Two-dimensional ordered arrays of gold (Au) nanoparticles were fabricated using two different variants of the nanosphere lithography technique. First, ordered arrays of polystyrene nanospheres on Si substrate were used as deposition masks through which gold films were deposited by electron beam evaporation. After the removal of the nanospheres, an array of triangular Au nanodisks was left on the Si substrate. After thermal annealing at increasing temperature, systematic shape transition of the nanostructures from original triangular Au nanodisks to rounded nanoparticles was observed. This approach allows us to systematically vary the size and morphology of the particles. In the second and novel technique, we made use of reactive ion etching to simultaneously reduce the dimension of the masking nanospheres and create arrays of nanopores on the substrate prior to the deposition of the Au films. These samples were subsequently annealed, which resulted in size-tunable and ordered Au nanoparticle arrays with the nanoparticles nested in the nanopores of the templated substrate. With the nanoparticles anchored in the nanopores, the substrate could be useful as a template for growth of other nanomaterials.

We report a simple technique for the fabrication of a two-dimensional periodic non-close-packed array of nonspherical particles. The technique exploits the self-assembly of uniformly sized colloidal microspheres on the surface of a Si substrate followed by reactive ion etching (RIE) that converts the spheres into nonspherical particles. Single and double layers of packed colloidal polystyrene microspheres of uniform size (diameter 1.2 μm) were spin-coated onto cleaned Si substrates. The samples were then exposed to reactive ions in an RIE unit operating under a mixture of CF4 and O2 gases. Due to preferential etching in the direction normal to the surface of the substrate, the microspheres were reduced to a nonspherical form resembling a biconvex microlens. Moreover, the periodic nature of the previously packed layer was preserved during the etching process. As a result, we obtained two-dimensional periodic non-close-packed arrays of nonspherical particles. In this work, we report the systematic dependence of the dimensions of the polystyrene particles on the duration of the exposure to RIE. In addition, the resultant patterned Si substrates were further utilized as templates for directed assembly of unique arrangements of microspheres with different diameters.

No abstract

No abstract

Synthesis and biological activity of fluorinated 7-aryl-2-pyridyl-6,7-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-amines [1] § A B S T R A C TIn our lead finding program, 12 new fluorinated 7-aryl-2-pyridyl-6,7-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-amines were prepared via a practical three-step procedure starting from (iso)nicotinic hydrazides. The fluorine substituted aryl fragment was introduced in the last step through cyclocondensation of N-(3-pyridyl-1,2,4-triazol-5-yl)guanidines and fluoro/trifluoromethyl substituted benzaldehydes. The structures of the compounds were confirmed by 1 H and 13 C NMR spectral data. The tautomeric preferences for the compounds were established using 2D NOESY experiments. The antiproliferative activity of the synthesized 1,2,4-triazolo[1,5-a][1,3,5]triazines was evaluated against breast, colon and lung cancer cell lines. The highest antiproliferative activity in the series was found for 2-(pyridine-3-yl)-7-(4-trifluoromethylphenyl)-6,7-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-amine. The lack of inhibitory activity against bovine dihydrofolate reductase (DHFR) indicated that the antiproliferative activity was realized via other mechanisms.ß 2008 Elsevier B.V. All rights reserved. § Part 10 in the series ''Fused heterocyclic systems with s-triazine ring''.