ambient Cu. 1,4-Phenylene diisocyanide and 1,4-terephthalic acid were both observed to adopt a standing-up phase configuration, in which the difunctional molecules bond to the base substrate through only one terminal functional group, with the other terminal group disposed away from the substrate. This indicates the ability to utilize OOTFs to produce "sticky surfaces" on ambient Cu. All other molecules bonded to the substrate through both terminal groups, in either surface-parallel or arched "hairpin" configurations. On the basis of these findings, aromatic diisocyanides and diacids are the most suitable molecules for creating OOTFs with high packing density. Such films can be utilized as protective coatings in the assembly of printed circuit boards, where Cu is becoming an increasingly important substrate for interconnects. Moreover, the ability to create chemically sticky surfaces on ambient Cu substrates indicates exciting potential for the development of a new surface-mount technology operative at the nanometer scale.
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